New Medicines

TembexaSmallpox virus infection - adults and paediatrics, including neonates


New molecular entity

Development and Regulatory status

Approved (Licensed)
Jan 22No indication on company website that they have plans to seek approval outside of the US. Company contacted for comment. [2]
Jun 21Approved in the US, where brincidofovir was granted fast track designation and orphan status, for smallpox for all age groups (adults and paediatrics, including neonates). Chimerix developed the Tembexa oral formulations (capsules and oral suspension) as medical countermeasures for the treatment of smallpox under an ongoing collaboration with BARDA, part of the office of the Assistant Secretary for Preparedness and Response within the U.S. Department of Health and Human Services [1].


Brincidofovir is a nucleotide analogue lipid-conjugate designed to mimic a natural monoacyl phospholipid to achieve effective intracellular concentrations of the active antiviral metabolite, cidofovir diphosphate [1]
Smallpox is a highly contagious disease caused by the variola virus. Historically, smallpox was one of the deadliest diseases in history with a case fatality rate of approximately 30%. Despite successful eradication of smallpox in the 1970s, there is considerable concern that variola virus could reappear, either through accidental release or as a weapon of bioterrorism [1].
Smallpox virus infection - adults and paediatrics, including neonates

Trial or other data

Jun 21Tembexa’s approval in the US is based on efficacy data in two lethal orthopoxvirus animal models of human smallpox disease, the rabbitpox model (New Zealand White rabbits infected with rabbitpox virus) and the mousepox model (BALB/c mice infected with ectromelia virus). In the pivotal studies in each model, Tembexa treatment resulted in statistically significant survival benefit vs placebo following delayed treatment after animals were infected with a lethal viral dose. The FDA’s ‘Animal Rule’ allows for testing of investigational drugs in animal models to support effectiveness in diseases which are not ethical or feasible to study in humans [1].