NEW YORK (BLOOMBERG) - A Regeneron Pharmaceuticals Inc. antibody cocktail may help treat coronavirus patients outside of the hospital by reducing virus levels and symptoms, early study results indicate.

In an early-stage clinical trial of 275 Covid-19 patients, those who received Regeneron's experimental therapy had lower virus levels in the bloodstream seven days later compared with patients who received a placebo, the company said in a statement.

Regeneron's treatment, which contains a mix of two highly potent antibodies against the coronavirus spike protein, "rapidly reduced viral load and associated symptoms in infected Covid-19 patients," George D. Yancopoulos, Regeneron's Chief Scientific Officer, said in the statement.

"The greatest treatment benefit was in patients who had not mounted their own effective immune response."

The results are a sign that experimental antibody treatments could become a powerful part of the arsenal for treating the coronavirus.

Dr Anthony Fauci, the top US infectious-disease official, has referred to antibody-based medicines that could treat infected patients sooner after they contract the virus as a bridge to a vaccine.

Several companies are developing similar therapies. Earlier this month, Eli Lilly & Co. said its experimental antibody treatment reduced the rate at which symptomatic coronavirus patients were hospitalised compared with a placebo.

Other companies testing antibody treatments include AstraZeneca Plc, as well as GlaxoSmithKline Plc and its partner Vir Biotechnology Inc.

Regeneron said its therapy appeared to be most beneficial in the subset of patients who hadn't yet produced coronavirus antibodies on their own.

In those patients, symptoms eased 8 days after they received a high dose of the cocktail, called REGN-COV2, compared with 13 days in antibody-negative patients who received a placebo.

Both high and low doses were well-tolerated, Regeneron said.

A much larger part of the trial that will generate definitive efficacy results plans to enroll 1,300 outpatient coronavirus sufferers.

In addition, Tarrytown, New York-based Regeneron is studying the therapy in hospitalised patients and also as a preventative in household contacts of infected individuals.