Richard Dillon

NPM1-mutated acute myeloid leukemia (AML) represents the largest molecular subgroup of adult AML. NPM1-mutated AML is recognizable by molecular techniques and immunohistochemistry, which, when combined, can solve difficult diagnostic problems (including identification of myeloid sarcoma and NPM1 mutations outside exon 12). According to updated 2022 European LeukemiaNet (ELN) guidelines, determining the mutational status of NPM1 (and FLT3) is a mandatory step for the genetic-based risk stratification of AML. Monitoring of measurable residual disease (MRD) by qRT-PCR, combined with ELN risk stratification, can guide therapeutic decisions at the post-remission stage. Here, we review the criteria for appropriate diagnosis and molecular monitoring of NPM1-mutated AML. Significance: NPM1-mutated AML represents a distinct entity in the 2022 International Consensus Classification and 5th edition of World Health Organization classifications of myeloid neoplasms. The correct diagnosis of NPM1-mutated AML and its distinction from other AML entities is extremely important because it has clinical implications for the management of AML patients, such as genetic-based risk stratification according to 2022 ELN. Monitoring of MRD by qRT-PCR, combined with ELN risk stratification, can guide therapeutic decisions at the post-remission stage, e.g., whether or not to perform allogeneic hematopoietic stem cell transplantation.

Summary In high‐risk myeloid malignancy, relapse is reduced using cord blood transplant (CBT) but remains the principal cause of treatment failure. We previously described T‐cell expansion in CBT recipients receiving granulocyte transfusions. We now report the safety and tolerability of such transfusions, T‐cell expansion data, immunophenotype, cytokine profiles and clinical response in children with post‐transplant relapsed acute leukaemia who received T‐replete, HLA‐mismatched CBT and pooled granulocytes within a phase I/II trial (ClinicalTrials.Gov NCT05425043). All patients received the transfusion schedule without significant clinical toxicity. Nine of ten patients treated had detectable measurable residual disease (MRD) pre‐transplant. Nine patients achieved haematological remission, and eight became MRD negative. There were five deaths: transplant complications ( n = 2), disease ( n = 3), including two late relapses. Five patients are alive and in remission with 12.7 months median follow up. Significant T‐cell expansion occurred in nine patients with a greater median lymphocyte count than a historical cohort between days 7–13 (median 1.73 × 10 9 /L vs. 0.1 × 10 9 /L; p < 0.0001). Expanded T‐cells were predominantly CD8 + and effector memory or TEMRA phenotype. They exhibited markers of activation and cytotoxicity with interferon‐gamma production. All patients developed grade 1–3 cytokine release syndrome (CRS) with elevated serum IL‐6 and interferon‐gamma.