SCHEDULE 13D/A 0001231919-25-000570 0001609492 XXXXXXXX LIVE 4 Common Stock 12/22/2025 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 1725184.00 0.00 1725184.00 0.00 1725184.00 N 3.6 PN 0001609493 N MPM BioVentures 2014 (B), L.P. b WC N DE 115066.00 0.00 115066.00 0.00 115066.00 N 0.2 PN 0001609495 N MPM Asset Management Investors BV2014 LLC b WC N DE 59379.00 0.00 59379.00 0.00 59379.00 N 0.1 OO 0001691428 N UBS Oncology Impact Fund L.P. b WC N E9 1426938.00 0.00 1426938.00 0.00 1426938.00 N 2.9 PN 0001765091 N MPM BioVentures 2014 GP LLC b WC N DE 0.00 1840250.00 0.00 1840250.00 1840250.00 N 3.8 OO 0001765021 N MPM BioVentures 2014 LLC b WC N DE 0.00 1899629.00 0.00 1899629.00 1899629.00 N 3.9 OO 0001721036 N Oncology Impact Fund (Cayman) Management L.P. b WC N E9 0.00 1426938.00 0.00 1426938.00 1426938.00 N 2.9 PN 0001687078 N MPM BioImpact LLC b WC N DE 0.00 1426938.00 0.00 1426938.00 1426938.00 N 2.9 OO 0001134655 N ANSBERT GADICKE b WC N X1 0.00 3977612.00 0.00 3977612.00 3977612.00 N 8.2 IN 0001134657 N LUKE EVNIN b WC N X1 0.00 2550674.00 0.00 2550674.00 2550674.00 N 5.3 IN 0001473930 N Todd Foley b WC N X1 0.00 1899629.00 0.00 1899629.00 1899629.00 N 3.9 IN 0001263048 N MPM ASSET MANAGEMENT LLC b WC N DE 273218.00 0.00 273218.00 0.00 273218.00 N 0.6 OO 0001719960 N MPM ONCOLOGY INNOVATIONS FUND LP b WC N DE 377827.00 0.00 377827.00 0.00 377827.00 N 0.8 PN 0001857903 N MPM Oncology Innovations Fund GP LLC b WC N DE 0.00 377827.00 0.00 377827.00 377827.00 N 0.8 OO Common Stock WEREWOLF THERAPEUTICS, INC. 200 TALCOTT AVENUE 2ND FLOOR WATERTOWN MA 02472 Explanatory Note: This Amendment No. 4 to Schedule 13D ("Amendment No. 3") 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 and Amendment No. 3 filed December 3, 2025 (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. 4 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. 3 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: * 1,725,184 shares are held directly by BV 2014; * 115,066 shares are held directly by BV 2014(B); * 59,379 shares are held directly by AM BV2014 LLC; * 377,827 shares are held directly by MPM OIF; * 273,218 shares by AM LLC; and * 1,426,938 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 48,540,200 Common Stock outstanding as of October 29, 2025, as reported in the Issuer's Form 10-Q filed with the SEC on November 4, 2025. See rows (7) through (10) of the Filing Persons Owner Profile of this Amendment No. 4 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 since the date of filing Amendment No. 3: Date of Price Range Ave. Price Sold by Sold by Sold By Sold by Sold by Sold by Sale BV 2014 BV 2014(B) AM BV2014 MPM OIF AM LLC UBS Oncology LLC 12/04/25 $0.92-$1.0208 $0.97 36,101 2,408 1,243 7,950 5,714 29,814 12/05/25 $0.9434-$0.9863 $0.97 11,197 747 386 2,466 1,772 9,247 12/08/25 $0.9582-$1.01 $0.99 23,006 1,534 792 5,067 3,642 18,999 12/09/25 $0.99-$1.025 $1.01 30,123 2,009 1,036 6,634 4,768 24,877 12/10/25 $0.9472-$1.11 $1.06 25,077 1,673 863 5,522 3,969 20,709 12/11/25 $1.045-$1.10 $1.07 18,930 1,263 651 4,169 2,996 15,633 12/12/25 $1.06-$1.10 $1.08 12,069 805 416 2,658 1,910 9,967 12/15/25 $1.02-$1.10 $1.07 15,977 1,066 550 3,518 2,529 13,194 12/16/25 $1.02-$1.10 $1.05 9,832 656 339 2,165 1,556 8,120 12/17/25 $1.095-$1.18 $1.14 6,747 450 232 1,486 1,068 5,572 12/22/25 $0.6596-$0.7341 $0.69 40,082 2,673 1,381 8,827 6,344 33,101 12/23/25 $0.61-$0.6728 $0.63 48,274 3,220 1,662 10,631 7,641 39,867 12/24/25 $0.6337-$0.66 $0.65 11,023 735 379 2,428 1,745 9,103 12/26/25 $0.6165-$0.66 $0.63 24,082 1,606 829 5,303 3,812 19,888 12/29/25 $0.58955-$0.65 $0.61 73,401 4,896 2,256 16,165 11,618 60,618 Inapplicable. Inapplicable. Joint Filing Statement MPM BioVentures 2014, L.P. /s/ Ansbert Gadicke 12/29/2025 MPM BioVentures 2014 (B), L.P. /s/ Ansbert Gadicke 12/29/2025 MPM Asset Management Investors BV2014 LLC /s/ Ansbert Gadicke 12/29/2025 UBS Oncology Impact Fund L.P. /s/ Ansbert Gadicke 12/29/2025 MPM BioVentures 2014 GP LLC /s/ Ansbert Gadicke 12/29/2025 MPM BioVentures 2014 LLC /s/ Ansbert Gadicke 12/29/2025 Oncology Impact Fund (Cayman) Management L.P. /s/ Ansbert Gadicke 12/29/2025 MPM BioImpact LLC /s/ Ansbert Gadicke 12/29/2025 ANSBERT GADICKE /s/ Ansbert Gadicke 12/29/2025 LUKE EVNIN /s/ Luke Evnin 12/29/2025 Todd Foley /s/ Todd Foley 12/29/2025 MPM ASSET MANAGEMENT LLC /s/ Ansbert Gadicke 12/29/2025 MPM ONCOLOGY INNOVATIONS FUND LP /s/ Ansbert Gadicke 12/29/2025 MPM Oncology Innovations Fund GP LLC /s/ Ansbert Gadicke 12/29/2025