Drugmakers Lilly, Vir Biotechnology and GlaxoSmithKline on Wednesday announced plans to conduct a clinical trial to evaluate a combination of two drugs in people with mild to moderate infection of the coronavirus disease 2019 (Covid-19).

The drugs are both monoclonal antibodies, which are laboratory-made proteins designed to mimic the immune system’s ability to fight off viruses.

Similar combinations of these drugs can reduce levels of virus in the blood of Covid-19 patients by up to 20 percent, according to recent research.

“With a virus like [Covid-19], it’s expected that variants could emerge that require new therapeutic options, which is why Lilly is studying bamlanivimab together with other neutralizing antibodies,” Lilly chief scientific officer Dr. Daniel Skovronsky said in a press release.

The companies expanded an ongoing clinical trial will now evaluate the combination of Lilly’s bamlanivimab, at a dose of 700 milligrams, and Vir’s VIR-7831, at a dose of 500 mg., according to the companies.

“Adding VIR-7831 to our study is an important part of our commitment to develop therapies to treat current and future strains of Covid-19 until vaccines are widely available and utilized,” Skovronsky said.

Bamlanivimab already has received an emergency use authorization from the US Food and Drug Administration (FDA) for the treatment of mild to moderate Covid-19 in those who are at high risk for progressing to severe illness, Lilly said.

VIR-7831, which has not been approved by the FDA, is being evaluated in clinical trials as a standalone “early” treatment of Covid-19 in adults at high risk for hospitalization from the disease, officials said.

“We believe that VIR-7831 has significant potential as a single agent,” Vir CEO George Scangos said in a statement.

“As the virus continues to evolve, we, along with Lilly and GSK, share the view that we should pursue all possibilities to help end the pandemic and maximize the number of lives that can be saved,” he said.