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Stocks making the biggest moves after hours: GM, Snap, Merck and more

Nadine El-Bawab

Shares of Merck & Co MRK dropped as much as 9% in extended trading on Monday, before erasing those losses, after the pharmaceutical company announced that its medication Keytruda failed to meet expectations in phase 3 of the drug's trial. Shares of Snap SNAP ticked slightly higher after the company announced it has named a new chief financial officer to take over for interim CFO Lara Sweet, effective immediately. The social media company promoted Derek Andersen, Snap's current vice president of finance, to permanently fill the position of chief financial officer.