Chimerix’s (NASDAQ: [[ticker:CMRX]]) lead antiviral drug candidate, which has already shown efficacy treating infections in transplant patients, is being called upon as an emergency Ebola treatment even as the company ramps up to test the drug in humans.
The Durham, NC company said today its drug brincidofovir has been made available for treating Ebola, in response to requests from doctors treating Ebola patients. This afternoon, Texas Health Presbyterian Hospital Dallas confirmed via its Twitter feed that Chimerix’s drug is being used to treat critically ill Ebola patient Thomas Duncan. The hospital says he was first administered the drug on Saturday.
In the absence of any Food and Drug Administration-approved drugs to treat Ebola, hospitals have turned to experimental treatments. Texas Health Presbyterian’s use of the Chimerix drug comes as supplies of Mapp Biopharmaceutical’s Ebola drug ZMapp, which has been used to treat several patients, have been exhausted. The company had initially made only enough of the drug for testing. Plans are underway to manufacture more ZMapp, but even when the infrastructure is in place, production can take months.
Brincidofovir is already in late-stage clinical trials to treat cytomegalovirus infection in stem cell transplant patients, whose weakened immune systems make them susceptible to the virus. But Chimerix has long noted that its drug is a broad-spectrum antiviral with potential applications treating a wide range of viruses. Brincidofovir contains what is called a nucleotide analog, a molecule that is similar to the natural nucleotides that are the building blocks of DNA and RNA. When viruses like Ebola replicate by copying their genes, they grab the analog by mistake in their new genetic strands. That stops the process, preventing the virus from replicating.
With brincidofovir, Chimerix aimed to develop an antiviral whose broad spectrum of activity is comparable to that of Gilead Sciences’s (NASDAQ: [[ticker:GILD]]) antiviral cidofovir (Vistide). In fact, brincidofovir is based on cidofovir. Chimerix’s key innovation was attaching cidofovir to pieces of lipids, a type of fat. The lipids enable the drug to be absorbed by the gut, and they also may boost uptake of the antiviral drug into cells infected by viruses. As a result, brincidofovir can be given as an oral pill or liquid suspension, while cidofovir must be intravenously administered. Equally important, the addition of the lipids enables brincidofovir to avoid cidofovir’s toxic effects on the kidneys.
The federal government was an early supporter of Chimerix’s antiviral efforts. In 2011, the Biomedical Advanced Research and Development Authority (BARDA) awarded Chimerix a contract, valued at up to $81.1 million, to develop a medical countermeasure against weaponized smallpox. The antiviral studied in that program is now the experimental drug brincidofovir. In September, BARDA extended the bioweapon countermeasure contract by 15 months and awarded Chimerix an additional $17.0 million.
Chimerix already has safety data on brincidofovir in humans from clinical trials testing the drug as a treatment to prevent cytomegalovirus infection in stem cell transplant patients. The company this year also used its drug to treat seven-year-old Josh Hardy, a Virginia boy who became infected with adenovirus while undergoing cancer treatment. Chimerix found itself at the center of a heated media and social media debate calling for compassionate use of the drug. But instead of simply providing the drug to Hardy, Chimerix was able to work with regulators to enroll the boy in an open-label clinical trial studying the drug in patients with adenovirus. Hardy has reportedly responded well to the drug and was able to return home.
Chimerix says that lab tests of brincidofovir at the Viral Special Pathogens Branch of the Centers for Disease Control and Prevention as well as the National Institutes of Health showed that the drug’s activity against the Ebola virus was similar to the activity against other viral pathogens, such as adenovirus and the smallpox virus. Chimerix says that it is working with the FDA to finalize a clinical trial protocol “early this week” to test brincidofovir’s safety, tolerability and efficacy in patients confirmed to have Eblola infection. Tests of the drug in animals infected with Ebola are already underway.
