Patient-derived anti-Siglec-6 antibodies engineered into T cell-recruiting bispecific antibody formats for treating leukemia

ABSTRACT: Despite numerous therapeutic options, safe and curative therapy is out of reach for most chronic lymphocytic leukemia (CLL) patients. We previously reported the identification of a patient-derived CLL-binding antibody, JML-1, and identified Siglec-6 as the target of JML-1. Siglec-6 is an attractive target for cancer immunotherapy due to its absence on healthy tissues and potential role in immune signaling. In this work, we identify additional patient-derived anti-Siglec-6 antibodies, RC-1 and RC-2, that bind with higher affinity than JML-1, yet exhibit similar specificity and overlapping conformational epitopes. Both JML-1 and RC-1 were employed to generate anti-Siglec-6 x anti-CD3 T cell-recruiting bispecific antibodies (T-biAbs) which were effective in vitro at activating T cells and lysing target cells. Upon engineering RC-1 into more compact and rigid T-biAb formats, we achieved sub-pM EC50 values for cell lysis in vitro. In addition, the T-biAbs mediated the killing of primary CLL cells by autologous T cells at natural effector-to-target cell ratios ex vivo. The increased potency of this T-biAb format appears to be due to the reduction in the length and/or flexibility of the cytolytic synapse. Furthermore, the anti-Siglec-6 x anti-CD3 T-biAb was effective at curing mice in a systemic in vivo model of CLL.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Valentine Courouble  

LAB HEAD: Christoph Rader

PROVIDER: PXD029601 | Pride | 2022-12-19

REPOSITORIES: Pride