Modular in vivo antibody-ADC click to reverse drug resistance in tumours

Antibody-drug conjugates (ADCs) have significantly advanced cancer therapy by enabling the selective delivery of cytotoxic agents to tumour cells. However, ADC efficacy remains constrained by its dependence on a single target antigen, which limits tumour targeting and promotes resistance in heterogeneous tumours with variable and low antigen expression^1-6. Here we introduce an in vivo bioorthogonal ligation strategy that generates functional antibody-ADC click constructs following systemic administration. This platform provides a modular and translatable approach for enhanced targeted drug delivery in heterogeneous tumours. We conjugate therapeutic antibodies and ADCs with trans-cyclooctene and tetrazine moieties for sequential administration to enable in vivo ligation of an antibody with an ADC after systemic delivery. The antibody-ADC click approach demonstrated improved antitumour activity relative to standard ADC monotherapy or antibody plus ADC combinations in preclinical models of HER2 and EGFR co-expression. These included tumours with low, ultralow, negative or heterogeneous HER2 expression and resistant or ineligible for conventional HER2-directed ADCs. This modular strategy leverages receptor biology and bioorthogonal chemistry for optimal therapeutic efficacy and does not require extensive antibody re-engineering. Moreover, the antibody-ADC click approach can be extended to other receptor pairs, which makes it a flexible modular platform to address heterogeneity and resistance to targeted therapies across different tumour types.