Abstract B002: A study on the relationship between ex vivo drug sensitivity and clinical outcome of acute lymphoblastic leukemia

Abstract Novel immune-cellular target therapies have been actively developed and introduced in the real-world treatment of acute lymphoblastic leukemia (ALL). However, we are still using multi-agent chemotherapy to reduce the initial tumor burden and facing many relapsed or refractory (R/R) patients with poor survival outcomes. In this study, we measured the ex vivo sensitivity of patient-derived cells to as many as 21 different anti-cancer drugs and assessed their prognostic utility. The results confirmed a strong utility of the drug sensitivities in predicting clinical outcomes. Out of 37 ALL patients who participated, we performed ex vivo DS analysis on 27 patients (9 Ph-negative, 14 Ph-positive, and 4 T-ALL at diagnosis (n=17) and at relapse (n=10)) using bone marrow aspirates. Briefly, the isolated blast cells were incubated for 72 hours with various concentrations of up to 21 anti-cancer drugs, and changes in viability were measured using the Alamar Blue assay. For each drug, we calculated the individual patient’s drug sensitivity in terms of the three metrics—IC50, area under the curve (AUC), and Emax (the remaining viability at the highest concentrations). Smaller values of IC50, AUC, and Emax correspond to high drug sensitivities. After sample acquisition, all patients received one of the following therapies: Modified hyper-CVAD (cyclophosphamide, vincristine, doxorubicin, dexamethasone, n=6) plus tyrosine kinase inhibitors (n=8) or L-asparaginase (n=2), inotuzumab ozogamicin (n=3), tyrosine kinase inhibitor (TKI) alone (n=3), blinatumomab (n=2), chimeric antigen receptor T-cells (CAR-T, n=1), and others (n=2). Complete response was achieved in 24 patients (89%), and minimal residual disease (MRD) was observed in 16 (67%) among the responders. During the follow-up, with median of 22 months, there were 3 refractory and 2 relapsed patients, 4 succumbed to death in remission, and 3 died due to leukemia progression. Given the various disease subtypes and treatment modalities, we focused on the patients with available DS analysis results treated with modified hyper-CVAD +/- imatinib/L-asparaginase (n=16) for further analysis. Upon evaluating the predictive utility of the drug sensitivity metrics, we found that the Emax of cyclophosphamide or other alkylating agents (melphalan, busulfan or ifosfamide) was effective (ROC-AUC of 1.00, n=6) in predicting early disease-progression (<3 months) of Ph+ ALL. On the other hand, the Emax of decitabine was effective (ROC-AUC of 1.00, n=5) in predicting early disease progression of Ph- B-ALL. For T-ALL, the Emax of multiple drugs—decitabine, alkylating agents including cyclophosphamide, and mitoxantrone—were effective in predicting early disease progression (ROC-AUC of 1.00, n=2). Furthermore, the unsupervised clustering of the drug AUCs was effective in predicting MRD positivity (ROC-AUC of 0.85, n = 27). In conclusion, we report that our proprietary ex vivo drug sensitivity platform may have clinical utility in identifying ineffective therapy for ALL patients across multiple subtypes and/or settings. Citation Format: Sung-Soo Park, Sungwon Lim, Seunghyok Ham, Seongjun Lee, Sesun Park, Hyoju Yi, Seok Lee, Jae-Ho Yoon, Jamin Koo. A study on the relationship between ex vivo drug sensitivity and clinical outcome of acute lymphoblastic leukemia [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Functional and Genomic Precision Medicine in Cancer: Different Perspectives, Common Goals; 2025 Mar 11-13; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(5 Suppl):Abstract nr B002.