Merck & Co., Inc. (NYSE:MRK)'s talks to buy cancer-drug maker Seagen Inc. (NasdaqGS:SGEN) have stalled for now, threatening what would be the pharmaceutical giant's biggest deal in more than a decade, according to people familiar with the matter. The companies have so far failed to agree on a price, said the people, who asked not to be identified because the information was private. The talks could still resume and possibly yield an agreement, the people said.