Gilead Sciences CEO Daniel O’Day said in an open letter Saturday that the company is expanding access to its experimental anti-coronavirus drug remdesivir to include severely ill COVID-19 patients.The big pig picture: President Trump has called the antiviral drug "promising," but the results of six clinical trials on this investigational medicine are still being conducted, so its effectiveness in the treatment of the novel coronavirus has yet to be proved. The World Health Organization is involved in the tests."With expanded access, hospitals or physicians can apply for emergency use of remdesivir for multiple severely ill patients at a time."Excerpt from O’Day's statementGilead Sciences temporarily stopped granting emergency access requests for remdesivir from individual patients outside the trials "due to an overwhelming demand" last Sunday.Zoom in: The firm has moved from its "compassionate use" program to one of "expanded access" because "the system cannot support and process the overwhelming number of applications we have seen with COVID-19," O'Day said.Children and pregnant women would still have access via the "compassionate use" program, which has seen the drugmaker provide remdesivir to more than 1,000 patients, per O'Day's letter.Establishing the safety and efficacy of this investigational medicine is essential before it can be distributed for use worldwide, O'Day noted.What's next: The company hopes to have initial data from the trials in the coming weeks."If it is approved, we will work to ensure affordability and access so that remdesivir is available to patients with the greatest need," O'Day said.Go deeper: Special status for coronavirus drug caught health officials off guardInside a coronavirus drug delayOver 100 drugs are in testing in the race to treat coronavirusNew testing for coronavirus emerges from MERS, Ebola anti-virals