Abstract 5092: Development of a priming approach to enhance antigen-directed therapies in hematological malignancies and solid tumors

Abstract

Abstract Clinical success of antigen-directed therapies in cancer has been limited by heterogeneous antigen expression and a narrow therapeutic window. In many patients, failure of antigen-directed therapies such as CAR T-cell therapies, antibody-drug conjugates (ADC) or radioligand therapies (RLT) has less to do with a lack of potency or specificity of the agent and more to do with variable and suboptimal antigen expression in the patient. We are developing combination therapies that introduce a priming agent designed to optimize antigen expression in the patient and improve the therapeutic window of existing antigen-directed therapies. Our high-throughput platform utilizes machine learning and automation to scale functional combinatorial screening for small molecule priming agents using cell lines and patient samples. Using this platform, we are identifying priming therapies for CD123, CD33, CD22, and CD19 in hematological malignancies including acute myeloid leukemia (AML), and HER2, HER3, and TROP2 in solid tumors including breast cancer.For our CD123 program, we have identified priming agents that selectively upregulate CD123 expression ≥2-fold on AML cells without increasing expression on normal myeloid progenitor cells, which also express CD123. AML cells treated with a CD123 priming agent in combination with a CD123 ADC showed greater tumor-cell killing compared to the ADC alone. In comparison, normal myeloid progenitor cells from healthy bone marrow treated with the same CD123 priming-ADC combination treatment did not show an increase in ADC-mediated cell killing. From our mechanistic studies, we have identified a somatic mutation associated with CD123 upregulation that may lead to selective upregulation on cancer cells and not on normal cells. Additionally, this marker can be used for patient selection. We have also observed CD123 upregulation in vivo using mouse models of AML and are currently conducting additional in vivo proof of concept studies to demonstrate that CD123 priming therapy enhances efficacy.There are two distinct advantages of a priming approach paired with an antigen-directed therapy, which include: (1) improving the durability of patient responses and (2) expanding the patient population. Our priming combination approach has the potential to overcome antigen heterogeneity and thereby improve the clinical success of antigen-directed therapies. Citation Format: Kathryn E. Vanderlaag, Anukriti Dhar, Molly Volkman, Erik Werner, Transon Nguyen, Kamran Ali. Development of a priming approach to enhance antigen-directed therapies in hematological malignancies and solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5092.