AACR 2019 – Establishment of a patient-derived acute myeloid leukemia (AML) ex vivo platform for evaluation of novel therapeutic agents

Title

Establishment of a patient-derived acute myeloid leukemia (AML) ex vivo platform for evaluation of novel therapeutic agentsAuthors

Authors

Bhavna Verma, Swetha Tati, Bruce Ruggeri, Amy Wesa

Abstract

Acute myelogenous leukemia (AML) is the most common acute leukemia in adults. A hematologic cancer, the disease is highly heterogeneous, with multiple subtypes. Despite advances in treatment, the long-term survival for AML remains poor and the development of novel treatments is an unmet need. Due to the highly divergent subtypes and mutation profiles in AML, the use of patient-derived models may improve drug discovery and development. To address this, we have established a short-term culture system that supports the growth of primary AML cellsex vivoto permit the evaluation and/or screening of candidate agents. Our AML bank is comprised of patient-derived specimens across a range of subtypes (which includes M1, M2, M4, M5, and others), and includes models with common mutations in FLT3 (ITD), IDH1/IDH2 and NPM. Primary AML specimens were characterized for common mutations by TruSightsequencing and for surface marker expression by flow cytometry. Theex vivoassay system was evaluated for the ability to support the survival and expansion of 22 primary AML specimens. Among these, 15 had evidence of proliferation, 5 had no net expansion, and 2 failed to survive. Extension of the culture period for up to 14 days was feasible, with most models having equal or increased cell numbers by the end of the culture period (8 of 10 evaluated). All models stably expressed CD33 throughout the assay. To verify the applicability of this system for drug testing, a standard of care agent cytarabine (Ara-C) was assessed for each of the AML models. Cell growth/viability was assessed using CellTiter-Glo assay. Concentration-dependent responses to Ara-C were observed across multiple models (IC5010 nMto 150 nM), indicating a range of relatively sensitive to resistant AML models. A cohort of models were evaluatedin vivofor sensitivity to Ara-C. Engraftment of the systemic patient-derived xenograft AML models (into NOG or NOG-EXL mice) was evaluated in circulation by flow cytometry. When engrafted, AML-bearing mice were randomized into Ara-C or vehicle control groups. Two weeks later, mice were evaluated for the presence of human CD45+CD33+AML cells. Models that were relatively sensitive to Ara-C ex vivo (IC50< 30 nM) showed a greaterin vivo response as evidenced by a 60-80% reduction in the mean circulating AML cells versus models with >100 nMIC50values, that had little response. In conclusion, Champions offers over 30 well characterized models of AML for study inex vivo culture andin vivo systemic xenograft models. The diversity in these AML models is reflective of patient diversity, enhancing their utility in the evaluation of novel therapeutic candidates. These data indicate the feasibility of utilization of these primary models,ex vivoas well asin vivo,for drug discovery for AML, from screening to preclinical efficacy modeling.