ACHL Achilles Therapeutics PLC

Names of Reporting Persons.

RA Capital Management, L.P.

Names of Reporting Persons.

Peter Kolchinsky

Names of Reporting Persons.

Rajeev Shah

CUSIP No. 00449L102

Names of Reporting Persons.

RA Capital Healthcare Fund, L.P.

Item 1 of the Statement is hereby amended and supplemented as follows:

This Amendment No. 3 amends and supplements the statement on Schedule 13D originally filed with the Securities and Exchange Commission on April 16, 2021, as amended by Amendment No. 1 filed on December 15, 2022, as amended by Amendment No. 2 filed on December 23, 2022 (as so amended, the “Statement”) by the Reporting Persons with respect to the Ordinary Shares, nominal value £0.001 per share per share (“Ordinary Shares”) of Achilles Therapeutics plc, a public limited company incorporated under the laws of England and Wales (the “Issuer”), which has its principal executive offices at 245 Hammersmith Road, London W6 8PW, United Kingdom. Unless otherwise defined herein, capitalized terms used in this Amendment No. 3 shall have the meanings ascribed to them in the Statement. Unless amended or supplemented below, the information in the Statement remains unchanged.

(a)   This Schedule 13D is being filed on behalf of RA Capital Management, L.P. (“RA Capital”), Peter Kolchinsky, Rajeev Shah, and RA Capital Healthcare Fund, L.P. (the “Fund”) who are collectively referred to herein as the “Reporting Persons”.  

The ADS reported herein include 1,298,843 ADS held by the Fund and 308,991 ADS held by RA Capital Nexus Fund, L.P. (the “Nexus Fund”). All options (right to purchase), that were previously held by Dr. Derek DiRocco for the benefit of RA Capital expired unexercised as of November 3, 2022.

RA Capital Healthcare Fund GP, LLC is the general partner of the Fund and RA Capital Nexus Fund GP, LLC is the general partner of the Nexus Fund. The general partner of RA Capital is RA Capital Management GP, LLC, of which Dr. Kolchinsky and Mr. Shah are the controlling persons. RA Capital serves as investment adviser for the Fund and the Nexus Fund, and may be deemed a beneficial owner, for purposes of Section 13(d) of the Exchange Act, of any securities of the Issuer held by the Fund or the Nexus Fund.  The Fund and the Nexus Fund have delegated to RA Capital the sole power to vote and the sole power to dispose of all securities held in the Fund’s and the Nexus Fund’s portfolio, including the ADS reported herein.  Because the Fund and the Nexus Fund have divested themselves of voting and investment power over the reported securities they hold and may not revoke that delegation on less than 61 days’ notice, the Fund and the Nexus Fund disclaim beneficial ownership of the securities they hold for purposes of Section 13(d) of the Act and therefore disclaim any obligation to report ownership of the reported securities under Section 13(d) of the Exchange Act. As managers of RA Capital, Dr. Kolchinsky and Mr. Shah may be deemed beneficial owners, for purposes of Section 13(d) of the Act, of any securities of the Issuer beneficially owned by RA Capital.  RA Capital, Dr. Kolchinsky, and Mr. Shah disclaim beneficial ownership of the securities reported in this Statement other than for the purpose of determining their obligations under Section 13(d) of the Act, and the filing of the Statement shall not be deemed an admission that either RA Capital, Dr. Kolchinsky, or Mr. Shah is the beneficial owner of such securities for any other purpose.

(b)   The address of the principal business office of each of the Reporting Persons is 200 Berkeley Street, 18th Floor, Boston, MA 02116.

(c)   The Fund is a private investment vehicle. RA Capital provides investment management services to the Fund and the Nexus Fund. The principal occupation of Dr. Kolchinsky and Mr. Shah is investment management.

(d)   During the last five years, none of the Reporting Persons has been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).

(e)   During the last five years, none of the Reporting Persons has been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree of final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

(f)    See row 6 of the cover pages.    

Item 5 of the Statement is amended and restated as follows:

(a)   The information set forth in rows 11 and 13 of the cover pages to this Statement is incorporated herein by reference. The percentages set forth in row 13 of the cover pages are based on 40,938,763 outstanding Ordinary Shares of the Issuer as reported in the Issuer’s Form 6-K, Exhibit 99.1 filed with the Securities and Exchange Commission (“SEC”) on November 8, 2022.

(b)   The information set forth in rows 7 through 10 of the cover pages to this Statement and Item 2 above is incorporated herein by reference.

(c)   Schedule A sets forth all transactions with respect to the ADS that have not previously been reported during the past sixty days by any Reporting Person and is incorporated herein by reference.

(d)   No person (other than the Reporting Persons) is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the ADS subject to this Statement.

(e)   On December 29, 2022 the reporting persons ceased being owners of more than 5% of the issuer's outstanding common stock.

Exhibit 1    Joint Filing Agreement