CONTINGENT VALUE RIGHTS AGREEMENT By and between SANOFI and COMPUTERSHARE INC. and COMPUTERSHARE TRUST COMPANY, N.A., collectively, as Rights Agent Dated as of

CONTINGENT VALUE RIGHTS

COMPUTERSHARE INC. and

COMPUTERSHARE TRUST COMPANY, N.A.,

collectively, as Rights Agent

Dated as of August 5, 2025

Annex A Form of Assignment and Assumption Agreement

CONTINGENT VALUE RIGHTS AGREEMENT

This CONTINGENT VALUE RIGHTS AGREEMENT, dated as of August 5, 2025 (this Agreement ), by and between Sanofi, a French

soci t anonyme ( Parent ), and Computershare Inc., a Delaware corporation ( Computershare ), and its affiliate, Computershare Trust Company, N.A., a national banking association (the

Trust Company , and collectively, with Computershare, the Rights Agent ).

WHEREAS, this Agreement is entered into pursuant to the Agreement and Plan of Merger, dated May 21, 2025 (as amended, restated,

supplemented, waived or otherwise modified from time to time, the Merger Agreement ), by and among Vigil Neuroscience, Inc., a Delaware corporation (the Company ), Parent and Vesper Acquisition Sub Inc., a

Delaware corporation wholly owned by Parent ( Merger Sub ), pursuant to which Merger Sub will be merged with and into the Company (the Merger ), with the Company continuing as the surviving corporation in the

Merger and as a wholly owned Subsidiary of Parent (the Surviving Corporation ), on the terms and subject to the conditions set forth therein; and

WHEREAS, pursuant to the terms of the Merger Agreement, as a result of the consummation of the Merger, the holders of Shares that are

entitled to receive the Merger Consideration pursuant to Section 1.5(a)(iii) of the Merger Agreement, certain holders of Company Equity Awards and the holders of Company Warrants will become entitled to receive the

Milestone Payment contingent upon the achievement of the Milestone during the Milestone Period, subject to the terms and conditions of this Agreement.

NOW, THEREFORE, in consideration of the foregoing and the consummation of the transactions referred to above, Parent and the Rights

Agent agree, for the equal and proportionate benefit of all Holders (as hereinafter defined), as follows:

Section 1.1 Definitions. Capitalized terms used in this Agreement and not otherwise defined shall have the meanings assigned to

them in the Merger Agreement. For purposes of this Agreement, the following terms shall have the following meanings:

Holders means, at the time of determination, Holders of at least a majority of the outstanding CVRs as set forth in the CVR Register.

Affiliate means, as to any Person, any other Person that, directly or indirectly, controls, or is controlled by, or is

under common control with, such Person. For this purpose, control (including, with its correlative meanings, controlled by and under common control with ) means the possession, directly or indirectly, of the power

to direct or cause the direction of management or policies of a Person, whether through the ownership of securities or partnership or other ownership interests, by Contract or otherwise.

Assignment Transaction means any transaction (including a sale of assets,

spin-off, split-off or licensing transaction), other than a Change in Control, pursuant to which rights in and to the Product are sold, licensed, assigned or transferred

to or acquired by any Person other than Parent or its Affiliates. For purposes of clarification, an Assignment Transaction shall not apply to licensing arrangements between Parent or its Affiliates, on the one hand, and third

party licensees, distributors and contract manufacturers, on the other hand, entered into in the ordinary course of business for purposes of developing, manufacturing, distributing or selling the Product.

Business Day means a day except a Saturday, a Sunday or other day on which banks in the City of New York, NY, USA or Paris,

France are authorized or required by Legal Requirements to be closed.

Change in Control means (a) a sale or other

disposition of all or substantially all of the assets of Parent on a consolidated basis, (b) a merger, consolidation or other business combination involving Parent in which Parent is not the surviving entity or (c) any transaction

(including (i) any issuance of securities and (ii) a merger, consolidation or other business combination in which Parent is the surviving entity) involving Parent in which the holders of voting securities of Parent immediately prior to

such transaction collectively own securities representing less than 50% of Parent s voting power immediately after such transaction, in the case of each of the foregoing clauses (a), (b) and (c), whether effected directly or indirectly, and

whether effected in a single transaction or a series of related transactions.

Closing Date Underwater Options means

the Company Options referred to in Section 1.8(a)(iii) of the Merger Agreement.

Stock means the common stock, $0.0001 par value per share, of the Company.

Company Equity Award means any

Company Option that is outstanding and unexercised and any Company RSU that is outstanding, in each case as of immediately prior to the Effective Time.

Company Equity Plans means the Company s 2021 Stock Option and Incentive Plan and the Company s Amended and

Restated 2020 Equity Incentive Plan, as amended.

Company Options means all options to purchase Shares granted under

the Company Equity Plans or otherwise, other than those that are cancelled without any consideration being payable in respect thereof in accordance with Section 1.8(a)(iv) of the Merger Agreement.

Company RSU means each restricted stock unit award with respect to Shares granted under a Company Equity Plan or otherwise.

Company Warrant Holder means a Holder of a CVR granted in accordance with the terms of the Merger Agreement with

respect to a Company Warrant.

Company Warrants means the pre-funded warrants

to purchase up to an aggregate of 2,980,889 Shares issued to certain accredited investors in connection with the Securities Purchase Agreement, dated as of August 12, 2022, by and among the Company and the other parties therein.

Cover means, with respect to a given product or a component thereof and a

Valid Claim, that such Valid Claim would, absent a license thereunder or ownership thereof, be infringed by the making, having made, use, sale, offer for sale or importation of such product or component.

CVRs means the contingent rights of the Holders to receive the Milestone Payment pursuant to this Agreement.

Diligent Efforts means, with respect to the Product, efforts of a Person to carry out its obligations in a diligent and

sustained manner without undue pause, interruption or delay, which level is at least commensurate with the level of efforts that a pharmaceutical company of comparable size and resources as those of Parent and its Affiliates would devote to the

development and seeking of regulatory approval (including FDA Approval), for a pharmaceutical product having similar market potential as the Product, at a similar stage of its development or product life, taking into account issues of market

exclusivity, product profile, including safety, tolerability and efficacy, the competitiveness of alternate products in the marketplace or under development, the availability of existing forms or dosages of the Product for other indications, the

launch or sales of a generic product, the regulatory environment and the profitability of the Product (including pricing and reimbursement status achieved), Parent and its Affiliates portfolio at the time of consideration and other technical,

commercial, legal, scientific or medical factors; provided, that such level of efforts and resources shall be determined without taking into account the fact of the potential Milestone Payment payable in accordance with, and subject to, the

terms of this Agreement.

Entity means any corporation (including any

non-profit corporation), general partnership, limited partnership, limited liability partnership, joint venture, estate, trust, company (including any company limited by shares, limited liability company or

joint stock company), firm, society or other enterprise, association, organization or entity.

means a Holder of a CVR granted in accordance with the terms of the Merger Agreement with respect to a Company Equity Award.

FDA means the U.S. Food and Drug Administration, or any successor agency.

FDA Approval means, with respect to a pharmaceutical product, any regulatory approval, licensure or authorization granted

by the FDA, where such approval, licensure or authorization is required for the recipient to commence marketing or selling such pharmaceutical product in the United States.

First Commercial Sale means, with respect to the Product, the first sale of the Product for monetary value in the U.S. by

Parent or its Affiliates (including the Surviving Corporation) or (sub)licensees following FDA Approval in the Indication, and for which any of Parent or its Affiliates (including the Surviving Corporation) or (sub)licensees has invoiced sales of

the Product in the US; provided, however, that the following will not constitute a First Commercial Sale: (a) any sale to any of Parent s Affiliates or (sub)licensees, unless such Affiliate or (sub)licensee is the last person

in the distribution chain of the Product; (b) any use by or on behalf of Parent or its Affiliates or (sub)licensees of the Product in clinical trials or non-clinical development activities; or

(c) any disposal or transfer of the Product for a bona fide charitable purpose, compassionate use or as samples, treatment IND sales , named patient sales , expanded access sales , right to try sales

Governmental Body means any: (a) nation, state, commonwealth,

province, territory, county, municipality, district or other jurisdiction of any nature; (b) federal, state, local, municipal, foreign or other government; or (c) governmental or quasi-governmental authority of any nature including any

governmental division, department, agency, commission, instrumentality, official, ministry, fund, foundation, center, organization, unit, body or Entity and any court, arbitrator or other tribunal.

Holder means a Person in whose name a CVR is registered in the CVR Register at the applicable time.

Indication means Alzheimer s Disease, as defined by the National Institute of Aging Alzheimer s Association

diagnostic criteria.

Legal Proceeding means any action, suit, charge, complaint, litigation, arbitration, proceeding

(including any civil, criminal, administrative, investigative or appellate proceeding), hearing, inquiry, audit, examination or investigation commenced, brought, conducted or heard by or before, or otherwise involving, any court or other

Governmental Body or any arbitrator or arbitration panel.

Legal Requirement means any applicable federal, state,

local, municipal, foreign or other law, statute, constitution, principle of common law, resolution, ordinance, code, edict, decree, rule, regulation, ruling or requirement issued, enacted, adopted, promulgated, implemented or otherwise put into

effect by or under the authority of any Governmental Body (or under the authority of Nasdaq).

Milestone means First

Commercial Sale of the Product.

Milestone Patent means (a) any Patent owned or exclusively licensed by the

Company as of the Effective Time and (b) any Patent owned or exclusively licensed by the Company that claims priority to any Patent within the scope of preceding clause (a).

Milestone Payment Amount means, for a given Holder, with respect to the achievement of the Milestone, a one-time payment equal to (a) in the case of CVRs held by such Holder other than CVRs issued in respect of Closing Date Underwater Options, the product of (i) the Milestone Payment multiplied by

(ii) the number of such CVRs held by such Holder as reflected on the CVR Register as of the close of business on the date of the Milestone Achievement Notice, and (b) in the case of CVRs held by such Holder issued in respect of Closing

Date Underwater Options, the product of (i) the Underwater Option Milestone Payment multiplied by (ii) the number of such CVRs held by such Holder as reflected on the CVR Register as of the close of business on the date of the Milestone

Milestone Payment means an amount per CVR equal to $2.00 in cash, without interest.

Milestone Payment Date means the date selected by Parent for the payment

of the Milestone Payment, which shall be not more than thirty (30) Business Days after the date on which the Milestone was achieved.

Milestone Period means the period commencing as of the Effective Time and ending at 11:59 PM EST on December 31, 2035.

Officer s Certificate means a certificate signed by the chief executive officer, chief financial

officer, any vice president, the controller, the treasurer or the secretary, in each case of Parent, in his or her capacity as such an officer (and not in any individual capacity), and delivered to the Rights Agent or any other person authorized to

act on behalf of Parent.