The National Institute of Allergy and Infectious Diseases (NIAID) said Friday it is testing Gilead Sciences Inc.'s /zigman2/quotes/210293917/composite GILD -0.33% remdesivir in combination with Eli Lilly & Co.'s /zigman2/quotes/200106384/composite LLY -0.48% rheumatoid arthritis drug Olumiant in COVID-19 patients as part of the next phase of the randomized, controlled clinical trial that led to the authorization of remdesivir. This study will enroll 1,000 people at more than 100 sites in the U.S. and abroad, to "examine if adding an anti-inflammatory agent to the remdesivir regimen can provide additional benefit for patients," NIAID director Dr. Anthony Fauci said in a statement. The topline results from the remdesivir trial helped make up the basis of the Food and Drug Administration's (FDA) emergency use authorization for the drug last week. A number of medicines that have been previously approved by the FDA to treat rheumatoid arthritis have been proposed as possible COVID-19 treatments, including Regeneron Pharmaceuticals Inc. /zigman2/quotes/203149337/composite REGN -0.56% and Sanofi's /zigman2/quotes/201967021/composite SNY -1.02% Kevzara and Roche Holding AG's /zigman2/quotes/206324342/delayed CH:ROG -0.24% Actemra. Olumiant, which was developed by Incyte Corp. /zigman2/quotes/204510994/composite INCY -0.78% and is licensed to Lilly, brought in $427 million in sales in 2019 for the Indianapolis-based drugmaker. Only two types of therapies - remdesivir and hydroxycholorquine and chlorquine - are authorized by the FDA as COVID-19 treatments. Year-to-date, Gilead's stock has gained 18.6%, while shares of Lilly are up 16.6%. The S&P 500 /zigman2/quotes/210599714/realtime SPX +0.42% is down 10.8%.