Dual‐Targeting of the HER2 Cancer Receptor with an Antibody‐Directed Enzyme and a Nanobody‐Guided MMAE Prodrug Scaffold

Abstract

Antibody‐enzyme conjugates have shown potential as tissue‐specific prodrug activators by antibody‐directed enzyme prodrug therapy (ADEPT), but the approach met challenges clinically due to systemic drug release. Here, we report a novel dual‐targeting ADEPT system (DuADEPT) which is based on active cancer receptor targeting of both a trastuzumab‐sialidase conjugate (Tz‐Sia) and a highly potent sialidase‐activated monomethyl auristatin E (MMAE) prodrug scaffold. The scaffold is based on a four‐way junction of the artificial nucleic acid analog acyclic (L)‐threoninol nucleic acid ((L)‐aTNA) which at the ends of its four arms carries one nanobody targeting HER2 and three copies of the prodrug. Dual‐targeting of the constructs to two proximal epitopes of HER2 was shown by flow cytometry, and a dual‐targeted enzymatic drug release assay revealed cytotoxicity upon prodrug activation specifically for HER2‐positive cancer cells. The specific delivery and activation of prodrugs in this way could potentially be used to decrease systemic side effects and increase drug efficacy, and utilization of Tz‐Sia provides an opportunity to combine the local chemotherapeutic effect of the DuADEPT with an anticancer immune response.