Abstract CT077: Potential utility of minimal residual disease (MRD) to identify relapse in pediatric and young adult (AYA) B-cell acute lymphoblastic leukemia (B-ALL) patients treated with tisagenlecleucel
Authors: Pulsipher Michael A. , Han Xia , Quigley Máire , Kari Gabor , Rives Susana , Laetsch Theodore W. , Myers Gary D. , Hiramatsu Hidefumi , Yanik Gregory A. , Qayed Muna , Driscoll Timothy , Boyer Michael W. , Stefanski Heather , Buchner Jochen , Baruchel Andre , Bader Peter , Yi Lan , Kalfoglou Creton , Robins Harlan , Yusko Erik , Gorgun Gullu , Bleickardt Eric , Wong Stephane , Grupp Stephan A. 
Published: August 2019

Abstract
Background: Detection of MRD is an important predictor of patient outcome following treatment of B-ALL; importantly, MRD is emerging as a useful tool to detect early relapse, which may fulfill a key previously unmet clinical need. Objective: To evaluate the potential of MRD to predict morphologic relapse in pediatric and AYA patients with B-ALL.
Methods: Bone marrow (BM) and peripheral blood (PB) specimens at screening (pre-tisagenlecleucel infusion), post-infusion, and relapse from two B-ALL clinical trials (ELIANA [NCT02435849] and ENSIGN [NCT02228096]) were tested using immunoglobulin next-generation sequencing (IgNGS) and flow cytometry (FC). We assessed concordance between two MRD assays to determine which method could support early relapse detection and whether using PB with IgNGS was comparable with BM testing with FC.
Results: IgNGS was performed in 300 samples from 88 patients. 237 samples from 83 patients also had FC MRD results available. Baseline samples, which had high disease burden, showed 100% MRD concordance between both assays. However, post-treatment, where the leukemic burden was dramatically reduced, IgNGS detected a greater number of MRD-positive samples vs FC at each sensitivity level tested (10-4, 10-5, and 10-6). At the highest sensitivity level of 10-6, IgNGS was able to detect 18% more MRD-positive post-treatment samples. IgNGS was able to detect MRD positivity 1-4 months ahead of clinical relapse in a small number of relapsed patients, whether relapse was CD19+ or CD19-. MRD burden in BM was higher than in PB using both FC and IgNGS. In patients with matching data available, IgNGS was able to detect more MRD-positive PB samples than FC MRD-positive BM samples. Patients who were MRD negative by both IgNGS and FC at the end of first month post-infusion had better progression-free survival (PFS) and overall survival (OS) compared with those with detectable MRD. Tumor clonality at baseline and clonal evolution following tisagenlecleucel treatment will be presented.
Conclusion: MRD detection using IgNGS in PB may be used as a surrogate for FC assessment of MRD in BM. Patients who were MRD negative by IgNGS 1 month after infusion had improved PFS and OS vs those with detectable MRD; ongoing studies will provide further information on the applicability of IgNGS MRD detection and its association with long-term outcome in tisagenlecleucel-treated pediatric and AYA relapsed/refractory B-ALL patients.
Citation Format: Michael A. Pulsipher, Xia Han, Máire Quigley, Gabor Kari, Susana Rives, Theodore W. Laetsch, Gary D. Myers, Hidefumi Hiramatsu, Gregory A. Yanik, Muna Qayed, Timothy Driscoll, Michael W. Boyer, Heather Stefanski, Jochen Buchner, Andre Baruchel, Peter Bader, Lan Yi, Creton Kalfoglou, Harlan Robins, Erik Yusko, Gullu Gorgun, Eric Bleickardt, Stephane Wong, Stephan A. Grupp. Potential utility of minimal residual disease (MRD) to identify relapse in pediatric and young adult (AYA) B-cell acute lymphoblastic leukemia (B-ALL) patients treated with tisagenlecleucel [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT077.