Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F2,F3	Feb 19, 2019	C	2,825,396	—	A	3,021,298	I	See Footnote
Common Stock^F1,F2,F4	Feb 19, 2019	C	322,901	—	A	3,344,199	I	See Footnote
Common Stock^F2,F5	Feb 19, 2019	P	706,666	$15.00	A	4,050,865	I	See Footnote

Table II — derivative securities

Security	Conv. / exercise price	Date	Code	Shares	A/D	Exercisable	Expires	Underlying	Underlying shares	Owned after	D/I
Series A Preferred Stock^F6,F1	—	Feb 19, 2019	C	17,500,000	D	—	—	Common Stock	2,825,396	0	I
Series B Preferred Stock^F6,F1	—	Feb 19, 2019	C	2,000,000	D	—	—	Common Stock	322,901	0	I

Explanation of responses

F1All shares of Series A Preferred Stock and Series B Preferred Stock automatically converted into the number of shares of the Issuer's common stock on a 6.1938:1 basis, for no additional consideration, immediately prior to the closing of the Issuer's initial public offering and had no expiration date.
F2The Reporting Persons disclaim beneficial ownership of the securities except to the extent of their respective pecuniary interests therein.
F3The shares are held as follows: 2,195,681 by MPM BioVentures 2014, L.P. ("BV 2014"), 146,447 by MPM BioVentures 2014(B), L.P. ("BV 2014(B)"), 79,644 by MPM Asset Management Investors BV2014 LLC ("AM BV2014"), 195,902 by MPM Asset Management LLC ("AM LLC"), 351,155 by MPM SunStates Fund, L.P. ("MPM SunStates") and 52,469 by MPM Asset Management Investors Sunstates Fund LLC ("AM SunStates"). MPM BioVentures 2014 GP LLC and MPM BioVentures 2014 LLC ("BV LLC") are the direct and indirect general partners of BV 2014 and BV 2014(B). MPM SunStates Fund GP LLC and MPM SunStates GP Managing Member LLC ("SunStates GP") are the direct and indirect general partners of MPM SunStates. Luke Evnin, Ansbert Gadicke and Todd Foley are the managing directors of BV LLC, Ansbert Gadicke is a member of SunStates GP and Luke Evnin and Anbsert Gadicke are the members of AM LLC.
F4The shares are held as follows: 2,451,844 by BV 2014, 163,532 by BV 2014(B), 88,935 by AM BV2014, 195,902 by AM LLC, 386,270 by MPM SunStates and 57,716 by AM SunStates.
F5The shares are held as follows: 3,056,272 by BV 2014, 203,846 by BV 2014(B), 110,859 by AM BV2014, 195,902 by AM LLC, 421,070 by MPM SunStates and 62,916 by AM SunStates.
F6No securities held by the Reporting Persons.

Remarks

See Form 4 for MPM SunStates Fund, L.P for additional members of this joint filing.