An FDA panel has voted 7-6 that Cempra’s ($CEMP) new antibiotic solithromycin should be recommended for U.S. regulatory approval–coming days after its shares plummeted by 40% on safety fears.

The committee voted unanimously (13 to 0) that there was substantial evidence of the efficacy of solithromycin in CABP. However, the committee also voted 12 to 1 that the risk of hepatotoxicity with solithromycin had not been adequately characterized.

The target dates for the FDA to take action under the Prescription Drug User Fee Act (PDUFA) are December 27 and 28, 2016, for the oral and intravenous (IV) filings, respectively.

The FDA is not bound by its advisory committees’ recommendations, but it takes their advice into consideration when reviewing investigational medications. If approved, solithromycin would be the first new macrolide antibiotic with both oral and IV formulations in more than 20 years.

Solithromycin is a next-generation macrolide with activity against most macrolide-resistant CABP pathogens, according to Cempra. In vitro and in vivo studies have shown activity against Streptococcus pneumoniae as well as an extended spectrum of activity against community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), streptococci, haemophilus, enterococci, Mycobacterium avium, and malaria. It is also active against atypical bacteria, such as legionella, chlamydia, mycoplasma, and ureaplasma, and against gonococci and other organisms that cause genitourinary-tract infections. Solithromycin is eight to 16 times more potent than azithromycin against many bacteria and is active against azithromycin-resistant strains. The activity of solithromycin against resistant strains is driven by its ability to interact with three sites on the bacterial ribosome, compared with the single binding site of first- and second-generation macrolides.

CABP is the number one cause of death from an infection, particularly in the very young and in the elderly. It is one of the most commonly diagnosed bacterial infections in the United States with five to 10 million cases per year. Although many strains of the primary CABP pathogen, S. pneumoniae, are resistant to currently approved macrolides, this class of antibiotic remains among the most commonly prescribed antibacterial drugs for CABP in both hospital and community settings.

New CABP treatments are needed, Cempra says, because of the rising threat of antimicrobial resistance, along with concerns about antibiotic tolerability and the impact on intestinal microflora.

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