Drugmaker Eli Lilly on Monday said it started early human trials of the world’s first potential antibody treatment for Covid-19.

Lilly said the first phase of the trial will track whether the treatment is safe and well-tolerated in patients hospitalized with the novel coronavirus.

The treatment uses an antibody designed to block the spike-shaped protein structures of the coronavirus from locking on to human cells, thus neutralizing it.

Lilly said the antibody treatment was developed after it was identified from a blood sample taken from one of the first U.S. patients who recovered from Covid-19.

The treatment was created in collaboration with AbCellera Biologics, a Canadian biotech company Lilly partnered with in March.

If the drug is show to be safe, Lilly said it will move on to the next phase of testing, which involves studying the potential treatment in non-hospitalized COVID-19 patients.

It says it expects results from that stage of the study by the end of June.