Reversing Drug Resistance in Tumors with Clickable Antibody Pairs

PROJECT SUMMARY/ABSTRACT – The incidence of gastric and breast cancers is increasing rapidly, rating fourth and fifth leading causes of cancer mortality worldwide. In patients clinically classified as HER2-positive (ERBB2 amplification and/or 2+/3+ protein overexpression by immunohistochemistry), antibody-drug conjugates (ADC) prolong progression-free and overall survival. However, these therapies have low activity in HER2-low cancer cells, and not all HER2-positive tumors benefit, or even those who initially respond inevitably develop resistance over time. Guided by preclinical data we obtained in HER2 heterogeneous patient-derived xenografts demonstrating that an increase in HER-ADC endocytosis enhances therapeutic efficacy, we developed approaches of antibody delivery that result in a 15.5-fold increase of ADC internalization in cancer cells. Our novel approach uses pertuzumab and trastuzumab-drug antibodies that click at the surface of cancer cells upon binding distinct HER2 domains to increase the number of HER2-ADC complexes and further enhance the rate of HER2-ADC endocytosis. Antibody-PET imaging studies that we have generated demonstrate that our approach increases the uptake of 89Zr-ADC in heterogeneous tumors containing HER2-high and HER2-low cancer cells. Here, we will optimize clickable pairs of two epitope-distinct antibody-ADC biomolecules to enhance tumor targeting and drug delivery in resistant models of breast and gastric cancer. In addition to test the potential of our approach in cancer cell lines and organoids, we will perform randomized imaging and therapeutic studies in patient-derived breast and gastric xenografts representing three tumor populations: ADC-eligible tumors of HER2 heterogeneity, ADC-ineligible tumors, and ADC-resistant tumors. We will determine the molecular imaging (89Zr-Antibody PET), safety, pharmacokinetic profile, and therapeutic efficacy of ADC alone (no-click) versus ADC plus pertuzumab conjugated with clicking pairs (click). These randomized preclinical studies will allow us to identify molecular features that confer drug sensitivity or resistance to this promising investigational approach. Aim 1 will optimize pertuzumab/ADC clicking pairs with improved tumor uptake and drug delivery when compared with ADC monotherapies and Aim 2 will validate the use of antibody clicking pairs as a new therapeutic approach. The two aims will provide important new preclinical data on the use of antibody clicking pairs to enhance drug delivery, which could provide an excellent foundation for many future investigations, including the clinical translation of using clicking pairs to enhance drug delivery and the potential broader application to other membrane receptors and heterogeneous tumors. The long-term translational objectives of the studies proposed are to establish a foundation for a clinical trial using antibody clicking to prevent or delay drug resistance in patients with heterogeneous breast and gastric cancers.