AbataCept for the Treatment of Immune-cHeckpoint Inhibitors Induced mYocarditiS

Immune-checkpoint-inhibitors (ICI) have revolutionized treatment for about 20 cancer types. They unleash anti-tumor immune responses. Unfortunately, in 0.36-1.23% of patients, this activation can also lead to lethal immune-related adverse events (irAEs) that can affect any organ. Among those irAEs, ICI-induced myocarditis was the most frequently fatal with death rate reaching 50% in a large case-series of over 100 patients. Other severe irAEs are pneumonitis, hepatitis and neuromyotoxicities (myositis, myasthenia gravis-like syndrome) with death rates of 20-25%. Co-occurrence of irAEs affecting multiple organs is frequent (30% for myocarditis and myositis) as they share underlying mechanisms with macrophages and cytotoxic T-cell infiltrates leading to organ destruction.

While rigorous studies for the treatment of irAEs are lacking, consensus guidelines recommend treatment with high-dose corticosteroids with progressive tapering and withholding ICI. When symptoms and biological markers do not improve, other immunosuppressive drugs (mycophenolate-mofetil, methotrexate, cyclosporine, cyclophosphamide, azathioprine, antithymocyte globulin, infliximab, tocilizumab, and rituximab) can be considered, depending on organs affected. Intravenous immunoglobulin or plasmapheresis can also be considered. In patients developing myocarditis, available therapeutics produce poor results and the fatality rate (40-50%) has stagnated between 2014-2019 despite increasing glucocorticoids use. No treatment has been shown to improve this situation. Thus, better reversal agents' strategies are urgently needed in the context of the increasing use of ICI and of associated irAEs. Abatacept and belatacept (CTLA4-immunoglobulin fusion proteins) have very promising properties: they inhibit CD80/CD86 mediated T-cell co-stimulation at the level of dendritic-cells, thereby abrogating activation of the T-cells upstream of the CTLA4 and PD1/PDL1 pathways. "CTLA4 agonists" leads to global T-cell anergy with limited off-target effects, and specifically reverse ICI-activated pathways.

Abatacept is currently indicated in rheumatological disorders such as rheumatoid arthritis and belatacept is indicated in kidney rejection transplantation prophylaxis. In these latter indications, the circulating monocytes CD86 receptor occupancy (CD86RO) by "CTLA4 agonists" is a relevant pharmacodynamic biomarker of their clinical activity. The target CD86RO cut-off should be over 80%.

Confirming the rationale for "CTLA4 agonists" use in ICI-myocarditis, the investigators recently showed that abatacept was able to alleviate fatal myocarditis in CTLA4/PD1 genetic knock-out mice model. Finally, this group recently described the first cases of glucocorticoid-refractory myocarditis induced by nivolumab (anti-PD1) which resolved after treatment with abatacept. This success prompted the investigators to treat over 15 ICI-myocarditis patients in their institution and several other teams to use abatacept in ICI-induced myocarditis with encouraging results. Though, in their experience, initial doses of abatacept needed to promptly reach CD86RO≥80% in ICI-myocarditis setting were much higher than those needed in its usual indications. Due to abatacept slow time to onset, combination with ruxolitinib (a JAK inhibitor) on top of corticosteroids was also proposed in ICI myocarditis management with very promising results (ICI-myotoxicity related mortality dropped from 60% on corticosteroids + 2nd line abatacept to 3% in 1st line abatacept + ruxolitinib + corticosteroids (https://doi.org/10.1158/2159-8290.CD-22-1180).

This study is a dose-finding Phase II trial where 3 abatacept IV regimen (A-10 mg/kg; B-20 mg/kg and C-25 mg/kg at Day0, Day5+/-2, Day14+/-2) will be tested aiming at reaching promptly (after the first dose) and sustainably a CD86RO≥80% during the first 3 weeks of ICI-myocarditis management. The main objective is to find the lowest dose required to achieve a circulating monocytes CD86RO≥80% within the first week of treatment and sustainably over three weeks. The target population is all adult patients with cancer (all cancer types) treated by immune checkpoint inhibitors (anti-PD1, anti-PDL1, anti-CTLA4 monotherapies or combination) and presenting drug-induced myocarditis.

Abatacept will be added to the standard of care of these severe ICI myocarditis patients, which include preferentially prednisone and ruxolitinib, tapered as a function of the bio-clinical evolution of ICI-myocarditis.