Bispecific antibodies and CAR T cells targeting a TP53 mutation-associated neoantigen show discordant affinity requirements

Data deposited here are the sequencing data of scFv from the affMat
reported in the study below: Mutation-associated neoantigens (MANAs) are
highly cancer-specific targets for immunotherapy when peptides derived
from intracellular mutant proteins are presented on the cell surface via
HLA molecules. T cell-engaging bispecific antibodies and CAR T cells can
target MANAs to eliminate cancer cells via T-cell activation. However, the
low antigen density of MANAs on the cell surface can limit therapeutic
efficacy. Here, we investigated whether increasing the affinity of the H2
single-chain variable fragment (scFv) targeting the p53 R175H MANA
(HMTEVVRHC presented on HLA-A*02:01) improves its therapeutic effect. We
identified higher-affinity H2 variants via phage biopanning and a
thiocyanate elution method. Increasing bispecific antibody affinity to the
low nanomolar range increased cancer cell killing and tumor control in
mouse xenograft models without sacrificing antigen specificity. We next
asked how increasing scFv affinity impacts CAR T cell function—a matter of
debate. We appended each variant scFv to a CD28z CAR, CD3 gamma, or the
T-cell receptor (TCR). In striking contrast to the bispecific antibody
results, increasing CAR affinity decreased function in each CAR format due
to lower T-cell activation upon interaction with target cancer cells.
These results have important implications for the design of future
immunotherapeutic approaches targeting low-density antigens.