Shares of Teva Pharmaceutical Industries Ltd. /zigman2/quotes/205657894/composite TEVA -1.26% gained 13% in premarket trading on Friday following a Thursday night announcement that the drugmaker will donate more than 6 million doses of hydroxychloroquine sulfate tablets in the U.S. this month. Chloroquine, a longtime malaria drug that is sometimes used as a treatment for rheumatoid arthritis, is being floated as a potential treatment for people sickened by the novel coronavirus by the Trump administration. Teva said in a news release that the drug, which has not received Food and Drug Administration approval as a treatment for COVID-19, has been requested by government officials in efforts to treat the disease. Bayer AG /zigman2/quotes/203424967/delayed BAYRY +1.08% and Mylan /zigman2/quotes/209413137/composite MYL +1.71% have also said they will produce chloroquine therapies as a result of the COVID-19 pandemic. Teva's stock is down 29.9% year-to-date, while the S&P 500 /zigman2/quotes/210599714/realtime SPX -0.80% has dropped 25.4%.