Background Nectin-4 is a Ca²⁺ independent immunoglobulin-like protein that is primarily involved in cell-cell adhesion. Nectin-4 is overexpressed in several tumor types, including breast, lung, urothelial, colorectal, pancreatic, and ovarian cancers. Overexpression of Nectin-4 is associated with multiple aspects of tumor progression such as proliferation, angiogenesis, epithelial to mesenchymal transition, metastasis, DNA repair and tumor relapse. This overexpression is correlated with poor prognosis, making Nectin-4 an attractive target for developing new therapeutic strategies for cancer. As a result, a substantial number of antibody drug conjugates targeting Nectin-4 are under development. Most of these therapies, however, display a high rate of drug related toxicities accentuating the need for alternative approaches for anti-cancer therapeutics targeting Nectin-4.

Methods We leveraged BioAtla’s Conditionally Active Biologic (CAB) platform to develop a dual CAB T cell engager (TCE) bispecific antibody targeting Nectin-4 and CD3 receptors (CAB-Nectin-4 x CAB-CD3 bispecific antibody). The dual CAB Nectin-4 x CD3 bispecific antibody was engineered to bind with high affinity to both Nectin-4 and CD3 receptor antigens under conditions that mimic the acidic tumor microenvironment, but with lower binding activity in physiological (alkaline) conditions.

Results Our data demonstrate that the dual-CAB bispecific antibody promotes cytotoxicity of Nectin-4-expressing cancer cells in vitro and induces complete tumor regression in vivo. Further, the dual CAB Nectin-4 x CD3 bispecific antibody has higher potency in inducing primary T cell activation measured by means of cytokine release and cancer cell cytotoxicity under acidic conditions compared to the non-CAB benchmark bispecific antibody. In non-human primates, a single dose of the dual-CAB bispecific antibody was well-tolerated at a dose of 5 mg/kg. Non-CAB Nectin4 x CD3 bispecific antibody was also well tolerated at a dose of 5mg/kg but induced high levels of IL-6, while the CAB Nectin-4 x CAB CD3 bispecific antibody induced minimal IL-6 cytokine response.

Conclusions The generation of CAB T-cell engagers (TCEs) with activity in the disease microenvironment minimizes on-target, off-tumor toxicities, thereby enabling TCEs with strong anti-tumor activity and increased tolerability for potentially enhanced therapeutic index in the clinic.