SAN FRANCISCO - As the number of clinical trials testing checkpoint inhibitors in combination immunotherapies climbs ever-skyward, efforts to find ideal synergies have met both disappointments and challenges. Executives in the thick of efforts to identify the next best moves in the field highlighted some of the setbacks and the need to set aside haste in favor of careful science, to be open to new possibilities and to re-examine which endpoints might provide the best measures in new trials.