Check out the companies making headlines after the bell Monday:
Sarepta shares surged in after-hours trading, after the Food and Drug Administration requested more data before making a decision on eteplirsen. Eteplirsen's approval has been mired in challenges, as regulators have debated whether the treatment for Duchenne muscular dystrophy, has had adequate clinical drug trial results amid changing guidelines for compassionate use.
Shares of Alexion Pharmaceuticals tumbled in extended trading after the company announced results from a study of one of its drugs. The company revealed that at week 26 of the study, a key efficacy measure missed its endpoint for statistical significance. The drug, Soliris, treats a neuromuscular disease that causes slurred speech, impaired swallowing and choking, double vision, weakness, disabling fatigue, shortness of breath and episodes of respiratory failure, according to the company.
Whole Foods inched higher after the bell, building on gains from the regular session. A bullish Barron's report published Saturday said the stock could return 20 percent over the next year, adding that the launch of its new 365 value chain unlocks a new market for the company.
United National Foods' shares also popped after the organic, natural and specialty food distributor posted better-than-expected quarterly earnings. The company reported third fiscal quarter earnings of 76 cents per share, higher than the 66 cents per share predicted by a Thomson Reuters consensus estimate. Earnings and revenue guidance for the year were also above Wall Street's estimates.
"Over the last several months our team has worked to significantly expand UNFI's fresh produce, specialty products and service offerings with the acquisitions of Nor-Cal, Global Organic and Haddon House Food Products," CEO Steven Spinner said.
Still, United National Foods' third quarter revenue fell short, coming in at $2.13 billion, versus $2.16 billion estimates.
— CNBC's Fred Imbert contributed to this report.