TCRX

The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) May 20, 2027 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) May 20, 2027 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) May 20, 2027 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) May 20, 2027 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) May 20, 2027 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

Includes 67,000 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 R. Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser"), on May 20, 2026, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended and Restated 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $0.9946 per share, and vest on the earlier of the first anniversary of the grant date or the date of the next annual meeting of stockholders of the Issuer, subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board") through the vesting date. The Stock Options expire on May 19, 2036.

Dr. Biggar serves on the Board as a representative of 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") and their affiliates and control persons.

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.

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 for the benefit of 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 for the benefit of 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 for the benefit of the Funds.

Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held 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.

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 such securities. The Funds each own an indirect proportionate pecuniary interest in such securities. 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 shares of Common Stock, Stock Options and Common Stock issued upon exercise of Stock Options (i.e. no direct pecuniary interest) issued as compensation for such Board service.

Pursuant to the policies of the Adviser, the Adviser has voting and dispositive power over the Stock Options and any Common Stock received as a result of the exercise of Stock Options.

The acquisition of Stock Options reported on this form represents a single grant to Dr. Biggar of 67,000 Stock Options on Table II. This grant of 67,000 Stock Options for Dr. Biggar is reported for each of the Funds as each has an indirect pecuniary interest in such securities.

Includes 67,000 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 R. Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser"), on May 20, 2026, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended and Restated 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $0.9946 per share, and vest on the earlier of the first anniversary of the grant date or the date of the next annual meeting of stockholders of the Issuer, subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board") through the vesting date. The Stock Options expire on May 19, 2036.

Dr. Biggar serves on the Board as a representative of 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") and their affiliates and control persons.

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 for the benefit of 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 for the benefit of 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 for the benefit of the Funds.

Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held 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.

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 such securities. The Funds each own an indirect proportionate pecuniary interest in such securities. 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 shares of Common Stock, Stock Options and Common Stock issued upon exercise of Stock Options (i.e. no direct pecuniary interest) issued as compensation for such Board service.

Pursuant to the policies of the Adviser, the Adviser has voting and dispositive power over the Stock Options and any Common Stock received as a result of the exercise of Stock Options.

The acquisition of Stock Options reported on this form represents a single grant to Dr. Biggar of 67,000 Stock Options on Table II. This grant of 67,000 Stock Options for Dr. Biggar is reported for each of the Funds as each has an indirect pecuniary interest in such securities.

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.

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 20, 2026, with the balance vesting thereafter in equal monthly installments over the next 36 months, subject to the Reporting Person's continued service to the Issuer on each vesting 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 20, 2026, with the balance vesting thereafter in equal monthly installments over the next 36 months, subject to the Reporting Person's continued service to the Issuer on each vesting 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 20, 2026, with the balance vesting thereafter in equal monthly installments over the next 36 months, subject to the Reporting Person's continued service to the Issuer on each vesting 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 20, 2026, with the balance vesting thereafter in equal monthly installments over the next 36 months, subject to the Reporting Person's continued service to the Issuer on each vesting 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 20, 2026, with the balance vesting thereafter in equal monthly installments over the next 36 months, subject to the Reporting Person's continued service to the Issuer on each vesting date.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $0.8958 to $0.90, 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, upon request, full information regarding the number of shares purchased at each separate price within the range set forth herein.

The securities to which this filing relates are held directly by Lynx1 Master Fund LP and a managed account 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.

The securities to which this filing relates are held directly by Lynx1 Master Fund LP and a managed account 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.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $0.8862 to $0.90, 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, upon request, full information regarding the number of shares purchased at each separate price within the range set forth herein.

The securities to which this filing relates are held directly by Lynx1 Master Fund LP and a managed account 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.

Includes 67,000 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 R. Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser"), on June 30, 2025, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended and Restated 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $1.45 per share, and vest on the earlier of the first anniversary of the grant date or the date of the next annual meeting of stockholders of the Issuer, subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board") through the vesting date. The Stock Options expire on June 29, 2035.

Dr. Biggar serves on the Board as a representative of 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") and their affiliates and control persons.

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 for the benefit of 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 for the benefit of 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 for the benefit of the Funds.

Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held 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.

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 such securities. The Funds each own an indirect proportionate pecuniary interest in such securities. 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 shares of Common Stock, Stock Options and Common Stock issued upon exercise of Stock Options (i.e. no direct pecuniary interest) issued as compensation for such Board service.

Pursuant to the policies of the Adviser, the Adviser has voting and dispositive power over the Stock Options and any Common Stock received as a result of the exercise of Stock Options.

The acquisition of Stock Options reported on this form represents a single grant to Dr. Biggar of 67,000 Stock Options on Table II. This grant of 67,000 Stock Options for Dr. Biggar is reported for each of the Funds as each has an indirect pecuniary interest in such securities.

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.

Includes 67,000 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 R. Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser"), on June 30, 2025, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended and Restated 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $1.45 per share, and vest on the earlier of the first anniversary of the grant date or the date of the next annual meeting of stockholders of the Issuer, subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board") through the vesting date. The Stock Options expire on June 29, 2035.

Dr. Biggar serves on the Board as a representative of 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") and their affiliates and control persons.

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.

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 for the benefit of 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 for the benefit of 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 for the benefit of the Funds.

Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held 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.

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 such securities. The Funds each own an indirect proportionate pecuniary interest in such securities. 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 shares of Common Stock, Stock Options and Common Stock issued upon exercise of Stock Options (i.e. no direct pecuniary interest) issued as compensation for such Board service.

Pursuant to the policies of the Adviser, the Adviser has voting and dispositive power over the Stock Options and any Common Stock received as a result of the exercise of Stock Options.

The acquisition of Stock Options reported on this form represents a single grant to Dr. Biggar of 67,000 Stock Options on Table II. This grant of 67,000 Stock Options for Dr. Biggar is reported for each of the Funds as each has an indirect pecuniary interest in such securities.

The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) June 30, 2026 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) June 30, 2026 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) June 30, 2026 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) June 30, 2026 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

The shares subject to this option shall vest and become exercisable in full upon the earlier to occur of (i) June 30, 2026 and (ii) the next annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service at such time.

The securities to which this filing relates are held directly by Lynx1 Master Fund LP and a managed account 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.

The securities to which this filing relates are held directly by Lynx1 Master Fund LP and a managed account 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.

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 3, 2025, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer.

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 3, 2025, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer.

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 3, 2025, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer.

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 3, 2025, with the balance vesting thereafter in equal monthly installments over the next 36 months of continuous service to the Issuer.

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 December 27, 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 9.99% 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.

The securities to which this filing relates are held directly by Lynx1 Master Fund LP and a managed account 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.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $2.855 to $3.00, 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, upon request, full information regarding the number of shares purchased at each separate price within the range set forth herein.

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.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $2.99 to $3.03, 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, upon request, full information regarding the number of shares purchased at each separate price within the range set forth herein.

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.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $4.335 to $4.350, 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, upon request, full information regarding the number of shares purchased at each separate price within the range set forth herein.

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.

Includes 7,500 shares of Voting Common Stock acquired under the TScan Therapeutics, Inc. 2021 Employee Stock Purchase Plan on December 31, 2022.

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.

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.

The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $5.56 to $5.91, inclusive. Full information regarding the number of shares sold at each separate price can be furnished to the Issuer, any security holder of the Issuer, or the SEC staff upon request.

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.

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.

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.

Includes 47,500 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 R. Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser"), on June 12, 2024, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended and Restated 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $8.88 per share, and vest on the earlier of the first anniversary of the grant date or the date of the next annual meeting of stockholders of the Issuer, subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board") through the vesting date. The Stock Options expire on June 11, 2034.

Dr. Biggar serves on the Board as a representative of 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") and their affiliates and control persons.

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.

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 for the benefit of 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 for the benefit of 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 for the benefit of the Funds.

Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held 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.

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 such securities. The Funds each own an indirect proportionate pecuniary interest in such securities. 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 shares of Common Stock, Stock Options and Common Stock issued upon exercise of Stock Options (i.e. no direct pecuniary interest) issued as compensation for such Board service.

Pursuant to the policies of the Adviser, the Adviser has voting and dispositive power over the Stock Options and any Common Stock received as a result of the exercise of Stock Options.

The acquisition of Stock Options reported on this form represents a single grant to Dr. Biggar of 47,500 Stock Options on Table II. This grant of 47,500 Stock Options for Dr. Biggar is reported for each of the Funds as each has an indirect pecuniary interest in such securities.

Includes 47,500 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 R. Biggar, a full-time employee of Baker Bros. Advisors LP (the "Adviser"), on June 12, 2024, in his capacity as a director of the Issuer, pursuant to the Issuer's Amended and Restated 2021 Equity Incentive Plan (the "Incentive Plan"). The Stock Options have a strike price of $8.88 per share, and vest on the earlier of the first anniversary of the grant date or the date of the next annual meeting of stockholders of the Issuer, subject to Dr. Biggar's continued service on the board of directors of the Issuer (the "Board") through the vesting date. The Stock Options expire on June 11, 2034.

Dr. Biggar serves on the Board as a representative of 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") and their affiliates and control persons.

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 for the benefit of 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 for the benefit of 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 for the benefit of the Funds.

Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held 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.

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 such securities. The Funds each own an indirect proportionate pecuniary interest in such securities. 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 shares of Common Stock, Stock Options and Common Stock issued upon exercise of Stock Options (i.e. no direct pecuniary interest) issued as compensation for such Board service.

Pursuant to the policies of the Adviser, the Adviser has voting and dispositive power over the Stock Options and any Common Stock received as a result of the exercise of Stock Options.

The acquisition of Stock Options reported on this form represents a single grant to Dr. Biggar of 47,500 Stock Options on Table II. This grant of 47,500 Stock Options for Dr. Biggar is reported for each of the Funds as each has an indirect pecuniary interest in such securities.

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.

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.

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.

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.