The two partners in August started testing the antibody on early-stage COVID-19 patients, hoping to keep symptoms from progressing.
Various firms are running tests in this promising class of antiviral drugs to combat the pandemic.
After testing the drug on 20 U.S. participants for safety, the trial will now expand as planned to 1,300 patients globally.
Half the participants will be randomly assigned to a control group receiving a placebo.
Interim trial results may be available as early as the end of 2020. Complete efficacy results are expected as early as January or later in the first quarter of 2021.
The long-acting single injection will be tested on recently diagnosed high-risk cases for its ability to prevent hospitalisation, typically a life threatening disease stage.
An experimental two-antibody combination under development by Regeneron was mong the drugs used on U.S. President Donald Trump for his COVID-19 infection.
That was only days after Regeneron, in a manufacturing partnership with Roche, said the drug was shown to reduce viral levels and improved symptoms at an early disease stage. That data would likely support a request for emergency use authorization.
Eli Lilly, which will get manufacturing help from Amgen, last month also released data showing that one of its antibodies lowered patient virus levels and could prevent disease progression.
Natural antibodies, part of the body’s adaptive immune system, are normally made by white blood cells in response to a foreign substance in the body.
But pharma companies, also including AstraZeneca and Molecular Partners, are working on monoclonal antibodies made in bioreactors from living cells, for a more targeted attack on the virus.