BACKGROUND Ruxolitinib, a selective JAK1 and JAK2 inhibitor, has clinically significant activity in myelofibrosis. METHODS In a double-blind trial, patients with intermediate-2 or high-risk myelofibrosis were randomized to twice-daily oral ruxolitinib (n=155) or placebo (n=154). The primary endpoint was the proportion of patients with ≥35% spleen volume reduction at 24 weeks assessed by magnetic resonance imaging. Secondary endpoints included durability of response, changes in symptom burden (assessed by Total Symptom Score [TSS]), and overall survival. RESULTS In the ruxolitinib group, 41.9% achieved the primary endpoint versus 0.7% in the placebo group (P<0.001). Spleen response was maintained while taking ruxolitinib: 67% of responding patients maintained response for ≥48 weeks. A ≥50% improvement in TSS at 24 weeks was achieved by 45.9% of ruxolitinib-treated versus 5.3% of placebo-treated patients (P<0.001). Thirteen deaths occurred in the ruxolitinib and 24 in the placebo group (hazard ratio, 0.50; 95% CI, 0.25–0.98; P=0.04). Discontinuations for adverse events were similar between groups (11% each). Among ruxolitinib-treated patients, anemia and thrombocytopenia were the most common adverse events, but rarely led to discontinuation (1 patient for each event). Two patients underwent transformation to acute myeloid leukemia (AML), both in the ruxolitinib group. CONCLUSIONS Ruxolitinib provided significant clinical benefits in patients with myelofibrosis by reducing spleen size, improving debilitating myelofibrosis-related symptoms, and improving overall survival. Improvement came at a cost of more frequent anemia and thrombocytopenia in the early part of the treatment period. The imbalance in AML transformation requires attention in further studies. (Funded by Incyte Corporation; ClinicalTrials.gov, NCT00952289)

Summary In acute myeloid leukemia (AML), the cell of origin, nature and biological consequences of initiating lesions and order of subsequent mutations remain poorly understood, as AML is typically diagnosed without observation of a pre-leukemic phase. Here, highly purified hematopoietic stem cells (HSC), progenitor and mature cell fractions from the blood of AML patients were found to contain recurrent DNMT3a mutations (DNMT3amut) at high allele frequency, but without coincident NPM1 mutations (NPM1c) present in AML blasts. DNMT3amut-bearing HSC exhibited multilineage repopulation advantage over non-mutated HSC in xenografts, establishing their identity as pre-leukemic-HSC (preL-HSC). preL-HSC were found in remission samples indicating that they survive chemotherapy. Thus DNMT3amut arises early in AML evolution, likely in HSC, leading to a clonally expanded pool of preL-HSC from which AML evolves. Our findings provide a paradigm for the detection and treatment of pre-leukemic clones before the acquisition of additional genetic lesions engenders greater therapeutic resistance.

Refractoriness to induction chemotherapy and relapse after achievement of remission are the main obstacles to cure in acute myeloid leukaemia (AML). After standard induction chemotherapy, patients are assigned to different post-remission strategies on the basis of cytogenetic and molecular abnormalities that broadly define adverse, intermediate and favourable risk categories. However, some patients do not respond to induction therapy and another subset will eventually relapse despite the lack of adverse risk factors. There is an urgent need for better biomarkers to identify these high-risk patients before starting induction chemotherapy, to enable testing of alternative induction strategies in clinical trials. The high rate of relapse in AML has been attributed to the persistence of leukaemia stem cells (LSCs), which possess a number of stem cell properties, including quiescence, that are linked to therapy resistance. Here, to develop predictive and/or prognostic biomarkers related to stemness, we generated a list of genes that are differentially expressed between 138 LSC and 89 LSC cell fractions from 78 AML patients validated by xenotransplantation. To extract the core transcriptional components of stemness relevant to clinical outcomes, we performed sparse regression analysis of LSC gene expression against survival in a large training cohort, generating a 17-gene LSC score (LSC17). The LSC17 score was highly prognostic in five independent cohorts comprising patients of diverse AML subtypes (n = 908) and contributed greatly to accurate prediction of initial therapy resistance. Patients with high LSC17 scores had poor outcomes with current treatments including allogeneic stem cell transplantation. The LSC17 score provides clinicians with a rapid and powerful tool to identify AML patients who do not benefit from standard therapy and who should be enrolled in trials evaluating novel upfront or post-remission strategies.