Gilead Sciences (NASDAQ:GILD) appears to have hit another roadblock in its race to defeat COVID-19. The company is reportedly having trouble recruiting enough test subjects for its clinical trial of a drug candidate to fight the coronavirus.

According to an article published Tuesday in The Wall Street Journal, Gilead had intended to involve nearly 800 COVID-19 patients in the trial taking place in Wuhan, China, the city at the epicenter of the disease's outbreak. However, the company has only been able to sign up 185 people who qualify. Of those volunteers, 168 presented with severe symptoms, while the remainder presented with moderate or mild ones.

The clinical trials of the pharmaceutical company's antiviral treatment, remdesivir, were first announced Feb. 5. Citing China's state news agency, the Journal said that it was hoped that 761 patients would take part, the bulk of them with severe cases.

All participants were required to test positive for the COVID-19 virus. The severe patients were required to be within 12 days of the onset of COVID-19 symptoms, and have not taken medication for it within the preceding 30 days. The moderate and mild trial subjects had to be within eight days of the onset of the illness. Those requirements might be limiting the patient pool for the trial, as apparently many people with symptoms have already begun taking treatments.

Remdesivir was originally developed to treat the Ebola and Marburg viruses, although it has proven relatively ineffective against the former.

Gilead has not yet officially responded to the article, but the report does not seem to be of great concern to investors. The company's stock closed Tuesday trading less than 1% lower.