05:43 AM EDT, 10/21/2025 (MT Newswires) -- Spero Therapeutics ( SPRO ) and GSK (GSK), a British pharmaceutical group, reported early Tuesday that a phase 3 study of oral tebipenem HBr met its primary endpoint of non-inferiority compared with intravenous imipenem-cilastatin for treating complicated urinary tract infections.

The pivotal study was stopped early due to clear evidence of efficacy, the companies said.

An oral, 600 milligram dose of Tebipenem HBr achieved an overall success rate of almost 58.5% participants compared with over 60.2% overall success rate for a 500-milligram dose of imipenem-cilastatin administered intravenously.

The safety profile of tebipenem HBr was "generally similar" to that of other carbapenem antibiotics, the duo said, adding that the most frequently reported adverse events such as diarrhoea and headache were all "mild or moderate and non-serious."

Shares of Spero jumped 17% in recent premarket activity.