Case report of fatal immune-mediated myocarditis following treatment with davoceticept (ALPN-202), a PD-L1-dependent CD28 costimulator and dual PD-L1/CTLA-4 checkpoint inhibitor, in combination with pembrolizumab.

Engagement of programmed death-1 (PD-1) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) can interfere with the CD28 signaling requisite for T-cell activation. While immune checkpoint inhibitors (ICIs) can relieve this suppression, they are unable to drive CD28 costimulation that may mechanistically contribute to ICI resistance. Thus, CD28 costimulation in the context of checkpoint inhibition may activate immunosuppressed T-cells in the tumor microenvironment. Davoceticept (ALPN-202) is an Fc fusion of a CD80 variant immunoglobulin domain (vIgD) designed to mediate PD-L1-dependent CD28 costimulation while inhibiting the PD-L1 and CTLA-4 checkpoints. PD-L1-restriction of davoceticept's CD28 costimulatory activity may minimize systemic T-cell activation and avoid untoward systemic toxicities. At the same time, preclinical studies have suggested that treatment with davoceticept during PD-1 inhibition may enhance antitumor activity by upregulating PD-L1, potentially synergizing with davoceticept's PD-L1-dependent costimulatory mechanism. This report details two cases of fatal cardiac events following treatment with davoceticept in combination with pembrolizumab (anti-PD-1) in the phase 1 study, NEON-2. Both events occurred in females in their 60s; one with choroidal melanoma and prior immunotherapy, the other with ICI-naïve microsatellite stable colorectal cancer. The clinical courses were fulminant with symptom onset at 2 weeks, followed by rapid decline. Cardiac autopsy from one patient confirmed immune-related myocarditis, and immunosequencing revealed expansion of a single T-cell clone that was not present in the pretreatment tumor. These cases highlight the importance of understanding risk factors that may contribute to immune-related myocarditis and other severe immune-related adverse events when CD28 agonism is targeted in the context of checkpoint inhibition.NEON-2 (NCT04920383).