FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * Erion Mark D   2. Issuer Name and Ticker or Trading Symbol METABASIS THERAPEUTICS INC [MBRX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Chief Executive Officer (Last) (First) (Middle) 11119 NORTH TORREY PINES ROAD 3. Date of Earliest Transaction (Month/Day/Year) 01/29/2009 (Street) LA JOLLA, CA 92037 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Stock Option (Right to Buy)

$ 9.03

01/29/2009

D

75,000

(1)

03/19/2016

Common Stock

75,000

(2)

0

D

Stock Option (Right to Buy)

$ 7.55

01/29/2009

D

75,000

(3)

03/07/2017

Common Stock

75,000

(2)

0

D

Stock Option (Right to Buy)

$ 2.1

01/29/2009

D

90,000

(4)

04/02/2018

Common Stock

90,000

(2)

0

D

Stock Option (Right to Buy)

$ 1

01/29/2009

D

240,000

(5)

01/29/2019

Common Stock

240,000

(2)

240,000

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Erion Mark D 11119 NORTH TORREY PINES ROAD LA JOLLA, CA 92037			Chief Executive Officer

Signatures

Trisha Millican, by Power of Attorney		02/02/2009
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	The cancelled option provided for 25% of the shares vesting on the first anniversary of the grant date (3/19/2006), and the remaining shares vesting in equal monthly installments over the following three years.
(2)	Pursuant to the Company's Offer to Exchange Stock Options, on January 29, 2009, the Company cancelled options granted to the reporting person in exchange for new options equal to the number of shares under the cancelled options.
(3)	The cancelled option provided for 25% of the shares vesting on the first anniversary of the grant date (3/7/2007), and the remaining shares vesting in equal monthly installments over the following three years.
(4)	The cancelled option provided for 25% of the shares vesting on the first anniversary of the grant date (4/2/2008), and the remaining shares vesting in equal monthly installments over the following three years.
(5)	The option provides for 25% of the shares to vest six months from the grant date (1/29/09) and the remaining 75% of the shares to vest in equal monthly installments over three years beginning on the grant date.

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