结合拓扑异构酶I抑制剂和微管抑制剂的HER2靶向双载荷抗体偶联药物在异种移植模型中展现出优异疗效并克服对单载荷ADC的耐药

The genetic and phenotypic heterogeneity of human cancers is a primary driver of drug resistance, posing a major challenge to achieving durable therapeutic responses. To overcome this, Sutro has developed a dual-payload antibody-drug conjugate (dpADC) platform that enables precise co-delivery of two cytotoxic payloads via a single, homogeneous molecule. Sutro's HER2-targeting dpADC demonstrates that simultaneous delivery of two cytotoxic payloads provides greater anti-tumor activity than single-payload ADCs and overcomes preclinical, in-vivo-derived treatment resistance. Combining Sutro Biopharma's XpressCF+® cell-free expression system with site-specific conjugation technology, we engineered a HER2-targeting dpADC combining exatecan (topoisomerase I inhibitor; TOPO1i) and monomethyl auristatin E (MMAE) (microtubule inhibitor; MTi) payloads at an 8:4 ratio. The resulting dpADC exhibited favorable pharmacokinetics in vivo and minimal linker-payload loss over a 21-day study. In in vitro cell killing assays, the dpADC performed better than Enhertu and DAR8 exatecan ADC across multiple tumor cell lines. In in vivo efficacy studies, the dpADC exhibited greater anti-tumor activity than both single-payload ADC comparators across multiple xenograft models. To further evaluate the dpADC concept's potential, we examined its utility in addressing resistance induced by ADC treatment. To mimic resistances to single payload ADCs observed in the clinic, we continuously dosed xenograft tumors with Enhertu on a weekly dosing schedule until the tumors progressed. These Enhertu-resistant tumors were then continuously dosed with a MTi ADC until de novo resistance developed. Dual-resistant tumors were then treated with a dpADC resulting in deep and durable anti-tumor responses. Even in tumors that were rendered resistant to both payloads, the dpADC treatment was able to achieve substantial tumor regression, demonstrating the potential for benefit in mono payload ADC refractory settings. Overall, these results indicate that Sutro's HER2 dpADC can enhance anti-tumor activity beyond that of single-payload ADCs and can overcome prior treatment-induced resistance in a preclinical setting.