The 3 Drug Classes for Experimental Ebola Treatment

Treatment success often depends on the stage of the infection in which they are administered.

There are some treatments to fight Ebola in development, but they are all experimental drugs targeting a disease that has a 70% or, in some cases, higher mortality rate.

Peter Hotez, MD, PhD, dean of the National School of Tropical Medicine at Baylor College of Medicine and director of the Texas Children’s Center for Vaccine Development, explains that there are currently 3 different drug classes used to treat Ebola, but the treatment success often depends on the stage of the infection in which they are administered.

1) Currently, there are 2 experimental antivirals available, but their mechanisms of action are not the same as that of the antiretroviral therapy (ART) used in HIV/AIDS. That is because Ebola exerts its virulence through the RNA-dependent enzyme, RNase, while HIV employs reverse transcriptase. The first antiviral is favipiravir (Avigan), produced by the Japanese company, Fujifilm. The second is brincidofovir (CMX001), produced by Chimerix in North Carolina. Dr. Hotez emphasizes that "antiviral therapy is most successful when [administered] before the infection advances to late stages where the viral load is high."

2) The second drug treatment option is the administration of a vaccine. Dr. Hotez reports that there are 2 available. “Currently, there is an adenovirus produced by GlaxoSmithKline (GSK) with a strain licensed from the National Institutes of Health (NIH),” he explains. According the GSK website, this vaccine is still under development, but the company “is working closely with the World Health Organization (WHO), regulators, and other partners to respond to the outbreak and to accelerate development of [its] investigational Ebola vaccine.” The second vaccine is the stomatitis vaccine, produced by New Link Genetics in Iowa. This vaccine is actually a recombinant form of the vesicular stomatitis virus. Shortly after the interview with Dr. Hotez, news broke that the National Microbiology Laboratory based in Winnipeg, Manitoba, is working with the WHO on a vaccine that contains both pieces of the Ebola virus, along with fragments of another vaccine that, at press time, remained unidentified.

3) The final drug class is monoclonal antibody (mAb) therapy, to which ZMapp belongs. Dr. Hotez shed some light on the reason why ZMapp is currently unavailable: “Because ZMapp is produced in plants, the yield of mAb is not high.” According to Mapp Pharmaceuticals' website, the manufacturer is in the process of producing more ZMapp, but it appears that there may be a delay in its availability, along with a potentially low yield, as Dr. Hotez indicated.

Meanwhile, the FDA recently granted Chimerix emergency investigational new drug status for brincidofovir, the experimental drug administered to Nebraska journalist Ashoka Mukpo, the late Thomas Eric Duncan, and the 2 Dallas nurses, Nina Pham and Amber Vinson. ZMapp was administered in the first Americans treated in the United States for Ebola, but still remains unavailable.

More companies are actively seeking similar experimental status from the FDA, which would allow their drugs to be administered in emergency situations.

Yet, some researchers are taking a broader approach to finding a cure. For example, Michael Kay, MD, PhD, a research scientist, professor, and director of graduate studies at the University of Utah School of Medicine, specializes in developing methods to counteract life-threatening infectious diseases such as HIV and Ebola. Dr. Kay has designed a novel drug target that mimics a particular region of the fusion peptide protein that “is conserved across all Ebola strains,” he reports.

The potential implications for the medical world are huge; however, the peptidomimetic won’t be coming to a pharmacy near you anytime soon. Dr. Kay reports that it is in preclinical stages now, undergoing tissue cultures and efficacy studies. He anticipates that it will take another 2 to 3 years before the target is tested in clinical studies.

Still, the fact that Dr. Kay has developed a drug target, rather than an actual drug, could potentially create an entire new class of drugs and pharmaceutical research for Ebola and other illnesses.

According to Dr. Kay, the methods by which the pepitodmimetic is produced were recently published, and he is hoping that universal access to this information will encourage other scientists to begin screening potential drugs for development. Meanwhile, the world is watching, waiting, and hoping. Unfortunately, for some Ebola victims, it may be too little too late as the hourglass runs out on their lives while they await treatment.