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 relating to the Common Stock of Cabaletta Bio, Inc. is being filed with the Securities and Exchange Commission on behalf of each of them.

February 14, 2023

	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