Two-Stage CD8⁺ CAR T-Cell Differentiation in Patients with Large B-Cell Lymphoma

Area of Science:

• Immunotherapy
• Cellular Therapy
• Oncology

Background:

• Chimeric antigen receptor (CAR) T-cell therapy offers new treatment avenues for diffuse large B-cell lymphoma (DLBCL).
• Understanding CAR T-cell differentiation is crucial for improving patient outcomes but remains incomplete.
• Axicabtagene ciloleucel is a key CAR T-cell therapy used in DLBCL treatment.

Purpose of the Study:

• To investigate the in vivo differentiation of CAR T cells in DLBCL patients treated with axicabtagene ciloleucel.
• To analyze the clonal expansion, phenotype, and ontogeny of CAR T cells longitudinally.
• To elucidate the mechanisms underlying CAR T-cell expansion and persistence.

Main Methods:

• Single-cell, multimodal, and longitudinal analyses were performed on CAR T cells.
• Samples were collected from infusion products and peripheral blood of DLBCL patients (day 8-28).
• Lineage tracing using endogenous TCR clonotypes was employed to track CAR T-cell origins.

Main Results:

• CD8+ CAR T cells exhibited two distinct waves of clonal expansion.
• The first wave (day 8-14) showed an exhausted-like effector memory phenotype during peak expansion.
• The second wave (day 21-28) displayed a terminal effector phenotype during post-peak persistence.
• Lineage tracing revealed that the two waves originate from distinct precursors in the infusion product: effector-like for the first wave and stem-like for the second.
• Pre-infusion heterogeneity in CAR T-cell populations drives these distinct expansion waves.

Conclusions:

• CAR T-cell expansion and persistence are mediated by clonally, phenotypically, and ontogenically distinct cell populations.
• These distinct CAR T-cell populations have complementary roles in clinical efficacy.
• The findings challenge the notion that post-peak CAR T-cell contraction is solely due to apoptosis or extravasation of short-lived cells.