Gilead Sciences Inc's experimental coronavirus drug failed its first randomised clinical trial, the Financial Times reported on Thursday, citing draft documents published accidentally by the World Health Organisation.

Trading in the shares of the company was halted after they fell 6%. The Chinese trial showed the antiviral remdesivir did not improve patients' condition or reduce the pathogen's presence in the bloodstream, the report said.

Researchers studied 237 patients, giving the drug to 158 and comparing their progress with the remaining 79. The drug also showed significant side effects in some, which meant 18 patients were taken off it, according to the report.

Interest in Gilead's drug had been high as there are currently no approved treatments or preventive vaccines for COVID-19, and doctors are desperate for anything that might alter the course of the disease that attacks the lungs and can shut down other organs in extremely severe cases.

The company is testing the drug in multiple trials and highly anticipated trial results from a study involving 400 patients hospitalized with severe cases of the illness are expected later this month.

Remdesivir, which previously failed as a treatment for Ebola, is being tried against COVID-19 because it is designed to disable the mechanism by which certain viruses, including the new coronavirus, make copies of themselves and potentially overwhelm their host's immune system.