Evnin-linked funds sell 171K Werewolf Therapeutics (HOWL) shares

Rhea-AI Filing Summary

Werewolf Therapeutics, Inc. director Luke Evnin reported three indirect open-market sales of Common Stock by affiliated investment entities. Across May 18–20, 2026, these entities sold a total of 171,049 shares at reported weighted average prices of $0.50, $0.45 and $0.43 per share. The trades were effected under a Rule 10b5-1 trading plan dated March 26, 2026. After these sales, the affiliated entities together held 955,447 shares, and Evnin disclaims beneficial ownership beyond his pecuniary interest.

Insider Trade Summary 10b5-1

Net Seller: 171,049 shares ($76,363)

Net Sell 3 txns

Insider EVNIN LUKE

Role null

Sold 171,049 shs ($76K)

Type	Security	Shares	Price	Value
Sale	Common Stock	85,895	$0.43	$37K
Sale	Common Stock	62,970	$0.45	$28K
Sale	Common Stock	22,184	$0.50	$11K

Holdings After Transaction: Common Stock — 955,447 shares (Indirect, See Footnotes)

Footnotes (1)

1. Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 dated March 26, 2026. The shares were sold as follows: 2,377 by MPM Asset Management LLC ("AM LLC"), 15,006 by MPM BioVentures 2014, L.P. ("BV 2014"), 1,001 by MPM BIoVentures 2014(B), L.P. ("BV 2014(B)"), 517 by MPM Asset Management Investors BV2014 LLC ("AM BV2014") and 3,283 by MPM Oncology Innovations Fund, L.P. ("MPM OIF"). The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.4931 to $0.5059 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. Luke Evnin is a member of AM LLC, a Managing Director of BV LLC and a manager of MPM OIF GP. The Reporting Person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein. The shares are held as follows: 118,316 by AM LLC, 747,025 by BV 2014, 49,823 by BV 2014(B), 25,710 by AM BV2014 and 163,438 by MPM OIF. The shares were sold as follows: 6,747 by AM LLC, 42,596 by BV 2014, 2,841 by BV 2014(B), 1,466 by AM BV2014 and 9,320 by MPM OIF. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.4243 to $0.50 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: 111,569 by AM LLC, 704,429 by BV 2014, 46,982 by BV 2014(B), 24,244 by AM BV2014 and 154,118 by MPM OIF. The shares were sold as follows: 9,203 by AM LLC, 58,105 by BV 2014, 3,875 by BV 2014(B), 2,000 by AM BV2014 and 12,712 by MPM OIF. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.40905 to $0.4455 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: 102,366 by AM LLC, 646,324 by BV 2014, 43,107 by BV 2014(B), 22,244 by AM BV2014 and 141,406 by MPM OIF.

Key Figures

Total shares sold: 171,049 shares Shares sold May 18, 2026: 22,184 shares Shares sold May 19, 2026: 62,970 shares +5 more

8 metrics

Total shares sold 171,049 shares Net open-market sales over May 18–20, 2026

Shares sold May 18, 2026 22,184 shares Open-market sale at $0.50 per share

Shares sold May 19, 2026 62,970 shares Open-market sale at $0.45 per share

Shares sold May 20, 2026 85,895 shares Open-market sale at $0.43 per share

Holdings after transactions 955,447 shares Indirect holdings by affiliated entities following sales

Price range May 18 trades $0.4931–$0.5059 Weighted average price $0.50 per share

Price range May 19 trades $0.4243–$0.50 Weighted average price $0.45 per share

Price range May 20 trades $0.40905–$0.4455 Weighted average price $0.43 per share

Key Terms

Rule 10b5-1, weighted average price, open-market sale, pecuniary interest, +1 more

5 terms

Rule 10b5-1 regulatory

"Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 dated March 26, 2026."

Rule 10b5-1 is a regulation that allows company insiders to buy or sell their shares at predetermined times, even if they have access to non-public information. It acts like setting a schedule in advance for transactions, helping prevent accusations of unfair trading. This rule provides a way for insiders to plan trades transparently, giving investors confidence that these transactions are not based on hidden information.

weighted average price financial

"The price reported in Column 4 is a weighted average price."

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

open-market sale financial

"transaction_action": "open-market sale""

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

pecuniary interest financial

"The Reporting Person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein."

beneficial ownership financial

"The Reporting Person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein."

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

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^*

EVNIN LUKE

(Last) (First) (Middle)

C/O MPM BIOIMPACT LLC

399 BOYLSTON STREET, SUITE 1100

(Street)

BOSTON MASSACHUSETTS 02116

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Werewolf Therapeutics, Inc. [ HOWL ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/18/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	05/18/2026		S(1)		22,184(2)	D	$0.5(3)	1,104,312	I	See Footnotes(4)(5)
Common Stock	05/19/2026		S(1)		62,970(6)	D	$0.45(7)	1,041,342	I	See Footnotes(4)(8)
Common Stock	05/20/2026		S(1)		85,895(9)	D	$0.43(10)	955,447	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

Explanation of Responses:

1. Transaction effected pursuant to a plan established pursuant to Rule 10b5-1 dated March 26, 2026.

2. The shares were sold as follows: 2,377 by MPM Asset Management LLC ("AM LLC"), 15,006 by MPM BioVentures 2014, L.P. ("BV 2014"), 1,001 by MPM BIoVentures 2014(B), L.P. ("BV 2014(B)"), 517 by MPM Asset Management Investors BV2014 LLC ("AM BV2014") and 3,283 by MPM Oncology Innovations Fund, L.P. ("MPM OIF").

3. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.4931 to $0.5059 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. Luke Evnin is a member of AM LLC, a Managing Director of BV LLC and a manager of MPM OIF GP. The Reporting Person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein.

5. The shares are held as follows: 118,316 by AM LLC, 747,025 by BV 2014, 49,823 by BV 2014(B), 25,710 by AM BV2014 and 163,438 by MPM OIF.

6. The shares were sold as follows: 6,747 by AM LLC, 42,596 by BV 2014, 2,841 by BV 2014(B), 1,466 by AM BV2014 and 9,320 by MPM OIF.

7. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.4243 to $0.50 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: 111,569 by AM LLC, 704,429 by BV 2014, 46,982 by BV 2014(B), 24,244 by AM BV2014 and 154,118 by MPM OIF.

9. The shares were sold as follows: 9,203 by AM LLC, 58,105 by BV 2014, 3,875 by BV 2014(B), 2,000 by AM BV2014 and 12,712 by MPM OIF.

10. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.40905 to $0.4455 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: 102,366 by AM LLC, 646,324 by BV 2014, 43,107 by BV 2014(B), 22,244 by AM BV2014 and 141,406 by MPM OIF.

	/s/ Luke Evnin	05/20/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

What insider activity did Werewolf Therapeutics (HOWL) report in this Form 4?

The Form 4 reports that entities affiliated with director Luke Evnin sold a total of 171,049 shares of Werewolf Therapeutics Common Stock in three open-market transactions over May 18–20, 2026, at prices between $0.43 and $0.50 per share.

At what prices were the HOWL shares sold by the Evnin-affiliated entities?

The reported weighted average sale prices were $0.50 per share on May 18, 2026, $0.45 per share on May 19, 2026, and $0.43 per share on May 20, 2026, with each day’s trades executed across multiple prices within specified ranges.

How many Werewolf Therapeutics (HOWL) shares do the Evnin-related funds hold after these sales?

Following the reported transactions, the affiliated investment entities together hold 955,447 shares of Werewolf Therapeutics Common Stock. The filing specifies that these holdings are spread across several MPM-managed entities, and Luke Evnin disclaims beneficial ownership beyond his pecuniary interest.

Were the HOWL insider sales by Evnin-affiliated entities under a Rule 10b5-1 plan?

Yes. The filing states the transactions were effected pursuant to a Rule 10b5-1 trading plan dated March 26, 2026. Such plans prearrange trades, indicating these sales were scheduled in advance rather than timed in response to short-term market developments.

Which entities actually sold Werewolf Therapeutics (HOWL) shares in these Form 4 transactions?

The footnotes explain that shares were sold by MPM Asset Management LLC, MPM BioVentures 2014, L.P., MPM BioVentures 2014(B), L.P., MPM Asset Management Investors BV2014 LLC, and MPM Oncology Innovations Fund, L.P., all associated with director Luke Evnin.