Fully human CD19-specific chimeric antigen receptors for T-cell therapy

Area of Science:

• Immunology
• Oncology
• Biotechnology

Background:

• Adoptive transfer of CD19-specific chimeric antigen receptor (CAR) T-cells has shown success in treating B-cell malignancies.
• Immune responses against murine single-chain variable fragments (scFv) in CARs can lead to CAR T-cell elimination and tumor relapse.

Purpose of the Study:

• To generate fully human CD19-specific scFvs with binding characteristics similar to the murine FMC63 scFv.
• To construct and evaluate novel CAR T-cells using these human scFvs to reduce immunogenicity and improve efficacy.
• To assess the safety and efficacy of human CAR T-cells in preclinical models.

Main Methods:

• Generated fully human scFvs using human antibody DNA libraries.
• Constructed various CAR formats with human scFvs and transduced primary human T-cells.
• Assessed CAR T-cell activation against CD19-positive cell lines and primary chronic lymphocytic leukemia cells.
• Evaluated tumor elimination in human lymphoma xenografts in immunodeficient mice.
• Performed imaging to analyze CAR T-cell surface distribution and signaling.

Main Results:

• Fully human CD19-specific CAR T-cells were generated and demonstrated specific activation against CD19-positive targets.
• These human CAR T-cells effectively eliminated human lymphoma xenografts in vivo.
• Certain fully human CAR constructs outperformed the widely used murine FMC63-based CAR.
• No evidence of CAR T-cell clustering or tonic signaling was observed with human CARs.
• Modified fusion sites further reduced potential immunogenicity.

Conclusions:

• Fully human CD19-specific CARs offer a promising alternative to murine-based CARs, potentially reducing immune rejection.
• These novel CAR constructs may enhance the safety and durability of CAR T-cell therapy for B-cell malignancies.
• The developed human CARs are suitable for targeting validated clinical targets, with potential for reduced adverse immune responses.