Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F3,F4	Jul 25, 2016	C	535,996	—	A	535,996	I	Through Deerfield Private Design Fund III, L.P.
Common Stock^F1,F3,F4	Jul 25, 2016	C	267,998	—	A	267,998	I	Through Deerfield Special Situations Fund, L.P.
Common Stock^F2,F3,F4	Jul 25, 2016	C	99,830	—	A	635,826	I	Through Deerfield Private Design Fund III, L.P.
Common Stock^F2,F3,F4	Jul 25, 2016	C	99,830	—	A	367,828	I	Through Deerfield Special Situations Fund, L.P.
Common Stock^F3,F4	Jul 25, 2016	P	253,404	$15.00	A	889,230	I	Through Deerfield Private Design Fund III, L.P.
Common Stock^F3,F4	Jul 25, 2016	P	146,596	$15.00	A	514,424	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	D/I
Series B Convertible Preferred Stock^F1,F3,F4	—	Jul 25, 2016	C	535,996	D	—	—	Common Stock	535,996	I
Series B Convertible Preferred Stock^F1,F3,F4	—	Jul 25, 2016	C	267,998	D	—	—	Common Stock	267,998	I
Series C Convertible Preferred Stock^F2,F3,F4	—	Jul 25, 2016	C	99,830	D	—	—	Common Stock	99,830	I
Series C Convertible Preferred Stock^F2,F3,F4	—	Jul 25, 2016	C	99,830	D	—	—	Common Stock	99,830	I

Explanation of responses

F1Each share of Series B Convertible Preferred Stock automatically converted into 1 share of the Issuer's Common Stock immediately prior to the closing of the Issuer's initial public offering of Common Stock. The amounts in column 5 of Table I are presented as if conversion of the Series B Convertible Preferred Stock accrued immediately prior to the conversion of the Series C Convertible Preferred Stock.
F2Each share of Series C Convertible Preferred Stock automatically converted into 1 share of the Issuer's Common Stock immediately prior to the closing of the Issuer's initial public offering of Common Stock. The amounts in column 5 of Table I are presented as if conversion of the Series B Convertible Preferred Stock accrued immediately prior to the conversion of the Series C Convertible Preferred Stock.
F3This 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"). Deerfield Mgmt, L.P. is the general partner of Deerfield Special Situations Fund, L.P. (collectively 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.
F4In 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 Editas Medicine, Inc. filed with the Securities and Exchange Commission on February 2, 2016 by Deerfield Mgmt III, L.P., Deerfield Management Company, L.P., Deerfield Healthcare Innovations Fund, L.P., Deerfield Mgmt HIF, L.P., Deerfield Private Design Fund III, L.P. and James E. Flynn.