UCLA researchers in the Department of Microbiology Immunology and Molecular Genetics have developed a nanobody-based CAR T cell platform with increased stability and cross-immunogenicity between human and mouse antigens.
BACKGROUND:
Chimeric antigen receptor (CAR) T-cell therapy makes use of reengineered T cells to target and clear cancer cells. Conventional CAR-T cell therapy begins by collecting T-cells from patients; then, in a laboratory setting, the cells are genetically modified to express a CAR molecule on their surface. A large population of these designer cells are then reintroduced back into the patient where they attack and kill cancer cells expressing the molecule targeted by the CAR. The current clinically approved CAR-T cell products all utilize single-chain variable fragments (scFvs) as the extracellular binding domain. ScFvs confer target recognition and specificity of CAR-T cells to antigen-expressing tumor cells. However, one of the major limitations is species-specific reactivity to the antigen of interest which hampers clinical development. Consequently, CARs that only recognize human antigens cannot be used in immunocompetent murine models to study interactions with endogenous immunity and the tumor microenvironment.
INNOVATION:
Researchers at UCLA have engineered nanobody-based CARs against Mesothelin (MSLN), an antigen in which scFv-based CARs have been developed for and have been tested in the clinic against cancers such as ovarian, pancreatic, and lung cancer. Nanobodies are composed of only a heavy-chain variable domain (VHH), typically derived from antibodies from camelid species. Nanobodies are designed to be smaller, more stable, and have reduced immunogenicity compared to conventional scFvs. These properties allow for greater transduction efficiency to further increase efficacy of CAR-T cell therapies. Furthermore, the specific nanobody used in the MSLN CAR developed by the Chen lab is capable of cross-recognition between human and mouse antigens, thus allowing for in-depth preclinical studies in immunocompetent mouse models. With the implementation of the nanobody engineering platform, the MSLN CAR enables effective antigen-specific lysis of both MSLN positive human and murine tumor cells in vitro. The MSLN CAR-T cells also demonstrate high anti-tumor activity in a murine ovarian cancer model, demonstrating its potential use in preclinical animal studies.
POTENTIAL APPLICATIONS:
- Nanobody-based CAR-T cell platform
- Cross-immunogenic reagent for human and mouse studies
ADVANTAGES:
- Reduction in size for increased transfection efficiency and increased opportunity for co-expression of additional transgenes
- Cross-immunogenicity between human and mouse antigens enables in-depth characterization of interaction with endogenous immunity in immunocompetent mouse models
- Increased stability for more effective anti-tumor activity
DEVELOPMENT-TO-DATE:
Researchers have built a panel of MSLN CARs using various MSLN-binding scFvs and nanobodies. A nanobody-based lead candidate has been confirmed to bind both murine and human MSLN and confer control of human and murine cancer cells.