Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F4,F1	May 8, 2018	C	8,148,778	—	A	9,365,231	I	By Atlas Venture Fund VI, L.P.
Common Stock^F4,F2	May 8, 2018	C	249,193	—	A	286,392	I	By Atlas Venture Entrepreneurs' Fund VI, L.P.
Common Stock^F4,F3	May 8, 2018	C	149,207	—	A	171,480	I	By Atlas Venture Fund VI GmbH & Co. KG

Table II — derivative securities

Security	Conv. / exercise price	Date	Code	Shares	A/D	Exercisable	Expires	Underlying	Underlying shares	D/I
Series B Convertible Preferred Stock^F4,F1	—	May 8, 2018	C	7,398,761	D	—	—	Common Stock	3,699,380	I
Series B Convertible Preferred Stock^F4,F2	—	May 8, 2018	C	226,258	D	—	—	Common Stock	113,129	I
Series B Convertible Preferred Stock^F4,F3	—	May 8, 2018	C	135,475	D	—	—	Common Stock	67,737	I
Series C Convertible Preferred Stock^F4,F1	—	May 8, 2018	C	4,544,751	D	—	—	Common Stock	2,272,375	I
Series C Convertible Preferred Stock^F4,F2	—	May 8, 2018	C	138,981	D	—	—	Common Stock	69,490	I
Series C Convertible Preferred Stock^F4,F3	—	May 8, 2018	C	83,217	D	—	—	Common Stock	41,608	I
Series D Convertible Preferred Stock^F4,F1	—	May 8, 2018	C	1,263,264	D	—	—	Common Stock	631,632	I
Series D Convertible Preferred Stock^F4,F2	—	May 8, 2018	C	38,631	D	—	—	Common Stock	19,315	I
Series D Convertible Preferred Stock^F4,F3	—	May 8, 2018	C	23,131	D	—	—	Common Stock	11,565	I
Series E Convertible Preferred Stock^F4,F1	—	May 8, 2018	C	3,090,783	D	—	—	Common Stock	1,545,391	I
Series E Convertible Preferred Stock^F4,F2	—	May 8, 2018	C	94,518	D	—	—	Common Stock	47,259	I
Series E Convertible Preferred Stock^F4,F3	—	May 8, 2018	C	56,594	D	—	—	Common Stock	28,297	I

Explanation of responses

F1The shares are held directly by Atlas Venture Fund VI, L.P. ("AVF VI"). Atlas Venture Associates VI, L.P. ("AVA VI LP") is the sole general partner of AVF VI. Atlas Venture Associates VI, Inc. ("AVA VI Inc.") is the sole general partner of AVA VI LP. Each of AVA VI LP and AVA VI Inc. disclaims Section 16 beneficial ownership of all shares except to the extent of its pecuniary interest, if any, therein. This report shall not be deemed to be an admission that the reporting persons are the beneficial owners of such securities for purposes of Section 16 or for any other purpose.
F2The shares are held directly by Atlas Venture Entrepreneurs' Fund VI, L.P. ("AVEF VI"). AVA VI LP is the sole general partner of AVEF VI. AVA VI Inc. is the sole general partner of AVA VI LP. Each of AVA VI LP and AVA VI Inc. disclaims Section 16 beneficial ownership of all shares except to the extent of its pecuniary interest, if any, therein. This report shall not be deemed to be an admission that the reporting persons are the beneficial owners of such securities for purposes of Section 16 or for any other purpose.
F3The shares are held directly by Atlas Venture Fund VI GmbH & Co. KG ("AVFG VI"). AVA VI LP is the managing partner of AVFG VI. AVA VI Inc. is the sole general partner of AVA VI LP. Each of AVA VI LP and AVA VI Inc. disclaims Section 16 beneficial ownership of all shares except to the extent of its pecuniary interest, if any, therein. This report shall not be deemed to be an admission that the reporting persons are the beneficial owners of such securities for purposes of Section 16 or for any other purpose.
F4Each share of preferred stock automatically converted into Common Stock on a 1-for-2 basis upon the closing of the Issuer's initial public offering. The shares have no expiration date.