PROJECT SUMMARY/ABSTRACT My long-term career goal is to improve outcomes for pediatric patients with acute myeloid leukemia (AML), in part through development of improved modalities to detect residual disease and thus allow early identification and intervention for those patients at highest risk of relapse. My clinical experience as a pediatric oncologist specializing in treatment of myeloid malignancies informs my translational research focus in this area. This mentored career development award will facilitate my development into an independent translational physician- scientist by providing salary support and protected time to enhance my technical skills, knowledge base, and personal development in digital PCR (dPCR) assay development and validation, duplex NGS technology, NGS data analysis and bioinformatics, clinical trial design and development, networking, and collaboration. My mentoring team comprised of Dr. Craig Jordan (primary mentor), Dr. Dan Pollyea, Dr. Mike Verneris, and Dr. Chris Hourigan are all leaders in their respective fields and have a proven track record of fostering trainees and junior faculty to successful academic careers. The resource-rich environment on the Anschutz Medical Campus of the University of Colorado and the access to patient samples afforded me by the COG Myeloid Committee further contribute to a high probability of success for the proposed patient-oriented research. AML accounts for a disproportionate percentage of leukemia-associated morbidity and mortality in children, with relapse the leading cause of death in these patients. Measurable residual disease (MRD) has been shown in AML and other hematologic malignancies to be the single most valuable post-treatment predictor of relapse, but the existing clinical assays for MRD have significant limitations such that a high proportion of children who ultimately succumb to relapsed AML are actually MRD negative post-treatment. We hypothesize that application of molecular MRD assays to pediatric AML disease monitoring will be a sensitive predictor of disease burden and relapse. During the next 5 years I propose (1) to retrospectively evaluate the correlation between relapse and MRD positivity by mutation-based and chimerism-based dPCR assays in pediatric AML patients generally or post-transplant, respectively; (2) to retrospectively evaluate the correlation between relapse and MRD positivity by custom duplex NGS panels in pediatric AML patients; and (3) to prospectively validate the relapse predictive value of duplex NGS as a novel MRD modality in pediatric AML. Successful completion of this project will pave the way toward development of molecular tools such as dPCR and duplex NGS as improved MRD modalities that will enhance clinicians' ability to identify patients at highest risk of relapse and intervene to prevent its occurrence. This will lead to improved survival in pediatric patients suffering from myeloid leukemia.