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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.
Spero Therapeutics (SPRO) reported a strong clinical milestone and narrower losses in the quarter ended June 30, 2025. The pivotal Phase 3 PIVOT-PO trial for tebipenem HBr met its primary endpoint and was stopped early for efficacy after a pre-specified interim analysis of 1,690 patients, and the company has shifted its R&D focus to tebipenem while suspending SPR720 oral development and discontinuing SPR206.
Financially, total revenues were $14.2 million for the quarter and $20.1 million for the six months, driven by related-party collaboration revenue and grant revenue. Net loss improved to $1.7 million for the quarter ($0.03 per share) and $15.6 million for six months ($0.28 per share), compared with larger losses a year earlier. Cash and cash equivalents were $31.2 million at June 30, 2025, down from $52.9 million at year-end, and the company used $21.7 million of cash in operations in the six months. The company received significant upfront and milestone payments from GSK (including a $66.0 million upfront payment) and reports committed BARDA funding of $65.6 million (with $61.1 million recognized to date). The company disclosed an SEC Wells Notice and ongoing cooperation with the staff, and regained Nasdaq bid-price compliance on June 12, 2025.
Spero Therapeutics announced it issued a press release reporting results for the third quarter ended June 30, 2025. The 8-K furnishes that press release as Exhibit 99.1, but the filing itself does not include the underlying financial figures in-line.
The company also furnished an investor presentation as Exhibit 99.2, which management intends to use in investor communications and is available on the company website. Both the press release and presentation are described as "furnished" and are not deemed "filed" for purposes of certain securities-law liabilities.
Spero Therapeutics’ Form 8-K details the voting results of its 12 June 2025 Annual Meeting. A quorum of 40,015,633 shares (71.57%) of the 55.9 million shares outstanding was present.
Board elections: Class II directors Frank E. Thomas, Patrick Vink M.D., and Esther Rajavelu were re-elected through 2028, each receiving roughly 25.7 million votes for and 0.4-2.9 million votes withheld; 13.8 million broker non-votes were recorded.
Auditor ratification: PricewaterhouseCoopers LLP was confirmed as independent auditor for FY 2025 with an overwhelming 39.8 million ‘for’ versus 175 k ‘against’.
Say-on-pay: Executive compensation received shareholder support—25.18 million ‘for’ (96.0%) against 0.64 million ‘against’.
Equity plan amendment: Shareholders approved increasing the 2017 Stock Incentive Plan by 3 million additional shares (22.97 million for / 3.15 million against). This authorizes extra equity that may dilute existing holders once issued but expands flexibility to attract and retain talent.
No financial performance data, earnings guidance, or major strategic transactions were disclosed; the filing is limited to governance and compensation matters.