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than temporarily stopping administration of the Chimerix drug according to the safety plan the company had developed in Phase 2. Interrupting dosing of the drug should improve the diarrhea, if it is caused by the drug, according to the safety plan. If the diarrhea does not improve, the plan instructs physicians to look for other causes, such as graft versus host disease.
In clinical trial sites that followed the safety plan and interrupted dosing of the Chimerix drug, patients had better outcomes, Chief Medical Officer Garret Nichols said. He added that even though Chimerix staff briefed investigators on the safety plan at each clinical trial site, there were still differences in how closely the sites followed the plan. In one third of sites, patients were treated with corticosteroids without stopping the Chimerix drug. Nichols said the results of the trial underscored the need to emphasize to physicians the importance of interrupting dosing of the Chimerix drug early and allowing the gut to heal before resuming treatment.
Chimerix said there were no statistically significant differences in patient deaths when comparing brincidofovir to a placebo. Though 15 more people died on its drug than on placebo, Chimerix attributed the deaths to higher use of immunosuppressive therapies. The Chimerix drug also failed a secondary goal of the clinical trial—preventing infections with a virus known as BK, which like CMV can also cause trouble for patients with weakened immune systems.
Despite closing the trials in kidney transplant patients, Berrey said the on the call that Chimerix remains committed to addressing infections in these patients. While kidney transplant patients are not at risk for graft versus host disease, they can experience diarrhea. Berrey said that the company needs to have a more complete understanding of the failed trial before it invests in additional late-stage studies. “We are not walking away from the kidney transplant population,” Berrey said on the call. “We continue to believe this unmet need can be met with brincidofovir.”
Nor is Chimerix isn’t giving up on brincidofovir as a preventative therapy for CMV in stem cell transplant patients, who currently have no FDA-approved drugs to help them fight the virus. Rather, it’s taking them back to Phase 2 testing, where Chimerix hopes to confirm the drug’s activity against BK virus. The company says these studies will also explore ways to manage adverse events associated with its drug.
The Chimerix drug is also in a separate late-stage clinical trial for adenovirus infections in patients with weakened immune systems that is expected to produce data in mid-2016. Chimerix is also studying its drug as a smallpox countermeasure, research that is funded by the Biomedical Advanced Research and Development Authority. Chimerix plans to discuss the full results of the failed trial with the FDA, including the data it has so far for adenovirus and smallpox.
Chimerix still wants to proceed with an intravenous form of brincidofovir in preclinical testing that the company says might avoid the diarrhea caused by the pill form of the drug. If those results hold up in human testing, Chimerix says it could explore dosing patients with the IV form of the drug in the weeks after a transplant, with the pill form of the drug made available when they go home.