Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F2	May 23, 2016	S	484,903	$0.01	D	2,049,378	I	By ARCH Venture Fund VII, L.P.
Common Stock^F1,F2	May 23, 2016	S	195,156	$0.01	D	1,854,222	I	By ARCH Venture Fund VII, L.P.
Common Stock^F2,F3	May 23, 2016	P	1,000,000	$5.00	A	2,854,222	I	By ARCH Venture Fund VII, L.P.
Common Stock	holding	—	—		—	10,048	D

Table II — derivative securities

Security	Conv. / exercise price	Date	Code	Shares	A/D	Exercisable	Expires	Underlying	Underlying shares	Owned after	D/I
Employee Stock Option(right to buy)^F3	$1.81	May 23, 2016	A	9,385	A	—	Feb 8, 2026	Common Stock	9,385	9,385	D

Explanation of responses

F1Common stock held of record by ARCH Venture Fund VII, L.P. ("ARCH VII"). The sole general partner of ARCH VII is ARCH Venture Partners VII, L.P. ("ARCH Partners VII"), which may be deemed to have shared voting and investment power over the shares held by ARCH VII. The sole general partner of ARCH Partners VII is ARCH Venture Partners VII, LLC ("ARCH VII LLC"), which may be deemed to have shared voting and investment power over the shares held by ARCH VII. ARCH Partners VII and ARCH VII LLC disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein.
F2The managing directors of ARCH VII LLC are Keith Crandell, Clinton Bybee and Robert Nelsen and they may be deemed to have shared voting and investment power over the shares held by ARCH VII. Dr. Steve Gillis owns an interest in ARCH Partners VII, but does not have dispositive or voting power. Messrs. Crandell, Bybee and Nelsen and Dr. Gillis disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein.
F3On February 8, 2016, the reporting person was granted an option to purchase shares of common stock. The option vests in 48 equal monthly installments commencing on June 23, 2016, which is one month from the date of the consummation of the Issuer's initial public offering, and subject to the reporting person's continued service to the Issuer.