Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F2	Aug 1, 2017	C	2,538,641	—	A	2,538,641	I	See Footnote
Common Stock^F1,F2	Aug 1, 2017	C	211,934	—	A	2,750,575	I	See Footnote
Common Stock^F1,F3	Aug 1, 2017	C	563,072	—	A	563,072	I	See Footnote
Common Stock^F1,F3	Aug 1, 2017	C	319,421	—	A	882,493	I	See Footnote

Table II — derivative securities

Security	Conv. / exercise price	Date	Code	Shares	A/D	Exercisable	Expires	Underlying	Underlying shares	D/I
Series A-3 Preferred Stock^F1,F2,F4	—	Aug 1, 2017	C	2,538,641	D	—	—	Common Stock	2,538,641	I
Series A-3 Preferred Stock^F1,F3,F4	—	Aug 1, 2017	C	563,072	D	—	—	Common Stock	563,072	I
Series B Preferred Stock^F1,F2,F4	—	Aug 1, 2017	C	211,934	D	—	—	Common Stock	211,934	I
Series B Preferred Stock^F1,F3,F4	—	Aug 1, 2017	C	319,421	D	—	—	Common Stock	319,421	I

Explanation of responses

F1The shares of the Issuer's Preferred Stock automatically converted into shares of the Issuer's Common Stock, for no additional consideration, on a 1:1 basis immediately prior to the consummation of the Issuer's initial public offering.
F2The shares are directly held by ARCH Venture Fund VIII, L.P. ("ARCH VIII"). ARCH Venture Partners VIII, L.P. (the "GPLP"), as the sole general partner of ARCH VIII, may be deemed to beneficially own certain of the shares held by ARCH VIII. ARCH Venture Partners VIII, LLC ("GPLLC"), as the sole general partner of GPLP, may be deemed to beneficially own the shares held by ARCH VIII. Keith Crandell and Clinton Bybee are managing directors of GPLLC, and as such may be deemed to beneficially own the shares held by ARCH VIII. Each Reporting Person disclaims beneficial ownership of such shares except to the extent of any pecuniary interest therein.
F3The shares are directly held by ARCH Venture Fund VIII Overage, L.P. ("ARCH Overage"). GPLLC, as the sole general partner of ARCH Overage, may be deemed to beneficially own the shares held by ARCH Overage. Keith Crandell and Clinton Bybee are managing directors of GPLLC, and as such may be deemed to beneficially own the shares held by ARCH Overage. Each Reporting Person disclaims beneficial ownership of such shares except to the extent of any pecuniary interest therein.
F4The expiration date is not relevant to the conversion of these securities.