During Merck's (MRK 0.36%) second-quarter earnings call on Friday, the company's head of research and development discussed progress on a potential new treatment for COVID-19 patients. The antiviral candidate MK-4482 is a nucleoside analog that makes it hard for SARS-CoV-2 to replicate itself in the laboratory and is being developed in partnership with Ridgeback Biotherapeutics.

Following encouraging results from an ascending dose study, Merck thinks MK-4482 is well-tolerated at levels that should be more than enough to stop SARS-CoV-2 in its tracks. Based on preliminary results from three mid-stage studies, Roger Perlmutter, president of Merck Research Laboratories, believes the company will begin a pair of large pivotal trials in September. 

Coronavirus sample vials and a syringe.

Image source: Getty Images.

Merck is also in discussion with the National Institute of Allergy and Infectious Diseases (NIAID) about a large outpatient study to be conducted under the institute's supervision.

In a laboratory setting, MK-4882 has shown an ability to combat viruses that have acquired mutations, rendering them resistant to the only antiviral treatment currently available for COVID-19 patients, remdesivir from Gilead Sciences (GILD -0.47%). And Merck's coronavirus antiviral candidate could have another leg up on Gilead's treatment. Remdesivir is delivered as an intravenous infusion, while MK-4482 is an easy-to-swallow tablet.

Merck is moving pretty quickly with MK-4882, but it's still far behind an injectable antiviral treatment candidate for COVID-19 from Regeneron (REGN -0.68%). The dual-antibody cocktail called REGN-COV2 has already entered pivotal studies with COVID-19 patients in partnership with NIAID.

Editor's Note: This article was updated to reflect that the drug MK-4882 is being developed in collaboration with Ridgeback Biotherapeutics.