TCRX

SEC source: 0000950170-24-073694 · ownership.xml · derivative · entry 1

Klencke Barbara · CIK 0001647647 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 47,500

Underlying: Voting Common Stock · 47,500 shares

Expires 2034-06-11

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 12, 2025 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

SEC source: 0000950170-24-073695 · ownership.xml · derivative · entry 1

Dorton Katina · CIK 0001617541 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 47,500

Underlying: Voting Common Stock · 47,500 shares

Expires 2034-06-11

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 12, 2025 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

SEC source: 0000950170-24-073692 · ownership.xml · derivative · entry 2

Nicholson Garry A · CIK 0001640861 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 23,750

Underlying: Voting Common Stock · 23,750 shares

Expires 2034-06-11

F2 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable with respect to one-third of the shares on June 12, 2025, with the balance vesting thereafter in 24 equal monthly installments, subject to the Reporting Person's continued service at each such time.

SEC source: 0000950170-24-073692 · ownership.xml · derivative · entry 1

Nicholson Garry A · CIK 0001640861 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 47,500

Underlying: Voting Common Stock · 47,500 shares

Expires 2034-06-11

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 12, 2025 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

SEC source: 0000950170-24-052872 · ownership.xml · derivative · entry 1

Louis Chrystal · CIK 0002018696 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 380,000

Underlying: Voting Common Stock · 380,000 shares

Expires 2034-04-30

F1 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable with respect to 25% of the shares on the one-year anniversary of April 22, 2024, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer.

SEC source: 0000950170-24-046916 · ownership.xml · derivative · 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: No plan indicated

Ownership: Indirect · See Footnotes

Disclosed balance after: 43,158,741

Underlying: Common Stock · 8,851,451 shares

Expires not disclosed

F1 · shares: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 825,968 and 8,851,451 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $7.1299 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed on April 19, 2024. The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F1 · derivative.exercise_date: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 825,968 and 8,851,451 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $7.1299 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed on April 19, 2024. The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F2 · derivative.exercise_date: By written notice to the Issuer, the Funds may from time to time increase or decrease the Maximum Percentage applicable to that Fund to any other percentage not in excess of 19.99%. Any such increase will not be effective until the 61st day after such notice is delivered to the Issuer.

F1 · derivative.expiration_date: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 825,968 and 8,851,451 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $7.1299 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed on April 19, 2024. The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F1 · ownership.nature: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 825,968 and 8,851,451 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $7.1299 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed on April 19, 2024. The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F2 · ownership.nature: By written notice to the Issuer, the Funds may from time to time increase or decrease the Maximum Percentage applicable to that Fund to any other percentage not in excess of 19.99%. Any such increase will not be effective until the 61st day after such notice is delivered to the Issuer.

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.

F6 · 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: 0000950170-24-046916 · ownership.xml · derivative · 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: No plan indicated

Ownership: Indirect · See Footnotes

Disclosed balance after: 4,018,678

Underlying: Common Stock · 825,968 shares

Expires not disclosed

F1 · shares: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 825,968 and 8,851,451 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $7.1299 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed on April 19, 2024. The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F1 · derivative.exercise_date: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 825,968 and 8,851,451 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $7.1299 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed on April 19, 2024. The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F2 · derivative.exercise_date: By written notice to the Issuer, the Funds may from time to time increase or decrease the Maximum Percentage applicable to that Fund to any other percentage not in excess of 19.99%. Any such increase will not be effective until the 61st day after such notice is delivered to the Issuer.

F1 · derivative.expiration_date: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 825,968 and 8,851,451 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $7.1299 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed on April 19, 2024. The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F1 · ownership.nature: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 825,968 and 8,851,451 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $7.1299 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed on April 19, 2024. The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F2 · ownership.nature: By written notice to the Issuer, the Funds may from time to time increase or decrease the Maximum Percentage applicable to that Fund to any other percentage not in excess of 19.99%. Any such increase will not be effective until the 61st day after such notice is delivered to the Issuer.

F3 · 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.

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: 0000902664-24-003030 · ownership.xml · derivative · entry 1

Lynx1 Capital Management LP · CIK 0001910456 · 10% owner

Nichols Weston · CIK 0001746376 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 5,000,000

Underlying: Common Stock · 5,000,000 shares

Expires not disclosed

F1 · derivative.exercise_date: Subject to the terms and conditions set forth in the Pre-funded Warrant, the holder thereof may, at any time and from time to time on or after April 19, 2024, exercise the Pre-funded Warrant until it has been exercised in full. The Pre-funded Warrants reported herein contain an exercise limitation prohibiting the holder from exercising the Pre-Funded Warrants until such time as the holder, together with the Reporting Persons and certain other related parties, would not beneficially own after any such exercise more than 4.99% of the then issued and outstanding Common Stock (the "Blocker"). Due to the Blocker, the Pre-funded Warrants beneficially owned by the Reporting Persons are not presently exercisable.

F1 · derivative.expiration_date: Subject to the terms and conditions set forth in the Pre-funded Warrant, the holder thereof may, at any time and from time to time on or after April 19, 2024, exercise the Pre-funded Warrant until it has been exercised in full. The Pre-funded Warrants reported herein contain an exercise limitation prohibiting the holder from exercising the Pre-Funded Warrants until such time as the holder, together with the Reporting Persons and certain other related parties, would not beneficially own after any such exercise more than 4.99% of the then issued and outstanding Common Stock (the "Blocker"). Due to the Blocker, the Pre-funded Warrants beneficially owned by the Reporting Persons are not presently exercisable.

F2 · ownership.nature: The securities to which this filing relates are held directly by Lynx1 Master Fund LP to which Lynx1 Capital Management LP (the "Investment Manager") serves as investment manager. Weston Nichols ("Mr. Nichols") is the sole member of Lynx1 Capital Management GP LLC, the general partner of the Investment Manager. Each of the Investment Manager and Mr. Nichols disclaims beneficial ownership of the securities to which this filing relates for purposes of Section 16 of the Securities and Exchange Act of 1934, as amended, except to the extent of his or its pecuniary interest therein, if any.

SEC source: 0000950170-24-010522 · ownership.xml · derivative · entry 1

Amello Jason · CIK 0001451805 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 750,000

Underlying: Voting Common Stock · 750,000 shares

Expires 2034-01-31

F1 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable with respect to 25% of the shares on the one-year anniversary of January 29, 2024, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer.

SEC source: 0000950170-25-018131 · ownership.xml · derivative · entry 1

ZDRAVESKI ZORAN · CIK 0001741285 · See Remarks

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 52,500

Underlying: Voting Common Stock · 52,500 shares

Expires 2034-01-12

F1 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable with respect to 25% of the shares on the one-year anniversary of January 12, 2024, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer.

SEC source: 0000950170-25-018130 · ownership.xml · derivative · entry 1

Dworak Leiden · CIK 0001986012 · Vice President, Finance

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 46,875

Underlying: Voting Common Stock · 46,875 shares

Expires 2034-01-12

F1 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable with respect to 25% of the shares on the one-year anniversary of January 12, 2024, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer.

SEC source: 0000950170-25-018125 · ownership.xml · derivative · entry 1

MacBeath Gavin · CIK 0001738082 · Director · Chief Executive Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 160,000

Underlying: Voting Common Stock · 160,000 shares

Expires 2034-01-12

F1 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable with respect to 25% of the shares on the one-year anniversary of January 12, 2024, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer.

SEC source: 0000950170-23-072291 · ownership.xml · nonDerivative · entry 2

BARBERICH TIMOTHY J · CIK 0001120355 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 67,027

SEC source: 0000950170-23-072291 · ownership.xml · nonDerivative · entry 1

BARBERICH TIMOTHY J · CIK 0001120355 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 66,710

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $4.63 to $5.08, 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 range set forth in this footnote (1) to this Form 4.

SEC source: 0000950170-23-071208 · ownership.xml · nonDerivative · entry 1

Klencke Barbara · CIK 0001647647 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 30,000

SEC source: 0000950170-23-068925 · ownership.xml · derivative · entry 1

Woods Keith · CIK 0001996804 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,500

Underlying: Voting Common Stock · 17,500 shares

Expires 2033-12-05

F1 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) December 6, 2024 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

SEC source: 0000950170-23-034156 · ownership.xml · derivative · entry 1

Dworak Leiden · CIK 0001986012 · Chief Accounting Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,000

Underlying: Voting Common Stock · 25,000 shares

Expires 2033-07-20

F1 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable with respect to 25% of the shares on the one-year anniversary of July 21, 2023, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer.

SEC source: 0001209191-23-037371 · doc4.xml · derivative · entry 2

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director

667, L.P. · CIK 0001551139 · Director

BAKER FELIX · CIK 0001087940 · Director

BAKER JULIAN · CIK 0001087939 · Director

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

Baker Brothers Life Sciences LP · CIK 0001363364 · Director

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnotes

Disclosed balance after: 35,000

Underlying: Common Stock · 35,000 shares

Expires 2033-06-13

F1 · shares: Includes 35,000 non-qualified stock options ("Stock Options") exercisable solely into common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer") granted by the Issuer to Dr. Stephen Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser") on June 13, 2023, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $2.66 and vest in full upon the earlier of the first anniversary of the grant date or the Issuer's 2024 annual meeting subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board"). The Stock Options expire on June 13, 2033. Dr. Biggar serves on the Board as a representative of Baker Brothers Life Sciences, L.P. ("Life Sciences") and 667, L.P. ("667", and together with Life Sciences, the "Funds") and their affiliates.

F1 · derivative.exercise_date: Includes 35,000 non-qualified stock options ("Stock Options") exercisable solely into common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer") granted by the Issuer to Dr. Stephen Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser") on June 13, 2023, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $2.66 and vest in full upon the earlier of the first anniversary of the grant date or the Issuer's 2024 annual meeting subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board"). The Stock Options expire on June 13, 2033. Dr. Biggar serves on the Board as a representative of Baker Brothers Life Sciences, L.P. ("Life Sciences") and 667, L.P. ("667", and together with Life Sciences, the "Funds") and their affiliates.

F1 · ownership.nature: Includes 35,000 non-qualified stock options ("Stock Options") exercisable solely into common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer") granted by the Issuer to Dr. Stephen Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser") on June 13, 2023, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $2.66 and vest in full upon the earlier of the first anniversary of the grant date or the Issuer's 2024 annual meeting subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board"). The Stock Options expire on June 13, 2033. Dr. Biggar serves on the Board as a representative of Baker Brothers Life Sciences, L.P. ("Life Sciences") and 667, L.P. ("667", and together with Life Sciences, the "Funds") and their affiliates.

F3 · ownership.nature: Pursuant to the policies of the Adviser, Dr. Biggar does not have a right to any of the Issuer's securities issued as compensation for his service on the Board and the Funds are entitled to an indirect proportionate pecuniary interest in the securities. The Funds each own an indirect proportionate pecuniary interest in the Stock Options. Solely as a result of their ownership interest in (i) the general partners of the Funds and (ii) the Funds, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the Stock Options and any Common Stock acquired upon the exercise of Stock Options (i.e. no direct pecuniary interest).

F4 · ownership.nature: Pursuant to agreements between Dr. Biggar and the Adviser and the policies of the Adviser, the Adviser has voting and dispositive power over the Stock Options and any Common Stock acquired as a result of the exercise of the Stock Options.

F5 · ownership.nature: The acquisition of Stock Options reported on this form represents a single grant to Dr. Biggar of 35,000 Stock Options on Table II. This grant of 35,000 Stock Options for Dr. Biggar is reported for each of the Funds as each has an indirect pecuniary interest in such securities.

F6 · ownership.nature: 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 directly by the Funds or for the benefit of the Funds. 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 directly by the Funds or for the benefit of the Funds. The general partners of the Funds have relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held directly by the Funds of for the benefit of the Funds.

F7 · 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 or for the benefit of 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.

F8 · 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, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in the Stock Options reported in column 9 of Table II held for the benefit of 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: 0001209191-23-037371 · doc4.xml · derivative · entry 1

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director

667, L.P. · CIK 0001551139 · Director

BAKER FELIX · CIK 0001087940 · Director

BAKER JULIAN · CIK 0001087939 · Director

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

Baker Brothers Life Sciences LP · CIK 0001363364 · Director

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnotes

Disclosed balance after: 35,000

Underlying: Common Stock · 35,000 shares

Expires 2033-06-13

F1 · shares: Includes 35,000 non-qualified stock options ("Stock Options") exercisable solely into common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer") granted by the Issuer to Dr. Stephen Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser") on June 13, 2023, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $2.66 and vest in full upon the earlier of the first anniversary of the grant date or the Issuer's 2024 annual meeting subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board"). The Stock Options expire on June 13, 2033. Dr. Biggar serves on the Board as a representative of Baker Brothers Life Sciences, L.P. ("Life Sciences") and 667, L.P. ("667", and together with Life Sciences, the "Funds") and their affiliates.

F1 · derivative.exercise_date: Includes 35,000 non-qualified stock options ("Stock Options") exercisable solely into common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer") granted by the Issuer to Dr. Stephen Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser") on June 13, 2023, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $2.66 and vest in full upon the earlier of the first anniversary of the grant date or the Issuer's 2024 annual meeting subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board"). The Stock Options expire on June 13, 2033. Dr. Biggar serves on the Board as a representative of Baker Brothers Life Sciences, L.P. ("Life Sciences") and 667, L.P. ("667", and together with Life Sciences, the "Funds") and their affiliates.

F1 · ownership.nature: Includes 35,000 non-qualified stock options ("Stock Options") exercisable solely into common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer") granted by the Issuer to Dr. Stephen Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser") on June 13, 2023, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $2.66 and vest in full upon the earlier of the first anniversary of the grant date or the Issuer's 2024 annual meeting subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board"). The Stock Options expire on June 13, 2033. Dr. Biggar serves on the Board as a representative of Baker Brothers Life Sciences, L.P. ("Life Sciences") and 667, L.P. ("667", and together with Life Sciences, the "Funds") and their affiliates.

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 Stock Options reported in column 9 of Table II held for the benefit of 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.

F3 · ownership.nature: Pursuant to the policies of the Adviser, Dr. Biggar does not have a right to any of the Issuer's securities issued as compensation for his service on the Board and the Funds are entitled to an indirect proportionate pecuniary interest in the securities. The Funds each own an indirect proportionate pecuniary interest in the Stock Options. Solely as a result of their ownership interest in (i) the general partners of the Funds and (ii) the Funds, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the Stock Options and any Common Stock acquired upon the exercise of Stock Options (i.e. no direct pecuniary interest).

F4 · ownership.nature: Pursuant to agreements between Dr. Biggar and the Adviser and the policies of the Adviser, the Adviser has voting and dispositive power over the Stock Options and any Common Stock acquired as a result of the exercise of the Stock Options.

F5 · ownership.nature: The acquisition of Stock Options reported on this form represents a single grant to Dr. Biggar of 35,000 Stock Options on Table II. This grant of 35,000 Stock Options for Dr. Biggar is reported for each of the Funds as each has an indirect pecuniary interest in such securities.

F6 · ownership.nature: 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 directly by the Funds or for the benefit of the Funds. 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 directly by the Funds or for the benefit of the Funds. The general partners of the Funds have relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held directly by the Funds of for the benefit of the Funds.

F7 · 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 or for the benefit of 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: 0000899243-23-015646 · doc4.xml · derivative · entry 1

BARBERICH TIMOTHY J · CIK 0001120355 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 35,000

Underlying: Voting Common Stock · 35,000 shares

Expires 2033-06-12

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 13, 2024 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

SEC source: 0000899243-23-015644 · doc4.xml · derivative · entry 1

Barton Debora · CIK 0001936730 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 430,000

Underlying: Voting Common Stock · 430,000 shares

Expires 2033-06-12

F1 · derivative.exercise_date: 220,000 shares subject to this option shall vest and become exercisable with respect to 25% of the shares on the one-year anniversary of May 24, 2023, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer. The remaining 210,000 shares subject to this option shall vest and become exercisable with respect to 25% of the shares on February 2, 2025, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer, in each case subject to the Reporting Person's continued service at such time. This option was granted on May 24, 2023 subject to the approval of the Issuers' stockholders of an amendment to the TScan Therapeutics, Inc. 2021 Equity Incentive Plan, which was obtained on June 13, 2023.

SEC source: 0000899243-23-015636 · doc4.xml · derivative · entry 1

Silver Brian M. · CIK 0001860597 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 632,500

Underlying: Voting Common Stock · 632,500 shares

Expires 2033-06-12

F1 · derivative.exercise_date: 302,500 shares subject to this option shall vest and become exercisable with respect to 25% of the shares on the one-year anniversary of May 24, 2023, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer. The remaining 330,000 shares subject to this option shall vest and become exercisable with respect to 25% of the shares on February 2, 2025, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer, in each case subject to the Reporting Person's continued service at such time. This option was granted on May 24, 2023 subject to the approval of the Issuers' stockholders of an amendment to the TScan Therapeutics, Inc. 2021 Equity Incentive Plan, which was obtained on June 13, 2023.

SEC source: 0000899243-23-015640 · doc4.xml · derivative · entry 1

Gruia Gabriela · CIK 0001860326 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 35,000

Underlying: Voting Common Stock · 35,000 shares

Expires 2033-06-12

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 13, 2024 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

SEC source: 0000899243-23-015642 · doc4.xml · derivative · entry 1

Dorton Katina · CIK 0001617541 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 35,000

Underlying: Voting Common Stock · 35,000 shares

Expires 2033-06-12

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 13, 2024 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

SEC source: 0000899243-23-015639 · doc4.xml · derivative · entry 1

Klencke Barbara · CIK 0001647647 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 36,524

Underlying: Voting Common Stock · 36,524 shares

Expires 2033-06-12

F1 · derivative.exercise_date: 35,000 shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) June 13, 2024 and (ii) the next annual meeting of the Issuer's stockholders, with 1,524 shares subject to this option vesting and becoming exercisable in full on June 13, 2023, in each case subject to the Reporting Person's continued service at such time.

SEC source: 0000899243-23-015635 · doc4.xml · derivative · entry 1

MacBeath Gavin · CIK 0001738082 · Director · Chief Executive Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 1,121,300

Underlying: Voting Common Stock · 1,121,300 shares

Expires 2033-06-12

F1 · derivative.exercise_date: 536,300 shares subject to this option shall vest and become exercisable with respect to 25% of the shares on the one-year anniversary of May 24, 2023, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer. The remaining 585,000 shares subject to this option shall vest and become exercisable with respect to 25% of the shares on February 2, 2025, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer, in each case subject to the Reporting Person's continued service at such time. This option was granted on May 24, 2023 subject to the approval of the Issuers' stockholders of an amendment to the TScan Therapeutics, Inc. 2021 Equity Incentive Plan, which was obtained on June 13, 2023.

SEC source: 0000899243-23-015632 · doc4.xml · derivative · entry 1

ZDRAVESKI ZORAN · CIK 0001741285 · Chief Legal Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 430,000

Underlying: Voting Common Stock · 430,000 shares

Expires 2033-06-12

F1 · derivative.exercise_date: 220,000 shares subject to this option shall vest and become exercisable with respect to 25% of the shares on the one-year anniversary of May 24, 2023, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer. The remaining 210,000 shares subject to this option shall vest and become exercisable with respect to 25% of the shares on February 2, 2025, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer, in each case subject to the Reporting Person's continued service at such time. This option was granted on May 24, 2023 subject to the approval of the Issuers' stockholders of an amendment to the TScan Therapeutics, Inc. 2021 Equity Incentive Plan, which was obtained on June 13, 2023.

SEC source: 0000899243-23-014618 · doc4.xml · nonDerivative · entry 1

BARBERICH TIMOTHY J · CIK 0001120355 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 37,880

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $2.60 to $2.64, 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 range set forth in this footnote (1) to this Form 4.

F2 · balance_after: The Reporting Person's prior reports inadvertently included 33,259 shares of the Issuer's Voting Common Stock held by the Barberich Family Trust as directly owned by the Reporting Person. These shares are held in a trust for the benefit of the Reporting Person's children. The Reporting Person's spouse is the grantor of the trust and retains certain rights to remove and replace the trustee of the trust. The Reporting Person disclaims beneficial ownership of these shares.

SEC source: 0001209191-23-033647 · doc4.xml · derivative · entry 2

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director

667, L.P. · CIK 0001551139 · Director

BAKER FELIX · CIK 0001087940 · Director

BAKER JULIAN · CIK 0001087939 · Director

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

Baker Brothers Life Sciences LP · CIK 0001363364 · Director

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnotes

Disclosed balance after: 34,307,290

Underlying: Common Stock · 34,307,290 shares

Expires not disclosed

F1 · derivative.exercise_date: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences" and together with 667, the "Funds") purchased 3,192,710 and 34,307,290 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $1.9999 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed for the Commmon Stock on May 31, 2023 and for the Prefunded Warrants on June 1, 2023.

F2 · derivative.exercise_date: By written notice to the Issuer, the Funds may from time to time increase or decrease the Maximum Percentage applicable to that Fund to any other percentage not in excess of 19.99%. Any such increase will not be effective until the 61st day after such notice is delivered to the Issuer.

F3 · derivative.exercise_date: The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F1 · derivative.expiration_date: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences" and together with 667, the "Funds") purchased 3,192,710 and 34,307,290 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $1.9999 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed for the Commmon Stock on May 31, 2023 and for the Prefunded Warrants on June 1, 2023.

F2 · derivative.expiration_date: By written notice to the Issuer, the Funds may from time to time increase or decrease the Maximum Percentage applicable to that Fund to any other percentage not in excess of 19.99%. Any such increase will not be effective until the 61st day after such notice is delivered to the Issuer.

F3 · derivative.expiration_date: The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F4 · 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.

F6 · 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.

F7 · 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 7 of Table II beneficially owned 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: 0001209191-23-033647 · doc4.xml · derivative · entry 1

BAKER BROS. ADVISORS LP · CIK 0001263508 · Director

667, L.P. · CIK 0001551139 · Director

BAKER FELIX · CIK 0001087940 · Director

BAKER JULIAN · CIK 0001087939 · Director

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

Baker Brothers Life Sciences LP · CIK 0001363364 · Director

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnotes

Disclosed balance after: 3,192,710

Underlying: Common Stock · 3,192,710 shares

Expires not disclosed

F1 · derivative.exercise_date: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences" and together with 667, the "Funds") purchased 3,192,710 and 34,307,290 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $1.9999 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed for the Commmon Stock on May 31, 2023 and for the Prefunded Warrants on June 1, 2023.

F2 · derivative.exercise_date: By written notice to the Issuer, the Funds may from time to time increase or decrease the Maximum Percentage applicable to that Fund to any other percentage not in excess of 19.99%. Any such increase will not be effective until the 61st day after such notice is delivered to the Issuer.

F3 · derivative.exercise_date: The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F1 · derivative.expiration_date: 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences" and together with 667, the "Funds") purchased 3,192,710 and 34,307,290 warrants to purchase common stock ("Common Stock") of TScan Therapeutics, Inc. (the "Issuer"), respectively, for $1.9999 per share ("Prefunded Warrants") pursuant to an underwritten offering that closed for the Commmon Stock on May 31, 2023 and for the Prefunded Warrants on June 1, 2023.

F2 · derivative.expiration_date: By written notice to the Issuer, the Funds may from time to time increase or decrease the Maximum Percentage applicable to that Fund to any other percentage not in excess of 19.99%. Any such increase will not be effective until the 61st day after such notice is delivered to the Issuer.

F3 · derivative.expiration_date: The Prefunded Warrants have no expiration date and are exercisable at an exercise price of $0.0001 per share immediately at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such exercise the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would beneficially own, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Maximum Percentage") immediately prior to and following such exercise.

F4 · 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.

F5 · 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 7 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.

F6 · 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.

SEC source: 0000902664-23-003407 · ownership.xml · nonDerivative · entry 3

Lynx1 Capital Management LP · CIK 0001910456 · 10% owner

Nichols Weston · CIK 0001746376 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 5,224,600

F1 · ownership.nature: The securities to which this filing relates are held directly by Lynx1 Master Fund LP to which Lynx1 Capital Management LP (the "Investment Manager") serves as investment manager. Weston Nichols ("Mr. Nichols") is the sole member of Lynx1 Capital Management GP LLC, the general partner of the Investment Manager. Each of the Investment Manager and Mr. Nichols disclaims beneficial ownership of the securities to which this filing relates for purposes of ection 16 of the Securities and Exchange Act of 1934, as amended, except to the extent of his or its pecuniary interest therein, if any.

SEC source: 0000902664-23-003407 · ownership.xml · nonDerivative · entry 2

Lynx1 Capital Management LP · CIK 0001910456 · 10% owner

Nichols Weston · CIK 0001746376 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 5,225,000

F1 · ownership.nature: The securities to which this filing relates are held directly by Lynx1 Master Fund LP to which Lynx1 Capital Management LP (the "Investment Manager") serves as investment manager. Weston Nichols ("Mr. Nichols") is the sole member of Lynx1 Capital Management GP LLC, the general partner of the Investment Manager. Each of the Investment Manager and Mr. Nichols disclaims beneficial ownership of the securities to which this filing relates for purposes of ection 16 of the Securities and Exchange Act of 1934, as amended, except to the extent of his or its pecuniary interest therein, if any.

SEC source: 0000902664-23-003407 · ownership.xml · nonDerivative · entry 1

Lynx1 Capital Management LP · CIK 0001910456 · 10% owner

Nichols Weston · CIK 0001746376 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 5,240,000

F1 · ownership.nature: The securities to which this filing relates are held directly by Lynx1 Master Fund LP to which Lynx1 Capital Management LP (the "Investment Manager") serves as investment manager. Weston Nichols ("Mr. Nichols") is the sole member of Lynx1 Capital Management GP LLC, the general partner of the Investment Manager. Each of the Investment Manager and Mr. Nichols disclaims beneficial ownership of the securities to which this filing relates for purposes of ection 16 of the Securities and Exchange Act of 1934, as amended, except to the extent of his or its pecuniary interest therein, if any.

SEC source: 0000899243-23-010999 · doc4.xml · derivative · entry 1

Klencke Barbara · CIK 0001647647 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 9,146

Underlying: Voting Common Stock · 9,146 shares

Expires 2033-04-05

F1 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable in thirty-six equal monthly installments following April 6, 2023, subject to the Reporting Person's continued service at such time.

SEC source: 0000899243-23-004061 · doc4.xml · derivative · entry 1

Barton Debora · CIK 0001936730 · Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 50,000

Underlying: Voting Common Stock · 50,000 shares

Expires 2033-02-01

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following February 2, 2023, 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: 0000899243-23-004063 · doc4.xml · derivative · entry 1

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 100,000

Underlying: Voting Common Stock · 100,000 shares

Expires 2033-02-01

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following February 2, 2023, 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: 0000899243-23-004062 · doc4.xml · derivative · entry 1

MacBeath Gavin · CIK 0001738082 · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 40,000

Underlying: Voting Common Stock · 40,000 shares

Expires 2033-02-01

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following February 2, 2023, 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: 0000899243-23-004064 · doc4.xml · derivative · entry 1

ZDRAVESKI ZORAN · CIK 0001741285 · Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 35,000

Underlying: Voting Common Stock · 35,000 shares

Expires 2033-02-01

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following February 2, 2023, 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: 0000899243-22-039506 · doc4.xml · nonDerivative · entry 2

Silver Brian M. · CIK 0001860597 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 32,885

F2 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $1.55 to $1.57, inclusive.

SEC source: 0000899243-22-039506 · doc4.xml · nonDerivative · entry 1

Silver Brian M. · CIK 0001860597 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 29,727

F1 · price: The price reported in Column 4 is a weighted average price. These securities were purchased in multiple transactions at prices ranging from $1.46 to $1.55, 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 footnotes (1) and (2) to this Form 4.

SEC source: 0000899243-22-026846 · doc4.xml · derivative · entry 1

Silver Brian M. · CIK 0001860597 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 220,000

Underlying: Voting Common Stock · 220,000 shares

Expires 2032-07-24

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following July 25, 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: 0000899243-22-026848 · doc4.xml · derivative · entry 1

Desmarais William · CIK 0001860207 · Chief Business Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 30,000

Underlying: Voting Common Stock · 30,000 shares

Expires 2032-07-24

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following July 25, 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: 0000899243-22-026847 · doc4.xml · derivative · entry 1

ZDRAVESKI ZORAN · CIK 0001741285 · Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 50,000

Underlying: Voting Common Stock · 50,000 shares

Expires 2032-07-24

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following July 25, 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: 0000899243-22-026849 · doc4.xml · derivative · entry 1

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 100,000

Underlying: Voting Common Stock · 100,000 shares

Expires 2032-07-24

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following July 25, 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: 0000899243-22-026844 · doc4.xml · derivative · entry 1

MacBeath Gavin · CIK 0001738082 · See Remarks

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 100,000

Underlying: Voting Common Stock · 100,000 shares

Expires 2032-07-24

F1 · derivative.exercise_date: The shares subject to this option vest over 4 years of service following July 25, 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: 0000899243-22-025626 · doc4.xml · derivative · entry 1

Barton Debora · CIK 0001936730 · Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 150,000

Underlying: Voting Common Stock · 150,000 shares

Expires 2032-07-04

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 July 5, 2022, and the balance will vest in equal monthly installments over the next 36 months of continuous service to the Issuer.

SEC source: 0001209191-22-034093 · doc4.xml · derivative · 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: 9,146

Underlying: Common Stock · 9,146 shares

Expires 2032-05-31

F1 · derivative.exercise_date: 9,146 non-qualified stock options ("Stock Options") exercisable solely into common stock of TScan Therapeutics, Inc. (the "Issuer") were granted under the Issuer's 2021 Equity Incentive Plan to Dr. Stephen Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser") in his capacity as a director of the Issuer. The Stock Options with a strike price of $3.17 vest in full upon the earlier of the first anniversary of the grant date or the Issuer's 2023 annual meeting, subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board"). The Stock Options expire on May 31, 2032. Dr. Biggar serves on the Board as a representative of Baker Brothers Life Sciences, L.P. ("Life Sciences") and 667, L.P. ("667", and together with Life Sciences, the "Funds").

F1 · ownership.nature: 9,146 non-qualified stock options ("Stock Options") exercisable solely into common stock of TScan Therapeutics, Inc. (the "Issuer") were granted under the Issuer's 2021 Equity Incentive Plan to Dr. Stephen Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser") in his capacity as a director of the Issuer. The Stock Options with a strike price of $3.17 vest in full upon the earlier of the first anniversary of the grant date or the Issuer's 2023 annual meeting, subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board"). The Stock Options expire on May 31, 2032. Dr. Biggar serves on the Board as a representative of Baker Brothers Life Sciences, L.P. ("Life Sciences") and 667, L.P. ("667", and together with Life Sciences, the "Funds").

F2 · ownership.nature: The policies of the Funds and the Adviser do not permit full-time employees of the Adviser or managing members of the Adviser GP (as defined below) to receive compensation for serving as a director of the Issuer. The Funds are entitled to receive all of the pecuniary interest in the securities issued. The Funds each own an indirect proportionate pecuniary interest in the Stock Options. Solely as a result of Felix J. Baker's and Julian C. Baker's ownership interest in (i) the general partners of the Funds and (ii) the Funds, Felix J. Baker and Julian C. Baker may be deemed to have an indirect pecuniary interest in the Stock Options (i.e. no direct pecuniary interest).

F3 · ownership.nature: 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 have relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds. The Adviser has investment and dispositive power over the Stock Options and any common stock of the Issuer received as a result of the exercise of Stock Options.

F4 · 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: 0000899243-22-020964 · doc4.xml · derivative · entry 1

BARBERICH TIMOTHY J · CIK 0001120355 · 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: 0000899243-22-020965 · 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 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: 0000899243-22-020963 · doc4.xml · derivative · entry 1

Dorton Katina · CIK 0001617541 · 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.