Only a few months after reporting what it called “unprecedented” phase I data for its BCR-ABL1 tyrosine kinase inhibitor in chronic myeloid leukemia, Terns Pharmaceuticals Inc. agreed to an acquisition by Merck & Co. Inc. valued at about $6.7 billion. For Terns, the deal validates the decision last year to switch focus from its metabolic pipeline to oncology and, for Merck, it’s the latest move as the big pharma looks to shore up its offerings ahead of patent expirations for cancer blockbuster drug Keytruda (pembrolizumab).