FDA reviewers raise hepatotoxicity concerns over Cempra's antibiotic solithromycin; shares fall

In documents released Wednesday ahead of an FDA advisory panel meeting on November 4, FDA staff said that Cempra's experimental community-acquired pneumonia therapy solithromycin can cause an elevation in liver enzyme levels. "A significant safety signal for hepatotoxicity was observed in the solithromycin development programme," agency reviewers noted, adding that another area of concern was "the high rate of infusion site-related reactions." Shares in Cempra fell nearly as much as 61 percent on the news. 

In the documents, FDA reviewers noted that solithromycin exhibited equivalent efficacy as moxifloxacin in clinical studies. However, the frequency of liver enzyme elevation was higher in the solithromycin arm. FDA staff cautioned that the elevations were temporary, adding that patients did not exhibit symptoms of liver problems. 

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Cempra developed solithromycin as a derivative of Sanofi's antibiotic Ketek (telithromycin), whose use was curtailed following reports of safety concerns. Labelling of the drug was also revised in Europe following a safety review. 

Commenting on the news, Cowen & Co. analyst Ritu Baral remarked "we think the institutional memory of Ketek will force the division into a highly conservative and defensive stance on solithromycin's safety profile." The analyst added that despite the possible safety issues, "we believe the agency would respect what we see as a likely positive panel vote for approval." 

For related analysis, read ViewPoints: Unloved in its own realm, Cempra goes in search of greener pastures with solithromycin.

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