| 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) | |
|
April 13, 2017 | |
| (Date of event which requires filing of this statement) | |
| Check the appropriate box to designate the rule pursuant to which this Schedule 13G is filed: | |
| ¨ | Rule 13d-1(b) |
| x | Rule 13d-1(c) |
| ¨ | Rule 13d-1(d) |
| (Page 1 of 6 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. 45253H101 | 13G | Page 2 of 6 Pages |
| 1 |
NAMES OF REPORTING PERSONS Highbridge Capital Management, LLC | |||
| 2 | CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP |
(a) ¨ (b) ¨ | ||
| 3 | SEC USE ONLY | |||
| 4 |
CITIZENSHIP OR PLACE OF ORGANIZATION State of Delaware | |||
| NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH |
5 |
SOLE VOTING POWER 0 | ||
| 6 |
SHARED VOTING POWER 5,036,294 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021
| |||
| 7 |
SOLE DISPOSITIVE POWER 0 | |||
| 8 |
SHARED DISPOSITIVE POWER 5,036,294 shares of Common Stock issuable upon conversion of 4.50% Convertible Senior Notes due 2021
| |||
| 9 |
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,036,294 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) 5.34% | |||
| 12 |
TYPE OF REPORTING PERSON IA, OO | |||
| CUSIP No. 45253H101 | 13G | Page 3 of 6 Pages |
| Item 1(a). | NAME OF ISSUER: |
| The name of the issuer is ImmunoGen, Inc. (the "Company"). |
| Item 1(b). | ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES: |
| The Company's principal executive offices are located at 830 Winter Street, Waltham, MA 02451. |
| Item 2(a). | NAME OF PERSON FILING: |
| Item 2(b). | ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE: |
| Item 2(c). | CITIZENSHIP: |
| This statement is filed by: | ||
|
Highbridge Capital Management, LLC 40 West 57th Street, 32nd Floor New York, New York 10019 Citizenship: State of Delaware | ||
| The foregoing person is hereinafter sometimes referred to as the "Reporting Person." | ||
| Item 2(d). | TITLE OF CLASS OF SECURITIES: |
| Common Stock, par value $0.01 per share (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) | ¨ | Employee Benefit Plan or Endowment Fund in accordance with Rule 13d-1(b)(1)(ii)(F), | |
| (g) | ¨ | Parent Holding Company or control person in accordance with Rule 13d-1(b)(1)(ii)(G), | |
| (h) | ¨ | Savings Association as defined in Section 3(b) of the Federal Deposit Insurance Act, |
| CUSIP No. 45253H101 | 13G | Page 4 of 6 Pages |
| (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:_________________________ |
| Item 4. | OWNERSHIP. |
| (a) | Amount beneficially owned: |
| As of the date hereof, Highbridge Capital Management, LLC, as the trading manager of Highbridge International LLC and Highbridge Tactical Credit & Convertibles Master Fund, L.P. (collectively, the "Highbridge Funds"), may be deemed to be the beneficial owner of the 5,036,294 shares of Common Stock issuable upon conversion of the 4.50% Convertible Senior Notes due 2021 held by the Highbridge Funds. |
| (b) | Percent of class: |
|
The percentages used herein and in the rest of this Schedule 13G are calculated based upon 89,348,389 shares of Common Stock reported to be outstanding in the Company's Preliminary Proxy Statement on Schedule 14A filed with the Securities and Exchange Commission on April 18, 2017 and assumes the conversion of the 4.50% Convertible Senior Notes due 2021 held by the Highbridge Funds. Therefore, as of the date hereof, based on the Company's outstanding shares of Common Stock and assuming the conversion of the 4.50% Convertible Senior Notes due 2021 held by the Highbridge Funds, Highbridge Capital Management, LLC may be deemed to beneficially own approximately 5.34% of the outstanding shares of Common Stock of the Company. The foregoing should not be construed in and of itself as an admission by the Reporting Person as to beneficial ownership of the shares of Common Stock issuable upon conversion of the 4.50% Convertible Senior Notes due 2021 held by the Highbridge Funds. |
| (c) | Number of shares as to which such person has: |
| (i) | Sole power to vote or to direct the vote | |||
| 0 |
| (ii) | Shared power to vote or to direct the vote | |||
| See Item 4(a) |
| (iii) | Sole power to dispose or to direct the disposition of | |||
| 0 | ||||
| CUSIP No. 45253H101 | 13G | Page 5 of 6 Pages |
| (iv) | Shared power to dispose or to direct the disposition of | |||
| See Item 4(a) |
| 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. |
| See Item 4. | |
| Item 7. | IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY. |
| Not applicable. | |
| Item 8. | IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP. |
| Not applicable. | |
| Item 9. | NOTICE OF DISSOLUTION OF GROUP. |
| Not applicable. | |
| Item 10. | CERTIFICATION. |
| The Reporting Person hereby makes the following certification: | |
| By signing below the Reporting Person certifies that, to the best of its 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. 45253H101 | 13G | Page 6 of 6 Pages |
SIGNATURES
After reasonable inquiry and to the best of our knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct.
DATED: April 24, 2017
| HIGHBRIDGE CAPITAL MANAGEMENT, LLC | |||
| By: |
/s/ John Oliva |
||
| Name: John Oliva | |||
| Title: Managing Director | |||