CXCR4-modification enhances CAR-T efficacy by improving tumor tracking and bone marrow homing in B-cell malignancies

Hematological malignancies of B cell origin are characterized by frequent expression of CXCR4. The CXCR4-CXCL12 axis facilitates the in vivo dissemination of B cell lymphoma and multiple myeloma (MM). It is also a pivotal regulator in the migration and bone marrow homing of T cells. Herein, we hypothesized that engineering CAR-T cells to overexpress CXCR4 could utilize the CXCR4-CXCL12 axis to enhance their therapeutic efficacy by increasing tumor tracking and bone marrow accumulation. In this study, we found that lentiviral transduction caused significant CXCR4 downregulation on T cells, leading to impaired CAR-T cell migration to CXCL12. By contrast, CXCR4 overexpressing (CXCR4^hi) CD19 CAR-T cells and BCMA CAR-T cells showed superior in vivo tumor tracking and clearance capacities in the localized and systemically disseminated models of B cell lymphoma and MM, respectively. Notably, CXCR4 modification significantly facilitated the bone marrow homing and accumulation of CAR-T cells, which further promoted memory T cell differentiation, persistence and prolonged antitumor activity. Building on these findings, an investigator-initiated clinical trial (IIT) evaluating CXCR4^hi CD19 CAR-T cells in patients with relapsed/refractory B cell malignancies (NCT04684472) achieved encouraging efficacy: the low-dose cohort yielded 3 complete responses (CRs) and 1 partial response (PR) within the first month post-infusion. These findings support the use of CXCR4 modification as a strategy to improve CAR-T cell efficacy in treating hematologic B cell malignancies, warranting further clinical investigation.