Cabaletta Bio (CABA) SC 13G Cabaletta Bio / 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 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