Sec Form 4 Filing - Booth Bruce @ 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 Booth Bruce 2. Issuer Name and Ticker or Trading Symbol Vigil Neuroscience, Inc. [ VIGL] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (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 Common Stock 08/05/2025 D( 1 ) 5,000 ( 2 ) D 0 D ( 3 ) Common Stock 08/05/2025 D( 1 ) 4,808,896 D 0 I By Atlas Venture Fund XII, L.P. ( 4 ) Common Stock 08/05/2025 D( 1 ) 1,027,978 D 0 I By Atlas Venture Opportunity Fund I, L.P. ( 5 )

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) $ 3.03 08/05/2025 D( 1 ) 7,577 ( 6 ) ( 6 ) Common Stock 7,577 ( 5 ) 0 D ( 3 ) Stock Option Award (Right to Buy) $ 3.03 08/05/2025 D( 1 ) 12,155 ( 6 ) ( 6 ) Common Stock 12,155 ( 5 ) 0 D ( 3 ) Stock Option Award (Right to Buy) $ 3.03 08/05/2025 D( 1 ) 9,713 ( 6 ) ( 6 ) Common Stock 9,713 ( 5 ) 0 D ( 3 ) Stock Option Award (Right to Buy) $ 3.03 08/05/2025 D( 1 ) 13,928 ( 6 ) ( 6 ) Common Stock 13,928 ( 5 ) 0 D ( 3 ) Stock Option Award (Right to Buy) $ 3.39 08/05/2025 D( 1 ) 34,612 ( 6 ) ( 6 ) Common Stock 34,612 ( 5 ) 0 D ( 3 ) Stock Option Award (Right to Buy) $ 3.38 08/05/2025 D( 1 ) 18,068 ( 6 ) ( 6 ) Common Stock 18,068 ( 5 ) 0 D ( 3 ) Stock Option Award (Right to Buy) $ 2.19 08/05/2025 D( 1 ) 48,393 ( 6 ) ( 6 ) Common Stock 48,393 ( 5 ) 0 D ( 3 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Booth Bruce VIGIL NEUROSCIENCE, INC. 100 FORGE ROAD, SUITE 700 WATERTOWN, MA02472 X Signatures /s/ Ommer Chohan, 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 )Represents Restricted Stock Units ("RSUs"), each of which represented the contingent right to receive one share of the Common Stock. Pursuant to the terms of the Merger Agreement, at the Effective Time, each RSU that is outstanding as of immediately prior to the Effective Time, to the extent unvested, was accelerated and became fully vested, and 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 RSU immediately prior to the Effective Time, multiplied by (b) the Closing Amount and (ii) one CVR for each share subject to such RSU. ( 3 )The Reporting Person is a member of Atlas Venture Associates XII, LLC and is obligated to transfer the economic benefit, if any, received upon the sale of the shares issuable upon settlement of this award to Atlas Venture Life Science Advisors, LLC. As such, the Reporting Person disclaims beneficial owner ship of the securities reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, except to the extent of his pecuniary interest therein, if any. ( 4 )These shares are held directly by Atlas Venture Fund XII, L.P. ("Atlas Venture Fund XII"). The general partner of Atlas Venture Fund XII is Atlas Venture Associates XII, L.P. ("AVA XII LP"). Atlas Venture Associates XII, LLC ("AVA XII LLC") is the general partner of AVA XII LP. The Reporting Person is a member of AVA XII LLC and disclaims beneficial ownership of such securities held by Atlas Venture Fund XII, except to the extent of his pecuniary interest therein, if any. ( 5 )The shares are held directly by Atlas Venture Opportunity Fund I, L.P. ("Atlas Venture Opportunity Fund I"). The general partner of Atlas Venture Opportunity Fund I is Atlas Venture Associates Opportunity I, L.P. ("AVAO I LP"). Atlas Venture Associates Opportunity I, LLC ("AVAO I LLC") is the general partner of AVAO I LP. The Reporting Person is a member of AVAO I LLC and disclaims beneficial ownership of such securities held by Atlas Venture Opportunity Fund I, except to the extent of his pecuniary interest therein, if any. ( 6 )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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