This is an interesting question. I was speaking with a melanoma specialist yesterday and he said because you have colitis with IPI does not mean you will have it with PD1. On the contrary, it is not one of the side effects, and should not preclude you from having PD1.
Here is a report from ASCO regarding folks who had problematic side effects with ipi, but went on the tolerate Nivo well. From additional reports, those who take pembro subsequent to ipi are doing similarly.
Updated survival, toxicity, and biomarker of nivolumab with/without peptide vaccine in patients naive to, or progressed on, ipilimumab
Abstract 3009, J Clin Oncol
Weber, Kudchadkar, Gibney, et al.
105 patients with unresectable melanoma, who had failed at least one regimen were enrolled and given nivo at 1, 3, or 10mg/kg. 34 patients were ipi naive. 10 patients had failed ipi with grade 2 or less adverse events. 20 patients had filed ipi with grade 3/4 adverse events. All of these patients were HLA A0201 positive and were given peptide vaccines along with nivo. 41 patients had grade 2 or less ipi reactions and were not HLA restricted and were given nivo alone. Median f/u was 15 months. Median progression free survival was 4.2 months. Median overall survival was 16.7 months, with a one year survival of 65%. Median overall survival was similar for ipi naive or ipi refractory. Of 20 patients with grade 3/4 ipi reactions, only one had a subsequent grade 3/4 nivo reaction and it was different from the one experienced on ipi. Conclusion: Median overall survival of 16.7 months with nivo was observed in previously treated melanoma patients naive to or failing ipi. Prior adverse effects to ipi were not replicated with nivo.