Spero Therapeutics, Inc.

What they do

Spero has no approved products of its own and historically generated no product sales revenue. Its legacy asset, tebipenem (Utebzi), was exclusively licensed to GSK in September 2022, with the IND and NDA ownership transferred to GSK; Spero is entitled to potential milestones and royalties. After ceasing SPR206 (March 2025) and SPR720 (November 2025), Spero in July 2026 licensed SP001, a third-generation anti-CD40L antibody, from Innovent Biologics for worldwide rights excluding Greater China. SP001 is Phase 2-ready and being targeted at IgG4-related disease.

Revenue drivers

• Utebzi (tebipenem pivoxil) royalties and milestones from GSK — Spero licensed tebipenem to GSK in 2022; FDA approved Utebzi in June 2026 for cUTI, and GSK holds U.S. and Europe commercialization rights. Spero receives potential milestone and royalty payments, a portion of which is now owed to HealthCare Royalty Partners, with Spero retaining a 35% interest in GSK Proceeds after required payments under the July 2026 financing.
• Annual revenue recognized to date — Reported annual revenue was $3.1M (2021), $2.5M (2022), $933K (2023), $371K (2024) and $12.6M (2025) — lumpy and consistent with milestone/collaboration revenue rather than product sales. Recent quarters were $0.00 for 2025-09-30, 2026-03-31 and 2026-06-30, with $12.6M in 2025-12-31.
• SP001 (anti-CD40L antibody) — Licensed from Innovent Biologics in July 2026, SP001 is expected to be Spero's lead program and the primary use of the July 2026 royalty financing proceeds. No revenue is currently generated; management plans a Phase 2 study in IgG4-related disease, and Innovent retains rights in Greater China.

Recent performance

Spero reported $0.00 revenue for the quarters ended March 31, 2026 and June 30, 2026. Full-year 2025 revenue was $12.6M with net income of $8.6M and diluted EPS of $0.15, driven by non-recurring items rather than product sales. At June 30, 2026, total assets were $52.8M, total liabilities $8.6M, shareholder equity $44.2M, and cash and equivalents $50.8M. Accumulated deficit as of June 30, 2026 was $467.8M, and operating cash flow has been negative every year shown, including -$12.6M in 2025. In July 2026, Spero closed a $105 million non-recourse, non-dilutive royalty financing with HealthCare Royalty Partners (KKR).

Strategy

Following the March 2025 termination of SPR206 and November 2025 termination of SPR720, Spero has repositioned around immunology and inflammation. Its stated priority is advancing SP001 into a Phase 2 study in IgG4-related disease and evaluating additional immune-mediated disease opportunities to broaden SP001. The company continues to support GSK in the Utebzi approval and commercialization process under the GSK License Agreement. The $105 million royalty financing proceeds are intended primarily to fund SP001, and management says the funding plus the July 2026 transaction extends its cash runway into the second half of 2029. Debra Zack, M.D., Ph.D., a board-certified rheumatologist, was appointed Chief Medical Officer in July 2026 to oversee clinical development.

Risks

• Dependence on GSK for tebipenem economics — Because Spero transferred the tebipenem IND and NDA to GSK and holds only milestone and royalty rights, its cash flows from Utebzi depend entirely on GSK's commercialization execution and on payments that may be delayed, reduced or never realized.
• Pivoted pipeline with no company-generated clinical data for SP001 — Spero ceased SPR206 and SPR720 and licensed SP001 from Innovent in July 2026; the Phase 1 and Phase 1b experience cited for SP001 was generated by Innovent, not Spero, and Spero has not yet begun its own Phase 2 study.
• Obligations and retained 35% interest under the royalty financing — The July 2026 $105 million financing assigns to HealthCare Royalty Partners a portion of future GSK proceeds, so Spero retains only a 35% interest after required NPA payments, reducing the economic upside from Utebzi.
• History of losses and need for additional capital — Spero had a $467.8M accumulated deficit at June 30, 2026 and negative operating cash flow every year shown; management states it will need additional funding beyond its current runway into the second half of 2029 or if it changes its operating plan.

Outlook

Management says its priorities for the remainder of 2026 are advancing SP001 toward a Phase 2 study in IgG4-related disease and evaluating additional immune-mediated disease opportunities. GSK is expected to make Utebzi available to U.S. patients by the end of 2026. Spero states that cash and equivalents at June 30, 2026 plus July 2026 royalty financing net proceeds, offset by the Innovent upfront payment, fund operations into the second half of 2029.