X0202 SCHEDULE 13D/A 0001609492-26-000002 0001609492 XXXXXXXX LIVE 6 Common Stock 05/01/2026 false 0001785530 95075A107 WEREWOLF THERAPEUTICS, INC.

200 TALCOTT AVENUE 2ND FLOOR WATERTOWN MA 02472

Ansbert Gadicke 617-425-9200 c/o MPM BioImpact LLC 339 Boylston Street, Suite 1100 Boston MA 02116 0001609492 N MPM BioVentures 2014, L.P. b WC N DE 1131359.00 0.00 1131359.00 0.00 1131359.00 N 2.3 PN 0001609493 N MPM BioVentures 2014 (B), L.P. b WC N DE 75458.00 0.00 75458.00 0.00 75458.00 N 0.2 PN 0001609495 N MPM Asset Management Investors BV2014 LLC b WC N DE 38939.00 0.00 38939.00 0.00 38939.00 N 0.1 OO 0001691428 N UBS Oncology Impact Fund L.P. b WC N E9 936031.00 0.00 936031.00 0.00 936031.00 N 1.9 PN 0001765091 N MPM BioVentures 2014 GP LLC b WC N DE 0.00 1206817.00 0.00 1206817.00 1206817.00 N 2.5 OO 0001765021 N MPM BioVentures 2014 LLC b WC N DE 0.00 1245756.00 0.00 1245756.00 1245756.00 N 2.6 OO 0001721036 N Oncology Impact Fund (Cayman) Management L.P. b WC N E9 0.00 936031.00 0.00 936031.00 936031.00 N 1.9 PN 0001687078 N MPM BioImpact LLC b WC N DE 0.00 936031.00 0.00 936031.00 936031.00 N 1.9 OO 0001134655 N ANSBERT GADICKE b WC N X1 0.00 2608501.00 0.00 2608501.00 2608501.00 N 5.4 IN 0001134657 N LUKE EVNIN b WC N X1 0.00 1672470.00 0.00 1672470.00 1672470.00 N 3.4 IN 0001473930 N Todd Foley b WC N X1 0.00 1245756.00 0.00 1245756.00 1245756.00 N 2.6 IN 0001263048 N MPM ASSET MANAGEMENT LLC b WC N DE 179188.00 0.00 179188.00 0.00 179188.00 N 0.4 OO 0001719960 N MPM ONCOLOGY INNOVATIONS FUND LP b WC N DE 247526.00 0.00 247526.00 0.00 247526.00 N 0.5 PN 0001857903 N MPM Oncology Innovations Fund GP LLC b WC N DE 0.00 247526.00 0.00 247526.00 247526.00 Y 0.5 OO Common Stock WEREWOLF THERAPEUTICS, INC. 200 TALCOTT AVENUE 2ND FLOOR WATERTOWN MA 02472 Explanatory Note: This Amendment No. 6 to Schedule 13D ("Amendment No. 6") is being filed as an amendment to the initial statement on Schedule 13D relating to the common stock (the "Common Stock"), of Werewolf Therapeutics Inc. (the 'Issuer'), as filed with the Securities and Exchange Commission (the "SEC") on May 14, 2021 and as amended by Amendment No. 1 filed November 4, 2025, Amendment No. 2 filed November 17, 2025, Amendment No. 3 filed December 3, 2025, Amendment No. 4 filed December 29, 2025 and Amendment No. 5 filed January 16, 2026 (as amended, the "Original Schedule 13D"). This Schedule 13D/A is being filed by the Filing Persons to report the open market sales of the Issuer's Common Stock by certain Filing Persons. Items 5 and 7 of the Original Schedule 13D are hereby amended and supplemented to the extent hereinafter expressly set forth and, except as amended and supplemented hereby, the Original Schedule 13D remains in full force and effect. All capitalized terms used in this Amendment No. 6 but not defined herein shall have the meanings ascribed thereto in the Original Schedule 13D. See rows (11) and (13) of the Filing Persons Owner Profile of this Amendment No. 6 for the aggregate number of Common Stock and percentages of the shares of Common Stock beneficially owned by the Filing Person. The Common Stock is held as follows: * 1,131,359 shares are held directly by BV 2014; * 75,458 shares are held directly by BV 2014(B); * 38,939 shares are held directly by AM BV2014 LLC; * 247,526 shares are held directly by MPM OIF; * 179,188 shares by AM LLC; and * 936,031 shares are held directly by UBS Oncology. BV 2014 GP and BV 2014 LLC are the direct and indirect general partners of BV 2014 and BV 2014(B) and, accordingly, may be deemed to beneficially own the shares held by BV 2014 and BV 2014(B). BV 2014 LLC is the managing member of AM BV2014 LLC and, accordingly, may be deemed to beneficially own the shares held by AM BV2014 LLC. MPM OIF GP is the general Partner of MPM OIF and, accordingly, may be deemed to beneficially own the shares held by MPM OIF. BioImpact and Oncology Cayman are the direct and indirect general partners of UBS Oncology and, accordingly, may be deemed to beneficially own the shares held by UBS Oncology. Drs. Gadicke and Evnin and Mr. Foley are the managing directors of BV 2014 LLC and, accordingly, may be deemed to beneficially own the shares held by BV 2014, BV 2014(B) and AM BV2014 LLC. Drs. Gadicke and Evnin are the members of AM LLC and managers of MPM OIF GP and, accordingly, may be deemed to beneficially own the shares held by AM LLC and MPM OIF. Dr. Gadicke is the managing partner of BioImpact and, accordingly may be deemed to beneficially own the shares held by UBS Oncology. Calculation of the percentage of the shares of Common Stock beneficially owned is based upon 48,596,817 shares of Common Stock outstanding as of March 20, 2026, as reported in the Issuer's Form 10-K filed with the SEC on March 27, 2026. See rows (7) through (10) of the Filing Persons Owner Profile of this Amendment No. 6 for the number of shares as to which there is sole power to vote or to direct the vote, sole power to dispose or to direct the disposition, or shared power to dispose or to direct the disposition. The Reporting Persons sold the following Common Stock in the open market in the last 60 days: Date of Price Range Ave. Price Sold by Sold by Sold By Sold by Sold by Sold by Sale BV 2014 BV AM BV2014 MPM OIF AM LLC UBS 2014(B) LLC Oncology 04/27/26 $0.818-$0.8788 $0.85 36,488 2,434 1,256 7,983 5,779 30,188 04/28/26 $0.673-$0.82 $0.73 64,541 4,305 2,222 14,121 10,223 53,400 04/29/26 $0.68-$0.75 $0.69 38,259 2,552 1,317 8,371 6,060 31,654 04/30/26 $0.688-$0.7458 $0.72 113,821 7,592 3,918 24,903 18,028 94,172 05/01/26 $0.7011-$0.74 $0.73 39,501 2,635 1,360 8,642 6,256 32,682 05/04/26 $0.69-$0.7497 $0.72 32,455 2,164 1,117 7,098 5,139 26,843 05/05/26 $0.6616-$0.7253 $0.69 4,640 310 160 1,015 735 3,840 Inapplicable. Inapplicable. Exhibit 99.C - Joint Filing Statement MPM BioVentures 2014, L.P. /s/ Ansbert Gadicke 05/05/2026 MPM BioVentures 2014 (B), L.P. /s/ Ansbert Gadicke 05/05/2026 MPM Asset Management Investors BV2014 LLC /s/ Ansbert Gadicke 05/05/2026 UBS Oncology Impact Fund L.P. /s/ Ansbert Gadicke 05/05/2026 MPM BioVentures 2014 GP LLC /s/ Ansbert Gadicke 05/05/2026 MPM BioVentures 2014 LLC /s/ Ansbert Gadicke 05/05/2026 Oncology Impact Fund (Cayman) Management L.P. /s/ Ansbert Gadicke 05/05/2026 MPM BioImpact LLC /s/ Ansbert Gadicke 05/05/2026 ANSBERT GADICKE /s/ Ansbert Gadicke 05/05/2026 LUKE EVNIN /s/ Luke Evnin 05/05/2026 Todd Foley /s/ Todd Foley 05/05/2026 MPM ASSET MANAGEMENT LLC /s/ Ansbert Gadicke 05/05/2026 MPM ONCOLOGY INNOVATIONS FUND LP /s/ Ansbert Gadicke 05/05/2026 MPM Oncology Innovations Fund GP LLC /s/ Ansbert Gadicke 05/05/2026