Merck & Co Inc said on Tuesday a large study of its Keytruda melanoma treatment will be stopped early because an independent monitoring committee determined the drug succeeded in its goal of prolonging survival in previously untreated patients with advanced melanoma. REUTERS: Merck & Co Inc said on Tuesday a large study of its Keytruda melanoma treatment will be stopped early because an independent monitoring committee determined the drug succeeded in its goal of prolonging survival in previously untreated patients with advanced melanoma.