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Background Moxetumomab pasudotox is a recombinant CD22-targeting immunotoxin. Here, we present the long-term follow-up analysis of the pivotal, multicenter, open-label trial (NCT01829711) of moxetumomab pasudotox in patients with relapsed/refractory (R/R) hairy cell leukemia (HCL). Methods Eligible patients had received ≥ 2 prior systemic therapies, including ≥ 2 purine nucleoside analogs (PNAs), or ≥ 1 PNA followed by rituximab or a BRAF inhibitor. Patients received 40 µg/kg moxetumomab pasudotox intravenously on Days 1, 3, and 5 of each 28-day cycle for up to six cycles. Disease response and minimal residual disease (MRD) status were determined by blinded independent central review. The primary endpoint was durable complete response (CR), defined as achieving CR with hematologic remission (HR, blood counts for CR) lasting > 180 days. Results Eighty adult patients were treated with moxetumomab pasudotox and 63% completed six cycles. Patients had received a median of three lines of prior systemic therapy; 49% were PNA-refractory, and 38% were unfit for PNA retreatment. At a median follow-up of 24.6 months, the durable CR rate (CR with HR > 180 days) was 36% (29 patients; 95% confidence interval: 26–48%); CR with HR ≥ 360 days was 33%, and overall CR was 41%. Twenty-seven complete responders (82%) were MRD-negative (34% of all patients). CR lasting ≥ 60 months was 61%, and the median progression-free survival without the loss of HR was 71.7 months. Hemolytic uremic and capillary leak syndromes were each reported in ≤ 10% of patients, and ≤ 5% had grade 3–4 events; these events were generally reversible. No treatment-related deaths were reported. Conclusions Moxetumomab pasudotox resulted in a high rate of durable responses and MRD negativity in heavily pre-treated patients with HCL, with a manageable safety profile. Thus, it represents a new and viable treatment option for patients with R/R HCL, who currently lack adequate therapy. Trial registration ClinicalTrials.gov identifier: NCT01829711; first submitted: April 9, 2013. https://clinicaltrials.gov/ct2/show/NCT01829711

NPM1-mutated AML represents a WHO leukemia entity with unique pathological and clinical features. Little is known about the characteristics of "therapy-related" NPM1-mutated AML. We compared the genetics, transcriptional profile and clinical outcome of therapy-related NPM1-mutated AML (t-NPM1 AML), de-novo NPM1-mutated AML (dn-NPM1 AML) and therapy-related AML with wild-type NPM1 (t-AML). A normal karyotype was more frequent in t-NPM1 AML (n=78/96 cases, 88%) and dn-NPM1 (n=1986/2394,88%) than in t-AML (n=103/390,28%; p <0.001). DNMT3A and TET2 were mutated in 43% and 40% of t-NPM1 AML (n=107), similar to dn-NPM1 (n=88, 48% and 30%; p-values >0.1), but more frequently than t-AML (n=162; 14% and 10%; p-values <0.001). TP53 and PPM1D, typically mutated in t-AML, were consistently wild-type in t-NPM1 AML (97% and 96%). t-NPM1 and dn-NPM1 AML were transcriptionally similar, displaying upregulation of HOX genes and down-regulation of CD133 and CD34. With a median follow-up of 62 months, 3-year overall survival (OS) for t-NPM1 AML (n=96), dn-NPM1 AML (n=2394) and t-AML (n=390) was 54%, 60% and 31%. In multivariable analysis OS was similar for the two NPM1-mutated groups (HR 0.9, 95%CI 0.65-1.25, p=0.45) but better in t-NPM1 AML than t-AML (HR 1.86, 95%CI 1.30-2.68, p<0.001). Relapse-free survival did not differ between t-NPM1 and dn-NPM1 AML (HR 1.02, 95%CI 0.72-1.467, p=0.90) but was significantly higher in t-NPM1 AML than t-AML (HR 1.77, 95%CI 1.19-2.64, p=0.0045).t-NPM1 and dn-NPM1 AML have similar clinical, genomic and transcriptomic features, suggesting that they should be classified as a single disease entity