UNITED STATES
SECURITIES AND
EXCHANGE COMMISSION
WASHINGTON, D.C.
20549
SCHEDULE 13G/A
Under the Securities
Exchange Act of 1934
(Amendment No. 3)*
ImmunoGen, Inc.
(Name of Issuer)
Common Stock,
$0.01 par value per share
(Title of Class of
Securities)
45253H101
(CUSIP Number)
December 31,
2023
(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)
*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
| 1 |
Names
of Reporting Persons
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
RA Capital Management, L.P. |
| 2 |
Check
the Appropriate Box if a Member of a Group (See Instructions)
(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
26,916,027 |
| 7 |
Sole
Dispositive Power
0 |
| 8 |
Shared
Dispositive Power
26,916,027 |
| 9 |
Aggregate
Amount Beneficially Owned by Each Reporting Person
26,916,027 |
| 10 |
Check
BOX if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) ¨ |
| 11 |
Percent
of Class Represented by Amount in Row 9
9.99% |
| 12 |
Type
of Reporting Person (See Instructions)
IA, PN |
CUSIP No. 45253H101
| 1 |
Names
of Reporting Persons
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
Peter Kolchinsky |
| 2 |
Check
the Appropriate Box if a Member of a Group (See Instructions)
(a) ¨
(b) ¨ |
| 3 |
SEC
Use Only |
| 4 |
Citizenship
or Place of Organization
United States of America |
NUMBER OF
SHARES
BENEFICIALLY
OWNED BY
EACH
REPORTING
PERSON
WITH: |
5 |
Sole
Voting Power
0 |
| 6 |
Shared
Voting Power
26,916,027 |
| 7 |
Sole
Dispositive Power
0 |
| 8 |
Shared
Dispositive Power
26,916,027 |
| 9 |
Aggregate
Amount Beneficially Owned by Each Reporting Person
26,916,027 |
| 10 |
Check
BOX if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) ¨ |
| 11 |
Percent
of Class Represented by Amount in Row 9
9.99% |
| 12 |
Type
of Reporting Person (See Instructions)
HC, IN |
CUSIP No. 45253H101
| 1 |
Names
of Reporting Persons
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
Rajeev Shah |
| 2 |
Check
the Appropriate Box if a Member of a Group (See Instructions)
(a) ¨
(b) ¨ |
| 3 |
SEC
Use Only |
| 4 |
Citizenship
or Place of Organization
United States of America |
NUMBER OF
SHARES
BENEFICIALLY
OWNED BY
EACH
REPORTING
PERSON
WITH: |
5 |
Sole
Voting Power
0 |
| 6 |
Shared
Voting Power
26,916,027 |
| 7 |
Sole
Dispositive Power
0 |
| 8 |
Shared
Dispositive Power
26,916,027 |
| 9 |
Aggregate
Amount Beneficially Owned by Each Reporting Person
26,916,027 |
| 10 |
Check
BOX if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) ¨ |
| 11 |
Percent
of Class Represented by Amount in Row 9
9.99% |
| 12 |
Type
of Reporting Person (See Instructions)
HC, IN |
CUSIP No. 45253H101
| 1 |
Names
of Reporting Persons
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
RA Capital Healthcare Fund, L.P. |
| 2 |
Check
the Appropriate Box if a Member of a Group (See Instructions)
(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
26,916,027 |
| 7 |
Sole
Dispositive Power
0 |
| 8 |
Shared
Dispositive Power
26,916,027 |
| 9 |
Aggregate
Amount Beneficially Owned by Each Reporting Person
26,916,027 |
| 10 |
Check
BOX if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) ¨ |
| 11 |
Percent
of Class Represented by Amount in Row 9
9.99% |
| 12 |
Type
of Reporting Person (See Instructions)
PN |
| Item 1(a). | Name
of Issuer: |
ImmunoGen, Inc.
(the “Issuer”)
| Item 1(b). | Address
of Issuer’s Principal Executive Offices: |
830 Winter Street, Waltham,
MA 02451
| Item 2(a). | Names
of Persons Filing: |
The names of the persons
filing this report (collectively, the “Reporting Persons”) are:
RA Capital Management, L.P.
(“RA Capital”)
Peter Kolchinsky
Rajeev Shah
RA Capital Healthcare Fund,
L.P. (the “Fund”)
| Item 2(b). | Address
of Principal Business Office or, if None, Residence: |
The address of the principal
business office of each of the Reporting Persons is:
c/o RA Capital Management,
L.P., 200 Berkeley Street, 18th Floor, Boston MA 02116
RA Capital and the Fund are
Delaware limited partnerships. Dr. Kolchinsky and Mr. Shah are United States citizens.
| Item 2(d). | Title
of Class of Securities: |
Common stock, $0.01 par value
per share (“Common Stock”)
| Item 3. | If
this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or
(c), check whether the person filing is a: |
Not applicable.
The Fund directly holds (i) 23,750,601
shares of Common Stock and (ii) 21,853,000 Pre-funded warrants (“Pre-Funded Warrants”), through which it has the right
to acquire 21,853,000 shares of Common Stock subject to a Beneficial Ownership Blocker (as defined below).
The shares reported herein
for the Reporting Persons represent (i) 23,750,601 shares of Common Stock held directly, and (ii) 3,165,426 shares of Common
Stock that the Reporting Persons beneficially own based on the right to acquire, upon the exercise of the Pre-Funded Warrants. The Pre-Funded
Warrants are subject to a beneficial ownership blocker (“Beneficial Ownership Blocker”), which precludes the exercise of
the Pre-Funded Warrants to the extent that, following exercise, the Reporting Persons, together with its affiliates and other attribution
parties, would own more than 9.99% of the Common Stock outstanding. The Reporting Persons are currently prohibited from exercising the
Pre-Funded Warrants to the extent that such exercise would result in beneficial ownership of more than 26,916,027 shares of Common Stock.
The information required
by this item with respect to each Reporting Person is set forth in Rows 5 through 9 and 11 of the cover page to this Schedule 13G/A.
The beneficial ownership percentages reported are based on (i) 266,264,274 outstanding shares of Common Stock, as reported in the
Issuer’s Form 10-Q filed with the Securities and Exchange Commission on November 2, 2023, plus (ii) 3,165,426 shares
of Common Stock of which the Reporting Person may acquire beneficial ownership upon the exercise of Pre-Funded Warrants, as limited by
the Beneficial Ownership Blocker.
RA Capital Healthcare Fund
GP, LLC is the general partner of the Fund. The general partner of RA Capital is RA Capital Management GP, LLC, of which Dr. Kolchinsky
and Mr. Shah are the controlling persons. RA Capital serves as investment adviser for the Fund and may be deemed a beneficial owner,
for purposes of Section 13(d) of the Securities Exchange Act of 1934 (the “Act”), of any securities of the Issuer
held by the Fund. The Fund has delegated to RA Capital the sole power to vote and the sole power to dispose of all securities held in
the Fund’s portfolio, including the shares of the Issuer’s Common Stock reported herein. Because the Fund has divested voting
and investment power over the reported securities it holds and may not revoke that delegation on less than 61 days’ notice, the
Fund disclaims beneficial ownership of the securities it holds for purposes of Section 13(d) of the Act. As managers of RA
Capital, Dr. Kolchinsky and Mr. Shah may be deemed beneficial owners, for purposes of Section 13(d) of the Act, of
any securities of the Issuer beneficially owned by RA Capital. RA Capital, Dr. Kolchinsky, and Mr. Shah disclaim beneficial
ownership of the securities reported in this Schedule 13G/A other than for the purpose of determining their obligations under Section 13(d) of
the Act, and the filing of this Schedule 13G/A shall not be deemed an admission that either RA Capital, Dr. Kolchinsky, or Mr. Shah
is the beneficial owner of such securities for any other purpose.
| Item 5. | Ownership
of Five Percent or Less of a Class. |
If
this statement is being filed to report the fact that as of the date hereof the Reporting Persons have ceased to be the beneficial owner
of more than five percent of the class of securities, check the following ¨.
| 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.
By
signing below I certify that, to the best of my 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, other than activities solely in connection with a nomination under § 240.14a–11.
Exhibit List
Exhibit 1: Joint Filing Agreement
SIGNATURE
After reasonable
inquiry and to the best of its knowledge and belief, each of the undersigned certifies that the information set forth in this statement
is true, complete and correct.
Date: February 14,
2024
| RA CAPITAL MANAGEMENT, L.P. |
| |
|
|
| By: |
/s/
Peter Kolchinsky |
|
| |
Name: |
Peter Kolchinsky |
|
| |
Title: |
Authorized Signatory |
|
| |
|
|
| PETER KOLCHINSKY |
| |
|
|
| /s/
Peter Kolchinsky |
|
| |
|
|
| RAJEEV SHAH |
|
| |
|
|
| /s/
Rajeev Shah |
|
| |
|
|
| RA CAPITAL HEALTHCARE FUND, L.P. |
| |
|
|
| By: |
RA Capital Healthcare Fund GP, LLC |
| Its: |
General Partner |
| |
|
|
| By: |
/s/
Peter Kolchinsky |
|
| |
Name: |
Peter Kolchinsky |
|
| |
Title: |
Manager |
|
EXHIBIT 1
AGREEMENT
This Joint Filing Agreement, dated as
of February 14, 2024, is by and among RA Capital Management, L.P., Peter Kolchinsky, Rajeev Shah, and RA Capital Healthcare Fund,
L.P. (the foregoing are collectively referred to herein as the “Filers”).
Each of the Filers may be required to
file with the United States Securities and Exchange Commission a statement on Schedule 13G and/or 13D with respect to Common Stock, $0.01
par value per share of ImmunoGen, Inc. beneficially owned by them from time to time.
Pursuant to and in accordance with Rule 13(d)(1)(k) promulgated
under the Securities Exchange Act of 1934, as amended, the Filers hereby agree to file a single statement on Schedule 13G and/or 13D
(and any amendments thereto) on behalf of each of such parties, and hereby further agree to file this Joint Filing Agreement as an exhibit
to such statement, as required by such rule.
This Joint Filing Agreement may be terminated
by any of the Filers upon one week’s prior written notice or such lesser period of notice as the Filers may mutually agree.
Executed and delivered as of the date
first above written.
| RA CAPITAL MANAGEMENT, L.P. |
| |
|
|
| By: |
/s/
Peter Kolchinsky |
|
| |
Name: |
Peter Kolchinsky |
|
| |
Title: |
Authorized Signatory |
|
| |
|
|
| PETER KOLCHINSKY |
| |
|
|
| /s/
Peter Kolchinsky |
|
| |
|
|
| RAJEEV SHAH |
|
| |
|
|
| /s/
Rajeev Shah |
|
| |
|
|
| RA CAPITAL HEALTHCARE FUND, L.P. |
| |
|
|
| By: |
RA Capital Healthcare Fund GP, LLC |
| Its: |
General Partner |
| |
|
|
| By: |
/s/
Peter Kolchinsky |
|
| |
Name: |
Peter Kolchinsky |
|
| |
Title: |
Manager |
|
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