Abstract 388: AI/ML-driven discovery of a novel proteoglycan for precision targeting of ADCs for disruption of stromal barriers and direct anti-tumor activity

Abstract

Background: While checkpoint inhibitors (CPIs) such as anti-CTLA-4 and anti-PD-1/L1 have demonstrated efficacy in a number of solid tumor indications, those with high stromal presence have been difficult to treat with minimal response observed. We aimed to use a proprietary machine learning/artificial intelligence platform to identify novel stromal targets to relieve this immunosuppressive barrier and increase CPI responsiveness in difficult to treat indications. Methods: Based on bioinformatic analysis using our single cell RNA atlas, we assessed cancer-associated fibroblasts (CAFs)/fibroblastic cells in cancer tissue for identification of novel targets, including proteoglycans. Antibodies were generated by immunization of humanized mice, and lead antibodies were tested for activity in inhibiting cell adhesion and were further characterized for staining of both CAFs as well as tumor cells. ADCs were developed and tested in vitro for selective tumor cell killing. Results: Bioinformatic analysis identified a unique subset of cancer-associated fibroblasts, termed ecmCAFs, which demonstrated selective expression of Collagen Triple Helix Repeat Containing 1 (CTHRC1). This highly-selective expression pattern suggests it may be ideal as a target for alternative modalities, including ADC targeting or specific T cell activation. In addition, we identified that in certain tumor types, such a triple negative breast cancer and pancreatic ductal adenocarcinoma (PDAC), CTHRC1 is also highly expressed by cancer cells within the tumor and shows a more favorable expression profile for ADC targeting when compared to other stromal proteins such as FAP and LRRC15. We have confirmed surface expression and binding of CTHRC1 by our lead antibodies and have observed robust internalization on both human and mouse cancer cell lines. In vitro killing of tumor cells by ADCs and in vivo PD and efficacy will be presented on both ADCs and naked antibodies. Conclusions: We have identified CTHRC1 as a novel proteoglycan expressed by both ecmCAFs and tumor cells that appears to be an ideal target for both direct inhibition of stromal barrier function as well as targeting of cytotoxic payloads as an ADC. CTHRC1 expression is more selective than the classical markers FAP and LRRC15, both of which have been previously developed as ADCs. Citation Format: Elizabeth Koch, Max London, Amy Berkley, Allison Nixon, Sean Phippen, Kerry White, Amanda Hanson, Samuel Cooper, Christopher Harvey, Michael Briskin. AI/ML-driven discovery of a novel proteoglycan for precision targeting of ADCs for disruption of stromal barriers and direct anti-tumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 388.