mSA2 affinity-enhanced biotin-binding CAR T cells for universal tumor targeting.

Chimeric antigen receptor T cells (CAR-Ts) are promising cancer therapeutics. However, since cancer cells can lose the CAR-targeted antigen and avoid destruction, targeting multiple antigens with multiple CARs has been proposed. We illustrate here a less cumbersome alternative, anti-tag CARs (AT-CARs) that bind to tags on tumor-targeting antibodies. We have created novel AT-CARs, using the affinity-enhanced monomeric streptavidin 2 (mSA2) biotin-binding domain that when expressed on T cells can target cancer cells coated with biotinylated antibodies. Human T cells expressing mSA2 CARs with CD28-CD3ζ and 4-1BB-CD3ζ signaling domains were activated by plate-immobilized biotin and by tumor cells coated with biotinylated antibodies against the tumor-associated antigens CD19 and CD20. Furthermore, mSA2 CAR T cells were capable of mediating cancer cell lysis and IFNγ production in an antibody dose-dependent manner. The mSA2 CAR is a universal AT-CAR that can be combined with biotinylated tumor-specific antibodies to potentially target many different tumor types.

Antibodies elicited by the first non-viral prophylactic cancer vaccine show tumor-specificity and immunotherapeutic potential.

MUC1 is a shared tumor antigen expressed on >80% of human cancers. We completed the first prophylactic cancer vaccine clinical trial based on a non-viral antigen, MUC1, in healthy individuals at-risk for colon cancer. This trial provided a unique source of potentially effective and safe immunotherapeutic drugs, fully-human antibodies affinity-matured in a healthy host to a tumor antigen. We purified, cloned, and characterized 13 IgGs specific for several tumor-associated MUC1 epitopes with a wide range of binding affinities. These antibodies bind hypoglycosylated MUC1 on human cancer cell lines and tumor tissues but show no reactivity against fully-glycosylated MUC1 on normal cells and tissues. We found that several antibodies activate complement-mediated cytotoxicity and that T cells carrying chimeric antigen receptors with the antibody variable regions kill MUC1(+) target cells, express activation markers, and produce interferon gamma. Fully-human and tumor-specific, these antibodies are candidates for further testing and development as immunotherapeutic drugs.