Shares of Gilead Sciences Inc. /zigman2/quotes/210293917/composite GILD -0.68% were down 1.2% in trading on Monday after the drugmaker said it plans to start Phase 1 clinical trials for an inhaled version of remdesivir, its treatment for severely ill COVID-19 patients. An intravenous version of the drug received an emergency use authorization from the Food and Drug Administration in May. The new study will first test this version of the investigational medication in healthy patients before moving on to COVID-19 patients. It is thought that an inhaled drug would be easier to administer outside of a hospital setting. "That could have significant implications in helping to stem the tide of the pandemic," CEO Daniel O'Day said in a letter on Monday. O'Day also said Gilead plans to test whether remdesivir can help patients before they become severely ill, in vulnerable patient populations like children and pregnant women, and in combination with other therapies, including Eli Lilly & Co. /zigman2/quotes/200106384/composite LLY +0.44% and Incyte Corp.'s /zigman2/quotes/204510994/composite INCY -4.98% Olumiant and Roche Holdings' /zigman2/quotes/206324342/delayed CH:ROG +1.84% Actemra. "We have been keen to explore how remdesivir might work when combined with anti-inflammatory agents, particularly in the most severely ill patients," he wrote. Gilead's stock is up 17.9% year-to-date, while the S&P 500 /zigman2/quotes/210599714/realtime SPX -1.40% is down 4.1%.