Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F2,F3,F4	May 12, 2015	C	1,674,825	—	A	1,674,825	I	By Polaris Venture Partners V, L.P.
Common Stock^F1,F2,F5	May 12, 2015	C	32,642	—	A	32,642	I	By Polaris Venture Partners Entrepreneurs' Fund V, L.P.
Common Stock^F1,F2,F6	May 12, 2015	C	11,472	—	A	11,472	I	By Polaris Venture Partners Founders' Fund V, L.P.
Common Stock^F1,F2,F7	May 12, 2015	C	16,748	—	A	16,748	I	Polaris Venture Partners Special Founders' Fund V, L.P.
Common Stock^F8,F9,F3,F4	May 12, 2015	C	89,069	—	A	1,763,894	I	By Polaris Venture Partners V, L.P.
Common Stock^F8,F9,F5	May 12, 2015	C	1,736	—	A	34,378	I	By Polaris Venture Partners Entrepreneurs' Fund V, L.P.
Common Stock^F8,F9,F6	May 12, 2015	C	610	—	A	12,082	I	By Polaris Venture Partners Founders' Fund V, L.P.
Common Stock^F8,F9,F7	May 12, 2015	C	890	—	A	17,638	I	Polaris Venture Partners Special Founders' Fund V, L.P.

Table II — derivative securities

Security	Conv. / exercise price	Date	Code	Shares	A/D	Exercisable	Expires	Underlying	Underlying shares	D/I
Series B Redeemable Convertible Preferred Stock^F3,F4,F1,F2	—	May 12, 2015	C	3,473,763	D	—	—	Common Stock	436,725	I
Series B Redeemable Convertible Preferred Stock^F5,F1,F2	—	May 12, 2015	C	67,704	D	—	—	Common Stock	8,512	I
Series B Redeemable Convertible Preferred Stock^F6,F1,F2	—	May 12, 2015	C	23,796	D	—	—	Common Stock	2,992	I
Series B Redeemable Convertible Preferred Stock^F7,F1,F2	—	May 12, 2015	C	34,737	D	—	—	Common Stock	4,367	I
Series B-2 Redeemable Convertible Preferred Stock^F3,F4,F1,F2	—	May 12, 2015	C	4,168,683	D	—	—	Common Stock	524,090	I
Series B-2 Redeemable Convertible Preferred Stock^F5,F1,F2	—	May 12, 2015	C	81,248	D	—	—	Common Stock	10,214	I
Series B-2 Redeemable Convertible Preferred Stock^F6,F1,F2	—	May 12, 2015	C	28,556	D	—	—	Common Stock	3,590	I
Series B-2 Redeemable Convertible Preferred Stock^F7,F1,F2	—	May 12, 2015	C	41,686	D	—	—	Common Stock	5,241	I
Series C Redeemable Convertible Preferred Stock^F3,F4,F1,F2	—	May 12, 2015	C	4,208,756	D	—	—	Common Stock	529,128	I
Series C Redeemable Convertible Preferred Stock^F5,F1,F2	—	May 12, 2015	C	82,029	D	—	—	Common Stock	10,313	I
Series C Redeemable Convertible Preferred Stock^F6,F1,F2	—	May 12, 2015	C	28,831	D	—	—	Common Stock	3,624	I
Series C Redeemable Convertible Preferred Stock^F7,F1,F2	—	May 12, 2015	C	42,087	D	—	—	Common Stock	5,291	I
Series D Redeemable Convertible Preferred Stock^F3,F4,F1,F2	—	May 12, 2015	C	1,470,577	D	—	—	Common Stock	184,882	I
Series D Redeemable Convertible Preferred Stock^F5,F1,F2	—	May 12, 2015	C	28,661	D	—	—	Common Stock	3,603	I
Series D Redeemable Convertible Preferred Stock^F6,F1,F2	—	May 12, 2015	C	10,074	D	—	—	Common Stock	1,266	I
Series D Redeemable Convertible Preferred Stock^F7,F1,F2	—	May 12, 2015	C	14,706	D	—	—	Common Stock	1,849	I
Series E Redeemable Convertible Preferred Stock^F3,F4,F8,F9	—	May 12, 2015	C	862,318	D	—	—	Common Stock	89,069	I
Series E Redeemable Convertible Preferred Stock^F5,F8,F9	—	May 12, 2015	C	16,806	D	—	—	Common Stock	1,736	I
Series E Redeemable Convertible Preferred Stock^F6,F8,F9	—	May 12, 2015	C	5,906	D	—	—	Common Stock	610	I
Series E Redeemable Convertible Preferred Stock^F7,F8,F9	—	May 12, 2015	C	8,623	D	—	—	Common Stock	890	I

Explanation of responses

F1The aggregate number of shares of Issuer's Preferred Stock held by the Reporting Person converted into Common Stock immediately prior to the closing of the Issuer's initial public offering and has no expiration date. These shares converted into Common Stock on a 1-for-7.95413 basis.
F2Reflects a 1-for-7.95413 stock conversion of the Issuer's Preferred Stock into Common Stock which became effective immediately prior to the closing of the Issuer's initial public offering.
F3These shares are owned directly by Polaris Venture Partners V, L.P. ("Polaris V"), whose sole general partner is Polaris Venture Management Co. V, LLC ("Polaris Management"). Each of Jonathan A. Flint ("Flint") and Terrance G. McGuire ("McGuire") are the managing members of Polaris Management. Amir Nashat ("Nashat"), who is a member of the Issuer's Board of Directors, is a member of Polaris Management. Each of Flint, McGuire and Nashat, in their respective capacities with regard to Polaris Management, may be deemed to have shared voting and dispositive power over the shares held by each of Polaris V, Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("Polaris Entrepreneurs' V"), Polaris Venture Partners Founders' Fund V, L.P. ("Polaris Founders' V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("Polaris Special Founders' V", and together with Polaris V, Polaris Entrepreneurs' V and Polaris Founders' V, the "Polaris V Funds").
F4(Continued from Footnote 3) Each of Flint, McGuire, Nashat and Polaris Management disclaims beneficial ownership of these securities and this report shall not be deemed to be an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or any other purpose, except to the extent of their pecuniary interest therein.
F5These shares are owned directly by Polaris Entrepreneurs' V, whose sole general partner is Polaris Management. Each of Flint and McGuire are the managing members of Polaris Management. Nashat, who is a member of the Issuer's Board of Directors, is a member of Polaris Management. Each of Flint, McGuire and Nashat, in their respective capacities with regard to Polaris Management, may be deemed to have shared voting and dispositive power over the shares held by each of the Polaris V Funds. Each of Flint, McGuire, Nashat and Polaris Management disclaims beneficial ownership of these securities and this report shall not be deemed to be an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or any other purpose, except to the extent of their pecuniary interest therein.
F6These shares are owned directly by Polaris Founders' V, whose sole general partner is Polaris Management. Each of Flint and McGuire are the managing members of Polaris Management. Nashat, who is a member of the Issuer's Board of Directors, is a member of Polaris Management. Each of Flint, McGuire and Nashat, in their respective capacities with regard to Polaris Management, may be deemed to have shared voting and dispositive power over the shares held by each of the Polaris V Funds. Each of Flint, McGuire, Nashat and Polaris Management disclaims beneficial ownership of these securities and this report shall not be deemed to be an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or any other purpose, except to the extent of their pecuniary interest therein.
F7These shares are owned directly by Polaris Special Founders' V, whose sole general partner is Polaris Management. Each of Flint and McGuire are the managing members of Polaris Management. Nashat, who is a member of the Issuer's Board of Directors, is a member of Polaris Management. Each of Flint, McGuire and Nashat, in their respective capacities with regard to Polaris Management, may be deemed to have shared voting and dispositive power over the shares held by each of the Polaris V Funds. Each of Flint, McGuire, Nashat and Polaris Management disclaims beneficial ownership of these securities and this report shall not be deemed to be an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or any other purpose, except to the extent of their pecuniary interest therein.
F8The aggregate number of shares of Issuer's Preferred Stock held by the Reporting Person converted into Common Stock immediately prior to the closing of the Issuer's initial public offering and has no expiration date. These shares converted into Common Stock on a 1-for-9.6814 basis.
F9Reflects a 1-for 9.6814 stock conversion of the Issuer's Preferred Stock into Common Stock which became effective immediately prior to the closing of the Issuer's initial public offering.