Abatacept in Immune Checkpoint Inhibitor Myocarditis

This investigator-initiated randomized trial is being conducted to test whether abatacept, as compared to placebo, is associated with a reduction in MACE among participants who develop myocarditis after treatment with an ICI. Immune checkpoint inhibitors leverage the immune system to treat a wide variety of cancers. Myocarditis is an uncommon immune related adverse event (irAE) secondary to treatment with an ICI. The guideline recommended treatment for ICI myocarditis is cessation of the ICI and administration of corticosteroids. However, despite administration of corticosteroids, the rate of MACE with ICI myocarditis is high. Data from multiple independent international cohorts have shown that the rate of MACE with ICI myocarditis despite administration of corticosteroids ranges from 25-50%.For comparison, the rate of MACE with myocarditis unrelated to an ICI is \<5%. Abatacept is a selective co-stimulation modulator that inhibits T cell (T lymphocyte) activation by binding to CD80 and CD86, thereby blocking its interaction with CD28. This interaction provides a costimulatory signal necessary for full activation of T lymphocytes. In animal studies of ICI myocarditis, the administration of abatacept led to a reduction in cardiac immune activation and an increase in survival. In retrospective unpublished clinical data, the administration of abatacept to participants with ICI myocarditis on corticosteroids was associated with a reduction in risk of MACE. There are no prospective studies testing whether abatacept is effective among participants with ICI myocarditis. Therefore, the primary aim of this trial is to test in a randomized double-blind placebo-controlled study whether abatacept, administered concurrently with corticosteroids, is associated with a reduction in MACE among participants with recently diagnosed ICI myocarditis