The PD-L1 analyses in the trial had some limitations, Dr. Balar said. “PD-L1 testing continues to be the most hotly contested issue,” he said. “Obviously, the immune system is very dynamic, and we were testing something in archival specimens, in a static environment, so there are obviously all the caveats there.”
Some data have suggested that mutational burden may help identify the patient subset who will benefit. However, “to be able to make your decision in the clinic, those types of readouts need to be timely …, and I think that’s the gap,” he commented. “So in the future, is the right biomarker PD-1 or PD-L1? My hunch is no, that is probably not the right biomarker, there are probably better ones, and those are being worked on.”
Dr. Balar disclosed that he has a consulting or advisory role with Cerulean Pharma, Dendreon, Pfizer, and Roche/Genentech. The trial was sponsored by Hoffmann-La Roche. Ventana Medical Systems assisted with PD-L1 testing.