solithromycin

Drug Overview

Solithromycin (Cempra Pharmaceuticals/Cubist Pharmaceuticals/Toyama Chemical) is a next-generation ketolide antibiotic. The drug, which is structurally related to the macrolide class of antibiotics, is the first fluoroketolide antibacterial in clinical development for bacterial infections, including CAP. In a manner similar to earlier macrolides and ketolides, solithromycin inhibits bacterial protein synthesis by binding to the bacterial ribosomes. However, the drug exhibits an enhanced mechanism of action over Ketek and macrolides, stemming from its unique ability to bind the bacterial ribosome at three different sites. This reduces the ability of bacterial strains to select resistance against it. In vitro studies indicate that solithromycin exhibited a 16-fold enhanced potency over azithromycin.

Analyst Outlook

Solithromycin (Cempra Pharmaceuticals/Cubist Pharmaceuticals/Toyama Chemical) is the first fluoroketolide in clinical development for community-acquired pneumonia (CAP). In Phase III development, oral solithromycin demonstrated non-inferiority to moxifloxacin in the treatment of adult CAP patients. Cempra is currently conducting Phase III development of an intravenous (IV) form of the drug. Solithromycin’s enhanced mechanism of action enables it to demonstrate high potency against a range of bacterial pathogens, as well as retain its efficacy against bacterial strains resistant to earlier generations of macrolides. Solithromycin has also gained a regulatory advantage through a Qualified Infectious Disease Product (QIDP) designation from the US Food and Drug Administration (FDA).  Datamonitor Healthcare believes that in order to benefit from these advantages, solithromycin will need to overcome negative safety perceptions associated with the use of the first ketolide antibiotic in the CAP market: Ketek (telithromycin; Sanofi). Cempra will also benefit from forging collaborations with larger pharmaceutical companies with proven experience in the antibacterials market. These would enhance the drug’s penetration in the CAP market, and maximize its commercial potential.