CUSIP No.  23257Y859  SCHEDULE 13G Page 1 of 1 Pages

EXHIBIT A

JOINT FILING AGREEMENT

The undersigned hereby agree that the Statement on this Schedule 13G dated December 8, 2016 (the “Schedule 13G”), with respect to the Common Stock of Sunovion CNS Development Canada ULC (successor by amalgamation to Cynapsus Therapeutics 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 December 8, 2016.

OrbiMed Capital GP V LLC By: OrbiMed Advisors LLC, its Managing Member
By:	/s/ Samuel D. Isaly
	Name:	Samuel D. Isaly
	Title:	Managing Member
OrbiMed Advisors LLC
By:	/s/ Samuel D. Isaly
	Name:	Samuel D. Isaly
	Title:	Managing Member
Samuel D. Isaly
	/s/ Samuel D. Isaly
	Name:	Samuel D. Isaly