Spero Therapeutics SEC filings document the regulatory record of a clinical-stage biopharmaceutical company focused on immunology and inflammation. The filings identify SPRO common stock as listed on the Nasdaq Global Select Market and show the company’s headquarters in Cambridge, Massachusetts.
Quarterly reports on Form 10-Q provide Spero’s financial statements and notes, including disclosures on share-based compensation plans and at-the-market offering activity when applicable. Current reports on Form 8-K have covered operating results, license agreements, FDA approval disclosures for Utebzi, equity plan approvals, charter amendments, shelf registration activity and at-the-market sale agreements.
Spero’s DEF 14A proxy statement is relevant for governance matters submitted to stockholders, including equity plan information and annual meeting voting items. Registration-related filings and prospectus materials are also important because the company has used shelf registration and at-the-market structures to describe potential securities offerings.
Spero Therapeutics, Inc. (SPRO) entered into an Open Market Sale Agreement with Jefferies LLC on August 28, 2026, establishing an at-the-market equity program. Once its new Form S-3 universal shelf registration statement for up to $300,000,000 of securities is declared effective, the company may sell up to $100,000,000 of common stock through Jefferies under this agreement.
Sales, if any, will be made as at-the-market offerings, with Jefferies earning up to 3.0% of aggregate gross proceeds as sales agent. On the same date, Spero terminated its prior Cantor Fitzgerald Controlled Equity Offering Sales Agreement, which had allowed up to $75,000,000 of sales; no shares were sold under that program in 2024 or 2025 and no termination penalties were incurred.
Spero Therapeutics, Inc. (SPRO) filed a shelf registration to offer, from time to time, up to $300,000,000 of debt securities, common stock, preferred stock, depositary shares, subscription rights, units and warrants. This includes $100,000,000 of common stock that may be sold under a separate sales agreement prospectus.
Spero is a clinical-stage biopharmaceutical company developing next-generation medicines for immune-mediated diseases. Its lead program, SP001, is a fully humanized Fc-silent anti-CD40L monoclonal antibody, in development for Immunoglobulin G4 related disease, licensed from Innovent Biologics under a July 8, 2026 agreement.
Net proceeds from any offerings may be used for general corporate purposes, including research and development, preclinical and clinical work, in-licensing or acquisitions, debt repayment or refinancing, working capital and capital expenditures.
Spero Therapeutics reported second quarter 2026 results and provided a business update. The company highlighted three key milestones: U.S. FDA approval of Utebzi (tebipenem pivoxil), advancement of its new immunology program SP001 toward Phase 2, and a $105 million non-recourse, non-dilutive royalty financing.
For the quarter ended June 30, 2026, Spero reported no revenues, compared with $14.2 million in total revenues in the same quarter of 2025, reflecting the absence of prior grant and related-party collaboration revenue. Operating expenses were $9.9 million, versus $16.6 million a year earlier, driven by lower research and development spending.
Net loss for the quarter was $9.6 million (basic and diluted net loss per share of $0.16), compared with a net loss of $1.7 million (per share $0.03) in the prior-year quarter. As of June 30, 2026, cash and cash equivalents totaled $50.8 million, up from $40.3 million at December 31, 2025. Total assets were $52.8 million and stockholders’ equity was $44.2 million. The company continues to position SP001, a third-generation Fc-silent anti-CD40L monoclonal antibody, for development in IgG4-related and other immune-mediated diseases.
Spero Therapeutics, Inc. reported that for the three months ended June 30, 2026, total revenue was $0, down from $14.2 million a year earlier as prior-period BARDA grant and GSK collaboration revenue wound down. Operating expenses fell to $9.9 million from $16.6 million, but the absence of revenue drove a higher net loss of $9.6 million versus $1.7 million in the prior-year quarter.
For the six months ended June 30, 2026, the company recorded $16.8 million in net loss compared with $15.6 million a year earlier. Cash, cash equivalents and restricted cash were $50.8 million at June 30, 2026, up from $31.2 million a year before, supported by positive operating cash flow of $10.5 million in the first half of 2026.
The business has pivoted from tebipenem pivoxil to immunology, with lead program SP001, a fully humanized Fc-silent IgG1 antibody targeting CD40L, in development for IgG4-related disease. In June 2026, the FDA approved GSK’s NDA resubmission for Utebzi, triggering future milestone and royalty potential under the GSK license. Subsequent to quarter-end, Spero entered a $105.0 million royalty financing with affiliates of HCRx backed by a portion of future GSK payments and licensed SP001 globally (outside Greater China) from Innovent. Management states that existing cash plus royalty financing proceeds are expected to fund operations for at least 12 months from the issuance date.
Spero Therapeutics, Inc. reported that Chief Medical Officer Debra Zack received two equity awards on August 3, 2026. She was granted 162,311 RSUs under the 2019 Stock Incentive Plan, vesting in four equal annual installments beginning August 3, 2027, and stock options for 324,675 shares of common stock at an exercise price of $1.5400 per share, vesting 25% on August 3, 2027 with the remainder vesting in 36 equal monthly installments, all subject to continued service. The filing indicates these transactions were made pursuant to a Rule 10b5-1 trading plan.
Spero Therapeutics, Inc. filed an initial insider ownership report for Debra Zack, who serves as Chief Medical Officer. The report shows no equity transactions, acquisitions, or dispositions, and includes no current holdings or derivative positions, so no reportable beneficial ownership in Spero Therapeutics securities is disclosed for this officer in this filing.
Spero Therapeutics entered an exclusive license with Innovent Biologics for SP001, a third-generation Fc-silent anti-CD40L monoclonal antibody. Spero receives a worldwide license outside mainland China, Hong Kong, Macau and Taiwan and grants Innovent exclusive rights in that territory. Spero will pay Innovent a $35.0 million upfront fee, up to approximately $1.05 billion in development, regulatory and commercial milestones, and tiered royalties on net sales, and has agreed to file a U.S. IND for a Licensed Product within 12 months and use commercially reasonable efforts to develop and commercialize at least one indication in major markets.
On July 8, 2026, Spero also completed a non-recourse royalty financing tied to tebipenem HBr (Utebzi) economics under its GSK license. A special-purpose subsidiary issued senior secured notes with $105,000,000 aggregate principal, a 10% annual interest rate and nine-year maturity, subject to a $3,150,000 original issue discount, payable primarily from GSK milestone and royalty payments. A related agreement sold 65% of GSK milestone and royalty proceeds arising after repayment of the notes for $1,575,000, with Spero retaining 35%. The company estimates that net proceeds from this royalty financing, together with existing cash and cash equivalents, will fund operations into the second half of 2029.
SP001 (IBI355) has completed two Phase 1 studies in healthy volunteers and a Phase 1b multiple-ascending-dose trial in Sjögren’s disease, showing a generally benign safety profile and signals of disease-activity improvement. Spero currently expects to initiate a Phase 2 trial in IgG4-related disease in the second quarter of 2027, while Innovent plans a Phase 2 trial in Sjögren’s disease in China by early 2027, with potential expansion of SP001 into additional autoimmune and inflammatory indications.
Spero Therapeutics director Milind Deshpande received new equity awards as part of his compensation. He was granted 10,000 restricted stock units, each representing one share of common stock upon vesting, and a stock option for 20,000 shares at an exercise price of $2.15 per share.
The RSUs vest on June 23, 2027, contingent on his continued service. The option also vests and becomes fully exercisable on June 23, 2027 under the same service condition. Following the grant, he directly holds 101,454 shares of common stock.
Spero Therapeutics director Kathleen Tregoning received new equity awards. She was granted 10,000 restricted stock units, each convertible into one share of common stock upon vesting on June 23, 2027, subject to her continued service.
She also received stock options for 20,000 shares of common stock at an exercise price of $2.1500 per share, vesting in full on June 23, 2027 and expiring on June 23, 2036. Following these awards, she directly holds 85,000 shares of common stock.