Durham, NC based biopharmaceutical company, Chimerix announced yesterday that its investigational antiviral brincidofovir showed a survival benefit in a pivotal study of an animal model for smallpox.

Chimerix is developing brincidofovir as a medical countermeasure against smallpox, for which there is no antiviral agent currently approved. Brincidofovir has demonstrated broad-spectrum in vitro activity across five families of DNA viruses, and in addition to smallpox, is also being studied in two Phase 3 clinical trials for prevention of cytomegalovirus (CMV) and treatment of adenovirus infections in immunocompromised patients. The U.S. Food and Drug Administration (FDA) has granted Fast Track status to brincidofovir for smallpox, CMV, and adenovirus.

The pivotal smallpox study was conducted under the FDA’s Animal Efficacy Rule, which allows for testing of investigational compounds in animal models to support the drug’s effectiveness in diseases which are not ethical or feasible to study in humans. The primary objective of this study was to assess the efficacy of immediate and delayed treatment with brincidofovir after clinical signs of disease compared with placebo in preventing mortality in rabbits infected with the lethal rabbitpox virus a well-characterized model of smallpox. The study met its primary endpoint.

Rabbits treated with brincidofovir upon the first clinical sign of disease, and rabbits that received brincidofovir 24 or 48 hours after the first clinical sign of disease, demonstrated a statistically significant (p < 0.05) reduction in mortality compared to rabbits that received placebo. Final results from this study, including data on the incidence and severity of clinical and laboratory events in each cohort, are expected by the fourth quarter of 2015 and will be submitted to an upcoming medical conference and to the FDA for discussion of next steps.

The brincidofovir doses used in this animal study were scaled to equivalent doses used in the Phase 3 clinical trials of brincidofovir for CMV and adenovirus in humans, the SUPPRESS and AdVise trials, respectively. Additional data may be required prior to a new drug application (NDA) submission for smallpox.

“Data from this pivotal study support the potential for brincidofovir to contribute to the U.S. national security and public health preparedness for the treatment of smallpox, which is a Category A Priority Pathogen,” said M. Michelle Berrey, MD, MPH, President and CEO of Chimerix. “We look forward to continuing our work with BARDA and the FDA to advance brincidofovir as a medical countermeasure for smallpox.”

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