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SCHEDULE 13D/A 0001788357 XXXXXXXX LIVE 3 Common Stock, par value $0.01 per share 08/14/2025 false 0001496323 449585108 IGM Biosciences, Inc. 325 E MIDDLEFIELD ROAD MOUNTAIN VIEW CA 94043 Topsoe Holding A/S 45 4527 2000 Haldor Topsoes Alle 1 DK Kgs. Lyngby G7 2800 0001788357 N Topsoe Holding A/S WC N G7 0 0 0 0 0 N 0 OO Y Jakob Haldor Topsoe PF N G7 0 0 0 0 0 N 0 IN Y Christina Teng Topsoe PF N G7 0 0 0 0 0 N 0 IN Y Anne Haugwitz-Hardenberg-Reventlow PF N G7 0 0 0 0 0 N 0 IN Y Emil Oigaard PF N G7 0 0 0 0 0 N 0 IN Y Thomas Schleicher PF N G7 0 0 0 0 0 N 0 IN Y Birgitte Nielsen PF N G7 0 0 0 0 0 N 0 IN Common Stock, par value $0.01 per share IGM Biosciences, Inc. 325 E MIDDLEFIELD ROAD MOUNTAIN VIEW CA 94043 AMENDMENT NO. 3 TO SCHEDULE 13D This Amendment No. 3 to Schedule 13D amends and supplements the information provided in the previously filed Statement on Schedule 13D filed with the Securities and Exchange Commission on July 19, 2023, as amended to date (the "Schedule 13D"), jointly on behalf of Topsoe Holding A/S (formerly Haldor Topsoe Holding A/S) ("Topsoe Holding"), Jakob Haldor Topsoe, Christina Teng Topsoe, Anne Haugwitz-Hardenberg-Reventlow, Emil Oigaard, Thomas Schleicher and Birgitte Nielsen (each a "Reporting Person" and collectively, the "Reporting Persons"). Except as supplemented herein, such statements, as heretofore amended and supplemented, remain unchanged in all material respects and in full force and effect. Capitalized terms used but not defined herein have the meaning ascribed to such term in the Schedule 13D, as amended. Responses to each item of this Amendment No. 3 to Schedule 13D are incorporated by reference into the response to each other item, as applicable. Item 2 of Schedule 13D is hereby amended and supplemented as follows: (a), (b), (c) and (f) This Statement is being filed jointly on behalf of Topsoe Holding, a Danish stock-based corporation whose principal business, through its subsidiary operating companies, is catalysis and chemical processing, Jakob Haldor Topsoe, Christina Teng Topsoe, Anne Haugwitz-Hardenberg-Reventlow, Emil Oigaard, Thomas Schleicher and Birgitte Nielsen. The business address and principal office of each Reporting Person is Haldor Topsoes Alle, 1 DK-2800, Kgs. Lyngby, Denmark. Attached as Annex 1 is a chart setting forth, with respect to each executive officer and director of the Topsoe Holding, his or her name, residence or business address, present principal occupation or employment (along with the name, principal business and address of any corporation or other organization in which such employment is conducted) and citizenship, in each case as of the date hereof. Not applicable. Item 4 of Schedule 13D is hereby amended and supplemented as follows: On July 1, 2025, the Issuer entered into an Agreement and Plan of Merger (the "Merger Agreement") with Concentra Biosciences, LLC, a Delaware limited liability company ("Concentra"), and Concentra Merger Sub V, Inc., a Delaware corporation and a wholly owned subsidiary of Concentra ("Merger Sub"). The Merger Agreement provides for, among other things: (i) the acquisition of all of the Issuer's outstanding shares of common stock, par value $0.01 per share (the "Common Stock"), by Concentra through a cash tender offer (the "Offer"), for a price per share of the Common Stock of (A) $1.247 in cash (the "Cash Amount"), subject to applicable tax withholding and without interest; plus (B) one contingent value right (a "CVR") (such amount being the "CVR Amount" and the Cash Amount plus the CVR Amount, collectively being the "Offer Price") and (ii) the merger of Merger Sub with and into the Issuer (the "Merger") with the Issuer surviving the Merger. The foregoing description of the Merger Agreement and the transactions contemplated thereby is qualified in its entirety by reference to the full text of the Merger Agreement, a copy of which is attached as Exhibit 2.1 to the Issuer's Current Report on Form 8-K filed with the U.S. Securities and Exchange Commission (the "SEC") on July 1, 2025. The information contained in rows 7, 8, 9, 10, 11 and 13 on each of the cover pages of this Schedule 13D and the information set forth or incorporated in Items 2, 3, 4 and 6 is incorporated by reference in its entirety into this Item 5. Item 5 of Schedule 13D is hereby amended and supplemented as follows: The Reporting Persons do not beneficially own any shares of common stock. Regarding the number of shares as to which such person has: (i) sole power to vote or to direct the vote: See line 7 of cover sheets (ii) shared power to vote or to direct the vote: See line 8 of cover sheets (iii) sole power to dispose or to direct the disposition: See line 9 of cover sheets (iv) shared power to dispose or to direct the disposition: See line 10 of cover sheets. Except as set forth in Item 4 above, none of the Reporting Persons has effected any transactions in the Common Stock during the last 60 days. No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, Common Stock beneficially owned by any of the Reporting Persons. Each of the Reporting Persons has ceased to beneficially own five percent (5%) or more of the Issuer's common stock as of August 14, 2025. The information set forth in Items 3, 4 and 5 of this Statement is incorporated by reference into this Item 6. Exhibit Number Description Exhibit 99.1 Joint Filing Agreement, dated as of August 18, 2025, between Topsoe Holding A/S, Jakob Haldor Topsoe, Christina Teng Topsoe, Anne Haugwitz-Hardenberg-Reventlow Emil Oigaard. Topsoe Holding A/S By: /s/ Henrik Gaarn Bak Henrik Gaarn Bak, Managing Director 08/18/2025 Jakob Haldor Topsoe /s/ Jakob Haldor Topsoe Jakob Haldor Topsoe 08/18/2025 Christina Teng Topsoe /s/ Christina Teng Topsoe Christina Teng Topsoe 08/18/2025 Anne Haugwitz-Hardenberg-Reventlow /s/ Anne Haugwitz-Hardenberg-Reventlow Anne Haugwitz-Hardenberg-Reventlow 08/18/2025 Emil Oigaard /s/ Emil Oigaard Emil Oigaard 08/18/2025 Thomas Schleicher /s/ Thomas Schleicher Thomas Schleicher 08/18/2025 Birgitte Nielsen /s/ Birgitte Nielsen Birgitte Nielsen 08/18/2025