Baker Bros. Advisors SC 13G Achilles Therapeutics / BAKER BROS. ADVISORS ownership change

EXHIBIT 99.1

AGREEMENT

In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree that this Statement on Schedule 13G (including additional amendments thereto) relating to the Ordinary Shares of Achilles Therapeutics plc is being filed with the Securities and Exchange Commission on behalf of each of them.

February 14, 2022

BAKER BROS. ADVISORS LP By:     Baker Bros. Advisors (GP) LLC, its general partner
By:	/s/ Scott L. Lessing
	Name: Scott L. Lessing Title: President

BAKER BROS. ADVISORS (GP) LLC
By:	/s/ Scott L. Lessing
	Name: Scott L. Lessing Title: President

/s/ Julian C. Baker

Julian C. Baker

/s/ Felix J. Baker

Felix J. Baker