07:47 AM EST, 12/05/2024 (MT Newswires) -- Merck ( MRK ) said Thursday that it has started a late-stage clinical trial to assess investigational oral antiviral COVID-19 medicines Lagevrio or molnupiravir for the treatment of adults with COVID-19 who are at high risk for disease progression.

Lagevrio is being developed by Merck ( MRK ) in collaboration with Ridgeback Biotherapeutics.

The study is enrolling individuals who are at least 18 years, have tested positive for SARS-CoV-2 infection, have had COVID-19 symptoms for four days or less, and have not been hospitalized, the company said.

The study will only include adults who are unable to receive nirmatrelvir/ritonavir due to drug-drug interactions, allergy, previous adverse effects, or inaccessibility, the company said.

The trial introduces a different formulation of Lagevrio, consisting of four daily tablets of two smaller 400-mg tablets per dose, rather than the currently available eight 200-mg capsules per day. The updated tablets have not yet been approved in any country.