Chapel Hill, NC-based Cempra (NASDAQ: CEMP) said this morning that an intravenous form of its drug, solithromycin, was successful treating patients with community-acquired bacterial pneumonia. Compared against an existing antibiotic and former blockbuster drug, Bayer’s moxifloxacin, the Cempra drug was statistically “non-inferior”—the main goal of the study.
But patients did not respond to the IV form solithromycin as well as they did to a capsule form of the drug, which showed positive results in a separate Phase 3 study earlier this year. In a note to investors, Leerink Partners said that while the IV form of the Cempra drug hit its main targets, the IV drug did not measure up as well as the capsule form did against moxifloxacin. Leerink says that the IV drug was 4 to 5 percent worse than moxifloxacin on short-term follow up visits, five to 10 days after initially receiving the drug. But Leerink says it is confident the drug can receive U.S. approval.
In addition to not working as well as the capsule form, the IV form of the Cempra drug was associated with more adverse events than moxifloxacin. These reactions—pain or rash at the site of injection—were observed in 34.3 percent of patients receiving the Cempra drug but just 13.1 percent of those receiving moxifloxacin. Cempra said that infusion site pain is a known side effect of intravenously administered macrolides, the drug class that solithromycin belongs to. Another three patients in the trial were reported to have allergic reactions, two of them patients who received solithromycin. Investors frowned on the results, sending Cempra’s stock tumbling 33 percent down to $17 per share.
On a conference call with analysts, CEO Prabhavathi Fernandes said that patients with community-acquired bacterial pneumonia tend to be older and sick with other conditions. She said that those who don’t take well to the IV version of the drug could instead take the capsule form.
“In real life, you can switch them to oral,” she said. “You can see the data is very good orally, and very good IV.”
The latest Cempra study included switching patients from the IV form of solithromycin to the capsule form. Fernandes said that the ability to switch patients from an IV form to a capsule may allow for earlier hospital discharge of patients, which would save on healthcare costs.
Already approved macrolides include antibiotics used to treat bacterial infections such as pneumonia and Legionnaire’s disease. If solithromycin secures FDA approval, it would become the first macrolide to reach the reach the market since azithromycin’s approval in 1988. But azithromycin has fallen out of favor due to growing bacterial resistance to that drug.
Cempra’s antibiotic has shown activity against a wide range of bugs and the company is currently studying the drug in multiple clinical trials. Fernandes said a Phase 3 study in gonorrhea is continuing, as well as two separate mid-stage studies in chronic obstructive pulmonary disease and non-alcoholic steatohepatitis, or NASH. Cempra has also developed liquid and pill forms of the drug for children that are now in early-stage clinical trials, financed by a $58 million contract from the Biomedical Advanced Research and Development Authority. Fernandes said that Cempra’s work in these three applications of the drug will not be part of the upcoming drug filing with the FDA.
Following positive Phase 3 results for the capsule form of solithromycin in January, Cempra completed a stock offering raising more than $138 million to finance R&D, regulatory work, and commercialization plans for the drug. With results from both the capsule and IV forms of the antibiotic now in hand from studies in 1,723 patients, Cempra plans to start work on a new drug application filing with the FDA, which it expects to complete in the first half of 2016.
Cempra already has “fast track” designation from the FDA on both the IV and capsule forms of solithromycin for treating community-acquired bacterial pneumonia. The regulator last month also designated both forms of the drug as “qualified infectious disease products” for that condition. A capsule form of the drug had previously received that designation for gonorrhea. The QIDP designation means that the drug could receive priority review by the FDA and possible fast-track status. Also, if approved, the drug could receive a five-year extension of marketing exclusivity.