Buffeted by safety fears, Cempra shares crushed after FDA flags a warning on its antibiotic

Shares of Cempra Pharmaceuticals plunged 45% $CEMP in early trading Wednesday after investors were alarmed by an FDA review of its antibiotic, which raised red flags over a serious safety issue involving liver injuries among the patients they tested it on.

Solithromycin is designed to work by meddling with bacterial protein synthesis. And with a large number of community-acquired bacterial pneumonia patients (CABP) resistant to the leading antibiotic on the market, the Chapel Hill, NC-based biotech has won close attention for its research work.

The FDA reviewers had no trouble signing off on the antibiotic’s non-inferiority to moxifloxacin in treating CABP, with the treatments looking virtually identical on efficacy in two late-stage studies.

But on the safety front, the FDA had serious concerns. Their summary concludes:

In the solithromycin development program to date, a range of patterns of liver injury associated with exposure to solithromycin were observed. There was a spectrum of both hepatocellular and cholestatic signatures of hepatotoxicity, in one case accompanied by eosinophilia and suggesting hypersensitivity as a mechanism for liver injury. These findings were noted among a relatively small number of patients treated with solithromycin for CABP (n=920), normal healthy volunteers exposed to the drug in PK studies, and a small number of patients administered solithromycin in studies of other conditions. We conclude that these findings comprise a genuine liver injury signal.

That comes on top of manufacturing issues that Cempra has had to confirm in recent days, further contributing to the negative mood about their chances of a near-term approval. Late last week the company told investors that it needed to scramble to line up a fresh supply of solithromycin after regulators flagged issues with their main contract manufacturer. And the string of manufacturing issues that have plagued companies this year has put the issue squarely in the center of biopharma’s problems with R&D productivity in 2016, as new drug approvals lag well behind last year.

Cempra is the most advanced among handful of biotechs with late-stage programs underway for new antibiotics. Nabriva and Paratek are two more rivals in this field. While regulators have been advancing new ways to encourage development efforts in the field, Big Pharma has had a long and wary relationship with antibiotics, with many of the biggest players bowing out due to low margins and high R&D risks.

The AdComm is slated for Friday.

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Sr. Manager, Regulatory Affairs, CMC
CytomX Therapeutics San Francisco, CA
Marketing Associate - Demand Generation
Catalytic Data Science Charleston, SC
Associate Principal, Life Sciences Partnerships
Flatiron Health New York City or San Francisco

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