The address of the principal place of business for each of the Reporting Persons is: c/o Frazier Life Sciences Management, L.P. 1001 Page Mill Rd, Building 4, Suite B Palo Alto, CA 94304

The information contained in row 4 of each Reporting Person's cover page to this Schedule 13G is incorporated by reference.

The information contained in row 9 of each Reporting Person's cover page to this Schedule 13G (including the footnotes thereto) is incorporated by reference. FLSPF directly holds pre-funded warrants (the "Warrants") to acquire up to 8,141,117 shares of Common Stock. FHMLSP, L.P. is the general partner of FLSPF and the general partner of FHMLSP, L.P. is FHMLSP, L.L.C., which is managed by an investment committee of four that acts by majority vote. Accordingly, no members of such committee are attributed beneficial ownership of the securities directly held by FLSPF, and this Schedule 13G corrects any previous attribution to, and overstatement of beneficial ownership by, such members as reflected in any prior filings. FLSPOF directly holds Warrants to acquire up to 2,401,633 shares of Common Stock. FHMLSP Overage, L.P. is the general partner of FLSPOF and the general partner of FHMLSP Overage, L.P. is FHMLSP Overage, L.L.C., which is managed by an investment committee of four that acts by majority vote. Accordingly, no members of such committee are attributed beneficial ownership of the securities directly held by FLSPOF, and this Schedule 13G corrects any previous attribution to, and overstatement of beneficial ownership by, such members as reflected in any prior filings. FLS X directly holds Warrants to acquire up to 336,042 shares of Common Stock. FHMLS X, L.P. is the general partner of FLS X and FHMLS X, L.L.C. is the general partner of FHMLS X, L.P. Heron and Topper are the members of FHMLS X, L.L.C. and therefore share voting and investment power over the shares of Common Stock held by FLS X. FLS XI directly holds Warrants to acquire up to 894,779 shares of Common Stock. FHMLS XI, L.P. is the general partner of FLS XI and the general partner of FHMLS XI, L.P. is FHMLS XI, L.L.C., which is managed by an investment committee of three that acts by majority vote. Accordingly, no members of such committee are attributed beneficial ownership of the securities directly held by FLS XI, and this Schedule 13G corrects any previous attribution to, and overstatement of beneficial ownership by, such members as reflected in any prior filings. FLS XII directly holds Warrants to acquire up to 1,561,529 shares of Common Stock. FHMLS XII, L.P. is the general partner of FLS XII and the general partner of FHMLS XII, L.P. is FHMLS XII, L.L.C., which is managed by an investment committee of three that acts by majority vote. Accordingly, no members of such committee are attributed beneficial ownership of the securities directly held by FLS IX, and this Schedule 13G corrects any previous attribution to, and overstatement of beneficial ownership by, such members as reflected in any prior filings. The exercise of the Warrants reported in this Schedule 13G is subject to certain beneficial ownership limitations which cap, at 9.99%, the exercisability of Warrants directly held by FLSPF but do not implicate the exercisability of Warrants held by FLSPOF, FLS X, FLS XI or FLS XII because the direct Warrant holders are independently managed and not acting together, provided that, if they were determined to be acting together as a "group," all of the Warrant holders would be limited in their ability to exercise Warrants, to the extent that, upon giving effect to such exercise, the aggregate number of shares of Common Stock beneficially owned by the holder of such Warrant (together with its affiliates or any other persons acting as a group together with such holder) would exceed 9.99% of the number of shares of Common Stock outstanding immediately after giving effect to such exercise. Except as specifically stated herein, the filing of this Schedule 13G shall not be construed as an admission that any Reporting Person is, for the purposes of Section 13(d) and/or Section 13(g) of the Act or otherwise, the beneficial owner of any securities covered by this Schedule 13G or a member of a "group" with any other person.

The information contained in row 11 of each Reporting Person's cover page to this Schedule 13G (including the footnotes thereto) is incorporated by reference.

The information contained in row 5 of each Reporting Person's cover page to this Schedule 13G (including the footnotes thereto) is incorporated by reference.

The information contained in row 6 of each Reporting Person's cover page to this Schedule 13G (including the footnotes thereto) is incorporated by reference.

The information contained in row 7 of each Reporting Person's cover page to this Schedule 13G (including the footnotes thereto) is incorporated by reference.

The information contained in row 8 of each Reporting Person's cover page to this Schedule 13G (including the footnotes thereto) is incorporated by reference.