The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

NAME OF REPORTING PERSONS

Polaris Venture Partners VI, L.P.

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☐  (b) ☒

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

SHARES

BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

2,406,309 (1)

SHARED VOTING POWER

0

SOLE DISPOSITIVE POWER

2,406,309 (1)

SHARED DISPOSITIVE POWER

0

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,406,309 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

3.3% (2)

TYPE OF REPORTING PERSON

PN

2,123,347 of such shares are held of record by PVP VI (as defined in Item 2(a) of the Original Schedule 13G) and 282,962 of such shares are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment (as defined below). PVM VI (as defined in Item 2(a) of the Original Schedule 13G), the general partner of PVP VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer’s board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 72,426,220 shares of the Issuer’s Common Stock, calculated as follows (i) 72,143,258 shares of the Issuer’s Common Stock outstanding as of November 2, 2023, as reported by the Issuer in its Form 10-Q for the quarter ended September 30, 2023, filed with the US Securities and Exchange Commission (the “Commission”) on November 7, 2023 (the “Form 10-Q”) plus (ii) 282,962 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment.

NAME OF REPORTING PERSONS

Polaris Venture Partners Founders’ Fund VI, L.P.

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☐  (b) ☒

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

SHARES

BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

140,616 (1)

SHARED VOTING POWER

0

SOLE DISPOSITIVE POWER

140,616 (1)

SHARED DISPOSITIVE POWER

0

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

140,616 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

0.2% (2)

TYPE OF REPORTING PERSON

PN

124,080 of such shares are held of record by PVPFF VI (as defined in Item 2(a) of the Original Schedule 13G) and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment. PVM VI, the general partner of PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer’s board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 72,159,794 shares of the Issuer’s Common Stock, calculated as follows (i) 72,143,258 shares of the Issuer’s Common Stock outstanding as of November 2, 2023, as reported by the Issuer in the Form 10-Q plus 16,536 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment.

NAME OF REPORTING PERSONS

Polaris Venture Management Co VI, L.L.C.

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☐  (b) ☒

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

SHARES

BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

2,546,925 (1)

SHARED VOTING POWER

0

SOLE DISPOSITIVE POWER

2,546,925 (1)

SHARED DISPOSITIVE POWER

0

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,546,925 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

3.5% (2)

TYPE OF REPORTING PERSON

OO

2,123,347 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 124,080 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer’s board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 72,442,756 shares of the Issuer’s Common Stock, calculated as follows (i) 72,143,258 shares of the Issuer’s Common Stock outstanding as of November 2, 2023, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment.

NAME OF REPORTING PERSONS

David Barrett

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☐  (b) ☒

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

United States

NUMBER OF

SHARES

BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

0

SHARED VOTING POWER

2,546,925 (1)

SOLE DISPOSITIVE POWER

0

SHARED DISPOSITIVE POWER

2,546,925 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,546,925 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

3.5% (2)

TYPE OF REPORTING PERSON

IN

2,123,347 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 124,080 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer’s board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 72,442,756 shares of the Issuer’s Common Stock, calculated as follows (i) 72,143,258 shares of the Issuer’s Common Stock outstanding as of November 2, 2023, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment.

NAME OF REPORTING PERSONS

Brian Chee

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☐  (b) ☒

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

United States

NUMBER OF

SHARES

BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

39,339 (1)

SHARED VOTING POWER

2,546,925 (2)

SOLE DISPOSITIVE POWER

39,339 (1)

SHARED DISPOSITIVE POWER

2,546,925 (2)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,586,264 (1) (2)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

3.6% (3)

TYPE OF REPORTING PERSON

IN

All of such shares are held by Brian Chee directly.

2,123,347 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 124,080 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer’s board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 72,442,756 shares of the Issuer’s Common Stock, calculated as follows (i) 72,143,258 shares of the Issuer’s Common Stock outstanding as of November 2, 2023, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment.

NAME OF REPORTING PERSONS

Jonathan A. Flint

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☐  (b) ☒

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

United States

NUMBER OF

SHARES

BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

0

SHARED VOTING POWER

2,546,925 (1)

SOLE DISPOSITIVE POWER

0

SHARED DISPOSITIVE POWER

2,546,925 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,546,925 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

3.5% (2)

TYPE OF REPORTING PERSON

IN

2,123,347 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 124,080 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer’s board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 72,442,756 shares of the Issuer’s Common Stock, calculated as follows (i) 72,143,258 shares of the Issuer’s Common Stock outstanding as of November 2, 2023, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment.

NAME OF REPORTING PERSONS

Terrance G. McGuire

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☐  (b) ☒

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

United States

NUMBER OF

SHARES

BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

39,123 (1)

SHARED VOTING POWER

2,546,925 (2)

SOLE DISPOSITIVE POWER

39,123 (1)

SHARED DISPOSITIVE POWER

2,546,925 (2)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,586,048 (1) (2)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

3.6% (3)

TYPE OF REPORTING PERSON

IN

12,858 of such shares are held by Terrance G. McGuire directly and 26,265 of such shares are held by the McGuire Family 2008 GST Non-Exempt Irrevocable Trust.

2,123,347 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 124,080 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer’s board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 72,442,756 shares of the Issuer’s Common Stock, calculated as follows (i) 72,143,258 shares of the Issuer’s Common Stock outstanding as of November 2, 2023, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment.

NAME OF REPORTING PERSONS

Amir Nashat

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☐  (b) ☒

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

United States

NUMBER OF

SHARES

BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

104,780 (1)

SHARED VOTING POWER

2,546,925 (2)

SOLE DISPOSITIVE POWER

104,780 (1)

SHARED DISPOSITIVE POWER

2,546,925 (2)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,651,705 (1) (2)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

3.7% (3)

TYPE OF REPORTING PERSON

IN

Consists of (i) 25,506 shares held of record directly by Amir Nashat and (ii) 79,274 shares subject to stock option awards that have been granted to Amir Nashat in his capacity as a director of the Issuer and that are exercisable as of or within 60 days of the filing of this Amendment. Excludes 36,000 shares subject to stock option awards that have been granted to Amir Nashat in his capacity as a director of the Issuer and that are not exercisable as of or within 60 days of the filing of this Amendment.

2,123,347 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 124,080 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer’s board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 72,522,030 shares of the Issuer’s Common Stock, calculated as follows: (i) 72,143,258 shares of the Issuer’s Common Stock outstanding as of November 2, 2023, as reported by the Issuer in the Form 10-Q plus (ii) 79,274 shares of the Issuer’s Common Stock subject to stock option awards that have been granted to Amir Nashat in his capacity as a director of the Issuer and that are exercisable as of or within 60 days of the filing of this Amendment plus (iii) 282,962 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iv) 16,536 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment.

NAME OF REPORTING PERSONS

Bryce Youngren

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a)  ☐  (b) ☒

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

United States

NUMBER OF

SHARES

BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

27,299 (1)

SHARED VOTING POWER

2,546,925 (2)

SOLE DISPOSITIVE POWER

27,299 (1)

SHARED DISPOSITIVE POWER

2,546,925 (2)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,574,224 (1) (2)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

3.6% (3)

TYPE OF REPORTING PERSON

IN

All of such shares are held by Bryce Youngren directly.

2,123,347 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 124,080 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer’s board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

Based on 72,442,756 shares of the Issuer’s Common Stock, calculated as follows (i) 72,143,258 shares of the Issuer’s Common Stock outstanding as of November 2, 2023, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer’s Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment.

Row 9 of cover page for each Reporting Person.

Row 11 of cover page for each Reporting Person.

Except to the extent of their pecuniary interest therein, each Reporting Person disclaims beneficial ownership of such shares of Common Stock, except for the shares, if any, such Reporting Person holds of record.