Two months after the FDA rejected Cempra’s lead drug, a different antibiotic from the drug developer is now showing promise as a potential treatment for aggressive skin infections such as MRSA.
Chapel Hill, NC-based Cempra (NASDAQ: CEMP) said that early data from a Phase 3 clinical trial evaluating its fusidic acid pills showed that the drug was roughly equal to another antibiotic currently used to treat skin infections. The news sent Cempra shares up more than 30 percent to $4.10 this morning.
Fusidic acid is the only member of a class of antibiotics called fusidanes. The drug targets the process that bacteria use to make essential proteins, Cempra says. Though the drug has been used for years to treat bacterial infections in Western Europe and Australia, it has never been approved in the United States.
The Phase 3 trial enrolled 716 patients who had aggressive bacterial skin infections, randomized to receive either Cempra’s drug, or linezolid, an antibiotic that is currently used to treat these infections. Patients were stratified by infection, age, and prior use of antibiotic in the 36 hours before entering the clinical trial. The main goal of the trial was reducing the size of patients’ skin lesions by 20 percent or more in the 48- to 72-hour window after starting the drug—without the administration of rescue antibiotics. Cempra said that 87.2 percent of patients receiving its drug met that mark, compared to 86.6 percent of patients who received linezolid.
The most common pathogens identified in patients enrolled in the trial included Staphylococcus aureus, which can produce staph infections, and Streptococcus anginosus, which can lead to infections of internal organs, such as the lung, liver, and spleen. Cempra said that among patients in the trial who had methicillin-resistant Staphylococcus aureus (MRSA) infection, the success rate of the Cempra drug was 100 percent. Besides skin infections, Cempra is also exploring use of fusidic acid to treat prosthetic joint infections.
Because fusidic acid has been used for decades in other countries, Cempra says that the drug has built up a large body of publicly available safety data. That could be an important factor given Cempra’s failure to win FDA approval for solithromycin, an antibiotic that the company developed to treat community-acquired bacterial pneumonia. The FDA rejected that drug last December and asked Cempra to conduct another clinical trial to address the agency’s concerns about liver injury.
In the fusidic acid clinical trials, Cempra said the most common side effects in both treatment groups were gastrointestinal trouble. In one instance, a patient treated with the Cempra drug vomited. The one patient death in the study was attributed to an illicit drug overdose. That patient was in the linezolid arm of the trial.
Cempra said that it plans to present full data from the fusidic acid clinical trial at an upcoming scientific meeting.