WASHINGTON (REUTERS) - Regeneron Pharmaceuticals Inc on Thursday (June 11) said it had begun human testing of its experimental antibody cocktail as a treatment for Covid-19, the disease caused by the coronavirus.

The trial has an "adaptive" design and could quickly move from dozens of patients to eventually include thousands, chief scientific officer George Yancopoulos told Reuters.

"If it goes perfectly well, within a week or two, we will move to the second phase. Within a month or so of that we will have clear data that this is or isn't working. By the end of summer, we could have sufficient data for broad utilisation."

Regeneron shares rose about 2 per cent in early trading.

The dual antibody, called REGN-COV2, is being compared with a placebo treatment in hospitalised Covid-19 patients, and in Covid-19 patients who have symptoms but are not sick enough to be hospitalised.

Regeneron also plans to study REGN-COV2 for preventing the infection in people at high-risk of exposure - such as healthcare workers - and in uninfected people with close exposure to someone who has tested positive for the virus.

Antibodies are proteins made by the body's immune system that recognise, bind and neutralise an invading virus.

Regeneron's cocktail - which contains an antibody made by the company and a second isolated from humans who recovered from Covid-19 - is designed so that its two antibodies bind to the coronavirus' spike protein, limiting the ability of viruses to escape.

Trial patients will be given a single intravenous infusion of REGN-COV2. In the prevention segments of the study, participants will be given smaller subcutaneous doses, Dr Yancopoulus said. Investigators will be measuring patients'viral loads and keeping track of symptoms.

Regeneron said its treatment could be useful even if a Covid-19 vaccine is developed since the elderly and people with compromised immune systems often do not respond well to vaccines.

Dr Yancopoulos said, even though Regeneron does not yet have proof that REGN-COV2 is effective, the company has cleared the way for production of the antibody compound at its New York manufacturing facility.

Eli Lilly and Co could have a drug specifically designed to treat Covid-19 authorised for use as early as September if all goes well with either of two antibody therapies it is testing, its chief scientist told Reuters on Wednesday.