Gilead Sciences Inc. cut the company’s 2020 revenue forecast, citing lower-than-expected demand and difficulty in predicting sales of remdesivir, the only treatment approved in the United States for patients hospitalized with Covid-19.

Vir Biotechnology Inc. plans to start a mid-to-late stage trial of the company’s Covid-19 drug candidate in August, as drugmakers across the globe rush to find treatments for the highly infectious virus.