The U.S. Food and Drug Administration (FDA) has issued a complete response letter (CRL) in response to Spero Therapeutics ‘ (NASDAQ:SPRO) New Drug Application (NDA) seeking approval for tebipenem HBr oral tablets for the treatment of adult patients with complicated urinary tract infection (cUTI), including pyelonephritis.

The New Drug Application (NDA) was supported by the clinical data readout from the Phase 3 study investigating tebipenem HBr.

Earlier in the month of May 2022, the FDA outlined potential deficiencies in the application at the late cycle meeting.

In the CRL, the regulatory agency indicated that the NDA could not be approved in its present form, the Phase 3 cUTI study of tebipenem HBr (ADAPT-PO) was insufficient to support approval and additional clinical study would be required.

Ankit Mahadevia, M.D., Chief Executive Officer, commented : “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.”

The company is planning to request a Type A meeting with the FDA, to gain further insights as to the pathway forward towards a potential regulatory approval for tebipenem HBr.

Spero Therapeutics’ shares are trading down 11 percent at $0.84 in the after-hours session.