CDK4/6 inhibition enhances CAR-T cell therapy in solid tumors.

Area of Science:

• Immunology
• Oncology
• Pharmacology

Background:

• Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors enhance anti-tumor immunity and are potential adjuvants for cancer immunotherapies.
• While synergistic with immune checkpoint inhibitors, the combination of CDK4/6 inhibitors with CAR-T cell therapy is largely unexplored.

Purpose of the Study:

• To investigate the efficacy of combining trilaciclib (a CDK4/6 inhibitor) with CAR-T cell therapy in preclinical blood and solid cancer models.
• To elucidate the mechanisms underlying the combination's effects on CAR-T cell function and the tumor microenvironment.

Main Methods:

• In vitro assessment of trilaciclib's impact on human CAR-T cell cytotoxicity, metabolism, and expansion.
• In vivo evaluation of the combination therapy in RB-proficient and RB-deficient leukemia models, as well as solid tumor models (including immunocompetent mice).
• Mechanistic studies to analyze changes in tumor-infiltrating immune cells (T-regulatory cells, CD8+ CAR-T cells) and CAR-T cell tumor trafficking and function.

Main Results:

• In vitro, trilaciclib improved CAR-T cell cytotoxicity and metabolic fitness but reduced expansion.
• The combination was superior to monotherapy in RB-proficient leukemia and consistently more efficacious in solid cancer models.
• In solid tumors, combination therapy enhanced CD8+ CAR-T cell persistence, tumor trafficking, and cytotoxic function, while reducing tumor-infiltrating T-regulatory cells.

Conclusions:

• Trilaciclib combined with CAR-T cell therapy demonstrates significant efficacy in preclinical solid cancer models.
• The combination's success in solid tumors is linked to improved CAR-T cell function and persistence within the tumor microenvironment.
• This combinatorial approach holds potential as an effective treatment strategy for solid cancers.