Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F2,F3	May 12, 2015	C	230,764	—	A	230,764	I	Through Deerfield Private Design Fund III, L.P.
Common Stock^F1,F2,F3	May 12, 2015	C	230,764	—	A	230,764	I	Through Deerfield Special Situations Fund, L.P.
Common Stock^F2,F3	May 12, 2015	P	25,000	$14.00	A	255,764	I	Through Deerfield Private Design Fund III, L.P.
Common Stock^F2,F3	May 12, 2015	P	25,000	$14.00	A	255,764	I	Through Deerfield Special Situations Fund, L.P.

Table II — derivative securities

Security	Conv. / exercise price	Date	Code	Shares	A/D	Exercisable	Expires	Underlying	Underlying shares	Owned after	D/I
Series E Preferred Stock^F1,F2,F3	—	May 12, 2015	C	2,234,137	D	—	—	Common Stock	230,764	0	I
Series E Preferred Stock^F1,F2,F3	—	May 12, 2015	C	2,234,137	D	—	—	Common Stock	230,764	0	I

Explanation of responses

F1Shares of Series E Convertible Preferred Stock have no expiration date. Each share of Series E Convertible Preferred Stock automatically converted into .10329 shares of the Issuer's Common Stock upon the closing of the Issuer's initial public offering of Common Stock.
F2This Form 4 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt III, L.P. is the general partner of Deerfield Private Design Fund III, L.P. ("Fund III") and Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. (together with Fund III, the "Funds"). Deerfield Management Company, L.P. is the investment manager of the Funds. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.
F3In accordance with Instruction 4 (b)(iv) to Form 4, the entire amount of the Issuer's securities held by the Funds is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.

Remarks

Jonathan Isler, Attorney-in-Fact: Power of Attorney, which is hereby incorporated by reference to Exhibit 24 to a Form 3 with regard to Avalanche Biotechnologies, Inc. filed with the Securities and Exchange Commission on July 30, 2014 by Deerfield Mgmt III, L.P., Deerfield Mgmt, L.P., Deerfield Management Company, L.P., Deerfield Special Situations Fund, L.P., Deerfield Special Situations International Master Fund, L.P., Deerfield Private Design Fund III, L.P. and James E. Flynn.