As Merck reportedly eyes a $6 billion deal for Terns Pharmaceuticals ahead of Keytruda's patent cliff, analysts debate its upside against Sellas Life Sciences. While SLS offers an estimated 73% upside compared to TERN's 16%, TERN benefits from takeover rumors. SLS awaits a Phase 3 readout, whereas Merck sees a $70 billion opportunity beyond Keytruda.