Check out which companies are making headlines after the bell Tuesday:
Affiliated Managers Group - The company is set to join the S&P 500, replacing Forest Laboratories. The change is expected to take place after the closing of trading on June 30.
Bristol-Myers Squibb - The company announced a study of a drug to treat a type of melanoma was stopped early because of evidence showing superior overall survival in patients receiving the drug, nivolumab, versus the control drug.
Vertex Pharmaceuticals - Shares continued to climb on news a combination of its drugs to treat cystic fibrosis improved lung function in a pair of late-stage clinical trials.
Walgreen - The drugstore chain fell in after-hours trade, continuing a drop that began after the drugstore chain reported disappointing quarterly results ahead of Tuesday's open.
Whole Foods Market - Shares of the specialty grocer gained after Morgan Stanley initiated coverage with an "overweight" rating.
—By CNBC's Kate Gibson.
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