Keytruda taught Merck how to build a blockbuster. But manufacturing a 2nd lightning bolt is easier said than done

That dichotomy between Keytruda’s multibillion-dollar status and signs of deficiencies put an emphasis on the company’s ambitions. For now, the plan is twofold: Get Keytruda, a PD-1 checkpoint inhibitor, into earlier lines of treatment and continue to pursue a variety of combinations.