PHAT · Phathom Pharmaceuticals, Inc.

Represents shares underlying the restricted stock units that were surrendered by the reporting person to the Issuer in satisfaction of the Issuer's tax withholding obligation.

Reflects shares transferred for no consideration to a trust for the benefit of the Reporting Person's spouse and for which the Reporting Person serves as trustee.

The Restricted Stock Units ("RSUs") were granted on May 19, 2026, pursuant to the Issuer's Non-Employee Director Compensation Program. 100% of the total number of RSUs granted shall vest on the first to occur of (A) the first anniversary of the date of grant or (B) the next occurring annual meeting of the Issuer's stockholders, subject to the Reporting Person's continuing service on the Board through such vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

The Restricted Stock Units ("RSUs") were granted on May 19, 2026, pursuant to the Issuer's Non-Employee Director Compensation Program. 100% of the total number of RSUs granted shall vest on the first to occur of (A) the first anniversary of the date of grant or (B) the next occurring annual meeting of the Issuer's stockholders, subject to the Reporting Person's continuing service on the Board through such vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

The Restricted Stock Units ("RSUs") were granted on May 19, 2026, pursuant to the Issuer's Non-Employee Director Compensation Program. 100% of the total number of RSUs granted shall vest on the first to occur of (A) the first anniversary of the date of grant or (B) the next occurring annual meeting of the Issuer's stockholders, subject to the Reporting Person's continuing service on the Board through such vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

The Restricted Stock Units ("RSUs") were granted on May 19, 2026, pursuant to the Issuer's Non-Employee Director Compensation Program. 100% of the total number of RSUs granted shall vest on the first to occur of (A) the first anniversary of the date of grant or (B) the next occurring annual meeting of the Issuer's stockholders, subject to the Reporting Person's continuing service on the Board through such vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

The Restricted Stock Units ("RSUs") were granted on May 19, 2026, pursuant to the Issuer's Non-Employee Director Compensation Program. 100% of the total number of RSUs granted shall vest on the first to occur of (A) the first anniversary of the date of grant or (B) the next occurring annual meeting of the Issuer's stockholders, subject to the Reporting Person's continuing service on the Board through such vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

The Restricted Stock Units ("RSUs") were granted on May 19, 2026, pursuant to the Issuer's Non-Employee Director Compensation Program. 100% of the total number of RSUs granted shall vest on the first to occur of (A) the first anniversary of the date of grant or (B) the next occurring annual meeting of the Issuer's stockholders, subject to the Reporting Person's continuing service on the Board through such vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

The Restricted Stock Units ("RSUs") were granted on May 19, 2026, pursuant to the Issuer's Non-Employee Director Compensation Program. 100% of the total number of RSUs granted shall vest on the first to occur of (A) the first anniversary of the date of grant or (B) the next occurring annual meeting of the Issuer's stockholders, subject to the Reporting Person's continuing service on the Board through such vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

Reflects shares transferred for no consideration to a trust for the benefit of the Reporting Person's spouse and for which the Reporting Person serves as trustee.

Represents shares underlying the performance stock units that were surrendered by the reporting person to the Issuer in satisfaction of the Issuer's tax withholding obligation.

Represents shares underlying RSUs that were surrendered by the reporting person to the Issuer upon vesting of such RSU in satisfaction of the Issuer's tax withholding obligation.

Represents shares issued upon vesting of performance stock units granted to the reporting person on February 27, 2025 based on the achievement of performance criteria determined to be satisfied on February 27, 2026.

Represents restricted stock units ("RSUs") granted on February 27, 2026. 1/3 of the total number of RSUs granted vest on each of the first three anniversaries of February 27, 2026, the vesting commencement date, subject to the Reporting Person's continued service through each vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

Represents shares issued upon vesting of performance stock units granted to the reporting person on June 23, 2025 based on the achievement of performance criteria determined to be satisfied on February 10, 2026.

Includes 1,722 shares acquired under the Phathom Pharmaceuticals, Inc. employee stock purchase plan in January 2026.

Represents shares underlying the performance stock units that were surrendered by the reporting person to the Issuer in satisfaction of the Issuer's tax withholding obligation.

Represents shares issued upon vesting of performance stock units granted to the reporting person on April 3, 2025 based on the achievement of performance criteria determined to be satisfied on February 10, 2026.

Includes 2,410 shares acquired under the Phathom Pharmaceuticals, Inc. employee stock purchase plan in January 2026.

Represents shares underlying the performance stock units that were surrendered by the reporting person to the Issuer in satisfaction of the Issuer's tax withholding obligation.

Reflects shares transferred for no consideration to a trust for the benefit of the Reporting Person's spouse and for which the Reporting Person serves as trustee.

The shares are subject to a lock-up agreement entered into by the Reporting Person in connection with the underwriting agreement dated January 7, 2026 (the Lock-Up Agreement). The trust has agreed in writing to be bound by the same terms described in the Lock-Up Agreement to the extent and for the duration that such terms remain in effect at the time of the transfer.

Represents shares underlying the restricted stock units that were surrendered by the reporting person to the Issuer in satisfaction of the Issuer's tax withholding obligation.

1/48th of the total number of shares of common stock subject to the option vest monthly following the Vesting Commencement Date, subject to the Reporting Person's continuous service to the Issuer through each vesting date.

Represents restricted stock units ("RSUs") granted on January 2, 2026. 1/3 of the total number of RSUs granted vest on each of the first three anniversaries of January 2, 2026, the vesting commencement date (the "Vesting Commencement Date"), subject to the Reporting Person's continued service through each vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

Represents restricted stock units ("RSUs") granted on January 2, 2026. 1/3 of the total number of RSUs granted vest on each of the first three anniversaries of January 2, 2026, the vesting commencement date (the "Vesting Commencement Date"), subject to the Reporting Person's continued service through each vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

1/48th of the total number of shares of common stock subject to the option vest monthly following the Vesting Commencement Date, subject to the Reporting Person's continuous service to the Issuer through each vesting date.

Represents restricted stock units ("RSUs") granted on January 2, 2026. 1/3 of the total number of RSUs granted vest on each of the first three anniversaries of January 2, 2026, the vesting commencement date (the "Vesting Commencement Date"), subject to the Reporting Person's continued service through each vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

1/48th of the total number of shares of common stock subject to the option vest monthly following the Vesting Commencement Date, subject to the Reporting Person's continuous service to the Issuer through each vesting date.

Represents shares underlying the restricted stock units that were surrendered by the reporting person to the Issuer in satisfaction of the Issuer's tax withholding obligation.

Represents shares underlying the performance stock units that were surrendered by the reporting person to the Issuer in satisfaction of the Issuer's tax withholding obligation.

Represents shares issued upon vesting of performance stock units granted to the reporting person on April 3, 2025 based on the achievement of performance criteria determined to be satisfied on December 17, 2025.

Represents shares underlying the performance stock units that were surrendered by the reporting person to the Issuer in satisfaction of the Issuer's tax withholding obligation.

Represents shares issued upon vesting of performance stock units granted to the reporting person on June 23, 2025 based on the achievement of performance criteria determined to be satisfied on December 17, 2025.

Represents shares underlying the performance stock units that were surrendered by the reporting person to the Issuer in satisfaction of the Issuer's tax withholding obligation.

Each performance stock unit represents a contingent right to receive one share of common stock of the Issuer.

On April 3, 2025, the reporting person was granted 360,000 performance stock units, of which 90,000 vested on September 25, 2025 and an additional 90,000 vested on November 28, 2025, in each case due to the achievement of the applicable stock price hurdle. The remaining performance stock units will vest based on the achievement of stock price hurdles over a period of four years following the grant date, subject to the reporting person's continued service through the date each such stock price hurdle is achieved.

Represents shares sold to satisfy tax withholding obligations upon the settlement of restricted stock units.

Represents restricted stock units ("RSUs") granted on October 6, 2025. One third (1/3) of the total number of RSUs granted vest on each of the first three anniversaries of October 6, 2025, the vesting commencement date, subject to the Reporting Person's continued service on the applicable vesting date. Each RSU represents a contingent right to receive one share of common stock of the Issuer.

This amendment is being filed to report the transaction which was inadvertently omitted in the Form 4 filed on behalf of the Reporting Person on October 7, 2025.

The stock option will vest with respect to 25% of the shares of common stock on October 6, 2026, and will vest with respect to the remaining shares in equal monthly installments over the following three years, subject to the Reporting Person's continuous service to the Issuer on the applicable vesting dates.

Each performance stock unit represents a contingent right to receive one share of common stock of the Issuer.

On April 3, 2025, the reporting person was granted 360,000 performance stock units, of which 90,000 vested on September 25, 2025 due to the achievement of the applicable stock price hurdle. The remaining performance stock units will vest based on the achievement of stock price hurdles over a period of four years following the grant date, subject to the reporting person's continued service through the date each such stock price hurdle is achieved.

Represents shares underlying the performance stock units that were surrendered by the reporting person to the Issuer in satisfaction of the Issuer's tax withholding obligation.

Represents shares sold to satisfy tax withholding obligations upon the settlement of restricted stock units.