Cempra post positive Phase III results for solithromycin, but shares slump

In what seemed a somewhat contrary reaction, shares of US clinical-stage biotech firm Cempra (Nasdaq: CEMP) plunged 33.7% to $17.75 by mid-morning Friday in heavy trading, despite the company announcing positive top-line results from a global, pivotal Phase III clinical trial of intravenous (IV) to oral solithromycin (Solitaire-IV) in the treatment of patients with community-acquired bacterial pneumonia (CABP). However, there was also some negative news.

In the intent-to-treat population (ITT, all randomized patients), solithromycin met the FDA primary objective of statistical non-inferiority (NI, 10% non-inferiority margin) compared to moxifloxacin at the early clinical response (ECR, 72 [-12/+36] hours after initiation of therapy). The point estimates for the primary endpoint of early clinical response were 79.3% for solithromycin and 79.7% for moxifloxacin. The 95% confidence interval for the treatment difference had lower and upper bounds of -6.1% and 5.2%, respectively.

Solithromycin also met the co-primary objective of statistical NI compared to moxifloxacin at the ECR in the microbiological ITT (mITT) population (those patients with an etiologic diagnosis of the cause of CABP) from the pooled data from both Phase 3 studies. The point estimates were 77.2% for solithromycin and 78.9% for moxifloxacin with lower and upper bounds of the 95% confidence interval for the treatment difference of -7.4% and 4.2%.