SPRO · Spero Therapeutics, Inc.

The shares underlying this option will vest and become exercisable in full on June 23, 2027 subject to the Reporting Person's continued service as a director through the vesting date.

The shares underlying this option will vest and become exercisable in full on June 23, 2027 subject to the Reporting Person's continued service as a director through the vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 23, 2027, subject to the Reporting Person's continued service through the applicable vesting date.

The shares underlying this option will vest and become exercisable in full on June 23, 2027 subject to the Reporting Person's continued service as a director through the vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 23, 2027, subject to the Reporting Person's continued service through the applicable vesting date.

The shares underlying this option will vest and become exercisable in full on June 23, 2027 subject to the Reporting Person's continued service as a director through the vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 23, 2027, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 23, 2027, subject to the Reporting Person's continued service through the applicable vesting date.

The shares underlying this option will vest and become exercisable in full on June 23, 2027 subject to the Reporting Person's continued service as a director through the vesting date.

The shares underlying this option will vest and become exercisable in full on June 23, 2027 subject to the Reporting Person's continued service as a director through the vesting date.

The shares underlying this option will vest and become exercisable in full on June 23, 2027 subject to the Reporting Person's continued service as a director through the vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 23, 2027, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 23, 2027, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 23, 2027, subject to the Reporting Person's continued service through the applicable vesting date.

Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of RSUs. The sale occurred automatically to satisfy the tax withholding obligations to be funded by a "sell to cover" transaction and does not represent a discretionary trade by the Reporting Person.

Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of RSUs. The sale occurred automatically to satisfy the tax withholding obligations to be funded by a "sell to cover" transaction and does not represent a discretionary trade by the Reporting Person.

Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of RSUs. The sale occurred automatically to satisfy the tax withholding obligations to be funded by a "sell to cover" transaction and does not represent a discretionary trade by the Reporting Person.

Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of RSUs. The sale occurred automatically to satisfy the tax withholding obligations to be funded by a "sell to cover" transaction and does not represent a discretionary trade by the Reporting Person.

Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of RSUs. The sale occurred automatically to satisfy the tax withholding obligations to be funded by a "sell to cover" transaction and does not represent a discretionary trade by the Reporting Person.

Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of RSUs. The sale occurred automatically to satisfy the tax withholding obligations to be funded by a "sell to cover" transaction and does not represent a discretionary trade by the Reporting Person.

Consists of restricted stock units ("RSUs") granted to Reporting Person under Issuer's 2017 Stock Incentive Plan. Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest in four equal annual installments beginning on February 2, 2027, subject to the Reporting Person's continued service through the applicable vesting date.

Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of RSUs. The sale occurred automatically to satisfy the tax withholding obligations to be funded by a "sell to cover" transaction and does not represent a discretionary trade by the Reporting Person.

The shares underlying this option vest as to 25% on February 2, 2027, with the remainder vesting in 36 equal monthly installments thereafter, subject to the Reporting Person's continued service through the applicable vesting date.

The shares underlying this option vest as to 25% on February 2, 2027, with the remainder vesting in 36 equal monthly installments thereafter, subject to the Reporting Person's continued service through the applicable vesting date.

Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of RSUs. The sale occurred automatically to satisfy the tax withholding obligations to be funded by a "sell to cover" transaction and does not represent a discretionary trade by the Reporting Person.

Consists of restricted stock units ("RSUs") granted to Reporting Person under Issuer's 2017 Stock Incentive Plan. Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest in four equal annual installments beginning on February 2, 2027, subject to the Reporting Person's continued service through the applicable vesting date.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of restricted stock units ("RSUs") that were granted to the Reporting Person on November 13, 2023.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of restricted stock unit ("RSUs") that were granted to the Reporting Person on August 26, 2021.

Amount includes 65,817 shares of common stock held by the Mahadevia-Mehta Family Trust, of which the Reporting Person is a trustee.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of restricted stock units ("RSUs") that were granted to the Reporting Person on August 26, 2021.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 12, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 12, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 12, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 12, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 12, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 12, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 12, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest on June 12, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

Amount includes 65,817 shares of common stock held by the Mahadevia-Mehta Family Trust, of which the Reporting Person is a trustee.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest in four equal annual installments beginning on May 2, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of RSUs that were granted to the Reporting Person on February 1, 2023.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of RSUs that were granted to the Reporting Person on February 1, 2024.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of RSUs that were granted to the Reporting Person on February 1, 2023.

Amount includes 65,817 shares of common stock held by the Mahadevia-Mehta Family Trust, of which the Reporting Person is a trustee.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of RSUs that were granted to the Reporting Person on February 1, 2024.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of RSUs that were granted to the Reporting Person on February 1, 2022.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of RSUs that were granted to the Reporting Person on February 1, 2022.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of RSUs that were granted to the Reporting Person on February 1, 2022.

Amount includes 65,817 shares of common stock held by the Mahadevia-Mehta Family Trust, of which the Reporting Person is a trustee.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of RSUs that were granted to the Reporting Person on February 1, 2024.

The reported transaction is a sale of common stock effected to cover tax withholding obligations pursuant to a "sell to cover" provision included in each RSU Agreement in connection with the vesting of RSUs that were granted to the Reporting Person on February 1, 2023.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest in four equal annual installments beginning on February 3, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

Each RSU represents the right to receive one share of common stock upon vesting. The RSUs shall vest in full on February 3, 2026, subject to the Reporting Person's continued service through the applicable vesting date.

Consists of restricted stock units ("RSUs"). Each RSU represents the right to receive one share of common stock upon vesting. The RSUs vest in four equal annual installments beginning on February 3, 2026, subject to the Reporting Person's continued service through the applicable vesting date.