Spero Therapeutics, Inc. filed a Form S-8 registration statement with the U.S. Securities and Exchange Commission on October 28, 2026, to register 1,950,000 additional shares of common stock reserved under its Amended and Restated 2019 Inducement Equity Incentive Plan.

Key Highlights

  • Shares registered: 1,950,000 additional shares of common stock reserved under the Amended and Restated 2019 Inducement Equity Incentive Plan.
  • Plan name: The filing covers the Spero Therapeutics, Inc. Amended and Restated 2019 Inducement Equity Incentive Plan.
  • Agent for service: Esther Rajavelu, serving as President, Chief Executive Officer, Chief Financial Officer, and Treasurer.
  • Prior S-8 filings incorporated by reference: Six previously effective Form S-8 registration statements, with file numbers ranging from 333-230283 to 333-277984, are incorporated by reference.
  • Filer classification: The registrant identified itself as a non-accelerated filer and a smaller reporting company.
  • Legal opinion: Wilmer Cutler Pickering Hale and Dorr LLP provided the opinion of counsel filed as Exhibit 5.1.

Spero Therapeutics Adds Shares to 2019 Inducement Equity Plan

According to the filing, Spero Therapeutics, Inc. (NASDAQ:SPRO) submitted a Form S-8 registration statement on October 28, 2026, to register 1,950,000 additional shares of common stock. The registration statement disclosed that these shares are reserved under the company's Amended and Restated 2019 Inducement Equity Incentive Plan and represent "additional securities of the same class as other securities for which a registration statement filed on Form S-8 relating to an employee benefit plan is effective."

The filing incorporated by reference the contents of six prior Form S-8 registration statements filed with the SEC on March 14, 2019 (File No. 333-230283), August 6, 2020 (File No. 333-241681), March 30, 2023 (File No. 333-271000), August 10, 2023 (File No. 333-273880), November 13, 2023 (File No. 333-275515), and March 15, 2024 (File No. 333-277984), excluding Item 8 (Exhibits) in each case. The registration statement was filed pursuant to General Instruction E of Form S-8.

Exhibits filed with the registration statement include the legal opinion of Wilmer Cutler Pickering Hale and Dorr LLP (Exhibit 5.1), the consent of independent registered public accounting firm PricewaterhouseCoopers LLP (Exhibit 23.2), and the Amended and Restated 2019 Inducement Equity Incentive Plan itself (Exhibit 99.1). The registration statement was signed by Esther Rajavelu in her capacity as Principal Executive, Financial, and Accounting Officer, along with board Chairman Frank E. Thomas and six directors.

What Was Disclosed

Spero Therapeutics filed a Form S-8 on October 28, 2026, registering 1,950,000 additional common shares reserved under its Amended and Restated 2019 Inducement Equity Incentive Plan, incorporating by reference six prior S-8 filings and filing related exhibits including a legal opinion and auditor consent.