U.S. stock indexes closed solidly higher Friday, with some of the upbeat mood on Wall Street to start October and the fourth quarter being attributed to an experimental COVID-19 pill from Merck & Co. /zigman2/quotes/209956077/composite MRK -0.95% that has shown in trials that it helps prevent high-risk people early in the course of the disease from becoming seriously ill and dying. The Dow Jones Industrial Average /zigman2/quotes/210598065/realtime DJIA -1.30% rose 1.4% to 34,326, with gains in Visa /zigman2/quotes/203660239/composite V -3.93% , Microsoft Corp. /zigman2/quotes/207732364/composite MSFT -1.85% , Walt Disney & Co. /zigman2/quotes/203410047/composite DIS -6.94% and American Express Co. /zigman2/quotes/203805826/composite AXP -1.35% helping power the gains for the price-weighted index, along with Merck. The S&P 500 index /zigman2/quotes/210599714/realtime SPX -1.89% rose 1.2% to 4,357, with energy shares surging 3.3% to lead the S&P 500's 11 sectors to start the month where that sector ended September, on top. The Nasdaq Composite Index /zigman2/quotes/210598365/realtime COMP -2.72% closed 0.8% higher at 14,566. For the week, however, the Nasdaq closed down 3.2% and the S&P 500 ended off 2.2% for their worst weekly declines since Feb. 26, while the Dow ended the week off 1.4% for the sharpest weekly slide since Sept. 10, FactSet data show. as investors displayed a little risk appetite, thinking a new page in the calendar might push the market past the issues that drove it down earlier in the week.