Immune-checkpoint-inhibitor (ICI)–associated myotoxicity involves the heart (myocarditis) and skeletal muscles (myositis), which frequently occur concurrently and are highly fatal. We report the results of a strategy that included identification of individuals with severe ICI myocarditis by also screening for and managing concomitant respiratory muscle involvement with mechanical ventilation, as well as treatment with the CTLA4 fusion protein abatacept and the JAK inhibitor ruxolitinib. Forty cases with definite ICI myocarditis were included with pathologic confirmation of concomitant myositis in the majority of patients. In the first 10 patients, using recommended guidelines, myotoxicity-related fatality occurred in 60%, consistent with historical controls. In the subsequent 30 cases, we instituted systematic screening for respiratory muscle involvement coupled with active ventilation and treatment using ruxolitinib and abatacept. The abatacept dose was adjusted using CD86 receptor occupancy on circulating monocytes. The myotoxicity-related fatality rate was 3.4% (1/30) in these 30 patients versus 60% in the first quartile (P < 0.0001). These clinical results are hypothesis-generating and need further evaluation. Significance: Early management of respiratory muscle failure using mechanical ventilation and high-dose abatacept with CD86 receptor occupancy monitoring combined with ruxolitinib may be promising to mitigate high fatality rates in severe ICI myocarditis. See related commentary by Dougan, p. 1040. This article is highlighted in the In This Issue feature, p. 1027

While multiple pharmacological drugs have been associated with myocarditis, temporal trends and overall mortality have not been reported. Here we report the spectrum and main features of 5108 reports of drug-induced myocarditis, in a worldwide pharmacovigilance analysis, comprising more than 21 million individual-case-safety reports from 1967 to 2020. Significant association between myocarditis and a suspected drug is assessed using disproportionality analyses, which use Bayesian information component estimates. Overall, we identify 62 drugs associated with myocarditis, 41 of which are categorized into 5 main pharmacological classes: antipsychotics (n = 3108 reports), salicylates (n = 340), antineoplastic-cytotoxics (n = 190), antineoplastic-immunotherapies (n = 538), and vaccines (n = 790). Thirty-eight (61.3%) drugs were not previously reported associated with myocarditis. Antipsychotic was the first (1979) and most reported class (n = 3018). In 2019, the two most reported classes were antipsychotics (54.7%) and immunotherapies (29.5%). Time-to-onset between treatment start and myocarditis is 15 [interquartile range: 10; 23] days. Subsequent mortality is 10.3% and differs between drug classes with immunotherapies the highest, 32.5% and salicylates the lowest, 2.6%. These elements highlight the diversity of presentations of myocarditis depending on drug class, and show the emerging role of antineoplastic drugs in the field of drug-induced myocarditis.

Immune-checkpoint inhibitors (ICI) have revolutionized cancer therapy but are associated with infrequent but lethal myocarditis, for which management remains uncertain. Abatacept, a CTLA-4 fusion protein targeting CD86 on antigen presenting cells and leading to global T-cell anergy, has been described as a potential treatment in individual reports. Yet, abatacept treatment dosage, schedule and optimal combination with other immunosuppressive therapies are unclear. We describe a 25-year-old man who developed pembrolizumab (anti-PD1)-induced myocarditis 14 days after first injection for thymoma treatment, which deteriorated into cardiogenic shock, with sustained ventricular arrhythmia, requiring urgent extracorporeal life support implantation, despite prompt initiation of corticosteroids and mycophenolate-mofetil. Using a strategy of serial measurement ensuring with a target of >80% CD86 receptor occupancy on circulating monocytes, abatacept dose was adjusted and combined with ruxolitinib and methylprednisolone. This strategy resulted in high-dose of abatacept: 60 mg/kg in three doses (20 mg/kg each) within the first 10 days, followed by two doses. Clinical improvement occurred within 7 days, with resolution of systolic cardiac dysfunction, and ventricular arrhythmias resulting in successful discharge from hospital. We reversed a case of nearly lethal ICI-myocarditis, using specific patient-dose adjusted abatacept, which may serve as basis for personalized treatment of patients with severe ICI-adverse events. Trial registration number: NCT04294771.