Soluble CTLA-4 mutants ameliorate immune-related adverse events but preserve efficacy of CTLA-4– and PD-1–targeted immunotherapy

Immune checkpoint inhibitors (ICIs), such as nivolumab and ipilimumab, not only elicit antitumor responses in a wide range of human cancers but also cause severe immune-related adverse events (irAEs), including death. A largely unmet medical need is to treat irAEs without abrogating the immunotherapeutic effect of ICIs. Although abatacept has been used to treat irAEs, it risks neutralizing the anti–cytotoxic T lymphocyte–associated protein 4 (CTLA-4) monoclonal antibodies administered for cancer therapy, thereby reducing the efficacy of anti–CTLA-4 immunotherapy. To avoid this caveat, we compared wild-type abatacept and mutants of CTLA-4–Ig for their binding to clinically approved anti–CTLA-4 antibodies and for their effect on both irAEs and immunotherapy conferred by anti–CTLA-4 and anti–PD-1 antibodies. Here, we report that whereas abatacept neutralized the therapeutic effect of anti–CTLA-4 antibodies, the mutants that bound to B7-1 and B7-2, but not to clinical anti-CTLA-4 antibodies, including clinically used belatacept, abrogated irAEs without affecting cancer immunotherapy. Our data demonstrate that anti–CTLA-4–induced irAEs can be corrected by provision of soluble CTLA-4 variants and that the clinically available belatacept may emerge as a broadly applicable drug to abrogate irAEs while preserving the therapeutic efficacy of CTLA-4–targeting ICIs.