GSK's Antibiotic Breakthrough: Tebipenem HBr Succeeds in Late-Stage Trial for Complicated UTIs

GSK, the British pharmaceutical giant, has announced a significant milestone in the development of a novel antibiotic for complicated urinary tract infections (cUTIs). The company's oral antibiotic candidate, tebipenem HBr, has successfully met its primary endpoint in a Phase 3 clinical trial, paving the way for a potential new treatment option in the fight against antimicrobial resistance.

Trial Success and Early Termination

The Phase 3 trial, dubbed Pivot-PO, compared tebipenem HBr to a common intravenous antibiotic treatment in patients hospitalized with cUTIs. An independent monitoring board recommended early termination of the study based on the drug's efficacy. Tebipenem HBr met the goal of non-inferiority to the comparator treatment, with no new safety concerns identified beyond those observed in previous research.

The most commonly reported side effects were diarrhea and headaches, consistent with earlier findings. This positive outcome positions tebipenem HBr as a potential first-in-class oral carbapenem antibiotic for the treatment of cUTIs, offering a new weapon in the arsenal against drug-resistant bacterial infections.

Regulatory Plans and Market Implications

Following the success of the Pivot-PO trial, GSK has announced its intention to submit a marketing application to the U.S. Food and Drug Administration (FDA) in the second half of 2025. This move comes after a previous setback when the FDA rejected the drug in June 2022 under its former developer, Spero Therapeutics.

The news has had a significant impact on Spero's stock, which more than tripled to approximately $2.15 in early trading on May 28, 2025. This dramatic increase follows a prolonged period of declined value, with shares having traded around $22 in December 2020 before closing at just 68 cents on May 27, 2025.

GSK's Strategic Acquisition and Development

The success of tebipenem HBr represents a strategic win for GSK, which acquired the rights to the drug from Spero Therapeutics in 2022. The acquisition deal included an upfront payment of $66 million to Spero, with the potential for additional royalties and milestone payments totaling up to $525 million based on regulatory approvals and sales performance.

This development follows GSK's recent success with Blujepa, another oral antibiotic approved by the FDA in March 2025 for the treatment of certain uncomplicated urinary tract infections. The potential addition of tebipenem HBr to GSK's portfolio further solidifies the company's position in the antibiotics market and its commitment to addressing the growing threat of antimicrobial resistance.