T-cell chromatin states reflect individual differences in <i>ex viv</i> o cytokine release and cytotoxicity induced by T-cell engager ERY22 in cynomolgus monkeys

T-cell engager therapies, including CD3-bispecific antibodies, have demonstrated potent antitumor activity but frequently cause cytokine release syndrome (CRS). CRS is a systemic inflammatory response characterized by high levels of circulating cytokines and immune-cell hyperactivation, with symptoms ranging from mild features such as fever and fatigue to severe, life-threatening conditions including shock and multiorgan failure. Currently, both prophylactic measures and prompt post-onset treatment are essential for therapy with T-cell engagers. Although CRS mitigation strategies reduce its incidence and severity, marked interindividual variability in CRS remains: Some patients show no symptoms, whereas others develop severe symptoms under identical preventive measures. This study aimed to elucidate the mechanisms underlying the interindividual variability in cytokine release and cytotoxicity following stimulation with a T-cell engager. We used ERY22, a T-cell engager developed as a monkey surrogate of the human therapeutic candidate ERY974, an anti-GPC3/CD3 T-cell engager. ERY22 has been previously reported to induce severe CRS in cynomolgus monkeys following in vivo administration. When PBMCs from 16 cynomolgus monkeys and GPC3-expressing target cells were co-cultured ex vivo with ERY22, there was substantial interindividual variability in cytokine production and cytotoxicity. We hypothesized that epigenetic states in T cells modulate these responses; accordingly, we profiled pretreatment T-cell chromatin accessibility using ATAC-seq. Interindividual variability in cytokine production and cytotoxicity correlated with chromatin accessibility at loci associated with these processes. These findings advance understanding of personalized risk prediction and management of CRS in clinical settings.