Edgar Filing: IDENIX PHARMACEUTICALS INC

e10vq

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

(Mark One)


þ		QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the Quarterly Period Ended September 30, 2005


o		TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from to

Commission file number 000-49839

Idenix Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)


Delaware (State or Other Jurisdiction of Incorporation or Organization)		45-0478605 (IRS Employer Identification No.)

60 Hampshire Street Cambridge, MA (Address of Principal Executive Offices)		02139 (Zip Code)

Registrant’s telephone number, including area code: (617) 995-9800

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports) and (2) has been subject to such filing requirements for the past 90 days. Yes þ No o

Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Exchange Act). Yes o No þ

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of The Exchange Act). Yes o No þ

As of October 31, 2005, the number of shares of the registrant’s common stock, par value $.001 per share, outstanding was 55,632,622 shares.


		Page
Part I—Financial Information

Item 1.	Financial Statements

	Unaudited Condensed Consolidated Balance Sheets at September 30, 2005 and December 31, 2004		3

	Unaudited Condensed Consolidated Statements of Operations for the Three Months ended September 30, 2005 and 2004		4

	Unaudited Condensed Consolidated Statements of Operations for the Nine Months ended September 30, 2005 and 2004		5

	Unaudited Condensed Consolidated Statements of Cash Flows for the Nine Months ended September 30, 2005 and 2004		6

	Notes to the Unaudited Condensed Consolidated Financial Statements		7

Item 2.	Management’s Discussion and Analysis of Financial Condition and Results of Operations		18

Item 3.	Quantitative and Qualitative Disclosures About Market Risk		47

Item 4.	Controls and Procedures		47

Part II—Other Information

Item 1.	Legal Proceedings		49

Item 2.	Unregistered Sales of Equity Securities and Use of Proceeds		49

Item 3.	Defaults upon Senior Securities		49

Item 4.	Submission of Matters to a Vote of Security Holders		49

Item 5.	Other Information		49

Item 6.	Exhibits		49

Signatures			50

Exhibit Index
EX-10.1 AGREEMENT DATED OCTOBER 24, 2005
EX-31.1 SECTION 302 CERTIFICATION OF CEO
EX-31.2 SECTION 302 CERTIFICATION OF CFO
EX-32.1 SECTION 906 CERTIFICATION OF CEO
EX-32.2 SECTION 906 CERTIFICATION OF CFO

IDENIX PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(IN THOUSANDS, EXCEPT SHARE DATA)

(UNAUDITED)


	September 30,			December 31,
	2005			2004
ASSETS
Current assets:
Cash and cash equivalents	$	41,807		$	42,083
Restricted cash		411			—
Marketable securities		61,042			38,429
Accounts receivable, related party		16,660			16,243
Prepaid expenses and other current assets		4,166			3,231

Total current assets		124,086			99,986
Property and equipment, net		9,793			6,805
Restricted cash		750			750
Marketable securities		12,001			76,754
Income taxes receivable		832			370
Investment		500			500
Other assets		2,642			1,953

Total assets	$	150,604		$	187,118


LIABILITIES AND STOCKHOLDERS’ EQUITY
Current liabilities:
Accounts payable	$	2,143		$	4,619
Accrued expenses		20,431			15,300
Deferred rent		192			50
Deferred revenue, related party		8,683			9,695
Income taxes payable		214			199

Total current liabilities		31,663			29,863
Long-term obligations		2,757			3,691
Deferred rent, net of current portion		1,908			1,455
Deferred revenue		4,272			4,272
Deferred revenue, related party, net of current portion		28,219			38,779

Total liabilities		68,819			78,060
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.001 par value; 60,000,000 shares authorized at September 30, 2005 and December 31, 2004; 48,300,792 and 47,857,887 shares issued and outstanding at September 30, 2005 and December 31, 2004, respectively		48			48
Additional paid-in capital		349,276			340,938
Deferred compensation		(763	)		(1,987	)
Accumulated other comprehensive (loss) income		(302	)		136
Accumulated deficit		(266,474	)		(230,077	)

Total stockholders’ equity		81,785			109,058

Total liabilities and stockholders’ equity	$	150,604		$	187,118

The accompanying notes are an integral part of these condensed consolidated financial statements.

IDENIX PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(IN THOUSANDS, EXCEPT PER SHARE DATA)

(UNAUDITED)


	Three Months Ended September 30,
	2005			2004
Revenues:
License fees and collaborative research and development — related party	$	15,506		$	17,052
Government research grants		124			127

Total revenues		15,630			17,179
Operating expenses (1):
Research and development		21,488			19,048
General and administrative		4,800			4,205
Sales and marketing		4,222			1,840

Total operating expenses		30,510			25,093

Loss from operations		(14,880	)		(7,914	)
Investment income, net		717			521
Other (expense) income		(2	)		1

Loss before income taxes		(14,165	)		(7,392	)
Income tax benefit		467			39


Net loss	$	(13,698	)	$	(7,353	)


Net loss per common share:
Basic	$	(0.28	)	$	(0.17	)
Diluted	$	(0.28	)	$	(0.17	)
Shares used in calculation of net loss per share common share:
Basic		48,220			44,520
Diluted		48,220			44,520


(1)		During the three months ended September 30, 2005 and 2004, stock-based compensation expenses included in operating expenses amounted to approximately:


	Three Months Ended September 30,
	2005		2004
Research and development	$	227	$	297
General and administrative		88		201
Sales and marketing		24		31

	$	339	$	529

The accompanying notes are an integral part of these condensed consolidated financial statements.

IDENIX PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(IN THOUSANDS, EXCEPT PER SHARE DATA)

(UNAUDITED)


	Nine Months Ended September 30,
	2005			2004
Revenues:
License fees and collaborative research and development — related party	$	46,315		$	76,371
Government research grants		300			259

Total revenues		46,615			76,630
Operating expenses (1):
Research and development		63,141			55,142
General and administrative		14,744			10,942
Sales and marketing		8,055			3,653

Total operating expenses		85,940			69,737

(Loss) income from operations		(39,325	)		6,893
Investment income, net		2,339			665
Other expense		(4	)		(1	)

(Loss) income before income taxes		(36,990	)		7,557
Income tax benefit		593			153

Net (loss) income	$	(36,397	)	$	7,710



Net (loss) income per common share:
Basic	$	(0.76	)	$	0.20
Diluted	$	(0.76	)	$	0.19
Shares used in calculation of net (loss) income per common share:
Basic		48,100			39,190
Diluted		48,100			41,361


(1)		During the nine months ended September 30, 2005 and 2004, stock-based compensation expenses included in operating expenses amounted to approximately:


	Nine Months Ended September 30,
	2005		2004
Research and development	$	744	$	915
General and administrative		475		580
Sales and marketing		87		97

	$	1,306	$	1,592

The accompanying notes are an integral part of these condensed consolidated financial statements.

IDENIX PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(IN THOUSANDS)

(UNAUDITED)


	Nine Months Ended September 30,
	2005			2004
Cash flows from operating activities:
Net (loss) income	$	(36,397	)	$	7,710
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:
Depreciation and amortization		1,500			889
Stock-based compensation expense		1,306			1,592
Gain on sale of marketable securities		(384	)		—
Revenue adjustment for contingently issuable shares		2,451			1,850
Changes in operating assets and liabilities:
Accounts receivable, related party		(417	)		(3,050	)
Prepaid expenses and other current assets		(1,004	)		12
Income taxes receivable		(462	)		—
Other assets		(694	)		155
Accounts payable		(2,387	)		(1,056	)
Accrued expenses		5,450			1,073
Deferred rent		594			(38	)
Deferred revenue		—			(35	)
Deferred revenue, related party		(7,276	)		(8,561	)
Income taxes payable		(77	)		(180	)
Long-term obligations		(899	)		(944	)

Net cash used in operating activities		(38,696	)		(583	)
Cash flows from investing activities:
Purchase of property and equipment		(4,716	)		(2,859	)
Restricted deposits		(411	)		20
Purchases of marketable securities		(18,010	)		(42,742	)
Proceeds from sales or maturities of marketable securities		60,560			—

Net cash provided by (used in) investing activities		37,423			(45,581	)
Cash flows from financing activities:
Net proceeds from sale of common stock in initial public offering and private placement		—			133,409
Proceeds from exercise of common stock options		1,257			870
Repayment of capital lease obligations		—			(2	)

Net cash provided by financing activities		1,257			134,277
Effect of changes in exchange rates on cash and cash equivalents		(260	)		(63	)

Net (decrease) increase in cash and cash equivalents		(276	)		88,050
Cash and cash equivalents at beginning of period		42,083			43,485

Cash and cash equivalents at end of period	$	41,807		$	131,535

Supplemental disclosure of cash flow information:
Taxes paid	$	28		$	178
Supplemental disclosure of noncash investing and financing activities:
Value of shares of common stock contingently issuable or issued to related party	$	6,747		$	7,359

The accompanying notes are an integral part of these condensed consolidated financial statements.

IDENIX PHARMACEUTICALS, INC.

NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(UNAUDITED)

1. DESCRIPTION OF BUSINESS

Idenix Pharmaceuticals, Inc. (together with its consolidated subsidiaries, the “Company”) is a biopharmaceutical company engaged in the discovery, development and commercialization of drugs for the treatment of human viral and other infectious diseases. The Company’s current focus is on diseases caused by hepatitis B virus (“HBV”), hepatitis C virus (“HCV”) and human immunodeficiency virus (“HIV”).

The Company is subject to risks common to companies in the biopharmaceutical industry including, but not limited to, the successful development and commercialization of products, clinical trial uncertainty, regulatory approval, fluctuations in operating results and financial risks, potential need for additional funding, protection of proprietary technology and patent risks, compliance with government regulations, dependence on key personnel and collaborative partners, competition, technological and medical risks and management of growth.

Effective May 8, 2003, Novartis Pharma AG (“Novartis”), a subsidiary of Novartis AG, acquired a majority interest in the Company’s outstanding capital stock and the operations of the Company have been consolidated in the financial statements of Novartis AG since that date. Novartis has the ability to exercise control over the Company’s strategic direction, research and development activities and other material business decisions (Note 4).

2. BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES

The accompanying condensed consolidated financial statements are unaudited and have been prepared by the Company in accordance with accounting principles generally accepted in the United States of America for interim reporting.

The consolidated financial statements reflect the operations of the Company and its wholly owned subsidiaries. All significant intercompany accounts and transactions have been eliminated.

Certain information and footnote disclosures normally included in the Company’s annual consolidated financial statements have been condensed or omitted. Certain prior year amounts have been reclassified to conform to current year presentation. The interim financial statements, in the opinion of management, reflect all adjustments (including normal recurring accruals) necessary for a fair statement of the financial position and results of operations for the interim periods presented.

The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for any future period or the fiscal year ending December 31, 2005. These interim financial statements should be read in conjunction with the audited financial statements for the year ended December 31, 2004, which are included in the Company’s Annual Report on Form 10-K, which was filed with the Securities and Exchange Commission (“SEC”) on March 17, 2005.

Revenue Recognition

The Company records revenue provided that there is persuasive evidence that an arrangement exists and service has been performed, the price is fixed or determinable and collectibility is reasonably assured. The Company earns revenue under collaborative research and development arrangements and government research grants.

IDENIX PHARMACEUTICALS, INC.
NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

Collaborative Research and Development Revenue — Revenue related to collaborative research and development arrangements includes nonrefundable license fees, milestones and research and development payments from the Company’s collaborative partners. Where the Company has continuing performance obligations under the terms of a collaborative arrangement, nonrefundable license fees are recognized as revenue over the specified development period as the Company completes its performance obligations. When the Company’s level of effort is relatively constant over the performance period, the revenue is recognized on a straight-line basis. The determination of the performance period involves judgment on the part of management. If the Company cannot reasonably estimate its costs, then it recognizes the license fee revenue on a straight-line basis over the performance period. Payments received from collaborative partners for research and development efforts by the Company are recognized as revenue over the contract term as the related costs are incurred, net of any amounts due to the collaborative partner for costs incurred during the period. Revenues from milestones related to an arrangement under which the Company has continuing performance obligations, if deemed substantive, are recognized as revenue upon achievement of the milestone. Milestones are considered substantive if all of the following conditions are met: the milestone is nonrefundable; achievement of the milestone was not reasonably assured at the inception of the arrangement; substantive effort is involved to achieve the milestone; and the amount of the milestone appears reasonable in relation to the effort expended, the other milestones in the arrangement and the related risk associated with the achievement of the milestone. If any of these conditions is not met, the milestone payment is deferred and recognized as revenue as the Company completes its performance obligations.

Where the Company has no continuing involvement under a collaborative arrangement, the Company records nonrefundable license fee revenue when the Company has the contractual right to receive the payment, in accordance with the terms of the license agreement, and records milestones upon appropriate notification to the Company of achievement of the milestones by the collaborative partner.

In March 2003, the Company entered into a final settlement agreement with Sumitomo Pharmaceuticals Co., Ltd. (“Sumitomo”) under which the rights to develop and commercialize telbivudine, the Company’s lead product candidate for the treatment of hepatitis B, in Japan, China, South Korea and Taiwan previously granted to Sumitomo were returned to the Company. This agreement with Sumitomo became effective upon consummation of the Company’s collaboration with Novartis in May 2003. The Company repurchased these product rights for $5,000,000 and, as a result of this payment, the Company reversed approximately $4,571,000 of revenue previously recognized in original arrangements with Sumitomo with the remaining amount recorded as a reduction of deferred revenue. The Company also has $4,272,000 included in deferred revenue on its consolidated balance sheet at each of December 31, 2004 and September 30, 2005, representing amounts received from Sumitomo that have not been included in revenue to date. The Company must pay an additional $5,000,000 to Sumitomo upon the first commercial sale of telbivudine in Japan. This payment will be recorded first as a reduction of the remaining $4,272,000 of deferred revenue, with the excess recorded as an expense. If and when the Company determines that it will not seek regulatory approval for telbivudine in Japan, the Company would have no further obligations under the settlement agreement with Sumitomo and, therefore, the $4,272,000 of remaining deferred revenue would be recognized as revenue at that time.

In November 2002, the Emerging Issues Task Force (“EITF”), reached a consensus on EITF No. 00-21, ‘‘Accounting for Revenue Arrangements with Multiple Deliverables’’ (“EITF No. 00-21”). EITF No. 00-21 provides guidance on how to account for arrangements that involve the delivery or performance of multiple products, services and/or rights to use assets. The provisions of EITF No. 00-21 apply to revenue arrangements with multiple deliverables entered into or modified on or after July 1, 2003. The Company presently has no revenue arrangements required to be accounted for under EITF No. 00-21.

IDENIX PHARMACEUTICALS, INC.
NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

Government Research Grant Revenue – Government research grants that provide for payments to the Company for work performed are recognized as revenue when the related expense is incurred and the Company has obtained governmental approval to use the grant funds for these expenses.

Marketable Securities

The Company invests its excess cash balances in short-term and long-term marketable debt securities. The Company classifies all of its marketable securities as available-for-sale. The Company reports available-for-sale investments at fair value as of each balance sheet date and includes any unrealized gains and to the extent deemed temporary, unrealized losses in stockholders’ equity. If any adjustment to fair value reflects a decline in the value of the investment, the Company considers available evidence to evaluate whether the decline is “other than temporary” and, if so, marks the investment to market through a charge to the consolidated statement of operations. Realized gains and losses are determined on the specific identification method and are included in investment income. The Company classifies its marketable securities with remaining maturities of 12 months or less as current marketable securities exclusive of those categorized as cash equivalents. The Company classifies its marketable securities with remaining maturities greater than 12 months as non-current marketable securities, unless it is not expected to hold the investment to maturity.

Stock-Based Compensation

As permitted by Statement of Financial Accounting Standards (“SFAS”) No. 123, “Accounting for Stock-Based Compensation” (“SFAS No. 123”), the Company accounts for its stock-based awards to employees and directors using the intrinsic method prescribed in Accounting Principles Board Opinion No. 25 (“APB No. 25”), “Accounting for Stock Issued to Employees,” and related interpretations. Changes to option terms subsequent to award can also give rise to compensation expense. The Company recognizes compensation expense for restricted stock sold and stock options granted to nonemployees in accordance with the requirements of SFAS No. 123 and EITF Issue No. 96-18, “Accounting for Equity Instruments that Are Issued to Other than Employees for Acquiring, or in Conjunction with Selling Goods and Services” (“EITF 96-18”). EITF 96-18 requires that such equity instruments be recorded at their fair value at the measurement date, which is generally the vesting date of the instruments. Therefore, the measurement of stock-based compensation is subject to periodic adjustment as the underlying equity instruments vest.

In December 2002, the Financial Accounting Standards Board (“FASB”) issued SFAS No. 148, “Accounting for Stock-Based Compensation – Transition and Disclosure – An amendment of FAS 123” (“SFAS No. 148”). This statement provides alternative methods of transition for a voluntary change to the fair value method of accounting for stock-based employee compensation. SFAS No. 148 also requires that disclosures of the pro forma effect of using the fair value method of accounting for stock-based compensation be displayed more prominently and in tabular format. Additionally, SFAS No. 148 requires disclosure of the pro forma effect in the interim financial statements. The Company has elected to continue to account for employee stock options under APB No. 25.

In December 2004, the FASB issued SFAS No. 123 (revised 2004), “Share-Based Payment”. This Statement replaces SFAS No. 123 and supercedes APB No. 25. SFAS No. 123 (revised 2004) eliminates the ability to account for share-based compensation transactions using the intrinsic method currently used by the Company. SFAS No. 123 (revised 2004) requires such transactions to be accounted for using a fair value based method that would result in expense being recognized in the Company’s financial statements. The Company will be required to adopt SFAS No. 123 (revised 2004) in the first quarter of fiscal 2006 and has not yet determined the impact of adoption on the consolidated financial position or results of operations.

IDENIX PHARMACEUTICALS, INC.
NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

If compensation expense for the Company’s stock-based compensation plan had been determined based on the fair value using the Black-Scholes method at the grant dates as calculated in accordance with SFAS No. 123, the Company’s net (loss) income and net (loss) income per common share would have approximated the pro forma amounts below:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2005			2004			2005			2004
	(in thousands, except						(in thousands, except
	per share data)						per share data)
Net (loss) income:
Net (loss) income — as reported	$	(13,698	)	$	(7,353	)	$	(36,397	)	$	7,710
Add stock-based employee compensation expense included in reported net (loss) income		339			529			1,306			1,592
Deduct stock-based employee compensation expense determined under fair value method		(1,707	)		(844	)		(4,853	)		(2,248	)

Net (loss) income — pro forma	$	(15,066	)	$	(7,668	)	$	(39,944	)	$	7,054
Net (loss) income per share:
Basic — as reported	$	(0.28	)	$	(0.17	)	$	(0.76	)	$	0.20
Basic — pro forma	$	(0.31	)	$	(0.17	)	$	(0.83	)	$	0.18
Diluted — as reported	$	(0.28	)	$	(0.17	)	$	(0.76	)	$	0.19
Diluted — pro forma	$	(0.31	)	$	(0.17	)	$	(0.83	)	$	0.17

The assumptions used were as follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2005			2004			2005			2004
Expected dividend yield		—			—			—			—
Risk-free interest rate		4.05	%		3.55	%		3.91	%		3.24	%
Expected option term (in years)		5			5			5			5
Expected volatility		75	%		85	%		83	%		21	%

Basic and Diluted Net (Loss) Income per Common Share

The Company accounts for and discloses net (loss) income per common share in accordance with SFAS No. 128, “Earnings Per Share” (“SFAS No. 128”). Under the provisions of SFAS No. 128, basic net (loss) income per common share is computed by dividing the net (loss) income available to common stockholders by the weighted average number of common shares outstanding during the period. Diluted net (loss) income per common share is computed by dividing the net (loss) income available to common stockholders by the weighted average number of common shares and dilutive potential common shares outstanding. These potential common shares consist of common shares issuable upon the assumed exercise of outstanding stock options (using the treasury stock method), issuance of contingently issuable shares subject to Novartis subscription rights (see Note 4) and restricted stock awards.


	Three Months Ended September 30,						Nine Months Ended September 30,
	2005			2004			2005			2004
	(in thousands, except						(in thousands, except
	per share data)						per share data)
Basic and diluted net (loss) income per common share:
Net (loss) income	$	(13,698	)	$	(7,353	)	$	(36,397	)	$	7,710
Common Shares:
Weighted average number of common shares outstanding for basic net (loss) income per share:		48,220			44,520			48,100			39,190
Net effect of dilutive stock options		—			—			—			1,226
Effect of contingently issuable shares subject to Novartis stock purchase rights		—			—			—			945

Weighted average number of common shares outstanding for diluted net (loss) income per share:		48,220			44,520			48,100			41,361
Basic net (loss) income per common share	$	(0.28	)	$	(0.17	)	$	(0.76	)	$	0.20
Diluted net (loss) income per common share	$	(0.28	)	$	(0.17	)	$	(0.76	)	$	0.19

IDENIX PHARMACEUTICALS, INC.
NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

The following potentially dilutive, common share equivalents were excluded from the calculation of diluted net loss per common share because their effect was anti-dilutive:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2005		2004		2005		2004
	(in thousands)				(in thousands)
Options		3,826		3,003		3,826		205
Shares contingently issuable to related party		1,254		945		1,254		—
Restricted stock		13		100		13		—

3. COMPREHENSIVE (LOSS) INCOME

For the three and nine months ended September 30, 2005 and 2004, respectively, comprehensive (loss) income was as follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2005			2004			2005			2004
	(in thousands)						(in thousands)
Net (loss) income	$	(13,698	)	$	(7,353	)	$	(36,397	)	$	7,710
Changes in other comprehensive (loss) income:
Foreign currency translation adjustment		(31	)		—			(462	)		(72	)
Unrealized gain (loss) on investments		72			(28	)		24			(28	)

Total comprehensive (loss) income	$	(13,657	)	$	(7,381	)	$	(36,835	)	$	7,610

4. NOVARTIS RELATIONSHIP

Overview

In May 2003, the Company entered into a collaboration with Novartis relating to the worldwide development and commercialization of the Company’s product candidates. Novartis paid the Company a license fee of $75,000,000 for its lead HBV product candidates, telbivudine and valtorcitabine, has agreed to provide development funding for these HBV product candidates and will make milestone payments, which could total up to $35,000,000, upon the achievement of certain regulatory approvals, as well as additional milestone payments based upon achievement of predetermined sales levels.

Novartis also acquired an option to license the Company’s HCV and other product candidates. If Novartis exercises its option to collaborate on valopicitabine, the Company’s initial HCV product candidate, it would be required to provide development funding and pay the Company up to $525,000,000 in license fees and regulatory milestone payments, as well as additional milestone payments based upon achievement of predetermined sales levels. In June 2004, the Company received a $25,000,000 milestone payment from Novartis that it recognized as revenue based upon results from a phase I clinical trial of valopicitabine, also known as, NM283.

The Company is reimbursed by Novartis on a quarterly basis for expenses incurred by the Company in connection with the development of its HBV product candidates. Pursuant to a cost sharing arrangement with Novartis, the Company is also reimbursed for certain registration expenses and phase IIIb/IV clinical trial costs associated with telbivudine, net of certain qualifying costs incurred by Novartis.

IDENIX PHARMACEUTICALS, INC.
NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

Simultaneously with the collaboration described above, Novartis purchased approximately 54% of the Company’s outstanding capital stock from the Company’s then existing stockholders for $255,000,000 in cash, with an additional aggregate amount of up to additional $357,000,000 contingently payable to these stockholders if the Company achieves predetermined development milestones relating to an HCV product candidate. As of the completion of the public offering in October 2005, Novartis owns approximately 56% of the Company’s outstanding stock.

To date, the Company has received from Novartis a $75,000,000 license fee for its HBV product candidates and a $5,000,000 reimbursement for reacquiring product rights from Sumitomo to develop and commercialize telbivudine in certain markets in Asia. The Company has included this reimbursement as part of the license fee for accounting purposes because Novartis required the repurchase of these rights as a condition of entering into the development agreement. The Company has estimated that the performance period during which the development of the HBV product candidates and valopicitabine would occur is a period of approximately six and one-half years following the effective date of the development agreement that the Company entered into with Novartis, or December 2009. The Company is recognizing revenue on the license fee payments over this period. If the estimated performance period changes, the Company will adjust the periodic revenue that is being recognized and will record the remaining unrecognized license fee payments over the remaining development period during which the Company’s performance obligations will be completed. Significant judgments and estimates are involved in determining the estimated development period and different assumptions could yield materially different results.

Novartis’ Stock Purchase Rights

Novartis has the right to purchase, at par value of $0.001 per share, such number of shares as is required to maintain its percentage ownership of the Company’s voting stock if the Company issues shares of capital stock in connection with the acquisition or in-licensing of technology through the issuance of up to 5% of the Company’s stock in any 24-month period. These purchase rights of Novartis remain in effect until the earlier of: a) the date that Novartis and its affiliates own less than 19.4% of the Company’s voting stock; or b) the date that Novartis becomes obligated to make the additional contingent payments of $357,000,000 to holders of the Company’s stock who sold shares to Novartis on May 8, 2003.

Additionally, if the Company issues any shares of its capital stock, other than in certain situations, Novartis has the right to purchase such number of shares required to maintain its percentage ownership of the Company’s voting stock for the same consideration per share paid by others acquiring the Company’s stock. Upon the grant of options and stock awards under stock incentive plans, with the exception of the 1998 Equity Incentive Plan, the fair value of the Company’s common stock that would be issuable to Novartis, less the exercise price, if any, payable by the option or award holder, will be recorded as a reduction of the license fee associated with the Novartis collaboration. The amount will be attributed proportionately between cumulative revenue recognized through that date and the remaining amount of deferred revenue. These amounts will be adjusted through the date that Novartis elects to purchase the shares to maintain its percentage ownership based upon changes in the value of the Company’s common stock and in Novartis’ percentage ownership. These adjustments will also be attributed proportionately between cumulative revenue recognized through the measurement date and the remaining deferred revenue.

In connection with the closing of the Company’s initial public offering in July 2004, Novartis terminated a common stock subscription right with respect to 1,399,106 shares of common stock issuable by the Company as a result of the exercise of stock options granted after May 8, 2003 pursuant to the 1998 Equity Incentive Plan. In exchange for Novartis’ termination of such right, the Company issued 1,100,000 shares of common stock to Novartis for a purchase price of $0.001 per share. The fair value of these shares was determined to be $15,400,000 at the time of issuance. As a result of the issuance of these shares,

IDENIX PHARMACEUTICALS, INC.
NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

Novartis’ rights to purchase additional shares as a result of future option grants and stock issuances under the 1998 Equity Incentive Plan are terminated, and no additional adjustments to revenue and deferred revenue will be required. Prior to the termination of the stock subscription rights under the 1998 Equity Incentive Plan, as the Company granted options that were subject to this stock subscription right, the fair value of the Company’s common stock that would be issuable to Novartis, less par value, was recorded as a adjustment of the license fee and payments received from Novartis. The Company is still subject to potential revenue adjustments relating to future grants of options and stock awards under other stock incentive plans.

As of September 30, 2005, this Novartis stock subscription right has reduced the license fee by a cumulative total of $22,182,000 and has been reclassified to additional paid-in capital. Of this amount, $17,069,000 has been recorded as a reduction of deferred revenue as of September 30, 2005 with the remaining amount of $5,113,000 recorded as a reduction of revenue. The Company recorded a $1,554,000 reduction of revenue for the three months ended September 30, 2005 and a $611,000 increase to revenue for the three months ended September 30, 2004 associated with this stock subscription right. The Company recorded $2,451,000 and $1,850,000 of this reduction of revenue for the nine months ended September 30, 2005 and 2004, respectively.

5. SUBSEQUENT PUBLIC OFFERING OF COMMON STOCK

On October 31, 2005, the Company completed a public offering of 7,278,020 shares of its common stock at a purchase price to the public of $20.61 per share, resulting in proceeds to the Company of approximately $145,500,000, after deducting underwriting discounts and commissions and estimated offering expenses. Of the shares offered and sold by the Company, 3,939,131 shares were sold to Novartis.

6. MARKETABLE SECURITIES

The Company invests its excess cash with large U.S. based financial institutions and considers its investment portfolio as marketable securities available-for-sale as defined in SFAS No. 115, “Accounting for Certain Investments in Debt and Equity Securities.” Accordingly, these investments are recorded at fair value, which is based on quoted market prices. The fair values of available-for-sale investments by type of security, contractual maturity and classification in the balance sheets as of September 30, 2005 and December 31, 2004 are as follows:

IDENIX PHARMACEUTICALS, INC.
NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED


	September 30, 2005
			Gross		Gross
	Amortized		unrealized		unrealized			Market
	cost		gains		losses			value
	(In thousands)
Type of security:
Money market funds	$	6,335	$	—	$	—		$	6,335
Corporate debt securities		41,857		—		(221	)		41,636
U.S. Treasury securities and obligations of U.S. government agencies		17,504		—		(85	)		17,419
Taxable auction rate securities		17,492		1		(13	)		17,480
Accrued interest		616		—		—			616

	$	83,804	$	1	$	(319	)	$	83,486


	September 30,		December 31,
	2005		2004
	(In thousands)
Contractual maturity:
Maturing in one year or less	$	71,485	$	59,505
Maturing after one year through two years		2,000		40,679
Maturing after two years through ten years		3,000		15,500
Maturing after ten years		7,001		20,575

	$	83,486	$	136,259


	December 31, 2004
			Gross		Gross
	Amortized		unrealized		unrealized			Market
	cost		gains		losses			value
	(In thousands)
Type of security:
Money market funds	$	13,040	$	—	$	—		$	13,040
Corporate debt securities		40,102		26		(232	)		39,896
U.S. Treasury securities and obligations of U.S. government agencies		34,252		—		(137	)		34,115
Taxable auction rate securities		48,570		—		—			48,570
Accrued interest		638		—		—			638

	$	136,602	$	26	$	(369	)	$	136,259

Included in the table above are taxable auction rate securities, which typically reset to current interest rates every 28 to 45 days, but are included in the table above based on their stated maturities. All securities with contractual maturities greater than two years are taxable auction rate securities.

IDENIX PHARMACEUTICALS, INC.
NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED


	September 30,		December 31,
	2005		2004
	(In thousands)
Classification in balance sheets:
Cash equivalents	$	10,443	$	21,076
Marketable securities		61,042		38,429
Marketable securities, non-current		12,001		76,754

	$	83,486	$	136,259

The cash equivalent amounts of $10,443,000 and $21,076,000 are included as part of cash and cash equivalents on the Company’s consolidated balance sheet at September 30, 2005 and December 31, 2004, respectively.

7. ACCOUNTS RECEIVABLE

Accounts receivable consist of the following:


	September 30,		December 31,
	2005		2004
	(in thousands)
Accounts receivable, related party	$	2,026	$	—
Unbilled accounts receivable, related party		14,634		16,243

	$	16,660	$	16,243

Unbilled accounts receivable are revenues earned under collaborative agreements that have not been billed at September 30, 2005 and December 31, 2004. All related party billed and unbilled accounts receivable are due from Novartis.

8. ACCRUED EXPENSES

Accrued expenses consist of the following:


	September 30,		December 31,
	2005		2004
	(in thousands)
Research and development contract costs	$	12,562	$	8,064
Payroll and employee benefits		3,278		2,649
Professional fees		1,059		2,412
License fees		1,000		1,000
Other		2,532		1,175

	$	20,431	$	15,300

IDENIX PHARMACEUTICALS, INC.
NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

9. LEGAL CONTINGENCIES

Hepatitis C Product Candidates

In May 2004, the Company and, in an individual capacity, its Chief Executive Officer (“CEO”), entered into a settlement agreement with the University of Alabama at Birmingham (“UAB”) and its affiliate, the UAB Research Foundation (“UABRF”), to resolve a dispute among these parties. In March 2004, the Company and, in an individual capacity, its CEO, filed a lawsuit against UABRF in the United States District Court, District of Massachusetts, seeking declaratory judgment regarding the Company’s ownership of inventions and discoveries made during the period from November 1999 to November 2002 (“Leave Period”) by the CEO and the Company’s ownership of patents and patent applications related to such inventions and discoveries. During the Leave Period, while acting in the capacity of the Company’s Chief Scientific Officer, the CEO was on sabbatical from November 1999 to November 2000 (“Sabbatical Period”) and then unpaid leave prior to resigning in November 2002 from his position as a professor at UAB.

As a part of the settlement agreement, UAB and UABRF agreed that neither UAB or UABRF has any right, title or ownership interest in the inventions and discoveries made or reduced to practice during the Leave Period or the related patents and patent applications. In exchange, the Company made a $2,000,000 payment to UABRF in May 2004, dismissed the pending litigation and agreed to make certain future payments to UABRF. These future payments consist of (i) a $1,000,000 payment upon the receipt of regulatory approval to market and sell in the U.S. a product which relates to inventions and discoveries made by the CEO during the Sabbatical Period, and (ii) payments in an amount equal to 0.5% of worldwide net sales of such products with a minimum sales based payment to equal $12,000,000. The sales based payments (including the minimum amount) are contingent upon the commercial launch of products that relate to inventions and discoveries made by the CEO during the Sabbatical Period. The minimum amount is due within seven years after the later of the commercial launch in the United States or any of the United Kingdom, France, Germany, Italy or Spain, of a product that (i) has within its approved product label a use for the treatment of hepatitis C infection, and (ii) relates to inventions and discoveries made by the CEO during the Sabbatical Period, if sales based payments for such product have not then exceeded $12,000,000. At that time, the Company will be obligated to pay to UABRF the difference between the sales based payments then paid to date for such product and $12,000,000.

Hepatitis B Product Candidates

In addition to the Leave Period matter noted above, the Company was notified in January 2004, February 2005 and June 2005, that UABRF believes that patent applications which the Company has licensed from UABRF can be amended to obtain broad patent claims that would generally cover the method of using telbivudine to treat HBV. In July 2005, UABRF filed this continuation patent application. The Company disagrees with UABRF’s assertion. If UABRF pursues such patent claims, they could assert that the obligations of the Company arising under the license agreement with respect to licensed technology (including the amount and manner of payments due) are applicable to the Company’s intended use of telbivudine to treat hepatitis B. The agreement requires the Company to make, for each significant disease indication for which licensed technology is used, payments aggregating $1,300,000 if certain regulatory milestones are met. Additionally, if commercialization is achieved for a licensed product, the Company will be required to pay a royalty with respect to annual net sales of licensed products by the Company or an affiliate of the Company at the rate of 6% for net sales up to $50,000,000 and at the rate of 3% for net sales in excess of $50,000,000. If the Company enters into a sublicense arrangement with an entity other than one which controls at least 50% of the Company’s capital stock, the Company would be required to remit to UABRF 30% of all royalties received by the Company on sales of the licensed product by the sublicensee. The Company is also required to pay to UABRF 20% of all license fees, milestone payments and other cash consideration the Company receives from the sublicensee with respect to the licensed products. If UABRF’s position were to be upheld, and telbivudine was found to be covered by the agreement, the Company could be required to pay UABRF $15,000,000 related to the upfront payment received from Novartis. In addition, the Company could have to pay future royalties to UABRF. The Company does not believe that it is probable that UABRF’s position will be upheld.

Indemnification

The Company has agreed to indemnify Novartis and its affiliates against losses suffered as a result of any breach of representations and warranties in the development agreement. Under the development agreement and the stock purchase agreement, the Company made numerous representations and warranties to Novartis regarding its hepatitis B and C product candidates, including representations regarding the

IDENIX PHARMACEUTICALS, INC.
NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
(UNAUDITED) — CONTINUED

Company’s ownership of the inventions and discoveries described above. If one or more of the representations or warranties were not true at the time they were made to Novartis, the Company would be in breach of one or both of these agreements. In the event of a breach by the Company, Novartis has the right to seek indemnification from the Company and, under certain circumstances, the Company and its stockholders who sold shares to Novartis, which include many of its directors and officers, for damages suffered by Novartis as a result of such breach. While it is possible that the Company may be required to make payments pursuant to the indemnification obligations it has under the development agreement, the Company cannot reasonably estimate the amount of such payments or the likelihood that such payments will be required.

10. EQUITY INCENTIVE PLANS

In June 2005, the Company’s stockholders approved the 2005 Stock Incentive Plan (“2005 Plan”). The 2005 Plan allows for the granting of incentive stock options, non-qualified stock options, stock appreciation rights, performance share awards and restricted stock awards (“Awards”). The 2005 Plan, as approved by the Company’s stockholders, provided for the authorization of Awards covering an aggregate of 2,200,000 shares of common stock plus 800,000 shares previously authorized for issuance under the 2004 Stock Incentive Plan. In October 2005, the Company’s Board of Directors reduced the number of shares of common stock reserved for issuance under the 2005 Plan to 1,400,000 shares.

11. COLLABORATIVE AGREEMENTS AND CONTRACTS

On October 24, 2005, the Company entered into an agreement with the Universita’ degli Studi di Cagliari (the “University of Cagliari”). This agreement further amends the Co-Operative Antiviral Research Activity Agreement, dated January 4, 1999, between the University of Cagliari and the Company’s French subsidiary, as amended, and the License Agreement, dated December 14, 2000, between the University of Cagliari and the Company, as amended (the “License Agreement”). The agreement provides that the Company will pay to the University of Cagliari certain fees if the Company receives payments in the future from an affiliate of the Company with respect to the technology licensed to the Company pursuant to the License Agreement.

12. RELATED PARTY TRANSACTIONS

Prior to June 7, 2005, the Company had on its board of directors a partner in the law firm of Wilmer Cutler Pickering Hale and Dorr LLP. The Company retains Wilmer Cutler Pickering Hale and Dorr LLP as its corporate counsel. The Company incurred legal expenses of $120,000 and $578,000 during the nine months ended September 30, 2005 and 2004, respectively, for services rendered by Wilmer Cutler Pickering Hale and Dorr LLP during the period in which such law firm partner was on the Company's board of directors.

ITEM 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations

Forward-Looking Information and Factors That May Affect Future Results

This report contains “forward-looking statements” within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended. For this purpose, any statements contained herein regarding our strategy, future operations, financial position, future revenues, projected costs and expenses, prospects, plans and objectives of management, other than statements of historical facts, are forward-looking statements. The words “anticipate,” “believes,” “estimates,” “expects,” “intends,” “may,” “plans,” “projections,” “will,” “would” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Such statements reflect our current views with respect to future events. We cannot guarantee that we actually will achieve the plans, intentions, or expectations disclosed in our forward-looking statements. There are a number of important factors that could cause actual results or events to differ materially from those disclosed in the expressed or implied forward-looking statements we make. These important factors include our “critical accounting estimates” and the risk factors set forth below under the caption “Factors That May Affect Future Results.” Although we may elect to update forward-looking statements in the future, we specifically disclaim any obligation to do so, even if our estimates change, and readers should not rely on those forward-looking statements as representing our views as of any date subsequent to the date of this quarterly report.

Overview

Idenix is a biopharmaceutical company engaged in the discovery, development and commercialization of products for the treatment of human viral and other infectious diseases. Our current focus is on the treatment of infections caused by hepatitis B virus, or HBV, hepatitis C virus, or HCV and human immunodeficiency virus, or HIV. Each of telbivudine and valtorcitabine, our product candidates for the treatment of HBV, and valopicitabine, our product candidate for the treatment of HCV, is a nucleoside or nucleoside analog that we believe may have one or more therapeutic features that will afford competitive advantages to our product candidates over currently approved therapies. Such therapeutic features may include efficacy, safety, resistance profile or convenience of dosing. Each of the product candidates that we are developing is selective and specific, may be administered orally once a day, and we believe may be used in combination with other therapeutic agents to improve clinical benefits.

The following table summarizes key information regarding our pipeline of product candidates:


	Drug		Next
	Candidates/		Development
Indication	Programs	Description	Stage
HBV	telbivudine (L-nucleoside)	Telbivudine achieved the primary endpoint in our phase III registration trial, referred to as the GLOBE study, in July 2005. Submission to the United States Food and Drug Administration, or FDA, of a new drug application, or NDA, based on one-year data from this phase III registration trial is anticipated in December 2005. In addition to the GLOBE study, a phase III trial in patients with liver failure, or decompensated liver disease, is ongoing. Also ongoing are marketing trials that are intended to provide additional product data at the time of commercial launch of telbivudine.	NDA

HBV	valtorcitabine (L-nucleoside)	This product candidate is being developed for use in fixed dose combination with telbivudine for treatment of hepatitis B patients who require more intensive antiviral therapy than achieved by single agent therapy. A phase IIb clinical trial of the combination of valtorcitabine and telbivudine is ongoing.	phase III


	Drug		Next
	Candidates/		Development
Indication	Programs	Description	Stage
HCV	valopicitabine (NM283) (Nucleoside analog)	This product candidate is being developed as a potentially more effective alternative to ribavirin in interferon-based therapy for patients that have failed prior therapy, referred to as treatment-refractory patients, and for patients that have not been treated for chronic HCV infection, referred to as treatment-naive patients.


		Treatment-Refractory Patients	phase III

		A phase IIb clinical trial of the combination of valopicitabine and pegylated interferon in treatment-refractory patients is ongoing. The data to date indicate that after 12 weeks of treatment with the combination of one daily dose of 800 milligrams of valopicitabine and once a week pegylated interferon there was a statistically significant improvement in patients’ viral load reduction and early viral response rates compared to retreatment with the current standard of treatment. Early viral response is defined as a reduction of at least 2 log₁₀, or 99% or more, of HCV levels in a patient’s blood.

		Treatment-Naive Patients	phase III

		A phase IIa clinical trial of the combination of valopicitabine and pegylated interferon in treatment-naive patients is ongoing. The preliminary data indicate a mean reduction from baseline levels of hepatitis C virus in patients’ blood serum of 4.2 log^10, or more than a 99.99% reduction in viral load, at week 24 in nine patients receiving the combination therapy. A phase IIb clinical trial of the combination of valopicitabine and pegylated interferon in treatment naive patients is also ongoing. We anticipate completing enrollment of this trial by the end of 2005.

HCV	NV-08 (Nucleoside analogs)	Preclinical evaluation of product candidates from this program is in progress. This program consists of structurally different chemical classes than valopicitabine. We are seeking a candidate that may be developed for use in combination with valopicitabine.	phase I*

HIV	NV-05 (Non-nucleoside reverse transcriptase inhibitors or NNRTIs)	Lead compounds from two novel series are being evaluated in preclinical studies. We expect to file an investigational new drug application, or IND, in 2006 for one of the most promising product candidates among these lead compounds.	phase I*


*		Phase I clinical trial is expected to incorporate certain of the objectives of a phase II clinical trial.

In October 2005, we completed a public offering of our common stock. In this transaction we issued and sold 7,278,020 shares of common stock, including 3,939,131 shares of common stock sold to Novartis. From this sale of stock we received approximately $145.5 million in proceeds, after deducting underwriting discounts and commissions and offering expenses.

In May 2003, we entered into a collaboration with Novartis relating to the worldwide development and commercialization of our product candidates. Novartis paid us a license fee of $75 million for our lead HBV product candidates, telbivudine and valtorcitabine, has agreed to provide development funding for these HBV product candidates and will make milestone payments, which could total up to $35 million upon the achievement of specific regulatory approvals, as well as additional milestone payments based upon achievement of predetermined sales levels.

Novartis also acquired an option to license our HCV and other product candidates. If Novartis exercises its option to collaborate with us on valopicitabine, also known as NM283, our initial HCV

product candidate, it would be required to provide development funding and pay us up to $525 million in license fees and regulatory milestone payments, as well as additional milestone payments based upon achievement of predetermined sales levels. We will co-promote or co-market with Novartis in the United States, the United Kingdom, France, Germany, Italy and Spain all products Novartis licenses from us that are successfully developed. Novartis has the exclusive right to promote and market such products in the rest of the world. In June 2004, we received a $25 million milestone payment from Novartis based upon the results from our phase I clinical trial of valopicitabine.

In addition to the collaboration described above, Novartis purchased approximately 54% of our outstanding capital stock in May 2003 from our then existing stockholders for $255 million in cash, with an additional aggregate amount of up to $357 million contingently payable to these stockholders if we achieve predetermined development milestones relating to an HCV product candidate.

Novartis has the right to purchase from us that number of shares of our common stock as is required to enable Novartis to maintain its percentage ownership in our company that it acquired in May 2003. Novartis also has a contractual right to exercise control over corporate actions that may not require stockholder approval as long as it holds at least 19.4% of our voting stock. After giving effect to the completed public offering on October 31, 2005, Novartis owned approximately 56% of our outstanding common stock.

All of our product candidates are currently in preclinical or clinical development. To commercialize our product candidates, we will be required to successfully complete preclinical studies and clinical trials to obtain required regulatory approvals. We do not expect to submit an NDA to the FDA for a product candidate we are developing prior to December 2005. Any delay in obtaining or failure to obtain required approvals will materially adversely affect our ability to generate revenues from commercial sales relating to our product candidates. Accordingly, we expect our sources of funding for the next several years to include the reimbursement of expenses we may incur in connection with the development of licensed product candidates, license fees relating to valopicitabine and other product candidates we may successfully develop and license and milestone payments under existing and future collaborative arrangements. We may also need to seek additional financing to fund our future operations.

We have incurred significant losses since our inception in May 1998 and expect such losses to continue in the foreseeable future. Historically, we have generated losses principally from costs associated with research and development activities, including clinical trial costs, and general and administrative activities. As a result of planned expenditures for future discovery, development and commercialization activities and the expansion of our sales, operational and administrative infrastructure, we expect to incur additional operating losses for the foreseeable future.

Our research and development expenses consist primarily of salaries and payroll-related expenses for research and development personnel, including stock-based compensation, fees paid to clinical research organizations and other professional service providers in conjunction with our clinical trials, fees paid to research organizations in conjunction with animal studies, costs of material used in research and development, costs of contract manufacturing consultants, occupancy costs associated with the use of our research facilities and equipment, consulting and license fees paid to third parties, and depreciation of property and equipment related to research and development. The majority of our research and development spending is incurred on clinical, preclinical and manufacturing activity with third-party contractors relating to the development of our HBV and HCV product candidates. We expense internal and external research and development costs as incurred. We expect our research and development expenses to increase as we continue to engage in research activities, further develop our potential product candidates and advance our clinical trials.

Pursuant to our development agreement with Novartis, after it licenses a product candidate, Novartis is obligated to fund development expenses that we incur in accordance with development plans agreed upon by us and Novartis. The option we have granted to Novartis with respect to its right to license our product candidates generally requires that Novartis exercise the option for each such product candidate prior to the commencement of phase III clinical trials. The expenses associated with phase III clinical trials generally are the most costly component in the development of a successful new product.

Results of Operations

Comparison of Three Months Ended September 30, 2005 and 2004

Revenues

Total revenues were $15.6 million for the three months ended September 30, 2005 as compared with $17.2 million for the three months ended September 30, 2004.

Total revenues for the three months ended September 30, 2005 were primarily comprised of $15.5 million in related party revenue from Novartis consisting of $0.9 million in license fee revenue, net of a $1.6 million reduction due to Novartis stock subscription rights, and $14.6 million for reimbursement of research and development expenses, net of a $0.2 million cost sharing arrangement for expenses incurred by Novartis for certain registration expenses and phase IIIb clinical trials associated with telbivudine.

Total revenues for the three months ended September 30, 2004 were primarily comprised of $17.1 million in related party revenue from Novartis, consisting of $3.0 million in license fee revenue, including $0.6 million associated with the termination of certain Novartis stock subscription rights, and $14.1 million for reimbursement of research and development expenses.

The decrease in revenues of $1.6 million for the three months ended September 30, 2005 in comparison with the prior reporting period was primarily due to the impact of revenue reductions related to the Novartis stock subscription rights.

Research and Development Expenses

Research and development expenses were $21.5 million for the three months ended September 30, 2005 as compared with $19.0 million for the three months ended September 30, 2004. The increase of $2.5 million was primarily due to an increase of $1.2 million in expenses for third-party contractors, principally associated with phase III clinical trials of telbivudine and phase IIb clinical trials of valtorcitabine and valopicitabine. The increase was also due to an increase of $0.9 million in salary and other payroll-related expenses reflecting increased hiring of personnel as we expand our research and development activities.

We expect our research and development expenses to increase in future periods as we continue to devote substantial resources to these activities and we engage in a greater number of later stage clinical trials.

General and Administrative Expenses

General and administrative expenses were $4.8 million for the three months ended September 30, 2005 as compared with $4.2 million for the three months ended September 30, 2004. The increase of $0.6 million was primarily due to an increase in salary and payroll-related expenses associated with the hiring of additional personnel as we expand our operations.

We expect that our general and administrative expenses will increase in the future as we continue to expand our finance and accounting staff, maintain and enforce our patents and implement new computer systems.

Sales and Marketing Expenses

Sales and marketing expenses were $4.2 million for the three months ended September 30, 2005 as compared with $1.8 million for the three months ended September 30, 2004. The increase of $2.4 million was primarily due to an increase of $1.6 million in consulting expenses and an increase of $0.7 million in salary and payroll-related expenses as we engage in additional marketing activities in anticipation of the expected commercial launch of telbivudine.

We expect that sales and marketing expenses will increase significantly in the future as we increase our marketing activities, build a commercial infrastructure, hire additional marketing staff and recruit a specialized sales force in the U.S. and Europe in anticipation of the marketing and sale of product candidates which we may successfully develop and commercialize in the future.

Investment Income, Net

Net investment income was $0.7 million for the three months ended September 30, 2005 as compared with $0.5 million for the three months ended September 30, 2004. The increase of $0.2 million was primarily the result of higher average cash and marketable securities balances held during the quarter ended September 30, 2005 as compared to the quarter ended September 30, 2004 due to the receipt of net proceeds of $132.6 million from the initial public offering and concurrent private placement of our common stock to Novartis in July 2004.

Income Taxes

Income tax benefit was approximately $0.5 million for the three months ended September 30, 2005 as compared with $39,000 for the three months ended September 30, 2004. The income tax benefit for the three months ended September 30, 2005 was due to amounts our French subsidiary has received or is expected to receive for certain research and development credits relating to increased research spending in our facilities in France and Italy. Our income tax expense generally consists of tax expenses incurred by our U.S., French and Dutch subsidiaries. Our U.S. and French subsidiaries performed services for us and were reimbursed for these costs, plus a profit margin.

Comparison of Nine Months Ended September 30, 2005 and 2004

Revenues

Total revenues were $46.6 million for the nine months ended September 30, 2005 as compared with $76.6 million for the nine months ended September 30, 2004.

Total revenues for the nine months ended September 30, 2005 were primarily comprised of $46.3 million in related party revenue from Novartis consisting of $4.8 million in license fee revenue, net of a $2.5 million reduction due to Novartis stock subscription rights, and $41.5 million for reimbursement of research and development expenses, net of a $0.8 million cost sharing arrangement for expenses incurred by Novartis for certain registration expenses and phase IIIb clinical trials associated with telbivudine.

Total revenues for the nine months ended September 30, 2004 were primarily comprised of $76.4 million in related party revenue from Novartis, consisting of $6.7 million in license fee revenue, net of a $1.8 million reduction due to Novartis stock subscription rights, $25.0 million in milestone revenue associated with achievement of certain milestones for valopicitabine, and $44.7 million for reimbursement of research and development expenses.

The decrease in revenues of $30.0 million for the nine months ended September 30, 2005 in comparison with the prior reporting period was primarily due to the $25.0 million milestone payment received in June 2004 from Novartis on valopicitabine, lower reimbursements from Novartis as the cost of materials associated with clinical trials on telbivudine decreased in 2005 and the impact related to Novartis stock subscription rights.

Research and Development Expenses

Research and development expenses were $63.1 million for the nine months ended September 30, 2005 as compared with $55.1 million for the nine months ended September 30, 2004. The increase of $8.0 million was principally due to an increase of $4.5 million in expenses for third-party contractors, primarily for clinical trials of telbivudine and valopicitabine, and an increase of $2.5 million in salary and other payroll-related expenses as we expand our research and development activities.

General and Administrative Expenses

General and administrative expenses were $14.7 million for the nine months ended September 30, 2005 as compared with $10.9 million for the nine months ended September 30, 2004. The increase of $3.8 million was primarily due to an increase in salary and payroll-related expenses, an increase in costs for directors’ and officers’ liability insurance coverage associated with being a public company and an increase in professional fees in support of our growing operations.

Sales and Marketing Expenses

Sales and marketing expenses were $8.1 million for the nine months ended September 30, 2005 as compared with $3.7 million for the nine months ended September 30, 2004. The increase of $4.4 million was primarily due to an increase of $2.8 million in consulting expenses and an increase of $1.4 million in salary and payroll-related expenses attributable to marketing activities in anticipation of the expected commercial launch of telbivudine.

Investment Income, Net

Net investment income was $2.3 million for the nine months ended September 30, 2005 as compared with $0.7 million for the nine months ended September 30, 2004. The increase of $1.6 million was the result of higher cash and marketable securities balances held during the nine months ended September 30, 2005 due to the receipt of proceeds from our initial public offering and concurrent private placement of our common stock to Novartis in July 2004.

Income Taxes

Income tax benefit was approximately $0.6 million for the nine months ended September 30, 2005 as compared with $0.2 million for the nine months ended September 30, 2004. The increase in the income tax benefit for the nine months ended September 30, 2005 was primarily due to higher amounts our French subsidiary has received or is expected to receive for certain research and development credits relating to increased research spending in our facilities in France and Italy.

Liquidity and Capital Resources

Since our inception in 1998, we have financed our operations with proceeds obtained in connection with license and development arrangements and equity financings. The proceeds include license, milestone and other payments from Novartis, reimbursements from Novartis for costs we have incurred subsequent to May 8, 2003 in connection with the development of our HBV product candidates, net proceeds from Sumitomo for reimbursement of development costs, net proceeds from private placements of our convertible preferred stock, net proceeds from an initial public offering and concurrent private placement of our common stock in July 2004, net proceeds from the public offering of our common stock in October 2005 and proceeds from the exercise of stock options.

In July 2004, we completed an initial public offering and concurrent private placement in which we issued and sold 4,600,000 shares of common stock in the public offering and 5,400,000 shares of common stock to Novartis in the private placement. We received approximately $132.6 million in net proceeds from these offerings, after deducting underwriting discounts and commissions and offering expenses.

On October 31, 2005, we completed a public offering in which we issued and sold 7,278,020 shares of common stock, including 3,939,131 shares of common stock sold to Novartis. We received approximately $145.5 million in proceeds from this offering, after deducting underwriting discounts and commissions and offering expenses.

We had $41.8 million and $42.1 million in cash and cash equivalents as of September 30, 2005 and December 31, 2004, respectively. We also invest our excess cash balances in short-term and long-term marketable debt securities. All of our marketable securities are classified as available for sale. Our investments have an effective maturity not greater than 18 months and investments with maturities greater

than 12 months are classified as non-current marketable securities. We had $61.0 million and $38.4 million in current marketable securities as of September 30, 2005 and December 31, 2004, respectively. We had $12.0 million and $76.8 million in non-current marketable securities as of September 30, 2005 and December 31, 2004, respectively.

Net cash used in operating activities was $38.7 million for the nine months ended September 30, 2005 compared to net cash used in operating activities of $0.6 million for the nine months ended September 30, 2004. The net cash used in operating activities for the nine months ended September 30, 2005 was primarily attributable to the net loss for the period adjusted for a decrease in deferred revenue due to the amortization of our license fee received from Novartis in 2003. This decrease was offset by an increase in accrued expenses associated with higher research and development spending. The net cash used in operating activities for the nine months ended September 30, 2004 was primarily due to decreases in accounts payable and deferred revenue and an increase in accounts receivable due to greater amounts of research and development expenses being reimbursed by Novartis. These amounts were offset by net income for the period, resulting in part from recognition of a $25.0 million milestone payment from Novartis in the second quarter of 2004 and adjusted for non-cash charges for stock-based compensation and depreciation.

Net cash provided by investing activities was $37.4 million for the nine months ended September 30, 2005 compared to net cash used in investing activities of $45.6 million for the nine months ended September 30, 2004. The net cash provided by investing activities for the nine months ended September 30, 2005 was primarily due to net proceeds from sales of our marketable securities, net of purchases of marketable securities, to fund operations. This increase was offset by capital expenditures primarily for leasehold improvements and computer software. The net cash used in investing activities for the nine months ended September 30, 2004 was primarily due to the investment of a portion of the net proceeds from our initial public offering and concurrent private placement in marketable securities and capital expenditures primarily on leasehold improvements for our facilities in Cambridge, Massachusetts and Cagliari, Italy.

Net cash provided by financing activities was $1.3 million for the nine months ended September 30, 2005 compared to net cash provided by financing activities of $134.3 million for the nine months ended September 30, 2004. The net cash provided by financing activities for the nine months ended September 30, 2005 was due to proceeds from the exercise of stock options. The net cash provided by financing activities for the nine months ended September 30, 2004 was primarily due to net proceeds from the initial public offering and concurrent private placement completed in July 2004.

Set forth below is a description of our contractual obligations as of September 30, 2005:


	Payments Due by Period
					One to
Contractual			Less Than		Three		Four to		After Five
Obligations	Total		One Year		Years		Five Years		Years
					(in thousands)
Operating leases	$	21,048	$	2,421	$	5,393	$	5,164	$	8,070
Consulting, employment and other agreements		17,508		8,717		4,916		3,760		115

Total contractual obligations	$	38,556	$	11,138	$	10,309	$	8,924	$	8,185

In April 2005, we entered into a lease agreement for office and laboratory space in Montpellier, France. The lease term is 12 years expiring in April 2017 but is cancellable by either party after six years. The lease agreement also includes an option entitling us to purchase the building in which the leased space is located at any time after April 16, 2011. The purchase option extends until the expiration of the lease term.

In June 2005, we entered into a lease agreement for additional office space in Cambridge, Massachusetts. The initial lease term is for a period of 54 months expiring in March 2010. The lease agreement also provides us with an option, exercisable not later than nine months prior to the expiration of the initial term, to extend the term of the lease for one additional 48-month period and with rights of first

offer with respect to certain expansion space on two of the floors that we will occupy. In connection with this operating lease commitment, a commercial bank issued a letter of credit in May 2005 for $0.4 million collateralized by cash we have on deposit with that bank. The letter of credit expires in May 2006.

We have certain potential milestone payment obligations under the exclusive license agreement that we entered into with the University of Alabama Research Foundation, or UABRF, in June 1998 and July 1999, that we refer to as the UAB license agreement, our settlement agreement with Sumitomo, and our settlement agreement with UABRF entered into in connection with the resolution of matters relating to certain of our hepatitis C product candidates. The license agreement with UABRF provides for aggregate milestone payments of $1.3 million for each disease indication for which the licensed technology is used. Of this aggregate amount, $0.3 million is payable upon submission of an investigational new drug application or IND, for a product candidate that is covered by claims in patents or patent applications licensed from UABRF and $1.0 million is payable upon approval of an NDA for a product candidate that is covered by claims in patents or patent applications licensed from UABRF. We do not believe that any of the product candidates we are currently developing or those which we currently expect to develop will trigger payments or otherwise result in future obligations under the UAB license agreement. However, if the licensors disagree, they may assert claims to these milestone payments and to additional amounts. The settlement agreement with UABRF, which we entered into in connection with the resolution of matters relating to our hepatitis C product candidate, provides for a milestone payment of $1 million to UABRF upon receipt of regulatory approval in the U.S. to market and sell certain hepatitis C products invented or discovered by our Chief Executive Officer during the period from November 1, 1999 to November 1, 2000. Such hepatitis C products would include valtorcitabine if successfully developed and commercialized.

We believe that the net proceeds from the public offering we completed in October 2005, together with our current cash and cash equivalents and marketable securities and funding we expect to receive from Novartis relating to the development of our HBV product candidates will be sufficient to satisfy our anticipated cash needs for at least the next 24 months. At any time, it is possible that we may seek additional financing. We may seek such financing through a combination of public or private financing, collaborative relationships and other arrangements. Additional funding may not be available to us or, if available, may not be on terms favorable to us. Further, any additional equity financing may be dilutive to stockholders and debt financing, if available, may involve restrictive covenants. Our failure to obtain financing when needed may harm our business and operating results.

Off-Balance Sheet Arrangements

We currently have no off-balance sheet arrangements.

Critical Accounting Policies and Estimates

Our discussion and analysis of our financial position and results of operations are based upon our financial statements, which have been prepared in accordance with accounting principles generally accepted in the United States of America. The preparation of the financial statements requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses. On an ongoing basis, we evaluate our estimates and judgments, including those related to revenue recognition, accrued expenses and the fair value of stock related to stock-based compensation. We base our estimates on historical experience and various other assumptions that we believe to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions.

Our significant accounting policies are more fully described in Note 2 to our consolidated financial statements included in our Annual Report on Form 10-K. No changes to those critical accounting policies have been effected during the three months ended September 30, 2005.

by us. SFAS No. 123 (revised 2004) requires such transactions to be accounted for using a fair value based method that would result in expense being recognized in our financial statements. We will be required to adopt SFAS No. 123 (revised 2004) beginning in the first quarter after December 15, 2005 and have not yet determined the impact of adoption on the consolidated financial position or results of operations.

Factors that May Affect Future Results

Factors Related to Our Business

We have a limited operating history and have incurred a cumulative loss since inception. If we do not generate significant revenues, we will not be profitable.

We have incurred significant losses since our inception in May 1998. We have not generated any revenue from the sale of products to date. We expect our annual operating losses to increase over the next several years as we expand our drug discovery, development and commercialization efforts. To become profitable, we must successfully develop and obtain regulatory approval for our product candidates and effectively manufacture, market and sell any products we develop. Accordingly, we may never generate significant revenues and, even if we do generate significant revenues, we may never achieve profitability. Our failure to become and remain profitable could depress the market price of our common stock and could impair our ability to raise capital, expand our business or continue our operations.

We will need additional capital to fund our operations, including product candidate development, manufacturing and commercialization. If we do not have or cannot raise additional capital when needed, we will be unable to develop and commercialize our product candidates successfully.

We estimate that our December 31, 2005 cash, cash equivalents and marketable securities balance will approximate $229 million to $237 million. We believe that this balance and the development expense funding by Novartis for our licensed product candidates, will be sufficient to satisfy our anticipated cash needs for at least the next 24 months. However, we may need or choose to seek additional funding within this period of time. Our drug development programs and the potential commercialization of our product candidates will require substantial additional cash to fund expenses that we will incur in connection with preclinical studies and clinical trials, regulatory review, manufacturing and sales and marketing efforts.

Our need for additional funding will depend in large part on whether:

	•		with respect to our lead HBV product candidates, Novartis continues to reimburse us for development expenses and we achieve milestones relating to the development and regulatory approval of these product candidates and receive related milestone payments from Novartis; and

	•		with respect to our HCV and other product candidates, Novartis exercises its option to license these product candidates and we receive related license fees, milestone payments and development expense reimbursement payments from Novartis.

In addition, although Novartis has agreed to pay for certain development expenses incurred under development plans it approves for our lead HBV product candidates and any other product candidates Novartis licenses from us, Novartis has the right to terminate its license and the related funding obligations with respect to any product candidate by providing us with six months’ written notice.

Our future capital needs will also depend more generally on many other factors, including:

	•		the costs of launching telbivudine and any of our other product candidates if such product candidates are approved for commercial sale by regulatory authorities;

	•		the scope and results of our preclinical studies and clinical trials;

	•		the progress of our current drug development programs for HBV, HCV and HIV;

	•		the cost of obtaining, maintaining and defending patents on our product candidates and processes;

	•		the cost of establishing arrangements for manufacturing;

	•		the cost, timing and outcome of regulatory reviews;

	•		the cost of establishing sales and marketing functions;

	•		the commercial potential of our product candidates;

	•		the rate of technological advances in our markets;

	•		the cost of acquiring or undertaking development and commercialization efforts for any additional product candidates;

	•		the magnitude of our general and administrative expenses; and

	•		any costs we may incur under current and future licensing arrangements relating to our product candidates.

We estimate that we will incur significant costs to complete and file our NDA for telbivudine and to complete the clinical trials and other studies required to enable us to file NDAs with the FDA for valtorcitabine and valopicitabine, or NM283, our HCV product candidate, assuming we continue our development of each of these product candidates. The time and cost to complete clinical development of these product candidates may vary as a result of a number of factors.

We may seek additional capital through a combination of public and private equity offerings, debt financings and collaborative, strategic alliance and licensing arrangements. Such additional financing may not be available when we need it or may not be available on terms that are favorable to us.

If we raise additional capital through the sale of our common stock, existing stockholders will be diluted and the terms of the financing may adversely affect the holdings or rights of our stockholders. If we are unable to obtain adequate financing on a timely basis, we could be required to delay, reduce or eliminate one or more of our drug development programs or to enter into new collaborative, strategic alliance or licensing arrangements that may not be favorable to us. These arrangements could result in the transfer to third parties of rights that we consider valuable.

We will not be able to commercialize our drug products successfully if we are unable to hire and train qualified sales personnel to develop a direct sales force.

Our product candidates are under development and we are starting to recruit sales personnel to establish a direct sales force for the markets in which we will co-promote or co-market drugs we successfully develop and for which we receive regulatory approval. Due to the promotion, marketing and sale of competitive and potentially competitive products within specialized markets by companies that have significantly greater resources and existing commercialization infrastructures, we believe that it may be difficult to recruit qualified personnel with experience in sales and marketing of viral and other infectious disease therapeutics. As a result, we may not be able to successfully hire and train qualified sales personnel to establish a direct sales force. We expect to incur significant expense in establishing and expanding our sales force and we may incur a substantial amount of these costs before our product candidates have been approved for marketing.

Our market is subject to intense competition. If we are unable to compete effectively, our product candidates may be rendered noncompetitive or obsolete.

We are engaged in segments of the pharmaceutical industry that are highly competitive and rapidly changing. Many large pharmaceutical and biotechnology companies, academic institutions, governmental agencies and other public and private research organizations are pursuing the development of novel drugs that target viral diseases, including the same diseases we are targeting. We face, and expect to continue to face, intense and increasing competition as new products enter the market and advanced technologies become available. For example, we are aware that entecavir, a nucleoside analog, has recently been approved by the FDA for the treatment of hepatitis B infection and has been commercially launched in the

United States. In addition, we believe that a significant number of drugs, currently under development, may become available in the future for the treatment of hepatitis B, hepatitis C and HIV infections. If any of these product candidates are successfully developed, they may be marketed before our product candidates. Our competitors’ products may be more effective, or better marketed and sold, than any of our products. Many of our competitors have:

	•		significantly greater financial, technical and human resources than we have and may be better equipped to discover, develop, manufacture and commercialize products;

	•		more extensive experience in preclinical studies and clinical trials, obtaining regulatory approvals and manufacturing and marketing pharmaceutical products;

	•		products that have been approved or are in late stage development; and

	•		collaborative arrangements in our target markets with leading companies and research institutions.

Under certain circumstances, Novartis has the right to compete with product candidates and drugs developed or licensed by us. Novartis has the right under certain circumstances to market and sell products that compete with the product candidates and products that we license to it, and any competition by Novartis could have a material adverse effect on our business.

Competitive products may render our products obsolete or noncompetitive before we can recover the expenses of developing and commercializing our product candidates. Furthermore, the development of new treatment methods and/or the widespread adoption or increased utilization of vaccines for the diseases we are targeting could render our product candidates noncompetitive, obsolete or uneconomical.

If we successfully develop and obtain approval for our product candidates, we will face competition based on the safety and effectiveness of our products, the timing and scope of regulatory approvals, the availability and cost of supply, marketing and sales capabilities, reimbursement coverage, price, patent position and other factors. Our competitors may develop or commercialize more effective or more affordable products, or obtain more effective patent protection, than we do. Accordingly, our competitors may commercialize products more rapidly or effectively than we do, which could adversely affect our competitive position and business.

Biotechnology and related pharmaceutical technologies have undergone and continue to be subject to rapid and significant change. Our future will depend in large part on our ability to maintain a competitive position with respect to these technologies.

If we successfully develop products but those products do not achieve and maintain market acceptance, our business will not be successful.

Even if our product candidates are successfully developed, our success and growth will depend upon the acceptance of these candidates by physicians, healthcare professionals and third-party payers. Acceptance will be a function of our products being clinically useful and demonstrating superior therapeutic effect with an acceptable side effect profile as compared to existing or future treatments. Lamivudine, adefovir dipivoxil and entecavir are small molecule therapeutics currently approved for the treatment of chronic hepatitis B. The current standard of care for the treatment of chronic hepatitis C is the combination of pegylated interferon and ribavirin. We are aware that a significant number of product candidates are currently under development and may become available in the future for the treatment of hepatitis B, hepatitis C and HIV infections. If our products do not achieve market acceptance, then we will not be able to generate sufficient revenue from product sales to maintain or grow our business. In addition, even if product candidates we successfully develop achieve market acceptance, we may not be able to maintain that market acceptance over time if:

	•		new products or technologies are introduced that are more favorably received than our products or render our products obsolete; or

	•		complications, such as unacceptable levels of viral resistance or adverse side effects, arise with respect to use of our products.

Our research and development efforts may not result in additional product candidates being discovered, which could limit our ability to generate revenues.

Our research and development programs, other than our programs for telbivudine, valtorcitabine and valopicitabine, are at preclinical stages. Additional product candidates that we may develop will require significant research, development, preclinical studies and clinical trials, regulatory approval and commitment of resources before commercialization. We cannot predict whether our research will lead to the discovery of product candidates that could generate revenues for us.

As we evolve from a company primarily involved in discovery and development to one also involved in commercialization, we may encounter difficulties in managing our growth and expanding our operations successfully.

We have experienced a period of rapid and substantial growth that has placed a strain on our administrative and operational infrastructure, and we anticipate that our continued growth will have a similar impact. As we advance our product candidates through clinical trials and regulatory approval processes and initiate our preparations for the commercial launch of telbivudine, we are expanding our development, regulatory, manufacturing, marketing and sales capabilities and may contract with third parties to provide these capabilities for us. Such expansion of capabilities is requiring us to invest substantial cash and management resources. If the development or commercialization of any of our product candidates is delayed or terminated, we will have incurred significant unrecoverable costs in connection with the expansion of our administrative and operational capabilities at a time earlier than necessary, if necessary at all.

As our operations expand, we expect that we will need to manage additional relationships with various collaborative partners, suppliers and other third parties. Our ability to manage our operations and growth requires us to continue to improve our operational, financial and management controls, reporting systems and procedures. We may not be able to implement improvements to our management information and control systems in an efficient or timely manner and may discover deficiencies in existing systems and controls that could expose us to an increased risk of incurring financial or accounting irregularities or fraud.

If we are not able to attract and retain key management and scientific personnel and advisors, we may not successfully develop our product candidates or achieve our other business objectives.

We highly depend upon our senior management and scientific staff. The loss of the service of any of the key members of our senior management may significantly delay or prevent the achievement of product development and other business objectives. Our ability to attract and retain qualified personnel, consultants and advisors is critical to our success. We face intense competition for qualified individuals from numerous pharmaceutical and biotechnology companies, universities, governmental entities and other research institutions. We may be unable to attract and retain these individuals, and our failure to do so would have an adverse effect on our business.

Our business has a substantial risk of product liability claims. If we are unable to obtain appropriate levels of insurance, a product liability claim against us could adversely affect our business.

Our business exposes us to significant potential product liability risks that are inherent in the development, manufacturing and marketing of human therapeutic products. Product liability claims could result in a recall of products or a change in the indications for which such products may be used. Although we do not currently commercialize any products, product liability claims could be made against us based on the use of our product candidates in clinical trials. We currently have clinical trial insurance and will seek to obtain product liability insurance prior to marketing any of our product candidates. Our insurance may not provide adequate coverage against potential liabilities. Furthermore, clinical trial and product liability insurance is becoming increasingly expensive. As a result, we may be unable to maintain current amounts of insurance coverage, obtain additional insurance or obtain sufficient insurance at a reasonable cost to protect against losses that could have a material adverse effect on us.

If the estimates we make, and the assumptions on which we rely, in preparing our financial statements prove inaccurate, our actual results may vary from those reflected in our projections and accruals.

Our financial statements have been prepared in accordance with accounting principles generally accepted in the United States. The preparation of these financial statements requires us to make estimates and judgments that affect the reported amounts of our assets, liabilities, revenues and expenses, the amounts of charges accrued by us and related disclosure of contingent assets and liabilities. We base our estimates on historical experience and on various other assumptions that we believe to be reasonable under the circumstances. There can be no assurance, however, that our estimates, or the assumptions underlying them, will not change. For example, we are recognizing the license fee and other upfront payments under our development agreement with Novartis over a development period that we have set. If the estimated performance period changes, we will adjust the periodic revenue that is being recognized and will record the remaining unrecognized license fee and other up-front payments over the remaining development period during which our performance obligations will be completed. Significant judgments and estimates are involved in determining the estimated development period and different assumptions could yield materially different results. This, in turn, could adversely affect our stock price.

We face costs and risks associated with compliance with Section 404 of the Sarbanes-Oxley Act.

Currently, we are evaluating our internal control systems in order to allow our management to report on, and our independent registered public accounting firm to audit and express an opinion on, our internal controls over financial reporting, as required by Section 404 of the Sarbanes-Oxley Act. As a result, we are incurring additional expenses and a diversion of management’s time. While we anticipate completion of testing and evaluation of our internal controls over financial reporting with respect to the requirements of Section 404 of the Sarbanes-Oxley Act in a timely fashion, there can be no assurance that we will be able to realize this result. Our evaluation may also reveal material weaknesses or other shortcomings in our internal controls that will require us to implement new and potentially costly additional controls. If we determine that there is a material weakness in our internal controls, we will be obligated to make public disclosure of the determination. If we are not able to implement the requirements of Section 404 in a timely manner or with adequate compliance, we might be subject to investigation by regulatory authorities or be required to defer necessary reporting. Any such action could adversely affect the market price of our common stock.

Factors Related to Development, Clinical Testing and Regulatory Approval of our Product Candidates

All of our product candidates are still in development and remain subject to clinical testing and regulatory approval. If we are unable to successfully develop and test our product candidates, we will not be successful.

To date, we have not marketed, distributed or sold any products. The success of our business depends primarily upon our ability to develop and commercialize our product candidates successfully. Our most advanced product candidates are telbivudine, valtorcitabine and valopicitabine. Currently, we are conducting phase III clinical trials of telbivudine and phase IIb clinical trials of both valopicitabine and the combination of valtorcitabine and telbivudine. Our other product candidates are in various earlier stages of development. Our product candidates must satisfy rigorous standards of safety and efficacy before they can be approved for sale. Safety standards include an assessment of the toxicology and carcinogenicity of the product candidates we are developing. To satisfy these standards, we must engage in expensive and lengthy testing and obtain regulatory approval of our product candidates. As a result of efforts to satisfy these regulatory standards, our product candidates may not:

	•		offer therapeutic or other improvements over existing comparable drugs;

	•		be proven safe and effective in clinical trials;

	•		meet applicable regulatory standards;

	•		be capable of being produced in commercial quantities at acceptable costs; or

	•		be successfully commercialized.

Commercial availability of our product candidates is dependent upon successful clinical development and receipt of requisite regulatory approvals.

Based on the results from the first year of our ongoing phase III pivotal clinical trial for the use of telbivudine for the treatment of HBV infection, we and Novartis are planning to file an NDA with the FDA. The data from our phase III trial of telbivudine appear to be positive; however, new information may arise from our continuing analysis of the data that may be less favorable than currently anticipated. Clinical data often are susceptible to varying interpretations. Many companies that have believed that their products performed satisfactorily in clinical trials in terms of both safety and efficacy have nonetheless failed to obtain FDA approval for those products. We do not anticipate submitting the first applications for such regulatory approval for telbivudine prior to the end of 2005. Furthermore, even after we complete the submission, the FDA may not accept our submission as complete, may request additional information from us, including data from additional clinical trials, and ultimately may not grant marketing approval for telbivudine.

If our clinical trials are not successful, we will not obtain regulatory approval for commercial sale of our product candidates.

To obtain regulatory approval for the commercial sale of our product candidates, we will be required to demonstrate through preclinical studies and clinical trials that our product candidates are safe and effective. Preclinical studies and clinical trials are lengthy and expensive and the historical rate of failure for product candidates is high. The results from preclinical studies of a product candidate may not predict the results that will be obtained in human clinical trials.

We, the FDA or other applicable regulatory authorities may suspend clinical trials of a product candidate at any time if we or they believe the persons participating in such clinical trials are being exposed to unacceptable health risks or for other reasons. Among other things, adverse side effects of a product candidate on persons in a clinical trial could result in the FDA or foreign regulatory authorities refusing to approve a particular product candidate for any or all indications of use.

Clinical trials require sufficient patient enrollment, which is a function of many factors, including the size of the patient population, the nature of the protocol, the proximity of patients to clinical sites, the availability of effective treatments for the relevant disease and the eligibility criteria for the clinical trial. Delays in patient enrollment can result in increased costs and longer development times.

We cannot predict whether we will encounter problems with any of our completed, ongoing or planned clinical trials that will cause us or regulatory authorities to delay or suspend our clinical trials, or delay the analysis of data from our completed or ongoing clinical trials.

Any of the following could delay the completion of our ongoing and planned clinical trials:

	•		discussions with the FDA or comparable foreign authorities regarding the scope or design of our clinical trials;

	•		delays or the inability to obtain required approvals from, or suspensions or terminations by, institutional review boards or other governing entities at clinical sites selected for participation in our clinical trials;

	•		delays in enrolling patients and volunteers into clinical trials;

	•		lower than anticipated retention rate of patients and volunteers in clinical trials;

	•		negative results of clinical trials;

	•		insufficient supply or deficient quality of product candidate materials or other materials necessary to conduct our clinical trials; or

•

serious or unexpected drug-related side effects experienced by participants in our clinical trials.

If the results of our ongoing or planned clinical trials for our product candidates are not available when we expect or if we encounter any delay in the analysis of data from our preclinical studies and clinical trials:

	•		we may be unable to complete phase III clinical trials of telbivudine or submit an NDA for telbivudine;

	•		we may be unable to advance the clinical development of valtorcitabine and/or valopicitabine;

	•		we may be unable to commence human clinical trials of our other HCV product candidates, our HIV product candidates or other product candidates, if any;

	•		Novartis may choose not to license our product candidates other than telbivudine and valtorcitabine, and we may not be able to enter into other collaborative arrangements for any of our other product candidates; or

	•		we may not have the financial resources to continue research and development of our product candidates.

If we are unable to obtain U.S. and/or foreign regulatory approval, we will be unable to commercialize our product candidates.

Our product candidates are subject to extensive governmental regulations relating to development, clinical trials, manufacturing and commercialization. Rigorous preclinical studies and clinical trials and an extensive regulatory approval process are required in the U.S. and in many foreign jurisdictions prior to the commercial sale of our product candidates. Before any product candidate can be approved for sale, we must demonstrate that it can be manufactured in accordance with the FDA’s current good manufacturing practices, which is a rigorous set of requirements. In addition, facilities manufacturing our product candidate must pass FDA inspection prior to approval. Satisfaction of these and other regulatory requirements is costly, time consuming, uncertain and subject to unanticipated delays. It is possible that none of the product candidates we are developing will obtain the appropriate regulatory approvals necessary to permit commercial distribution.

We have limited experience in conducting and managing the clinical trials necessary to obtain regulatory approvals, including approval by the FDA. The time required for FDA and other approvals is uncertain and typically takes a number of years, depending upon the complexity of the product candidate. Our analysis of data obtained from preclinical studies and clinical trials is subject to confirmation and interpretation by regulatory authorities, which could delay, limit or prevent regulatory approval. We may also encounter unanticipated delays or increased costs due to government regulation from future legislation or administrative action, changes in FDA policy during the period of product development, clinical trials and FDA regulatory review.

Any delay in obtaining or failure to obtain required approvals could materially adversely affect our ability to generate revenues from a particular product candidate. Furthermore, any regulatory approval to market a product may be subject to limitations on the indicated uses for which we may market the product. These restrictions may limit the size of the market for the product. Additionally, product candidates we successfully develop could be subject to post market surveillance and testing.

We are also subject to numerous foreign regulatory requirements governing the conduct of clinical trials, manufacturing and marketing authorization, pricing and third party reimbursement. The foreign regulatory approval process includes all of the risks associated with FDA approval described above as well as risks attributable to the satisfaction of local regulations in foreign jurisdictions. Approval by the FDA does not assure approval by regulatory authorities outside the U.S. Many foreign regulatory authorities, including those in major markets such as China, have different approval procedures than those required by the FDA and may impose additional testing requirements for our product candidates.

Even if we obtain regulatory approvals, our product candidates will be subject to ongoing regulatory review. If we fail to comply with applicable U.S. and foreign regulations, we could lose those approvals and our business would be seriously harmed.

Approvals of our product candidates are subject to continuing regulatory review, including the review of clinical results, which are reported after our product candidates become commercially available. The manufacturer, and the manufacturing facilities we use to make any of our product candidates, will be subject to periodic review and inspection by the FDA. The subsequent discovery of previously unknown problems with the product, manufacturer or facility may result in restrictions on the drug or manufacturer or facility, including withdrawal of the drug from the market. We do not have, and currently do not intend to develop, the ability to manufacture material for our clinical trials or at commercial scale. Reliance on third-party manufacturers entails risks to which we would not be subject if we manufactured products ourselves, including reliance on the third-party manufacturer for regulatory compliance.

If we fail to comply with applicable continuing regulatory requirements, we may be subject to civil penalties, suspension or withdrawal of regulatory approval, product recalls and seizures, injunctions, operating restrictions and criminal prosecutions and penalties. Because of these potential sanctions, we seek to monitor compliance with these regulations.

If we are subject to unfavorable pricing regulations, third-party reimbursement practices or healthcare reform initiatives, our business may be harmed.

The regulations governing drug product licensing, pricing and reimbursement vary widely from country to country. Some countries require approval of the sale price of a drug before it can be marketed. In many countries, the pricing review period begins after product licensing approval is granted. In some foreign markets, prescription pharmaceutical pricing remains subject to continuing governmental control even after initial approval is granted. As a result, we may obtain regulatory approval for a product in a particular country, but then be subject to price regulations, which may delay the commercial launch of the product and may negatively impact the revenues we are able to derive from sales by us or Novartis of the product in that country.

Successful commercialization of our products will also depend in part on the extent to which reimbursement for our products and related treatments will be available from government health administration authorities, private health insurers and other organizations. If we succeed in bringing one or more products to the market, these products may not be considered cost effective and reimbursement to the patient may not be available or sufficient to allow us to sell our products on a competitive basis. Because our product candidates are in the development stage, we are unable at this time to determine the cost effectiveness of these product candidates. We may need to conduct expensive pharmacoeconomic studies to demonstrate to third party payors the cost effectiveness of our product candidates. Sales of prescription drugs depend on the availability and level of reimbursement to the consumer from third-party payers, such as government and private insurance plans. These third-party payers frequently require that drug companies provide them with predetermined discounts from list prices, and third-party payers are increasingly challenging the prices charged for medical products. Because our product candidates are in the development stage, we do not know the level of reimbursement, if any, we will receive for products successfully developed. If the reimbursement we receive for any of our products is inadequate in light of our development and other costs, our profitability could be adversely affected.

We believe that the efforts of governments and third-party payers to contain or reduce the cost of healthcare will continue to affect the business and financial condition of pharmaceutical and biopharmaceutical companies. A number of legislative and regulatory proposals to change the healthcare system in the U.S. and other major healthcare markets have been proposed in recent years. These proposals have resulted in prescription drug benefit legislation being enacted in the U.S. and healthcare reform legislation being enacted by certain states. Further federal and state legislative and regulatory developments are possible and we expect ongoing initiatives in the U.S. to increase pressure on drug pricing. Such reforms could have an adverse effect on anticipated revenues from product candidates that we may successfully develop.

If we do not comply with laws regulating the protection of the environment and health and human safety, our business could be adversely affected.

Our research and development activities involve the controlled use of hazardous materials, chemicals and various radioactive compounds. Although we believe that our safety procedures for handling and disposing of these materials comply with the standards prescribed by state and federal laws and regulations, the risk of accidental contamination or injury from these materials cannot be eliminated. If an accident occurs, we could be held liable for resulting damages, which could be substantial. We are also subject to numerous environmental, health and workplace safety laws and regulations, including those governing laboratory procedures, exposure to blood-borne pathogens and the handling of biohazardous materials. Although we maintain workers’ compensation insurance to cover us for costs we may incur due to injuries to our employees resulting from the use of these materials, this insurance may not provide adequate coverage against potential liabilities. We do not maintain insurance for environmental liability or toxic tort claims that may be asserted against us. Additional federal, state, foreign and local laws and regulations affecting our operations may be adopted in the future. We may incur substantial costs to comply with, and substantial fines or penalties if we violate, any of these laws or regulations.

Factors Related to Our Relationship with Novartis

Novartis has substantial control over us and could delay or prevent a change in corporate control.

Novartis presently owns approximately 56% of our outstanding common stock. For so long as Novartis owns at least a majority of our outstanding common stock, in addition to its contractual approval rights, Novartis has the ability to delay or prevent a change in control of Idenix that may be favored by other stockholders and otherwise exercise substantial control over all corporate actions requiring stockholder approval irrespective of how our other stockholders may vote, including:

• the election of directors;

• any amendment of our restated certificate of incorporation or amended and restated by-laws;

• the approval of mergers and other significant corporate transactions, including a sale of substantially all of our assets; or

• the defeat of any non-negotiated takeover attempt that might otherwise benefit our other stockholders.

Novartis has the right to exercise control over corporate actions that may not require stockholder approval as long as it holds at least 19.4% of our voting stock.

As long as Novartis and its affiliates own at least 19.4% of our voting stock, which we define below, we cannot take certain actions without the consent of Novartis. These actions include:

	•		the authorization or issuance of additional shares of our capital stock or the capital stock of our subsidiaries, except for a limited number of specified issuances;

	•		any change or modification to the structure of our Board of Directors or a similar governing body of any of our subsidiaries;

	•		any amendment or modification to any of our organizational documents or those of our subsidiaries;

	•		the adoption of a three-year strategic plan;

	•		the adoption of an annual operating plan and budget, if there is no approved strategic plan;

	•		any decision that would result in a variance of total annual expenditure, capital or expense, in excess of 20% from the approved three-year strategic plan;

	•		any decision that would result in a variance in excess of the greater of $10 million or 20% of our

			profit or loss target in the strategic plan or annual operating plan;

	•		the acquisition of stock or assets of another entity that exceeds 10% of our consolidated net revenue, net income or net assets;

	•		the sale, lease, license or other disposition of any assets or business which exceeds 10% of our net revenue, net income or net assets;

	•		the incurrence of any indebtedness by us or our subsidiaries for borrowed money in excess of $2 million;

	•		any material change in the nature of our business or that of any of our subsidiaries;

	•		any change in control of Idenix or any subsidiary; and

	•		any dissolution or liquidation of Idenix or any subsidiary, or the commencement by us or any subsidiary of any action under applicable bankruptcy, insolvency, reorganization or liquidation laws.

Pursuant to the amended and restated stockholders’ agreement, dated July 27, 2004, among us Novartis and certain of our stockholders, which we refer to as the stockholders’ agreement, we are obligated to use our reasonable best efforts to nominate for election as a director at least two designees of Novartis for so long as Novartis and its affiliates own at least 35% of our voting stock and at least one designee of Novartis for so long as Novartis and its affiliates own at least 19.4% of our voting stock.

Additionally, until such time as Novartis and its affiliates own less than 50% of our voting stock, Novartis’ consent is required for the selection and appointment of our chief financial officer. If in Novartis’ reasonable judgment our chief financial officer is not satisfactorily performing his duties, we are required to terminate the employment of our chief financial officer.

Furthermore, under the terms of the stock purchase agreement, dated as of March 21, 2003, among us, Novartis and substantially all of our then existing stockholders, which we refer to as the stock purchase agreement, Novartis is required to make future contingent payments of up to $357 million to these stockholders if we achieve predetermined development milestones with respect to an HCV product candidate. As a result, in making determinations as to our annual operating plan and budget for the development of our HCV product candidates, the interests of Novartis may be different than the interests of our other stockholders, and Novartis could exercise its approval rights in a manner that may not be in the best interests of all of our stockholders.

Under the stockholders’ agreement, voting stock means our outstanding securities entitled to vote in the election of directors, but does not include:

	•		securities issued in connection with our acquisition of all of the capital stock or all or substantially all of the assets of another entity; and

	•		shares of common stock issued upon exercise of stock options or stock awards pursuant to compensation and equity incentive plans. Notwithstanding the foregoing, voting stock includes up to 1,399,106 shares that were reserved as of May 8, 2003 for issuance under our 1998 Equity Incentive Plan.

Novartis has the ability to exercise substantial control over our strategic direction, our research and development focus and other material business decisions.

We currently depend on one collaboration partner, Novartis, for substantially all our revenues and for commercialization of our HBV product candidates, and we may depend on Novartis for commercialization of other product candidates. If our development, license and commercialization agreement with Novartis terminates, our business and, in particular, our drug development programs, pill be seriously harmed.

In May 2003, we received a $75 million license fee from Novartis in connection with the license of our HBV product candidates, telbivudine and valtorcitabine, under a development, license and commercialization agreement with Novartis, dated May 8, 2003, which we refer to as the development agreement. Assuming we continue to successfully develop and commercialize these product candidates, we are entitled to receive reimbursements of expenses we incur in connection with the development of these product candidates and additional milestone payments from Novartis. In June 2004, we received a milestone payment from Novartis in the amount of $25 million based upon the results achieved in the phase I clinical trial of valopicitabine, our lead HCV product candidate. Novartis has the option to license valopicitabine and additional product candidates from us. If it does so, we are entitled to receive additional license fees and milestone payments as well as reimbursement of expenses we incur in the development of such product candidates in accordance with development plans mutually agreed with Novartis. We expect that we will derive substantially all of our near term revenues from Novartis. Novartis may terminate the development agreement in any country or with respect to any product or product candidate licensed under the development agreement for any reason on six months’ written notice. If the development agreement is terminated in whole or in part and we are unable to enter similar arrangements with other collaborators, our business would be materially adversely affected.

Novartis has the option to license our product candidates, and if it does not exercise its option with respect to a product candidate, our development, manufacture and/or commercialization of such product candidate may be substantially delayed or limited.

In addition to its license of telbivudine and valtorcitabine, Novartis has the option under the development agreement to license our other product candidates, including valopicitabine, our lead product candidate for the treatment of hepatitis C infection. Our drug development programs and potential commercialization of our product candidates will require substantial additional funding. If we are not successful in efforts to enter into a collaboration arrangement with respect to a product candidate not licensed by Novartis, we may not have sufficient funds to develop such product candidate internally. As a result, our business would be adversely affected. In addition, the negotiation of a collaborative agreement is time consuming, and could, even if successful, delay the development, manufacture and/or commercialization of a product candidate and the terms of the collaboration agreements may not be favorable to us.

If we breach any of the numerous representations and warranties we made to Novartis under the development agreement or the stock purchase agreement, Novartis has the right to seek indemnification from us for damages it suffers as result of such breach. These amounts could be substantial.

We have agreed to indemnify Novartis and its affiliates against losses suffered as a result of our breach of representations and warranties in the development agreement and the stock purchase agreement. Under the development agreement and stock purchase agreement, we made numerous representations and warranties to Novartis regarding our hepatitis C and hepatitis B product candidates, including representations regarding our ownership of and licensed rights to the inventions and discoveries relating to such product candidates. If one or more of our representations or warranties were not true at the time we made them to Novartis, we would be in breach of these agreements. In the event of a breach by us, Novartis has the right to seek indemnification from us and, under certain circumstances, us and our stockholders who sold shares to Novartis, which include many of our directors and officers, for damages suffered by Novartis as a result of such breach. The amounts for which we could become liable to Novartis may be substantial.

In May 2004, we entered into a settlement agreement with the University of Alabama at Birmingham, or UAB, and the University of Alabama Research Foundation, or UABRF, relating to our ownership of our chief executive officer’s inventorship interest in certain of our patents and patent applications, including patent applications covering our hepatitis C product candidates. Under the terms of the settlement agreement, we agreed to make payments to UABRF, including an initial payment paid in 2004 in the amount of $2 million, as well as regulatory milestone payments and payments relating to net sales of certain products. Novartis may seek to recover from us, and, under certain circumstances, us and those of our officers, directors and other stockholders who sold shares to Novartis, the losses it suffers as a result of any breach of the representations and warranties we made relating to our hepatitis C product candidates and may assert that such losses include the settlement payments.

Novartis could also suffer losses in connection with any amounts we become obligated to pay relating to or under the terms of any license agreement, including the UAB license agreement, or other arrangements we may be required to enter into with UAB, Emory University and the Centre Nationale de la Recherché Scientifique, or CNRS, each licensors under the UAB license agreement, to commercialize telbivudine. Novartis, may seek to recover from us, and, under certain circumstances, us and those of our officers, directors and other stockholders who sold shares to Novartis, such losses and other losses it suffers as a result of any breach of the representations and warranties we made relating to our hepatitis B product candidates.

If we are required to rely upon the UAB license agreement to commercialize telbivudine, we will be obligated to make certain payments to UABRF and the other licensors. Such amounts would include payments in the aggregate amount of $1.3 million due upon achievement of regulatory milestones, a 6% royalty on annual sales up to $50 million and a 3% royalty on annual sales greater than $50 million made by us or an affiliate of ours. Additionally, if we sublicense our rights to a non-affiliate sublicensee which is defined as any entity other than one which holds or controls at least 50% of our capital stock, or if Novartis’ ownership interest in us declines below 50% of our outstanding shares of capital stock, we could be obligated to pay to UABRF 30% of all royalties received by us from sales by the sublicensee of telbivudine and 20% of all fees, milestone payments and other cash consideration we receive from the sublicensee with respect to telbivudine.

If we materially breach our obligations or covenants arising under the development agreement or our master manufacturing and supply agreement with Novartis, we may lose our right to develop or commercialize our product candidates.

We have significant obligations to Novartis under the development agreement and our master manufacturing and supply agreement, dated as of May 8, 2003, between our subsidiary, Idenix (Cayman) Limited, or Idenix Cayman, and Novartis. We refer to the master manufacturing and supply agreement as the supply agreement. The obligations to which we are subject include the responsibility for developing and, in some countries, co-promoting or co-marketing the products licensed to Novartis in accordance with plans and budgets subject to Novartis’ approval. The covenants and agreements we made when entering into the development agreement and supply agreement include covenants relating to payment of our required portion of development expenses under the development agreement, compliance with certain third-party license agreements and the conduct of our clinical studies. If we materially breach one or both of these agreements and are unable within an agreed time period to cure such breach, the agreements may be terminated and we may be required to grant Novartis an exclusive license to develop, manufacture and/or sell such products. Although such a license would be subject to payment of a royalty by Novartis to be negotiated in good faith, we and Novartis have stipulated that no such payments would permit the breaching party to receive more than 90% of the net benefit it was entitled to receive before the agreements were terminated. Accordingly, if we materially breach our obligations under the development agreement or the supply agreement, we may lose our rights to develop or commercialize our drug candidates and receive lower payments from Novartis than we had anticipated.

If we issue capital stock, in certain situations Novartis will be able to purchase shares at par value to maintain its percentage ownership in Idenix and, if that occurs, this could cause dilution. In addition, Novartis has the right, under specified circumstances, to purchase a pro rata portion of other shares that we may issue.

Under the terms of the stockholders’ agreement, Novartis has the right to purchase at par value of $0.001 per share, such number of shares required to maintain its percentage ownership of our voting stock if we issue shares of capital stock in connection with the acquisition or in-licensing of technology through the issuance of up to 5% of our stock in any 24-month period. If Novartis elects to maintain its percentage ownership of our voting stock under the rights described above, Novartis will be buying such shares at a price, which is substantially below market value, which would cause dilution. This right of Novartis will remain in effect until the earlier of:

	•		the date that Novartis and its affiliates own less than 19.4% of our voting stock; or

	•		the date that Novartis becomes obligated under the stock purchase agreement to make the additional

future contingent payments of $357 million to all of our stockholders who sold shares to Novartis in May 2003.

In addition to the right to purchase shares of our common stock at par value as described above, Novartis has the right, subject to limited exceptions noted below, to purchase a pro rata portion of shares of capital stock that we issue. The price that Novartis pays for these securities would be the price that we offer such securities to third parties, including the price paid by persons who acquire shares of our capital stock pursuant to awards granted under stock compensation plans. Novartis’ right to purchase a pro rata portion does not include:

	•		securities issuable in connection with any stock split, reverse stock split, stock dividend or recapitalization that we undertake that affects all holders of our common stock proportionately;

	•		shares that Novartis has the right to purchase at par value, as described above;

	•		shares of common stock issuable upon exercise of stock options and other awards pursuant to our 1998 Equity Incentive Plan; and

	•		securities issuable in connection with our acquisition of all the capital stock or all or substantially all of the assets of another entity.

Novartis’ right to purchase shares includes a right to purchase securities that are convertible into, or exchangeable for, our common stock, provided that Novartis’ right to purchase stock in connection with options or other convertible securities issued to any of our directors, officers, employees or consultants pursuant to any stock compensation or equity incentive plan will not be triggered until the underlying equity security has been issued to the director, officer, employee or consultant.

If Novartis terminates or fails to perform its obligations under the development agreement, we may not be able to successfully commercialize our drug products licensed to Novartis and the development and commercialization of our other product candidates could be delayed, curtailed or terminated.

Under the development agreement, we will co-promote or co-market with Novartis in the U.S., the U.K., France, Germany, Italy and Spain, our lead hepatitis B drug products and other products that Novartis licenses from us, which may include our hepatitis C drug products. Novartis will market and sell these drug products throughout the rest of the world. As a result, we will depend upon the success of the efforts of Novartis to market and sell our drug products. However, we have limited control over the resources that Novartis may devote to its commercialization efforts under the development agreement and, if Novartis does not devote sufficient time and resources to such efforts, we may not realize the potential commercial benefits of the agreement, and our results of operations may be adversely affected.

In addition, Novartis has the right to terminate the development agreement with respect to any product, product candidate or country with six months’ written notice to us. If Novartis were to breach or terminate this agreement with us, the development or commercialization of the affected product candidate or product could be delayed, curtailed or terminated because we may not have sufficient resources or capabilities, financial or otherwise, to continue development and commercialization of the product candidate, and we may not be successful in entering into a collaboration with another third party.

Novartis has the right under certain circumstances to market and sell products that compete with the product candidates and products that we license to it, and any competition by Novartis could have a material adverse effect on our business.

Novartis has agreed that, except as set forth in the development agreement, it will not market, sell or promote certain competitive products except that:

	•		this agreement not to compete extends only until May 2008;

	•		as to any country, the agreement not to compete would terminate if Novartis terminates the development agreement with respect to that country; and

•

if Novartis wishes to market, sell, promote or license a competitive product, it is required to inform us of the competitive product opportunity and, at our election, enter into good faith negotiations with us concerning such opportunity. If we either do not elect to enter into negotiations with respect to such opportunity or are unable to reach agreement within a specified period, Novartis would be free to proceed with its plans with respect to such competing product.

Accordingly, Novartis may under certain circumstances market, sell, promote or license, competitive products. Novartis has significantly greater financial, technical and human resources than we have and is better equipped to discover, develop, manufacture and commercialize products. In addition, Novartis has more extensive experience in preclinical studies and clinical trials, obtaining regulatory approvals and manufacturing and marketing pharmaceutical products. Moreover, any direct or indirect competition with Novartis with respect to products that we have licensed to them could result in confusion in the market. In the event that Novartis competes with us, our business could be materially and adversely affected.

Factors Related to Our Dependence on Third Parties

Because we have limited sales, marketing and distribution experience and capabilities, we may seek to enter into additional arrangements with third parties. We may not be successful in establishing these relationships or, if established, the relationship may not be successful.

We have limited sales, marketing and distribution capabilities. Although we intend to build an internal sales force and expand our marketing capabilities, we may seek to further augment our sales, marketing and distribution capabilities through arrangements with third parties. We may not be successful in entering into any such arrangements and, if entered into, the terms of any such arrangements may not be favorable. We cannot be assured that any third party would devote the necessary time or attention to sell, market or distribute our products. If these arrangements are unsuccessful, we may be unable to successfully commercialize our products.

If we seek to enter into collaboration agreements for any other product candidates but are not successful, we may not be able to continue development of those product candidates.

Our drug development programs and potential commercialization of our product candidates will require substantial additional cash to fund expenses to be incurred in connection with these activities. We have entered into an agreement with Novartis for the development and commercialization of telbivudine and valtorcitabine, our lead HBV product candidates, and we have granted options to Novartis with respect to development and commercialization of our other product candidates. We may seek to enter into additional collaboration agreements with pharmaceutical companies to fund all or part of the costs of drug development and commercialization of product candidates that Novartis does not license. We may not be able to enter into collaboration agreements and the terms of the collaboration agreements, if any, may not be favorable to us. If we are not successful in our efforts to enter into a collaboration arrangement with respect to a product candidate, we may not have sufficient funds to develop this or any other product candidate internally.

If we do not have sufficient funds to develop our product candidates, we will not be able to bring these product candidates to market and generate revenue. As a result, our business will be adversely affected. In addition, the inability to enter into collaboration agreements could delay or preclude the development, manufacture and/or commercialization of a product candidate and could have a material adverse effect on our financial condition and results of operations because:

	•		we may be required to expend our own funds to advance the product candidate to commercialization;

	•		revenue from product sales could be delayed; or

	•		we may elect not to develop or commercialize the product candidate.

If any collaborative partner terminates or fails to perform its obligations under agreements with us, the development and commercialization of our product candidates could be delayed or terminated.

We have entered into the development agreement with Novartis and we may enter into additional collaborative arrangements in the future. If collaborative partners do not devote sufficient time and resources to any collaboration arrangement with us, we may not realize the potential commercial benefits of the arrangement, and our results of operations may be adversely affected. In addition, if Novartis or future collaboration partners were to breach or terminate their arrangements with us, the development and commercialization of the affected product candidate could be delayed, curtailed or terminated because we may not have sufficient financial resources or capabilities to continue development and commercialization of the product candidate.

Our collaborations with outside scientists may be subject to restriction and change.

We work with chemists and biologists at academic and other institutions who assist us in our research and development efforts. Telbivudine, valtorcitabine and valopicitabine, were discovered with the research and development assistance of these third-party chemists and biologists. Many of the scientists who have contributed to the discovery and development of our product candidates are not our employees and may have other commitments that would limit their future availability to us. Although our scientific advisors and collaborators generally agree not to do competing work, if a conflict of interest between their work for us and their work for another entity arises, we may lose their services.

We depend on third-party manufacturers to manufacture products for us. If in the future we manufacture any of our products, we will be required to incur significant costs and devote significant efforts to establish these capabilities.

We have limited manufacturing experience and have the capability to manufacture only small quantities of compounds required in preclinical studies for our product candidates. We do not have, and do not intend to develop, the ability to manufacture material for our clinical trials or at commercial scale. To develop our product candidates, apply for regulatory approvals and commercialize any products, we need to contract for or otherwise arrange for the necessary manufacturing facilities and capabilities. Under the supply agreement, Novartis has agreed to manufacture or have manufactured for us the active pharmaceutical ingredients, or API, of product candidates that we license to Novartis for our clinical supply requirements. In addition, Novartis may manufacture or have manufactured for us the API for commercial supplies of these products, subject to the terms of the supply agreement. Under this agreement, if Novartis manufactures the API for a product, we would generally rely on Novartis for regulatory compliance and quality assurance for that product. Currently, we are negotiating with Novartis an agreement with respect to the anticipated manufacture by Novartis of the commercial supply of telbivudine. If we are unable to successfully conclude an agreement with Novartis for the manufacture of the telbivudine commercial supply or Novartis were to breach or terminate its manufacturing arrangements with us, the development or commercialization of telbivudine could be delayed, which would have an adverse affect on our business. In addition, any change in our manufacturers could be costly because the commercial terms of any such arrangement could be less favorable than the commercial terms we negotiate with Novartis.

We have relied upon third parties to produce material for preclinical studies and may continue to do so in the future. Although we believe that we will not have any material supply issues, we cannot be certain that we will be able to obtain long term supply arrangements of those materials on acceptable terms, if at all. We also expect to rely upon other third parties to produce materials required for clinical trials and for the commercial production of certain of our products if we succeed in obtaining necessary regulatory approvals. If we are unable to arrange for third-party manufacturing, or to do so on commercially reasonable terms, we may not be able to complete development of our products or market them.

Reliance on Novartis and third-party manufacturers entails risks to which we would not be subject if we manufactured products ourselves, including reliance on Novartis or the third party for regulatory compliance and quality assurance, the possibility of breach by Novartis or the third party of agreements related to supply because of factors beyond our control and the possibility of termination or nonrenewal of the agreement by Novartis or the third party, based on its own business priorities, at a time that is costly or damaging to us.

In addition, the FDA and other regulatory authorities require that our products be manufactured according to current good manufacturing practice regulations. Any failure by us, Novartis or our third-party manufacturers to comply with current good manufacturing practices and/or our failure to scale up our manufacturing processes could lead to a delay in, or failure to obtain, regulatory approval. In addition, such failure could be the basis for action by the FDA to withdraw approvals for product candidates previously granted to us and for other regulatory action.

We may in the future elect to manufacture certain of our products in our own manufacturing facilities. If we do so, we will require substantial additional funds and need to recruit qualified personnel in order to build or lease and operate any manufacturing facilities.

Factors Related to Patents and Licenses

If we are unable to adequately protect our patents and licenses related to our product candidates, or if we infringe the rights of others, we may not be able to successfully commercialize our product candidates.

Our success will depend in part on our ability to obtain patent protection both in the U.S. and in other countries for our product candidates. The patents and patent applications in our patent portfolio are either owned by us, exclusively licensed to us, or co-owned by us and others and exclusively licensed to us. Our ability to protect our product candidates from unauthorized or infringing use by third parties depends substantially on our ability to obtain and maintain valid and enforceable patents. Due to evolving legal standards relating to the patentability, validity and enforceability of patents covering pharmaceutical inventions and the scope of claims made under these patents, our ability to obtain and enforce patents is uncertain and involves complex legal and factual questions. Accordingly, rights under any issued patents may not provide us with sufficient protection for our product candidates or provide sufficient protection to afford us a commercial advantage against our competitors or their competitive products or processes. In addition, we cannot guarantee that any patents will be issued from any pending or future patent applications owned by or licensed to us. Even if patents have been issued or will be issued, we cannot guarantee that the claims of these patents are, or will be, valid or enforceable, or provide us with any significant protection against competitive products or otherwise be commercially valuable to us.

We may not have identified all patents, published applications or published literature that affect our business either by blocking our ability to commercialize our drugs, by preventing the patentability of our drugs to us or our licensors or co-owners, or by covering the same or similar technologies that may invalidate our patents, limit the scope of our future patent claims or adversely affect our ability to market our product candidates. For example, patent applications in the U.S. are maintained in confidence for up to 18 months after their filing. In some cases, however, patent applications remain confidential in the U.S. Patent and Trademark Office, which we refer to as the U.S. Patent Office, for the entire time prior to issuance as a U.S. patent. Patent applications filed in countries outside the U.S. are not typically published until at least 18 months from their first filing date. Similarly, publication of discoveries in the scientific or patent literature often lags behind actual discoveries. Therefore, we cannot be certain that we or our licensors or co-owners were the first to invent, or the first to file, patent applications on our product candidates or for their use as antiviral drugs. In the event that a third party has also filed a U.S. patent application covering our product candidates or a similar invention, we may have to participate in an adversarial proceeding, known as an interference, declared by the U.S. Patent Office to determine priority of invention in the U.S. The costs of these proceedings could be substantial and it is possible that our efforts could be unsuccessful, resulting in a loss of our U.S. patent position. The laws of some foreign jurisdictions do not protect intellectual property rights to the same extent as in the U.S. and many companies have encountered significant difficulties in protecting and defending such rights in foreign jurisdictions. If we encounter such difficulties in protecting or are otherwise precluded from effectively protecting our intellectual property rights in foreign jurisdictions, our business prospects could be substantially harmed. Since our hepatitis B product candidate, telbivudine, was a known compound before the filing of our patent applications covering the use of this product candidate to treat hepatitis B infection, we cannot obtain patent protection on telbivudine itself. As a result, we are limited to relying upon patents granted on the method of using telbivudine in medical therapy for the treatment of hepatitis B infection.

Our other hepatitis B product candidate, valtorcitabine, is a prodrug of the L-nucleoside ß-L-2’- deoxycytidine, or LdC, because it is converted into biologically active LdC in the body. We believe that

valtorcitabine is a new compound. The U.S. Patent Office has recently issued to us a patent on valtorcitabine itself, as well as claims on pharmaceutical compositions that include valtorcitabine. Claims to the method to treat hepatitis B infection using valtorcitabine are pending. We will not, however, be able to obtain patent protection on the biologically active form of LdC itself, because it was a known compound at the time the patent applications covering LdC were filed. Instead, our patent protection will be limited to patents covering the method of using LdC in medical therapy for the treatment of hepatitis B infection. We are aware of an issued U.S. patent with claims directed to a broad genus of compounds which may be construed to include paltorcitabine. We believe those claims to be invalid as a result of prior art in existence at the time those claims were filed. We would assert an invalidity defense against any such claims were they to be asserted against us. However, there is no assurance that these claims would be found to be invalid; in which case, we would need to obtain a license to these patent rights which may not be available on reasonable terms.

Pursuant to the UAB license agreement, we were granted an exclusive license to the rights held by UABRF, Emory University and CNRS, which we collectively refer to as “the 1998 licensors,” to a 1995 U.S. patent application and counterpart patent applications in Europe, Canada, Japan and Australia that cover the use of certain synthetic nucleosides for the treatment of hepatitis B infection. In January 2004, February 2005 and June 2005, UABRF notified us that it intended to file a U.S. continuation patent application claiming priority to the 1995 patent application, which itself is a continuation-in-part of a 1993 patent application, that would purportedly enable the 1998 licensors to prosecute and obtain generic patent claims that would generally encompass the method of using telbivudine to treat patients infected with hepatitis B. In July 2005, UABRF filed such a continuation patent application.

In connection with the 1998 licensors pursuit of such generic patent claims, we believe that UABRF may assert that the UAB license agreement covers our telbivudine technology and that we are obligated to make payments to the 1998 licensors in the amounts and manner specified in the UAB license agreement. Such amounts include payments in the aggregate amount of $1.3 million due upon achievement of regulatory milestones, a 6% royalty on annual sales up to $50 million and a 3% royalty on annual sales greater than $50 million made by us or an affiliate of ours. Additionally, if we sublicense our rights to any entity other than one which holds or controls at least 50% of our capital stock, or if Novartis’ ownership interest in us declines below 50% of our outstanding shares of capital stock, we could be obligated to pay to the 1998 licensors 30% of all royalties received by us from sales by the sublicensee of telbivudine and 20% of all fees, milestone payments and other cash consideration we receive from the sublicensee with respect to telbivudine.

As a result of presentation by the 1998 licensors of new claims in the U.S. continuation patent application filed in July 2005, and possibly under counterpart foreign patent applications, UABRF may assert a claim to 20% of the $75 million license fee we received in May 2003 in connection with the license of our hepatitis B drug candidates to Novartis. If UABRF asserts such a claim, we intend to dispute that such amount is owed. Under the terms of the UAB license agreement, the dispute would be resolved by a panel of arbitrators if we are unable to reach agreement with UABRF after a period of negotiation and mediation.

If we fail to perform our material obligations under the UAB license agreement, the agreement may be terminated or UABRF could, on its own behalf and on behalf of the other licensors, render the license to us non-exclusive. In the event UABRF is successful in terminating the license agreement as a result of a breach by us after a period of arbitration, and the 1998 licensors obtain a valid enforceable claim that generically covers the use of telbivudine to treat hepatitis B infection, it would be necessary for us to obtain another license from the 1998 licensors. Such license may not be available to us on reasonable terms, on an exclusive basis, or at all. This could materially adversely affect or preclude our ability to commercialize telbivudine.

If the 1998 licensors were instead to render the UAB license agreement to us non-exclusive, we would not be prohibited from using telbivudine to treat hepatitis B infection, but a non-exclusive license could be granted to one or more of our competitors by one or more of the 1998 licensors.

If it is determined that the UAB license agreement between us and UABRF does cover our use of telbivudine to treat hepatitis B infection, or we must otherwise rely upon a license agreement granted by the 1998 licensors to commercialize telbivudine, we may be in breach of certain of the representations and warranties we made to Novartis under the development agreement and the stock purchase agreement. Pursuant to the terms of the development agreement and the stock purchase agreement, if there is a breach

Novartis has the right to seek indemnification from us, and, under certain circumstances, us and our stockholders who sold shares to Novartis, for the losses Novartis incurs as a result of the breach. The amounts for which we could be liable to Novartis may be substantial.

Our initial hepatitis C clinical product candidate, valopicitabine, or NM283, is a prodrug of the active molecule NM 107, because it is converted into biologically active NM 107 in the body. We believe that NM283 may be a new compound, and therefore we are attempting to obtain patent protection on NM283 itself, as well as on a method to treat hepatitis C infection with NM283. NM 107 was a known compound at the time that the patent applications covering the use of this active form of NM283 to treat hepatitis C infection were filed. Thus, although we presently have two issued U.S. patents claiming methods of treatment using NM 107, one directed to treating hepatitis C infection specifically and the other directed to treating flavivirus and pestivirus infection, we cannot obtain patent protection on the compound NM 107 itself.

Despite the fact that NM 107 is a known compound, we are aware that a number of companies have recently filed patent applications attempting to cover NM 107 specifically as a compound, as well as NM283, as members of broad classes of compounds. Companies have also filed patent applications covering the use of NM 107, specifically, and NM283, generically, to treat hepatitis C infection, or infection by any member of the Flaviviridae virus family, to which hepatitis C belongs. These companies include Merck & Co., Inc. together with Isis Pharmaceuticals, Inc., Ribapharm, Inc., a wholly owned subsidiary of Valeant Pharmaceuticals International, Genelabs Technologies, Inc. and Biota, Inc., a subsidiary of Biota Holdings Ltd., or Biota. We believe that we were the first to file patent applications covering the use of these product candidates to treat hepatitis C infection. Because patents in countries outside the U.S. are awarded to the first to file a patent application covering an invention, we believe that we are entitled to patent protection in at least these countries. Notwithstanding this, a foreign country may grant patent rights covering our product candidates to one or more other companies, either because it is not aware of our patent filings or because the country does not interpret our patent filing as a bar to issuance of the other company’s patent in that country. If that occurs, we may need to challenge the third-party patent to establish our proprietary rights, and if we do not or are not successful, we will need to obtain a license that may not be available at all or on commercially reasonable terms. In the U.S., a patent is awarded to the patent applicant who was the first to invent the subject matter. The U.S. Patent Office could initiate an interference between us and Merck/ Isis, Ribapharm, Genelabs, Biota or another company to determine the priority of invention of the use of these compounds to treat hepatitis C infection. If such an interference is initiated and it is determined that we were not the first to invent the use of these compounds in methods for treating hepatitis C or other viral infection under U.S. law, we would need to obtain a license that may not be available at all or on commercially reasonable terms.

A number of companies have filed patent applications and have obtained patents covering general methods for the treatment of hepatitis B, hepatitis C and HIV infections. These patents could materially affect our ability to develop and sell our HBV and HCV product candidates, as well as other product candidates we may develop in the future. For example, we are aware that Chiron Corporation and Apath, LLC have obtained broad patents covering hepatitis C proteins, nucleic acids, diagnostics and drug screens. If we need to use these patented materials or methods to develop valopicitipine or other hepatitis C product candidates we may develop and the materials or methods fall outside certain safe harbors in the laws governing patent infringement, as recently articulated by the United States Supreme Court, we will need to buy these products from a licensee of the company authorized to sell such products or we will require a license from one or more companies, which may not be available to us on reasonable terms or at all. This could materially affect or preclude our ability to develop and sell our hepatitis C drug product.

If we find that any product candidates we are developing should be used in combination with a product covered by a patent held by another company or institution, and that a labeling instruction is required in product packaging recommending that combination, we could be accused of, or held liable for, infringement or inducement of infringement of the third-party patents covering the product recommended for co-administration with our product. In that case, we may be required to obtain a license from the other company or institution to provide the required or desired package labeling, which may not be available on commercially reasonable terms or at all.

Litigation regarding patents, patent applications and other proprietary rights may be expensive and time consuming. If we are unsuccessful in litigation concerning patents or patent applications owned or co-

owned by us or licensed to us, we may not be able to protect our products from competition or we may be precluded from selling our products. If we are involved in such litigation, it could cause delays in bringing product candidates to market and harm our ability to operate. Such litigation could take place in the United States in a federal court or in the U.S. Patent Office. The litigation could also take place in a foreign country, in either the court or the patent office of that country.

Our success will depend in part on our ability to uphold and enforce patents or patent applications owned or co-owned by us or licensed to us, which cover our product candidates. Proceedings involving our patents or patent applications could result in adverse decisions regarding:

	•		ownership of patents and patent applications;

	•		the patentability of our inventions relating to our product candidates; and/or

	•		the enforceability, validity or scope of protection offered by our patents relating to our product candidates.

Even if we are successful in these proceedings, we may incur substantial cost and divert management time and attention in pursuing these proceedings, which could have a material adverse effect on us.

In May 2004, we and our chief executive officer, Dr. Sommadossi, entered into a settlement agreement with UAB and UABRF resolving a dispute regarding ownership of inventions and discoveries made by Dr. Sommadossi during the period from November 1999 to November 2002, at which time Dr. Sommadossi was on sabbatical and then unpaid leave from his position at UAB. The patent applications we filed with respect to such inventions and discoveries include the patent applications covering our hepatitis C product candidate. Under the terms of the settlement agreement, we agreed to make a $2 million initial payment to UABRF, as well as other potential contingent payments based upon the commercial launch of products discovered or invented by Dr. Sommadossi during his sabbatical and unpaid leave. In addition, UAB and UABRF have each agreed that neither of them has any right, title or ownership interest in these inventions and discoveries. Under the development agreement and stock purchase agreement, we made numerous representations and warranties to Novartis regarding our hepatitis C product candidate and program, including representations regarding our ownership of the inventions and discoveries. If one or more of our representations or warranties were not true at the time we made them to Novartis, we would be in breach of these agreements. In the event of a breach by us, Novartis has the right to seek indemnification from us and, under certain circumstances, us and our stockholders who sold shares to Novartis, which include many of our directors and officers, for damages suffered by Novartis as a result of such breach. The amounts for which we could be liable to Novartis may be substantial.

Our success will also depend in part on our ability to avoid infringement of the patent rights of others. If it is determined that we do infringe a patent right of another, we may be required to seek a license, defend an infringement action or challenge the validity of the patents in court. Patent litigation is costly and time consuming. We may not have sufficient resources to bring these actions to a successful conclusion. In addition, if we are not successful in infringement litigation and we do not license or develop non-infringing technology, we may:

	•		incur substantial monetary damages;

	•		encounter significant delays in bringing our product candidates to market; and/or

	•		be precluded from participating in the manufacture, use, importation, offer for sale or sale of our product candidates or methods of treatment requiring licenses.

Confidentiality agreements with employees and others may not adequately prevent disclosure of trade secrets and other proprietary information.

To protect our proprietary technology and processes, we also rely in part on confidentiality agreements with our corporate partners, employees, consultants, outside scientific collaborators, sponsored researchers and other advisors. These agreements may not effectively prevent disclosure of confidential information

and may not provide an adequate remedy in the event of unauthorized disclosure of confidential information. In addition, others may independently discover our trade secrets and proprietary information, and in such cases we could not assert any trade secret rights against such parties. Costly and time-consuming litigation could be necessary to enforce and determine the scope of our proprietary rights, and failure to obtain or maintain trade secret protection could adversely affect our competitive business position.

If any of our agreements that grant us the exclusive right to make, use and sell our product candidates are terminated, we may be unable to develop or commercialize our product candidates.

We, together with Novartis, have entered into an amended and restated agreement with CNRS and L’Universite Montpellier II, which we refer to as University of Montpellier, co-owners of the patent applications covering our hepatitis B product candidates. This agreement covers both the cooperative research program and the terms of our exclusive right to exploit the results of the cooperative research, including our hepatitis B product candidates. We, together with Novartis, have also entered into two agreements with the Universita degli Studi di Cagliari, which we refer to as the University of Cagliari, the co-owner of the patent applications covering our hepatitis C product candidates and certain of our HCV and NNRTI HIV pre-clinical product candidates. One agreement with the University of Cagliari covers our cooperative research program and the other agreement is an exclusive license to develop and sell the jointly created HCV and HIV product candidates. Under the amended and restated agreement with CNRS and the University of Montpellier and the license agreement, as amended, with the University of Cagliari, we obtained from our co-owners the exclusive right to exploit these product candidates. Subject to certain rights afforded to Novartis, these agreements can be terminated by either party in circumstances such as the occurrence of an uncured breach by the non-terminating party. The termination of our rights under the agreement with CNRS and the University of Montpellier or the license agreement, as amended, with the University of Cagliari would have a material adverse effect on our business and could prevent us from developing a product candidate or selling a product. In addition, these agreements provide that we pay the costs of patent prosecution, maintenance and enforcement. These costs could be substantial. Our inability or failure to pay these costs could result in the termination of the agreements or certain rights under them.

Under our amended and restated agreement with CNRS and the University of Montpellier and our license agreement, as amended, with the University of Cagliari, we and Novartis have the right to exploit and license our co-owned product candidates without the permission of the co-owners. However, our agreements with CNRS and the University of Montpellier and with the University of Cagliari are currently governed by, and will be interpreted and enforced under, French and Italian law, respectively, which are different in substantial respects from U.S. law, and which may be unfavorable to us in material respects. Under French law, co-owners of intellectual property cannot exploit, assign or license their individual rights without the permission of the co-owners. Similarly, under Italian law, co-owners of intellectual property can not exploit or license their individual rights without the permission of the co-owners. Accordingly, if our agreements with the University of Cagliari terminate, we may not be able to exploit, license or otherwise convey to Novartis or other third parties our rights in our drug candidates for a desired commercial purpose without the consent of the co-owner, which could materially affect our business and prevent us from developing our product candidates and selling our products.

Under U.S. law, a co-owner has the right to prevent the other co-owner from suing infringers by refusing to join voluntarily in a suit to enforce a patent. Our amended and restated agreement with CNRS and the University of Montpellier and our license agreement, as amended, with the University of Cagliari provide that such parties will cooperate to enforce our jointly owned patents on our product candidates. If these agreements terminate or their cooperation is not given or is withdrawn, or they refuse to join in litigation that requires their participation, we may not be able to enforce these patent rights or protect our markets.

If our cooperative research agreement with the University of Cagliari is terminated, we may be unable to develop research results arising out of that work prior to the termination.

Our cooperative research agreement with the University of Cagliari, as amended, grants us the exclusive right to directly or indirectly use or license to Novartis or other third parties the results of research obtained from the cooperative effort, in exchange for a fixed royalty. If the cooperative research agreement is terminated, our exclusive right to use the research results will also terminate, unless those

rights are also granted under a separate license agreement, as has been done with respect to the patent applications covering our HCV lead product candidate and HCV pre-clinical product candidates and the classes of compounds we are evaluating for selection of NNRTI HIV product candidate. Our cooperative agreement with the University of Cagliari currently expires in January 2007, and can only be renewed by the written consent of both parties. If the agreement is not renewed, there is no guarantee that the University of Cagliari will agree to transfer rights to any of the research results into a separate license agreement on termination of the research program, or that it will agree to do so on reasonable commercial terms. If we are not able to obtain a license to research results in the event of a termination of the cooperative research agreement, we will be unable to develop the research results.

Factors Related to Our Common Stock

Sales of additional shares of our common stock could cause the price of our common stock to decline.

Sales of substantial amounts of our common stock in the public market, or the availability of such shares for sale, could adversely affect the price of our common stock. In addition, the issuance of common stock upon exercise of outstanding options could be dilutive, and may cause the market price for a share of our common stock to decline. As of October 31, 2005, we had 55,632,622 shares of common stock issued and outstanding, together with outstanding options to purchase approximately 3,718,764 shares of common stock with a weighted average exercise price of $11.61 per share.

The holders of approximately 33,282,034 shares of common stock have rights, subject to certain conditions, to require us to file registration statements covering their shares or to include their shares in registration statements that we may file for ourselves or other stockholders.

Fluctuation of our quarterly results may cause our stock price to decline, resulting in losses to you.

Our quarterly operating results have fluctuated in the past and are likely to fluctuate in the future. A number of factors, many of which are not within our control, could subject our operating results and stock price to volatility, including:

	•		realization of license fees and achievement of milestones under our development agreement with Novartis and, to the extent applicable, other licensing and collaborative agreements;

	•		reductions in revenue associated with Novartis’ right to maintain its percentage ownership of our voting stock when we issue shares at a price below fair market value;

	•		the results of ongoing and planned clinical trials of our product candidates;

	•		the results of regulatory reviews relating to the approval of our product candidates;

	•		the initiation or conclusion of litigation to enforce or defend any of our assets; and

	•		general and industry-specific economic conditions that may affect our research and development expenditures.

Due to the possibility of significant fluctuations, we do not believe that quarterly comparisons of our operating results will necessarily be indicative of our future operating performance. If our quarterly operating results fail to meet the expectations of stock market analysts and investors, the price of our common stock may decline, resulting in losses to you.

An investment in our common stock may decline in value as a result of announcements of business developments by us or our competitors.

The market price of our common stock is subject to substantial volatility as a result of announcements by us or other companies in our industry. As a result, purchasers of our common stock may not be able to sell their shares of common stock at or above the price at which they purchased such stock. Announcements which may subject the price of our common stock to substantial volatility include announcements regarding:

	•		our collaboration with Novartis;

	•		the results of discovery, preclinical studies and clinical trials by us or our competitors;

	•		the acquisition of technologies, product candidates or products by us or our competitors;

	•		the development of new technologies, product candidates or products by us or our competitors;

	•		regulatory actions with respect to our product candidates or products or those of our competitors;

	•		the initiation or conclusion of litigation to enforce or defend any of our assets; and

	•		significant acquisitions, strategic partnerships, joint ventures or capital commitments by us or our competitors.

We could be subject to class action litigation due to stock price volatility, which, if it occurs, will distract our management and could result in substantial costs or large judgments against us.

The stock market in general has recently experienced extreme price and volume fluctuations. In addition, the market prices of securities of companies in the biotechnology industry have been extremely volatile and have experienced fluctuations that have often been unrelated or disproportionate to the operating performance of these companies. These fluctuations could adversely affect the market price of our common stock. In the past, securities class action litigation has often been brought against companies following periods of volatility in the market prices of their securities. We may be the target of similar litigation in the future. Securities litigation could result in substantial costs and divert our management’s attention and resources, which could cause serious harm to our business, operating results and financial condition.

Item 3. Quantitative and Qualitative Disclosures About Market Risk

Market risk represents the risk of loss that may impact our financial position, operating results or cash flows due to changes in interest rates. The primary objective of our investment activities is to preserve capital, while maintaining liquidity, until it is required to fund operations. To minimize risk, we maintain our operating cash in commercial bank accounts. We invest our excess cash in high quality financial instruments with active secondary or resale markets consisting primarily of money market funds, U.S government guaranteed debt obligations, repurchase agreements with major financial institutions, and certain corporate debt securities, with the dollar weighted average effective maturity of the portfolio less than nine months and no security with an effective maturity in excess of 18 months. Since our investments have effective maturities that are short term in duration and the investments are denominated in U.S. dollars, we believe that we are not subject to any material credit, market or foreign exchange risk exposure. We do not have any derivative financial instruments.

Item 4. Controls and Procedures

Evaluation of Disclosure Controls and Procedures

Our management with participation of our Chief Executive Officer and Chief Financial Officer, evaluated the effectiveness of our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, or Exchange Act) as of September 30, 2005. In designing and evaluating our disclosure controls and procedures, our management recognized that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives, and our management necessarily applied its judgment in evaluating the cost-benefit relationship of possible controls and procedures. Based on this evaluation, our Chief Executive Officer and Chief Financial Officer concluded that, as of September 30, 2005, our disclosure controls and procedures were (1) designed to ensure that material information relating to us, including our consolidated subsidiaries, is made known to our CEO and CFO by others within those entities, particularly during the

period in which this report was being prepared and (2) effective, in that they provide reasonable assurance that information required to be disclosed by us in the reports that we file or submit under the Exchange Act is recorded, processed, summarized and reported within the time periods specified in the Securities and Exchange Commission’s rules and forms.

Changes in Internal Controls over Financial Reporting

No change in our internal control over financial reporting (as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act) occurred during the fiscal quarter ended September 30, 2005 that has materially affected or is reasonably likely to materially affect, our internal controls over financial reporting.

Part II. Other Information

Item 1. Legal Proceedings

None

Item 2. Unregistered Sales of Equity Securities and Use of Proceeds

(a) Unregistered Sales of Equity Securities

None.

(b) Initial Public Offering and Use of Proceeds from the Sale of Registered Securities

We registered shares of our common stock in connection with our initial public offering under the Securities Act. Our Registration Statement on Form S-1 (Reg. No. 333-111157) in connection with our initial public offering was declared effective by the SEC on July 21, 2004. We completed our initial public offering on July 27, 2004.

The aggregate purchase price of shares of our common stock sold in the offering by us was $64,400,000 and the net proceeds to us was approximately $57,000,000, after underwriting discounts and offering expenses. The net proceeds of the initial public offering are invested in investment grade securities with the dollar weighted average effective maturity of the portfolio less than nine months and no security with an effective maturity in excess of 18 months. There has been no material change in the planned use of proceeds from our initial public offering as described in our final prospectus filed with the SEC pursuant to Rule 424(b).

(c) Repurchase of Securities

None.

Item 3. Defaults Upon Senior Securities

None

Item 4. Submission of Matters to a Vote of Security Holders

None

Item 5. Other Information

None

Item 6. Exhibits

See Exhibit Index on the page immediately preceding the exhibits for a list of the exhibits filed as a part of this quarterly report, which Exhibit Index is incorporated by reference.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.


Date: November 8, 2005	By:	/s/ Jean-Pierre Sommadossi

		Jean-Pierre Sommadossi
		Chairman and Chief Executive Officer
		(Principal Executive Officer)

Date: November 8, 2005	By:	/s/ David A. Arkowitz

		David A. Arkowitz
		Chief Financial Officer and Treasurer (Principal Accounting Officer)

Exhibit Index


Exhibit
No.		Description

10.1+		Agreement, by and among Idenix Pharmaceuticals, Inc., Idenix SARL and the Universita delgi Studi Cagliari, dated October 24, 2005.

31.1		Certification of Chief Executive Officer pursuant to Rule 13a-14(a)/Rule 15d-14(a) of the Securities Exchange Act of 1934, as amended.

31.2		Certification of Chief Financial Officer pursuant to Rule 13a-14(a)/Rule 15d-14(a) of the Securities Exchange Act of 1934, as amended.

32.1		Certification of Chief Executive Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.

32.2		Certification of Chief Financial Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.


+		Confidential treatment requested as to certain portions, which portions have been filed separately with the Securities and Exchange Commission.