The Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) to Spero Therapeutics regarding the New Drug Application (NDA) for tebipenem HBr (tebipenem pivoxil hydrobromide) for the treatment of adults with complicated urinary tract infections (cUTI), including pyelonephritis, caused by susceptible microorganisms.

Tebipenem HBr is an investigational oral antibiotic in the carbapenem class. In January 2022, the FDA accepted for Priority Review the NDA for tebipenem HBr based on data from the phase 3 ADAPT-PO trial ( Identifier: NCT03788967), which evaluated the efficacy and safety of tebipenem HBr in 868 adults with cUTI or acute pyelonephritis. 

Findings showed that treatment with tebipenem HBr was statistically noninferior to ertapenem with respect to overall response (combined clinical cure plus microbiological eradication) at the test-of-cure visit in the microbiological-intent-to-treat population.

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In the CRL, the FDA stated that the application could not be approved in its present form and that an additional clinical trial would be required. The outcome had been anticipated by the Company. In a previous statement, Spero Therapeutics noted that a separate FDA analysis of data from the ADAPT-PO trial resulted in the prespecified noninferiority margin of -12.5% not being met.

“We are disappointed with the FDA’s decision, but we look forward to our continued dialogue, addressing the agency’s concerns and outlining a clear path forward for tebipenem HBr,” said Ankit Mahadevia, MD, CEO of Spero Therapeutics. “With this development, we continue to believe that tebipenem HBr offers patients and their providers an important new treatment option that if approved, has the potential to address the critical unmet need for a new oral antibiotic for patients with cUTI.”


Spero Therapeutics receives Complete Response Letter from US Food and Drug Administration for tebipenem HBr New Drug Application. News release. Spero Therapeutics Inc. Accessed June 28, 2022.

This article originally appeared on MPR