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HOWL insider MPM-affiliated director reports November stock sales

Filing Impact
(Moderate)
Filing Sentiment
(Negative)
Form Type
4

Rhea-AI Filing Summary

Werewolf Therapeutics, Inc. (HOWL) reported insider stock sales by an affiliated director and 10% owner. Investment entities associated with MPM BioImpact LLC filed a Form 4 showing automatic sales of common stock under a Rule 10b5-1 trading plan dated September 24, 2025. On November 13, 2025, they sold 90,951 shares at a weighted average price of $0.98 per share, followed by 61,640 shares at $0.93 on November 14 and 57,061 shares at $0.95 on November 17. After these transactions, the group reported indirect beneficial ownership of 5,481,539 shares held across several MPM-managed funds, while disclaiming beneficial ownership beyond their economic interest. This filing is one of two identical submissions due to limits on the number of reporting persons.

Positive

  • None.

Negative

  • None.
Insider MPM BioVentures 2014, L.P., MPM BioVentures 2014 (B), L.P., MPM BioVentures 2014 LLC, MPM BioVentures 2014 GP LLC, MPM Asset Management Investors BV2014 LLC
Role 10% Owner | 10% Owner | 10% Owner | 10% Owner | 10% Owner
Sold 209,652 shs ($201K)
Type Security Shares Price Value
Sale Common Stock 57,061 $0.95 $54K
Sale Common Stock 61,640 $0.93 $57K
Sale Common Stock 90,951 $0.98 $89K
Holdings After Transaction: Common Stock — 5,481,539 shares (Indirect, See Footnotes)
Footnotes (1)
  1. Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 dated September 24, 2025. The shares were sold as follows: 6,244 by MPM Asset Management LLC ("AM LLC"), 39,450 by MPM BioVentures 2014, L.P. ("BV 2014"), 2,631 by MPM BioVentures 2014(B), L.P. ("BV 2014(B)"), 1,359 by MPM Asset Management Investors BV2014 LLC ("AM BV2014"), 8,688 by MPM Oncology Innovations Fund, L.P. ("MPM OIF") and 32,579 by UBS Oncology Impact Fund L.P. ("UBS Oncology"). The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.918 to $1.07 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. MPM BioVentures 2014 GP LLC and MPM BioVentures 2014 LLC ("BV LLC") are the direct and indirect general partners of BV 2014 and BV 2014(B). BV LLC is the manager of AM BV2014. MPM Oncology Innovations Fund GP LLC ("MPM OIF GP") is the general partner of MPM OIF. MPM BioImpact LLC ("BioImpact") is the General Partner of Oncology Impact Fund (Cayman) Management L.P., the General Partner of UBS Oncology. Ansbert Gadicke is a member of AM LLC, a managing director of BV LLC, a manager of MPM OIF GP and the managing partner of BioImpact. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest therein. The shares are held as follows: 384,621 by AM LLC, 2,429,001 by BV 2014, 162,011 by BV 2014(B), 83,604 by AM BV2014, 532,824 by MPM OIF and 2,008,179 by UBS Oncology. The shares were sold as follows: 4,232 by AM LLC, 26,736 by BV 2014, 1,783 by BV 2014(B), 921 by AM BV2014, 5,888 by MPM OIF and 22,080 by UBS Oncology. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.895 to $0.9551 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The shares are held as follows: 380,389 by AM LLC, 2,402,265 by BV 2014, 160,228 by BV 2014(B), 82,683 by AM BV2014, 526,936 by MPM OIF and 1,986,099 by UBS Oncology. The shares were sold as follows: 3,918 by AM LLC, 24,750 by BV 2014, 1,651 by BV 2014(B), 851 by AM BV2014, 5,451 by MPM OIF and 20,440 by UBS Oncology. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.9183 to $0.99 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The shares are held as follows: 376,471 by AM LLC, 2,377,515 by BV 2014, 158,577 by BV 2014(B), 81,832 by AM BV2014, 521,485 by MPM OIF and 1,965,659 by UBS Oncology.
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Form 4 Insider Transactions: What Each Field Means →
SEC Form 4
FORM 4 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
OMB APPROVAL
OMB Number: 3235-0287
Estimated average burden
hours per response: 0.5
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
X
 Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.
1. Name and Address of Reporting Person*
MPM BioVentures 2014, L.P.
(Last) (First) (Middle)
C/O MPM BIOIMPACT LLC
399 BOYLSTON STREET, SUITE 1100
(Street)
BOSTON MA 02116
(City) (State) (Zip)
2. Issuer Name and Ticker or Trading Symbol
Werewolf Therapeutics, Inc. [ HOWL ] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
Director X 10% Owner
Officer (give title below) Other (specify below)
3. Date of Earliest Transaction (Month/Day/Year)
11/13/2025
4. If Amendment, Date of Original Filed (Month/Day/Year)
 6. Individual or Joint/Group Filing (Check Applicable Line)
Form filed by One Reporting Person
X Form filed by More than One Reporting Person
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 11/13/2025 S(1) 90,951(2) D $0.98(3) 5,600,240 I See Footnotes(4)(5)
Common Stock 11/14/2025 S(1) 61,640(6) D $0.93(7) 5,538,600 I See Footnotes(4)(8)
Common Stock 11/17/2025 S(1) 57,061(9) D $0.95(10) 5,481,539 I See Footnotes(4)(11)
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 6. Date Exercisable and Expiration Date (Month/Day/Year) 7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
1. Name and Address of Reporting Person*
MPM BioVentures 2014, L.P.
(Last) (First) (Middle)
C/O MPM BIOIMPACT LLC
399 BOYLSTON STREET, SUITE 1100
(Street)
BOSTON MA 02116
(City) (State) (Zip)
Relationship of Reporting Person(s) to Issuer
Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
MPM BioVentures 2014 (B), L.P.
(Last) (First) (Middle)
C/O MPM BIOIMPACT
399 BOYLSTON STREET, SUITE 1100
(Street)
BOSTON MA 02116
(City) (State) (Zip)
Relationship of Reporting Person(s) to Issuer
Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
MPM BioVentures 2014 LLC
(Last) (First) (Middle)
C/O MPM BIOIMPACT LLC
399 BOYLSTON STREET, SUITE 1100
(Street)
BOSTON MA 02116
(City) (State) (Zip)
Relationship of Reporting Person(s) to Issuer
Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
MPM BioVentures 2014 GP LLC
(Last) (First) (Middle)
C/O MPM BIOIMPACT LLC
399 BOYLSTON STREET, SUITE 1100
(Street)
BOSTON MA 02116
(City) (State) (Zip)
Relationship of Reporting Person(s) to Issuer
Director X 10% Owner
Officer (give title below) Other (specify below)
1. Name and Address of Reporting Person*
MPM Asset Management Investors BV2014 LLC
(Last) (First) (Middle)
C/O MPM BIOIMPACT LLC
399 BOYLSTON STREET, SUITE 1100
(Street)
BOSTON MA 02116
(City) (State) (Zip)
Relationship of Reporting Person(s) to Issuer
Director X 10% Owner
Officer (give title below) Other (specify below)
Explanation of Responses:
1. Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 dated September 24, 2025.
2. The shares were sold as follows: 6,244 by MPM Asset Management LLC ("AM LLC"), 39,450 by MPM BioVentures 2014, L.P. ("BV 2014"), 2,631 by MPM BioVentures 2014(B), L.P. ("BV 2014(B)"), 1,359 by MPM Asset Management Investors BV2014 LLC ("AM BV2014"), 8,688 by MPM Oncology Innovations Fund, L.P. ("MPM OIF") and 32,579 by UBS Oncology Impact Fund L.P. ("UBS Oncology").
3. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.918 to $1.07 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
4. MPM BioVentures 2014 GP LLC and MPM BioVentures 2014 LLC ("BV LLC") are the direct and indirect general partners of BV 2014 and BV 2014(B). BV LLC is the manager of AM BV2014. MPM Oncology Innovations Fund GP LLC ("MPM OIF GP") is the general partner of MPM OIF. MPM BioImpact LLC ("BioImpact") is the General Partner of Oncology Impact Fund (Cayman) Management L.P., the General Partner of UBS Oncology. Ansbert Gadicke is a member of AM LLC, a managing director of BV LLC, a manager of MPM OIF GP and the managing partner of BioImpact. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest therein.
5. The shares are held as follows: 384,621 by AM LLC, 2,429,001 by BV 2014, 162,011 by BV 2014(B), 83,604 by AM BV2014, 532,824 by MPM OIF and 2,008,179 by UBS Oncology.
6. The shares were sold as follows: 4,232 by AM LLC, 26,736 by BV 2014, 1,783 by BV 2014(B), 921 by AM BV2014, 5,888 by MPM OIF and 22,080 by UBS Oncology.
7. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.895 to $0.9551 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
8. The shares are held as follows: 380,389 by AM LLC, 2,402,265 by BV 2014, 160,228 by BV 2014(B), 82,683 by AM BV2014, 526,936 by MPM OIF and 1,986,099 by UBS Oncology.
9. The shares were sold as follows: 3,918 by AM LLC, 24,750 by BV 2014, 1,651 by BV 2014(B), 851 by AM BV2014, 5,451 by MPM OIF and 20,440 by UBS Oncology.
10. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.9183 to $0.99 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
11. The shares are held as follows: 376,471 by AM LLC, 2,377,515 by BV 2014, 158,577 by BV 2014(B), 81,832 by AM BV2014, 521,485 by MPM OIF and 1,965,659 by UBS Oncology.
Remarks:
This filing is 1 of 2 identical filings due to limitations on number of Reporting Persons. See Form 4 filed by Ansbert Gadicke.
/s/ Ansbert Gadicke, Managing Director of MPM BioVentures 2014 LLC 11/17/2025
/s/ Ansbert Gadicke, Managing Director of MPM BioVentures 2014 LLC, the manager of MPM Asset Management Investors BV2014 LLC 11/17/2025
/s/ Ansbert Gadicke, Managing Director of MPM BioVentures 2014 LLC, the Managing Member of MPM BioVentures 2014 GP LLC, the GP of MPM BioVentures 2014 (B), L.P. 11/17/2025
/s/ Ansbert Gadicke, Managing Director of MPM BioVentures 2014 LLC, the Managing Member of MPM BioVentures 2014 GP LLC, the GP of MPM BioVentures 2014, L.P. 11/17/2025
/s/ Ansbert Gadicke, Managing Director of MPM BioVentures 2014 LLC, the Managing Member of MPM BioVentures 2014 GP LLC 11/17/2025
** Signature of Reporting Person Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

Source: View Original Filing on SEC EDGAR

FAQ

What does the Form 4 filed for Werewolf Therapeutics (HOWL) report?

The Form 4 reports insider sales of Werewolf Therapeutics, Inc. common stock by investment entities associated with MPM BioImpact LLC, which are related to a director and 10% owner of the company.

How many Werewolf Therapeutics (HOWL) shares were sold and at what prices?

The reporting entities sold 90,951 shares at $0.98 on November 13, 61,640 shares at $0.93 on November 14, and 57,061 shares at $0.95 on November 17, all at weighted average prices.

How many Werewolf Therapeutics (HOWL) shares does the reporting group own after these transactions?

After the reported sales, the filing shows 5,481,539 shares of Werewolf Therapeutics common stock indirectly beneficially owned across several MPM-managed funds.

Were the HOWL insider sales made under a Rule 10b5-1 trading plan?

Yes. The filing states that the transactions were effected pursuant to a Rule 10b5-1 trading plan established on September 24, 2025.

Who are the main entities involved in the Werewolf Therapeutics (HOWL) Form 4 filing?

The shares are held through entities including MPM Asset Management LLC, MPM BioVentures 2014, L.P., MPM BioVentures 2014(B), L.P., MPM Asset Management Investors BV2014 LLC, MPM Oncology Innovations Fund, L.P. and UBS Oncology Impact Fund L.P., with oversight roles described for related general partners and managers.

Do the reporting persons claim full beneficial ownership of the HOWL shares?

No. The filing notes that each reporting person disclaims beneficial ownership of the securities except to the extent of his or its pecuniary interest in them.

Why does the Werewolf Therapeutics (HOWL) insider report mention multiple identical filings?

The remarks section explains that this Form 4 is 1 of 2 identical filings, made due to limitations on the number of reporting persons that can be included on a single form.