Spero Searching for Way Forward after FDA Rejects cUTI Drug

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Shares of Spero Therapeutics fell rapidly in premarket trading Tuesday after the company announced it had received a Complete Response Letter from the U.S. Food and Drug Administration for its complicated urinary tract infection  (cUTI) therapy, tebipenem HBr oral tablets.

Cambridge, MA-based Spero said the FDA determined the New Drug Application, which had been accepted under priority review, could not be approved in its current form, something the company predicted in May. At that time, Spero announced a possible delay based on feedback from a Late Cycle Meeting. The FDA hinted that the data package for tebipenem HBr was likely not sufficient enough to support approval. Tebipenem HBr (tebipenem pivoxil hydrobromide) is being developed by Spero as the first oral carbapenem antibiotic for use in cUTI, including pyelonephritis.

In the CRL, the FDA said the Phase III ADAPT-PO trial, which assessed tebipenem HBr as a therapy for cUTI, was not strong enough to support approval and suggested the company run another trial. ADAPT-PO was a global, randomized, placebo-controlled clinical trial that assessed the safety and efficacy of oral tebipenem HBr compared to intravenous ertapenem for the treatment of adults with cUTI, including acute pyelonephritis. Spero said that the Phase III study was the first to compare an oral treatment against an intravenous one for cUTI.

In May, after being told of the likelihood of the CRL, Spero cut 75% of its staff as it underwent a restructuring to preserve cash. The company said it has requested a Type A meeting with the FDA in order to understand the regulatory agency’s reasoning and expectations regarding a new trial.

Ankit Mahadevia, CEO of Spero, expressed his disappointment in the CRL. He said the company leadership team is disappointed with the decision but remains committed to addressing those concerns and determining a “clear path forward” for tebipenem HBr.

“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,” Mahadevia said in a statement.

Mahadevia reiterated the company’s commitment to developing medications for unmet needs, such as cUTI and other indications. He said tebipenem HBr remains an important part of Spero's pipeline, along with SPR720 and SPR206, which are being developed for a rare, orphan pulmonary disease and multidrug-resistant Gram-negative infections in the hospital setting, respectively.