Welcome to our dedicated page for Spero Therapeuti SEC filings (Ticker: SPRO), a comprehensive resource for investors and traders seeking official regulatory documents including 10-K annual reports, 10-Q quarterly earnings, 8-K material events, and insider trading forms.
Spero Therapeutics, Inc. filings document the regulatory record of a Nasdaq-listed clinical-stage biopharmaceutical company developing treatments for rare diseases and multi-drug resistant bacterial infections. Form 8-K reports cover operating results, Regulation FD investor presentations, tebipenem HBr business updates, compensatory arrangements, board changes, and other material events.
Proxy materials describe director elections, annual meeting votes, executive compensation, board committees, and stock incentive plan matters. The filing record also identifies the company’s common stock, par value and exchange listing, and records governance and regulatory matters including the reported conclusion of a previously disclosed SEC investigation without a recommended enforcement action.
Spero Therapeutics Chief Operating Officer Timothy Keutzer reported new equity awards and related tax sales of common stock. On February 2, 2026, he received 68,000 restricted stock units that vest in four equal annual installments beginning February 2, 2027, contingent on continued service. He also received a stock option for 137,000 shares at $2.23 per share, vesting 25% on February 2, 2027, with the rest vesting in 36 monthly installments.
To cover tax withholding from RSU vesting, Keutzer had automatic “sell to cover” transactions of 18,891 shares at $2.20, 24,224 shares at $2.14, and 3,471 shares at $2.24, which the filing states were not discretionary trades. After these transactions, he directly owned 761,158 shares of common stock and 137,000 stock options.
Spero Therapeutics officer Esther Rajavelu reported new equity awards and a small tax-related share sale. On February 2, 2026, she received 249,000 RSUs that vest in four equal annual installments starting February 2, 2027, and a stock option for 498,000 shares at an exercise price of $2.23, vesting 25% on February 2, 2027 and monthly thereafter.
To cover tax withholding from RSU vesting, 18,442 common shares were automatically sold at $2.20 in a non-discretionary “sell to cover” transaction. After these transactions, she directly held 1,100,008 common shares and 498,000 stock options.
Spero Therapeutics reported two corporate updates. First, Ankit Mahadevia, MD, resigned from the Board of Directors, its Development Committee, and all officer and director roles at subsidiaries effective January 30, 2026, citing other professional commitments and no disagreements with the company or Board. The company plans to enter into a consulting agreement so he can continue supporting management.
Second, on January 20, 2026, Spero received a letter from the U.S. Securities and Exchange Commission stating the SEC has concluded its investigation and, based on information as of that date, does not intend to recommend an enforcement action against the company. The investigation had been previously disclosed in Spero’s periodic reports.
Spero Therapeutics (SPRO) furnished materials related to its third-quarter update. The company provided a press release announcing results for the quarter ended September 30, 2025 and an investor presentation, both dated November 13, 2025.
The materials are furnished, not filed, which limits their legal exposure under the Exchange Act and Securities Act. The investor presentation is available on the company’s investor relations website.
Spero Therapeutics’ latest quarterly report shows a narrower loss and a sharper focus on its lead antibiotic candidate tebipenem HBr. For the quarter ended September 30, 2025, total revenue was $5.4 million, down from $13.5 million a year earlier as grant and collaboration revenue declined. Net loss improved to $7.4 million from $17.1 million, helped by lower research and development spending and collaboration milestone receipts.
At September 30, 2025, Spero held $48.6 million in cash and cash equivalents and stockholders’ equity of $26.5 million. Management believes this cash, combined with lower clinical spending after completing the pivotal PIVOT-PO trial, will fund operations for at least 12 months, but additional capital will be needed to carry products through approval and commercialization.
Strategically, Spero has ceased development of SPR206 and SPR720 and is now heavily dependent on tebipenem HBr and its license partnership with GSK. The PIVOT-PO Phase 3 trial in complicated urinary tract infections met its primary endpoint and was stopped early for efficacy, and GSK plans to file with the FDA in the fourth quarter of 2025. Key risks highlighted include continued operating losses, dependence on milestone and grant payments, manufacturing and regulatory uncertainties, stock price volatility, prior Nasdaq listing issues, and an ongoing SEC Wells Notice process related to the company’s 2022 tebipenem disclosures.
Spero Therapeutics (SPRO) reported an insider transaction on a Form 4. On 11/07/2025, a company executive sold 40,270 shares of common stock at $2.37 per share. The filing states this was a sell-to-cover to satisfy tax withholding upon the vesting of RSUs granted on November 13, 2023. Following the transaction, the executive beneficially owned 869,450 shares, held directly.
Spero Therapeutics director Ankit Mahadevia sold 6,572 shares of common stock on 08/28/2025 at $1.97 per share to satisfy tax withholding for RSUs that vested from a grant dated 08/26/2021. After the sale, the reporting person beneficially owns 703,294 shares, which includes 65,817 shares held by the Mahadevia-Mehta Family Trust where he is a trustee. The Form 4 was signed by an attorney-in-fact on 09/02/2025.
Timothy Keutzer, Chief Operating Officer of Spero Therapeutics (SPRO), reported a sale of company common stock on 08/28/2025. The filing shows 1,695 shares were sold at $1.97 per share under a "sell to cover" provision tied to RSU vesting granted on August 26, 2021, and the sale was executed to satisfy tax withholding obligations. After the transaction, the reporting person beneficially owned 739,744 shares directly. The Form 4 was signed by an attorney-in-fact on behalf of Mr. Keutzer on 09/02/2025.
Anson-managed entities reported beneficial ownership of 1,615,469 shares of Spero Therapeutics common stock, representing 2.9% of the 55,910,641 shares outstanding. The holdings are disclosed on a Schedule 13G/A dated for the event 06/30/2025 and signed on 08/14/2025 by representatives of Anson Funds Management LP, Anson Management GP LLC, Anson Advisors Inc., Tony Moore, Amin Nathoo and Moez Kassam.
The filing states the shares are held by the Fund and that the position is held in the ordinary course of business and not to influence control of the issuer. Voting and dispositive power over the 1,615,469 shares is shown as shared (no sole power reported). The filing cites the issuer's outstanding share count from the issuer's May 13, 2025 quarterly report.
Spero Therapeutics registered an additional 3,000,000 shares of common stock under its 2017 Stock Incentive Plan, as amended, representing an increase in shares reserved for employee awards. The registration statement incorporates by reference prior Form S-8 filings for the same plan and includes key exhibits such as the amended plan, forms of award agreements, counsel opinion and the independent auditor's consent.