Oct 1 (Reuters) - Wall Street"s main indexes opened higher on Friday as steep losses in September saw investors buying into cheaper sectors, while drugmaker Merck rose on marking progress in the development of an oral COVID-19 drug. The Dow Jones Industrial Average (.DJI) rose 86.78 points, or 0.26%, at the open to 33,930.70. The S&P 500 (.SPX) opened higher by 9.62 points, or 0.22%, at 4,317.16, while the Nasdaq Composite (.IXIC) gained 46.35 points, or 0.32%, to 14,494.93 at the opening bell.