SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
 
SCHEDULE 13G
 
Under the Securities Exchange Act of 1934
(Amendment No.  )*
 

ImmunoGen, Inc.

(Name of Issuer)
 

Common Stock, par value $0.01 per share

(Title of Class of Securities)
 

45253H101

(CUSIP Number)
 

August 2, 2017

(Date of Event Which Requires Filing of This Statement)
 
 
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
 
¨ Rule 13d-1(b)
x Rule 13d-1(c)
¨ Rule 13d-1(d)
 
(Page 1 of 14 Pages)

 

______________________________

*The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

 

 

CUSIP No. 45253H10113GPage 2 of 14 Pages

 

1

NAME OF REPORTING PERSON

Polygon Convertible Opportunity Master Fund

2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

3 SEC USE ONLY
4

CITIZENSHIP OR PLACE OF ORGANIZATION

Cayman Islands

NUMBER OF
SHARES
BENEFICIALLY
OWNED BY
EACH
REPORTING
PERSON WITH:		 5

SOLE VOTING POWER

0

6

SHARED VOTING POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

7

SOLE DISPOSITIVE POWER

0

8

SHARED DISPOSITIVE POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

9

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

5.2%

12

TYPE OF REPORTING PERSON

OO

         

 

 

CUSIP No. 45253H10113GPage 3 of 14 Pages

 

 

1

NAME OF REPORTING PERSON

Polygon Management Ltd.

2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

3 SEC USE ONLY
4

CITIZENSHIP OR PLACE OF ORGANIZATION

Cayman Islands

NUMBER OF
SHARES
BENEFICIALLY
OWNED BY
EACH
REPORTING
PERSON WITH:		 5

SOLE VOTING POWER

0

6

SHARED VOTING POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

7

SOLE DISPOSITIVE POWER

0

8

SHARED DISPOSITIVE POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

9

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

5.2%

12

TYPE OF REPORTING PERSON

OO

         

 

 

CUSIP No. 45253H10113GPage 4 of 14 Pages

 

 

1

NAME OF REPORTING PERSON

Polygon Global Partners LP

2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

3 SEC USE ONLY
4

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF
SHARES
BENEFICIALLY
OWNED BY
EACH
REPORTING
PERSON WITH:		 5

SOLE VOTING POWER

0

6

SHARED VOTING POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

7

SOLE DISPOSITIVE POWER

0

8

SHARED DISPOSITIVE POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

9

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

5.2%

12

TYPE OF REPORTING PERSON

PN

         

 

CUSIP No. 45253H10113GPage 5 of 14 Pages

 

 

1

NAME OF REPORTING PERSON

Polygon Global Partners LLP

2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

3 SEC USE ONLY
4

CITIZENSHIP OR PLACE OF ORGANIZATION

United Kingdom

NUMBER OF
SHARES
BENEFICIALLY
OWNED BY
EACH
REPORTING
PERSON WITH:		 5

SOLE VOTING POWER

0

6

SHARED VOTING POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

7

SOLE DISPOSITIVE POWER

0

8

SHARED DISPOSITIVE POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

9

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

5.2%

12

TYPE OF REPORTING PERSON

PN

         

 

CUSIP No. 45253H10113GPage 6 of 14 Pages

 

 

1

NAME OF REPORTING PERSON

TFG Asset Management L.P.

2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

3 SEC USE ONLY
4

CITIZENSHIP OR PLACE OF ORGANIZATION

Cayman Islands

NUMBER OF
SHARES
BENEFICIALLY
OWNED BY
EACH
REPORTING
PERSON WITH:		 5

SOLE VOTING POWER

0

6

SHARED VOTING POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

7

SOLE DISPOSITIVE POWER

0

8

SHARED DISPOSITIVE POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

9

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

5.2%

12

TYPE OF REPORTING PERSON

IA; PN

         

 

CUSIP No. 45253H10113GPage 7 of 14 Pages

 

 

1

NAME OF REPORTING PERSON

Patrick G. G. Dear

2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

3 SEC USE ONLY
4

CITIZENSHIP OR PLACE OF ORGANIZATION

United Kingdom

NUMBER OF
SHARES
BENEFICIALLY
OWNED BY
EACH
REPORTING
PERSON WITH:		 5

SOLE VOTING POWER

0

6

SHARED VOTING POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

7

SOLE DISPOSITIVE POWER

0

8

SHARED DISPOSITIVE POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

9

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

5.2%

12

TYPE OF REPORTING PERSON

IN

         

 

CUSIP No. 45253H10113GPage 8 of 14 Pages

 

 

1

NAME OF REPORTING PERSON

Reade E. Griffith

2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ¨

(b) ¨

3 SEC USE ONLY
4

CITIZENSHIP OR PLACE OF ORGANIZATION

United Kingdom

NUMBER OF
SHARES
BENEFICIALLY
OWNED BY
EACH
REPORTING
PERSON WITH:		 5

SOLE VOTING POWER

0

6

SHARED VOTING POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

7

SOLE DISPOSITIVE POWER

0

8

SHARED DISPOSITIVE POWER

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

9

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

4,894,938 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021

10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

5.2%

12

TYPE OF REPORTING PERSON

IN

         

 

CUSIP No. 45253H10113GPage 9 of 14 Pages

 

Item 1.  
  (a) NAME OF ISSUER
  ImmunoGen, Inc. (the "Issuer").
   
  (b) ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES
 

830 Winter Street
Waltham, MA 02451

 

Item 2.  
  (a) NAME OF PERSON FILING
  (b) ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE
  (c) CITIZENSHIP
   
 

This Schedule 13G is filed on behalf of the following persons and entities (collectively, the "Reporting Persons").

 

Polygon Convertible Opportunity Master Fund (the "Master Fund")

P.O. Box 309

Ugland House

Grand Cayman, E9 KY1-1104

Citizenship: Cayman Islands

 

Polygon Management Ltd. (the "General Partner")

P.O. Box 309

Ugland House

Grand Cayman, E9 KY1-1104

Citizenship: Cayman Islands

 

Polygon Global Partners LP (the "US Investment Manager")

399 Park Avenue

22nd Floor

New York, NY 10022

Citizenship: Delaware

 

Polygon Global Partners LLP (the "UK Investment Manager")

4 Sloane Terrace

London, X0 SW1X9DQ

United Kingdom

Citizenship: United Kingdom

 

TFG Asset Management L.P. (the "Manager")

PO Box 309

Ugland House

Grand Cayman, E9 KY1-1104

Citizenship: Cayman Islands

 

 

Patrick G. G. Dear ("Mr. Dear")

c/o Polygon Global Partners LLP

4 Sloane Terrace

London, X0 SW1X9DQ

United Kingdom

Citizenship: United Kingdom

 

CUSIP No. 45253H10113GPage 10 of 14 Pages

 

 

Reade E. Griffith ("Mr. Griffith")

c/o Polygon Global Partners LLP

4 Sloane Terrace

London, X0 SW1X9DQ

United Kingdom

Citizenship: United Kingdom

 

Item 2(d). TITLE OF CLASS OF SECURITIES
  Common Stock, $0.01 par value (the "Common Stock")
   
Item 2(e). CUSIP NUMBER
  45253H101
   
Item 3. IF THIS STATEMENT IS FILED PURSUANT TO Rules 13d-1(b), OR 13d-2(b) OR (c), CHECK WHETHER THE PERSON FILING IS A:

 

  (a) ¨ Broker or dealer registered under Section 15 of the Act;
  (b) ¨ Bank as defined in Section 3(a)(6) of the Act;
  (c) ¨ Insurance company as defined in Section 3(a)(19) of the Act;
  (d) ¨ Investment company registered under Section 8 of the Investment Company Act of 1940;
  (e) ¨ An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);
  (f) ¨

An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F);

 

  (g) ¨

A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G);

 

  (h) ¨

A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act;

 

  (i) ¨

A church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act;

 

  (j) ¨ A non-U.S. institution in accordance with Rule 13d-1(b)(1)(ii)(J);
  (k) ¨ Group, in accordance with Rule 13d-1(b)(1)(ii)(K).

 

 

If filing as a non-U.S. institution in accordance with Rule 13d-1(b)(1)(ii)(J), please

specify the type of institution: ____________________________

   

 

 

CUSIP No. 45253H10113GPage 11 of 14 Pages

 

 

Item 4. OWNERSHIP
   
  The information required by Items 4(a) – (c) is set forth in Rows (5) – (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each such Reporting Person.
   
  The percentages used in this Schedule 13G are calculated based upon 89,348,389 shares of Common Stock outstanding as of March 31, 2017, as reported in the Company's Prospectus filed pursuant to Rule 424(b)(5) filed with the Securities and Exchange Commission on May 11, 2017 and assumes the conversion of the 4.50% Convertible Senior Notes due 2021 held by the Master Fund.
   
  All of the 4.50% Convertible Senior Notes due 2021 are directly held by the Master Fund. The Manager, the US Investment Manager, the UK Investment Manager and the General Partner have voting and dispositive power over the securities held by the Master Fund. Messrs. Dear and Griffith control the Manager, the US Investment Manager, the UK Investment Manager and the General Partner.  The filing of this statement should not be construed as an admission that any of the Reporting Persons is, for the purposes of Sections 13 of the Securities Exchange Act of 1934, the beneficial owner of the shares of Common Stock reported herein.

 

Item 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS
   
  Not applicable.
   
Item 6. OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON
   
  Not applicable.
   
   
Item 7. IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY OR CONTROL PERSON
   
  Not applicable.
   
   
Item 8. IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP
   
  Not applicable.
   
   
Item 9. NOTICE OF DISSOLUTION OF GROUP
   
  Not applicable.
   

 

 

 

CUSIP No. 45253H10113GPage 12 of 14 Pages

 

Item 10. CERTIFICATION
   
  By signing below each of the undersigned certifies that, to the best of such person’s knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.
   

 

 

CUSIP No. 45253H10113GPage 13 of 14 Pages

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, each of the undersigned hereby certifies that the information set forth in this statement is true, complete and correct.

DATE: August 7, 2017

 

   
POLYGON CONVERTIBLE OPPORTUNITY MASTER FUND  
   
/s/ Michael Humphries  
Name:  Michael Humphries  
Title: Director  
   
POLYGON MANAGEMENT LTD.  
   
/s/ Reade E. Griffith  
Name:  Reade E. Griffith  
Title: Authorized Person  
   
POLYGON GLOBAL PARTNERS LP  
   
/s/ Reade E. Griffith  
Name:  Reade E. Griffith  
Title: Principal  
   
POLYGON GLOBAL PARTNERS LLP  
   
/s/ Reade E. Griffith  
Name:  Reade E. Griffith  
Title: Principal  
   
TFG ASSET MANAGEMENT L.P.  
By: Polygon Management Ltd., its general partner  
   
/s/ Reade E. Griffith  
Name:  Reade E. Griffith  
Title: Authorized Person  
   
/s/ Patrick G. G. Dear  
Patrick G. G. Dear  
   
/s/ Reade E. Griffith  
Reade E. Griffith  
   

 

 

CUSIP No. 45253H10113GPage 14 of 14 Pages

Exhibit 1

JOINT FILING AGREEMENT

PURSUANT TO RULE 13d-1(k)

 

The undersigned acknowledge and agree that the foregoing statement on Schedule 13G is filed on behalf of each of the undersigned and that all subsequent amendments to this statement on Schedule 13G shall be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements. The undersigned acknowledge that each shall be responsible for the timely filing of such amendments, and for the completeness and accuracy of the information concerning him or it contained herein and therein, but shall not be responsible for the completeness and accuracy of the information concerning the others, except to the extent that he or it knows or has reason to believe that such information is inaccurate.

 

DATE: August 7, 2017

   
POLYGON CONVERTIBLE OPPORTUNITY MASTER FUND  
   
/s/ Michael Humphries  
Name:  Michael Humphries  
Title: Director  
   
POLYGON MANAGEMENT LTD.  
   
/s/ Reade E. Griffith  
Name:  Reade E. Griffith  
Title: Authorized Person  
   
POLYGON GLOBAL PARTNERS LP  
   
/s/ Reade E. Griffith  
Name:  Reade E. Griffith  
Title: Principal  
   
POLYGON GLOBAL PARTNERS LLP  
   
/s/ Reade E. Griffith  
Name:  Reade E. Griffith  
Title: Principal  
   
TFG ASSET MANAGEMENT L.P.  
By: Polygon Management Ltd., its general partner  
   
/s/ Reade E. Griffith  
Name:  Reade E. Griffith  
Title: Authorized Person  
   
/s/ Patrick G. G. Dear  
Patrick G. G. Dear  
   
/s/ Reade E. Griffith  
Reade E. Griffith