The American Society of Clinical Oncology annual meeting provided the first opportunity to stack up data for competing immune checkpoint inhibitors targeting PD-1 or its ligand PD-L1. The efficacy for the most advanced agents in melanoma and lung cancer is nearly identical. But dosing convenience in melanoma and toxicity in NSCLC could be the deciding factors for doctors.

In both cases, very early data suggest Merck & Co. Inc. could have the advantage over Bristol-Myers Squibb Co. In lung cancer, AstraZeneca plc also compares favorably to BMS, so far.