There’s no real difference in response rate. And I would say there’s no clinically significant differences in toxicity profile, including autoimmune side effects.

— Paul Mitchell, MD

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“This is a very important systematic review,” commented invited discussant, Paul Mitchell, MD, Associate Professor at the Olivia Newton-John Cancer and Wellness Centre in Melbourne, Australia.

“There are theoretical reasons why programmed cell death ligand 1 (PD-L1) inhibitors might cause less toxicity,” he noted. Specifically, unlike agents that target programmed cell death protein 1, those that target PD-L1 do not affect the interaction with PD-L2, which could translate to fewer adverse effects.

General Messages

The meta-analysis reassuringly confirms that overall, both PD-1 and PD-L1 inhibitors have low toxicity, less than that seen with chemotherapy, according to Dr. Mitchell. “The general messages are that severe toxicity is unusual with these agents. There’s no real difference in response rate,” he summarized. “And I would say there’s no clinically significant differences in toxicity profile, including autoimmune side effects.”

“Toxicity, though, will become more of an issue as we embark on more combination immunotherapy studies and combination chemoimmunotherapies become more widely used,” Dr. Mitchell predicted. ■

Disclosure: Dr. Mitchell is on the advisory boards of Bristol-Myers Squibb, Merck, AstraZeneca, Roche, and Celgene; has received travel grants from Bristol-Myers Squibb and Roche; and has received honoraria from Roche, Bristol-Myers Squibb, AstraZeneca, and Merck.