Spero Therapeutics is a clinical-stage biopharmaceutical company focused on a single drug candidate: tebipenem HBr, an oral carbapenem antibiotic for treating complicated urinary tract infections (cUTIs) in adults. Carbapenems are the standard of care for many drug-resistant gram-negative bacterial infections, but are currently only available as IV infusions, requiring hospitalization. Tebipenem HBr is designed to deliver carbapenem-class efficacy in an oral tablet, potentially allowing patients to avoid IV therapy. Spero has licensed exclusive worldwide development and commercialization rights (outside Japan and certain Asian markets) to GSK, which is responsible for all regulatory filings, commercial launch, and further development. Spero's role is now largely limited to supporting GSK through the FDA approval process. Spero's business model is built around milestones and royalties from the GSK deal rather than direct product sales. Spero received a $66M upfront payment at signing, with additional milestones tied to trial progress and regulatory events, and stands to earn up to ~$326M in commercial milestones contingent on first sales and net sales thresholds. Spero also earns tiered royalties on net sales, starting at 1% on annual sales up to $750M and rising to high single-digit to low double-digit percentages above $1B. Tebipenem HBr's Phase 3 PIVOT-PO trial met its primary endpoint at an interim analysis in May 2025 and was stopped early for efficacy. GSK submitted an NDA resubmission in December 2025, with a PDUFA date of June 18, 2026. Spero's two other pipeline programs have been discontinued.