PTGX · Protagonist Therapeutics, Inc

The transactions set forth on this Form 4 were effected pursuant to a 10b5-1 plan adopted by the reporting person on February 27, 2026.

The price reported represents the weighted average sale price per share. The shares were sold in multiple transactions at prices ranging from $117.00 to $119.07. Upon request by the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price.

These stock options are fully vested.

The transactions set forth on this Form 4 were effected pursuant to a 10b5-1 plan adopted by the reporting person on February 27, 2026.

These stock options are fully vested.

The price reported represents the weighted average sale price per share. The shares were sold in multiple transactions at prices ranging from $107.02 to $108.00. Upon request by the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price.

The transactions set forth on this Form 4 were effected pursuant to a 10b5-1 plan adopted by the reporting person on February 27, 2026.

These stock options are fully vested.

The transactions set forth on this Form 4 were effected pursuant to a 10b5-1 plan adopted by the reporting person on February 27, 2026.

These stock options are fully vested.

The price reported represents the weighted average sale price per share. The shares were sold in multiple transactions at prices ranging from $98.83 to $103.50. Upon request by the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price.

These stock options are fully vested and will expire on October 11, 2026.

This Form 4 Amendment is being filed to clarify that the transactions set forth on this Form 4 were effected pursuant to a 10b5-1 plan adopted by the reporting person on January 30, 2026 and to check the appropriate box which appeared unchecked on the original Form 4 filing.

These stock options are fully vested.

Reflects 10,000 shares of common stock that were previously held directly by the Reporting Person and which were transferred to the Bryan & Courtney Giraudo Trust.

The price reported represents the weighted average sale price per share. The shares were sold in multiple transactions at prices ranging from $98.69 to $104.67. Upon request by the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price.

Reflects 10,000 shares of common stock that were previously held directly by the Reporting Person and which were transferred to the Bryan & Courtney Giraudo Trust.

These stock options are fully vested.

This transaction involves a bona fide gift of securities from the Reporting Person to family and friends.

Sale of shares to cover tax withholding obligation incurred upon settlement of restricted stock units.

Includes an aggregate of 433 shares acquired by the Reporting Person under the Issuer's 2016 Employee Stock Purchase Plan on March 9, 2026.

The price reported represents the weighted average sale price per share. The shares were sold in multiple transactions at prices ranging from $103.99 to $105.54. Upon request by the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price.

These stock options are fully vested.

The stock option was granted to the Reporting Person on April 18, 2022, one quarter vested on April 18, 2023 and the remaining three quarters vest in equal monthly installments through April 18, 2026, subject to the Reporting Person's continued service to the Issuer.

The price reported represents the weighted average sale price per share. The shares were sold in multiple transactions at prices ranging from $104.00 to $104.465. Upon request by the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price.

The stock option was granted to the Reporting Person on November 7, 2022, one quarter vested on November 7, 2023 and the remaining three quarters vest in equal monthly installments through November 7, 2026, subject to the Reporting Person's continuous service to the Issuer.

The stock option was granted to the Reporting Person on January 16, 2023 and vests in 48 equal monthly installments following the date of grant, subject to the Reporting Person's continued service to the Issuer.

These stock options are fully vested.

These stock options are fully vested.

This transaction involves a bona fide gift of securities from the Reporting Person to relatives.

Includes an aggregate of 433 shares acquired by the Reporting Person under the Issuer's 2016 Employee Stock Purchase Plan on March 9, 2026.

The price reported represents the weighted average sale price per share. The shares were sold in multiple transactions at prices ranging from $81.47 to $83.12. Upon request by the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price.

These stock options are fully vested.

These stock options are fully vested.

The price reported represents the weighted average sale price per share. The shares were sold in multiple transactions at prices ranging from $83.65 to $83.87. Upon request by the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price.