Bristol-Myers Squibb ( BMY ) tumbled to the bottom of the S&P 500 today after the company said it would not try to get a quick approval from the FDA for its lung cancer treatment . Bristol-Myers Squibb dropped 11% to $49.23, while the S&P 500 advanced 0.3% to 2,271.31. Morgan Stanley's David Risinger and team call is a "perplexing disappointment." They explain why: