What happened At times, the reason or reasons behind a stock's rise are obscure or mysterious. But that certainly wasn't the case with Collegium Pharmaceutical (NASDAQ: COLL) on Tuesday, which shot 9.8% higher thanks to a development that should dramatically raise its profile. So what Collegium, a biotech that has enjoyed success with its pain relief medication Xtampza ER, is about to become a component of the S&P stock index family. Late Monday, S&P Dow Jones Indices -- the operator of the famous suite of indexes -- announced a change in its benchmark S&P 500 index. Image source: Getty Images. S&P 500 index component TechnipFMC is getting the boot and being replaced by Monolithic Power Systems. The latter is currently in the S&P MidCap 400 index, so its slot there will be filled by Iridium Communications. Iridium is now on the S&P SmallCap 600 index, thus a replacement is needed for its position; Collegium is that replacement. The move is slated to take effect this Friday, Feb. 12. Now what Inclusion on a notable stock index, particularly one with the characters "S&P" in front of it and particularly for a less-known business like Collegium, instantly raises its visibility. It also, crucially, attracts the many index funds that prowl S&P lineups for their portfolios. Naturally, greater prominence and attention doesn't necessarily mean an endless stock price lift -- Collegium still has to deliver for shareholders. But this is an extremely positive development for a company that has performed well lately. 10 stocks we like better than Collegium PharmaceuticalWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Collegium Pharmaceutical wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of November 20, 2020 Eric Volkman has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source