The bankruptcy of Steward Health has become the latest cautionary tale about private equity’s involvement in health care. Cerberus Capital Management’s purchase in 2010 of several Massachusetts-based nonprofit hospitals was meant to be a life preserver for the struggling chain, but instead its woes deepened, compromising patient care.

Merck & Co. has said nothing publicly about rumors that it is in talks to buy Seagen, a biotech company working on cancer treatments, for about $40 billion.