Exhibit A AGREEMENT REGARDING THE JOINT FILING OF SCHEDULE 13D

CUSIP No. 00000X000 Page [•] of [•]

Exhibit A

AGREEMENT REGARDING THE JOINT FILING OF

SCHEDULE 13D

The undersigned, being duly authorized thereunto, hereby execute this agreement as an exhibit to this Schedule 13D to evidence the agreement of the below-named parties, in accordance with the rules promulgated pursuant to the Securities Exchange Act of 1934, to file this Schedule jointly on behalf of each such party.

Dated: December 21, 2018

POLARIS VENTURE PARTNERS V, L.P.
By:		Polaris Venture Management Co. V, L.L.C.
By:		*
		Managing Member
POLARIS VENTURE PARTNERS ENTREPRENEURS’ FUND V, L.P.
By:		Polaris Venture Management Co. V, L.L.C.
By:		*
		Managing Member
POLARIS VENTURE PARTNERS FOUNDERS’ FUND V, L.P.
By: Polaris Venture Management Co. V, L.L.C.
By:		*
		Managing Member
POLARIS VENTURE PARTNERS SPECIAL FOUNDERS’ FUND V, L.P.
By:		Polaris Venture Management Co. V, L.L.C.
By:		*
		Managing Member
POLARIS VENTURE MANAGEMENT CO. V, L.L.C.
By:		*
		Managing Member

XXXXXXXX X. XXXXX
By:		*
Xxxxxxxx X. Xxxxx
XXXXXXXX X. XXXXXXX
By:		*
Xxxxxxxx X. XxXxxxx
XXXX XXXXXX
By:		*
		Xxxx Xxxxxx

*By:		/s/ Xxx Xxxxxxxxx
Name:		Xxx Xxxxxxxxx
		Attorney-in-Fact

[This Exhibit A to Schedule 13D Amendment No. 1 was executed pursuant to Powers of Attorney. Note that copies of the applicable Powers of Attorney are already on file with the appropriate agencies.]