ACET · Adicet Bio, Inc. · Insider Trading

1/6th of the shares subject to this option shall vest and become exercisable on each of the next six (6) monthly anniversaries of August 5, 2026, subject to the Reporting Person's continued service with the Issuer as of the applicable vesting dates.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date with partial acceleration tied to certain performance milestones, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date with partial acceleration tied to certain performance milestones, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

On April 27, 2026, RA Capital Healthcare Fund, L.P. (the "Fund") entered into an Exchange Agreement with the Issuer pursuant to which the Fund exchanged, for no additional consideration, 250,000 shares of the Issuer's Common Stock for a pre-funded warrant exercisable for up to 250,000 shares of the Issuer's Common Stock at an exercise price of $0.0001 per share (the "Pre-Funded Warrant").

The Pre-Funded Warrant has no expiration date and is exercisable immediately. Notwithstanding the foregoing, the Fund shall not be entitled to exercise the Pre-Funded Warrant to the extent that it would cause the aggregate number of shares of Common Stock beneficially owned by the Fund, together with its Attribution Parties (as defined in the Pre-Funded Warrant), to exceed 9.99% of the total number of issued and outstanding shares of Common Stock of the Issuer following such exercise.

RA Capital Management, L.P. (the "Adviser") is the investment manager for RA Capital Healthcare Fund, L.P. (the "Fund"). The general partner of the Adviser is RA Capital Management GP, LLC (the "Adviser GP"), of which Dr. Peter Kolchinsky and Mr. Rajeev Shah are the managing members. Each of the Adviser, the Adviser GP, the Fund, Dr. Kolchinsky and Mr. Shah disclaims beneficial ownership of any of the reported securities, except to the extent of its or his respective pecuniary interest therein.

Held directly by the Fund.

On April 27, 2026, RA Capital Healthcare Fund, L.P. (the "Fund") entered into an Exchange Agreement with the Issuer pursuant to which the Fund exchanged, for no additional consideration, 250,000 shares of the Issuer's Common Stock for a pre-funded warrant exercisable for up to 250,000 shares of the Issuer's Common Stock at an exercise price of $0.0001 per share (the "Pre-Funded Warrant").

RA Capital Management, L.P. (the "Adviser") is the investment manager for RA Capital Healthcare Fund, L.P. (the "Fund"). The general partner of the Adviser is RA Capital Management GP, LLC (the "Adviser GP"), of which Dr. Peter Kolchinsky and Mr. Rajeev Shah are the managing members. Each of the Adviser, the Adviser GP, the Fund, Dr. Kolchinsky and Mr. Shah disclaims beneficial ownership of any of the reported securities, except to the extent of its or his respective pecuniary interest therein.

Held directly by the Fund.

These securities are held of record by OrbiMed Israel Partners II, L.P. ("OIP II"). OrbiMed Israel GP II, L.P. ("OrbiMed Israel GP II") is the general partner of OIP II, and OrbiMed Advisors Israel II Limited ("OrbiMed Israel II") is the general partner of OrbiMed Israel GP II. By virtue of such relationships, OrbiMed Israel GP II and OrbiMed Israel II may be deemed to have voting and investment power over the shares of common stock held by OIP II and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed Israel II exercises this investment and voting power through an investment committee comprised of Carl L. Gordon, David Bonita, and Erez Chimovits, each of whom disclaims beneficial ownership over the shares of common stock held by OIP II.

Each of OrbiMed Advisors, OrbiMed BioFund, OrbiMed Israel GP, OrbiMed Israel GP II, OrbiMed Israel II, Genesis GP, GP V, and GP VI disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of his or its pecuniary interest therein, if any. This report shall not be deemed an admission that any such person or entity is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

These securities are held of record by OrbiMed Israel Partners Limited Partnership ("OIP"). OrbiMed Israel BioFund GP Limited Partnership ("OrbiMed BioFund") is the general partner of OIP, and OrbiMed Israel GP Ltd. ("OrbiMed Israel GP") is the general partner of OrbiMed BioFund. By virtue of such relationships, OrbiMed BioFund and OrbiMed Israel GP may be deemed to have voting and investment power over the shares of common stock held by OIP and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed Israel GP exercises this investment and voting power through an investment committee comprised of Carl L. Gordon and Erez Chimovits, each of whom disclaims beneficial ownership over the shares of common stock held by OIP.

Each of OrbiMed Advisors, OrbiMed BioFund, OrbiMed Israel GP, OrbiMed Israel GP II, OrbiMed Israel II, Genesis GP, GP V, and GP VI disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of his or its pecuniary interest therein, if any. This report shall not be deemed an admission that any such person or entity is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

These securities are held of record by OrbiMed Israel Partners Limited Partnership ("OIP"). OrbiMed Israel BioFund GP Limited Partnership ("OrbiMed BioFund") is the general partner of OIP, and OrbiMed Israel GP Ltd. ("OrbiMed Israel GP") is the general partner of OrbiMed BioFund. By virtue of such relationships, OrbiMed BioFund and OrbiMed Israel GP may be deemed to have voting and investment power over the shares of common stock held by OIP and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed Israel GP exercises this investment and voting power through an investment committee comprised of Carl L. Gordon and Erez Chimovits, each of whom disclaims beneficial ownership over the shares of common stock held by OIP.

Each of OrbiMed Advisors, OrbiMed BioFund, OrbiMed Israel GP, OrbiMed Israel GP II, OrbiMed Israel II, Genesis GP, GP V, and GP VI disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of his or its pecuniary interest therein, if any. This report shall not be deemed an admission that any such person or entity is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

These securities are held of record by OrbiMed Israel Partners Limited Partnership ("OIP"). OrbiMed Israel BioFund GP Limited Partnership ("OrbiMed BioFund") is the general partner of OIP, and OrbiMed Israel GP Ltd. ("OrbiMed Israel GP") is the general partner of OrbiMed BioFund. By virtue of such relationships, OrbiMed BioFund and OrbiMed Israel GP may be deemed to have voting and investment power over the shares of common stock held by OIP and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed Israel GP exercises this investment and voting power through an investment committee comprised of Carl L. Gordon and Erez Chimovits, each of whom disclaims beneficial ownership over the shares of common stock held by OIP.

Each of OrbiMed Advisors, OrbiMed BioFund, OrbiMed Israel GP, OrbiMed Israel GP II, OrbiMed Israel II, Genesis GP, GP V, and GP VI disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of his or its pecuniary interest therein, if any. This report shall not be deemed an admission that any such person or entity is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

(1) 1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

(1) 1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

(1) 1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

(1) 1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

(1) 1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $7.05 to $7.58 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 in this footnote.

RA Capital Management, L.P. (the "Adviser") is the investment manager for RA Capital Healthcare Fund, L.P. (the "Fund"). The general partner of the Adviser is RA Capital Management GP, LLC (the "Adviser GP"), of which Dr. Peter Kolchinsky and Mr. Rajeev Shah are the managing members. Each of the Adviser, the Adviser GP, the Fund, Dr. Kolchinsky and Mr. Shah disclaims beneficial ownership of any of the reported securities, except to the extent of its or his respective pecuniary interest therein.

Held directly by the Fund.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $6.89 to $7.48 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 in this footnote.

RA Capital Management, L.P. (the "Adviser") is the investment manager for RA Capital Healthcare Fund, L.P. (the "Fund"). The general partner of the Adviser is RA Capital Management GP, LLC (the "Adviser GP"), of which Dr. Peter Kolchinsky and Mr. Rajeev Shah are the managing members. Each of the Adviser, the Adviser GP, the Fund, Dr. Kolchinsky and Mr. Shah disclaims beneficial ownership of any of the reported securities, except to the extent of its or his respective pecuniary interest therein.

Held directly by the Fund.

The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $6.89 to $7.20 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 in this footnote.

RA Capital Management, L.P. (the "Adviser") is the investment manager for RA Capital Healthcare Fund, L.P. (the "Fund"). The general partner of the Adviser is RA Capital Management GP, LLC (the "Adviser GP"), of which Dr. Peter Kolchinsky and Mr. Rajeev Shah are the managing members. Each of the Adviser, the Adviser GP, the Fund, Dr. Kolchinsky and Mr. Shah disclaims beneficial ownership of any of the reported securities, except to the extent of its or his respective pecuniary interest therein.

Held directly by the Fund.

Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting of restricted stock units and does not represent a sale by the Reporting Person.

Reflects a 1-for-16 reverse stock split effected by the Issuer on December 30, 2025.

Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting of restricted stock units and does not represent a sale by the Reporting Person.

Reflects a 1-for-16 reverse stock split effected by the Issuer on December 30, 2025.

Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting of restricted stock units and does not represent a sale by the Reporting Person.

Reflects a 1-for-16 reverse stock split effected by the Issuer on December 30, 2025.

Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting of restricted stock units and does not represent a sale by the Reporting Person.

Reflects a 1-for-16 reverse stock split effected by the Issuer on December 30, 2025.

These securities were purchased in an underwritten registered direct offering.

These securities are held of record by OrbiMed Private Investments VI, LP ("OPI VI"). OrbiMed Capital GP VI LLC ("GP VI") is the general partner of OPI VI, and OrbiMed Advisors is the managing member of GP VI. By virtue of such relationships, GP VI and OrbiMed Advisors may be deemed to have voting and investment power over the shares of common stock held by OPI VI and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed Advisors exercises this investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership over the shares of common stock held by OPI VI.

Each of OrbiMed Advisors, OrbiMed BioFund, OrbiMed Israel GP, OrbiMed Israel GP II, OrbiMed Israel II, GP V, GP VI, and Genesis GP disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of his or its pecuniary interest therein, if any. This report shall not be deemed an admission that any such person or entity is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

These securities were purchased in an underwritten registered direct offering.

These securities are held of record by OrbiMed Private Investments V, LP ("OPI V"). OrbiMed Capital GP V LLC ("GP V") is the general partner of OPI V, and OrbiMed Advisors LLC ("OrbiMed Advisors"), a registered investment adviser under the Investment Advisors Act of 1940, as amended, is the managing member of GP V. By virtue of such relationships, GP V and OrbiMed Advisors may be deemed to have voting and investment power over the shares of common stock held by OPI V and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed Advisors exercises this investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership over the shares of common stock held by OPI V.

Each of OrbiMed Advisors, OrbiMed BioFund, OrbiMed Israel GP, OrbiMed Israel GP II, OrbiMed Israel II, GP V, GP VI, and Genesis GP disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of his or its pecuniary interest therein, if any. This report shall not be deemed an admission that any such person or entity is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

The Reporting Person was issued Restricted Stock Units ("RSUs"). Each RSU represents a contingent right to receive one share of Common Stock. The RSUs shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors. The RSUs may be settled only by delivering shares of Common Stock, and thus, the grant is being reported in Table I as allowed per SEC guidance.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

The Reporting Person was issued Restricted Stock Units ("RSUs"). Each RSU represents a contingent right to receive one share of Common Stock. The RSUs shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors. The RSUs may be settled only by delivering shares of Common Stock, and thus, the grant is being reported in Table I as allowed per SEC guidance.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

The Reporting Person was issued Restricted Stock Units ("RSUs"). Each RSU represents a contingent right to receive one share of Common Stock. The RSUs shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors. The RSUs may be settled only by delivering shares of Common Stock, and thus, the grant is being reported in Table I as allowed per SEC guidance.

The Reporting Person was issued Restricted Stock Units ("RSUs"). Each RSU represents a contingent right to receive one share of Common Stock. The RSUs shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors. The RSUs may be settled only by delivering shares of Common Stock, and thus, the grant is being reported in Table I as allowed per SEC guidance.

The Reporting Person was issued Restricted Stock Units ("RSUs"). Each RSU represents a contingent right to receive one share of Common Stock. The RSUs shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors. The RSUs may be settled only by delivering shares of Common Stock, and thus, the grant is being reported in Table I as allowed per SEC guidance.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

These shares shall vest in full on the earlier to occur of (i) the first anniversary of the grant date or (ii) the date of the next annual meeting of stockholders following the grant date, subject to the Reporting Person's continued service on the Issuer's board of directors.

These shares shall vest in thirty-six (36) equal monthly installments following April 17, 2025; provided, however, that all vesting shall cease if the Reporting Person resigns from the Issuer's Board of Directors or otherwise ceases to serve as a director of the Issuer.

25% of the shares subject to the stock option shall vest on December 7, 2025, and the remainder of the shares shall vest in equal monthly installments for a period of 36 months thereafter, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

1/48th of the shares shall vest on each of the next forty-eight (48) monthly anniversaries of the grant date, provided that the Reporting Person maintains a service relationship with the Issuer as of the applicable vesting dates.

Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting of restricted stock units and does not represent a sale by the Reporting Person.

Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting of restricted stock units and does not represent a sale by the Reporting Person.

Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting of restricted stock units and does not represent a sale by the Reporting Person.

Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting of restricted stock units and does not represent a sale by the Reporting Person.

Effective August 21, 2024, the Issuer's Board of Directors approved a rescission of the August 2023 stock option repricing for certain non-employee directors of the Issuer. All of the affected stock options have been reverted to their original exercise price as established at the time of the grant. Such transactions were exempt pursuant to Rule 16b-6(d) and Rule 16b-3 of the Exchange Act, as applicable.

The shares subject to this option are fully vested and exercisable as of the date hereof.