The stock market performed well on Monday, with the Dow climbing 88 points and other major market benchmarks posting similar gains of roughly half a percent. Many investors were pleased with the continued advances in the crude oil market, where prices approached the $52-per-barrel level on news of potential supply constraints because of Russian production controls and measures from OPEC member nations. Yet even though the stock market rose and sent the Energy Select SPDR ETF (XLE -0.31%) up more than 1.5%, some stocks nevertheless lost substantial ground. Among the worst perfomers were Bristol-Myers Squibb (BMY 0.96%), Myriad Genetics (MYGN -0.70%), and Twilio (TWLO -0.55%).


Image source: Bristol-Myers Squibb.

Bristol faces a competitive setback

Bristol-Myers Squibb lost more than 10% after a tough weekend for the drug-maker. On one hand, the company's presentation at the European Society for Medical Oncology showed few signs of any positive signs for its Checkmate-026 trial of its Opdivo candidate treatment for a form of lung cancer. At the same time, competitor Merck (MRK -0.11%) announced much more encouraging trial data for its Keytruda lung-cancer drug, setting the stage for a competitive showdown in which the odds will be very much in Merck's favor. If Merck gets the upper hand, then it will be extremely difficult for Bristol's Opdivo to meet the expectations that its shareholders have for the drug, and that could put even further pressure on the drug-maker's shares going forward.

Analysts hit Myriad shares

Myriad Genetics dropped 12% in the wake of an analyst's downgrade of the genetic testing company's stock. Analysts at Ladenburg Thalmann downgraded shares of Myriad Genetics from neutral to sell. The current target price of $16 per share for the stock would imply even further downside from current levels, and investors are increasingly worried about potential competition. For instance, Myriad currently relies heavily on its BRACAnalysis test for breast and ovarian cancer, but some potential competitors believe that they can offer reduced pricing that could hurt Myriad's business model in the long run. The question is how long Myriad can ride its first-mover advantage, but the prospect of an end to its competitive moat is making some Myriad Genetics shareholders take a hard look at their shares today.

Twilio's early investors sell out

Finally, Twilio plunged 14%. The company said late Friday that it would register a follow-on public offering of stock, allowing several of its existing stockholders to liquidate all or part of their holdings in the company. Twilio expects to issue $50 million in new stock in the offering, with the proceeds going to the company. However, the remaining $350 million in offered shares would represent holdings of third-party shareholders, and Twilio won't see any of those proceeds. The move comes as somewhat of a surprise because lock-up provisions for the newly public company weren't set to expire until late December. Given the success that the smartphone messaging and video specialist's stock has seen, it's no surprise that institutional investors want to book profits, and for long-term investors who believe in the company's prospects down the road, the drop could represent a good opportunity for more investment.