07:57 AM EDT, 05/28/2025 (MT Newswires) -- Spero Therapeutics ( SPRO ) and GSK (GSK) said Wednesday that a phase 3 trial of tebipenem HBr, an investigational oral antibiotic for complicated urinary tract infections, including pyelonephritis, met its primary endpoint and will end early due to efficacy.

An Independent Data Monitoring Committee recommended stopping the trial after a planned interim analysis of data from 1,690 patients showed that tebipenem HBr was non-inferior to IV imipenem-cilastatin at the test-of-cure visit, the companies said.

They added that no new safety concerns were identified, with diarrhea and headache as the most common adverse events.

The companies added that GSK plans to submit the data to US regulators in H2 2025.

Shares of Spero Therapeutics ( SPRO ) climbed by more than 230% in premarket trading, while GSK was little changed.