Potent and selective antitumor activity of a T cell-engaging bispecific antibody targeting a membrane-proximal epitope of ROR1.
Publication Type:Journal Article
Source:Proc Natl Acad Sci U S A, Volume 115, Issue 24, p.E5467-E5476 (2018)
Keywords:Animals, Antibodies, Bispecific, Antineoplastic Agents, CD3 Complex, Cell Line, Tumor, Crystallography, X-Ray, Epitopes, Humans, Immunotherapy, Jurkat Cells, K562 Cells, Mice, Rabbits, Receptor Tyrosine Kinase-like Orphan Receptors, Single-Chain Antibodies, T-Lymphocytes, Cytotoxic, Xenograft Model Antitumor Assays
<p>T cell-engaging bispecific antibodies (biAbs) present a promising strategy for cancer immunotherapy, and numerous bispecific formats have been developed for retargeting cytolytic T cells toward tumor cells. To explore the therapeutic utility of T cell-engaging biAbs targeting the receptor tyrosine kinase ROR1, which is expressed by tumor cells of various hematologic and solid malignancies, we used a bispecific ROR1 × CD3 scFv-Fc format based on a heterodimeric and aglycosylated Fc domain designed for extended circulatory and diminished systemic T cell activation. A diverse panel of ROR1-targeting scFv derived from immune and naïve rabbit antibody repertoires was compared in this bispecific format for target-dependent T cell recruitment and activation. An ROR1-targeting scFv with a membrane-proximal epitope, R11, revealed potent and selective antitumor activity in vitro, in vivo, and ex vivo and emerged as a prime candidate for further preclinical and clinical studies. To elucidate the precise location and engagement of this membrane-proximal epitope, which is conserved between human and mouse ROR1, the 3D structure of scFv R11 in complex with the kringle domain of ROR1 was determined by X-ray crystallography at 1.6-Å resolution.</p>