TCRX

SEC source: 0000899243-22-020961 · doc4.xml · derivative · entry 1

Harel Ittai · CIK 0001632710 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,146

Underlying: Voting Common Stock · 9,146 shares

Expires 2032-05-31

F1 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) June 1, 2023 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

SEC source: 0000899243-22-019018 · doc4.xml · nonDerivative · entry 2

SOUTHWELL DAVID P · CIK 0001251553 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 171,569

F2 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $3.45 to $3.55, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of securities purchased at each separate price within the ranges set forth in this footnote.

SEC source: 0000899243-22-019018 · doc4.xml · nonDerivative · entry 1

SOUTHWELL DAVID P · CIK 0001251553 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 161,569

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $3.379 to $3.70, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of securities purchased at each separate price within the ranges set forth in this footnote.

SEC source: 0001209191-22-028579 · doc4.xml · nonDerivative · entry 8

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director · 10% owner

667, L.P. · CIK 0001551139 · Director · 10% owner

BAKER FELIX · CIK 0001087940 · Director · 10% owner

BAKER JULIAN · CIK 0001087939 · Director · 10% owner

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director · 10% owner

Baker Brothers Life Sciences LP · CIK 0001363364 · Director · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 2,528,583

F7 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were traded by the Funds in multiple transactions at prices ranging from $1.98 to $1.99, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer, or the Staff, upon request, full information regarding the number of shares traded at each separate price within the range set forth in this footnote.

F2 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to 667 and Baker Brothers Life Sciences, L.P. ("Life Sciences", and togehter with 667, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F3 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

F4 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Brothers Life Sciences Capital L.P. and (ii) Life Sciences, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the Common Stock reported in column 5 of Table I directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to their interest in Life Sciences and Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.

SEC source: 0001209191-22-028579 · doc4.xml · nonDerivative · entry 7

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director · 10% owner

667, L.P. · CIK 0001551139 · Director · 10% owner

BAKER FELIX · CIK 0001087940 · Director · 10% owner

BAKER JULIAN · CIK 0001087939 · Director · 10% owner

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director · 10% owner

Baker Brothers Life Sciences LP · CIK 0001363364 · Director · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 256,209

F7 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were traded by the Funds in multiple transactions at prices ranging from $1.98 to $1.99, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer, or the Staff, upon request, full information regarding the number of shares traded at each separate price within the range set forth in this footnote.

F1 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, L.P. ("667"), Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer") reported in column 5 of Table I directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to their interest in 667 and Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.

F2 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to 667 and Baker Brothers Life Sciences, L.P. ("Life Sciences", and togehter with 667, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F3 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

SEC source: 0001209191-22-028579 · doc4.xml · nonDerivative · entry 6

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director · 10% owner

667, L.P. · CIK 0001551139 · Director · 10% owner

BAKER FELIX · CIK 0001087940 · Director · 10% owner

BAKER JULIAN · CIK 0001087939 · Director · 10% owner

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director · 10% owner

Baker Brothers Life Sciences LP · CIK 0001363364 · Director · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 2,505,600

F6 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were traded by the Funds in multiple transactions at prices ranging from $1.78 to $2.00, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer, or the Staff, upon request, full information regarding the number of shares traded at each separate price within the range set forth in this footnote.

F2 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to 667 and Baker Brothers Life Sciences, L.P. ("Life Sciences", and togehter with 667, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F3 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

F4 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Brothers Life Sciences Capital L.P. and (ii) Life Sciences, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the Common Stock reported in column 5 of Table I directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to their interest in Life Sciences and Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.

SEC source: 0001209191-22-028579 · doc4.xml · nonDerivative · entry 5

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director · 10% owner

667, L.P. · CIK 0001551139 · Director · 10% owner

BAKER FELIX · CIK 0001087940 · Director · 10% owner

BAKER JULIAN · CIK 0001087939 · Director · 10% owner

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director · 10% owner

Baker Brothers Life Sciences LP · CIK 0001363364 · Director · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 253,327

F6 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were traded by the Funds in multiple transactions at prices ranging from $1.78 to $2.00, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer, or the Staff, upon request, full information regarding the number of shares traded at each separate price within the range set forth in this footnote.

F1 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, L.P. ("667"), Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer") reported in column 5 of Table I directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to their interest in 667 and Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.

F2 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to 667 and Baker Brothers Life Sciences, L.P. ("Life Sciences", and togehter with 667, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F3 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

SEC source: 0001209191-22-028579 · doc4.xml · nonDerivative · entry 4

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director · 10% owner

667, L.P. · CIK 0001551139 · Director · 10% owner

BAKER FELIX · CIK 0001087940 · Director · 10% owner

BAKER JULIAN · CIK 0001087939 · Director · 10% owner

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director · 10% owner

Baker Brothers Life Sciences LP · CIK 0001363364 · Director · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 1,747,506

F5 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were traded by the Funds in multiple transactions at prices ranging from $1.90 to $2.00, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission (the "Staff"), upon request, full information regarding the number of shares traded at each separate price within the range set forth in this footnote.

F2 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to 667 and Baker Brothers Life Sciences, L.P. ("Life Sciences", and togehter with 667, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F3 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

F4 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Brothers Life Sciences Capital L.P. and (ii) Life Sciences, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the Common Stock reported in column 5 of Table I directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to their interest in Life Sciences and Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.

SEC source: 0001209191-22-028579 · doc4.xml · nonDerivative · entry 3

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director · 10% owner

667, L.P. · CIK 0001551139 · Director · 10% owner

BAKER FELIX · CIK 0001087940 · Director · 10% owner

BAKER JULIAN · CIK 0001087939 · Director · 10% owner

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director · 10% owner

Baker Brothers Life Sciences LP · CIK 0001363364 · Director · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 158,267

F5 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were traded by the Funds in multiple transactions at prices ranging from $1.90 to $2.00, inclusive. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission (the "Staff"), upon request, full information regarding the number of shares traded at each separate price within the range set forth in this footnote.

F1 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, L.P. ("667"), Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer") reported in column 5 of Table I directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to their interest in 667 and Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.

F2 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to 667 and Baker Brothers Life Sciences, L.P. ("Life Sciences", and togehter with 667, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F3 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

SEC source: 0001209191-22-028579 · doc4.xml · nonDerivative · entry 2

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director · 10% owner

667, L.P. · CIK 0001551139 · Director · 10% owner

BAKER FELIX · CIK 0001087940 · Director · 10% owner

BAKER JULIAN · CIK 0001087939 · Director · 10% owner

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director · 10% owner

Baker Brothers Life Sciences LP · CIK 0001363364 · Director · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 1,645,675

F2 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to 667 and Baker Brothers Life Sciences, L.P. ("Life Sciences", and togehter with 667, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F3 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

F4 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Brothers Life Sciences Capital L.P. and (ii) Life Sciences, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the Common Stock reported in column 5 of Table I directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to their interest in Life Sciences and Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.

SEC source: 0001209191-22-028579 · doc4.xml · nonDerivative · entry 1

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director · 10% owner

667, L.P. · CIK 0001551139 · Director · 10% owner

BAKER FELIX · CIK 0001087940 · Director · 10% owner

BAKER JULIAN · CIK 0001087939 · Director · 10% owner

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director · 10% owner

Baker Brothers Life Sciences LP · CIK 0001363364 · Director · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 145,498

F1 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, L.P. ("667"), Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer") reported in column 5 of Table I directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to their interest in 667 and Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.

F2 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to 667 and Baker Brothers Life Sciences, L.P. ("Life Sciences", and togehter with 667, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F3 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

SEC source: 0000899243-22-012476 · doc4.xml · nonDerivative · entry 1

Silver Brian M. · CIK 0001860597 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 26,885

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $3.375 to $3.48, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of securities purchased at each separate price within the ranges set forth in this footnote (1) to this Form 4.

SEC source: 0000899243-22-002650 · doc4.xml · derivative · entry 1

Silver Brian M. · CIK 0001860597 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 115,000

Underlying: Voting Common Stock · 115,000 shares

Expires 2032-01-17

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following January 18, 2022, with 25% vesting upon completion of 1 year of continuous service to the Issuer and the balance vesting in 36 equal monthly installments thereafter.

SEC source: 0000899243-22-002654 · doc4.xml · derivative · entry 1

Desmarais William · CIK 0001860207 · Chief Business Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 50,000

Underlying: Voting Common Stock · 50,000 shares

Expires 2032-01-17

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following January 18, 2022, with 25% vesting upon completion of 1 year of continuous service to the Issuer and the balance vesting in 36 equal monthly installments thereafter.

SEC source: 0000899243-22-002651 · doc4.xml · derivative · entry 1

MacBeath Gavin · CIK 0001738082 · Chief Scientific Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 140,000

Underlying: Voting Common Stock · 140,000 shares

Expires 2032-01-17

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following January 18, 2022, with 25% vesting upon completion of 1 year of continuous service to the Issuer and the balance vesting in 36 equal monthly installments thereafter.

SEC source: 0000899243-22-002647 · doc4.xml · derivative · entry 1

SOUTHWELL DAVID P · CIK 0001251553 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 275,000

Underlying: Voting Common Stock · 275,000 shares

Expires 2032-01-17

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following January 18, 2022, with 25% vesting upon completion of 1 year of continuous service to the Issuer and the balance vesting in 36 equal monthly installments thereafter.

SEC source: 0000899243-22-002646 · doc4.xml · derivative · entry 1

ZDRAVESKI ZORAN · CIK 0001741285 · Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 85,000

Underlying: Voting Common Stock · 85,000 shares

Expires 2032-01-17

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following January 18, 2022, with 25% vesting upon completion of 1 year of continuous service to the Issuer and the balance vesting in 36 equal monthly installments thereafter.

SEC source: 0000899243-21-049764 · doc4.xml · derivative · entry 2

SOUTHWELL DAVID P · CIK 0001251553 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 21,161

Underlying: Voting Common Stock · 48,670 shares

Expires 2029-02-04

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_date: The shares originally subject to this option vested over 4 years of service following October 9, 2018, with 25% vesting upon completion of 1 year of continuous service to the Issuer and the balance vesting in 36 equal monthly installments thereafter. In addition, all of the shares subject to this option shall vest and become fully exercisable upon a Change of Control (as defined in the option agreement).

SEC source: 0000899243-21-049764 · doc4.xml · nonDerivative · entry 1

SOUTHWELL DAVID P · CIK 0001251553 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 146,569

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

SEC source: 0000899243-21-037802 · doc4.xml · nonDerivative · entry 1

ZDRAVESKI ZORAN · CIK 0001741285 · Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,716

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $7.43 to $7.48, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of securities purchased at each separate price within the ranges set forth in this footnote (1) to this Form 4.

SEC source: 0000899243-21-037149 · doc4.xml · nonDerivative · entry 1

Silver Brian M. · CIK 0001860597 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 11,885

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $6.20 to $6.432, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of securities purchased at each separate price within the ranges set forth in this footnote (1) to this Form 4.

SEC source: 0000899243-21-037147 · doc4.xml · nonDerivative · entry 2

MacBeath Gavin · CIK 0001738082 · Chief Scientific Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 49,767

SEC source: 0000899243-21-037147 · doc4.xml · nonDerivative · entry 1

MacBeath Gavin · CIK 0001738082 · Chief Scientific Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 49,710

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $6.09 to $6.30, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of securities purchased at each separate price within the ranges set forth in this footnote (1) to this Form 4.

SEC source: 0000899243-21-035684 · doc4.xml · nonDerivative · entry 1

Silver Brian M. · CIK 0001860597 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,885

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $8.34 to $8.52, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of securities purchased at each separate price within the ranges set forth in this footnote (1) to this Form 4.

SEC source: 0000899243-21-035442 · doc4.xml · nonDerivative · entry 1

SOUTHWELL DAVID P · CIK 0001251553 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 97,899

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $8.64 to $8.75, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of securities purchased at each separate price within the ranges set forth in this footnote (1) to this Form 4.

SEC source: 0000899243-21-035470 · doc4.xml · derivative · entry 1

ZDRAVESKI ZORAN · CIK 0001741285 · Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 150,000

Underlying: Voting Common Stock · 150,000 shares

Expires 2031-09-06

F1 · derivative.exercise_date: The shares subject to this option will vest with respect to 25% of the shares after 12 months of continuous service to the Issuer following September 7, 2021, and the balance will vest in equal monthly installments over the next 36 months of continuous service to the Issuer.

SEC source: 0000899243-21-034610 · doc4.xml · nonDerivative · entry 1

Desmarais William · CIK 0001860207 · Chief Business Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,500

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $9.01 to $9.09, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of securities purchased at each separate price within the ranges set forth in this footnote (1) to this Form 4.

SEC source: 0001638599-21-000606 · doc4_7293.xml · derivative · entry 6

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director

667, L.P. · CIK 0001551139 · Director

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director

Baker Brothers Life Sciences LP · CIK 0001363364 · Director

BAKER FELIX · CIK 0001087940 · Director

BAKER JULIAN · CIK 0001087939 · Director

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 3,960,811

Underlying: Common Stock · 3,960,811 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F6 · derivative.exercise_price: Series C Convertible Preferred Stock of the Issuer ("Series C Preferred") were convertible at any time by the holder and were automatically convertible on a 1-for-1 basis ("Series C Preferred Conversion Ratio") without payment or further consideration immediately prior to the close of the IPO into either Common Stock or non-voting common stock of the Issuer ("Non-Voting Common Stock"). The Funds elected to automatically convert immediately prior to the close of the IPO into the number of shares of Non-Voting Common Stock shown in Table II. The Series C Preferred had no expiration date.

F7 · derivative.exercise_price: Each share of Non-Voting Common Stock is convertible into one share of Common Stock at any time at the option of the holder without consideration subject to a 4.99% beneficial ownership limitation described below.

F9 · price: Pursuant to Instruction 4(c)(iii), this response has been left blank.

F7 · derivative.exercise_date: Each share of Non-Voting Common Stock is convertible into one share of Common Stock at any time at the option of the holder without consideration subject to a 4.99% beneficial ownership limitation described below.

F8 · derivative.exercise_date: The Non-Voting Common Stock is only convertible to the extent that after giving effect to such conversion the holders thereof together with their affiliates with whom such holders would be required to aggregate beneficial ownership for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act") would beneficially own, for purposes of Section 13(d) of the Exchange Act, no more than 4.99% of the outstanding Common Stock (the "Beneficial Ownership Limitation"). By written notice to the Issuer, the Funds may from time to time increase or decrease the Beneficial Ownership Limitation applicable to that Fund to any other percentage, and any increase will not be effective until the 61st day after notice is delivered to the Issuer. The shares of Non-Voting Common Stock have no expiration date.

F7 · derivative.expiration_date: Each share of Non-Voting Common Stock is convertible into one share of Common Stock at any time at the option of the holder without consideration subject to a 4.99% beneficial ownership limitation described below.

F8 · derivative.expiration_date: The Non-Voting Common Stock is only convertible to the extent that after giving effect to such conversion the holders thereof together with their affiliates with whom such holders would be required to aggregate beneficial ownership for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act") would beneficially own, for purposes of Section 13(d) of the Exchange Act, no more than 4.99% of the outstanding Common Stock (the "Beneficial Ownership Limitation"). By written notice to the Issuer, the Funds may from time to time increase or decrease the Beneficial Ownership Limitation applicable to that Fund to any other percentage, and any increase will not be effective until the 61st day after notice is delivered to the Issuer. The shares of Non-Voting Common Stock have no expiration date.

F4 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to the Funds. In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F5 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

F11 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Brothers Life Sciences Capital L.P. and (ii) Life Sciences, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the securities reported in column 9 of Table II directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to their interest in Life Sciences and Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.

SEC source: 0001638599-21-000606 · doc4_7293.xml · derivative · entry 5

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director

667, L.P. · CIK 0001551139 · Director

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director

Baker Brothers Life Sciences LP · CIK 0001363364 · Director

BAKER FELIX · CIK 0001087940 · Director

BAKER JULIAN · CIK 0001087939 · Director

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Non-Voting Common Stock · 3,960,811 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F6 · derivative.exercise_price: Series C Convertible Preferred Stock of the Issuer ("Series C Preferred") were convertible at any time by the holder and were automatically convertible on a 1-for-1 basis ("Series C Preferred Conversion Ratio") without payment or further consideration immediately prior to the close of the IPO into either Common Stock or non-voting common stock of the Issuer ("Non-Voting Common Stock"). The Funds elected to automatically convert immediately prior to the close of the IPO into the number of shares of Non-Voting Common Stock shown in Table II. The Series C Preferred had no expiration date.

F7 · derivative.exercise_price: Each share of Non-Voting Common Stock is convertible into one share of Common Stock at any time at the option of the holder without consideration subject to a 4.99% beneficial ownership limitation described below.

F9 · price: Pursuant to Instruction 4(c)(iii), this response has been left blank.

F6 · derivative.exercise_date: Series C Convertible Preferred Stock of the Issuer ("Series C Preferred") were convertible at any time by the holder and were automatically convertible on a 1-for-1 basis ("Series C Preferred Conversion Ratio") without payment or further consideration immediately prior to the close of the IPO into either Common Stock or non-voting common stock of the Issuer ("Non-Voting Common Stock"). The Funds elected to automatically convert immediately prior to the close of the IPO into the number of shares of Non-Voting Common Stock shown in Table II. The Series C Preferred had no expiration date.

F6 · derivative.expiration_date: Series C Convertible Preferred Stock of the Issuer ("Series C Preferred") were convertible at any time by the holder and were automatically convertible on a 1-for-1 basis ("Series C Preferred Conversion Ratio") without payment or further consideration immediately prior to the close of the IPO into either Common Stock or non-voting common stock of the Issuer ("Non-Voting Common Stock"). The Funds elected to automatically convert immediately prior to the close of the IPO into the number of shares of Non-Voting Common Stock shown in Table II. The Series C Preferred had no expiration date.

F4 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to the Funds. In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F5 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

F11 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Brothers Life Sciences Capital L.P. and (ii) Life Sciences, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the securities reported in column 9 of Table II directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to their interest in Life Sciences and Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.

SEC source: 0001638599-21-000606 · doc4_7293.xml · derivative · entry 4

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director

667, L.P. · CIK 0001551139 · Director

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director

Baker Brothers Life Sciences LP · CIK 0001363364 · Director

BAKER FELIX · CIK 0001087940 · Director

BAKER JULIAN · CIK 0001087939 · Director

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 315,777

Underlying: Common Stock · 315,777 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F6 · derivative.exercise_price: Series C Convertible Preferred Stock of the Issuer ("Series C Preferred") were convertible at any time by the holder and were automatically convertible on a 1-for-1 basis ("Series C Preferred Conversion Ratio") without payment or further consideration immediately prior to the close of the IPO into either Common Stock or non-voting common stock of the Issuer ("Non-Voting Common Stock"). The Funds elected to automatically convert immediately prior to the close of the IPO into the number of shares of Non-Voting Common Stock shown in Table II. The Series C Preferred had no expiration date.

F7 · derivative.exercise_price: Each share of Non-Voting Common Stock is convertible into one share of Common Stock at any time at the option of the holder without consideration subject to a 4.99% beneficial ownership limitation described below.

F9 · price: Pursuant to Instruction 4(c)(iii), this response has been left blank.

F7 · derivative.exercise_date: Each share of Non-Voting Common Stock is convertible into one share of Common Stock at any time at the option of the holder without consideration subject to a 4.99% beneficial ownership limitation described below.

F8 · derivative.exercise_date: The Non-Voting Common Stock is only convertible to the extent that after giving effect to such conversion the holders thereof together with their affiliates with whom such holders would be required to aggregate beneficial ownership for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act") would beneficially own, for purposes of Section 13(d) of the Exchange Act, no more than 4.99% of the outstanding Common Stock (the "Beneficial Ownership Limitation"). By written notice to the Issuer, the Funds may from time to time increase or decrease the Beneficial Ownership Limitation applicable to that Fund to any other percentage, and any increase will not be effective until the 61st day after notice is delivered to the Issuer. The shares of Non-Voting Common Stock have no expiration date.

F7 · derivative.expiration_date: Each share of Non-Voting Common Stock is convertible into one share of Common Stock at any time at the option of the holder without consideration subject to a 4.99% beneficial ownership limitation described below.

F8 · derivative.expiration_date: The Non-Voting Common Stock is only convertible to the extent that after giving effect to such conversion the holders thereof together with their affiliates with whom such holders would be required to aggregate beneficial ownership for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act") would beneficially own, for purposes of Section 13(d) of the Exchange Act, no more than 4.99% of the outstanding Common Stock (the "Beneficial Ownership Limitation"). By written notice to the Issuer, the Funds may from time to time increase or decrease the Beneficial Ownership Limitation applicable to that Fund to any other percentage, and any increase will not be effective until the 61st day after notice is delivered to the Issuer. The shares of Non-Voting Common Stock have no expiration date.

F4 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to the Funds. In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F5 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

F10 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the securities reported in column 9 of Table II directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to their interest in 667 and Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.

SEC source: 0001638599-21-000606 · doc4_7293.xml · derivative · entry 3

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director

667, L.P. · CIK 0001551139 · Director

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director

Baker Brothers Life Sciences LP · CIK 0001363364 · Director

BAKER FELIX · CIK 0001087940 · Director

BAKER JULIAN · CIK 0001087939 · Director

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Non-Voting Common Stock · 315,777 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F6 · derivative.exercise_price: Series C Convertible Preferred Stock of the Issuer ("Series C Preferred") were convertible at any time by the holder and were automatically convertible on a 1-for-1 basis ("Series C Preferred Conversion Ratio") without payment or further consideration immediately prior to the close of the IPO into either Common Stock or non-voting common stock of the Issuer ("Non-Voting Common Stock"). The Funds elected to automatically convert immediately prior to the close of the IPO into the number of shares of Non-Voting Common Stock shown in Table II. The Series C Preferred had no expiration date.

F7 · derivative.exercise_price: Each share of Non-Voting Common Stock is convertible into one share of Common Stock at any time at the option of the holder without consideration subject to a 4.99% beneficial ownership limitation described below.

F9 · price: Pursuant to Instruction 4(c)(iii), this response has been left blank.

F6 · derivative.exercise_date: Series C Convertible Preferred Stock of the Issuer ("Series C Preferred") were convertible at any time by the holder and were automatically convertible on a 1-for-1 basis ("Series C Preferred Conversion Ratio") without payment or further consideration immediately prior to the close of the IPO into either Common Stock or non-voting common stock of the Issuer ("Non-Voting Common Stock"). The Funds elected to automatically convert immediately prior to the close of the IPO into the number of shares of Non-Voting Common Stock shown in Table II. The Series C Preferred had no expiration date.

F6 · derivative.expiration_date: Series C Convertible Preferred Stock of the Issuer ("Series C Preferred") were convertible at any time by the holder and were automatically convertible on a 1-for-1 basis ("Series C Preferred Conversion Ratio") without payment or further consideration immediately prior to the close of the IPO into either Common Stock or non-voting common stock of the Issuer ("Non-Voting Common Stock"). The Funds elected to automatically convert immediately prior to the close of the IPO into the number of shares of Non-Voting Common Stock shown in Table II. The Series C Preferred had no expiration date.

F4 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to the Funds. In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F5 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

F10 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the securities reported in column 9 of Table II directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to their interest in 667 and Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.

SEC source: 0001638599-21-000606 · doc4_7293.xml · nonDerivative · entry 2

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director

667, L.P. · CIK 0001551139 · Director

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director

Baker Brothers Life Sciences LP · CIK 0001363364 · Director

BAKER FELIX · CIK 0001087940 · Director

BAKER JULIAN · CIK 0001087939 · Director

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 1,320,302

F1 · ownership.nature: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 104,698 and 1,320,302 shares of common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $15.00 per share pursuant to the initial public offering (the "IPO") that closed on July 20, 2021.

F3 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Brothers Life Sciences Capital L.P. and (ii) Life Sciences, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the Common Stock reported in column 5 of Table I directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to their interest in Life Sciences and Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.

F4 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to the Funds. In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F5 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

SEC source: 0001638599-21-000606 · doc4_7293.xml · nonDerivative · entry 1

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director

667, L.P. · CIK 0001551139 · Director

Baker Bros. Advisors (GP) LLC · CIK 0001580575 · Director

Baker Brothers Life Sciences LP · CIK 0001363364 · Director

BAKER FELIX · CIK 0001087940 · Director

BAKER JULIAN · CIK 0001087939 · Director

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 104,698

F1 · ownership.nature: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 104,698 and 1,320,302 shares of common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $15.00 per share pursuant to the initial public offering (the "IPO") that closed on July 20, 2021.

F2 · ownership.nature: After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the Common Stock reported in column 5 of Table I directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to their interest in 667 and Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.

F4 · ownership.nature: Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to the Funds. In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.

F5 · ownership.nature: Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.

SEC source: 0000899243-21-029440 · doc4.xml · derivative · entry 2

BARBERICH TIMOTHY J · CIK 0001120355 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Voting Common Stock · 33,259 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of the Issuer's Series B Preferred Stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F1 · price: Each share of the Issuer's Series B Preferred Stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F1 · derivative.exercise_date: Each share of the Issuer's Series B Preferred Stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F1 · derivative.expiration_date: Each share of the Issuer's Series B Preferred Stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

SEC source: 0000899243-21-029440 · doc4.xml · nonDerivative · entry 1

BARBERICH TIMOTHY J · CIK 0001120355 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 33,259

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of the Issuer's Series B Preferred Stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

SEC source: 0000899243-21-029437 · doc4.xml · nonDerivative · entry 1

Silver Brian M. · CIK 0001860597 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,000

F1 · shares: Represents shares purchased in the Issuer's initial public offering.

SEC source: 0000899243-21-029479 · doc4.xml · derivative · entry 7

Westphal Christoph H · CIK 0001291961 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Voting Common Stock · 171,063 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F2 · price: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F2 · derivative.exercise_date: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F2 · derivative.expiration_date: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F3 · ownership.nature: These shares are held by Longwood Fund IV, L.P. ("Longwood"). The general partner of Longwood is Longwood Fund IV GP, LLC ("Longwood GP"). Voting, investment and dispositive decisions at Longwood GP with respect to the securities held by Longwood are made by an investment committee comprised of Christoph Westphal, Richard Aldrich and John Lawrence (collectively, the "IC Members"). Longwood GP and each of the IC Members may be deemed to share voting, investment and dispositive power over the securities held by Longwood and as a result may be deemed to have beneficial ownership over such securities. Longwood GP and each of the IC Members disclaims beneficial ownership over the securities held by Longwood, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-21-029479 · doc4.xml · derivative · entry 6

Westphal Christoph H · CIK 0001291961 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Voting Common Stock · 332,594 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F2 · price: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F2 · derivative.exercise_date: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F2 · derivative.expiration_date: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F3 · ownership.nature: These shares are held by Longwood Fund IV, L.P. ("Longwood"). The general partner of Longwood is Longwood Fund IV GP, LLC ("Longwood GP"). Voting, investment and dispositive decisions at Longwood GP with respect to the securities held by Longwood are made by an investment committee comprised of Christoph Westphal, Richard Aldrich and John Lawrence (collectively, the "IC Members"). Longwood GP and each of the IC Members may be deemed to share voting, investment and dispositive power over the securities held by Longwood and as a result may be deemed to have beneficial ownership over such securities. Longwood GP and each of the IC Members disclaims beneficial ownership over the securities held by Longwood, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-21-029479 · doc4.xml · derivative · entry 5

Westphal Christoph H · CIK 0001291961 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Voting Common Stock · 641,848 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · derivative.exercise_price: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F2 · price: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F2 · derivative.exercise_date: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F2 · derivative.expiration_date: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F3 · ownership.nature: These shares are held by Longwood Fund IV, L.P. ("Longwood"). The general partner of Longwood is Longwood Fund IV GP, LLC ("Longwood GP"). Voting, investment and dispositive decisions at Longwood GP with respect to the securities held by Longwood are made by an investment committee comprised of Christoph Westphal, Richard Aldrich and John Lawrence (collectively, the "IC Members"). Longwood GP and each of the IC Members may be deemed to share voting, investment and dispositive power over the securities held by Longwood and as a result may be deemed to have beneficial ownership over such securities. Longwood GP and each of the IC Members disclaims beneficial ownership over the securities held by Longwood, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-21-029479 · doc4.xml · nonDerivative · entry 4

Westphal Christoph H · CIK 0001291961 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 1,278,838

F4 · shares: Represents shares purchased in the Issuer's initial public offering.

F3 · ownership.nature: These shares are held by Longwood Fund IV, L.P. ("Longwood"). The general partner of Longwood is Longwood Fund IV GP, LLC ("Longwood GP"). Voting, investment and dispositive decisions at Longwood GP with respect to the securities held by Longwood are made by an investment committee comprised of Christoph Westphal, Richard Aldrich and John Lawrence (collectively, the "IC Members"). Longwood GP and each of the IC Members may be deemed to share voting, investment and dispositive power over the securities held by Longwood and as a result may be deemed to have beneficial ownership over such securities. Longwood GP and each of the IC Members disclaims beneficial ownership over the securities held by Longwood, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-21-029479 · doc4.xml · nonDerivative · entry 3

Westphal Christoph H · CIK 0001291961 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 1,145,505

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · price: Each share of the Issuer's preferred stock automatically converted on a one for one basis into Voting Common Stock immediately prior to the closing of the Issuer's initial public offering, without payment or further consideration. The preferred stock had no expiration date.

F3 · ownership.nature: These shares are held by Longwood Fund IV, L.P. ("Longwood"). The general partner of Longwood is Longwood Fund IV GP, LLC ("Longwood GP"). Voting, investment and dispositive decisions at Longwood GP with respect to the securities held by Longwood are made by an investment committee comprised of Christoph Westphal, Richard Aldrich and John Lawrence (collectively, the "IC Members"). Longwood GP and each of the IC Members may be deemed to share voting, investment and dispositive power over the securities held by Longwood and as a result may be deemed to have beneficial ownership over such securities. Longwood GP and each of the IC Members disclaims beneficial ownership over the securities held by Longwood, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-21-028652 · doc4.xml · derivative · entry 1

Silver Brian M. · CIK 0001860597 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 250,441

Underlying: Voting Common Stock · 250,441 shares

Expires 2031-07-14

F1 · derivative.exercise_date: The shares subject to this option will vest with respect to 25% of the shares after 12 months of continuous service to the Issuer following May 3, 2021, and the balance will vest in equal monthly installments over the next 36 months of continuous service to the issuer. If Mr. Silver's employment is terminated without cause or for good reason within the three months prior to a change of control or within 12 months at or following a change of control, any unvested shares or equity awards shall immediately vest.

SEC source: 0000899243-21-028648 · doc4.xml · derivative · entry 2

Gruia Gabriela · CIK 0001860326 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,146

Underlying: Voting Common Stock · 9,146 shares

Expires 2031-07-14

F2 · derivative.exercise_date: The shares subject to this option will vest in 12 equal monthly installments upon the completion of each month of continuous service to the Issuer after May 4, 2022.

SEC source: 0000899243-21-028648 · doc4.xml · derivative · entry 1

Gruia Gabriela · CIK 0001860326 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,146

Underlying: Voting Common Stock · 9,146 shares

Expires 2031-07-14

F1 · derivative.exercise_date: The shares subject to this option will vest in 36 equal monthly installments upon the completion of each month of continuous service to the Issuer after May 4, 2021 .