CD28 Co-Stimulus Achieves Superior CAR T Cell Effector Function against Solid Tumors Than 4-1BB Co-Stimulus

Area of Science:

• Immunology
• Oncology
• Biotechnology

Background:

• Chimeric antigen receptor (CAR) T cell effector function is influenced by construct design, including spacer and co-stimulatory domains.
• Preclinical models are crucial for selecting optimal CAR T cell candidates for clinical trials.
• Species-specific factors can limit the efficacy of CAR T cells in traditional xenograft models.

Purpose of the Study:

• To evaluate the impact of different spacer and co-stimulatory domains on CAR T cell performance in a human tumor xenograft model.
• To compare CAR T cell trafficking, expansion, and tumor control mediated by CD28 versus 4-1BB co-stimulation.
• To assess the efficacy of CAR T cell designs targeting L1CAM and HER2 antigens in solid tumors.

Main Methods:

• Utilized a "mouse-in-mouse" model with murine CAR T cells and human tumor xenografts to overcome species-specific limitations.
• Compared CAR T cells with identical constructs differing only in spacer (long/short) or co-stimulatory (CD28/4-1BB) domains.
• Assessed CAR T cell trafficking, in vivo expansion at the tumor site, and tumor regression in neuroblastoma and ovarian carcinoma xenograft models.

Main Results:

• CAR T cells incorporating CD28 co-stimulation demonstrated superior trafficking to tumors compared to those with 4-1BB.
• L1CAM-targeting CAR T cells with a short spacer and CD28 co-stimulation showed the greatest expansion and induced initial tumor regression.
• The superiority of CD28 co-stimulation was confirmed in both L1CAM-targeting neuroblastoma and HER2-targeting ovarian carcinoma xenografts.

Conclusions:

• CD28 co-stimulatory signaling significantly enhances CAR T cell efficacy in solid tumors.
• Incorporating CD28 signaling into CAR design is recommended for improving adoptive T cell therapy for solid tumors.
• The developed "mouse-in-mouse" model effectively supports the pre-clinical evaluation of CAR T cell constructs.