(State or other jurisdiction of

incorporation or organization)

(I.R.S. Employer

Identification No.)

Mitchell S. Bloom

Finnbarr Murphy

Goodwin Procter LLP

100 Northern Avenue

Boston, Massachusetts 02210

+1 617 570 1000

Sophie C. McGrath

Goodwin Procter (UK) LLP

100 Cheapside

London EC2V 6DY

United Kingdom

+44 20 7447 4200

Description

Filed herewith.

/s/ Iraj Ali

Iraj Ali, Ph.D.

Chief Executive Officer and Director

(Principal Executive Officer)

/s/ Robert Coutts

Robert Coutts

Chief Financial Officer

(Principal Financial and Accounting Officer)

/s/ Edwin Moses

Edwin Moses, Ph.D.

/s/ Michael F. Giordano

Michael F. Giordano, M.D.

/s/ Carsten Boess

Carsten Boess

/s/ Bernhard Ehmer

Bernhard Ehmer, M.D.

/s/ Julie O’Neill

Julie O’Neill

Goodwin Procter (UK) LLP

100 Cheapside

London EC2V 6DY

goodwinlaw.com

+44 (0) 20 7447 4200

INTRODUCTION

Purpose

Defined terms and headings

capitalised terms used without definition in this letter or the schedules hereto have the meanings assigned to them in the Registration Statement unless a contrary indication appears; and

headings are for ease of reference only and shall not affect interpretation.

Legal review

an online search at Companies House in respect of information available for inspection on the Company’s file conducted on 4 April 2024;

an enquiry of the Central Index of Winding Up Petitions, London on 4 April 2024 at 10:01 a.m. (London time) ((a) and (b), together, the “Searches”);

an executed copy of the print of the resolutions passed by the shareholders of the Company at a general meeting held on 15 March 2021 approving, inter alia: (i) the allotment of shares by the directors, or the granting of rights to subscribe for, or to convert any security into, shares on a non-preemptive basis up to an aggregate nominal amount of £128,000; and (ii) the adoption of the Plans by the Company (the “Shareholder Resolutions”);

an executed copy of the written resolutions of the board dated 3 April 2024 pursuant to which it was resolved, inter alia that the number of shares available for issue and allotment pursuant to the Plans would be increased by 2,046,636 Shares in accordance with the evergreen provisions of the Plans (the “Board Resolutions” and, together with the Shareholder Resolutions, the “Corporate Approvals”);

a copy of the current articles of association of the Company adopted on 28 June 2021 pursuant to a special resolution of the members of the Company passed on 28 June 2021 (the “Current Articles”), a copy of the certificate of incorporation on change of name and re-registration of a private company as a public company dated 10 February 2021 and a copy of the certificate of incorporation of a private limited company dated 18 November 2020;

a copy of the Plans; and

a copy of the draft Registration Statement.

Applicable law

we have not investigated the laws of any country other than England and we express no opinion in this letter on the laws of any jurisdiction other than England and we assume that no foreign law affects any of the opinions given below. It is assumed that no foreign law which may apply to the matters contemplated by the Registration Statement, the Company, any document or any other matter contemplated by any document would or might affect this letter and/or the opinions given in it; and

we do not undertake or accept any obligation to update this letter and/or the opinions given in it to reflect subsequent changes in English law or factual matters.

Assumptions and reservations

OPINION

the Registration Statement becoming effective under the Securities Act;

that the Corporate Approvals were each passed or will be passed (as appropriate) at either: (i) a meeting which was or will be duly convened and held in accordance with all applicable laws and regulations (including as to quorum); or (ii) in the case of the Board Resolutions, by way of circulating written resolution of the directors pursuant to the terms of the Current Articles and the Companies Act 2006 as amended (the “Act”) (in each case, as applicable);

the Board and the shareholders of the Company having validly approved and adopted the Plans;

the Board or the Remuneration Committee of the Board (the “Remuneration Committee”) having validly resolved to issue and allot the Shares, or grant rights to subscribe for the Shares, at a duly convened and quorate meeting of the Board or the Remuneration Committee or by way of duly passed written resolutions of the Board or the Remuneration Committee in each case in compliance with the Plans, all applicable laws and regulations and such resolutions being in full force and effect and not having been rescinded or amended;

the receipt in full by the Company of payment for the Shares in an amount of “cash consideration” (as defined in section 583(3) of the Act) of not less than the aggregate nominal value for such Shares; and

valid entries having been made in relation to the allotment and issue of the Shares in the books and registers of the Company,

EXTENT OF OPINIONS

DISCLOSURE AND RELIANCE

the genuineness of all signatures, stamps and seals on all documents, the authenticity and completeness of all documents submitted to us as originals, and the conformity to original documents of all documents submitted to us as copies;

that, where a document has been examined by us in draft or specimen form, it will be or has been duly executed in the form of that draft or specimen, and that each of the signed documents examined by us has been duly executed and, where applicable, delivered on behalf of the Company;

that each of the individuals who signs as, or otherwise claims to be, a Director or officer of the Company is the individual whom they claim to be and holds the office they claim to hold;

the accuracy as to factual matters of each document we have reviewed;

that the Current Articles referred to in paragraph 1.3(e) of this letter remain in full force and effect and no alteration has been made or will be made to such articles of association, in each case prior to the date of allotment and issue of any of the Shares (the “Allotment Date”);

on the Allotment Date the Company will comply with all applicable laws to allot and issue the Shares and the Company will receive such amounts as are necessary to fully pay the nominal value of the Shares and any applicable share premium;

valid entries having been made in relation to the allotment and issue of the Shares in the books and registers of the Company;

that all documents, forms and notices which should have been delivered to the Registrar of Companies in respect of the Company have been so delivered, that information revealed by the Searches was complete and accurate in all respects and has not, since the time of the Searches, been altered and that the results of the Searches will remain complete and accurate as at the Allotment Date;

that no event occurs that would prevent the Company from validly allotting and issuing the Shares;

that any allotment and issue of Shares which occurs after the date of this opinion is done in accordance with the terms and limits prescribed by the Corporate Approvals and any other restrictions imposed by either the Board or the members of the Company after the date of this letter;

that any minutes of the meetings of the Directors or the written resolutions of the Directors provided to us in connection with the giving of the opinions in this letter reflect a true record of the proceedings described in them in duly convened, constituted and quorate meetings in which all constitutional, statutory and other formalities (including as required by the Current Articles) were duly observed, and the resolutions set out in the minutes or written resolutions were validly passed and have not been and will not be revoked or varied in such a way as to make the issue and allotment of Shares invalid and remain in full force and effect and will remain so as at the Allotment Date;

that the resolutions set out in the Shareholder Resolutions were validly passed and have not been and will not be revoked or varied and remain in full force and effect and will remain so as at the Allotment Date and that, prior to the Allotment Date, the Company has not allotted shares or granted rights to subscribe for, or to convert any security into, shares pursuant to the Shareholder Resolutions which would, when aggregated with any other allotment of Shares by the Company (whether before or after the date of this letter), result in the Directors exceeding the limits set out in the Shareholder Resolutions;

that in relation to the allotment and issue of the Shares, the Directors have acted and will act in the manner required by sections 171 to 174 of the Act, and there has not been and will not be any bad faith, breach of trust, fraud, coercion, duress or undue influence on the part of any of the directors of the Company;

that the Directors and appropriate officers of the Company have taken all necessary corporate action to approve the allotment and issue of the Shares and all ancillary matters relating thereto;

that the Shares will be sold or allotted and issued in accordance with a duly authorised, executed equity incentive agreement, share option agreement, stock option agreement, restricted share unit agreement or other agreement having similar effect, in each case pursuant to the Plans;

that no Shares or rights to subscribe for Shares have been or shall be offered to the public in the United Kingdom in breach of the Financial Services and Markets Act 2000, as amended (“FSMA”) or of any other United Kingdom laws or regulations concerning offers of securities to the public, and no communication has been or shall be made in relation to the Shares in breach of section 21 of FSMA or any other United Kingdom laws or regulations relating to offers or invitations to subscribe for, or to acquire rights to subscribe for or otherwise acquire, shares or other securities;

that there are no facts or circumstances (and no documents, agreements, instruments or correspondence) which are not apparent from the face of the documents listed in paragraph 1.3 (above) or which have not been disclosed to us that may affect the validity or enforceability of the documents listed in paragraph 1.3 (above) or any obligation therein or otherwise affect the opinions expressed in this letter;

that the Company has not taken any corporate or other action nor have any steps been taken or legal proceedings been started against the Company for the liquidation, winding up, dissolution, reorganisation or bankruptcy of, or for the appointment of a liquidator, receiver, trustee, administrator, administrative receiver or similar officer of, the Company or all or any of its assets (or any analogous proceedings in any jurisdiction) and the Company is not unable to pay its debts as they fall due within the meaning of section 123 of the Insolvency Act 1986, as amended, and will not become unable to pay its debts within the meaning of that section as a result of any of the transactions contemplated herein, is not insolvent and has not been dissolved or declared bankrupt (although the Searches gave no indication that any winding-up, dissolution or administration order or appointment of a receiver, administrator, administrative receiver or similar officer has been made with respect to the Company); and

the Company is not, nor will be, engaging in criminal, misleading, deceptive or unconscionable conduct or seeking to conduct any relevant transaction or any associated activity in a manner or for a purpose which might render any transaction contemplated under any corporate approvals or any associated activity illegal, void or voidable.

the Searches are not capable of revealing conclusively whether or not a winding-up or administration petition or order has been presented or made, a receiver appointed, a company voluntary arrangement proposed or approved or any other insolvency proceeding commenced, and the available records may not be complete or up-to-date. In particular, the Central Registry of Winding-Up Petitions in England may not contain details of administration applications filed, or appointments recorded in or orders made by, district registries and county courts outside London. Searches at Companies House and at the Central Registry of Winding Up Petitions in England are not capable of revealing whether or not a winding up petition or a petition for the making of an administration order has been presented and, further, notice of a winding up order or resolution, notice of an administration order and notice of the appointment of a receiver may not be filed at Companies House immediately and there may be a delay in the relevant notice appearing on the file of the company concerned. Further, not all security interests are registrable, such security interests have not in fact been registered or such security interests have been created by an individual or an entity which is not registered in England. We have not made enquiries of any District Registry or County Court in England;

the opinions set out in this letter are subject to: (i) any limitations arising from applicable laws relating to insolvency, bankruptcy, administration, reorganisation, liquidation, moratoria, schemes or analogous circumstances; and (ii) an English court exercising its discretion under section 426 of the Insolvency Act 1986 (co-operation between courts exercising jurisdiction in relation to insolvency) to assist the courts having the corresponding jurisdiction in any part of the United Kingdom or any relevant country or territory;

we express no opinion as to matters of fact;

we have made no enquiries of any individual connected with the Company;

a certificate, documentation, notification, opinion or the like might be held by the English courts not to be conclusive if it can be shown to have an unreasonable or arbitrary basis or in the event of a manifest error; and

it should be understood that we have not been responsible for investigating or verifying: (i) the accuracy of the facts, including statements of foreign law, or the reasonableness of any statements of opinion, contained in the Registration Statement; or (ii) that no material facts have been omitted from it.

Security

Class

Title⁽¹⁾

Maximum

Aggregate

Offering

Price

Fee

Rate

These shares may be represented by the American Depositary Shares (“ADSs”) of Achilles Therapeutics plc (the “Registrant”). Each ADS represents one ordinary share, nominal value £0.001 per share (each, an “Ordinary Share”). ADSs issuable upon deposit of the Ordinary Shares registered hereby were registered pursuant to a separate Registration Statement on Form F-6 (File No. 333-253945).

Pursuant to Rule 416 under the Securities Act of 1933, as amended (the “Securities Act”), this registration statement (“Registration Statement”) shall also cover any additional Ordinary Shares of the Registrant which become issuable under the above-named plans by reason of any stock dividend, stock split, recapitalization or any other similar transaction effected without the receipt of consideration which results in an increase in the number of the Registrant’s outstanding Ordinary Shares.

Estimated solely for the purpose of calculating the amount of the registration fee and calculated pursuant to Rule 457(c) and Rule 457(h) under the Securities Act based on the average of the high and low sales prices of the registrant’s common stock, as reported by The Nasdaq Global Select Market on April 1, 2024.

Represents an automatic increase on January 1, 2024 to the number of shares available for issuance under the Registrant’s (i) 2021 Omnibus Plan (the “2021 Plan”) and (ii) 2021 Employee Share Purchase Plan (the “ESPP”), pursuant to the terms of the 2021 Plan and the ESPP. Shares available for issuance under the 2021 Plan and the ESPP were previously registered on Form S-8 filed with the Securities and Exchange Commission on April 6, 2021, March 2, 2022 and March 8, 2023 (Registration Nos. 333-255063, 333-263220 and 333-270344)).