Sec Form 4 Filing - Gray David L. F. @ Vigil Neuroscience, Inc. - 2025-08-05

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Gray David L. F. 2. Issuer Name and Ticker or Trading Symbol Vigil Neuroscience, Inc. [ VIGL] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Science Officer (Last) (First) (Middle) VIGIL NEUROSCIENCE, INC., 100 FORGE ROAD, SUITE 700 3. Date of Earliest Transaction (MM/DD/YY) 08/05/2025 (Street) WATERTOWN, MA02472 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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 Stock Option Award (Right to Buy) $ 3.39 08/05/2025 D( 1 ) 125,000 ( 2 ) ( 2 ) Common Stock 125,000 ( 2 ) 0 D Stock Option Award (Right to Buy) $ 2.19 08/05/2025 D( 1 ) 125,000 ( 2 ) ( 2 ) Common Stock 125,000 ( 2 ) 0 D Stock Option Award (Right to Buy) $ 3.03 08/05/2025 D( 1 ) 267,000 ( 2 ) ( 2 ) Common Stock 267,000 ( 2 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Gray David L. F. VIGIL NEUROSCIENCE, INC. 100 FORGE ROAD, SUITE 700 WATERTOWN, MA02472 Chief Science Officer Signatures /s/ Michael Cohen, Attorney-in-Fact 08/05/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )This Form 4 reports securities disposed pursuant to the Agreement and Plan of Merger (the "Merger Agreement") by and among the Issuer, Sanofi ("Parent"), and Vesper Acquisition Sub Inc., a wholly owned subsidiary of Parent ("Merger Sub"). Pursuant to the terms of the Merger Agreement, on August 5, 2025 (the "Effective Time"), Merger Sub merged with and into the Issuer (the "Merger"), with the Issuer continuing as the surviving corporation in the Merger and as a wholly owned subsidiary of Parent. At the Effective Time, each share of Issuer Common Stock issued and outstanding immediately prior to the Effective Time was converted into the right to receive (i) $8.00 per share of Common Stock in cash, without interest (the "Closing Amount") plus (ii) one contingent value right ("CVR"), representing the right to receive $2.00 payable in cash, conditioned upon satisfaction of a certain clinical milestone (together with the Closing Amount, the "Merger Consideration"). ( 2 )Pursuant to the terms of the Merger Agreement, at the Effective Time, each stock option that was outstanding as of immediately prior to the Effective Time, to the extent unvested, was accelerated and became fully vested. Each stock option having an exercise price per share that was less than the Closing Amount was cancelled and converted into the right to receive (i) an amount, without interest, equal to the product of (a) the total number of shares subject to such option immediately prior to the Effective Time, multiplied by (b) the excess of (1) the Closing Amount over (2) the exercise price per share under such option and (ii) one CVR for each share subject to such option.

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).

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