Targeting CCR1/CCR2 attenuates cytokine release syndrome while preserving CAR T-cell antitumor activity

Cytokine release syndrome (CRS) is a major dose-limiting toxicity of chimeric antigen receptor (CAR) T-cell therapy, yet the upstream mechanisms driving macrophage activation remain incompletely understood. Here, we established a xenograft model of human CAR T-cell therapy that recapitulates key features of CRS and combined single-cell RNA sequencing (scRNA-seq) with pharmacological intervention to define the inflammatory programs underlying CRS. CAR T-cell treatment induced dose-dependent systemic inflammation and remodeled the host myeloid compartment, leading to the accumulation of a distinct population of CRS-associated macrophages. Analysis of clinical scRNA-seq datasets from CAR T cell–treated glioblastoma patients confirmed enrichment of the CRS-associated macrophage gene signature following therapy in patients, supporting the clinical relevance of our findings. Transcriptomic analyses identified marked upregulation of the chemokine receptors CCR1 and CCR2 together with activation of CCL3- and CCL2-associated signaling pathways. Pharmacological inhibition of CCR1 and CCR2 significantly reduced clinical CRS, inflammatory cytokine production, and macrophage activation while preserving CAR T-cell expansion, effector cytokine production, and in vivo antitumor efficacy. These findings identify CCR1/CCR2-dependent chemokine signaling as a critical regulator of macrophage-driven CRS and support chemokine receptor blockade as a promising strategy to improve the safety of CAR T-cell therapy without compromising therapeutic efficacy.