It's a good news, bad news FDA approval for Achaogen's powerful antibiotic Zemdri

Achaogen secured FDA approval for Zemdri on Tuesday, but the agency rejected one indication the company sought. (Achaogen)

Achaogen got some anticipated good news Tuesday with an FDA nod for its high-powered antibiotic Zemdri, but it wasn't an unqualified win. Zemdri will make its debut as a treatment for drug-resistant urinary tract infections with a black-box warning, and it missed out on a second use—bloodstream infections—it had hoped to win this first go-round.

The South San Francisco biotech won FDA approval for Zemdri to treat adults with complicated UTIs when they lack other options. The drug is "designed to retain its potent activity" when attacking difficult-to-treat infections resistant to multiple antibiotics, CEO Blake Wise said in a statement.

For example? Carbapenem-resistant bacteria—which the CDC has described as a "nightmare bacteria"—and extended spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, dubbed a "serious threat." Zemdri is a daily IV drug developed with "significant" financial support from BARDA, a U.S. agency attached to HHS, Wise said. 

The multidrug-resistant, gram-negative pathogens Zemdri targets have arisen as a major threat to health systems and patients, forcing long and costly hospital stays. And it's a somewhat rare debut these days; in recent years, experts have lamented a lack of R&D in the field even as drug-resistant pathogens proliferate worldwide.

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Zemdri will bear a boxed warning that details its potential to cause kidney damage, hearing loss, and neuromuscular blockade, a condition that can result in muscle weakness or paralysis. The warning will also state Zemdri can harm developing fetuses.

The FDA also stiff-armed Achaogen's bid to launch Zemdri as a treatment for bloodstream infections, after its panel of expert advisors voted against that approval last month. The CRL cited a lack of efficacy data for that use, Achaogen said, adding that it plans to meet with the agency to "determine whether there is a feasible resolution" to clear the way for a second try.

Leerink analysts have predicted the drug could pull in $500 million in sales at peak. And launch preparations have already started, executives said last month. On Achaogen's first-quarter conference call in early May, chief commercial officer Janet Dorling said the company was progressing on a goal to hire about 60 hospital account managers.

"Our current field team continues to profile our target accounts to ensure we can hit the ground running at launch," she added.

But Zemdri isn't the only new antibiotic doctors will have in their arsenals to treat complicated urinary tract infections. The Medicines Company won a similar approval for Vabomere last year, and an analyst has predicted $400 million in peak sales for the drug.

In its bid for a bloodstream infection approval, Achaogen followed a new FDA pathway for limited-population antibacterial drugs. The drug was the first evaluated using that pathway.

Achaogen shares were down about 22% on Tueday on the mixed news.