Detection of antibody-drug conjugate target expression on tumor-derived extracellular vesicles circulating in blood plasma of oncology patients.

Abstract

e14549 Background: Antibody-drug conjugates (ADCs) are a novel class of biotherapeutics designed to target tumor associated antigens using monoclonal antibodies to deliver a cytotoxic payload. ADCs enable precision targeting of tumor cells, resulting in increased targeted destruction of cancer cells with minimal off target cytotoxicity. Due to the immense promise of ADCs, hundreds of targets are undergoing investigation in clinical trials. Challenges in ADC clinical studies include determining which patients are likely to benefit from treatment, as well as monitoring therapeutic efficacy. Particularly in solid tumors, ADC protein target expression in tumor tissue biopsy can be difficult to assess due to tissue accessibility or inconsistencies with immunohistochemistry quantitation. Improved methods for patient stratification and response monitoring are urgently needed to aid in development of ADCs. Methods: Blood-based liquid biopsy is an ideal method to overcome these challenges in ADC development because it is minimally invasive, amenable to serial collection, and feasible where tumor tissue is not available. The most common liquid biopsy approaches utilize cell-free circulating tumor DNA or circulating tumor cells. These methods are hindered by unfavorable signal to noise ratios and do not provide proteomic expression data representative of a heterogeneous tumor site. As a promising alternative, extracellular vesicles (EVs) are lipid membrane encapsulated particles carrying diverse protein, nucleic acid, and metabolite cargos. Blood of cancer patients contains EVs from healthy cells and tissues throughout the body but also contains a population of EVs derived directly from tumor tissue. These tumor-derived EVs (TDEVs) serve as rich sources of insight into tumor biology and disease pathology. To detect TDEVs amongst background noise, we have developed a clinically applicable, multi-omic EV subpopulation interrogation pipeline that robustly profiles TDEV proteomes and transcriptomes in plasma. Results: The pipeline identifies activation of pathways driving oncogenesis and detects cancer markers, including ADC targets, across several cancers. We demonstrate detection of ADC targets in blood plasma TDEVs from non-small cell lung cancer (NSCLC) patients using LC-MS/MS proteomics. We show that protein expression of known ADC targets can vary dramatically from patient to patient. Comparison of proteomic data from NSCLC patients displaying high versus low TDEV protein expression levels of one highly disease relevant ADC target demonstrated differential expression of multiple markers associated with a particular cell signaling pathway in these two groups. Conclusions: This study demonstrates that TDEVs provide insight into ADC target dynamics in tumor tissue that could help overcome key challenges impeding ADC clinical studies.