Shares of Merck & Co. gave up their regular session gains after hours Tuesday when the drugmaker said it was halting a study of an Alzheimer's drug because it did not appear to be working. Merck shares fell 1.5% to $64.69 after hours, following a 1.4% gain in the regular session. Merck said it stopped a clinical study of the drug verubecestat because a data monitoring committee said there was "virtually no chance of finding a positive clinical effect" for the drug under the study protocol. A different study of the drug for Alzheimer's, however, will continue, Merck said.
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