- Cempra Pharmaceuticals saw its stock free fall nearly 63% in Wednesday trading after Food and Drug Administration staff raised safety concerns about the company's drug for community-acquired bacterial pneumonia (CABP).
- In a document to be presented Friday to the Antimicrobial Drugs Advisory Committee, FDA staff indicated Cempra's solithromycin posed significant risks to patients' liver health.
- Solithromycin is part of a class of chemicals called macrolides which attach to ribosomal RNA of bacteria and limit antibiotic resistance. It is closely related to another FDA-approved drug for bacterial pneumonia, Ketek (telithromycin), which sparked controversy after it was linked to acute liver failure in some patients.
Cempra is betting big on its lead product. The company spent nearly $160 million on direct research and development for solithromycin between 2013 and 2015, and $13 million more this quarter, according to financial filings with the Securities and Exchange Commission. The company has been investigating the drug for over eight years, finally filing a new drug application with the FDA in April.
The agency's analysis of clinical data, however, flagged some concerns with the drug's safety profile. While FDA staff noted the efficacy of the drug — nearly 80% of patients across two Phase 3 trials hit the early clinical response primary endpoints — they also acknowledged a range of liver damage could be seen in some of the trials.
For example, early data from a 28-day study testing solithromycin's effects on airway inflammation in four patients showed three of them had liver damage.
"In the solithromycin development program to date, a range of patterns of liver injury associated with exposure to solithromycin were observed," FDA staff wrote in its document for the November 4 panel meeting.
The staff's analysis, however, concluded solithromycin did not present a serious risk of death by liver damage. They advised that the drug must prove more effective for at least some CABP patients than other pharmaceuticals, treat cases of CABP that are resistant to other macrolide medicine, and show fewer non-liver related adverse effects than competitors.
Should solithromycin meet those criteria, the staff recommended the drug come with a warning label and receive continued monitoring from regulators. If it can't, they said Cempra should conduct more clinical trials, though with higher patient numbers to better flesh out safety characteristics of the drug.
The advisory committee will make its recommendation decision based on the presentations made by both the FDA and Cempra. While the FDA typically follows the advice of its advisory panels, it is not obligated to do so.
The drug has two target actions dates, one for the oral version and one for the injectable, scheduled for December 27 and 28, respectively.
In a November 2 investor note, Jefferies analysts gave Cempra a "Buy" rating. Though the tone of the FDA staff's document may scare off some, the investment bank said the drug's liver toxicity issues could have been expected given its parallels to Ketek, and that the treatment could still receive a "positive panel outcome."
Cempra stock recovered some of its losses in Thursday morning trading, rising 1.5%. Still, this has been a bad couple of weeks for the Chapel Hill, NC-based company. Shares dropped 21% last Friday after executives revealed the FDA was holding off on approving a manufacturing plant in India.