Chen Bihua bought BLSM

Footnotes

Represents (i) 1,228,315 shares issued upon conversion of shares of Series A Preferred Stock beneficially owned by Fund III (defined below), and (ii) 371,678 shares issued upon conversion of shares of Series A Preferred Stock beneficially owned by Master Fund (defined below).; Each share of Series A Preferred Stock and Series B Preferred Stock (together, the "Preferred Stock") automatically converted into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. The Preferred Stock had no expiration date.; Cormorant Asset Management, LP ("Cormorant") serves as the investment manager of Cormorant Global Healthcare Master Fund, LP (the "Master Fund"), Cormorant Private Healthcare Fund III, LP ("Fund III"), Cormorant Private Healthcare Fund V, LP ("Fund V") and Cormorant Private Healthcare Fund VI, LP ("Fund VI"). Cormorant Global Healthcare GP, LLC ("GP LLC"), Cormorant Private Healthcare GP III, LLC ("GP III"), Cormorant Private Healthcare GP V, LLC ("GP V") and Cormorant Private Healthcare GP VI, LLC ("GP VI") serve as General Partner of the Master Fund, Fund III, Fund V and Fund VI, respectively.; Bihua Chen serves as manager of Cormorant, GP LLC, GP III, GP V and GP VI. Each of the Reporting Persons disclaims beneficial ownership of the shares reported herein except to the extent of its or her pecuniary interest therein, and the filing of this Form 4 shall not be construed as an admission that any of the Reporting Persons is the beneficial owner of any such shares for purposes of Section 16(a) of the Securities Exchange Act of 1934 or for any other purpose.