WASHINGTON (REUTERS) - Eli Lilly and Co on Wednesday (Sept 16) said a single infusion of its experimental antibody treatment reduced the need for hospitalisation and emergency room visits for clinical trial patients with moderate Covid-19.

The company said it will discuss the interim results, which have not yet been reviewed by outside experts, with global regulators.

A Lilly spokeswoman said discussions with the US Food and Drug Administration are expected to range from additional clinical trials to the possibility of an emergency use authorisation.

The mid-stage study tested three different doses of LY-CoV555, a manufactured copy of a an antibody produced by a patient who recovered from Covid-19. Antibody treatments work by recognising and locking onto foreign invaders to prevent infection of healthy cells.

Of the total 302 patients treated with the Lilly drug, five or 1.7 per cent, had to be hospitalised or required an emergency room visit. That compared with 6 per cent in the placebo group, Lilly said.

"These data are not a home run but ... are among the most encouraging Covid treatment data we've seen, particularly given this is in mild-to-moderate outpatients where there has simply been no treatment progress until now," Raymond James analyst Steven Seedhouse said in a research note.

Oddly, only the middle 2,800-milligram dose achieved the trial's main goal of reducing the amount of virus detected in patients compared with a placebo 11 days after treatment.

Lilly said most trial participants, including those given a placebo, had completely cleared the virus by day 11.

"It's clear that we need to look at impact on viral load at earlier timepoints or persistently high viral load," the company said in an emailed statement.

Most hospitalisations occurred in patients with underlying risk factors such as obesity or advanced age. Lilly said future study would focus on people in these higher-risk groups.

No drug-related serious adverse events or trial deaths were reported.

Lilly said the trial will enroll 800 patients with mild-to-moderate Covid-19, with the next segment testing LY-CoV555 in combination with a second Lilly antibody, LY-CoV016, which binds to a different area of the virus.

The antibodies, given by intravenous infusion, are also being tested for preventing Covid-19 in nursing home residents and staff and for treating patients already hospitalised with Covid-19.

Several companies including Regeneron Pharmaceuticals Inc and Vir Biotechnology are also testing antibody treatments for Covid-19.

Eli Lilly shares were up less than 1 per cent to US$151.28.