Exhibit 1

JOINT FILING AGREEMENT

The undersigned hereby agree that the Statement on Schedule 13D, dated September 16, 2024, with respect to the common stock of MBX Biosciences, Inc. is filed on behalf of each of us pursuant to and in accordance with the provisions of Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended. Each of the undersigned agrees to be responsible for the timely filing of this Statement, and for the completeness and accuracy of the information concerning itself contained therein. This Joint Filing Agreement may be executed in any number of counterparts, all of which taken together shall constitute one and the same instrument.

IN WITNESS WHEREOF, the undersigned have executed this Joint Filing Agreement as of the 23rd day of September 2024.

ORBIMED ADVISORS LLC
By:	/s/ Carl L. Gordon
	Name: Carl L. Gordon
	Title: Member
ORBIMED CAPITAL GP VII LLC
By:	ORBIMED ADVISORS LLC, its managing member
By:	/s/ Carl L. Gordon
	Name: Carl L. Gordon
	Title: Member of OrbiMed Advisors LLC
ORBIMED GENESIS GP LLC
By:	ORBIMED ADVISORS LLC, its managing member
By:	s/ Carl L. Gordon
	Name: Carl L. Gordon
	Title: Member of OrbiMed Advisors LLC