In this photo illustration a Gilead logo is displayed on a smartphone on March 25, 2020 in Arlington, Virginia. Gilead announced on March 25, 2020 that it has submitted a request to the Food and Drug Administration to rescind the exclusive marketing rights it had secured for remdesivir, an antiviral drug that shows promise in treating Covid-19, the disease caused by the new coronavirus. Image Credit: AFP

Gilead Sciences Inc. said it's donating 1.5 million doses of its experimental anti-coronavirus drug remdesivir, which could treat 140,000 patients.

The drug will be offered for compassionate use, expanded access and clinical trials, and will treat patients with severe symptoms, Chairman and Chief Executive Officer Daniel O'Day said in an open letter. The company is also boosting its supply of remdesivir to more than 500,000 treatment courses by October, and to more than 1 million by the end the year. Production time has also been accelerated to six months from one year, he said.

"While we are working with the utmost sense of urgency on the immediate needs before us, we are also looking forward," he said. "Over the next weeks and months, we will be able to further increase our supplies of remdesivir as raw materials with long lead times become available for manufacture."

The drugmaker said last week it's switching to "expanded access" from a "compassionate use" program under which remdesivir was given. The move will accelerate its emergency use for multiple severely ill patients. More than 1,700 patients have been treated through these programs, O'Day said in the letter on Saturday.

A World Health Organization panel said in January that remdesivir was considered to be the most promising therapeutic candidate based on its broad antiviral spectrum, and existing data based on human and animal studies. The medication was developed initially for Ebola and studied in patients in Eastern Congo.

Multiple clinical trials are investigating the drug's effects in Covid-19 patients in China and elsewhere.