Immune checkpoint inhibitors (ICIs) are broadly used in the treatment of different oncologic diseases. Nevertheless, the raising use of these drugs leads to the occurrence of rare but severe immune related adverse events. ICI induced myocarditis, which is often accompanied with myositis or myasthenia-like syndrome, occurs infrequently, but is fatal in up to 50% of cases.

We present here a patient in which the immune suppressive drug Abatacept, a fusion protein of human IgG1 and the extracellular CTLA-4 domain, was used to treat a severe case of ICI induced myocarditis. A 68-year old patient was treated with a single dosage of the PD-1 inhibitor pembrolizumab to treat thymus carcinoma. The patient initially complained about muscle pain, double vision, a reduced general condition and dyspnea according to NYHA II. Initially, high sensitive troponinT (hsTnT) as well as Creatinkinase (CK) showed obvious elevations (hsTnT: 1833 pg/ml, CK: 6288 U/l)). NTproBNP (2324 ng/l) showed a decent cardiac decompensation. A significant coronary vessel disease was ruled out by cardiac catheterization. Biopsies of the myocardium showed signs of CD3/CD8 positive myocardial inflammation. Cardiac MRI supported the diagnosis of myocarditis by atypical late gadolinium enhancement.

Despite of a high dose corticosteroid treatment, inflammation progressed. Cardiac biomarkers further raised (hsTNT: 3251 pg/ml, NTproBNP: 5627 ng/l) and deterioration of myasthenia-related symptoms lead to intubation and mechanical ventilation. 

According to the current position papers, plasmapheresis was initiated and immunoglobulins were administered. Since steroid tapering was not well tolerated, we administered Abatacept at day 13 after admission. HsTnT as well as NTproBNP droped significantly in the following days and symptoms of myasthenia markedly improved. Under Abatacept therapy, tapering of steroids was well tolerated.

Taken together, corticosteroids can sufficiently inhibit ICI induced myocarditis. In cases of steroid resistant ICI myocarditis Abatacept is able to specifically target ICI activated T-cell CTLA-4/PD-1/PD-L1. Possible limitation of Abatacept treatment are potential tumor promoting effects and possible infectious complications. However, Abatacept needs to be further evaluated for the treatment of complex cases of ICI induced myocarditis.