Hematopoietic Cell Transplantation as Curative Therapy for Patients with Myelofibrosis: Long-Term Success in all Age Groups

When and how to transplant in myelofibrosis - recent trends

Allogeneic hematopoietic stem cell transplantation (AHSCT) is currently the only treatment modality that is capable of curing myelofibrosis (MF). Although outcomes of AHSCT have improved vastly in recent years owing to advancements in HLA typing, conditioning regimens, and supportive care, it remains a procedure with a considerable risk in MF patients due to conditioning regimen related toxicity, higher rates of graft failure, infections, and graft versus host disease (GVHD). Recent progress in the treatment and prevention of GVHD with post-transplant cyclophosphamide has also rendered transplantation from alternative donors feasible and safer, thus improving access to patients without HLA-identical donors. Accordingly, all patients with intermediate or high-risk MF today should be referred for potential transplant evaluation to consider the pros and cons of an early versus a delayed transplant strategy. Individual risk assessment in MF is best facilitated by contemporary prognostic models that incorporate both clinical and genetic risk factors. The current review highlights new information regarding risk stratification in MF, anchored by practical algorithms that facilitate patient selection for specific treatment actions, including AHSCT.

Transplant Outcomes in Myelofibrosis: Impact of Donor Type (Cord Blood Grafts Supported by CD34+ selected Cells [Haplo-Cord] Versus Matched Donors)

Despite the established potentially curative role of allogeneic hematopoietic cell transplantation (allo-HCT) in managing myelofibrosis (MF), the choice of alternative donors for patients lacking matched donors remains a challenge, and the optimal graft source in this disease entity continues to be an ongoing debate. We aimed to evaluate the impact of donor type: umbilical cord blood transplant supported with CD34+ selected haploidentical donor (haplo-cord) versus adult matched related donor (MRD) and matched unrelated donor (MUD) in 40 adult patients with primary or secondary MF, including those progressing to accelerated phase (AP) or blast phase (BP), who underwent their first allo-HCT. The primary objective of this study was to analyze the impact of stem cell source on primary endpoints of overall survival (OS), graft-versus-host disease, and non-relapse mortality (NRM). Median follow-up for all alive patients was 53 months (range 0.3-63 months). Nine patients (22.5%) underwent an MRD allo-HCT, 15 patients (37.5%) underwent a MUD allo-HCT, and 16 patients (40%) underwent a haplo-cord allo-HCT. Four patients died without neutrophil engraftment: 3 (19%) in haplo-cord group and one (4%) in MRD/MUD group. The cumulative incidence of absolute neutrophil engraftment by day 60 was 80% (95% CI 45-94) in the haplo-cord group and 92% (95% CI 65-98) in the MRD/MUD group (P = .09). The cumulative incidence of platelet engraftment by day 60 was 59% (95% CI 27-81) in haplo-cord group and 75% (95% CI 51-88) in MRD/MUD group (P = .4). OS was 62% at 1 year (95% CI 49-79) and 34% at 3 years (95% CI 21-55). The 3-year OS was similar between the haplo-cord group and the MRD/MUD (37% versus 32%, P = .9). The 1-year OS for AP/BP patients was 50% (95% CI 27-93) in the haplo-cord group, compared to 40% (95% CI 19-86) in the MRD/MUD. The 1-year OS for chronic phase CP patients was 83% (95% CI 58-100) in the haplo-cord group, compared to 79% (95% CI 60-100) in the MRD/MUD group. The cumulative incidence of relapse at 3 years in the haplo-cord group was 13% (95% CI 1.8-34), and in the MRD/MUD group was 28% (95% CI 10-49) (P = .36). One-year NRM was 38% (95% CI 15-61) in the haplo-cord group and 33% (95% CI 15-52) in the MRD/MUD group. Three-year NRM was 48% (95% CI 19-72) in the haplo-cord group and 54% (95% CI 29-73) in MRD/MUD group (P = .95). We showed no significant difference in OS, relapse, and NRM outcomes after haplo-cord transplant compared to adult matched donors' grafts (MRD or MUD) in MF patients. However, there were more graft failures in patients transplanted with a haplo-cord transplants and delayed engraftments with inadequate haplo myeloid bridges. Despite the small sample size in our study, considering our findings and the availability of other alternative donors, using haplo-cord platforms may no longer be justified for MF unless the UCB engraftment dynamics can be optimized.

Programmed death-ligand 1 expression in patients with primary or secondary myelofibrosis

BACKGROUND

It has been described in mice models that myeloproliferative neoplasm (MPN) with JAK2-V617F mutation has an increased expression of programmed death-ligand 1 (PD-L1) in megakaryocytes leading to cancer immune evasion by inhibiting the T-lymphocytes.

AIMS

To quantify and compare the PD-L1 expression on bone marrow (BM) of patients with MPN JAK2 positive, negative, and normal controls.

METHODS

We collected BM of patients with MPN JAK2 positive, negative and normal controls from 1990 to 2019. We also created a scoring system to quantify PD-L1 expression in megakaryocytes.

RESULTS

We obtained 14 BM with JAK2 positive PMF, 5 JAK2 negative PMF, and 10 patients with normal BM biopsies. PD-L1 expression was higher in the JAK2 positive group compared with the control group with a score of 212.6 versus 121.1 (t-value 2.05, p-value 0.025). In addition, the score was higher in the PMF group regardless of JAK2 mutational status when compared with the control group with score of 205.9 versus 121.1 (t-value 2.12, p-value 0.021). There was no difference in the PD-L1 score between the JAK2 negative versus the control group 187.2 versus 121.1 (t-value 1.02, p-value 0.162).

CONCLUSION

These findings suggest that PMF patients with a JAK2 mutation have a higher PD-L1 expression in megakaryocytes compared with the control group. We postulate that the combination of checkpoint and JAK2 inhibitors may be an active treatment option in JAK2 mutated PMF given the higher PD-L1 expression.

Phenotypic characterization of disease-initiating stem cells in JAK2- or CALR-mutated myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are characterized by uncontrolled expansion of myeloid cells, disease-related mutations in certain driver-genes including JAK2, CALR, and MPL, and a substantial risk to progress to secondary acute myeloid leukemia (sAML). Although behaving as stem cell neoplasms, little is known about disease-initiating stem cells in MPN. We established the phenotype of putative CD34+ /CD38- stem cells and CD34+ /CD38+ progenitor cells in MPN. A total of 111 patients with MPN suffering from polycythemia vera, essential thrombocythemia, or primary myelofibrosis (PMF) were examined. In almost all patients tested, CD34+ /CD38- stem cells expressed CD33, CD44, CD47, CD52, CD97, CD99, CD105, CD117, CD123, CD133, CD184, CD243, and CD274 (PD-L1). In patients with PMF, MPN stem cells often expressed CD25 and sometimes also CD26 in an aberrant manner. MPN stem cells did not exhibit substantial amounts of CD90, CD273 (PD-L2), CD279 (PD-1), CD366 (TIM-3), CD371 (CLL-1), or IL-1RAP. The phenotype of CD34+ /CD38- stem cells did not change profoundly during progression to sAML. The disease-initiating capacity of putative MPN stem cells was confirmed in NSGS mice. Whereas CD34+ /CD38- MPN cells engrafted in NSGS mice, no substantial engraftment was produced by CD34+ /CD38+ or CD34- cells. The JAK2-targeting drug fedratinib and the BRD4 degrader dBET6 induced apoptosis and suppressed proliferation in MPN stem cells. Together, MPN stem cells display a unique phenotype, including cytokine receptors, immune checkpoint molecules, and other clinically relevant target antigens. Phenotypic characterization of neoplastic stem cells in MPN and sAML should facilitate their enrichment and the development of stem cell-eradicating (curative) therapies.

Myeloproliferative Neoplasms, Version 3.2022, NCCN Clinical Practice Guidelines in Oncology

The classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) consist of myelofibrosis, polycythemia vera, and essential thrombocythemia and are a heterogeneous group of clonal blood disorders characterized by an overproduction of blood cells. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for MPN were developed as a result of meetings convened by a multidisciplinary panel with expertise in MPN, with the goal of providing recommendations for the management of MPN in adults. The Guidelines include recommendations for the diagnostic workup, risk stratification, treatment, and supportive care strategies for the management of myelofibrosis, polycythemia vera, and essential thrombocythemia. Assessment of symptoms at baseline and monitoring of symptom status during the course of treatment is recommended for all patients. This article focuses on the recommendations as outlined in the NCCN Guidelines for the diagnosis of MPN and the risk stratification, management, and supportive care relevant to MF.

Effect of fluconazole on the pharmacokinetics of a single dose of fedratinib in healthy adults

Purpose

Fedratinib is an orally administered Janus kinase (JAK) 2–selective inhibitor for the treatment of adult patients with intermediate-2 or high-risk primary or secondary myelofibrosis. In vitro, fedratinib is predominantly metabolized by cytochrome P450 (CYP) 3A4 and to a lesser extent by CYP2C19. Coadministration of fedratinib with CYP3A4 inhibitors is predicted to increase systemic exposure to fedratinib. This study evaluated the effect of multiple doses of the dual CYP3A4 and CYP2C19 inhibitor, fluconazole, on the pharmacokinetics of a single dose of fedratinib.

Methods

In this non-randomized, fixed-sequence, open-label study, healthy adult participants first received a single oral dose of fedratinib 100 mg on day 1. Participants then received fluconazole 400 mg on day 10 and fluconazole 200 mg once daily on days 11–23, with a single oral dose of fedratinib 100 mg on day 18. Pharmacokinetic parameters were calculated for fedratinib administered with and without fluconazole.

Results

A total of 16 participants completed the study and were included in the pharmacokinetic population. Coadministration of fedratinib with fluconazole increased maximum observed plasma concentration (C_max) and area under the plasma concentration–time curve from time 0 to the last quantifiable concentration (AUC_0–t) of fedratinib by 21% and 56%, respectively, compared with fedratinib alone. Single oral doses of fedratinib 100 mg administered with or without fluconazole were well tolerated.

Conclusions

Systemic exposure after a single oral dose of fedratinib was increased by up to 56% when fedratinib was coadministered with fluconazole compared with fedratinib alone.

Trial registry: Clinicaltrials.gov

NCT04702464.

Impact of molecular profiling on the management of patients with myelofibrosis

Myelofibrosis (MF) is a chronic myeloproliferative neoplasm (MPN) characterized by a highly heterogeneous clinical course, which can be complicated by severe constitutional symptoms, massive splenomegaly, progressive bone marrow failure, cardiovascular events, and development of acute leukemia. Constitutive signaling through the JAK-STAT pathway plays a fundamental role in its pathogenesis, generally due to activating mutations of JAK2, CALR and MPL genes (i.e., the MPN driver mutations), present in most MF patients. Next Generation Sequencing (NGS) panel testing has shown that additional somatic mutations can already be detected at the time of diagnosis in more than half of patients, and that they accumulate along the disease course. These mutations, mostly affecting epigenetic modifiers or spliceosome components, may cooperate with MPN drivers to favor clonal dominance or influence the clinical phenotype, and some, such as high molecular risk mutations, correlate with a more aggressive clinical course with poor treatment response. The current main role of molecular profiling in clinical practice is prognostication, principally for selecting high-risk patients who may be candidates for transplantation, the only curative treatment for MF to date. To this end, contemporary prognostic models incorporating molecular data are useful tools to discriminate different risk categories. Aside from certain clinical situations, decisions regarding medical treatment are not based on patient molecular profiling, yet this approach may become more relevant in novel treatment strategies, such as the use of vaccines against the mutant forms of JAK2 or CALR, or drugs directed against actionable molecular targets.

Managing patients with myelofibrosis and thrombocytopenia

INTRODUCTION

: Given the progressive nature of myelofibrosis, the incidence of thrombocytopenia increases over time. Furthermore, approved drugs ruxolitinib and fedratinib, induce thrombocytopenia. Hence, treatment of myelofibrosis patients with low platelet counts is an unmet need.

AREAS COVERED

: This review summarizes the current and emerging treatment options available for patients with myelofibrosis and thrombocytopenia. In the first section of this review, we summarized the use of JAK inhibitors in patients with thrombocytopenia, and in the second part, we focused on use of therapies other than JAK Inhibitors such as steroids, immunomodulatory agents, androgens and other novel agents.

EXPERT OPINION

: Up to 25% of patients with myelofibrosis have platelet counts below 100,000 at presentation. Patients with thrombocytopenia are more likely to be anemic and PRBC transfusion-dependent, as well as have high-risk disease characteristics and a poor overall survival rate.. Among all JAK inhibitors studied in phase 3 clinical trials, pacritinib seems not to induce significant thrombocytopenia while maintaining a good spleen response. Severe thrombocytopenia is a major impediment to myelofibrosis therapy, and more research, particularly on novel therapeutic agents aimed at cytopenic patient populations, is needed.

Novel treatments for myelofibrosis: beyond JAK inhibitors

Myelofibrosis is a chronic hematologic malignancy characterized by constitutional symptoms, bone marrow fibrosis, extramedullary hematopoiesis resulting in splenomegaly and a propensity toward leukemic progression. Given the central role of the JAK-STAT pathway in the pathobiology of myelofibrosis, JAK inhibitors are the mainstay of current pharmacologic management. Although these therapies have produced meaningful improvements in splenomegaly and symptom burden, JAK inhibitors do not significantly impact disease progression. In addition, many patients are ineligible because of disease-related cytopenias, which are exacerbated by JAK inhibitors. Therefore, there is a continued effort to identify targets outside the JAK-STAT pathway. In this review, we discuss novel therapies in development for myelofibrosis. We focus on the preclinical rationale, efficacy and safety data for non-JAK inhibitor therapies that have published or presented clinical data. Specifically, we discuss agents that target epigenetic modification (pelabresib, bomedemstat), apoptosis (navitoclax, navtemdalin), signaling pathways (parsaclisib), bone marrow fibrosis (AVID200, PRM-151), in addition to other targets including telomerase (imetelstat), selective inhibitor of nuclear transport (selinexor), CD123 (tagraxofusp) and erythroid maturation (luspatercept). We end by providing commentary on the ongoing and future therapeutic development in myelofibrosis.

Emerging drugs for the treatment of myelofibrosis: phase II & III clinical trials

INTRODUCTION

Myelofibrosis is a clonal hematologic malignancy with clinical manifestations that include cytopenias, debilitating constitutional symptoms, splenomegaly, bone marrow fibrosis and a propensity toward leukemic progression. While allogeneic hematopoietic stem cell transplantation can be curative, this therapy is not available for the majority of patients. Ruxolitinib and fedratinib are approved JAK2 inhibitors that have produced meaningful benefits in terms of spleen reduction and symptom improvement, but there remain several unmet needs.

AREAS COVERED

We discuss novel therapies based upon published data from phase II or III clinical trials. Specifically, we cover novel JAK inhibitors (momelotinib and pacritinib), and agents that target bromodomain and extra-terminal domain (pelabresib), the antiapoptotic proteins BCL-2/BCL-xL (navitoclax), MDM2 (navtemadlin), phosphatidylinositol 3-kinase (parsaclisib), or telomerase (imetelstat).

EXPERT OPINION

Patients with disease related cytopenias are ineligible for currently approved JAK2 inhibitors. However, momelotinib and pacritinib may be able to fill this void. Novel therapies are being evaluated in the upfront setting to improve the depth and duration of responses with ruxolitinib. Future evaluation of agents must be judged on their potential to modify disease progression, which current JAK2 inhibitors lack. Combination therapy, possibly with an immunotherapeutic agent might serve as key components of future myelofibrosis treatment options.

New Markers of Disease Progression in Myelofibrosis

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm due to the clonal proliferation of a hematopoietic stem cell. The vast majority of patients harbor a somatic gain of function mutation either of JAK2 or MPL or CALR genes in their hematopoietic cells, resulting in the activation of the JAK/STAT pathway. Patients display variable clinical and laboratoristic features, including anemia, thrombocytopenia, splenomegaly, thrombotic complications, systemic symptoms, and curtailed survival due to infections, thrombo-hemorrhagic events, or progression to leukemic transformation. New drugs have been developed in the last decade for the treatment of PMF-associated symptoms; however, the only curative option is currently represented by allogeneic hematopoietic cell transplantation, which can only be offered to a small percentage of patients. Disease prognosis is based at diagnosis on the classical International Prognostic Scoring System (IPSS) and Dynamic-IPSS (during disease course), which comprehend clinical parameters; recently, new prognostic scoring systems, including genetic and molecular parameters, have been proposed as meaningful tools for a better patient stratification. Moreover, new biological markers predicting clinical evolution and patient survival have been associated with the disease. This review summarizes basic concepts of PMF pathogenesis, clinics, and therapy, focusing on classical prognostic scoring systems and new biological markers of the disease.

Survival following allogeneic transplant in patients with myelofibrosis

Allogeneic hematopoietic cell transplantation (HCT) is the only curative therapy for myelofibrosis (MF). In this large multicenter retrospective study, overall survival (OS) in MF patients treated with allogeneic HCT (551 patients) and without HCT (non-HCT) (1377 patients) was analyzed with Cox proportional hazards model. Survival analysis stratified by the Dynamic International Prognostic Scoring System (DIPSS) revealed that the first year of treatment arm assignment, due to upfront risk of transplant-related mortality (TRM), HCT was associated with inferior OS compared with non-HCT (non-HCT vs HCT: DIPSS intermediate 1 [Int-1]: hazard ratio [HR] = 0.26, P < .0001; DIPSS-Int-2 and higher: HR, 0.39, P < .0001). Similarly, in the DIPSS low-risk MF group, due to upfront TRM risk, OS was superior with non-HCT therapies compared with HCT in the first-year post treatment arm assignment (HR, 0.16, P = .006). However, after 1 year, OS was not significantly different (HR, 1.38, P = .451). Beyond 1 year of treatment arm assignment, an OS advantage with HCT therapy in Int-1 and higher DIPSS score patients was observed (non-HCT vs HCT: DIPSS-Int-1: HR, 2.64, P < .0001; DIPSS-Int-2 and higher: HR, 2.55, P < .0001). In conclusion, long-term OS advantage with HCT was observed for patients with Int-1 or higher risk MF, but at the cost of early TRM. The magnitude of OS benefit with HCT increased as DIPSS risk score increased and became apparent with longer follow-up.

Next Generation Therapeutics for the Treatment of Myelofibrosis

Myelofibrosis is a myeloproliferative neoplasm characterized by splenomegaly, constitutional symptoms, bone marrow fibrosis, and a propensity towards transformation to acute leukemia. JAK inhibitors are the only approved therapy for myelofibrosis and have been successful in reducing spleen and symptom burden. However, they do not significantly impact disease progression and many patients are ineligible due to coexisting cytopenias. Patients who are refractory to JAK inhibition also have a dismal survival. Therefore, non-JAK inhibitor-based therapies are being explored in pre-clinical and clinical settings. In this review, we discuss novel treatments in development for myelofibrosis with targets outside of the JAK-STAT pathway. We focus on the mechanism, preclinical rationale, and available clinical efficacy and safety information of relevant agents including those that target apoptosis (navitoclax, KRT-232, LCL-161, imetelstat), epigenetic modulation (CPI-0610, bomedemstat), the bone marrow microenvironment (PRM-151, AVID-200, alisertib), signal transduction pathways (parsaclisib), and miscellaneous agents (tagraxofusp. luspatercept). We also provide commentary on the future of therapeutic development in myelofibrosis.

Overview of Myeloproliferative Neoplasms: History, Pathogenesis, Diagnostic Criteria, and Complications

Myeloproliferative disorders are a group of diseases morphologically linked by terminal myeloid cell expansion that frequently evolve from one clinical phenotype to another and eventually progress to acute myeloid leukemia. Diagnostic criteria for the Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) have been established by the World Health Organization and they are recognized as blood cancers. MPNs have a complex and incompletely understood pathogenesis that includes systemic inflammation, clonal hematopoiesis, and constitutive activation of the JAK-STAT pathway. Complications, such as thrombosis and progression to overt forms of myelofibrosis and acute leukemia, contribute significantly to morbidity and mortality of patients with MPN.

Full donor chimerism after allogeneic hematopoietic stem cells transplant for myelofibrosis: The role of the conditioning regimen

The aim of this retrospective study was to assess the rate of full donor chimerism (F-DC) in patients with myelofibrosis, prepared for an allogeneic stem cell transplant, with one or two alkylating agents. We analyzed 120 patients with myelofibrosis, for whom chimerism data were available on day +30. There were two groups: 42 patients were conditioned with one alkylating agent (ONE-ALK), either thiotepa or busulfan or melphalan, in combination with fludarabine, whereas 78 patients were prepared with two alkylating agents, thiotepa busulfan and fludarabine (TBF). Patients receiving TBF were older (57 vs 52 years), were less frequently splenectomized pre-HSCT (31% vs 59%), had more frequently intermediate-2/high DIPSS scores (90% vs 74%), were grafted more frequently from alternative donors (83% vs 33%) and received more frequently ruxolitinib pre-HSCT (26% vs 7%). The proportion of patients with F-DC on day +30, in the TBF vs the ONE-ALK group, was respectively 87% vs 45% (P < .001). The 5-year cumulative incidence of relapse was 9% in the TBF group, vs 43% for the ONE-ALK group (P < .001). The 5-year actuarial disease-free survival was 63% for TBF and 38% for the ONE-ALK group (P = .004). In conclusion, early full donor chimerism is a prerequisite for long term control of disease in patients with myelofibrosis, undergoing an allogeneic HSCT. The combination of two alkylating agents in the conditioning regimen, provides a higher chance of achieving full donor chimerism on day+30, and thus a higher chance of long term disease free survival.

Fedratinib-induced orbital inflammation

A 69-year-old man with myelofibrosis presented with a two-day history of left periorbital swelling, blurred vision, and non-radiating dull orbital pain. On examination, there was restricted left-sided extraocular motility with conjunctival injection, chemosis, and periorbital edema. Magnetic resonance imaging demonstrated left-sided pre- and post-septal fat stranding concerning for orbital cellulitis. Two weeks before symptom onset, the patient began fedratinib therapy for myelofibrosis but discontinued this medication upon hospital admission. After restarting fedratinib, he presented with similar right-sided ophthalmic signs. A review of his medication history revealed a temporal relationship between symptom onset and fedratinib use. After medication discontinuation, his symptoms improved rapidly.

Treosulfan-Based Conditioning Regimen for Second Allograft in Patients with Myelofibrosis

Simple Summary

Currently, the only curative therapy in myelofibrosis is allogeneic hematopoietic stem cell transplantation. Donor lymphocyte infusion and second stem cell transplantation are the two main treatment options for myelofibrosis patients who relapse after the first transplantation. The optimal conditioning regimen for the second transplantation in myelofibrosis patients is not well defined. Our study aimed to address this question and showed that treosulfan-based conditioning for second allograft in relapsed myelofibrosis patients resulted in longtime freedom from disease in about 50% of the patients. This data supports the second allogeneic hematopoietic stem cell transplantation with a less toxic treosulfan-based conditioning regimen that is effective in relapsed, donor lymphocyte infusion resistant myelofibrosis patients with long term low transplant-related mortality and relapse rates.

Abstract

Relapse after allogeneic hematopoietic stem cell transplantation (AHSCT) in myelofibrosis (MF) patients remains as a significant issue despite advances in transplantation procedures and significant prolongation in survival. Second AHSCT is a potential treatment option but associated with high treatment-related mortality and novel less toxic conditioning regimens are needed. In 33 MF patients with relapse after AHSCT and failure to donor lymphocyte infusion (DLI) we investigated treosulfan (36–42 g/m²) in combination with fludarabine and anti-thymocyte globulin (ATG) as conditioning regimen for a second AHSCT with matched related (n = 2), unrelated (n = 23), or mismatched unrelated (n = 8) donors. All patients achieved leukocyte engraftment after a median of 11 days, and 56 ± 13% experienced acute GVHD grade II–IV at day 100. The therapy-related mortality at day 100 and at 3 years was 16% and 31%, respectively. The cumulative incidence of relapse at 5 years was 16%, resulting in a 5-year disease-free and overall survival of 45% and 47%, respectively. Treosulfan-based conditioning for second allograft in relapsed MF patients resulted in about 50% of the patients in long-term freedom from disease.

Incidence and Outcome of Late Relapse after Allogeneic Stem Cell Transplantation for Myelofibrosis

In this cross-sectional study, we retrospectively evaluated the files of 227 patients with myelofibrosis who underwent transplantation between 1994 and 2015 for relapse later than 5 years after allogeneic stem cell transplantation (SCT). A total of 94 patients who were alive and in remission at 5 years were identified with follow-up of at least 5 years (median, 9.15 years) after SCT. Thirteen patients (14%) experienced late molecular (n = 6) or hematologic (n = 7) relapse at a median of 7.1 years while 81 patients did not experience relapse. Relapse patients received either donor lymphocyte infusion (DLI) (n = 7) and/or second transplantation (n = 4). Of those, 72.7% achieved again full donor cell chimerism and molecular remission, and after a median follow-up of 45 months, the 3-year overall survival rates for patients with or without relapse were 90.9% (95% confidence interval [CI], 77% to 100%) and 98.8% (95% CI, 96% to 100%), respectively (P = .13). We conclude that late relapse occurs in about 14% of the patients and the majority can be successfully salvaged with DLI and/or second allograft. All patients with molecular relapse are alive and support the long-time molecular monitoring in myelofibrosis patients after allogeneic SCT.

STAT5 is Expressed in CD34+/CD38- Stem Cells and Serves as a Potential Molecular Target in Ph-Negative Myeloproliferative Neoplasms

Janus kinase 2 (JAK2) and signal transducer and activator of transcription-5 (STAT5) play a key role in the pathogenesis of myeloproliferative neoplasms (MPN). In most patients, JAK2 V617F or CALR mutations are found and lead to activation of various downstream signaling cascades and molecules, including STAT5. We examined the presence and distribution of phosphorylated (p) STAT5 in neoplastic cells in patients with MPN, including polycythemia vera (PV, n = 10), essential thrombocythemia (ET, n = 15) and primary myelofibrosis (PMF, n = 9), and in the JAK2 V617F-positive cell lines HEL and SET-2. As assessed by immunohistochemistry, MPN cells displayed pSTAT5 in all patients examined. Phosphorylated STAT5 was also detected in putative CD34+/CD38- MPN stem cells (MPN-SC) by flow cytometry. Immunostaining experiments and Western blotting demonstrated pSTAT5 expression in both the cytoplasmic and nuclear compartment of MPN cells. Confirming previous studies, we also found that JAK2-targeting drugs counteract the expression of pSTAT5 and growth in HEL and SET-2 cells. Growth-inhibition of MPN cells was also induced by the STAT5-targeting drugs piceatannol, pimozide, AC-3-019 and AC-4-130. Together, we show that CD34+/CD38- MPN-SC express pSTAT5 and that pSTAT5 is expressed in the nuclear and cytoplasmic compartment of MPN cells. Whether direct targeting of pSTAT5 in MPN-SC is efficacious in MPN patients remains unknown.

Assessment of Quality of Life following Allogeneic Stem Cell Transplant for Myelofibrosis

Patient-reported outcomes (PROs) for patients with myelofibrosis (MF) have been well characterized, but little is known about quality of life (QoL) following allogeneic stem cell transplantation (allo-SCT). Medical data and PRO measures were collected before transplant and at day 30, day 100, and 1 year after allo-SCT. PRO measures include Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF), Brief Fatigue Inventory, Global Assessment of Change, and Functional Assessment of Cancer Therapy-Bone Marrow Transplant. Forty-four patients who had baseline QoL and at least 1 post-transplant assessment were included. The median age of the patients was 62.5 years (range, 35 to 74 years). At baseline, the mean MPN Total Symptom Score was 28.0, and at day 30, day 100, and 1 year, it was 25.4, 32.3, and 24.3, respectively. However, in myeloproliferative neoplasm-specific symptoms, such as itching, night sweats, bone pain, and fever, a statistically significant improvement was observed for at least 1 time point following transplant. At day 30, 10 (26.3%) patients reported a little/moderately/very much better overall QoL since their transplant, and 26 (68.45%) had a little/moderately/very much worse QoL. At day 100, 10 (30.3%) reported better QoL and 19 (57.6%) reported worsening since transplant. By 1 year, 16 (61.5%) reported feeling better. Our study shows that there is very little change in symptom burden at 1 year following transplant in general, but MF-specific symptoms showed improvement. By 1 year, 61% felt that their QoL was better than it was before transplant.

Survival outcomes in myelofibrosis patients treated with ruxolitinib: A population-based cohort study in Sweden and Norway

Objective

To estimate survival in Swedish and Norwegian myelofibrosis (MF) patients who received ruxolitinib.

Methods

Swedish and Norwegian patients with MF diagnosis in the National Cancer Registries (Sweden: 2001‐2015; Norway: 2002‐2016) and ≥1 record of ruxolitinib in the Prescribed Drug Registries (2013‐2017) were included. Patients were followed from ruxolitinib initiation until death or end of follow‐up; those who discontinued ruxolitinib were followed from ruxolitinib discontinuation. Relative survival (RS) and excess mortality rate ratios (EMRRs) were calculated vs a matched general population. Average loss in life expectancy (LEL) was predicted using flexible parametric models.

Results

Among patients who initiated ruxolitinib (n = 190), 1‐ and 4‐year RS were 0.80 (95% confidence interval [CI]: 0.74, 0.86) and 0.52 (95% CI: 0.42, 0.64), respectively, and LEL was 11 years. EMRR was greater in patients aged >70 vs <60 years (3.16; 95% CI: 1.34‐7.40). Among patients who discontinued ruxolitinib (n = 71), median RS was 16.0 months (95% CI: 6.3, NE), and LEL was 12 years. After ruxolitinib treatment discontinuation, Swedish patients (n = 37) received glucocorticoids, hydroxyurea, busulfan, danazol and lenalidomide.

Conclusion

Swedish and Norwegian MF patients who discontinued ruxolitinib had dismal survival outcomes and limited subsequent treatment options, highlighting the need for improved therapies.

Myelofibrosis in 2019: moving beyond JAK2 inhibition

Myelofibrosis (MF) is a myeloproliferative neoplasm characterized by ineffective clonal hematopoiesis, splenomegaly, bone marrow fibrosis, and the propensity for transformation to acute myeloid leukemia. The discovery of mutations in JAK2, CALR, and MPL have uncovered activated JAK-STAT signaling as a primary driver of MF, supporting a rationale for JAK inhibition. However, JAK inhibition alone is insufficient for long-term remission and offers modest, if any, disease-modifying effects. Given this, there is great interest in identifying mechanisms that cooperate with JAK-STAT signaling to predict disease progression and rationally guide the development of novel therapies. This review outlines the latest discoveries in the biology of MF, discusses current clinical management of patients with MF, and summarizes the ongoing clinical trials that hope to change the landscape of MF treatment.

Immune Checkpoint Blockade Enhances Shared Neoantigen-Induced T-cell Immunity Directed against Mutated Calreticulin in Myeloproliferative Neoplasms

Somatic frameshift mutations in the calreticulin (CALR) gene are key drivers of cellular transformation in myeloproliferative neoplasms (MPN). All patients carrying these mutations (CALR ⁺ MPN) share an identical sequence in the C-terminus of the mutated CALR protein (mut-CALR), with the potential for utility as a shared neoantigen. Here, we demonstrate that although a subset of patients with CALR ⁺ MPN develop specific T-cell responses against the mut-CALR C-terminus, PD-1 or CTLA4 expression abrogates the full complement of responses. Significantly, blockade of PD-1 and CLTA4 ex vivo by mAbs and of PD-1 in vivo by pembrolizumab administration restores mut-CALR-specific T-cell immunity in some patients with CALR ⁺ MPN. Moreover, mut-CALR elicits antigen-specific responses from both CD4⁺ and CD8⁺ T cells, confirming its broad applicability as an immunogen. Collectively, these results establish mut-CALR as a shared, MPN-specific neoantigen and inform the design of novel immunotherapies targeting mut-CALR. SIGNIFICANCE: Current treatment modalities for MPN are not effective in eliminating malignant cells. Here, we show that mutations in the CALR gene, which drive transformation in MPN, elicit T-cell responses that can be further enhanced by checkpoint blockade, suggesting immunotherapies could be employed to eliminate CALR ⁺ malignant cells in MPN.This article is highlighted in the In This Issue feature, p. 1143.

Reduced intensity allogeneic stem cell transplantation for younger patients with myelofibrosis

Allogeneic stem cell transplantation (alloSCT) is a curative procedure for myelofibrosis. Elderly people are mainly affected, limiting the feasibility of myeloablative regimens. The introduction of reduced-intensity conditioning (RIC) made alloSCT feasible for older patients. Nevertheless, the incidence of myelofibrosis is not negligible in young patients, who are theoretically able to tolerate high-intensity therapy. Very few data are available about the efficacy of RIC-alloSCT in younger myelofibrosis patients. This study included 56 transplanted patients aged <55 years. Only 30% had a human leucocyte antigen (HLA)-matched sibling donor, the others were transplanted from a fully-matched (36%) or partially-matched (34%) unrelated donor. All transplants were conditioned according the European Society for Blood and Marrow Transplantation protocol: busulfan-fludarabine + anti-thymocyte globulin, followed by ciclosporin and mycophenolate. One patient experienced primary graft failure. Incidence of graft-versus-host disease grade II-IV was 44% (grade III/IV 23%). One-year non-relapse mortality was 7% and the 5-year cumulative incidence of relapse was 19%. After a median follow-up of 8·6 years, the estimated 5-year progression-free survival and overall survival (OS) was 68% and 82%, respectively. Patients with fully-matched donor had a 5-year OS of 92%, in contrast to 68% for those with a mismatched donor (P = 0·03). The most important outcome-determining factor is donor HLA-matching. In conclusion, RIC-alloSCT ensures optimal engraftment and low relapse rate in younger myelofibrosis patients, enabling the possibility of cure in this group.

Comparison of Outcomes of Allogeneic Transplantation for Primary Myelofibrosis among Hematopoietic Stem Cell Source Groups

The choice of alternative donor is a major issue in allogeneic hematopoietic stem cell transplantation (HSCT) for patients with primary myelofibrosis (PMF) without an HLA-matched related donor. We conducted this retrospective study using the Japanese national registry data for 224 PMF patients to compare the outcomes of first allogeneic HSCT from HLA-matched related donor bone marrow (Rtd-BM), HLA-matched related donor peripheral blood stem cells (Rtd-PB), HLA-matched unrelated donor bone marrow (UR-BM), unrelated umbilical cord blood (UR-UCB), and other hematopoietic stem cell grafts. Nonrelapse mortality (NRM) rates at 1 year after Rtd-BM, Rtd-PB, UR-BM, UR-UCB, and other transplantations were 16%, 36%, 30%, 41%, and 48%, respectively. Multivariate analysis identified UR-UCB transplantation, other transplantation, frequent RBC transfusion before transplantation, and frequent platelet (PLT) transfusion before transplantation as predictive of higher NRM. Relapse rates at 1 year after Rtd-BM, Rtd-PB, UR-BM, UR-UCB, and other transplantation were 14%, 17%, 11%, 14%, and 15%, respectively. No specific factor was associated with the incidence of relapse. Overall survival (OS) at 1 and 4 years after Rtd-BM, Rtd-PB, UR-BM, UR-UCB, and other transplantation were 81% and 71%, 58% and 52%, 61% and 46%, 48% and 27%, and 48% and 41%, respectively. Multivariate analysis identified older patient age, frequent RBC transfusion before transplantation, and frequent PLT transfusion before transplantation as predictive of lower OS. In conclusion, UR-UCB transplantation, as well as UR-BM transplantation, can be selected for PMF patients without an HLA-identical related donor. However, careful management is required for patients after UR-UCB transplantation because of the high NRM. Further studies including more patients after HLA-haploidentical related donor and HLA-mismatched unrelated donor transplantation would provide more valuable information for patients with PMF when making decisions regarding the choice of alternative donor.

What the internist should know about stem cell transplant in the elderly patient

Most hematological malignancies are increasing in frequency with age. Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative therapeutic option for patients with malignant and non-malignant hematological diseases. The treatment of elderly patients with advanced hematological malignancies has expanded to include reduced intensity conditioning allo-HCT. Physicians increasingly refer older patients for allo-HCT due to more experience and improved supportive care in allo-HCT. This review article discusses the available data regarding the feasibility, tolerability, toxicity, and effectiveness of allo-HCT in different hematological diseases in the elderly. Over the past decade, utilization and survival after allo-HCT have increased in patients ≥70 years. Selected adults ≥70 years with hematological diseases should be evaluated for transplantation.

Patient Perspectives Regarding Allogeneic Bone Marrow Transplantation in Myelofibrosis

Hematopoietic stem cell transplantation (HCT) is a curative treatment for patients with myelofibrosis (MF); however, many HCT-eligible patients decline this potentially life-saving procedure. The reasons behind this decision are not clear. We sought to survey patients with MF to understand their perspective on HCT. A 63-question survey was posted on myeloproliferative neoplasm patient advocacy websites. A total of 129 patients with MF responded to the survey. Among these patients, 49 (41%) were referred for HCT, and 41(32%) attended the transplantation consult. Of the patients who attended the transplantation consult, 24 (59%) did not plan on going on to HCT, and 16 (41%) intended to proceed with HCT. Reasons for the decision to not undergo transplantation included the desire to not be ill, desire to not spend time in the hospital, and concerns about overall quality of life. Specifically, concerns related to financial impact and the risk of graft-versus-host disease (GVHD) were expressed. Patients who decided to proceed with HCT felt that this would extend their survival and allow them to be around family for longer. This is the first survey to investigate patient perceptions regarding HCT for MF. Less than one-half of the patients were referred for HCT, and of those, less than one-half planned on proceeding with the transplantation, suggesting that many patients do not receive this life-saving procedure. Further exploration of the basis of patients' reluctance to proceed with HCT is warranted.

Recommendations on the use of ruxolitinib for the treatment of myelofibrosis

OBJECTIVES

Myelofibrosis (MF) is a severe disease, with decreased life expectancy and heavy symptom burden. Ruxolitinib is the only approved pharmacotherapy for the treatment of MF patients. In Belgium, ruxolitinib is only reimbursed for MF patients with splenomegaly for whom the disease is categorized as intermediate-2 or high risk. The improvement of symptoms without spleen volume reduction is not considered sufficient to continue treatment. The aim of this manuscript is to provide guidance for the safe and effective administration of ruxolitinib, considering the particularities of the Belgian reimbursement criteria.

METHODS

Our recommendations are based on a consensus reached during two meetings, where available data and observations derived from clinical experience were discussed.

RESULTS AND DISCUSSION

We recommend changing the current Belgian reimbursement conditions to include the evaluation of disease-related symptoms along with splenomegaly to decide whether ruxolitinib treatment should be continued or not. Indeed, the decrease in disease-related symptoms seems to be an equally important parameter as the decrease in splenic volume in the evaluation of the response to ruxolitinib. We also advocate for the treatment with ruxolitinib of MF patients in lower-risk categories with severe disease-related symptoms, as this drug could greatly improve their quality of life. Optimization of the ruxolitinib dose is recommended to avoid an unnecessary decrease in platelet count or hemoglobin that may jeopardize treatment continuation.

CONCLUSION

With the aim to optimize the treatment of MF patients, the Belgian regulation for ruxolitinib should be revised in terms of reimbursement criteria, dose titration, stopping rules, and patient follow-up.

Significance of thrombocytopenia in patients with primary and postessential thrombocythemia/polycythemia vera myelofibrosis

Severe thrombocytopenia (platelets <50 × 10⁹ /L) is associated with very poor outcome of patients with myelofibrosis (MF). As patients with primary myelofibrosis (PMF) differ from patients with postessential thrombocythemia (PET-MF) and postpolycythemia vera myelofibrosis (PPV-MF), we aimed to evaluate the significance of low platelets among these patients. We present clinical characteristics and outcome of patients with either PMF, PPV-MF, or PET-MF, and thrombocytopenia who presented to our institution between 1984 and 2015. Of 1269 patients (877 PMF, 212 PPV-MF, 180 PET-MF), 11% and 14% had platelets either <50 × 10⁹ /L or between 50-100 × 10⁹ /L, respectively. Patients with platelets <50 × 10⁹ /L were most anemic and transfusion dependent, had highest blast count and unfavorable karyotype. In general, their overall and leukemia-free survival was the shortest with median time of 15 and 13 months, respectively; with incidence of acute leukemia almost twice as high as in the remaining patients (6.9 vs 3.6 cases per 100 person-years). Nevertheless, this observation remains mostly significant for patients with PMF, as those with PEV/PVT-MF have already significantly inferior prognosis with platelets <100 × 10⁹ /L.

β-Arrestin2 mediates progression of murine primary myelofibrosis

Primary myelofibrosis is a myeloproliferative neoplasm associated with significant morbidity and mortality, for which effective therapies are lacking. β-Arrestins are multifunctional adaptor proteins involved in developmental signaling pathways. One isoform, β-arrestin2 (βarr2), has been implicated in initiation and progression of chronic myeloid leukemia, another myeloproliferative neoplasm closely related to primary myelofibrosis. Accordingly, we investigated the relationship between βarr2 and primary myelofibrosis. In a murine model of MPLW515L-mutant primary myelofibrosis, mice transplanted with donor βarr2-knockout (βarr2-/-) hematopoietic stem cells infected with MPL-mutant retrovirus did not develop myelofibrosis, whereas controls uniformly succumbed to disease. Although transplanted βarr2-/- cells homed properly to marrow, they did not repopulate long-term due to increased apoptosis and decreased self-renewal of βarr2-/- cells. In order to assess the effect of acute loss of βarr2 in established primary myelofibrosis in vivo, we utilized a tamoxifen-induced Cre-conditional βarr2-knockout mouse. Mice that received Cre (+) donor cells and developed myelofibrosis had significantly improved survival compared with controls. These data indicate that lack of antiapoptotic βarr2 mediates marrow failure of murine hematopoietic stem cells overexpressing MPLW515L. They also indicate that βarr2 is necessary for progression of primary myelofibrosis, suggesting that it may serve as a novel therapeutic target in this disease.

Myelofibrosis: to transplant or not to transplant?

Hematopoietic cell transplantation (HCT) is the only curative therapeutic modality for myelofibrosis (MF) at present. The optimal timing of HCT is not known in the presence of wider availability of less risky nontransplant therapies such as JAK 1/2 inhibitors. Careful review of patient, disease, and transplant-related factors is required in the appropriate selection of HCT vs the best available nontransplant therapies. We highlight some of the relevant issues and positioning of HCT in light of evolving data on JAK 1/2 inhibitors. The goal of this study is to provide the reader with updated evidence of HCT for MF, recognizing that knowledge in this area is limited by the absence of comparative studies between HCT and nontransplant therapies. Prospective studies are needed for better information on: the determination of optimal timing and conditioning regimens, the best way to integrate JAK inhibitors in the HCT protocols, and the impact of JAK inhibitors on graft-versus-host disease.

Allogeneic hematopoietic cell transplantation in patients with myelofibrosis: A single center experience

Myelofibrosis (MF) is a rare disease responsible for an increasing ineffective hematopoesis by a progressive fibrosing process in the bone marrow. The only curative treatment option is allogeneic hematopoietic cell transplantation (HCT). In this single-center analysis, we evaluated retrospectively 54 consecutive patients suffering from primary or secondary MF which underwent HCT from 1997 to 2014 after either myeloablative (MAC, n = 19) or reduced-intensity conditioning (RIC, n = 35). Overall survival (OS) and disease-free survival (DFS) after 3 years was 54/53 % for RIC versus 63/58 % for MAC (p = 0.8/0.97). Cumulative incidence of relapse was 34 % after RIC and 8 % after MAC (p = 0.16). Three-year non-relapse mortality (NRM) was 15 % after RIC and 34 % after MAC (p = 0.29). We found that RIC was associated with a lower incidence of acute graft versus host disease (GvHD; II-IV 26 vs. 0 %, p = 0.004). Evaluation of prognostic relevance of the Dynamic International Prognostic Scoring System (DIPSS) score showed a significant better OS in patient with risk score ≤3 versus >3 (after 3 years, 71 vs. 39 %, p = 0.008). While similar OS and DFS were observed with MAC or RIC, the use of RIC resulted in lower incidence of acute GvHD. RIC regimens may be therefore the preferred conditioning approach for allogeneic HCT in patients with MF.

Myelofibrosis-When Do We Select Transplantation or Non-transplantation Therapeutic Options?

Janus kinase 1/2 (JAK1/2) inhibitor therapy is effective in alleviating myelofibrosis (MF)-related symptoms. However, at present, the only curative therapy for MF patients is hematopoietic cell transplantation (HCT). The decision of whether to proceed with HCT, which carries significant risks, or continue with JAK inhibitor therapy is a complicated one. Nevertheless, careful assessment of patient, disease, and transplant-related factors can guide this decision on a case-by-case basis. Difficult questions arise in the decision-making process such as age limits, whether lower-risk patients are suitable candidates, and HCT in patients responding well to JAK inhibitor therapy. The optimal timing of transplant is a major dilemma in the management of MF patients who are responding to or are stable on JAK inhibitor therapy. In this paper, we provide our perspective on selection of transplant versus non-transplant therapies in the management of MF.