Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F4,F5	Mar 4, 2019	C	665,908	—	A	665,908	I	See Footnote
Common Stock^F6,F1	Mar 4, 2019	C	173,586	—	A	216,451	I	See Footnote
Common Stock^F6,F5	Mar 4, 2019	C	281,203	—	A	947,111	I	See Footnote
Common Stock^F1	holding	—	—		—	42,865	I	See Footnote
Common Stock^F2	holding	—	—		—	42,865	I	See Footnote
Common Stock^F3	holding	—	—		—	1,649,999	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 Preferred Stock^F4,F5	—	Mar 4, 2019	C	1,331,816	D	—	—	Common Stock	665,908	I
Series A-1 Preferred Stock^F6,F1	—	Mar 4, 2019	C	347,173	D	—	—	Common Stock	173,586	I
Series A-1 Preferred Stock^F6,F5	—	Mar 4, 2019	C	562,407	D	—	—	Common Stock	281,203	I

Explanation of responses

F1Shares held by Flagship Ventures Fund 2007, L.P. ("Flagship 2007"). Flagship Ventures 2007 General Partner LLC ("Flagship 2007 GP") is the general partner of Flagship 2007. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship 2007 LLC. While Mr. Kania is retired from Flagship Pioneering, Inc., he continue to serve as a manager of Flagship 2007 GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship 2007. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.
F2Shares held by Flagship VentureLabs IV, LLC ("VentureLabs IV"). Flagship Ventures Fund IV, L.P. ("Flagship Fund IV") is a member of VentureLabs IV and also serves as its manager. Flagship Ventures Fund IV General Partner LLC ("Flagship Fund IV GP") is the general partner of Flagship Fund IV. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship Fund IV GP. While Mr. Kania is retired from Flagship Pioneering, Inc., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by VentureLabs IV. Each of the filing persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein
F3Shares held by Cadena LLC ("Cadena"). Noubar B. Afeyan, Ph.D. is the sole manager of Cadena, and may be deemed to possess sole voting and investment power with respect to all shares held by Cadena. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.
F4Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.001 ("Common Stock"), on a one-for-two basis upon the closing of the Issuer's initial public offering.
F5Shares held by Flagship Ventures Fund IV, L.P. Flagship Fund IV GP is the general partner of Flagship Fund IV. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship Fund IV GP. While Mr. Kania is retired from Flagship Pioneering, Inc., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV. Each of the filing persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.
F6Each share of Series A-1 Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-two basis upon the closing of the Issuer's initial public offering.

Remarks

Due to limitations of the electronic filing system, each of Flagship Ventures Fund V General Partner LLC, Flagship Ventures Fund V, L.P., Flagship VentureLabs V LLC, Flagship VentureLabs V Manager LLC, Flagship Pioneering, Inc., Nutritional Health Disruptive Innovation Fund, L.P., Nutritional Health Side Fund, L.P., Flagship Ventures Opportunities Fund I, L.P., Flagship Ventures Opportunities Fund I General Partner LLC and Noubar B. Afeyan, Ph.D. are filing a separate Form 4 with respect to securities of the Issuer.