Impact of prior JAK-inhibitor therapy with ruxolitinib on outcome after allogeneic hematopoietic stem cell transplantation for myelofibrosis: a study of the CMWP of EBMT

Impact of post-transplant cyclophosphamide and splenomegaly on primary graft failure and multi-lineage cytopenia after allogeneic hematopoietic cell transplantation

Primary graft failure (PGF) and multi-lineage cytopenia (MLC) increase the risk of nonrelapse mortality in allogeneic hematopoietic cell transplants (HCT). We evaluated the impact of post-transplant cyclophosphamide (PTCy) and splenomegaly on PGF and MLC for hematological malignancies. This study included patients with PTCy (N=84) and conventional graft-vs.-host disease prophylaxis (N=199). The occurrence of splenomegaly varied widely, ranging from 17.1 % (acute myeloid leukemia) to 66.7 % (myeloproliferative neoplasms). Ten patients (N=8 in the PTCy and N=2 in the non- PTCy) developed PGF, and 44 patients developed MLC (both N=22). PTCy and severe splenomegaly (≥20 cm) were risk factors for PGF (odds ratio (OR): 10.40, p<0.01 and 6.74, p=0.01 respectively). Moreover, severe splenomegaly was a risk factor for PGF in PTCy patients (OR: 10.20, p=0.01). PTCy (hazard ratio (HR) 2.09, p=0.02), moderate (≥15, <20 cm, HR 4.36, p<0.01), and severe splenomegaly (HR 3.04, p=0.01) were independent risk factors for MLC. However, in subgroup analysis in PTCy patients, only mild splenomegaly (≥12, <15 cm, HR 4.62, p=0.01) was a risk factor for MLC. We recommend all patients be screened for splenomegaly before HCT, and PTCy is cautioned in those with splenomegaly.

Graft Failure Incidence, Risk Factors, and Outcomes in Patients Undergoing Non-Myeloablative Allogeneic Hematopoietic Cell Transplantation Using Post-Transplant Cyclophosphamide

Graft failure (GF) is a major complication of allogeneic hematopoietic cell transplantation (alloHCT) that results in significant morbidity and mortality. Post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis has emerged as an effective regimen across the spectrum of donor-match settings, but few studies have investigated the characteristics of GF in the setting of PTCy-based GVHD prophylaxis. The objective was to detail the incidence, clinical features, risk factors, and outcomes for patients with primary graft failure (PGF) and secondary graft failure (SGF). In this retrospective study at a single institution, 958 consecutive patients undergoing first nonmyeloablative (NMA) alloHCT with PTCy-based GVHD prophylaxis were analyzed. PGF was defined as a failure to achieve an ANC ≥ 500 cells/m3 by day 30 of transplant in the absence of residual disease. SGF was defined as complete loss of donor chimerism after initial engraftment. The incidences of PGF and SGF were 3.8% (n = 37) and 1.8% (n = 17), respectively. Neither PGF nor SGF were associated with HLA disparity. In a multivariate analysis, risk factors for PGF in this cohort included age ≥ 65 (OR 2.4, 95% CI 1.2 to 4.8, P = .0120), an underlying diagnosis of MDS, MPN, or MDS/MPN overlap (OR 2.8, 95% CI 1.4 to 5.7, P = .0050), post-transplant viremia with HHV-6 (OR 2.9, 95% CI 1.5 to 5.7, P = .0030), and low CD34+ dose (OR 0.7, 95% CI 0.5 to 0.9, P = .0080). Patients with PGF had poor overall survival, driven primarily by a high rate of nonrelapse mortality (59% at 36 months). SGF was associated with use of a bone marrow graft source and a diagnosis of Hodgkin lymphoma. Patients with SGF had excellent clinical outcomes with only one of seventeen patients experiencing relapse and relapse-related mortality. The incidence of PGF and SGF in patients receiving NMA conditioning and PTCy is low and is not impacted by HLA disparities between donors and recipients. PGF is more common in recipients with age ≥ 65, a diagnosis of MDS, MPN, or MDS/MPN-overlap, post-transplant HHV-6 viremia, and low CD34+ cell dose. Low total nucleated cell dose is also a risk factor for PGF in patients receiving a bone marrow graft source. Patients who experience PGF have poor outcomes due to high rates of nonrelapse mortality, whereas patients who experience SGF have excellent long-term outcomes.

2024 update on allogeneic hematopoietic stem cell transplant for myelofibrosis: A review of current data and applications on risk stratification and management

BACKGROUND

Allogeneic hemopoietic stem cell transplantation (HSCT) currently remains the only curative treatment for patients with myelofibrosis (MF). Transplant related mortality (TRM) and relapse, remain two significant complications which need to be addressed.

AIMS

The aim of this manuscript is to review current available reports on changes which have recently occurred, to improve the outcome of MF patients undergoing an allogeneic HSCT.

METHODS

Published papers were used to analyze different aspects of allogeneic HSCT.

RESULTS

Changes and updates are provided on selection of patients, prognostic systems, managing splenomegaly, conditioning regimens, predicting transplant outcome, stem cell sources, stem cell donors, graft versus host disease (GvHD) prophylaxis, patients with blast phase, hematopoietic reconstitution, disease markers, donor chimerism, and treatment of relapse.

CONCLUSIONS

The review outlines new transplant platforms which are now available for patients with myelofibrosis, together with persisting problems, among which, older age combined with marrow fibrosis and an inflammatory disease. Relapse also requires aggressive monitoring of drivers mutations, and early cellular therapy.

Splenic irradiation for myelofibrosis prior to hematopoietic cell transplantation: A global collaborative analysis

Splenomegaly is the clinical hallmark of myelofibrosis. Splenomegaly at the time of allogeneic hematopoietic cell transplantation (HCT) is associated with graft failure and poor graft function. Strategies to reduce spleen size before HCT especially after failure to Janus kinase (JAK) inhibition represent unmet clinical needs in the field. Here, we leveraged a global collaboration to investigate the safety and efficacy of splenic irradiation as part of the HCT platform for patients with myelofibrosis. We included 59 patients, receiving irradiation within a median of 2 weeks (range, 0.9-12 weeks) before HCT. Overall, the median spleen size prior to irradiation was 23 cm (range, 14-35). Splenic irradiation resulted in a significant and rapid spleen size reduction in 97% of patients (57/59), with a median decrease of 5.0 cm (95% confidence interval, 4.1-6.3 cm). The most frequent adverse event was thrombocytopenia, with no correlation between irradiation dose and hematological toxicities. The 3-year overall survival was 62% (95% CI, 48%-76%) and 1-year non-relapse mortality was 26% (95% CI, 14%-38%). Independent predictors for survival were severe thrombocytopenia and anemia before irradiation, transplant-specific risk score, higher-intensity conditioning, and present portal vein thrombosis. When using a propensity score matching adjusted for common confounders, splenic irradiation was associated with significantly reduced relapse (p = .01), showing a 3-year incidence of 12% for splenic irradiation versus 29% for patients with immediate HCT and 38% for patients receiving splenectomy. In conclusion, splenic irradiation immediately before HCT is a reasonable approach in patients experiencing JAK inhibition failure and is associated with a low incidence of relapse.

Graft-versus-host disease and impact on relapse in myelofibrosis undergoing hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) remains the only curative treatment for myelofibrosis (MF). Relapse occurs in 10-30% and remains a major factor for dismal outcomes. Previous work suggested that graft-versus-host disease (GVHD) might be associated with risk of relapse. This study included 341 patients undergoing their first (n = 308) or second (n = 33) alloHSCT. Anti-T-lymphocyte or antithymocyte globulin was used for GVHD prophylaxis in almost all patients. Median time to neutrophile and platelet engraftment was 13 days and 19 days, respectively. The cumulative incidence of acute GVHD grade II-IV was 41% (median, 31 days; range, 7-112). Grade III-IV acute GVHD was observed in 22%. The cumulative incidence of chronic GVHD was 61%. Liver was affected in 23% of acute GVHD cases and 46% of chronic GVHD cases. Severe acute GVHD was associated with high non-relapse mortality. The development of acute GVHD grade II and moderate GVHD was an independent factor for reduced risk for relapse after transplantation without increased risk for non-relapse mortality, while especially acute GVHD grade IV was associated with high non-relapse mortality. Last, we identified that ongoing response to ruxolitinib, accelerated-phase MF at time of transplantation and splenectomy prior to transplantation were independent predictors for relapse.

Transplantation for myelofibrosis patients in the ruxolitinib era: a registry study from the Société Francophone de Greffe de Moelle et de Thérapie Cellulaire

In this SFGM-TC registry study, we report the results after stem cell transplantation (HSCT) in 305 myelofibrosis patients, in order to determine potential risk factors associated with outcomes, especially regarding previous treatment with ruxolitinib. A total of 102 patients were transplanted from an HLA-matched-sibling donor (MSD), and 143 patients received ruxolitinib. In contrast with previous studies, our results showed significantly worse outcomes for ruxolitinib patients regarding overall survival (OS) and non-relapse mortality (NRM), especially in the context of unrelated donors (URD). When exploring reasons for potential confounders regarding the ruxolitinib effect, an interaction between the type of donor and the use of ATG was found, therefore subsequent analyses were performed separately for each type of donor. Multivariable analyses did not confirm a significant negative impact of ruxolitinib in transplantation outcomes. In the setting of URD, only age and Fludarabine-Melphalan (FM) conditioning were associated with increased NRM. For MSD, only Karnoksfy <70% was associated with reduced OS. However, a propensity score analysis showed that ruxolitinib had a negative impact on OS but only in non-responding patients, consistent with previous data. To conclude, with all the precautions due to confounders and bias, ruxolitinib itself does not appear to increase mortality after HSCT.

The application of JAK inhibitors in the peri-transplantation period of hematopoietic stem cell transplantation for myelofibrosis

Myelofibrosis (MF) is a myeloproliferative neoplasm (MPN) with a poor prognosis, and allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only treatment with curative potential. Ruxolitinib, a JAK1/2 inhibitor, has shown promising results in improving patients' symptoms, overall survival, and quality of life, and can be used as a bridging therapy to HSCT that increases the proportion of transplantable patients. However, the effect of this and similar drugs on HSCT outcomes is unknown, and the reports on their efficacy and safety in the peri-transplantation period vary widely in the published literature. This paper reviews clinical data related to the use of JAK inhibitors in the peri-implantation phase of hematopoietic stem cell transplantation for primary myelofibrosis and discusses their efficacy and safety.

Indication and management of allogeneic haematopoietic stem-cell transplantation in myelofibrosis: updated recommendations by the EBMT/ELN International Working Group

New options for medical therapy and risk scoring systems containing molecular data are leading to increased complexity in the management of patients with myelofibrosis. To inform patients' optimal care, we updated the 2015 guidelines on indications for and management of allogeneic haematopoietic stem-cell transplantation (HSCT) with the support of the European Society for Blood and Marrow Transplantation (EBMT) and European LeukemiaNet (ELN). New recommendations were produced using a consensus-building methodology after a comprehensive review of articles released from January, 2015 to December, 2022. Seven domains and 18 key questions were selected through a series of questionnaires using a Delphi process. Key recommendations in this update include: patients with primary myelofibrosis and an intermediate-2 or high-risk Dynamic International Prognostic Scoring System score, or a high-risk Mutation-Enhanced International Prognostic Score Systems (MIPSS70 or MIPSS70-plus) score, or a low-risk or intermediate-risk Myelofibrosis Transplant Scoring System score should be considered candidates for allogeneic HSCT. All patients who are candidates for allogeneic HSCT with splenomegaly greater than 5 cm below the left costal margin or splenomegaly-related symptoms should receive a spleen-directed treatment, ideally with a JAK-inhibitor; HLA-matched sibling donors remain the preferred donor source to date. Reduced intensity conditioning and myeloablative conditioning are both valid options for patients with myelofibrosis. Regular post-transplantation driver mutation monitoring is recommended to detect and treat early relapse with donor lymphocyte infusion. In a disease where evidence-based guidance is scarce, these recommendations might help clinicians and patients in shared decision making.

Are transplant indications changing for myelofibrosis?

Myelofibrosis is a devastating myeloid malignancy characterized by dysregulation of the JAK-STAT pathway, resulting in splenomegaly, constitutional symptoms, anemia, thrombocytopenia, leukocytosis, and an increased likelihood of progression to acute leukemia. The only curative option is allogeneic stem cell transplantation. The numbers of transplants have been increasing every year, and although there have been improvements in survival, there remain many unanswered questions. In this review, we will evaluate patient selection and appropriate timing for transplantation. We will cover the current prognostic scoring systems, which can aid in the decision of when to move forward with transplant. We will also review the different donor options, as well as the conditioning regimens. The peritransplant management of splenomegaly will be reviewed. We will discuss management of posttransplant complications such as loss of donor chimerism or disease relapse. Finally, we will review what is known about the outlook of patients who have undergone allogeneic stem cell transplant with regards to quality of life and long-term survival.

How I treat transplant-eligible patients with myelofibrosis

Despite the approval of Janus kinase inhibitors and novel agents for patients with myelofibrosis (MF), disease-modifying responses remain limited, and hematopoietic stem cell transplantation (HSCT) remains the only potentially curative treatment option. The number of HSCTs for MF continues to increase worldwide, but its inherent therapy-related morbidity and mortality limit its use for many patients. Furthermore, patients with MF often present at an older age, with cytopenia, splenomegaly, and severe bone marrow fibrosis, posing challenges in managing them throughout the HSCT procedure. Although implementation of molecular analyses enabled improved understanding of disease mechanisms and subsequently sparked development of novel drugs with promising activity, prospective trials in the HSCT setting are often lacking, making an evidence-based decision process particularly difficult. To illustrate how we approach patients with MF with respect to HSCT, we present 3 different clinical scenarios to capture relevant aspects that influence our decision making regarding indication for, or against, HSCT. We describe how we perform HSCT according to different risk categories and, furthermore, discuss our up-to-date approach to reduce transplant-related complications. Last, we show how to harness graft-versus-MF effects, particularly in the posttransplant period to achieve the best possible outcomes for patients.

Momelotinib (JAK1/JAK2/ACVR1 inhibitor): mechanism of action, clinical trial reports, and therapeutic prospects beyond myelofibrosis

Janus kinase (JAK) 2 inhibitors are now part of the therapeutic armamentarium for primary and secondary myelofibrosis (MF). Patients with MF endure shortened survival and poor quality of life. Allogeneic stem cell transplantation (ASCT) is currently the only treatment modality in MF with the potential to cure the disease or prolong survival. By contrast, current drug therapy in MF targets quality of life and does not modify the natural history of the disease. The discovery of JAK2 and other JAK-STAT activating mutations (i.e., CALR and MPL) in myeloproliferative neoplasms, including MF, has facilitated the development of several JAK inhibitors that are not necessarily specific to the oncogenic mutations themselves but have proven effective in countering JAK-STAT signaling, resulting in suppression of inflammatory cytokines and myeloproliferation. This non-specific activity resulted in clinically favorable effects on constitutional symptoms and splenomegaly and, consequently, approval by the Food and Drug Administration (FDA) of three small molecule JAK inhibitors: ruxolitinib, fedratinib, and pacritinib. A fourth JAK inhibitor, momelotinib, is poised for FDA approval soon and has been shown to provide additional benefit in alleviating transfusion-dependent anemia in MF. The salutary effect of momelotinib on anemia has been attributed to inhibition of activin A receptor, type 1 (ACVR1) and recent information suggests a similar effect from pacritinib. ACRV1 mediates SMAD2/3 signaling which contributes to upregulation of hepcidin production and iron-restricted erythropoiesis. Targeting ACRV1 raises therapeutic prospects in other myeloid neoplasms associated with ineffective erythropoiesis, such as myelodysplastic syndromes with ring sideroblasts or SF3B1 mutation, especially those with co-expression of a JAK2 mutation and thrombocytosis.

A Journey Through JAK Inhibitors for the Treatment of Myeloproliferative Diseases

PURPOSE OF REVIEW

Chronic myeloproliferative neoplasms (MPN) represent a group of diseases characterised by constitutive activation of the JAK/STAT pathway in a clonal myeloid precursor. The therapeutic approach aims to treat the symptom burden (headache, itching, debilitation), splenomegaly, slow down the fibrotic proliferation in the bone marrow and reduce the risk of thrombosis/bleeding whilst avoiding leukaemic transformation.

RECENT FINDINGS

In recent years, the advent of JAK inhibitors (JAKi) has significantly broadened treatment options for these patients. In myelofibrosis, symptom control and splenomegaly reduction can improve quality of life with improved overall survival, not impacting progression into acute leukaemia. Several JAKi are available and used worldwide, and combination approaches are now being explored. In this chapter, we review the approved JAKi, highlighting its strengths, exploring potential guidelines in choosing which one to use and reasoning towards future perspectives, where the combinations of therapies seem to promise the best results.

The pharmacotherapeutic management of patients with myelofibrosis: looking beyond JAK inhibitors

INTRODUCTION

The approach to myelofibrosis (MF) has been revolutionized in recent years, overcoming the traditional therapies, often not very effective. Janus kinase inhibitors (JAKi - from ruxolitinib up to momelotinib) were the first class of drugs with considerable results.

AREAS COVERED

Ongoing, new molecules are being tested that promise to give hope even to those patients not eligible for bone marrow transplants who become intolerant or are refractory to JAKi, for which therapeutic hopes are currently limited. Telomerase, murine double minute 2 (MDM2), phosphatidylinositol 3-kinase δ (PI3Kδ), BCL-2/xL, and bromodomain and extra-terminal motif (BET) inhibitors are the drugs with promising results in clinical trials and close to closure with consequent placing on the market, finally allowing JAK to look beyond. The novelty of the MF field was searched in the PubMed database, and the recently completed/ongoing trials are extrapolated from the ClinicalTrial website.

EXPERT OPINION

From this point of view, the use of new molecules widely described in this review, probably in association with JAKi, will represent the future treatment of choice in MF, leaving, in any case, the potential new approaches actually in an early stage of development, such as the use of immunotherapy in targeting CALR, which is coming soon.

Recent progress of JAK inhibitors for hematological disorders

JAK inhibitors are important therapeutic options for hematological disorders, especially myeloproliferative neoplasms. Ruxolitinib, the first JAK inhibitor approved for clinical use, improves splenomegaly and ameliorates constitutional symptoms in both myelofibrosis and polycythemia vera patients. Ruxolitinib is also useful for controlling hematocrit levels in polycythemia vera patients who were inadequately controlled by conventional therapies. Furthermore, pretransplantation use of ruxolitinib may improve the outcome of allo-hematopoietic stem cell transplantation in myelofibrosis. In contrast to these clinical merits, evidence of the disease-modifying action of ruxolitinib, i.e., reduction of malignant clones or improvement of bone marrow pathological findings, is limited, and many myelofibrosis patients discontinued ruxolitinib due to adverse events or disease progression. To overcome these limitations of ruxolitinib, several new types of JAK inhibitors have been developed. Among them, fedratinib was proven to provide clinical merits even in patients who were resistant or intolerant to ruxolitinib. Pacritinib and momelotinib have shown merits for myelofibrosis patients with thrombocytopenia or anemia, respectively. In addition to treatment for myeloproliferative neoplasms, recent studies have demonstrated that JAK inhibitors are novel and attractive therapeutic options for corticosteroid-refractory acute as well as chronic graft versus host disease.

Advances in management of primary myelofibrosis and polycythaemia vera: Implications in clinical practice

Primary myelofibrosis (PMF) and polycythaemia vera (PV) are rare BCR-ABL1-negative myeloproliferative neoplasms, associated with an increased risk of thrombosis, haemorrhagic complications and progression to fibrosis or leukaemia or fibrosis for PV. Both diseases are characterised by biological and clinical heterogeneity, leading to great variability in their management in routine clinical practice. In this review, we present an updated overview of the diagnosis, prognosis and treatment of PMF and PV, and we discuss how our multidisciplinary expert group based across France translates this evidence-based knowledge into routine clinical practice.

Spleen volume and length determined by computed tomography impact outcome after allogeneic stem cell transplantation for myelofibrosis

Splenomegaly is a hallmark of myelofibrosis (MF), and reports on the impact of spleen size on the outcome of allo-HSCT have been conflicting, possibly due to differences in methods of assessment. We retrospectively analysed the impact of spleen volume and length measured by computed tomography on allo-HSCT outcome in 93 patients, 74% of whom had prior ruxolitinib treatment. Median spleen volume and length were 1.58 dm3 and 20 cm, respectively. We found a strong correlation between spleen volume and length (Pearson's r = 0.95, p < 0.001), Spearman (rho = 0.96, p < 0.001). After a median follow-up of 41.7 months, 5-year overall and disease-free survival were 66% and 59%, respectively. Spleen size did not impact overall survival or non-relapse mortality. Larger spleen volume and length as continuous variables were associated with slower platelet and leucocyte engraftment and a higher risk of disease relapse in univariate and multivariate analyses. Spleen length measured precisely by imaging is a good surrogate for spleen volume. In the era of JAK inhibitors, larger spleen size reflects advanced disease in MF and is associated with an increased risk of relapse but has no impact on non-relapse mortality and overall survival after allo-HSCT.

Splenic irradiation prior to allogeneic transplant conditioning in myelofibrosis: A pilot experience

INTRODUCTION

In the era of JAK inhibitors, allogeneic stem cell transplantation (HSCT) remains the only curative treatment for patients with Myelofibrosis (MF). Splenic irradiation (SI) may be used to reduce spleen size and related symptoms.

METHODS

We conducted a retrospective analysis on 14 patients with MF who underwent HSCT with SI from any donor source at our center between June 2016 and March 2021. All patients received a conditioning backbone based on treosulfan and fludarabine, with post-transplant cyclophosphamide (PTCy) and sirolimus as graft-versus-host disease (GvHD) prophylaxis. Patients received SI with 10 Gy involved-field radiotherapy in five 2-Gy fractions over the course of a week prior to the beginning of conditioning.

RESULTS

At transplant all patients were transfusion-dependent and had splenomegaly (median bipolar diameter by ultrasound: 20.75 cm). Overall, 12 patients had received ruxolitinib prior to transplant. Re-evaluation of spleen dimensions was available for 13 patients: median splenic bipolar diameter after at least 3 months from transplant decreased by a median of 25%. With a median post-transplant follow-up of 25 months, 6 patients remain in CR with full-donor chimerism, 3 patients died due to NRM. Overall, 4 patients relapsed. At last follow-up, nine patients are currently alive and achieved transfusion-independence.

CONCLUSIONS

In a small cohort of mostly ruxolitinib pre-treated patients, SI and treosulfan-based conditioning appeared a safe and effective tool to reduce spleen dimensions and ameliorate symptoms. Future prospective studies with adequate sample size are warranted to further investigate the usefulness and safety of this approach in MF.

Association between the choice of the conditioning regimen and outcomes of allogeneic hematopoietic cell transplantation for myelofibrosis

Allogeneic hematopoietic cell transplantation (allo-HCT) remains the only curative treatment for myelofibrosis. However, the optimal conditioning regimen either with reduced-intensity conditioning (RIC) or myeloablative conditioning (MAC) is not well known. Using the Center for International Blood and Marrow Transplant Research database, we identified adults aged ≥18 years with myelofibrosis undergoing allo-HCT between 2008-2019 and analyzed the outcomes separately in the RIC and MAC cohorts based on the conditioning regimens used. Among 872 eligible patients, 493 underwent allo-HCT using RIC (fludarabine/ busulfan n=166, fludarabine/melphalan n=327) and 379 using MAC (fludarabine/busulfan n=247, busulfan/cyclophosphamide n=132). In multivariable analysis with RIC, fludarabine/melphalan was associated with inferior overall survival (hazard ratio [HR]=1.80; 95% confidenec interval [CI]: 1.15-2.81; P=0.009), higher early non-relapse mortality (HR=1.81; 95% CI: 1.12-2.91; P=0.01) and higher acute graft-versus-host disease (GvHD) (grade 2-4 HR=1.45; 95% CI: 1.03-2.03; P=0.03; grade 3-4 HR=2.21; 95%CI: 1.28-3.83; P=0.004) compared to fludarabine/busulfan. In the MAC setting, busulfan/cyclophosphamide was associated with a higher acute GvHD (grade 2-4 HR=2.33; 95% CI: 1.67-3.25; P<0.001; grade 3-4 HR=2.31; 95% CI: 1.52-3.52; P<0.001) and inferior GvHD-free relapse-free survival (GRFS) (HR=1.94; 95% CI: 1.49-2.53; P<0.001) as compared to fludarabine/busulfan. Hence, our study suggests that fludarabine/busulfan is associated with better outcomes in RIC (better overall survival, lower early non-relapse mortality, lower acute GvHD) and MAC (lower acute GvHD and better GRFS) in myelofibrosis.

Myelofibrosis

The clinical phenotype of primary and post-polycythemia vera and postessential thrombocythemia myelofibrosis (MF) is dominated by splenomegaly, symptomatology, a variety of blood cell alterations, and a tendency to develop vascular complications and blast phase. Diagnosis requires assessing complete cell blood counts, bone marrow morphology, deep genetic evaluations, and disease history. Driver molecular events consist of JAK2V617F, CALR, and MPL mutations, whereas about 8% to 10% of MF are "triple-negative." Additional myeloid-gene variants are described in roughly 80% of patients. Currently available clinical-based and integrated clinical/molecular-based scoring systems predict the survival of patients with MF and are applied for conventional treatment decision-making, indication to stem cell transplant (SCT) and allocation in clinical trials. Standard treatment consists of anemia-oriented therapies, hydroxyurea, and JAK inhibitors such as ruxolitinib, fedratinib, and pacritinib. Overall, spleen volume reduction of 35% or greater at week 24 can be achieved by 42% of ruxolitinib-, 47% of fedratinib-, 19% of pacritinib-, and 27% of momelotinib-treated patients. Now, it is time to move towards new paradigms for evaluating efficacy like disease modification, that we intend as a robust and unequivocal effect on disease biology and/or on patient survival. The growing number of clinical trials potentially pave the way for new strategies in patients with MF. Translational studies of some molecules showed an early effect on bone marrow fibrosis and on variant allele frequencies of myeloid genes. SCT is still the only curative option, however, it is associated with relevant challenges. This review focuses on the diagnosis, prognostication, and treatment of MF.

Splenomegaly in patients with primary or secondary myelofibrosis who are candidates for allogeneic hematopoietic cell transplantation: a Position Paper on behalf of the Chronic Malignancies Working Party of the EBMT

Splenomegaly is a hallmark of myelofibrosis, a debilitating haematological malignancy for which the only curative option is allogeneic haematopoietic cell transplantation (HCT). Considerable splenic enlargement might be associated with a higher risk of delayed engraftment and graft failure, increased non-relapse mortality, and worse overall survival after HCT as compared with patients without significantly enlarged splenomegaly. Currently, there are no standardised guidelines to assist transplantation physicians in deciding optimal management of splenomegaly before HCT. Therefore, the aim of this Position Paper is to offer a shared position statement on this issue. An international group of haematologists, transplantation physicians, gastroenterologists, surgeons, radiotherapists, and radiologists with experience in the treatment of myelofibrosis contributed to this Position Paper. The key issues addressed by this group included the assessment, prevalence, and clinical significance of splenomegaly, and the need for a therapeutic intervention before HCT for the control of splenomegaly. Specific scenarios, including splanchnic vein thrombosis and COVID-19, are also discussed. All patients with myelofibrosis must have their spleen size assessed before allogeneic HCT. Myelofibrosis patients with splenomegaly measuring 5 cm and larger, particularly when exceeding 15 cm below the left costal margin, or with splenomegaly-related symptoms, could benefit from treatment with the aim of reducing the spleen size before HCT. In the absence of, or loss of, response, patients with increasing spleen size should be evaluated for second-line options, depending on availability, patient fitness, and centre experience. Splanchnic vein thrombosis is not an absolute contraindication for HCT, but a multidisciplinary approach is warranted. Finally, prevention and treatment of COVID-19 should adhere to standard recommendations for immunocompromised patients.

Haploidentical Hematopoietic Cell Transplantation for Myelofibrosis in the Ruxolitinib Era

Haploidentical stem cell transplantation is a viable strategy in the absence of an HLA-identical donor, but in myelofibrosis (MF), concerns may rise due to the risk of graft failure. Considering that engraftment is a major issue in MF, we sought to highlight its impact on survival outcomes. In addition, we explored the impact of pretransplantation ruxolitinib administration as an independent variable on outcomes. Here we report the results of a retrospective, monocentric experience with T cell-replete haploidentical bone marrow transplantation with post-transplantation cyclophosphamide as graft-versus-host disease (GVHD) prophylaxis in 51 consecutive MF-affected patients. The median duration of follow-up was 47 months. All 51 patients received a double-alkylating conditioning regimen, and 21 patients (41%) received pretransplantation ruxolitinib. Thirty-seven of 49 evaluable patients (76%) achieved full donor chimerism with neutrophil engraftment, 8 of 49 (16%) experienced graft rejection, and 4 of 49 (8%) had primary poor graft function. Splenectomy was more frequent among patients who engrafted (P = .06). Graft rejection was the sole factor negatively impacting overall survival (hazard ratio [HR], 4.19; 95% confidence interval [CI], 1.37 to 12.80; P = .01) and the major determinant for nonrelapse mortality (HR, 10.31; 95% CI, 2.54 to 41.82; P = .001). The 24-month incidence of relapse was 19% and was negatively impacted by splenectomy (HR, 5.84; 95% CI, 1.28 to 26.72; P = .02). The cumulative incidence of grade II-IV acute GVHD was 27% (95% CI, 20% to 33%), and that of grade III-IV acute GVHD was 8% (95% CI, 4% to 12%). The 24-month cumulative incidence of all-grade chronic GVHD was 28% (95% CI, 21% to 35%). Our data show that T cell-replete haploidentical bone marrow transplantation following double-alkylating conditioning in patients with MF is associated with favorable rates of GVHD and an acceptable relapse risk; nevertheless, rejection is not negligible and is associated with significant mortality. Splenectomy, which favors engraftment, is predictive of a higher risk of relapse.

Innovative strategies to improve hematopoietic stem cell transplant outcomes in myelofibrosis

Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by inflammation, marrow fibrosis, and an inherent risk of blastic transformation. Hematopoietic allogeneic stem cell transplant is the only potentially curative therapy for this disease, however, survival gains observed for other transplant indications over the past two decades have not been realized for MF. The role of transplantation may also evolve with the use of novel targeted agents. The chronic inflammatory state associated with MF necessitates pretransplantation assessment of end-organ function. Applying the transplant methodology employed for other myeloid disorders to patients with MF fails to acknowledge differences in the underlying disease pathophysiology. Limited understanding of the causes of poor transplant outcomes in this cohort has prevented refinement of transplant eligibility criteria in MF. There is increasing evidence of heterogeneity in molecular disease grade, beyond the clinical manifestations which have traditionally guided transplant timing. Exploring the physiological consequences of disease chronicity unique to MF, acknowledging the heterogeneity in disease grade, and using advanced prognostic models, molecular diagnostics and other organ function diagnostic tools, we present an innovative review of strategies with the potential to improve transplant outcomes in this disease. Larger, prospective studies which consider the impact of molecular-based disease grade are needed for MF transplantation.

Towards a Personalized Definition of Prognosis in Philadelphia-Negative Myeloproliferative Neoplasms

Purpose of Review

Philadelphia-negative myeloproliferative neoplasms (MPNs) include polycythemia vera (PV), essential thrombocythemia (ET), prefibrotic (pre-), and overt-primary myelofibrosis (primary MF, PMF). PV and ET could evolve into secondary MF (SMF), whose early diagnosis relies on monitoring signs of possible progression. All MPNs have a risk of blast phase (BP), that is associated with a very dismal outcome. Overall survival (OS) is different among MPNs, and disease-specific prognostic scores should be applied for a correct clinical management. In this review, an overview of current prognostic scores in MPNs will be provided.

Recent Findings

The biological complexity of MPNs and its role on the trajectory of disease outcome have led to the design of integrated prognostic models that are nowadays of common use in PMF patients. As for PV and ET, splicing gene mutations could have a detrimental role, but with the limit of the not routinary recommended application of extensive molecular analysis in these diseases. SMF is recognized as a distinct entity compared to PMF, and OS estimates should be calculated by the MYSEC-PM (Myelofibrosis SECondary-prognostic model). Both in PMF and SMF, decisions as selection of patients potentially candidates to allogenic stem cell transplant or that could benefit from an early shift from standard treatment are based not only on conventional prognostic scores, but also on multivariable algorithms.

Summary

The expanding landscape of risk prediction for OS, evolution to BP, and SMF progression from PV/ET informs personalized approach to the management of patients affected by MPNs.

Management of Myelofibrosis during Treatment with Ruxolitinib: A Real-World Perspective in Case of Resistance and/or Intolerance

The development and approval of ruxolitinib, the first JAK1/2 inhibitor indicated to treat myelofibrosis, has improved patient outcomes, with higher spleen and symptoms responses, improved quality of life, and overall survival. Despite this, several unmet needs remain, including the absence of resistance criteria, suboptimal response, the timing of allogeneic transplant, and the management of patients in case of intolerance. Here, we report the results of the second survey led by the “MPN Lab” collaboration, which aimed to report physicians’ perspectives on these topics. As in our first survey, physicians were selected throughout Italy, and we included those with extensive experience in treating myeloproliferative neoplasms and those with less experience representing clinical practice in the real world. The results presented here, summarized using descriptive analyses, highlight the need for a clear definition of response to ruxolitinib as well as recommendations to guide the management of ruxolitinib under specific conditions including anemia, thrombocytopenia, infections, and non-melanoma skin cancers.

JAK2 Alterations in Acute Lymphoblastic Leukemia: Molecular Insights for Superior Precision Medicine Strategies

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer, arising from immature lymphocytes that show uncontrolled proliferation and arrested differentiation. Genomic alterations affecting Janus kinase 2 (JAK2) correlate with some of the poorest outcomes within the Philadelphia-like subtype of ALL. Given the success of kinase inhibitors in the treatment of chronic myeloid leukemia, the discovery of activating JAK2 point mutations and JAK2 fusion genes in ALL, was a breakthrough for potential targeted therapies. However, the molecular mechanisms by which these alterations activate JAK2 and promote downstream signaling is poorly understood. Furthermore, as clinical data regarding the limitations of approved JAK inhibitors in myeloproliferative disorders matures, there is a growing awareness of the need for alternative precision medicine approaches for specific JAK2 lesions. This review focuses on the molecular mechanisms behind ALL-associated JAK2 mutations and JAK2 fusion genes, known and potential causes of JAK-inhibitor resistance, and how JAK2 alterations could be targeted using alternative and novel rationally designed therapies to guide precision medicine approaches for these high-risk subtypes of ALL.

The role of JAK inhibitors in hematopoietic cell transplantation

The Janus Kinase (JAK)/Signal Transducers and Activators of Transcription (STAT) pathway is essential for both the regulation of hematopoiesis and the control of inflammation. Disruption of this pathway can lead to inflammatory and malignant disease processes. JAK inhibitors, designed to control the downstream effects of pro-inflammatory and pro-angiogenic cytokines, have been successfully used in pre-clinical models and clinical studies of patients with autoimmune diseases, hematologic malignancies, and the hematopoietic cell transplantation (HCT) complication graft versus host disease (GVHD). In the last decade, JAK inhibitors Ruxolitinib, Fedratinib, and most recently Pacritinib have been United States Federal Drug Administration (FDA) approved for the treatment of myelofibrosis (MF). Ruxolitinib was also recently approved for the treatment of steroid refractory acute as well as chronic GVHD; JAK inhibitors are currently under evaluation in the pre-HCT setting in MF and for the prevention of GVHD. This review will focus on the role of JAK inhibitors in the treatment of hematologic malignancies, the potential function of pre-HCT JAK inhibitors in patients with MF, and the role of JAK inhibitors in the prevention and treatment of acute and chronic GVHD.

The Use of Allogeneic Hematopoietic Stem Cell Transplantation in Primary Myelofibrosis

Primary myelofibrosis (PMF) is a BCR-ABL1 negative myeloproliferative neoplasm characterized by clonal proliferation of myeloid cells. This leads to reactive bone marrow fibrosis, ultimately resulting in progressive marrow failure, hepatosplenomegaly, and extramedullary hematopoiesis. PMF is considered the most aggressive of the BCR-ABL1 negative myeloproliferative neoplasms with the least favorable prognosis. Constitutional symptoms are common, which can impact an individual’s quality of life and leukemic transformation remains an important cause of death in PMF patients. The development of the Janus kinase 2 (JAK2) inhibitors have provided a good option for management of PMF-related symptoms. Unfortunately, these agents have not been shown to improve overall survival or significantly alter the course of disease. Allogenic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative treatment option in PMF. However, allo-HSCT is associated with significant treatment-related morbidity and mortality and has historically been reserved for younger, high-risk patients. This review examines patient, disease, and transplant-specific factors which may impact transplant-related outcomes in PMF. Through the vast improvements in donor selection, conditioning regimens, and post-transplant care, allo-HSCT may provide a safe and effective curative option for a broader range of PMF patients in the future.

Role of JAK inhibitors in myeloproliferative neoplasms: current point of view and perspectives

Classic Philadelphia-negative myeloproliferative neoplasms (MPN) include polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF), classified as primary (PMF), or secondary to PV or ET. All MPN, regardless of the underlying driver mutation in JAK2/CALR/MPL, are invariably associated with dysregulation of JAK/STAT pathway. The discovery of JAK2V617F point mutation prompted the development of small molecules inhibitors of JAK tyrosine kinases (JAK inhibitors-JAKi). To date, among JAKi, ruxolitinib (RUX) and fedratinib (FEDR) are approved for intermediate and high-risk MF, and RUX is also an option for high-risk PV patients inadequately controlled by or intolerant to hydroxyurea. While not yet registered, pacritinib (PAC) and momelotinib (MMB), proved to be effective particularly in thrombocytopenic and anemic MF patients, respectively. In most cases, JAKi are effective in reducing splenomegaly and alleviating disease-related symptoms. However, almost 50% lose response by three years and dose-dependent toxicities may lead to suboptimal dosing or treatment discontinuation. To date, although not being disease-modifying agents, JAKi represent the therapeutic backbone particularly in MF patient. To optimize therapeutic strategies, many trials with drug combinations of JAKi with novel molecules are ongoing. This review critically discusses the role of JAKi in the modern management of patients with MPN.

Myelofibrosis: Genetic Characteristics and the Emerging Therapeutic Landscape

Primary myelofibrosis (PMF) is one of three myeloproliferative neoplasms (MPN) that are morphologically and molecularly inter-related, the other two being polycythemia vera (PV) and essential thrombocythemia (ET). MPNs are characterized by JAK-STAT-activating JAK2, CALR, or MPL mutations that give rise to stem cell-derived clonal myeloproliferation, which is prone to leukemic and, in case of PV and ET, fibrotic transformation. Abnormal megakaryocyte proliferation is accompanied by bone marrow fibrosis and characterizes PMF, while the clinical phenotype is pathogenetically linked to ineffective hematopoiesis and aberrant cytokine expression. Among MPN-associated driver mutations, type 1-like CALR mutation has been associated with favorable prognosis in PMF, while ASXL1, SRSF2, U2AF1-Q157, EZH2, CBL, and K/NRAS mutations have been shown to be prognostically detrimental. Such information has enabled development of exclusively genetic (GIPSS) and clinically integrated (MIPSSv2) prognostic models that facilitate individualized treatment decisions. Allogeneic stem cell transplantation remains the only treatment modality in MF with the potential to prolong survival, whereas drug therapy, including JAK2 inhibitors, is directed mostly at the inflammatory component of the disease and is therefore palliative in nature. Similarly, disease-modifying activity remains elusive for currently available investigational drugs, while their additional value in symptom management awaits controlled confirmation. There is a need for genetic characterization of clinical observations followed by in vitro and in vivo preclinical studies that will hopefully identify therapies that target the malignant clone in MF to improve patient outcomes.

How We Manage Myelofibrosis Candidates for Allogeneic Stem Cell Transplantation

Moving from indication to transplantation is a critical process in myelofibrosis. Most of guidelines specifically focus on either myelofibrosis disease or transplant procedure, and, currently, no distinct indication for the management of MF candidates to transplant is available. Nevertheless, this period of time is crucial for the transplant outcome because engraftment, non-relapse mortality, and relapse incidence are greatly dependent upon the pre-transplant management. Based on these premises, in this review, we will go through the path of identification of the MF patients suitable for a transplant, by using disease-specific prognostic scores, and the evaluation of eligibility for a transplant, based on performance, comorbidity, and other combined tools. Then, we will focus on the process of donor and conditioning regimens’ choice. The pre-transplant management of splenomegaly and constitutional symptoms, cytopenias, iron overload and transplant timing will be comprehensively discussed. The principal aim of this review is, therefore, to give a practical guidance for managing MF patients who are potential candidates for allo-HCT.

Reduced intensity hematopoietic stem cell transplantation for myelofibrosis in accelerated-phase

Results of this first report in accelerated-phase myelofibrosis may encourage clinicians to refer these patients for curative treatment.

Accelerated-phase myelofibrosis without prior cytoreduction showed excellent 5-year survival (65%) but higher relapse vs chronic phase.

Accelerated-phase myelofibrosis, currently defined by circulating blasts 10% to 19%, usually confers very high risk for progression and poor outcome. The outcome of hematopoietic stem cell transplantation for accelerated-phase myelofibrosis has not been evaluated yet. We analyzed the outcome of 349 clinically and genetically annotated patients with primary or secondary myelofibrosis undergoing reduced intensity transplantation, of whom 35 had accelerated-phase myelofibrosis. In comparison with chronic-phase (<10% blasts) myelofibrosis, median leukocyte counts were higher, more patients had constitutional symptoms, and RAS mutations were detected more frequently in the accelerated-phase group. After a median follow-up of 5.9 years, estimated 5-year overall survival was 65% (95% confidence interval [CI], 49% to 81%) vs 64% (95% CI, 59% to 69%) for the chronic-phase group (P = .91), and median overall survival was not reached. In terms of relapse-free survival, estimated 5-year outcome for the accelerated-phase group was 49% (95% CI, 32% to 67%) vs 55% (95% CI, 50% to 61%) for the chronic-phase group (P = .65). Estimated 5-year nonrelapse mortality was 20% (95% CI, 8% to 33%) for the accelerated-phase group vs 30% (95% CI, 24% to 35%; P = .25) for the chronic-phase group. In terms of relapse, 5-year incidence was 30% (95% CI, 14% to 46%) for the accelerated-phase group vs 15% (95% CI, 11% to 19%) for the chronic-phase group (P = .02). Results were confirmed in multivariable analysis and propensity score matching. In conclusion, reduced intensity transplantation showed excellent survival but higher relapse for accelerated-phase myelofibrosis.

Momelotinib: an emerging treatment for myelofibrosis patients with anemia

The suite of marked anemia benefits that momelotinib has consistently conferred on myelofibrosis (MF) patients stem from its unique inhibitory activity on the BMP6/ACVR1/SMAD and IL-6/JAK/STAT3 pathways, resulting in decreased hepcidin (master iron regulator) expression, higher serum iron and hemoglobin levels, and restored erythropoiesis. Clinical data on momelotinib from the phase 2 and the two phase 3 SIMPLIFY trials consistently demonstrated high rates of sustained transfusion-independence. In a recent phase 2 translational study, 41% of the patients achieved transfusion independence for ≥ 12 weeks. In the phase 3 trials SIMPLIFY-1 and SIMPLIFY-2, 17% more JAK inhibitor-naïve patients and two-fold more JAK inhibitor-treated patients achieved or maintained transfusion independence with momelotinib versus ruxolitinib and best available therapy (89% ruxolitinib), respectively. Anemia is present in approximately a third of MF patients at diagnosis, eventually developing in nearly all patients. The need for red blood cell transfusions is an independent adverse risk factor for both overall survival and leukemic transformation. Presently, FDA-approved medications to address anemia are lacking. Momelotinib is one of the prime candidates to durably address the critical unmet needs of MF patients with moderate/severe anemia. Importantly, momelotinib may have overall survival benefits in frontline and second-line MF patients. MOMENTUM is an international registration-track phase 3 trial further assessing momelotinib’s unique constellation of anemia and other benefits in second-line MF patients; the results of the MOMENTUM trial are keenly awaited and may lead to regulatory approval of momelotinib.

2021 Update on allogeneic hematopoietic stem cell transplant for myelofibrosis: A review of current data and applications on risk stratification and management

The number of patients with myelofibrosis (MF) undergoing an allogeneic hemopoietic stem cell transplantation (HSCT) is increasing: in the analysis of the European Group for Blood and Marrow Transplantation (EBMT) the number of MF has increased from 515 in 2014 to 748 in 2018 . This reflects the fact that HSCT is currently the only curative treatment, capable of inducing prolonged disease‐free survival. Nevertheless, several problems prevent more patients from undergoing an allogeneic HSCT: we will be discussing indications for HSCT, comorbidities, splenomegaly, older age and disease phase. Donor type and stem cell source are less of a problem. Several transplant platforms exist, including different strategies for graft versus host disease (GvHD) prophylaxis, Age tailored conditioning regimens need to be implemented, to allow older and fragile patients to undergo an allogeneic HSCT.