| CUSIP No. 74366E102 | 13G | Page 9 of 9 Pages |
Exhibit 99.1
JOINT FILING AGREEMENT
We, the undersigned, hereby express our agreement that the attached Schedule 13G is, and any further amendments thereto signed by each of the undersigned shall be, filed on behalf of us pursuant to and in accordance with the provisions of Rule13d-1(k) under the Securities Exchange Act of 1934. This agreement may be terminated with respect to the obligations to jointly file future amendments to such statement on Schedule 13G as to any of the undersigned upon such person giving written notice thereof to each of the other persons signatory hereto, at the principal office thereof.
Dated: February 13, 2018
| PHARMSTANDARD INTERNATIONAL S.A. | ||
| By: | /s/ Erik Martinovskis | |
| Name: Erik Martinovskis | ||
| Title: Director | ||
| JOINT STOCK COMPANY PHARMSTANDARD | ||
| By: | /s/ Fedlyuk Viktor P. | |
| Name: Fedlyuk Viktor P. | ||
| Title: Deputy General Director for Legal Affairs | ||