In a squeaker, FDA AdComm votes for an OK of Cempra’s antibiotic

Brian Skorney, Baird analyst

Brian Skorney, Baird analyst

Cempra $CEMP just barely squeaked through an AdComm review for its proposed new antibiotic solithromycin on Friday, with a slim majority of 7 to 6 casting votes in its favor on the key question of whether the benefits outweighed the obvious toxicity risks associated with their product.

Past safety issues associated with telithromycin (Ketek) clearly weighed on all the members, but with growing resistance to existing antibiotics becoming an ever-growing public health crisis, there were enough ‘yes’ votes to get this one over the line.

Next stop: The FDA has to make the formal decision, and it’s likely to consider this vote as a virtual split, leaving it in the position of either throwing up the stop sign, or signing on with a lot of strings attached to an approval.

The committee frequently zeroed in on the crux of the issue: New antibiotics are badly needed and solithromycin also met the pivotal endpoint on non-inferiority. But the antimicrobial drugs advisory group had to balance that against troubling signs of liver toxicity that could harm patients. And analysts were left skeptical that Cempra, even if it gets a formal OK, would be able to effectively market it. Noted Baird’s Brian Skorney:

(A)s we outlined in our downgrade note, marketing restrictions are likely to be so burdensome, if approved, based on panelists concerns over drug-induced liver injury and the unanimous requests to restrict and monitor it, the commercial potential could be negligible. Although we expect the stock to give up some of its losses on short covering, we continue to see the soli opportunity as fundamentally impaired by safety concerns.

How would Cempra track cases and what could they do to reduce risks after several adverse events were recorded in its trials?

These were three key questions:

  • Did the biotech provide sufficient efficacy data for treating community-acquired bacterial pneumonia?

The vote was unanimous, 13 to 0 in favor of solithromycin.

Marc Scheetz, a pharmacist, felt that the antibiotic should be rigorously limited to 5 to 7 days of therapy but agreed with the rest of the committee that the efficacy data were clear and that the antibiotic works as billed. Several committee members called the data adequate, but not necessarily substantial.

  • Was the risk of hepatoxicity properly characterized?

The vote went the other way, 12 to 1 voting ‘no.’ Small sample sizes in the trials drew some sharp responses and many of the committee members were clearly concerned about how this should be dealt with in the real world. For several panel members, the question seemed to balance on whether Cempra should be required to get a better understanding of the antibiotic in Phase III or Phase IV, after an approval.

Several committee members — though certainly not all — leaned toward a Phase IV, which would require a larger study, a point that was echoed by others.

  • Do the benefits outweigh the risk?

This was the money shot, and it just barely fell into Cempra’s favor.

Tom Boyer voted no. If there was no other option, he’d say yes, but the risk of toxicity clearly outweighed the benefit.

Marc Scheetz: Yes, but… “I wish I could have voted the mean, or maybe.” And its use should be severely restricted until more data is gathered.

Ellen Andrews says the bugs just won’t stop, and that’s what swayed her vote in favor of an approval, in spite of the risk.

The review today marks a critical juncture for a handful of biotechs with late-stage antibiotics. The path to market is clear, as are the obstacles in the clinic. None of that change today.

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