Do you consider alternate therapy with a different anti-PD1 agent after a patient responds to an anti-CTLA4 +/- anti-PD1 agent but develops serious side effects?

The short answer is no. Pembro and Nivo are essentailly the same drug and in all the studies, once the patient has developed grade 3 toxicity the treatment is complete because further dosing will result in even more severe toxicty. The only exception is for endocrinopathies which can be managed with...