ABSTRACT
T cells expressing chimeric antigen receptors have shown remarkable therapeutic activity against different types of cancer. However, their wider use has been hampered by the potential for life-threatening toxicities due to the unintended targeting of healthy cells expressing low levels of the targeted antigen. We have now developed an affinity-tuning approach for the generation of minimally modified, low-affinity antibody variants derived from existing high-affinity antibodies. Using this approach, we engineered low affinity variants of the fully human CD229-specific antibody 2D3. Parental 2D3 originally efficiently targeted multiple myeloma cells but also healthy T cells expressing low levels of CD229. We demonstrate that CAR T cells based on a low affinity variant of 2D3 maintain the parental antibody’s anti-tumor activity, but lack its targeting of healthy T cells. In addition, variant CD229 CAR T cells show reduced trogocytosis potentially augmenting CAR T cell persistence. The fast off-rate CAR produced using our affinity tuning approach eliminates a key liability of CD229 CAR T cells and paves the way for the effective and safe treatment of patients with multiple myeloma.
One sentence summary Affinity tuning approach yields low affinity CD229 CAR binding domain maintaining the parental clone’s anti-tumor activity while eliminating killing of healthy T cells, increasing CAR T cell expansion, and decreasing trogocytosis.
Competing Interest Statement
ERV, TL, and DA are inventors on provisional patent application 63/285843 describing low-affinity CD229 antibodies and CAR T cells. SVR, DA, and TL are inventors on PCT application US2017/42840 'Antibodies and CAR T Cells for the Treatment of Multiple Myeloma' describing the therapeutic use of CD229 CAR T cells for the treatment of multiple myeloma.