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In this phase 2 open-label randomized study, 31 patients with intermediate-2 or high-risk myelofibrosis received fedratinib 300, 400 or 500 mg once daily in consecutive 4-week cycles. Mean spleen volume reductions at 12 weeks (primary end point) were 30.3% (300 mg), 33.1% (400 mg) and 43.3% (500 mg). Spleen response rates (patients achieving ⩾35% spleen reduction) at 12/24 weeks were 30%/30% (300 mg), 50%/60% (400 mg) and 64%/55% (500 mg), respectively. By 4 weeks, improvements in myelofibrosis (MF)-associated symptoms were observed. At 48 weeks, 68% of patients remained on fedratinib and 16% had discontinued because of adverse events (AEs). Common grade 3/4 AEs were anemia (58%), fatigue (13%), diarrhea (13%), vomiting (10%) and nausea (6%). Serious AEs included one case of reversible hepatic failure and one case of Wernicke’s encephalopathy (after analysis cutoff). Fedratinib treatment led to reduced STAT3 phosphorylation but no meaningful change in JAK2 V617F allele burden. Significant modulation ( P< 0.05, adjusted for multiple comparisons) of 28 cytokines was observed, many of which correlated with spleen reduction. These data confirm the clinical activity of fedratinib in MF. After the analysis cutoff date, additional reports of Wernicke's encephalopathy in other fedratinib trials led to discontinuation of the sponsored clinical development program.

Myelofibrosis (MF) is a chronic yet progressive myeloid neoplasm in which only a minority of patients undergo curative therapy, hematopoietic stem cell transplantation. Ruxolitinib, a JAK1/2 inhibitor, is the lone therapy approved for MF, offering a clear symptom and spleen benefit at the expense of treatment-related cytopenias. Pacritinib (PAC), a multi-kinase inhibitor with specificity for JAK2, FLT3, and IRAK1 but sparing JAK1, has demonstrated clinical activity in MF with minimal myelosuppression. Due to an FDA-mandated full clinical hold, the randomized phase 3 PERSIST trials were abruptly stopped and PAC was immediately discontinued for all patients. Thirty-three patients benefitting from PAC on clinical trial prior to the hold were allowed to resume therapy on an individual, compassionate-use basis. This study reports the detailed outcomes of 19 of these PAC retreatment patients with a median follow-up of 8 months. Despite a median platelet count of 49 × 109/L at restart of PAC, no significant change in hematologic profile was observed. Grade 3/4 adverse events of epistaxis (n = 1), asymptomatic QT prolongation (n = 1), and bradycardia (n = 1) occurred in three patients within the first 3 months of retreatment. One death due to catheter-associated sepsis occurred. The median time to discontinuation of PAC therapy on compassionate use for all 33 patients was 12.2 (95% CI 8.3—NR) months. PAC retreatment was associated with modest improvement in splenomegaly without progressive myelosuppression and supports the continued development of this agent for the treatment of MF second line to ruxolitinib or in the setting of treatment-limiting thrombocytopenia.

AbstractInternational collaborations over the years have produced a series of prognostic models for primary myelofibrosis (PMF), including the recently unveiled mutation-enhanced international prognostic scoring systems for transplant-age patients (MIPSS70 and MIPSS70-plus). In the current study, we considered the feasibility of a genetically inspired prognostic scoring system (GIPSS) that is exclusively based on genetic markers. Among 641 cytogenetically annotated patients with PMF and informative for previously recognized adverse mutations, multivariable analysis identified “VHR” karyotype, “unfavorable” karyotype, absence of type 1/like CALR mutation and presence of ASXL1, SRSF2, or U2AF1Q157 mutation, as inter-independent predictors of inferior survival; the respective HRs (95% CI) were 3.1 (2.1–4.3), 2.1 (1.6–2.7), 2.1 (1.6–2.9), 1.8 (1.5–2.3), 2.4 (1.9–3.2), and 2.4 (1.7–3.3). Based on HR-weighted risk points, a four-tiered GIPSS model was devised: low (zero points; n = 58), intermediate-1 (1 point; n = 260), intermediate-2 (2 points; n = 192), and high (≥3 points; n = 131); the respective median (5-year) survivals were 26.4 (94%), 8.0 (73%), 4.2 (40%), and 2 (14%) years; the model was internally validated by bootstrapping and its predictive accuracy was shown to be comparable to that of MIPSS70-plus. GIPPS offers a low-complexity prognostic tool for PMF that is solely dependent on genetic risk factors and, thus, forward-looking in its essence.

The authors identified calreticulin mutations in the majority of patients with essential thrombocythemia and myelofibrosis who did not have JAK2 mutations. The mutation alters calreticulin protein, and cells expressing the mutant protein are more responsive to growth factors. Philadelphia chromosome–negative myeloproliferative neoplasms include polycythemia vera, essential thrombocythemia, and primary myelofibrosis. 1 A unique gain-of-function mutation in the Janus kinase 2 gene ( JAK2 ) is found in about three quarters of patients in whom these disease entities have been diagnosed. 2 , 3 The valine-to-phenylalanine (V617F) alteration constitutively activates JAK2, resulting in increased phosphorylation of its substrates and leading to increased cytokine responsiveness of myeloid cells. The JAK2 V617F mutation is present in approximately 95% of patients with polycythemia vera and in 50 to 60% of those with essential thrombocythemia or primary myelofibrosis. 4 In addition, somatic mutations of JAK2 exon 12 . . .

Polycythemia vera (PV) and essential thrombocythemia (ET) are myeloproliferative neoplasms with variable risk of evolution into post-PV and post-ET myelofibrosis, from now on referred to as secondary myelofibrosis (SMF). No specific tools have been defined for risk stratification in SMF. To develop a prognostic model for predicting survival, we studied 685 JAK2, CALR , and MPL annotated patients with SMF. Median survival of the whole cohort was 9.3 years (95% CI: 8-not reached-NR-). Through penalized Cox regressions we identified negative predictors of survival and according to beta risk coefficients we assigned 2 points to hemoglobin level <11 g/dl, to circulating blasts ⩾3%, and to CALR -unmutated genotype, 1 point to platelet count <150 × 10 9 /l and to constitutional symptoms, and 0.15 points to any year of age. Myelofibrosis Secondary to PV and ET-Prognostic Model (MYSEC-PM) allocated SMF patients into four risk categories with different survival ( P <0.0001): low (median survival NR; 133 patients), intermediate-1 (9.3 years, 95% CI: 8.1-NR; 245 patients), intermediate-2 (4.4 years, 95% CI: 3.2–7.9; 126 patients), and high risk (2 years, 95% CI: 1.7–3.9; 75 patients). Finally, we found that the MYSEC-PM represents the most appropriate tool for SMF decision-making to be used in clinical and trial settings.

Calreticulin ( CALR ) mutations were recently described in JAK2 and MPL unmutated primary myelofibrosis (PMF) and essential thrombocythemia. In the current study, we compared the clinical, cytogenetic and molecular features of patients with PMF with or without CALR , JAK2 or MPL mutations. Among 254 study patients, 147 (58%) harbored JAK2 , 63 (25%) CALR and 21 (8.3%) MPL mutations; 22 (8.7%) patients were negative for all three mutations, whereas one patient expressed both JAK2 and CALR mutations. Study patients were also screened for ASXL1 (31%), EZH2 (6%), IDH (4%), SRSF2 (12%), SF3B1 (7%) and U2AF1 (16%) mutations. In univariate analysis, CALR mutations were associated with younger age ( P <0.0001), higher platelet count ( P <0.0001) and lower DIPSS-plus score ( P =0.02). CALR -mutated patients were also less likely to be anemic, require transfusions or display leukocytosis. Spliceosome mutations were infrequent ( P =0.0001) in CALR -mutated patients, but no other molecular or cytogenetic associations were evident. In multivariable analysis, CALR mutations had a favorable impact on survival that was independent of both DIPSS-plus risk and ASXL1 mutation status ( P =0.001; HR 3.4 for triple-negative and 2.2 for JAK2 -mutated). Triple-negative patients also displayed inferior LFS ( P =0.003). The current study identifies ‘CALR – ASXL1 + ’ and ‘triple-negative’ as high-risk molecular signatures in PMF.

The myeloproliferative disorders, comprising polycythemia vera, essential thrombocytosis, and myelofibrosis, are clonal hematopoietic cancers that have an indolent course. The clinical manifestations of these entities overlap, as do their genetic drivers. The myeloproliferative neoplasms — polycythemia vera, essential thrombocytosis, and primary myelofibrosis — are unique hematopoietic stem-cell disorders that share mutations that constitutively activate the physiologic signal-transduction pathways responsible for hematopoiesis (Table 1). Consequently, these disorders engage in phenotypic mimicry among themselves, as well as with myeloid neoplasms and even benign hematopoietic disorders. In contrast to the myeloid neoplasms, the myeloproliferative neoplasms have a natural history, with supportive care alone, that is usually measured in decades rather than years. 1 However, a facade of benign myeloproliferation masks a clone of transformed hematopoietic stem cells capable of expansion and transformation to an aggressive . . .

Patient outcome in primary myelofibrosis (PMF) is significantly influenced by karyotype. We studied 879 PMF patients to determine the individual and combinatorial prognostic relevance of somatic mutations. Analysis was performed in 483 European patients and the seminal observations were validated in 396 Mayo Clinic patients. Samples from the European cohort, collected at time of diagnosis, were analyzed for mutations in ASXL1 , SRSF2 , EZH2 , TET2 , DNMT3A , CBL , IDH1 , IDH2 , MPL and JAK2 . Of these, ASXL1 , SRSF2 and EZH2 mutations inter-independently predicted shortened survival. However, only ASXL1 mutations (HR: 2.02; P <0.001) remained significant in the context of the International Prognostic Scoring System (IPSS). These observations were validated in the Mayo Clinic cohort where mutation and survival analyses were performed from time of referral. ASXL1 , SRSF2 and EZH2 mutations were independently associated with poor survival, but only ASXL1 mutations held their prognostic relevance (HR: 1.4; P =0.04) independent of the Dynamic IPSS (DIPSS)-plus model, which incorporates cytogenetic risk. In the European cohort, leukemia-free survival was negatively affected by IDH1/2 , SRSF2 and ASXL1 mutations and in the Mayo cohort by IDH1 and SRSF2 mutations. Mutational profiling for ASXL1, EZH2, SRSF2 and IDH identifies PMF patients who are at risk for premature death or leukemic transformation.

The authors show that the diverse mutations in CALR that occur in nonmutated JAK2 myeloproliferative diseases all introduce frameshift mutations that alter the C-terminal part of the protein and affect its distribution within cells. The myeloproliferative neoplasms are chronic myeloid cancers that are characterized by the overproduction of mature blood cells, and that may evolve into acute myeloid leukemia. 1 , 2 In addition to chronic myeloid leukemia with the BCR-ABL fusion gene, the three most common myeloproliferative neoplasms are essential thrombocythemia, polycythemia vera, and myelofibrosis. Many patients with a BCR-ABL– negative myeloproliferative neoplasm carry a Janus kinase 2 ( JAK2 ) V617F mutation. 3 – 6 The JAK2 V617F mutation or JAK2 exon 12 mutations are found in most patients with polycythemia vera, 7 , 8 whereas the JAK2 V617F mutation is found in only 50 to 60% of . . .

Allogeneic hematopoietic stem-cell transplantation is the only curative treatment for myelofibrosis. Driver mutations are the pathophysiological hallmark of the disease, but the role of mutation clearance after transplantation is unclear. We used highly sensitive polymerase-chain-reaction technology to analyze the dynamics of driver mutations in peripheral-blood samples from 324 patients with myelofibrosis (73% with mutations, 23% with mutations, and 4% with mutations) who were undergoing transplantation after reduced-intensity conditioning. Mutations were detected before transplantation and at 30, 100, and 180 days after transplantation to measure clearance and its effect on relapse and cure. The two primary end points were relapse and disease-free survival. At day 30 after transplantation, mutation clearance was found in 42% of the patients who had mutations, 73% of those who had mutations, and 54% of those who had mutations; the corresponding percentages at day 100 were 63%, 82%, and 100%. The cumulative incidence of relapse at 1 year was 6% (95% confidence interval [CI], 2 to 10) among patients with mutation clearance at day 30 after transplantation and 21% (95% CI, 15 to 27) among those without mutation clearance at day 30. Disease-free and overall survival at 6 years were 61% and 74%, respectively, among patients with mutation clearance at day 30 after transplantation and 41% and 60%, respectively, among those without mutation clearance at day 30. Mutation clearance at day 30 appeared to outperform traditional donor chimerism as a measure of response; it was independently associated with a reduced risk of relapse or progression (hazard ratio, 0.36; 95% CI, 0.21 to 0.61) and appeared to overcome differences in prognosis based on the type of driver mutation ( vs. or ). In patients with myelofibrosis, clearance of driver mutations at day 30 after transplantation appeared to influence relapse and survival, irrespective of the underlying driver mutation.