EXHIBIT A JOINT FILING AGREEMENT

CUSIP No. 00000X000  SCHEDULE 13G Page 8 of 8 Pages

EXHIBIT A

JOINT FILING AGREEMENT

The undersigned hereby agree that the Statement on this Schedule 13G dated February 12, 2021 (the “Schedule 13G”), with respect to the Common Stock, par value $0.0001 per share, of Adverum Biotechnologies, 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, and that this Agreement shall be included as an Exhibit to this Schedule 13G. Each of the undersigned agrees to be responsible for the timely filing of the Schedule 13G, and for the completeness and accuracy of the information concerning itself contained therein. This 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 Agreement as of February 12, 2021.

	OrbiMed Advisors LLC
	By:	/s/ Xxxxxxxx X. Xxxxxxxxxxx
		Name:	Xxxxxxxx X. Xxxxxxxxxxx
		Title:	Member
	By:	/s/ Xxxx X. Xxxxx
		Name:	Xxxx X. Xxxxx
		Title:	Member
	By:	/s/ Xxxx X. Xxxxxx
		Name:	Xxxx X. Xxxxxx
		Title:	Member

	OrbiMed Capital LLC
	By:	/s/ Xxxxxxxx X. Xxxxxxxxxxx
		Name:	Xxxxxxxx X. Xxxxxxxxxxx
		Title:	Member
	By:	/s/ Xxxx X. Xxxxx
		Name:	Xxxx X. Xxxxx
		Title:	Member
	By:	/s/ Xxxx X. Xxxxxx
		Name:	Xxxx X. Xxxxxx
		Title:	Member