(Adds background, details of CRL)
June 27 (Reuters) - The U.S. Food and Drug Administration (FDA) declined to approve Spero Therapeutics Inc's oral antibiotic drug for the treatment of patients with complicated urinary tract infections, the company said on Monday.
In the complete response letter, the health regulator concluded that Spero's late-stage study testing the drug was insufficient and an additional study would be required, the drugmaker said.
Shares of Spero fell about 14% after the bell.
Spero had sought approval for its most advanced drug candidate, tebipenem, to treat the infections, including a type of kidney inflammation called pyelonephritis in adult patients with limited oral treatment options.
But the company suffered a setback in March when the agency found certain deficiencies in the drug's marketing application. Spero later suspended commercialization activities for tebipenem and slashed its workforce by about 75%, as the FDA's feedback suggested that the data on the drug could be insufficient to obtain approval.
The drugmaker said on Monday it intends to promptly request a meeting with the health regulator.
(Reporting by Amruta Khandekar and Bhanvi Satija; Editing by Shounak Dasgupta and Aditya Soni)