CTLA4 and myocarditis: In contrast, a pharmacovigilance study identified myocarditis in 18 of 20,594 patients (0.09%) treated with nivolumab alone or in combination with ipilimumab (13), and a cohort study of 964 patients from a multicenter registry reported a prevalence of 1.14%, which increased to as high as 2.4% for combination therapy with anti-PD-1/anti-CTLA-4 (44).