SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

MPM BioVentures 2014, L.P.

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 1,725,184.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 1,725,184.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

1,725,184.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

3.6 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

MPM BioVentures 2014 (B), L.P.

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 115,066.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 115,066.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

115,066.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

0.2 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

MPM Asset Management Investors BV2014 LLC

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 59,379.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 59,379.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

59,379.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

0.1 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

UBS Oncology Impact Fund L.P.

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 1,426,938.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 1,426,938.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

1,426,938.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

2.9 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

MPM BioVentures 2014 GP LLC

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,840,250.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,840,250.00

Aggregate amount beneficially owned by each reporting person

1,840,250.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

3.8 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

MPM BioVentures 2014 LLC

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,899,629.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,899,629.00

Aggregate amount beneficially owned by each reporting person

1,899,629.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

3.9 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

Oncology Impact Fund (Cayman) Management L.P.

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,426,938.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,426,938.00

Aggregate amount beneficially owned by each reporting person

1,426,938.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

2.9 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

MPM BioImpact LLC

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,426,938.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,426,938.00

Aggregate amount beneficially owned by each reporting person

1,426,938.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

2.9 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

ANSBERT GADICKE

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 3,977,612.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 3,977,612.00

Aggregate amount beneficially owned by each reporting person

3,977,612.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

8.2 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

LUKE EVNIN

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 2,550,674.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 2,550,674.00

Aggregate amount beneficially owned by each reporting person

2,550,674.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

5.3 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

Todd Foley

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,899,629.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,899,629.00

Aggregate amount beneficially owned by each reporting person

1,899,629.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

3.9 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

MPM ASSET MANAGEMENT LLC

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 273,218.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 273,218.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

273,218.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

0.6 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

MPM ONCOLOGY INNOVATIONS FUND LP

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 377,827.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 377,827.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

377,827.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

0.8 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP No.

95075A107

Name of reporting person

MPM Oncology Innovations Fund GP LLC

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 377,827.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 377,827.00

Aggregate amount beneficially owned by each reporting person

377,827.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

0.8 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

Item 1.

Security and Issuer

(a)

Title of Class of Securities:

Common Stock

(b)

Name of Issuer:

WEREWOLF THERAPEUTICS, INC.

(c)

Address of Issuer's Principal Executive Offices:

200 TALCOTT AVENUE, 2ND FLOOR, WATERTOWN, MASSACHUSETTS , 02472.

Item 1 Comment:

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.

Item 5.

Interest in Securities of the Issuer

(a)

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.

(b)

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.

(c)

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

(d)

Inapplicable.

(e)

Inapplicable.

Item 7.

Material to be Filed as Exhibits.

Joint Filing Statement

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

MPM BioVentures 2014, L.P.

Signature:	/s/ Ansbert Gadicke
Name/Title:	Managing Director of MPM BioVentures 2014 LLC, the Managing Member of MPM BioVentures 2014 GP LLC, the General Partner of MPM BioVentures 2014, L.P.
Date:	12/29/2025

MPM BioVentures 2014 (B), L.P.

Signature:	/s/ Ansbert Gadicke
Name/Title:	Managing Director of MPM BioVentures 2014 LLC, Managing Member of MPM BioVentures 2014 GP LLC, the General Partner of MPM BioVentures 2014 (B), L.P.
Date:	12/29/2025

MPM Asset Management Investors BV2014 LLC

Signature:	/s/ Ansbert Gadicke
Name/Title:	Managing Director of MPM BioVentures 2014 LLC, the manager of MPM Asset Management Investors BV2014 LLC
Date:	12/29/2025

UBS Oncology Impact Fund L.P.

Signature:	/s/ Ansbert Gadicke
Name/Title:	Managing Partner of MPM BioImpact LLC, the GP of Oncology Impact Fund (Cayman) Management L.P., the GP of UBS Oncology Impact Fund L.P.
Date:	12/29/2025

MPM BioVentures 2014 GP LLC

Signature:	/s/ Ansbert Gadicke
Name/Title:	Managing Director of MPM BioVentures 2014 LLC, the Managing Member of MPM BioVentures 2014 GP LLC
Date:	12/29/2025

MPM BioVentures 2014 LLC

Signature:	/s/ Ansbert Gadicke
Name/Title:	Managing Director
Date:	12/29/2025

Oncology Impact Fund (Cayman) Management L.P.

Signature:	/s/ Ansbert Gadicke
Name/Title:	Managing Partner of MPM BioImpact LLC, the General Partner of Oncology Impact Fund (Cayman) Management L.P.
Date:	12/29/2025

MPM BioImpact LLC

Signature:	/s/ Ansbert Gadicke
Name/Title:	Managing Partner
Date:	12/29/2025

ANSBERT GADICKE

Signature:	/s/ Ansbert Gadicke
Name/Title:	Ansbert Gadicke
Date:	12/29/2025

LUKE EVNIN

Signature:	/s/ Luke Evnin
Name/Title:	Luke Evnin
Date:	12/29/2025

Todd Foley

Signature:	/s/ Todd Foley
Name/Title:	Todd Foley
Date:	12/29/2025

MPM ASSET MANAGEMENT LLC

Signature:	/s/ Ansbert Gadicke
Name/Title:	Member
Date:	12/29/2025

MPM ONCOLOGY INNOVATIONS FUND LP

Signature:	/s/ Ansbert Gadicke
Name/Title:	Manager of MPM Oncology Innovations Fund GP LLC, the General Partner of MPM Oncology Innovations Fund, L.P.
Date:	12/29/2025

MPM Oncology Innovations Fund GP LLC

Signature:	/s/ Ansbert Gadicke
Name/Title:	Manager
Date:	12/29/2025