Investing.com -- Elanco Animal Health Inc. (NYSE:ELAN) stock rose 7% after the company was set to join the S&P MidCap 400 index, effective prior to the opening of trading on Tuesday, September 2. The animal health company will replace Sarepta Therapeutics Inc. (NASDAQ:SRPT) in the S&P MidCap 400, while Sarepta will move to the S&P SmallCap 600, replacing Brookline Bancorp Inc. (NASDAQ:BRKL). The index changes come as S&P SmallCap 600 constituent Berkshire Hills Bancorp Inc. (NYSE:BHLB) is acquiring Brookline Bancorp in a transaction expected to be completed soon. Following the merger, Berkshire Hills Bancorp will remain in the S&P SmallCap 600 but will undergo a name and ticker change to Beacon Financial Corp. (NYSE:BBT). Index inclusion typically benefits companies by increasing their visibility to investors and potentially boosting liquidity in their shares. Funds that track the S&P MidCap 400 will need to purchase Elanco shares to maintain proper index weighting, which likely contributed to today's stock price increase. The changes to both indices will take effect before markets open on September 2, 2025, according to the announcement. This article was generated with the support of AI and reviewed by an editor. For more information see our T&C.