UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO RULES 13d-1(b), (c), AND (d) AND AMENDMENTS THERETO FILED

PURSUANT TO RULE 13d-2(b)

(Amendment No. )¹

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

1              The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

(1) Includes 496,795 Shares (as defined in Item 2) underlying certain Pre-Funded Warrants (as defined in Item 4). The Pre-Funded Warrants are subject to the Pre-Funded Warrants Blocker (as defined in Item 4).

(1) Includes 496,795 Shares underlying certain Pre-Funded Warrants. The Pre-Funded Warrants are subject to the Pre-Funded Warrants Blocker.

(1) Includes 373,039 Shares underlying certain Pre-Funded Warrants. The Pre-Funded Warrants are subject to the Pre-Funded Warrants Blocker.

(1) Includes 373,039 Shares underlying certain Pre-Funded Warrants. The Pre-Funded Warrants are subject to the Pre-Funded Warrants Blocker.

(1) Includes 43,602 Shares underlying certain Pre-Funded Warrants. The Pre-Funded Warrants are subject to the Pre-Funded Warrants Blocker.

(1) Includes 43,602 Shares underlying certain Pre-Funded Warrants. The Pre-Funded Warrants are subject to the Pre-Funded Warrants Blocker.

(1) Includes 869,834 Shares underlying certain Pre-Funded Warrants. The Pre-Funded Warrants are subject to the Pre-Funded Warrants Blocker.

(1) Includes 926,094 Shares underlying certain Pre-Funded Warrants. The Pre-Funded Warrants are subject to the Pre-Funded Warrants Blocker.

(1) Includes 926,094 Shares underlying certain Pre-Funded Warrants. The Pre-Funded Warrants are subject to the Pre-Funded Warrants Blocker.

(1) Includes 926,094 Shares underlying certain Pre-Funded Warrants. The Pre-Funded Warrants are subject to the Pre-Funded Warrants Blocker.

Vigil Neuroscience, Inc., a Delaware corporation (the “Issuer”).

1 Broadway, 7^th Floor, Suite 07-300

Cambridge, Massachusetts 02142

Biotechnology Value Fund, L.P. (“BVF”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF I GP LLC (“BVF GP”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

Biotechnology Value Fund II, L.P. (“BVF2”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF II GP LLC (“BVF2 GP”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

Biotechnology Value Trading Fund OS LP (“Trading Fund OS”)

PO Box 309 Ugland House

Grand Cayman, KY1-1104

Cayman Islands

Citizenship: Cayman Islands

BVF Partners OS Ltd. (“Partners OS”)

PO Box 309 Ugland House

Grand Cayman, KY1-1104

Cayman Islands

Citizenship: Cayman Islands

BVF GP Holdings LLC (“BVF GPH”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF Partners L.P. (“Partners”)
44 Montgomery St., 40th Floor
San Francisco, California 94104
Citizenship: Delaware

BVF Inc.

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

Mark N. Lampert (“Mr. Lampert”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: United States

Each of the foregoing is referred to as a “Reporting Person” and collectively as the “Reporting Persons.”

Common Stock, par value $0.0001 per share (the “Shares”)

92673K108

As of the close of business on August 26, 2022, the Reporting Persons hold an aggregate of 926,094 pre-funded warrants (the “Pre-Funded Warrants”) exercisable for an aggregate of 926,094 Shares. Each Pre-Funded Warrant is exercisable for one Share at an exercise price of $0.0001. The Pre-Funded Warrants are immediately exercisable and have no expiration date. A holder of a Pre-Funded Warrant will not be entitled to exercise any portion of such Pre-Funded Warrant that, upon giving effect to such exercise, would cause the aggregate number of Shares beneficially owned by such holder (together with its affiliates and any other persons whose beneficial ownership of Shares would be aggregated with the holder for purposes of Section 13(d) of the Exchange Act) to exceed 9.99% of the total number of then issued and outstanding Shares, as such percentage ownership is determined in accordance with the terms of the Pre-Funded Warrant and subject to such holder’s rights under the Pre-Funded Warrant to increase or decrease such percentage to any other percentage not in excess of 19.99% upon at least 61 days’ prior notice from such holder to the Issuer (the “Pre-Funded Warrants Blocker”). As of August 26, 2022, the Pre-Funded Warrants Blocker does not limit the aggregate exercise of the Pre-Funded Warrants by the Reporting Persons.

As of the close of business on August 26, 2022 (i) BVF beneficially owned 1,469,702 Shares, including 496,795 Shares underlying the Pre-Funded Warrants held by it; (ii) BVF2 beneficially owned 1,103,586 Shares, including 373,039 Shares underlying the Pre-Funded Warrants held by it; and (iii) Trading Fund OS beneficially owned 128,991 Shares, including 43,602 Shares underlying the Pre-Funded Warrants held by it.

BVF GP, as the general partner of BVF, may be deemed to beneficially own the 1,469,702 Shares beneficially owned by BVF.

BVF2 GP, as the general partner of BVF2, may be deemed to beneficially own the 1,103,586 Shares beneficially owned by BVF2.

Partners OS, as the general partner of Trading Fund OS, may be deemed to beneficially own the 128,991 Shares beneficially owned by Trading Fund OS.

BVF GPH, as the sole member of each of BVF GP and BVF2 GP, may be deemed to beneficially own the 2,573,288 Shares beneficially owned in the aggregate by BVF and BVF2.

Partners, as the investment manager of BVF, BVF2 and Trading Fund OS, and the sole member of Partners OS, may be deemed to beneficially own the 2,739,727 Shares beneficially owned in the aggregate by BVF, BVF2 and Trading Fund OS and held in a certain Partners managed account (the “Partners Managed Account”), including 37,448 Shares, which includes 12,658 Shares underlying the Pre-Funded Warrants held in the Partners Managed Account.

BVF Inc., as the general partner of Partners, may be deemed to beneficially own the 2,739,727 Shares beneficially owned by Partners.

Mr. Lampert, as a director and officer of BVF Inc., may be deemed to beneficially own the 2,739,727 Shares beneficially owned by BVF Inc.

The foregoing should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of any Shares owned by another Reporting Person. BVF GP disclaims beneficial ownership of the Shares beneficially owned by BVF. BVF2 GP disclaims beneficial ownership of the Shares beneficially owned by BVF2. Partners OS disclaims beneficial ownership of the Shares beneficially owned by Trading Fund OS. BVF GPH disclaims beneficial ownership of the Shares beneficially owned by BVF and BVF2. Each of Partners, BVF Inc. and Mr. Lampert disclaims beneficial ownership of the Shares beneficially owned by BVF, BVF2 and Trading Fund OS and held in the Partners Managed Accounts, and the filing of this statement shall not be construed as an admission that any such person or entity is the beneficial owner of any such securities.

The following percentages are based on a denominator that is the sum of (i) 28,268,331 Shares outstanding, as of July 31, 2022, which is the total number of Shares outstanding as reported in the Issuer’s Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (the “SEC”) on August 8, 2022, (ii) 7,293,084 Shares issued in connection with a private placement financing by the Issuer that closed on August 16, 2022, as reported in the Issuer’s Current Report on Form 8-K filed with the SEC on August 12, 2022 and (iii) certain or all of the 926,094 Shares issuable upon the exercise of the Pre-Funded Warrants owned by the Reporting Persons, as applicable.

As of the close of business on August 26, 2022, (i) BVF beneficially owned approximately 4.1% of the outstanding Shares, (ii) BVF2 beneficially owned approximately 3.1% of the outstanding Shares, (iii) Trading Fund OS beneficially owned less than 1% of the outstanding Shares, (iv) BVF GP may be deemed to beneficially own approximately 4.1% of the outstanding Shares, (v) BVF2 GP may be deemed to beneficially own approximately 3.1% of the outstanding Shares, (vi) Partners OS may be deemed to beneficially own less than 1% of the outstanding Shares, (vii) BVF GPH may be deemed to beneficially own approximately 7.2% of the outstanding Shares, and (viii) each of Partners, BVF Inc. and Mr. Lampert may be deemed to beneficially own approximately 7.5% of the outstanding Shares (less than 1% of the outstanding Shares are held in the Partners Managed Account).

See Cover Pages Items 5-9.

See Cover Pages Items 5-9.

See Cover Pages Items 5-9.

See Cover Pages Items 5-9.

Not Applicable.

BVF GPH, Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the Shares beneficially owned by BVF and BVF2. Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the Shares beneficially owned by Trading Fund OS and held in the Partners Managed Account.

Not Applicable.

See Exhibit 99.1.

Not Applicable.

By signing below each of the undersigned certifies that, to the best of its knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

SIGNATURE

After reasonable inquiry and to the best of his knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: August 26, 2022