IMGN / ImmunoGen, Inc. - SEC Filings, Annual Report, Proxy Statement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 15 CERTIFICATION AND NOTICE OF TERMINATION OF REGISTRATION UNDER SECTION 12(g) OF THE SECURITIES EXCHANGE ACT OF 1934 OR SUSPENSION OF DUTY TO FILE REPORTS UNDER SECTIONS 13

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 15 CERTIFICATION AND NOTICE OF TERMINATION OF REGISTRATION UNDER SECTION 12(g) OF THE SECURITIES EXCHANGE ACT OF 1934 OR SUSPENSION OF DUTY TO FILE REPORTS UNDER SECTIONS 13 AND 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission File Number: 000-17999 ImmunoGen, Inc. (Exact name of registrant as specified in its char

IMGN / ImmunoGen, Inc. / RA CAPITAL MANAGEMENT, L.P. - SC 13G/A Passive Investment

SC 13G/A 1 tm246065d13sc13ga.htm SC 13G/A 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 t

AGREEMENT

EX-99.1 2 tm246065d13ex1.htm EXHIBIT 1 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 Commissio

Joint Filing Agreement

EX-99.1 2 tm245846d22ex99-1.htm EXHIBIT 99.1 Exhibit 99.1 Joint Filing Agreement In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), the undersigned hereby agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto, the “Schedule 13G”) relating to the Common Stock, $0.01 pa

IMGN / ImmunoGen, Inc. / Redmile Group, LLC - SC 13G/A Passive Investment

SC 13G/A 1 tm245846d22sc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 6) ImmunoGen, Inc. (Name of Issuer) Common Stock, $0.01 par value (Title of Class of Securities) 45253H101 (CUSIP Number) December 31, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriat

IMGN / ImmunoGen, Inc. / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SC 13G/A 1 tv01170-immunogeninc.htm SCHEDULE 13G/A SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 6)* Name of issuer: ImmunoGen Inc Title of Class of Securities: Common Stock CUSIP Number: 45253H101 Date of Event Which Requires Filing of this Statement: December 29, 2023 Check the appropriate box to designate the rul

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

Changes in Control of Registrant, Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Termination of a Material Definitive Agreement, Material Modification to Rights of Security Holders, Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing, Financial Statements and Exhibits, Completion of Acquisition or Disposition of Assets

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 12, 2024 ImmunoGen, Inc.† (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission F

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

EX-99.25

imgn-form25

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

IMMUNOGEN, INC. AMENDED AND RESTATED BYLAWS AMENDED AND RESTATED BYLAWS FOR THE REGULATION OF IMMUNOGEN, INC. A MASSACHUSETTS CORPORATION TABLE OF CONTENTS

Exhibit 3.2 IMMUNOGEN, INC. AMENDED AND RESTATED BYLAWS AMENDED AND RESTATED BYLAWS FOR THE REGULATION OF IMMUNOGEN, INC. A MASSACHUSETTS CORPORATION TABLE OF CONTENTS Page ARTICLE I NAME, OFFICES AND SEAL 1 Section 1.1. Name 1 Section 1.2. Registered Office 1 Section 1.3. Other Offices 1 Section 1.4. Seal 1 ARTICLE II SHAREHOLDERS 1 Section 2.1. Place of a Meeting 1 Section 2.2. Annual Meetings 1

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

As filed with the Securities and Exchange Commission on February 12, 2024

As filed with the Securities and Exchange Commission on February 12, 2024 Registration No.

ARTICLE III State the total number of shares and par value, * if any, of each class of stock that the corporation is authorized to issue. All corpo-rations must authorize stock. If only one class or series is authorized, it is not necessary to specif

Exhibit 3.1 FORM MUST BE TYPED FORM MUST BE TYPED 5IF$PNNPOXFBMUIPG.BTTBDIVTFUUT William Francis Galvin Secretary of the Commonwealth One Ashburton Place, Boston, Massachusetts 02108-1512 P.C. c156ds1007950c11335 01/13/05 * Changes to Article VIII must be made by filing a statement of change of supplemental information form. ** Professional corporations governed by G.L. Chapter 156A and must speci

Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 7, 2024 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

IMGN / ImmunoGen, Inc. / ADAGE CAPITAL PARTNERS GP, L.L.C. - IMMUNOGEN, INC. Passive Investment

SC 13G/A 1 p24-0407sc13ga.htm IMMUNOGEN, INC. SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 1)* ImmunoGen, Inc. (Name of Issuer) Common Stock, par value $0.01 per share (Title of Class of Securities) 45253H101 (CUSIP Number) December 31, 2023 (Date of Event Which Requires Filing of This Statement) Check the appropr

Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 31, 2024 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant x Filed by a Party other than the Registrant ¨ Check the appropriate box: ¨ Preliminary Proxy Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ¨ Definitive Proxy Statement x Definitive Additional Materials ¨ Soliciting Material Pursuant to §240.

Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 29, 2024 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant x Filed by a Party other than the Registrant ¨ Check the appropriate box: ¨ Preliminary Proxy Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ¨ Definitive Proxy Statement x Definitive Additional Materials ¨ Soliciting Material Pursuant to §240.

Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 24, 2024 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 8, 2024 ImmunoGen, Inc. (

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 8, 2024 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant x Filed by a Party other than the Registrant ¨ Check the appropriate box: ¨ Preliminary Proxy Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ¨ Definitive Proxy Statement x Definitive Additional Materials ¨ Soliciting Material Pursuant to §240.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(A) OF THE SECURITIES EXCHANGE ACT OF 1934

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(A) OF THE SECURITIES EXCHANGE ACT OF 1934 Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Defi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant x Filed by a Party other than the Registrant ¨ Check the appropriate box: ¨ Preliminary Proxy Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ¨ Definitive Proxy Statement ¨ Definitive Additional Materials x Soliciting Material Pursuant to §240.

CALCULATION OF FILING FEE TABLES Schedule 14A (Form Type) ImmunoGen, Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Transaction Valuation

Exhibit 107 CALCULATION OF FILING FEE TABLES Schedule 14A (Form Type) ImmunoGen, Inc.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(A) OF THE SECURITIES EXCHANGE ACT OF 1934

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(A) OF THE SECURITIES EXCHANGE ACT OF 1934 Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Defi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant x Filed by a Party other than the Registrant ¨ Check the appropriate box: ¨ Preliminary Proxy Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ¨ Definitive Proxy Statement ¨ Definitive Additional Materials x Soliciting Material Pursuant to §240.

AbbVie to Acquire ImmunoGen, including its Flagship Cancer Therapy ELAHERE® (mirvetuximab soravtansine-gynx), Expanding Solid Tumor Portfolio

Exhibit 99.1 AbbVie to Acquire ImmunoGen, including its Flagship Cancer Therapy ELAHERE® (mirvetuximab soravtansine-gynx), Expanding Solid Tumor Portfolio November 30, 2023 · Proposed acquisition will accelerate AbbVie's entry into the commercial market for ovarian cancer ELAHERE® is a first-in-class antibody-drug conjugate (ADC) approved for platinum-resistant ovarian cancer · ImmunoGen's late-st

AGREEMENT AND PLAN OF MERGER Abbvie Inc., AThene subsidiary LLC, ATHENE MERGER SUB INC. IMMUNOGEN, INC.. Dated as of November 30, 2023 TABLE OF CONTENTS

Exhibit 2.1 Execution Version AGREEMENT AND PLAN OF MERGER among Abbvie Inc., AThene subsidiary LLC, ATHENE MERGER SUB INC. and IMMUNOGEN, INC.. Dated as of November 30, 2023 TABLE OF CONTENTS Article I THE MERGER 1 Section 1.1. The Merger 1 Section 1.2. Closing; Effective Time 2 Section 1.3. Effects of the Merger 2 Section 1.4. Articles of Organization and Bylaws of the Surviving Corporation 2 Se

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 30, 2023 ImmunoGen, Inc.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 30, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fi

AGREEMENT AND PLAN OF MERGER Abbvie Inc., AThene subsidiary LLC, ATHENE MERGER SUB INC. IMMUNOGEN, INC.. Dated as of November 30, 2023 TABLE OF CONTENTS

Exhibit 2.1 Execution Version AGREEMENT AND PLAN OF MERGER among Abbvie Inc., AThene subsidiary LLC, ATHENE MERGER SUB INC. and IMMUNOGEN, INC.. Dated as of November 30, 2023 TABLE OF CONTENTS Article I THE MERGER 1 Section 1.1. The Merger 1 Section 1.2. Closing; Effective Time 2 Section 1.3. Effects of the Merger 2 Section 1.4. Articles of Organization and Bylaws of the Surviving Corporation 2 Se

AbbVie to Acquire ImmunoGen, including its Flagship Cancer Therapy ELAHERE® (mirvetuximab soravtansine-gynx), Expanding Solid Tumor Portfolio

Exhibit 99.1 AbbVie to Acquire ImmunoGen, including its Flagship Cancer Therapy ELAHERE® (mirvetuximab soravtansine-gynx), Expanding Solid Tumor Portfolio November 30, 2023 · Proposed acquisition will accelerate AbbVie's entry into the commercial market for ovarian cancer ELAHERE® is a first-in-class antibody-drug conjugate (ADC) approved for platinum-resistant ovarian cancer · ImmunoGen's late-st

Entry into a Material Definitive Agreement, Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 30, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fi

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 2, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

Change in Control Severance Agreement dated as of September18, 2023 between the Registrant and Lauren White

EXHIBIT 10.1 CHANGE IN CONTROL SEVERANCE AGREEMENT This Agreement is entered into as of the 18th day of September, 2023 (the “Effective Date”) by and between ImmunoGen, Inc., a Massachusetts corporation (the “Company”), and Lauren White (the “Executive”). WHEREAS, the Company recognizes that the Executive’s service to the Company is very important to the future success of the Company; WHEREAS, the

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ImmunoGen Reports Recent Progress and Third Quarter 2023 Financial Results Continued Strong Demand for ELAHERE; US Net Sales of $105.2 Million in Q3 ELAHERE MAA in FRα-Positive Platinum-Resistant Ovarian Cancer Accepted by EMA; sBLA to Support Full Approval in US Submitted to FDA PICCOLO Trial of ELAHERE in Platinum-Sensitive Ovarian Cancer Meets Primary Endpoint of Objective Response

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 OR ☐ 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 0-17999 I

Offer Letter dated as of September 18, 2023 between the Registrant and Lauren White

Exhibit 10.2 August 4, 2023 Lauren White 16 Laudholm Rd Newton, MA 02458 Dear Lauren: I am delighted to offer you the full-time position of Senior Vice President, Chief Financial Officer at ImmunoGen, Inc. (“ImmunoGen or the “Company”). The terms and conditions of this offer are set out below. We look forward to you joining ImmunoGen. Position. As noted above, your title will be Senior Vice Presid

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): September 18, 2023 ImmunoGen, Inc

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): September 18, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission F

ImmunoGen Appoints Lauren White as Senior Vice President and Chief Financial Officer

Exhibit 99.1 ImmunoGen Appoints Lauren White as Senior Vice President and Chief Financial Officer Waltham, MA – September 18, 2023 – ImmunoGen, Inc. (Nasdaq: IMGN), a leader in the expanding field of antibody-drug conjugates (ADCs) for the treatment of cancer, today announced that Lauren White has been appointed Senior Vice President and Chief Financial Officer. "We are excited to have Lauren join

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): July 31, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File N

Amended and Restated By-Laws

EXHIBIT 3.2 ImmunoGen, Inc. BY-LAWS AMENDED AND RESTATED AS OF JUNE 14, 2023 TABLE OF CONTENTS ARTICLE I- Shareholders‌3 Section 1.1Place and Conduct of Meetings‌3 Section 1.2Annual Meetings‌3 Section 1.3Special Meetings‌3 Section 1.4Notice of Meetings‌3 Section 1.5Quorum of Shareholders‌4 Section 1.6Adjournments‌4 Section 1.7Votes and Proxies‌4 Section 1.8Action at Meeting‌4 Section 1.9Inspector

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 OR ☐ 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 0-17999 Immuno

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ImmunoGen Reports Recent Progress and Second Quarter 2023 Financial Results Continued Strong Momentum with ELAHERE Launch in US; Net Sales of $77.4 Million in Q2 Presented Positive Results for ELAHERE from Phase 3 MIRASOL Trial During Late-Breaking Oral Presentation at ASCO; First Therapy to Demonstrate an Overall Survival Benefit Compared to Chemotherapy in a Phase 3 Trial in Platinu

Compensation Policy for Non-Employee Directors, as amended through June 14, 2023

EXHIBIT 10.1 ImmunoGen, Inc. Compensation Policy for Non-Employee Directors (Effective June 14, 2023) Objective It is the objective of ImmunoGen, Inc. to compensate non-employee members (each, a “Director”) of the Board of Directors (the “Board”) in a manner that will enable the recruitment and retention of highly qualified Directors by fairly compensating them for their services as Directors. Cas

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Financial Statements and Exhibits, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 14, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File N

Amended and Restated By-Laws, marked for amendments

Exhibit 3.1 ImmunoGen, Inc. BY-LAWS AMENDED AND RESTATED AS OF JUNE 1514, 20162023 TABLE OF CONTENTS Title Page ARTICLE I- StockholdersShareholders 31 Section 1.1 Place and Conduct of Meetings 31 Section 1.2 Annual Meetings 31 Section 1.3 Special Meetings 31 Section 1.4 Notice of Meetings 32 Section 1.5 Quorum of StockholdersShareholders 42 Section 1.6 Adjournments 42 Section 1.7 Votes and Proxies

PART II INFORMATION NOT REQUIRED IN PROSPECTUS

Exhibit 99.1 PART II INFORMATION NOT REQUIRED IN PROSPECTUS Item 14. Other Expenses of Issuance and Distribution. The following table sets forth estimates of the various expenses, other than any underwriting discounts and commissions, in connection with the sale and distribution of the securities being registered. Securities and Exchange Commission Registration Fee $ 41,188 Printing and related ex

Calculation of Filing Fee Tables (Form Type) ImmunoGen, Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities

EX-FILING FEES 2 tm2314503d4ex-filingfees.htm EX-FILING FEES Exhibit 107 Calculation of Filing Fee Tables 424(b)(5) (Form Type) ImmunoGen, Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Fee Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Ag

Underwriting Agreement dated May 4, 2023 by and among ImmunoGen, Inc. and Jefferies LLC, Goldman Sachs & Co. LLC and Guggenheim Securities, LLC, as representatives of the several underwriters named in Schedule 1 thereto

Exhibit 1.1 ImmunoGen, Inc. 26,000,000 Shares of Common Stock, par value $.01 per share Underwriting Agreement May 4, 2023 JEFFERIES LLC GOLDMAN SACHS & CO. LLC GUGGENHEIM SECURITIES, LLC As Representatives of the several Underwriters listed in Schedule 1 hereto c/o Jefferies LLC 520 Madison Avenue New York, New York 10022 c/o Goldman Sachs & Co. LLC 200 West Street New York, New York 10282 c/o Gu

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 4, 2023 ImmunoGen, Inc. (Exac

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 4, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File Num

26,000,000 shares of common stock

 Filed pursuant to Rule 424(b)(5)  Registration No. 333-251502 PROSPECTUS SUPPLEMENT (to Prospectus dated December 18, 2020) 26,000,000 shares of common stock We are offering 26,000,000 shares of our common stock. Our common stock is listed on The Nasdaq Global Select Market under the symbol “IMGN.” On May 2, 2023, the last reported sale price of our common stock on The Nasdaq Global Select Market

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 3, 2023 ImmunoGen, Inc. (Exac

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 3, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File Num

SUBJECT TO COMPLETION, DATED MAY 3, 2023

TABLE OF CONTENTS The information in this preliminary prospectus supplement is not complete and may be changed.

Demonstrates Overall Survival Benefit in the Phase 3 MIRASOL Trial in Patients with FRα-Positive Platinum-Resistant Ovarian Cancer

Exhibit 99.1 ELAHERE® Demonstrates Overall Survival Benefit in the Phase 3 MIRASOL Trial in Patients with FRα-Positive Platinum-Resistant Ovarian Cancer Results Show Statistically Significant Improvements in PFS, ORR, and OS Compared to Chemotherapy First Medicine to Demonstrate an Overall Survival Advantage in Platinum-Resistant Ovarian Cancer Submission of MAA in Europe and sBLA in US Anticipate

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Entry into a Material Definitive Agreement, Material Modification to Rights of Security Holders, Unregistered Sales of Equity Securities, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 1, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File Num

Articles of Amendment.

Exhibit 3.1 The Commonwealth of Massachusetts William Francis Galvin Secretary of the Commonwealth One Ashburton Place, Boston, Massachusetts 02108-1512 Articles of Amendment (General Laws Chapter 156D, Section 10.06; 950 CMR 113.34) (1) Exact name of corporation: ImmunoGen, Inc. (2) Registered office address: Corporation Service Company, 84 State Street, Boston, MA 02109 (number, street, city or

Exchange Agreement, dated May 1, 2023, by and among ImmunoGen, Inc. and RA Capital Healthcare Fund, L.P.

Exhibit 10.1 May 1, 2023 ImmunoGen, Inc. 830 Winter Street Waltham, MA 02451 Attn: Mark J. Enyedy, Chief Executive Officer Re: 3(a)(9) Exchange Agreement Ladies and Gentlemen: This letter agreement (the “Agreement”) confirms the agreement of ImmunoGen, Inc. (the “Company”) and the holder of the Common Stock, par value $.01 per share, of the Company (the “Common Stock”) listed on Schedule I attache

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables FORM S-8 (Form Type) IMMUNOGEN, INC. (Exact name of registrant as specified in its charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price per Unit(2) Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, $.01 par value

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): April 28, 2023 ImmunoGen, Inc. (E

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): April 28, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ImmunoGen Reports Recent Progress and First Quarter 2023 Financial Results Strong Adoption of ELAHERE; Net Sales of $29.5 Million in First Full Quarter of Launch Top-Line Results from Confirmatory MIRASOL Trial Anticipated in Early May; Expected to Support Full Approval of ELAHERE in the US and Expansion into Europe Announced Non-Dilutive Financing for Up to $175 Million to Strengthen

License and Option Agreement dated as of February 28, 2023 by and between ImmunoGen, Inc. and Vertex Pharmaceuticals Incorporated

Exhibit 10.1 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Triple asterisks denote omissions. LICENSE AND OPTION AGREEMENT By and between IMMUNOGEN, INC. AND VERTEX PHARMACEUTICALS INCORPORATED TABLE OF CONTENTS ARTICLE 1 DEFINITIONS 1 ARTICLE 2 RESEARC

Loan Agreement, dated as of April 6, 2023, by and among ImmunoGen, Inc. as the borrower, and certain subsidiaries of the Company party thereto from time to time, as guarantors, BPCR Limited Partnership, as a lender, BioPharma Credit Investments V (Master) LP, as a lender, and BioPharma Credit PLC, as collateral agent for the lenders

Exhibit 10.2 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Triple asterisks denote omissions. LOAN AGREEMENT Dated as of April 6, 2023 among IMMUNOGEN, INC. (as Borrower, and a Credit Party), THE GUARANTORS SIGNATORY HERETO OR OTHERWISE PARTY HERETO FRO

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables FORM S-8 (Form Type) IMMUNOGEN, INC. (Exact name of registrant as specified in its charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price per Unit(2) Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, $.01 par value

As filed with the Securities and Exchange Commission on April 28, 2023

As filed with the Securities and Exchange Commission on April 28, 2023 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 OR ☐ 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 0-17999 Immun

As filed with the Securities and Exchange Commission on April 28, 2023

As filed with the Securities and Exchange Commission on April 28, 2023 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ⌧ Filed by a Party other than the Registrant ◻ Check the appropriate box: ◻ Preliminary Proxy Statement ◻ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ◻ Defin

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ⌧ Filed by a Party other than the Registrant ◻ Check the appropriate box: ◻ Preliminary Proxy Statement ◻ Confidential, for Use of the Commission Only (as permitted by Rule 14

Regulation FD Disclosure, Entry into a Material Definitive Agreement, Financial Statements and Exhibits, Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): April 6, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File N

ImmunoGen Announces Non-Dilutive Term Loan Financing for Up to $175 Million with Pharmakon Advisors

ImmunoGen Announces Non-Dilutive Term Loan Financing for Up to $175 Million with Pharmakon Advisors ImmunoGen to Receive $75 Million Upon Execution of the Agreement; Eligible to Receive up to an Additional $100 Million in Near-Term Proceeds Waltham, MA – April 6, 2023 – ImmunoGen, Inc.

Offer Letter dated as of December 29, 2022 between the Registrant and Michael J. Vasconcelles

Exhibit 10.23 November 12, 2022 Michael J. Vasconcelles Dear Mike: I am delighted to offer you the full-time position of Executive Vice President, Research, Development, and Medical Affairs at ImmunoGen, Inc. (“ImmunoGen” or the “Company”). This offer is made based on the following terms: 1. Reporting. Your role as the Executive Vice President, Research, Development, and Medical Affairs. This is a

Form of Restricted Stock Unit Agreement (Inducement Plan), as amended February 3, 2023

‌Exhibit 10.27(b) IMMUNOGEN, INC. RESTRICTED STOCK UNIT TERMS AND CONDITIONS The following supplements the Grant Detail (the “Grant Detail”) to which these Restricted Stock Unit Terms and Conditions apply, and together with the Grant Detail, constitutes the “Restricted Stock Unit Agreement” referenced in the Grant Detail. This Restricted Stock Unit Agreement is entered into and made effective as o

First Amendment to Offer Letter dated as of December 29, 2022 between the Registrant and Michael J. Vasconcelles

Exhibit 10.23(a) December 7, 2022 Michael J. Vasconcelles Re: First Amendment to Offer Letter Dear Mike: Further to our conversation and in reference to the terms of your Offer Letter dated November 12, 2022 (the “Offer Letter”), this First Amendment to the Offer Letter (the “First Amendment”) sets out the understanding between us and modifications to the Offer Letter as follows: 1. Unless otherwi

Form of Restricted Stock Unit Agreement for Non-Employee Directors as of December 15, 2022

Exhibit 10.12(f) RESTRICTED STOCK UNIT AGREEMENT FOR NON-EMPLOYEE DIRECTORS UNDER THE IMMUNOGEN, INC. AMENDED AND RESTATED 2018 EMPLOYEE, DIRECTOR AND CONSULTANT EQUITY INCENTIVE PLAN Name of Grantee: [•] No. of Restricted Stock Units Granted: [•] Grant Date: [•] This agreement (this “Agreement”) evidences an award (the “Award”) of restricted stock units granted by ImmunoGen, Inc. (the “Company”)

Form of Restricted Stock Unit Agreement under the 2018 Plan, as amended February 3, 2023

Exhibit 10.12(c) Form of Restricted Stock Unit Agreement IMMUNOGEN, INC. RESTRICTED STOCK UNIT TERMS AND CONDITIONS The following supplements the Grant Detail (the “Grant Detail”) to which these Restricted Stock Unit Terms and Conditions apply, and together with the Grant Detail, constitutes the “Restricted Stock Unit Agreement” referenced in the Grant Detail. This Restricted Stock Unit Agreement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the year ended December 31, 2022 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the period from to Commission file number 0-17999 ImmunoGen, Inc. Massachusett

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 1, 2023 ImmunoGen, Inc. (Ex

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): March 1, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File N

Change in Control Severance Agreement dated as of December 29, 2022 between the Registrant and Michael J. Vasconcelles

Exhibit 10.20 ADDENDUM A TO MICHAEL J. VASCONCELLES OFFER LETTER CHANGE IN CONTROL SEVERANCE AGREEMENT This Agreement is entered into as of the 29th day of December, 2022 (the “Effective Date”) by and between ImmunoGen, Inc., a Massachusetts corporation (the “Company”), and Michael Vasconcelles (the “Executive”). WHEREAS, the Company recognizes that the Executive’s service to the Company is very i

Description of Securities

Exhibit 4.3 DESCRIPTION OF THE REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 ImmunoGen, Inc. (“ImmunoGen,” “we,” “us” or the “Company”) has one class of securities registered under Section 12 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”): common stock, $.01 par value per share (“Common Stock”). The Common Stock is listed

Change in Control Severance Agreement dated as of January 5, 2021 between the Registrant and Renee Lentini

‌Exhibit 10.19 CHANGE IN CONTROL SEVERANCE AGREEMENT This Agreement is entered into as of the 5th day of January, 2021 (the “Effective Date”) by and between ImmunoGen, Inc., a Massachusetts corporation (the “Company”), and Renee Lentini (the “Executive”). WHEREAS, the Company recognizes that the Executive’s service to the Company is very important to the future success of the Company; WHEREAS, the

Inducement Equity Incentive Plan, as amended December 15, 2022

‌Exhibit 10.27 IMMUNOGEN, INC. INDUCEMENT EQUITY INCENTIVE PLAN, AS AMENDED 1.DEFINITIONS. Unless otherwise specified or unless the context otherwise requires, the following terms, as used in this ImmunoGen, Inc. Inducement Equity Incentive Plan, have the following meanings: Administrator means the Board of Directors, unless it has delegated power to act on its behalf to the Committee, in which ca

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 28, 2023 ImmunoGen, Inc.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): February 28, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fi

Compensation Policy for Non-Employee Directors, as amended through December 15, 2022

Exhibit 10.24 ImmunoGen, Inc. Compensation Policy for Non-Employee Directors (Effective December 15, 2022) Objective It is the objective of ImmunoGen, Inc. to compensate non-employee members (each, a “Director”) of the Board of Directors (the “Board”) in a manner that will enable the recruitment and retention of highly qualified Directors by fairly compensating them for their services as Directors

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ImmunoGen Reports Recent Progress and 2022 Financial Results Launched ELAHERE™ (mirvetuximab soravtansine-gynx), the First and Only ADC Approved for Platinum-Resistant Ovarian Cancer in the US; ELAHERE Monotherapy and in Combination with Bevacizumab Included in NCCN Guidelines and Compendium Top-Line Results from Confirmatory MIRASOL Trial Anticipated in Q2 2023; Expected to Support F

Form of Non-Qualified Stock Option Agreement for Non-Employee Directors, as amended December 15, 2022

Exhibit 10.12(d) Form of Director Option Agreement IMMUNOGEN, INC. NON-QUALIFIED STOCK OPTION TERMS AND CONDITIONS The following supplements the Grant Detail (the “Grant Detail”) to which these Non-Qualified Stock Option Terms and Conditions apply, and together with the Grant Detail, constitutes the “Option Agreement” referenced in the Grant Detail. This Option Agreement is entered into and made e

Subsidiaries of the Registrant

Exhibit 21 SUBSIDIARIES Name Jurisdiction of Organization Hurricane, LLC Massachusetts ImmunoGen US Holding, Inc. Delaware ImmunoGen Europe Limited United Kingdom ImmunoGen Switzerland GmbH Switzerland ImmunoGen BioPharma (Ireland) Limited Ireland ImmunoGen Securities Corp. Massachusetts

ImmunoGen Announces a Global, Multi-Target License and Option Agreement with Vertex for the Use of ImmunoGen's ADC Technology in the Development of Novel Targeted Conditioning Agents

ImmunoGen Announces a Global, Multi-Target License and Option Agreement with Vertex for the Use of ImmunoGen's ADC Technology in the Development of Novel Targeted Conditioning Agents ImmunoGen to Receive a $15 Million Upfront Payment; Eligible to Receive Up to $337 Million in Potential Option Fees and Milestone Payments Plus Tiered Royalties on a Per Target Basis Waltham, MA – March 1, 2023 – ImmunoGen, Inc.

2004 Non-Employee Director Compensation and Deferred Stock Unit Plan, as amended and restated on December 15, 2022

Exhibit 10.15 IMMUNOGEN, INC. 2004 NON-EMPLOYEE DIRECTOR COMPENSATION AND DEFERRED SHARE UNIT PLAN (amended and restated effective as of December 15, 2022) WHEREAS, the Board of Directors (the “Board”) of ImmunoGen, Inc. (the “Company”) previously established the ImmunoGen, Inc. 2004 Non-Employee Director Compensation and Deferred Share Unit Plan (as amended from time to time, the “Plan”), initial

IMGN / ImmunoGen, Inc. / RA CAPITAL MANAGEMENT, L.P. - SC 13G/A Passive Investment

SC 13G/A 1 tm236221d36sc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 2)* ImmunoGen, Inc. (Name of Issuer) Common Stock, $0.01 par value per share (Title of Class of Securities) 45253H101 (CUSIP Number) December 31, 2022 (Date of Event Which Requires Filing of this Statement) Check t

Joint Filing Agreement

EX-99.1 2 tm236041d7ex99-1.htm EXHIBIT 99.1 Exhibit 99.1 Joint Filing Agreement In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), the undersigned hereby agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto, the “Schedule 13G”) relating to the Common Stock, $0.01 par

IMGN / ImmunoGen, Inc. / Redmile Group, LLC - SC 13G/A Passive Investment

IMGN / ImmunoGen, Inc. / Flynn James E Passive Investment

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULES 13d-1(b)(c), AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2(b) (Amendment No.

IMGN / ImmunoGen, Inc. / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 5)* Name of issuer: ImmunoGen Inc. Title of Class of Securities: Common Stock CUSIP Number: 45253H101 Date of Event Which Requires Filing of this Statement: December 30, 2022 Check the appropriate box to designate the rule pursuant to which this Schedule is filed: ☒ Rule

IMGN / ImmunoGen, Inc. / WELLINGTON MANAGEMENT GROUP LLP - SEC SCHEDULE 13G Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 3 )* ImmunoGen, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45253H101 (CUSIP Number) December 30, 2022 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedu

2 FORWARD - LOOKING STATEMENTS This presentation includes forward - looking statements regarding ImmunoGen’s current expectations related to : the commercialization of ELAHERE, the design and potential success of 420 study, pivekimab sunirine, IMGC 9

EX-99.1 2 imgn-20230109xex99d1.htm EX-99.1 Exhibit 99.1 1 TARGET A BETTER NOW JP Morgan Healthcare Conference January 9 - 12, 2023 Nasdaq: IMGN 2 FORWARD - LOOKING STATEMENTS This presentation includes forward - looking statements regarding ImmunoGen’s current expectations related to : the commercialization of ELAHERE, the design and potential success of 420 study, pivekimab sunirine, IMGC 936 , a

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 9, 2023 ImmunoGen, Inc. (

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 9, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File

ImmunoGen Appoints Michael Vasconcelles, MD, as Executive Vice President, Research, Development, and Medical Affairs

ImmunoGen Appoints Michael Vasconcelles, MD, as Executive Vice President, Research, Development, and Medical Affairs Waltham, MA – January 4, 2023 – ImmunoGen, Inc.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 4, 2023 ImmunoGen, Inc. (

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 4, 2023 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 23, 2022 ImmunoGen, Inc.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 23, 2022 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fi

ImmunoGen Announces Susan Altschuller on FMLA Leave; Interim CFO Appointed

EX-99.1 2 imgn-20221223xex99d1.htm EX-99.1 ImmunoGen Announces Susan Altschuller on FMLA Leave; Interim CFO Appointed Waltham, MA – December 28, 2022 – ImmunoGen, Inc. (Nasdaq: IMGN), a leader in the expanding field of antibody-drug conjugates (ADCs) for the treatment of cancer, today announced that Susan Altschuller, PhD, Senior Vice President and Chief Financial Officer (CFO), is on leave under

IMGN / ImmunoGen, Inc. / ADAGE CAPITAL PARTNERS GP, L.L.C. - IMMUNOGEN, INC. Passive Investment

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) December 15, 2022 (Date of Event Which Requires Filing of This Statement) Check the appropriate box to designate the rule pursuant to which

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 14, 2022 ImmunoGen, Inc.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 14, 2022 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fi

ImmunoGen Announces FDA Accelerated Approval of ELAHERE™ (mirvetuximab soravtansine-gynx) for the Treatment of Platinum-Resistant Ovarian Cancer

Exhibit 99.1 ImmunoGen Announces FDA Accelerated Approval of ELAHERE™ (mirvetuximab soravtansine-gynx) for the Treatment of Platinum-Resistant Ovarian Cancer ELAHERE is the First ADC Approved by FDA for Platinum-Resistant Ovarian Cancer Indication Covers Patients with One to Three Prior Systemic Treatment Regimens, Regardless of Prior Avastin® Use VENTANA FOLR1 (FOLR1-2.1) RxDx Assay, the Companio

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents ? ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 4, 2022 ImmunoGen, Inc.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 4, 2022 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ? ImmunoGen Reports Recent Progress and Third Quarter 2022 Financial Results ? Launch Preparations Completed Ahead of November 28, 2022 PDUFA Date ? Presentations at ESMO, IGCS, and ESGO Highlight Mirvetuximab?s Potential to Become New Standard of Care and Combination Agent of Choice in FR?-Positive Ovarian Cancer ? Initial Data from Pivotal Phase 2 CADENZA Study Demonstrated Encourag

ImmunoGen Announces Departure of Chief Commercial Officer

Exhibit 99.1 ImmunoGen Announces Departure of Chief Commercial Officer Waltham, MA – November 1, 2022 – ImmunoGen, Inc. (Nasdaq: IMGN), a leader in the expanding field of antibody-drug conjugates (ADCs) for the treatment of cancer, today announced that Kristen Harrington-Smith, Senior Vice President and Chief Commercial Officer (CCO), will be departing the Company. Ms. Harrington-Smith is leaving

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): October 26, 2022 ImmunoGen, Inc.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): October 26, 2022 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

ImmunoGen Provides Update on Pivotal CADENZA Study of Pivekimab Sunirine in Frontline Blastic Plasmacytoid Dendritic Cell Neoplasm

Exhibit 99.1 ImmunoGen Provides Update on Pivotal CADENZA Study of Pivekimab Sunirine in Frontline Blastic Plasmacytoid Dendritic Cell Neoplasm Review of Data from First 10 Patients Demonstrates Significant Activity and Favorable Tolerability in Both De Novo BPDCN Patients and Those with a Prior or Concomitant Hematologic Malignancy (PCHM) Following Discussion with FDA, CADENZA Patients to be Segm

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 31, 2022 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents ? ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables FORM S-8 (Form Type) IMMUNOGEN, INC. (Exact name of registrant as specified in its charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price per Unit(2) Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, $.01 par value

As filed with the Securities and Exchange Commission on August 1, 2022

As filed with the Securities and Exchange Commission on August 1, 2022 Registration No.

Articles of Amendment

Exhibit 3.1(d) ? ? ? William Francis Galvin Secretary of the Commonwealth One Ashburton Place, Boston, Massachusetts 02108-1512 ? ? ? FORM MUST BE TYPED Articles of Amendment FORM MUST BE TYPED ? (General Laws Chapter 156D, Section 10.06; 950 CMR 113.34) ? ? (1) Exact name of corporation: ImmunoGen, Inc. ? ? (2) Registered o?ce address: CORPORATION SERVICE COMPANY, 84 STATE STREET, BOSTON, MA 0210

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables FORM S-8 (Form Type) IMMUNOGEN, INC. (Exact name of registrant as specified in its charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price per Unit(2) Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, $.01 par value

As filed with the Securities and Exchange Commission on August 1, 2022

As filed with the Securities and Exchange Commission on August 1, 2022 Registration No.

Inducement Equity Incentive Plan, as amended

Exhibit 10.1 IMMUNOGEN, INC. ? INDUCEMENT EQUITY INCENTIVE PLAN, AS AMENDED ? ? ? 1.DEFINITIONS. ? Unless otherwise specified or unless the context otherwise requires, the following terms, as used in this ImmunoGen, Inc. Inducement Equity Incentive Plan, have the following meanings: ? Administrator means the Board of Directors, unless it has delegated power to act on its behalf to the Committee, i

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION ? Washington, D.C. 20549 ? FORM 8-K ? CURRENT REPORT ? PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ? Date of Report (Date of earliest event reported): July 29, 2022 ? ImmunoGen, Inc. (Exact name of registrant as specified in its charter) ? ? ? ? ? ? ? Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorpo

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ? ImmunoGen Reports Recent Progress and Second Quarter 2022 Financial Results ? BLA for Mirvetuximab Soravtansine Monotherapy in Ovarian Cancer Accepted by FDA with Priority Review; PDUFA Date Set for November 28, 2022 ? Completed enrollment in the Confirmatory MIRASOL Study ? Presented Additional Efficacy and Safety Data for Mirvetuximab Monotherapy at ASCO; Poster Highlighting Updat

Amended and Restated 2018 Employee, Director and Consultant Equity Incentive Plan

Exhibit 10.1 IMMUNOGEN, INC. AMENDED AND RESTATED 2018 EMPLOYEE, DIRECTOR AND CONSULTANT EQUITY INCENTIVE PLAN 1. DEFINITIONS. Unless otherwise specified or unless the context otherwise requires, the following terms, as used in this ImmunoGen, Inc. 2018 Employee, Director and Consultant Equity Incentive Plan, have the following meanings: Administrator means the Board of Directors, unless it has de

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): June 15, 2022 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File N

ImmunoGen Announces Acceptance of Biologics License Application for Mirvetuximab Soravtansine in Ovarian Cancer by US Food and Drug Administration with Priority Review

Exhibit 99.1 ImmunoGen Announces Acceptance of Biologics License Application for Mirvetuximab Soravtansine in Ovarian Cancer by US Food and Drug Administration with Priority Review PDUFA Date is November 28, 2022 Waltham, MA ? May 23, 2022 ? ImmunoGen, Inc. (Nasdaq: IMGN), a leader in the expanding field of antibody-drug conjugates (ADCs) for the treatment of cancer, today announced that the US Fo

Regulation FD Disclosure, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): May 20, 2022 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File Nu

IMGN / ImmunoGen, Inc. / Flynn James E Passive Investment

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULES 13d-1(b)(c), AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2(b) (Amendment No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents ? ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ? ImmunoGen Reports Recent Progress and First Quarter 2022 Financial Results ? Submitted BLA for Mirvetuximab Soravtansine Monotherapy to FDA Under Accelerated Approval Pathway; Commercial Preparations Underway ? Presented Results from Positive Pivotal SORAYA Trial of Mirvetuximab Soravtansine in Ovarian Cancer in Plenary Session at SGO Annual Meeting; Additional Efficacy and Safety D

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION ? Washington, D.C. 20549 ? FORM 8-K ? CURRENT REPORT ? PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ? Date of Report (Date of earliest event reported): May 6, 2022 ? ImmunoGen, Inc. (Exact name of registrant as specified in its charter) ? ? ? ? ? ? ? Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorpora

License Agreement as of February 14, 2022 by and between the Registrant and Eli Lilly and Company

Exhibit 10.1 Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Triple asterisks denote omissions. LICENSE AGREEMENT by and between IMMUNOGEN, INC. AND Eli Lilly and Company ? ? ? ? TABLE OF CONTENTS Article 1 DEFINITIONS?1 Article 2 TARGET SELECTION?15 2.1P

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) ? ? Filed by the Registrant ? ? Filed by a Party other than the Registrant ? ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

definitive proxy statement on Schedule 14A filed on April 26, 2022

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ? ? Filed by a Party other than the Registrant ? ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rul

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ? ? Filed by a Party other than the Registrant ? ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rul

IMGN / ImmunoGen, Inc. / ADAGE CAPITAL PARTNERS GP, L.L.C. - IMMUNOGEN, INC. Passive Investment

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) March 23, 2022 (Date of Event Which Requires Filing of This Statement) Check the appropriate box to designate the rule pursuant to which thi

Compensation Policy for Non-Employee Directors, as amended through December 16, 2021

? Exhibit 10.24 ? ImmunoGen, Inc. Compensation Policy for Non-Employee Directors (Effective December 16, 2021) Objective It is the objective of ImmunoGen to compensate non-employee Directors in a manner which will enable recruitment and retention of highly qualified Directors and fairly compensate them for their services as a Director. Cash Compensation Annual meeting fee for non-employee Director

Development and License Agreement with Biogen Idec., Inc. dated October 1, 2006

Exhibit 10.9 ? Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Triple asterisks denote omissions. ? DEVELOPMENT AND LICENSE AGREEMENT ? This Development and License Agreement (this ?Agreement?) is made effective as of October 1, 2004 (the ?Effective Date?

First Amendment to Agreements dated as of December 9, 2013 by and between the Registrant and Eli Lilly and Company

? ? Exhibit 10.8 ? Certain identified information has been excluded from the exhibit because it is both (i) not material and (ii) is the type of information that the registrant treats as private or confidential. Triple asterisks denote omissions. ? FIRST AMENDMENT TO AGREEMENTS ? This First Amendment to Agreements (the ?First Amendment?) is made effective as of the date of the last signature below

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 10-K

Table of Contents ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

Change in Control Severance Agreement dated November 15, 2021 between the Registrant and Kristen Harrington-Smith

Exhibit 10.23 CHANGE IN CONTROL SEVERANCE AGREEMENT This Agreement is entered into as of the 15th day of November, 2021 (the ?Effective Date?) by and between ImmunoGen, Inc., a Massachusetts corporation (the ?Company?), and Kristen Harrington-Smith (the ?Executive?). WHEREAS, the Company recognizes that the Executive?s service to the Company is very important to the future success of the Company;

Subsidiaries of the Registrant

Exhibit 21 SUBSIDIARIES ? ? Name Jurisdiction of Organization Hurricane, LLC Massachusetts ImmunoGen BioPharma (Ireland) Limited Ireland ImmunoGen Europe Limited United Kingdom ImmunoGen Securities Corp. Massachusetts ?

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION ? Washington, D.C. 20549 ? FORM 8-K ? CURRENT REPORT ? PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ? Date of Report (Date of earliest event reported): February 25, 2022 ? ImmunoGen, Inc. (Exact name of registrant as specified in its charter) ? ? ? ? ? ? ? Massachusetts 0-17999 04-2726691 (State or other jurisdiction of inc

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ? ImmunoGen Reports Recent Progress and 2021 Financial Results ? Positive Top-Line Data from Pivotal SORAYA Trial of Mirvetuximab Soravtansine in Ovarian Cancer; Detailed Results to be Presented in Plenary Session at SGO in March ? Mirvetuximab BLA On Track for Submission this Quarter ? IMGN632 Triplet Data Demonstrating Manageable Safety Profile and Encouraging Activity in AML Highli

Regulation FD Disclosure, Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION ? Washington, D.C. 20549 ? FORM 8-K ? CURRENT REPORT ? PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ? Date of Report (Date of earliest event reported): February 14, 2022 ? ImmunoGen, Inc. (Exact name of registrant as specified in its charter) ? ? ? ? ? ? ? Massachusetts 0-17999 04-2726691 ? ? (State or other jurisdiction of

ImmunoGen Announces a Global, Multi-Target License Agreement of its Novel Camptothecin ADC Platform to Lilly for Up to $1.7 Billion

EX-99.1 2 imgn-20220214xex99d1.htm EX-99.1 Exhibit 99.1 ImmunoGen Announces a Global, Multi-Target License Agreement of its Novel Camptothecin ADC Platform to Lilly for Up to $1.7 Billion ImmunoGen Grants Lilly Exclusive Rights to Research, Develop, and Commercialize Antibody-Drug Conjugates Combining Targets Selected by Lilly with ImmunoGen's Novel Camptothecin Platform ImmunoGen to Receive a $13

IMGN / ImmunoGen, Inc. / Redmile Group, LLC - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 4) IMMUNOGEN, INC. (Name of Issuer) Common Stock, $0.01 par value (Title of Class of Securities) 45253H101 (CUSIP Number) December 31, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to

IMGN / ImmunoGen, Inc. / RA CAPITAL MANAGEMENT, L.P. - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 1)* ImmunoGen, Inc. (Name of Issuer) Common Stock, par value $0.01 per share (Title of Class of Securities) 45253H101 (CUSIP Number) December 31, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule p

Joint Filing Agreement

Exhibit 99.1 Joint Filing Agreement In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended (the ?Exchange Act?), the undersigned hereby agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto, the ?Schedule 13G?) relating to the Common Stock, $0.01 par value per share, of ImmunoGen, Inc., which

IMGN / ImmunoGen, Inc. / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 4)* Name of issuer: ImmunoGen Inc. Title of Class of Securities: Common Stock CUSIP Number: 45253H101 Date of Event Which Requires Filing of this Statement: December 31, 2021 Check the appropriate box to designate the rule pursuant to which this Schedule is filed: ??Rule

CONFIDENTIAL1 TARGET A BETTER NOW JP Morgan Healthcare ConferenceJanuary 10-13, 2022NASDAQ: IMGN CONFIDENTIAL2 FORWARD-LOOKING STATEMENTS Thispresentationincludesforward-lookingstatementsregardingImmunoGen’scurrentexpectationsrelatedto:thedesignandpo

Exhibit 99.1 CONFIDENTIAL1 TARGET A BETTER NOW JP Morgan Healthcare ConferenceJanuary 10-13, 2022NASDAQ: IMGN CONFIDENTIAL2 FORWARD-LOOKING STATEMENTS Thispresentationincludesforward-lookingstatementsregardingImmunoGen?scurrentexpectationsrelatedto:thedesignandpotentialsuccessofImmunoGen?smirvetuximabsoravtansine,IMGN632,IMGC936,andIMGN151preclinicalandclinicalstudiesandregulatorypathways,includin

Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION ? Washington, D.C. 20549 ? FORM 8-K ? CURRENT REPORT ? PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ? Date of Report (Date of earliest event reported): January 10, 2022 ? ImmunoGen, Inc. (Exact name of registrant as specified in its charter) ? ? ? ? ? ? ? Massachusetts 0-17999 04-2726691 ? ? (State or other jurisdiction of

IMGN / ImmunoGen, Inc. / WELLINGTON MANAGEMENT GROUP LLP - SEC SCHEDULE 13G Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 2 )* ImmunoGen, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45253H101 (CUSIP Number) December 31, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedu

The following is a supplement (the “Supplement”) to the description of the business of ImmunoGen, Inc. (the “Company”) included in the Company’s reports filed with the Securities and Exchange Commission pursuant to the Securities Exchange Act of 1934

EXHIBIT 99.2 The following is a supplement (the ?Supplement?) to the description of the business of ImmunoGen, Inc. (the ?Company?) included in the Company?s reports filed with the Securities and Exchange Commission pursuant to the Securities Exchange Act of 1934, as amended (the ?Exchange Act?). The Supplement should not be read in isolation and should be read together with the description of the

Underwriting Agreement dated December 1, 2021 by and among ImmunoGen, Inc. and Jefferies LLC and Cowen and Company, LLC, as representatives of the several underwriters named in Schedule 1 thereto

EXHIBIT 1.1 ImmunoGen, Inc. 11,636,364 Shares of Common Stock, par value $0.01 per share Pre-Funded Warrants to Purchase 27,363,636 Shares of Common Stock Underwriting Agreement December 1, 2021 JEFFERIES LLC COWEN AND COMPANY, LLC As Representatives of the several Underwriters listed in Schedule 1 hereto c/o Jefferies LLC 520 Madison Avenue New York, New York 10022 c/o Cowen and Company, LLC 599

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 1, 2021 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

PART II INFORMATION NOT REQUIRED IN PROSPECTUS

Exhibit 99.1 PART II INFORMATION NOT REQUIRED IN PROSPECTUS Item 14. Other Expenses of Issuance and Distribution. The following table sets forth estimates of the various expenses, other than any underwriting discounts and commissions, in connection with the sale and distribution of the securities being registered. Securities and Exchange Commission Registration Fee $ 27,440 Printing and related ex

Form of Pre-Funded Warrant issued December 6, 2021

Exhibit 4.1 IMMUNOGEN, INC. PRE-FUNDED WARRANT TO PURCHASE COMMON STOCK Number of Shares: [?] (subject to adjustment) Warrant No. [?] Original Issue Date: December 6, 2021 ImmunoGen, Inc., a Massachusetts corporation (the ?Company?), hereby certifies that, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, [?] or its permitted registered assigns (the

CALCULATION OF REGISTRATION FEE?

TABLE OF CONTENTS As Filed Pursuant to 424(b)(5) Registration No. 333-251502? ? CALCULATION OF REGISTRATION FEE? ? ? Title of Each Class Securities to be Registered ? ? ? Amount to be Registered ? ? ? Proposed Maximum Offering Price Per Share ? ? ? Proposed Maximum Aggregate Offering Price ? ? ? Amount of Registration Fee(1) ? ? Common Stock, $0.01 par value ? ? ? ? ? 44,850,000(2) ? ? ? ? ? $ 6.6

Risk Factor Update

EXHIBIT 99.3 Risk Factor Update An investment in our common stock involves a high degree of risk. Before deciding whether to invest in our common stock, you should consider carefully the risks described below and discussed under the section captioned ?Risk Factors? contained in our Annual Report on Form 10-K for the year ended December 31, 2020, as filed with the Securities and Exchange Commission

Issuer Free Writing Prospectus

Issuer Free Writing Prospectus Filed Pursuant to Rule 433 Dated December 1, 2021 Relating to Preliminary Prospectus Supplement Dated November 30, 2021 Registration Statement No.

ImmunoGen Announces Positive Top-Line Results from Pivotal SORAYA Trial of Mirvetuximab Soravtansine in Ovarian Cancer

Exhibit 99.1 ImmunoGen Announces Positive Top-Line Results from Pivotal SORAYA Trial of Mirvetuximab Soravtansine in Ovarian Cancer Trial Met Primary Endpoint with Confirmed Objective Response Rate of 32.4% Median Duration of Response at Data Cutoff is 5.9 Months Continued Demonstration of Favorable Tolerability Profile BLA Submission on Track for First Quarter of 2022 Conference Call to be Held a

Regulation FD Disclosure, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 30, 2021 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fi

$175,000,000? Common stock?

TABLE OF CONTENTS The information in this preliminary prospectus supplement is not complete and may be changed.

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

UNITED STATES SECURITIES AND EXCHANGE COMMISSION ? Washington, D.C. 20549 ? FORM 8-K ? CURRENT REPORT ? PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ? Date of Report (Date of earliest event reported): November 15, 2021 ? ImmunoGen, Inc. (Exact name of registrant as specified in its charter) ? ? ? ? ? ? ? Massachusetts 0-17999 04-2726691 ? ? (State or other jurisdiction of

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): October 29, 2021 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ? ImmunoGen Reports Recent Progress and Third Quarter 2021 Financial Results ? Top-Line Data from Pivotal SORAYA Trial Evaluating Mirvetuximab Soravtansine in Platinum-Resistant Ovarian Cancer on Track for Release this Quarter ? IMGN632 AML Combination Data to be Highlighted at ASH Annual Meeting ? PICCOLO, Single-Arm Study of Mirvetuximab in Platinum-Sensitive Ovarian Cancer, Open fo

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents ? ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

UNITED STATES SECURITIES AND EXCHANGE COMMISSION ? Washington, D.C. 20549 ? FORM 8-K ? CURRENT REPORT ? PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ? Date of Report (Date of earliest event reported): September 22, 2021 ? ImmunoGen, Inc. (Exact name of registrant as specified in its charter) ? ? ? ? ? ? ? Massachusetts 0-17999 04-2726691 ? ? (State or other jurisdiction o

Securities Purchase Agreement dated August 11, 2021 between ImmunoGen, Inc. and RA Capital Healthcare Fund, L.P.

Exhibit 10.1 Execution Version SECURITIES PURCHASE AGREEMENT BETWEEN IMMUNOGEN, INC. AND THE INVESTOR NAMED HEREIN Dated as of AUGUST 11, 2021 This SECURITIES PURCHASE AGREEMENT (this ?Agreement?) is made and entered into this 11th day of August, 2021 by and between ImmunoGen, Inc., a Massachusetts corporation (the ?Company?), and the Person named on the signature page hereto under the heading ?In

CALCULATION OF REGISTRATION FEE

TABLE OF CONTENTS As Filed Pursuant to 424(b)(5) Registration No. 333-251502? CALCULATION OF REGISTRATION FEE ? ? Title of Each Class of Securities to be Registered ? ? ? Amount to be Registered ? ? ? Proposed Maximum Offering Price Per Share ? ? ? Proposed Maximum Aggregate Offering Price ? ? ? Amount of Registration Fee(1) ? Common Stock, $0.01 par value ? ? ? 5,434,782 (2) ? ? ? $5.52 ? ? ? $29

Form of Pre-Funded Warrant issued August 12, 2021

Exhibit 4.1 IMMUNOGEN, INC. PRE-FUNDED WARRANT TO PURCHASE COMMON STOCK Number of Shares: [ ] (subject to adjustment) Warrant No. [ ] Original Issue Date: [ ] ImmunoGen, Inc., a Massachusetts corporation (the ?Company?), hereby certifies that, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, [ ] or its permitted registered assigns (the ?Holder?), i

Regulation FD Disclosure, Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): August 11, 2021 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File

As filed with the Securities and Exchange Commission on August 9, 2021

As filed with the Securities and Exchange Commission on August 9, 2021 Registration No.

As filed with the Securities and Exchange Commission on August 9, 2021

As filed with the Securities and Exchange Commission on August 9, 2021 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents ? ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ? ImmunoGen Reports Recent Progress and Second Quarter 2021 Financial Results ? Compelling Final Data from FORWARD II Study Combining Mirvetuximab Soravtansine with Avastin? in Recurrent Ovarian Cancer, Regardless of Platinum Status, Presented at ASCO ? Top-line Data from Pivotal SORAYA Trial on Track for Q4 Release ? Continued Progress in Ongoing MIRASOL, IMGN632, and IMGC936 Studies

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): July 30, 2021 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File N

Compensation Policy for Non-Employee Directors, as amended through June 16, 2021.

Exhibit 10.2 ImmunoGen, Inc. Compensation Policy for Non-Employee Directors (Effective June 16, 2021) Objective It is the objective of ImmunoGen to compensate non-employee Directors in a manner which will enable recruitment and retention of highly qualified Directors and fairly compensate them for their services as a Director. Cash Compensation Annual meeting fee for non-employee Directors: $40,00

Amended and Restated 2018 Employee Director and Consultant Equity Incentive Plan

Exhibit 10.1 IMMUNOGEN, INC. Amended And Restated 2018 EMPLOYEE, DIRECTOR AND CONSULTANT EQUITY INCENTIVE PLAN 1. DEFINITIONS. Unless otherwise specified or unless the context otherwise requires, the following terms, as used in this ImmunoGen, Inc. 2018 Employee, Director and Consultant Equity Incentive Plan, have the following meanings: Administrator means the Board of Directors, unless it has de

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits, Other Events, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): June 16, 2021 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File N

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant x Filed by a Party other than the Registrant o Check the appropriate box: o Preliminary Proxy Statement o Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) o Defin

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION ? Washington, D.C. 20549 ? FORM 8-K ? CURRENT REPORT ? PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ? Date of Report (Date of earliest event reported): May 10, 2021 ? ImmunoGen, Inc. (Exact name of registrant as specified in its charter) ? ? ? ? ? ? ? Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorpor

Inducement Equity Incentive Plan, as amended

? IMMUNOGEN, INC. ? INDUCEMENT EQUITY INCENTIVE PLAN, AS AMENDED ? ? ? 1.DEFINITIONS. ? Unless otherwise specified or unless the context otherwise requires, the following terms, as used in this ImmunoGen, Inc. Inducement Equity Incentive Plan, have the following meanings: ? Administrator means the Board of Directors, unless it has delegated power to act on its behalf to the Committee, in which cas

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ? ImmunoGen Reports Recent Progress and First Quarter 2021 Financial Results ? Top-Line Data from Pivotal SORAYA Trial of Mirvetuximab Soravtansine in Ovarian Cancer Expected in the Fourth Quarter of 2021 ? FORWARD II Mirvetuximab Plus Avastin? Doublet Cohort in Recurrent Ovarian Cancer, Regardless of Platinum Status, Selected for Oral Presentation at ASCO ? Preclinical Data Demonstra

Quarterly Report - 10-Q

Table of Contents ? ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

- DEFA14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) ? ? Filed by the Registrant ? ? Filed by a Party other than the Registrant ? ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

definitive proxy statement on Schedule 14A filed on April 28, 2021

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ? ? Filed by a Party other than the Registrant ? ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rul

- S-8

As filed with the Securities and Exchange Commission on March 1, 2021 Registration No.

Collaboration and License Agreement effective as of October 19, 2020 by and between the registrant and Hangzhou Zhongmei Huadong Pharmaceutical Co., Ltd., a subsidiary of Huadong Medicine Co., Ltd.

Exhibit 10.6 ? ? [Pursuant to Item 601(b)(10) of Regulation S-K, certain confidential portions of this exhibit have been omitted by means of marking such portions with brackets and asterisks - [***] - as the identified confidential portions (i) are not material and (ii) would be competitively harmful if publicly disclosed.] ? ? ? ? ? ? COLLABORATION AND LICENSE AGREEMENT by and between ImmunoGen,

Description of Securities

? Exhibit 4.3 ? DESCRIPTION OF THE REGISTRANT?S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 ? As of March 1, 2021, ImmunoGen, Inc. (?ImmunoGen,? ?we,? ?us? or the ?Company?) had one class of securities registered under Section 12 of the Securities Exchange Act of 1934, as amended (the ?Exchange Act?): Common Stock, $.01 par value per share (?Common Stock?) .

Subsidiaries of the Registrant

Exhibit 21 SUBSIDIARIES ? ? Name Jurisdiction of Organization Hurricane, LLC Massachusetts ImmunoGen BioPharma (Ireland) Limited Ireland ImmunoGen Europe Limited United Kingdom ImmunoGen Securities Corp. Massachusetts ?

Change in Control Severance Agreement dated as of June 1, 2020 between the Registrant and Stacy Coen

Exhibit 10.19 CHANGE IN CONTROL SEVERANCE AGREEMENT This Agreement is entered into as of the 1st day of June, 2020 (the ?Effective Date?) by and between ImmunoGen, Inc., a Massachusetts corporation (the ?Company?), and Stacy A. Coen (the ?Executive?). WHEREAS, the Company recognizes that the Executive?s service to the Company is very important to the future success of the Company; WHEREAS, the Exe

Annual Report - 10-K

Table of Contents ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

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 (Title of Class of Securities) (CUSIP Nu

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 (Title of Class of Securities) 45253H101 (CUSIP Number) December 31, 2020 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to

UNITED STATES 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) (

UNITED STATES 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) December 31, 2020 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule purs

Joint Filing Agreement

Exhibit 99.1 Joint Filing Agreement In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), the undersigned hereby agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto, the “Schedule 13G”) relating to the Common Stock, $0.01 par value per share, of ImmunoGen, Inc., which

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ImmunoGen Reports Recent Progress and 2020 Financial Results Top-Line Data from Pivotal SORAYA Trial for Mirvetuximab Soravtansine in Ovarian Cancer Expected in Q3 2021; BLA to be Submitted by Year-End Full Approval Pathway for IMGN632 in BPDCN Aligned with FDA; Updated Phase 1/2 Data in BPDCN Presented at ASH Balance Sheet Funds Operations into the Second Half of 2022 Conference Call

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION ? Washington, D.C. 20549 ? FORM 8-K ? CURRENT REPORT ? PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ? Date of Report (Date of earliest event reported): February 12, 2021 ? ImmunoGen, Inc. (Exact name of registrant as specified in its charter) ? ? ? ? ? ? ? Massachusetts 0-17999 04-2726691 (State or other jurisdiction of inc

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 3)*

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 3)* Name of issuer: ImmunoGen Inc. Title of Class of Securities: Common Stock CUSIP Number: 45253H101 Date of Event Which Requires Filing of this Statement: December 31, 2020 Check the appropriate box to designate the rule pursuant to which this Schedule is filed: ☒ Rule

CUSIP NO. 45253H101 13G Page 1 of 7

immu20a12.htm - Generated by SEC Publisher for SEC Filing CUSIP NO. 45253H101 13G Page 1 of 7 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 12)* ImmunoGen, Inc. (Name of Issuer) Common Stock, $.01 par value (Title of Class of Securities) 45253H101 (CUSIP Number) December 31, 2020 (Date of Event Which Re

SCHEDULE 13G

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1 )* ImmunoGen, Inc. (Name of Issuer) Common Stock (Title of Class of Securities) 45253H101 (CUSIP Number) December 31, 2020 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedu

Regulation FD Disclosure, Results of Operations and Financial Condition - 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): January 11, 2021 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

3 POISED TO BECOME A FULLY - INTEGRATED ONCOLOGY COMPANY WITH TWO PRODUCTS ON THE MARKET BY THE END OF 2022 ACCELERATED PATH FOR MIRVETUXIMAB IN PROC PIVOTAL DATA: Q3 2021 POTENTIAL APPROVAL: 2022 INNOVATIVE EARLIER STAGE CANDIDATES AND ADVANCED ADC

Exhibit 99.1 TARGET A BETTER NOW Nasdaq: IMGN J.P. Morgan Healthcare Conference January 11-14, 2021 Exhibit 99.1 2 This presentation includes forward-looking statements regarding ImmunoGen’s expectations related to the design and potential success of ImmunoGen’s mirvetuximab soravtansine and IMGN632 clinical studies and regulatory pathways, including the timing of initiating and receiving data fro

- FORM S-8

As filed with the Securities and Exchange Commission on December 21, 2020 Registration No.

The following table sets forth the estimated costs and expenses, other than sales commissions to the Agent, payable by the registrant in connection with the sale of the securities being registered:

Exhibit 99.1 The registrant is filing this Exhibit 99.1 for the purpose of incorporating the information set forth herein by reference into the registration statement on Form S-3 (File No. 333-251502) that was filed by the registrant with the Securities and Exchange Commission on December 18, 2020 and became effective upon filing. The following table sets forth the estimated costs and expenses, ot

Open Market Sale AgreementSM, dated December 18, 2020, by and between the Registrant and Jeffries LLC

EX-10.1 3 tm2038486d4ex10-1.htm EXHIBIT 10.1 Exhibit 10.1 OPEN MARKET SALE AGREEMENTSM December 18, 2020 JEFFERIES LLC 520 Madison Avenue New York, New York 10022 Ladies and Gentlemen: ImmunoGen, Inc., a Massachusetts corporation (the “Company”), proposes, subject to the terms and conditions stated herein, to issue and sell from time to time through Jefferies LLC, as sales agent and/or principal (

Form of Senior Indenture.

Exhibit 4.7 IMMUNOGEN, INC. Issuer AND [ ] Trustee INDENTURE Dated as of [ ] Senior Debt Securities CROSS-REFERENCE TABLE (1) Section of Trust Indenture Act Section of of 1939, as Amended Indenture 310(a). 7.09 310(b). 7.08 7.10 310(c). Inapplicable 311(a). 7.13(a) 311(b). 7.13(b) 311(c). Inapplicable 312(a) 5.02(a) 312(b). 5.02(b) 312(c). 5.02(c) 313(a). 5.04(a) 313(b). 5.04(a) 313(c). 5.04(a) 5.

Entry into a Material Definitive Agreement, Termination of a Material Definitive Agreement, Financial Statements and Exhibits - FORM 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 18, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fi

Form of Subordinated Indenture.

Exhibit 4.8 IMMUNOGEN, INC. Issuer AND [ ] Trustee INDENTURE Dated as of [ ] Subordinated Debt Securities CROSS-REFERENCE TABLE (1) Section of Trust Indenture Act Section of of 1939, as Amended Indenture 310(a). 7.09 310(b). 7.08 7.10 310(c). Inapplicable 311(a). 7.13(a) 311(b). 7.13(b) 311(c). Inapplicable 312(a) 5.02(a) 312(b). 5.02(b) 312(c). 5.02(c) 313(a). 5.04(a) 313(b). 5.04(a) 313(c). 5.04

Financial Statements and Exhibits, Other Events - FORM 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 18, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fi

RISK FACTORS

Exhibit 99.1 Unless the context otherwise requires in this Exhibit 99.1, “ImmunoGen,” “the Company,” “we,” “us,” “our” and similar names refer to ImmunoGen, Inc. and our subsidiaries. Our trademarks include, without limitation, our name and corporate logo. Other service marks, trademarks and trade names contained in this Exhibit 99.1 are the property of their respective owners. RISK FACTORS INVEST

CALCULATION OF REGISTRATION FEE

TABLE OF CONTENTS Filed Pursuant to Rule 424(b)(5) Registration No. 333-251502 CALCULATION OF REGISTRATION FEE Title of Securities to be Registered Proposed Maximum Aggregate Offering Price Amount of Registration Fee Common Stock, $.01 par value $ 150,000,000 $ 16,365(1) (1) Calculated in accordance with Rule 457(o) under the Securities Act of 1933, as amended. This “Calculation of Registration Fe

- S-3ASR

TABLE OF CONTENTS As filed with the Securities and Exchange Commission on December 18, 2020 Registration No.

Other Events - 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 10, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fi

CONFIDENTIAL 2 FORWARD LOOKING STATEMENTS This presentation includes forward-looking statements based on management's current expectations. These statements include, but are not limited to, ImmunoGen’s expectations related to: the occurrence, timing,

Exhibit 99.2 CONFIDENTIAL 1 IMGN632 Investor Call December 7, 2020 Exhibit 99.2 CONFIDENTIAL 2 FORWARD LOOKING STATEMENTS This presentation includes forward-looking statements based on management's current expectations. These statements include, but are not limited to, ImmunoGen’s expectations related to: the occurrence, timing, and outcome of potential pre-clinical, clinical, and regulatory event

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events - 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): December 5, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

ImmunoGen Presents Updated Findings from Phase 1/2 Study of IMGN632 in Blastic Plasmacytoid Dendritic Cell Neoplasm at ASH Annual Meeting

EX-99.1 2 imgn-20201205xex99d1.htm EX-99.1 Exhibit 99.1 ImmunoGen Presents Updated Findings from Phase 1/2 Study of IMGN632 in Blastic Plasmacytoid Dendritic Cell Neoplasm at ASH Annual Meeting Updated Data Demonstrating Favorable Safety Profile and Encouraging Monotherapy Activity in BPDCN Presented During Oral Session Preclinical Combination Data in Relapsed/Refractory AML Support Further Evalua

- 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): November 6, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

Quarterly Report - 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2020 OR ☐ 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 0-17999 I

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ImmunoGen Reports Recent Progress and Third Quarter 2020 Financial Results Partnership with Huadong Medicine Accelerates Development and Commercialization of Mirvetuximab Soravtansine in Greater China Encouraging Anti-Tumor Activity and Tolerability Data from FORWARD II Triplet Cohort Evaluating Mirvetuximab in Combination with Carboplatin and Avastin® in Platinum-Sensitive Ovarian Ca

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers - 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): October 22, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

Regulation FD Disclosure, Entry into a Material Definitive Agreement, Financial Statements and Exhibits - 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): October 19, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission Fil

ImmunoGen and Huadong Medicine Announce Strategic Collaboration to Develop and Commercialize Mirvetuximab Soravtansine in Greater China

Exhibit 99.1 ImmunoGen and Huadong Medicine Announce Strategic Collaboration to Develop and Commercialize Mirvetuximab Soravtansine in Greater China Partnership Accelerates Development Path for Mirvetuximab in Greater China and Expands Huadong Medicine’s Oncology Portfolio with Innovative ADC Combines ImmunoGen’s Lead Clinical Program with Huadong’s Regional Oncology Expertise ImmunoGen to Receive

ImmunoGen Raises $54.8 Million in Gross Proceeds Through its At-the-Market Facility

Exhibit 99.1 ImmunoGen Raises $54.8 Million in Gross Proceeds Through its At-the-Market Facility Waltham, MA – October 12, 2020 – ImmunoGen, Inc. (Nasdaq: IMGN), a leader in the expanding field of antibody-drug conjugates (ADCs) for the treatment of cancer, today announced that it has raised gross proceeds of approximately $54.8 million through its At-the-Market (“ATM") facility pursuant to its Op

Financial Statements and Exhibits, Other Events - 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): October 9, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File

The following table sets forth the estimated costs and expenses, other than sales commissions to the Agent, payable by the registrant in connection with the sale of the securities being registered:

Exhibit 99.1 The registrant is filing this Exhibit 99.1 for the purpose of incorporating the information set forth herein by reference into the registration statement on Form S-3 (File No. 333-223507) that was filed by the registrant with the Securities and Exchange Commission on March 7, 2018 and became effective upon filing. The following table sets forth the estimated costs and expenses, other

Open Market Sale AgreementSM, dated September 25, 2020, by and between ImmunoGen, Inc. and Jefferies LLC

Exhibit 10.1 OPEN MARKET SALE AGREEMENTSM September 25, 2020 JEFFERIES LLC 520 Madison Avenue New York, New York 10022 Ladies and Gentlemen: ImmunoGen, Inc., a Massachusetts corporation (the “Company”), proposes, subject to the terms and conditions stated herein, to issue and sell from time to time through Jefferies LLC, as sales agent and/or principal (the “Agent”), shares of the Company’s common

CALCULATION OF REGISTRATION FEE

TABLE OF CONTENTS Filed Pursuant to Rule 424(b)(5) Registration No. 333-223507 CALCULATION OF REGISTRATION FEE Title of Securities to be Registered Proposed Maximum Aggregate Offering Price Amount of Registration Fee Common Stock, $.01 par value $ 100,000,000 $ 2,363(1)(2) (1) Calculated in accordance with Rule 457(o) under the Securities Act of 1933, as amended. This “Calculation of Registration

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): September 25, 2020 ImmunoGen, Inc

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): September 25, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission F

Form of Performance-Based Stock Option Agreement (February 2020) under the Inducement Equity Incentive Plan

Exhibit 10-2 IMMUNOGEN, INC. PERFORMANCE-BASED NON-QUALIFIED STOCK OPTION TERMS AND CONDITIONS The following supplements the Grant Detail (the “Grant Detail”) to which these Performance-Based Non-Qualified Stock Option Terms and Conditions apply, and together with the Grant Detail, constitutes the “Option Agreement” referenced in the Grant Detail. This Option Agreement is entered into and made eff

Change in Control Severance Agreement dated as of July 20, 2020 between the Registrant and Susan Altschuller, Ph.D.

Exhibit 10-4 CHANGE IN CONTROL SEVERANCE AGREEMENT This Agreement is entered into as of the 20th day of July, 2020 (the “Effective Date”) by and between ImmunoGen, Inc.

Articles of Amendment (incorporated herein by reference to Exhibit 3.1(c) of the Company’s quarterly report on Form 10-Q for the quarter ended June 30, 2020, filed with the Commission on August 5, 2020 (Commission File No. 000-17999)).

Exhibit 3.1(c) D PC Qrbe

Quarterly Report - 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2020 OR ☐ 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 0-17999 Immuno

Employment Offer Letter dated June 30, 2020 between the Registrant and Susan Altschuller

Exhibit 10.3 June 29, 2020 Susan Altschuller 45 Tennyson St Somerville, MA 02145 Dear Susan: I am delighted to offer you the full-time position of Senior Vice President and Chief Financial Officer at ImmunoGen, Inc. (“ImmunoGen” or the “Company”). This offer is contingent upon approval of the Board of Director’s Compensation Committee (“Compensation Committee”). The Compensation Committee will for

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): July 31, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File N

SELECTED FINANCIAL INFORMATION

Exhibit 99.1 ImmunoGen Reports Recent Progress and Second Quarter 2020 Financial Results Encouraging Data from FORWARD II Study of Mirvetuximab in Combination with Avastin® in Recurrent Ovarian Cancer, Regardless of Platinum Status, Presented at ASCO Preclinical Data on Next Generation Anti-FRα ADC, IMGN151, Demonstrating Enhanced Anti-Tumor Activity, Presented at AACR Positive Opinion on Orphan D

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers - 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): July 20, 2020 ImmunoGen, Inc. (Exact name of registrant as specified in its charter) Massachusetts 0-17999 04-2726691 (State or other jurisdiction of incorporation) (Commission File N