SARS-CoV-2, initially called 2019-nCoV, is a novel human coronavirus renamed after because of its significant homology to SARS-CoV. It is an enveloped, positive sense, single strand RNA virus with a genome size of almost 30KB, which encodes both structural proteins such as the spike glycoprotein responsible for interaction with cell receptor and viral entry and non-structural proteins such as 3C-like protease, papain-like protease and RNA-dependent RNA polymerase that are essential for viral replication.


The pandemic coronavirus disease COVID-19 is caused by the infection of a novel human coronavirus, severe acute respiratory syndrome-coronavirus (SARS-CoV-2). This is only the seventh known coronavirus that infects humans. Some of the previously identified strains such as HCoV-229E and HCoV-OC43 have been circulating in humans for years but usually cause only very mild symptoms. Two recent outbreaks with the highly pathogenic SARS-CoV and MERS-CoV were quickly suppressed through rigorous infection control.

In August 2021, Enanta announced that it had nominated EDP-235, its lead oral protease inhibitor specifically designed for the treatment of COVID-19. Enanta expects to initiate a Phase 1 single and multiple ascending dose study to evaluate the safety, tolerability, and pharmacokinetics of EDP-235 in healthy volunteers in early 2022.

EDP-235 potently and selectively inhibits SARS-CoV-2 replication in multiple cellular models, including primary human airway epithelial cells, with an EC90 of 33nM. EDP-235 retained activity against protease enzymes from currently circulating SARS-CoV-2 variants. Importantly, EDP-235 has excellent lung distribution preclinically and demonstrates properties supportive of once daily oral dosing. Furthermore, EDP-235 has shown activity against other coronaviruses, providing the opportunity to potentially treat other infections that may emerge in the future.

While vaccines and antibody therapeutics in development today target the viral spike protein, EDP-235 has been specifically designed to target conserved regions in the active site of a viral enzyme essential for SARS-CoV-2 replication. Thus, Enanta does not expect mutations in the spike protein to affect the activity of EDP-235 and is encouraged by the promising preclinical data generated to date.

For an overview of our research, including our licensed products, please see Our Pipeline.