Clinical and bone marrow effects of interferon alfa therapy in myelofibrosis with myeloid metaplasia

Pegylated Interferons: Still a Major Player for the Treatment of Myeloproliferative Neoplasms

Over the past 35 years, interferons have been explored in various formulations for the management of Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), such as essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis, and remain a key tool in caring for patients with these diseases. These agents are excellent cytoreductive agents with high rates of hematologic response, are helpful in symptom management, and have a long track record of safety and manageable toxicities. More recently, they have shown promise in sustaining responses over many years, with associated reductions in driver mutations (JAK2, MPL, CALR) of these diseases, particularly in PV and ET. Since reductions in molecular mutant allele burden have been correlated with several response outcomes such as reductions in both thrombotic risk and disease progression, there is emerging proof that interferons may offer disease-modifying activity. These long-term benefits and their use as the preferred agent in young pregnant women who need cytoreduction make interferons often the first choice in young adult population who harbor a lifetime risk of progression. Looking forward, the prospect of sustained treatment-free responses, like chronic myeloid leukemia after deep molecular response, and normal life expectancy may also be on the frontier. Despite relative rookies such as JAK inhibitors in the MPN landscape, the veteran in the game, interferon, remains a key player.

Momelotinib expands the therapeutic armamentarium for myelofibrosis: Impact on hierarchy of treatment choices

The primary objective of treatment in myelofibrosis (MF) is prolongation of life, which is currently accomplished only by allogeneic hematopoietic stem cell transplantation (AHSCT). Determination of optimal timing for AHSCT is facilitated by molecular risk stratification. Non-transplant treatment options in MF are palliative in scope and include Janus kinase 2 (JAK2) inhibitors (JAKi): momelotinib (FDA approved on September 15, 2023), ruxolitinib (November 16, 2011), fedratinib (August 16, 2019), and pacritinib (February 28, 2022); all four JAKi are effective in reducing spleen size and alleviating symptoms, considered a drug class effect and attributed to their canonical JAK-STAT inhibitory mechanism of action. In addition, momelotinib exhibits erythropoietic effect, attributed to alleviation of ineffective erythropoiesis through inhibition of activin A receptor type-I (ACVR1). In transplant-ineligible or deferred patients, the order of treatment preference is based on specific symptoms and individual assessment of risk tolerance. Because of drug-induced immunosuppression and other toxicities attributed to JAKi, we prefer non-JAKi drugs as initial treatment for MF-associated anemia that is not accompanied by treatment-requiring splenomegaly or constitutional symptoms. Otherwise, it is reasonable to consider momelotinib as the first-line JAKi treatment of choice, in order to target the triad of quality-of-life offenders in MF: anemia, splenomegaly, and constitutional symptoms/cachexia. For second-line therapy, we favor ruxolitinib, over fedratinib, based on toxicity profile. Pacritinib and fedratinib provide alternative options in the presence of severe thrombocytopenia or ruxolitinib-resistance/intolerance, respectively. Splenectomy remains a viable option for drug-resistant symptomatic splenomegaly and cytopenia.

Primary myelofibrosis: 2021 update on diagnosis, risk-stratification and management

DISEASE OVERVIEW

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm (MPN) characterized by stem cell-derived clonal myeloproliferation that is often but not always accompanied by JAK2, CALR, or MPL mutations. Additional disease features include bone marrow reticulin/collagen fibrosis, aberrant inflammatory cytokine expression, anemia, hepatosplenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression, and shortened survival.

DIAGNOSIS

Bone marrow morphology is the primary basis for diagnosis. Presence of JAK2, CALR, or MPL mutation, expected in around 90% of the patients, is supportive but not essential for diagnosis; these mutations are also prevalent in the closely related MPNs, namely polycythemia vera (PV) and essential thrombocythemia (ET). The 2016 World Health Organization classification system distinguishes "prefibrotic" from "overtly fibrotic" PMF; the former might mimic ET in its presentation. Furthermore, approximately 15% of patients with ET or PV might progress into a PMF-like phenotype (post-ET/PV MF) during their clinical course.

ADVERSE MUTATIONS

SRSF2, ASXL1, and U2AF1-Q157 mutations predict inferior survival in PMF, independent of each other and other risk factors. RAS/CBL mutations predicted resistance to ruxolitinib therapy.

ADVERSE KARYOTYPE

Very high risk abnormalities include -7, inv (3), i(17q), +21, +19, 12p-, and 11q-.

RISK STRATIFICATION

Two new prognostic systems for PMF have recently been introduced: GIPSS (genetically-inspired prognostic scoring system) and MIPSS70+ version 2.0 (MIPSSv2; mutation- and karyotype-enhanced international prognostic scoring system). GIPSS is based exclusively on mutations and karyotype. MIPSSv2 includes, in addition, clinical risk factors. GIPSS features four and MIPSSv2 five risk categories.

RISK-ADAPTED THERAPY

Observation alone is advised for MIPSSv2 "low" and "very low" risk disease (estimated 10-year survival 56%-92%); allogeneic hematopoietic stem cell transplant (AHSCT) is the preferred treatment for "very high" and "high" risk disease (estimated 10-year survival 0%-13%); treatment-requiring patients with intermediate-risk disease (estimated 10-year survival 30%) are best served by participating in clinical trials. In non-transplant candidates, conventional treatment for anemia includes androgens, prednisone, thalidomide, and danazol; for symptomatic splenomegaly, hydroxyurea and ruxolitinib; and for constitutional symptoms, ruxolitinib. Fedratinib, another JAK2 inhibitor, has now been FDA-approved for use in ruxolitinib failures. Splenectomy is considered for drug-refractory splenomegaly and involved field radiotherapy for non-hepatosplenic EMH and extremity bone pain.

NEW DIRECTIONS

A number of new agents, alone or in combination with ruxolitinib, are currently under investigation for MF treatment (ClinicalTrials.gov); preliminary results from some of these clinical trials were presented at the 2020 ASH annual meeting and highlighted in the current document.

Modern management of splenomegaly in patients with myelofibrosis

Myelofibrosis (MF) is a chronic myeloproliferative neoplasm which can lead to massive splenomegaly secondary to extramedullary hematopoiesis. Patients frequently exhibit debilitating symptoms including pain and early satiety, in addition to cellular sequestration causing severe cytopenias. JAK 1/2 inhibitors, such as ruxolitinib and fedratinib, are the mainstay of therapy and produce significant and durable reductions in spleen volume. However, many patients are not eligible for JAK 2 inhibitor therapy or become refractory to treatment over time. Novel therapies are in development that can reduce the degree of splenomegaly for some of these patients. However, splenectomy, splenic irradiation, and partial splenic artery embolization remain valuable therapeutic options in select patients. In this review, we will discuss currently available pharmacologic therapies and describe promising drugs currently in development. We will also delve into the efficacy and safety concerns of splenectomy, splenic irradiation, and partial splenic artery embolization. Finally, we will propose a treatment algorithm to help guide clinicians in the management of symptomatic splenomegaly in patients with MF.

Primary myelofibrosis: 2019 update on diagnosis, risk-stratification and management

DISEASE OVERVIEW

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm (MPN) characterized by stem cell-derived clonal myeloproliferation that is often but not always accompanied by JAK2, CALR, or MPL mutations; additional disease features include bone marrow stromal reaction including reticulin fibrosis, abnormal cytokine expression, anemia, hepatosplenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression, and shortened survival.

DIAGNOSIS

Diagnosis of PMF is based on bone marrow morphology. Presence of JAK2, CALR, or MPL mutation, expected in ∼ 90% of the patients, is supportive but not essential for diagnosis. The revised 2016 World Health Organization (WHO) classification system distinguishes "prefibrotic" from "overtly fibrotic" PMF; the former might mimic ET in its presentation and it is prognostically relevant to distinguish the two.

RISK STRATIFICATION

Two new prognostic systems for PMF have recently been introduced: GIPSS (genetically inspired prognostic scoring system) and MIPSS70+ version 2.0 (mutation- and karyotype-enhanced international prognostic scoring system). GIPSS is based exclusively on mutations and karyotype. MIPSS70+ version 2.0 utilizes both genetic and clinical risk factors. GIPSS features four and MIPSS70+ version 2.0 five risk categories. MIPSS70+ version 2.0 requires an online score calculator (http://www.mipss70score.it) while GIPPS offers a lower complexity prognostic tool.

RISK-ADAPTED THERAPY

Observation alone is advised for MIPSS70+ version 2.0 "low" and "very low" risk disease (estimated 10-year survival 56%-92%); allogeneic stem cell transplant is the preferred treatment of choice for "very high" and "high" risk disease (estimated 10-year survival 0-13%); treatment-requiring patients with intermediate-risk disease (estimated 10-year survival 30%) are best served by participating in clinical trials. All other treatment approaches, including the use of JAK2 inhibitors, are mostly palliative and should not be used in the absence of clear treatment indications. Conventional treatment for anemia includes androgens, prednisone, thalidomide and danazol, for symptomatic splenomegaly hydroxyurea and ruxolitinib and for constitutional symptoms ruxolitinib. Splenectomy is considered for drug-refractory splenomegaly and involved field radiotherapy for nonhepatosplenic EMH and extremity bone pain.

A phase II trial of ruxolitinib in combination with azacytidine in myelodysplastic syndrome/myeloproliferative neoplasms

Ruxolitinib and azacytidine target distinct disease manifestations of myelodysplastic syndrome/myeloproliferative neoplasms (MDS/MPNs). Patients with MDS/MPNs initially received ruxolitinib BID (doses based on platelets count), continuously in 28-day cycles for the first 3 cycles. Azacytidine 25 mg/m² (Day 1-5) intravenously or subcutaneously was recommended to be added to each cycle starting cycle 4 and could be increased to 75 mg/m² (Days 1-5) for disease control. Azacytidine could be started earlier than cycle 4 and/or at higher dose in patients with rapidly proliferative disease or with elevated blasts. Thirty-five patients were treated (MDS/MPN-U, n =14; CMML, n =17; aCML, n =4), with a median follow-up of 15.2 months (range, 1.0-41.5). All patients were evaluable by the 2015 international consortium proposal of response criteria for MDS/MPNs (ICP MDS/MPN) and 20 (57%) responded. Nine patients (45%) responded after the addition of azacytidine. A greater than 50% reduction in palpable splenomegaly at 24 weeks was noted in 9/14 (64%) patients. Responders more frequently were JAK2-mutated (P = .02) and had splenomegaly (P = .03) compared to nonresponders. New onset grade 3/4 anemia and thrombocytopenia occurred in 18 (51%) and 19 (54%) patients, respectively, but required therapy discontinuation in only 1 (3%) patient. Patients with MDS/MPN-U had better median survival compared to CMML and aCML (26.5 vs 15.1 vs 8 months; P = .034). The combination of ruxolitinib and azacytidine was well-tolerated with an ICP MDS/MPN-response rate of 57% in patients with MDS/MPNs. The survival benefit was most prominent in patients with MDS/MPN-U.

Myelofibrosis: an update on drug therapy in 2016

INTRODUCTION

Primary myelofibrosis (PMF) is the least common but the most aggressive of the classic Philadelphia chromosome-negative myeloproliferative neoplasms. Survival is much shorter in PMF than in polycythemia vera (PV) or essential thrombocythemia (ET). Post-PV/ET myelofibrosis (MF) is clinically indistinguishable from PMF and approached similarly. Areas covered: Current pharmacologic therapy of MF revolves around the Janus kinase 1/2 (JAK1/2) inhibitor ruxolitinib, which dramatically improves constitutional symptoms and splenomegaly in the majority of patients, and improves overall survival (OS). However, allogeneic stem cell transplantation remains the only potential cure. Other JAK inhibitors continue to be developed for MF, and momelotinib and pacritinib are in phase III clinical trials. Anemia is common in MF, and initially worsened by ruxolitinib. Momelotinib and pacritinib may prove advantageous in this regard. Current strategies for managing anemia of MF include danazol, immunomodulatory drugs and erythroid stimulating agents, either alone or in combination with ruxolitinib. Expert opinion: A number of other agents, representing diverse drug classes, are in various stages of development for MF. These include newer JAK inhibitors, other signaling inhibitors, epigenetic modifiers, anti-fibrotic agents, telomerase inhibitors, and activin receptor ligand traps (for anemia). Hopefully, these novel therapies will further extend the clinical benefits of ruxolitinib.

Primary myelofibrosis: 2017 update on diagnosis, risk-stratification, and management

Disease overview: Primary myelofibrosis (PMF) is a myeloproliferative neoplasm (MPN) characterized by stem cell-derived clonal myeloproliferation that is often but not always accompanied by JAK2, CALR or MPL mutation, abnormal cytokine expression, bone marrow fibrosis, anemia, splenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression and shortened survival.

DIAGNOSIS

Diagnosis is based on bone marrow morphology. The presence of JAK2, CALR or MPL mutation is supportive but not essential for diagnosis; approximately 90% of patients carry one of these mutations and 10% are "triple-negative." None of these mutations are specific to PMF and are also seen in essential thrombocythemia (ET). According to the revised 2016 World Health Organization (WHO) classification and diagnostic criteria, "prefibrotic" PMF (pre-PMF) is distinguished from "overtly fibrotic" PMF; the former might mimic ET in its presentation and it is prognostically relevant to distinguish the two. Risk stratification: The Dynamic International Prognostic Scoring System-plus (DIPSS-plus) uses eight predictors of inferior survival: age >65 years, hemoglobin <10 g/dL, leukocytes >25 × 10⁹ /L, circulating blasts ≥1%, constitutional symptoms, red cell transfusion dependency, platelet count <100 × 10⁹ /L and unfavorable karyotype (i.e., complex karyotype or sole or two abnormalities that include +8, -7/7q-, i(17q), inv(3), 5/5q-, 12p-, or 11q23 rearrangement). The presence of 0, 1, "2 or 3" and ≥4 adverse factors defines low, intermediate-1, intermediate-2 and high-risk disease with median survivals of approximately 15.4, 6.5, 2.9 and 1.3 years, respectively. Most recently, DIPSS-plus-independent adverse prognostic relevance has been demonstrated for certain mutations including ASXL1 and SRSF2 whereas patients with type 1/like CALR mutations, compared to their counterparts with other driver mutations, displayed significantly better survival. Risk-adapted therapy: Observation alone is a reasonable treatment strategy for asymptomatic low or intermediate-1 DIPSS-plus risk disease, especially in the absence of high-risk mutations. All other patients with high or intermediate-2 risk disease, or those harboring high-risk mutations such as ASXL1 or SRSF2, should be considered for stem cell transplant, which is currently the only treatment modality with the potential to favorably modify the natural history of the disease. Non-transplant candidates should be encouraged to participate in clinical trials, since the value of conventional drug therapy, including the use of JAK2 inhibitors, is limited to symptoms palliation and reduction in spleen size. Specifically, JAK2 inhibitors have not been shown to induce complete clinical or cytogenetic remissions or significantly affect JAK2/CALR/MPL mutant allele burden. Splenectomy is considered for drug-refractory splenomegaly. Involved field radiotherapy is most useful for post-splenectomy hepatomegaly, non-hepatosplenic EMH, PMF-associated pulmonary hypertension and extremity bone pain. Am. J. Hematol. 91:1262-1271, 2016. © 2016 Wiley Periodicals, Inc.

Myeloproliferative Neoplasms: Molecular Drivers and Therapeutics

Activating mutations in genes that drive neoplastic cell growth are numerous and widespread in cancer, and specific genetic alterations are associated with certain types of cancer. For example, classic myeloproliferative neoplasms (MPNs) are hematopoietic stem cell disorders that affect cells of the myeloid lineage, including erythrocytes, platelets, and granulocytes. An activating mutation in the JAK2 tyrosine kinase is prevalent in these diseases. In MPN patients that lack such a mutation, other genetic changes that lead to activation of the JAK2 signaling pathway are present, indicating deregulation of JAK2 signaling plays an etiological driving role in MPNs, a concept supported by significant evidence from in vivo experimental MPN systems. Thus, small molecules that inhibit JAK2 activity are ideal drugs to impede the progression of disease in MPN patients. However, even though JAK inhibitors provide significant symptomatic relief, they have failed as a remission-inducing therapy. Nonetheless, the progress made understanding the molecular etiology of MPNs since 2005 is significant and has provided insight for the development and testing of novel molecular targeted therapeutic approaches. The current understanding of driver mutations in MPNs and an overview of current and potential therapeutic strategies for MPN patients will be discussed.

Therapeutic approaches in myelofibrosis and myelodysplastic/myeloproliferative overlap syndromes

The discovery of JAK2 (V617F) a decade ago led to optimism for a rapidly developing treatment revolution in Ph(-) myeloproliferative neoplasms. Unlike BCR-ABL, however, JAK2 was found to have a more heterogeneous role in carcinogenesis. Therefore, for years, development of new therapies was slow, despite standard treatment options that did not address the overwhelming symptom burden in patients with primary myelofibrosis (MF), post-essential thrombocythemia MF, post-polycythemia vera MF, and myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN) syndromes. JAK-STAT inhibitors have changed this, drastically ameliorating symptoms and ultimately beginning to show evidence of impact on survival. Now, the genetic foundations of myelofibrosis and MDS/MPN are rapidly being elucidated and contributing to targeted therapy development. This has been empowered through updated response criteria for MDS/MPN and refined prognostic scoring systems in these diseases. The aim of this article is to summarize concisely the current and rationally designed investigational therapeutics directed at JAK-STAT, hedgehog, PI3K-Akt, bone marrow fibrosis, telomerase, and rogue epigenetic signaling. The revolution in immunotherapy and novel treatments aimed at previously untargeted signaling pathways provides hope for considerable advancement in therapy options for those with chronic myeloid disease.

Profile of pomalidomide and its potential in the treatment of myelofibrosis

Myelofibrosis, a Philadelphia-negative myeloproliferative neoplasm, is in a new treatment era after the discovery of the JAK2V617F mutation in 2005. JAK inhibitors boast improvements in disease-related symptoms, splenomegaly, and overall survival; however, treatment of myelofibrosis remains a challenge, given the lack of improvement in cytopenias with these agents. Second-generation immunomodulatory agents, such as pomalidomide, have shown efficacy in myelofibrosis-associated anemia within multiple clinical trials. Five major pomalido-mide clinical trials have been completed to date, and demonstrate tolerability and efficacy with low-dose pomalidomide (0.5 mg/day) in the treatment of myelofibrosis, and no clinical benefit of elevated dosing regimens (≥2.5 mg/day). Anemia responses ranged from 17% to 36% as per the International Working Group for Myelofibrosis Research and Treatment consensus guidelines, while improvements in splenomegaly were rare, and observed in <1% of most clinical trials. In comparison with earlier immunomodulatory agents, pomalidomide was associated with an improved toxicity profile, with substantially lower rates of myelosuppression and neuropathy. Given the low overall response rate to pomalidomide as a single agent, combination strategies are of particular interest for future studies. Pomalidomide is currently being tested in combination with ruxolitinib, and other novel combinations are likely on the horizon.

Management of thrombocythemia

Essential thrombocythemia is a clonal myeloproliferative neoplasm characterized by an elevated platelet count, the potential for both microvascular and macrovascular sequelae, and a risk for transformation to myelofibrosis or acute myeloid leukemia. A systematic and detailed initial analysis is essential for accurate diagnosis of essential thrombocythemia, as many etiologies are reactive and benign. Once a diagnosis has been made, risk stratification and symptom assessment are vital to guide the subsequent therapy. Treatment may be required in high-risk disease, such as in cases of advanced age or prior thrombotic events. Systemic therapy is aimed at reducing the thrombotic risk and includes daily low dose aspirin and in some patients, cytoreductive therapy.  Currently, the first line cytoreductive therapy includes hydroxyurea or pegylated interferon, with a phase III clinical trial underway comparing these two important agents. Anagrelide and clinical trials are reserved for refractory or intolerant patients. Looking to the future, new therapies including Janus kinase 2 (JAK2) and telomerase inhibitors are promising and may become valuable to the treatment armamentarium for those afflicted with essential thrombocythemia.

Primary myelofibrosis: 2014 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm characterized by stem cell-derived clonal myeloproliferation, abnormal cytokine expression, bone marrow fibrosis, anemia, splenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression, and shortened survival.

DIAGNOSIS

DIAGNOSIS is based on bone marrow morphology. The presence of JAK2, CALR, or MPL mutation is supportive but not essential for diagnosis; approximately 90% of patients carry one of these mutations and 10% are "triple-negative." None of these mutations are specific to PMF and are also seen in essential thrombocythemia (ET). Prefibrotic PMF mimics ET in its presentation and the distinction, enabled by careful bone marrow morphological examination, is prognostically relevant. Differential diagnosis also includes chronic myeloid leukemia, myelodysplastic syndromes, chronic myelomonocytic leukemia, and acute myeloid leukemia.

RISK STRATIFICATION

The Dynamic International Prognostic Scoring System-plus (DIPSS-plus) uses eight predictors of inferior survival: age >65 years, hemoglobin <10 g/dL, leukocytes >25 × 10(9) /L, circulating blasts ≥1%, constitutional symptoms, red cell transfusion dependency, platelet count <100 × 10(9) /L, and unfavorable karyotype (i.e., complex karyotype or sole or two abnormalities that include +8, -7/7q-, i(17q), inv(3), -5/5q-, 12p-, or 11q23 rearrangement). The presence of 0, 1, "2 or 3," and ≥4 adverse factors defines low, intermediate-1, intermediate-2, and high-risk disease with median survivals of approximately 15.4, 6.5, 2.9, and 1.3 years, respectively. High risk disease is also defined by CALR(-) /ASXL1(+) mutational status.

RISK-ADAPTED THERAPY

Observation alone is adequate for asymptomatic low/intermediate-1 risk disease, especially with CALR(+) /ASXL1(-) mutational status. Stem cell transplant is considered for DIPSS-plus high risk disease or any risk disease with CALR(-) /ASXL1(+) mutational status. Investigational drug therapy is reasonable for symptomatic intermediate-1 or intermediate-2 risk disease. Splenectomy is considered for drug-refractory splenomegaly. Involved field radiotherapy is most useful for post-splenectomy hepatomegaly, non-hepatosplenic EMH, PMF-associated pulmonary hypertension, and extremity bone pain.

Does anything work for anaemia in myelofibrosis?

Anaemia is a common finding at diagnosis in myelofibrosis, and becomes a symptomatic problem in most patients with time. There are several treatment options for specific anaemia treatment, none of which has been tested in large, randomized, controlled trials. However, as myelofibrosis is not a disease with spontaneous remissions, even non-randomized trials carry weight. In this survey, the existing evidence will be analysed, both for the commonly used treatments like erythropoiesis-stimulating agents, androgens and thalidomide and for the new drugs in the area, and conclusions will be drawn concerning standard clinical anaemia treatment in myelofibrosis, which according to evidence from studies has a 40-50% chance of response in patients with not too advanced disease.

Emerging therapies for the treatment of chronic Philadelphia chromosome-negative myeloproliferative neoplasm-associated myelofibrosis

INTRODUCTION

Chronic Philadelphia chromosome-negative myeloproliferative neoplasm-associated myelofibrosis significantly impacts afflicted patients with cytopenia, splenomegaly, debilitating constitutional symptoms and decreased survival. Approval of the first Janus kinase 2 (JAK2) inhibitor therapy, ruxolitinib, has improved splenomegaly, symptomatic burden, survival and perhaps fibrosis in some treated patients; however, other patients remain symptomatic and are in need of alternate therapeutic strategies.

AREAS COVERED

A review of recent literature via PubMed and meeting abstracts has revealed many studies investigating new treatment approaches for chronic Philadelphia chromosome-negative myeloproliferative neoplasms. Multiple additional JAK2 inhibitors (fedratinib, pacritinib and momelotinib) are well into single agent development, as well as multiple combination approaches with ruxolitinib. Efforts to combine JAK2 inhibition with agents to improve cytopenia, marrow fibrosis, additional pathway inhibitors and even allogeneic transplant are planned or ongoing. Additionally, Phase III trials of immunomodulation with pomalidomide are ongoing.

EXPERT OPINION

This article discusses investigational therapies for the treatment of Philadelphia chromosome-negative myeloproliferative neoplasms, particularly those in Phase II clinical trials, employing new JAK2 inhibitors, novel multi-agent therapeutic approaches and innovative new drug targets. Additionally, the future era of Philadelphia chromosome-negative myeloproliferative neoplasms is addressed with potentially expanded niches for JAK2 inhibition.

Reversible bone marrow aplasia induced by pegylated interferon-α-2a therapy in a patient with primary myelofibrosis

Interferon has been widely used in the management of patients with hematological malignancies such as polycythemia vera, myelofibrosis, chronic myeloid leukemia and viral infections such as chronic hepatitis C. Hematological adverse effects such as cytopenias have been observed, particularly in patients who receive a combination of interferon-α-2a and ribavirin for hepatitis C. Mild myelosuppression can be seen with pegylated interferon; however, bone marrow aplasia in patients with myelofibrosis has not been reported. It is important to be aware of such a serious complication since persistent bone marrow aplasia can be fatal. We describe a case of pegylated interferon-induced reversible bone marrow aplasia in a patient with primary myelofibrosis.

Primary myelofibrosis: 2013 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm characterized by stem cell-derived clonal myeloproliferation, abnormal cytokine expression, bone marrow fibrosis, anemia, splenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression, and shortened survival.

DIAGNOSIS

Diagnosis is based on bone marrow morphology. The presence of fibrosis, JAK2/MPL mutation, or +9/13q- cytogenetic abnormality is supportive but not essential for diagnosis. Prefibrotic PMF mimics essential thrombocythemia in its presentation and the distinction is prognostically relevant. Differential diagnosis of myelofibrosis should include chronic myeloid leukemia, myelodysplastic syndromes, chronic myelomonocytic leukemia, and acute myeloid leukemia.

RISK STRATIFICATION

The Dynamic International Prognostic Scoring System-plus (DIPSS-plus) prognostic model for PMF can be applied at any point during the disease course and uses eight independent predictors of inferior survival: age >65 years, hemoglobin <10 g/dL, leukocytes >25 × 10⁹/L, circulating blasts ≥ 1%, constitutional symptoms, red cell transfusion dependency, platelet count <100 × 10⁹/L, and unfavorable karyotype (i.e., complex karyotype or sole or two abnormalities that include +8, -7/7q-, i(17q), inv(3), -5/5q-, 12p-, or 11q23 rearrangement). The presence of 0, 1, "2 or 3," and ≥ 4 adverse factors defines low, intermediate-1, intermediate-2, and high-risk disease with median survivals of approximately 15.4, 6.5, 2.9, and 1.3 years, respectively. A >80% two-year mortality is predicted by monosomal karyotype, inv(3)/i(17q) abnormalities, or any two of circulating blasts >9%, leukocytes ≥ 40 × 10⁹/L or other unfavorable karyotype. Most recently, mutations involving ASXL1, SRSF2, EZH2, and IDH1/2 or increased plasma IL-2R, IL-8, or serum-free light chain levels have been shown to adversely affect survival.

RISK-ADAPTED THERAPY

Observation alone is adequate for asymptomatic low/intermediate-1 risk disease. Allogeneic stem cell transplantation (ASCT) is often considered for high risk disease. Conventional or experimental drug therapy is reasonable for symptomatic intermediate-1 or intermediate-2 risk disease; however, ASCT is an acceptable treatment option for such patients in the presence of ASXL1 or other prognostically adverse mutations. Splenectomy and low-dose radiotherapy are used for drug-refractory splenomegaly. Radiotherapy is also used for the treatment of non-hepatosplenic EMH, PMF-associated pulmonary hypertension, and extremity bone pain.

Is there a role for the use of IFN-α in primary myelofibrosis?

A 62-year-old man with a history of diabetes and hypertension is referred to your hematology clinic for an incidental discovery of anemia. He does not have any constitutional symptoms and previous blood counts have been within the normal range. He has hepatosplenomegaly with a palpable spleen of 6 cm below the left costal margin and a liver size of 2.5 cm below the right costal margin. Laboratory evaluation shows a WBC count of 12.8 K/μL, hemoglobin of 11.0 g/dL, and platelets of 202 K/μL, with a mean corpuscular volume of 85.7, 72% neutrophils, 13% lymphocytes, 4% monocytes, 5% eosinophils, 1% basophils, 1% promyelocytes, 4% myelocytes, and lactate dehydrogenase of 447 U/L (upper limit of normal is < 340 U/L). Peripheral blood smear shows 2+ teardrop-shaped RBCs, large hypogranular platelets, and rare nucleated RBCs. Bone marrow (BM) biopsy exhibits a hypercellular BM with atypical megakaryocytes and increased reticulin fibrosis (MF-1). BCR-ABL gene rearrangement by FISH was negative and JAK2 V617F mutation was 95% positive. He was diagnosed with primary myelofibrosis considered low risk (risk score of 0) by the International Prognostic Scoring System.1 Because he is low risk and asymptomatic, he does not need treatment at this time.2 However, he has read about the possible clinical benefits of IFN-α and its potential reduction of BM fibrosis and wonders whether this would be an appropriate treatment.

Advances in the management of myelofibrosis

BACKGROUND

Myelofibrosis (MF) is a rare and serious hematologic malignancy classified as a Philadelphia chromosome-negative myeloproliferative neoplasm (MPN). The disease is more common in males and in older individuals. Of the MPNs, MF presents with the most severe morbidity and greatest mortality. Although the cause of MF is unknown, it is thought to occur from acquired mutations that target the hematopoietic stem cell.

METHODS

We reviewed the current literature pertaining to the pathophysiology, clinical presentation, diagnosis, risk stratification, and treatment of MF. The strengths and limitations of present treatment options as well as the emerging clinical experience with Janus kinase 2 (JAK2) inhibitors are explored.

RESULTS

Diagnosis is often one of exclusion and is facilitated using the World Health Organization or International Working Group for Myelofibrosis Research and Treatment criteria, depending on whether primary or secondary MF is suspected. Treatment is complicated by a lack of disease familiarity of general practitioners and the advanced age of presenting patients. Although allogeneic stem cell transplant offers a potential cure, most treatments for this condition are limited to symptomatic management, with little to no effect on survival. Appropriate patient assessment and risk stratification are essential for predicting outcomes and allowing treating physicians to tailor therapy accordingly.

CONCLUSIONS

Significant advances have been made in understanding the pathophysiology of MF, leading to novel therapeutic approaches. The discovery of the JAK2 mutation and the development of JAK2 inhibitors provide clinicians with a new effective treatment option. Ruxolitinib is the first JAK1/2 inhibitor approved by the Food and Drug Administration (FDA) for the treatment of patients with intermediate- or high-risk MF. In clinical studies, ruxolitinib produced a significantly greater reduction in spleen size and improved quality of life compared with placebo or best available therapy. Several future therapies, including combination therapies with ruxolitinib, are currently under investigation.

Primary myelofibrosis: 2012 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm characterized by stem cell-derived clonal myeloproliferation, abnormal cytokine expression, bone marrow fibrosis, anemia, splenomegaly, extramedullary hematopoiesis (EMH), constitutional symptoms, cachexia, leukemic progression, and shortened survival.

DIAGNOSIS

Diagnosis is based on bone marrow morphology. The presence of fibrosis, JAK2/MPL mutation or +9/13q- cytogenetic abnormality is supportive but not essential for diagnosis. Prefibrotic PMF mimics essential thrombocythemia in its presentation and the distinction is prognostically relevant. Differential diagnosis of myelofibrosis should include chronic myelogenous leukemia, myelodysplastic syndromes, chronic myelomonocytic leukemia, and acute myeloid leukemia.

RISK STRATIFICATION

The Dynamic International Prognostic Scoring System-plus (DIPSS-plus) prognostic model for PMF can be applied at any point during the disease course and uses eight independent predictors of inferior survival: age >65 years, hemoglobin <10 g/dL, leukocytes >25 × 10(9) /L, circulating blasts ≥1%, constitutional symptoms, red cell transfusion dependency, platelet count <100 × 10(9) /L, and unfavorable karyotype (i.e., complex karyotype or sole or two abnormalities that include +8, -7/7q-, i(17q), inv(3), -5/5q-, 12p- or 11q23 rearrangement). The presence of 0, 1, "2 or 3," and ≥4 adverse factors defines low, intermediate-1, intermediate-2, and high-risk disease with median survivals of ~15.4, 6.5, 2.9, and 1.3 years, respectively. A >80% two-year mortality is predicted by monosomal karyotype, inv(3)/i(17q) abnormalities, or any two of circulating blasts >9%, leukocytes ≥40 × 10(9) /L or other unfavorable karyotype.

RISK-ADAPTED THERAPY

Observation alone is adequate for asymptomatic low/intermediate-1 risk disease. Allogeneic stem cell transplantation or experimental drug therapy is considered for intermediate-2/ high risk disease. Conventional or experimental drug therapy is reasonable for symptomatic intermediate-1 risk disease. Splenectomy and low-dose radiotherapy are used for drug-refractory splenomegaly. Radiotherapy is also used for the treatment of non-hepatosplenic EMH, PMF-associated pulmonary hypertension, and extremity bone pain.

R723, a selective JAK2 inhibitor, effectively treats JAK2V617F-induced murine myeloproliferative neoplasm

The activating mutations in JAK2 (including JAK2V617F) that have been described in patients with myeloproliferative neoplasms (MPNs) are linked directly to MPN pathogenesis. We developed R723, an orally bioavailable small molecule that inhibits JAK2 activity in vitro by 50% at a concentration of 2nM, while having minimal effects on JAK3, TYK2, and JAK1 activity. R723 inhibited cytokine-independent CFU-E growth and constitutive activation of STAT5 in primary hematopoietic cells expressing JAK2V617F. In an anemia mouse model induced by phenylhydrazine, R723 inhibited erythropoiesis. In a leukemia mouse model using Ba/F3 cells expressing JAK2V617F, R723 treatment prolonged survival and decreased tumor burden. In V617F-transgenic mice that closely mimic human primary myelofibrosis, R723 treatment improved survival, hepatosplenomegaly, leukocytosis, and thrombocytosis. R723 preferentially targeted the JAK2-dependent pathway rather than the JAK1- and JAK3-dependent pathways in vivo, and its effects on T and B lymphocytes were mild compared with its effects on myeloid cells. Our preclinical data indicate that R723 has a favorable safety profile and the potential to become an efficacious treatment for patients with JAK2V617F-positive MPNs.

How I treat myelofibrosis

It is currently assumed that myelofibrosis (MF) originates from acquired mutations that target the hematopoietic stem cell and induce dysregulation of kinase signaling, clonal myeloproliferation, and abnormal cytokine expression. These pathogenetic processes are interdependent and also individually contributory to disease phenotype-bone marrow stromal changes, extramedullary hematopoiesis, ineffective erythropoiesis, and constitutional symptoms. Molecular pathogenesis of MF is poorly understood despite a growing list of resident somatic mutations that are either functionally linked to Janus kinase (JAK)-signal transducer and activator of transcription hyperactivation (eg JAK2, MPL, and LNK mutations) or possibly involved in epigenetic dysregulation of transcription (TET2, ASXL1, or EZH2 mutations). Current prognostication in primary MF is based on the Dynamic International Prognostic Scoring System-plus model, which uses 8 independent predictors of inferior survival to classify patients into low, intermediate 1, intermediate 2, and high-risk disease groups; corresponding median survivals are estimated at 15.4, 6.5, 2.9, and 1.3 years. Such information is used to plan a risk-adapted treatment strategy for the individual patient, which might include observation alone, conventional or investigational (eg, JAK inhibitors, pomalidomide) drug therapy, allogenic stem cell transplantation with reduced- or conventional-intensity conditioning, splenectomy, or radiotherapy. I discuss these treatment approaches in the context of who should get what and when.

Identification during the follow-up of time-dependent prognostic factors for the competing risks of death and blast phase in primary myelofibrosis: a study of 172 patients

The median survival of patients with primary myelofibrosis ranges from 3.5 to 5.5 years, and most patients die from cause related to the disease, including blast phase (BP, in 5%-30% of cases). Because identification of high-risk patients might use information collected during the clinical course, we assessed the prognostic value of time-dependent covariates for 2 competing risks (death and BP) in a series of 172 patients. Significant (P < .01) adverse time-dependent prognostic factors for the risk of death were the time to onset of anemia (hemoglobin < 100 g/L [10 g/dL]), leukocytosis (leukocyte count > 30 x 10(9)/L), thrombocytopenia (platelet count < 150 x 10(9)/L), presence of circulating blasts, intermediate-high or high International Working Group for Myelofibrosis Research and Treatment score, and time to splenectomy. The first 3 dependent covariates and the time to chemotherapy initiation (P = .05) were prognostic factors for the risk of BP. The prognostic effect of onset of leukocytosis was significantly more pronounced for BP than for death. Thus, occurrence during the follow-up of characteristics associated with an adverse prognostic value at diagnosis also influenced the risks of death and BP. Patients with leukocytosis should be closely monitored. These data might efficiently help to evaluate the severity of the disease before treatment decision during the clinical course.

How I treat symptomatic splenomegaly in patients with myelofibrosis

Managing patients with myelofibrosis (MF), either those with primary MF or those whose MF has evolved from antecedent polycythemia vera or essential thrombocythemia, presents many challenges to the hematologist. MF patients have a range of debilitating disease manifestations (eg, massive splenomegaly, cytopenias, constitutional symptoms, and transformation to a treatment-refractory blast phase). Cure is potentially achievable through allogeneic stem cell transplantation; however, this therapy is either inappropriate or not feasible for the majority of patients. Therefore, remaining therapies are palliative but can be of significant value to some MF patients. In particular, management of symptomatic splenomegaly remains one of the most perplexing aspects of MF clinical care. Using medications is the simplest approach for reducing splenomegaly, yet achieving symptomatic response without undue myelosuppression is challenging. Splenectomy or radiotherapy offers benefit, but careful patient selection and close monitoring are required because both have the potential for dangerous adverse effects. Experimental medical therapies, such as JAK2 inhibitors, show promise and may soon play an important role in the management of symptomatic splenomegaly in MF patients. Future care of MF patients, including splenomegaly management, will continue to require the hematologist to select therapeutic options carefully in the context of realistic, achievable goals.

Bone marrow toxicity in HCV genotype 5a-infected patient after peg-IFN alpha-2a and ribavirin therapy

The optimal therapy for HCV-related chronic hepatitis is the combination of pegylated interferon alpha (peg-IFN alpha) plus ribavirin (RBV). Unfortunately, both peg-IFN alpha and RBV are responsible for a wide range of adverse events and potentially severe toxicities, particularly hematological alterations. Indeed, RBV is generally responsible for anemia through hemolysis, while peg-IFN alpha induces more commonly leukopoenia and thrombocytopenia, presumably through bone marrow toxicity. Actually, data regarding histopathological bone marrow alterations in HCV-infected patients following IFN-alpha therapy is scanty. We report a case of a HCV-infected cirrhotic patient, who developed bone marrow alterations following one-year peg-IFN alpha plus RBV treatment, and we describe the associated histopathological features. Our case report provides new significant insight on the histopathological changes occurring in bone marrow of HCV-infected cirrhotic patients during peg-IFN alpha-2a plus RBV treatment, providing also additional information on potential bone marrow toxicity in the course of IFN-based treatments.

Interferon-alpha therapy in bcr-abl-negative myeloproliferative neoplasms

Interferon (IFN) was the first cytokine discovered 50 years ago, with a wide range of biological properties, including immunomodulatory, proapoptotic and antiangiogenic activities, that rapidly raised interest in its therapeutic use in malignancies. IFN-receptor characterization was also pivotal in the discovery of the JAK/STAT signaling pathway. Among the large IFN family, mainly one of the type I IFN, IFN-alpha2, is used in therapy. Many clinical trials have shown remarkable efficacy of IFN-alpha in bcr-abl-negative myeloproliferative neoplasms (MPNs), especially polycythemia vera (PV), and essential thrombocythemia (ET). IFN-alpha induces about 80% of hematological responses in those diseases and is able to reduce splenomegaly, as well as relieve pruritus and other constitutional symptoms. Yet its use was limited by toxicity, leading to early treatment discontinuation in about 20% of the patients. However, its lack of leukemogenic potential and its possible use during pregnancy have already made IFN-alpha the drug of choice for younger MPN patients. In addition, several studies have shown a probably selective effect of IFN-alpha on PV and ET clones, as shown by cytogenetic remissions, reversions to polyclonal hematopoiesis, and more recently by induction of JAK2V617F complete molecular remissions in PV which may widen the indications of IFN-alpha in JAK2-mutated MPN.

The prediction of interferon treatment effects based on time series microarray gene expression profiles

BACKGROUND

The status of a disease can be reflected by specific transcriptional profiles resulting from the induction or repression activity of a number of genes. Here, we proposed a time-dependent diagnostic model to predict the treatment effects of interferon and ribavirin to HCV infected patients by using time series microarray gene expression profiles of a published study.

METHODS

In the published study, 33 African-American (AA) and 36 Caucasian American (CA) patients with chronic HCV genotype 1 infection received pegylated interferon and ribavirin therapy for 28 days. HG-U133A GeneChip containing 22283 probes was used to analyze the global gene expression in peripheral blood mononuclear cells (PBMC) of all the patients on day 0 (pretreatment), 1, 2, 7, 14, and 28. According to the decrease of HCV RNA levels on day 28, two categories of responses were defined: good and poor. A voting method based on Student's t test, Wilcoxon test, empirical Bayes test and significance analysis of microarray was used to identify differentially expressed genes. A time-dependent diagnostic model based on C4.5 decision tree was constructed to predict the treatment outcome. This model not only utilized the gene expression profiles before the treatment, but also during the treatment. Leave-one-out cross validation was used to evaluate the performance of the model.

RESULTS

The model could correctly predict all Caucasian American patients' treatment effects at very early time point. The prediction accuracy of African-American patients achieved 85.7%. In addition, thirty potential biomarkers which may play important roles in response to interferon and ribavirin were identified.

CONCLUSION

Our method provides a way of using time series gene expression profiling to predict the treatment effect of pegylated interferon and ribavirin therapy on HCV infected patients. Similar experimental and bioinformatical strategies may be used to improve treatment decisions for other chronic diseases.

Essential thrombocythemia, polycythemia vera, and myelofibrosis: current management and the prospect of targeted therapy

The recent discovery of JAK2 and/or MPL mutations in polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) has had a major impact on how we diagnose and treat these disorders. For instance, the presence of a JAK2 mutation is now considered conditio sine qua non for the diagnosis of PV and the World Health Organization classification system has recently revised its diagnostic criteria for PV, ET, and PMF to include JAK2 and MPL mutations as clonal markers. From the standpoint of treatment, JAK-STAT is now identified as a legitimate target pathway for drug development in myeloproliferative neoplasms. Herein, I will first outline my views regarding current management in ET, PV, and PMF and then discuss emerging data on preclinical and clinical activity of anti-JAK2 small molecule drugs. Am. J. Hematol., 2008. (c) 2008 Wiley-Liss, Inc.

Conventional and experimental drug therapy in myelofibrosis with myeloid metaplasia

Myelofibrosis with myeloid metaplasia (MMM) is currently classified as a classic (ie, BCR-ABL-negative) myeloproliferative disorder characterized by anemia, multiorgan extramedullary hematopoiesis, constitutional symptoms, and premature death from either leukemic transformation or other disease complications. Stem cell transplantation can be curative, but many patients either are not appropriate candidates or do not choose to accept the significant risks associated with transplantation. Current pharmacologic therapy has been beneficial mainly in terms of palliating disease-associated cytopenias, constitutional symptoms, splenomegaly, and other organ damage from excess myeloproliferation. Novel treatment strategies are under investigation, including targeted inhibition of JAK2(V617F), the activating tyrosine kinase point mutation present in about half of patients with MMM. In this article, we review both the old and new pharmacologic options for MMM.

Advances in the therapy of chronic idiopathic myelofibrosis

The molecular basis of chronic idiopathic myelofibrosis (CIMF) has remained elusive, thus hampering the development of effective targeted therapies. However, significant progress regarding the molecular mechanisms involved in the pathogenes is of this disease has been made in recent years that will likely provide ample opportunity for the investigation of novel therapeutic approaches. At the fore front of these advances is the discovery that 35%-55% of patients with CIMF harbor mutations in the Janus kinase 2 tyrosine kinase gene. Until very recently, the management of patients with CIMF involved the use of supportive measures, including growth factors, transfusions, or interferon, and the administration of cyto-reductive agents, such as hydroxyurea and anagrelide. However, several trials have demonstrated the efficacy of antiangiogenic agents alone or in combination with corticosteroids. In addition, the use of reduced-intensity conditioning allogeneic stem cell transplantation has resulted in prolonged survival and lower transplant-related mortality.

Myelofibrosis with myeloid metaplasia: disease overview and non-transplant treatment options

Myelofibrosis with myeloid metaplasia (MMM) is currently classified as a classic (i.e. not yet molecularly defined) myeloproliferative disorder (MPD), along with essential thrombocythemia (ET) and polycythemia vera (PV). All three MPDs represent stem-cell-derived clonal myeloproliferation that, in the case of MMM, is accompanied by an intense bone marrow stromal reaction that includes collagen fibrosis, osteosclerosis, and angiogenesis. To date, both the molecular basis of the primary clonal process and the pathogenetic mechanisms that underlie the secondary histological changes remain elusive. Clinically, MMM is characterized by anemia, multi-organ extramedullary hematopoiesis that often involves the spleen and liver, constitutional symptoms, and premature death from either leukemic transformation or other disease complications. Current diagnosis is based on characteristic but not diagnostic bone marrow histological features. Modern therapy remains palliative but allogeneic stem cell transplantation might be curative to a selected group of patients. This chapter reviews both the old and the new therapy with regard to non-transplant treatment options for MMM.

Pathogenesis of myelofibrosis with myeloid metaplasia

The primary disease process in myelofibrosis with myeloid metaplasia (MMM) is clonal myeloproliferation with varying degrees of phenotypic differentiation. This is characteristically accompanied by secondary intramedullary collagen fibrosis, osteosclerosis, angiogenesis, and extramedullary hematopoiesis. Modern clonality studies have confirmed the multipotent stem-cell origin of the neoplastic process in MMM. The nature of the specific oncogenic mutation(s) is currently being unraveled with the recent discovery of an association between a somatic point mutation of JAK2 tyrosine kinase (V617F) and bcr/abl-negative myeloproliferative disorders, including MMM. The pathogenetic mechanisms that underlie the secondary bone marrow stromal changes in MMM are also incompletely understood. Mouse models of this latter disease aspect have been constructed by either in vivo overexpression of thrombopoietin (TPOhigh mice) or megakaryocyte lineage restricted underexpression of the transcription factor GATA-1 (GATA-1low mice). Gene knockout experiments using such animal models have suggested the essential role of hematopoietic cell-derived transforming growth factor beta1 in inducing bone marrow fibrosis and stromal cell-derived osteoprotegerin in promoting osteosclerosis. However, experimental myelofibrosis in mice does not recapitulate clonal myeloproliferation that is fundamental to human MMM. Other cytokines that are implicated in mediating myelofibrosis and angiogenesis in MMM include basic fibroblast, platelet-derived, and vascular endothelial growth factors. It is currently assumed that such cytokines are abnormally released from clonal megakaryocytes as a result of a pathologic interaction with neutrophils (eg, emperipolesis). This latter phenomenon, through neutrophil-derived elastase, could also underlie the abnormal peripheral-blood egress of myeloid progenitors in MMM.

Myelofibrosis with myeloid metaplasia: new developments in pathogenesis and treatment

Myeloid metaplasia with myelofibrosis (MMM) is a chronic myeloproliferative disorder (CMPD) characterized by progressive anemia, massive splenomegaly, both hepatosplenic and non-hepatosplenic extramedullary hematopoiesis (EMH), a leukoerythroblastic blood smear, circulating progenitor cells, and marked bone marrow stromal reaction including collagen fibrosis, osteosclerosis and angiogenesis. The overall median survival is 5 years although it might range from 2 to 15 years depending on the presence or absence of clinically defined prognostic factors. Death is often due to leukemic transformation, portal hypertension or infection. In addition to shortened survival, quality of life is often affected by frequent red blood cell transfusions, profound constitutional symptoms, and cachexia. Drug therapy and autologous hematopoietic stem cell transplantation (HSCT) are of only palliative value and have not been shown to improve survival. The role of allogeneic HSCT, both myeloablative and non-myeloablative, is actively being investigated. Both splenectomy and radiation therapy have defined therapeutic roles to control EMH-associated symptoms. Analysis of the molecular biology of the disease is underway with the aid of animal models leading to the identification of novel therapeutic targets. Among the novel agents tested, thalidomide seems the most promising although newer agents are on the horizon.

Marrow fibrosis, indicator of therapy failure in chronic myeloid leukemia - prospective long-term results from a randomized-controlled trial

Marrow fibrosis (MF) has rarely been considered in therapy studies on chronic myeloid leukemia (CML), and there is a lack of long-term observations on the basis of sequential bone marrow biopsies (BMBs) taken prospectively during the course of disease. A total of 848 BMBs from 400 patients with Ph(+) CML recruited in the German randomized CML study I were examined for MF before and during therapy. In total, 110 patients had been randomized to receive interferon (IFN)-alpha, and 290 to receive chemotherapy (hydroxyurea (HU): 154, busulfan: 136). During IFN-alpha and HU medication, MF was reduced or did not increase for about 2 years. Evolving or progressive MF was an independent and early predictor of therapy failure about 2 years earlier than indicated by changes in the peripheral blood, spleen size, marrow blast count and cytogenetics (P<0.00005), resulting in a significant shortening of the survival times of patients independent of the type of therapy applied including allografting (multivariate analyses; P<0.00005). The analyzed long-term observations strongly indicate that MF is an independent poor prognostic complication of CML, allowing an early prediction of therapy failure. Consideration of the fiber content in marrow may therefore significantly improve the prediction of therapy efficacy and outcome of disease.

Chronic Myelogenous Leukemia and Myeloproliferative Disease

In Section I, Dr. Stephen O’Brien reviews the latest data on the clinical use of imatinib (STI571, Gleevec, Glivec) in CML. His review focuses on the use of imatinib in newly diagnosed chronic phase patients and summarizes cytogenetic and molecular response data, as well as use of the agent at high doses and in combination with other drugs. A brief summary of the prospective international Phase III studies that are currently ongoing is also provided, and the issues of resistance and definition of suboptimal therapeutic response are also covered. Finally, therapeutic decision-making and treatment strategy are considered.

In Section II, Dr. Ayalew Tefferi considers the latest developments in the biology and therapy of myeloid metaplasia/myelofibrosis. Dr. Tefferi covers what is currently understood of the biology of the disease and reviews established therapies for the condition as well as novel agents that are being used in clinical trials. The development of optimal management strategies for the disease is considered.

In Section III, Dr. Peter Valent reviews the classification of mast cell proliferative disorders and covers the clinical and pathological presentation of this group of neoplasms. He reviews the state-of-the-art regarding the molecular biology of mastocytosis along with diagnostic criteria and novel treatment concepts.

The forgotten myeloproliferative disorder: myeloid metaplasia

Myelofibrosis with myeloid metaplasia is a hematologic disorder currently classified with polycythemia vera and essential thrombocythemia as a chronic myeloproliferative disease. The median age at diagnosis is 60 years, and more than 90% of patients are diagnosed after age 40 years. Clinical manifestations include massive splenomegaly, progressive anemia, profound constitutional symptoms, and extramedullary hematopoiesis. The diagnosis is confirmed by bone marrow examination after other causes of myelofibrosis are ruled out. Median survival is 5 years and causes of death include leukemic transformation. Prognosis is adversely affected by the presence of anemia (hemoglobin <10 g/dl), leukopenia or leukocytosis (white blood cells >30,000/ micro l), circulating blasts, and hypercatabolic symptoms. Conventional treatment is palliative and does not improve survival. In this regard, androgen preparations, corticosteroids, and erythropoietin are useful for the treatment of disease-associated anemia. Symptomatic splenomegaly is best managed by cytoreductive therapy or surgical removal. Radiation therapy is most useful in the treatment of nonhepatosplenic extramedullary hematopoiesis. New treatment approaches include the use of thalidomide alone or in combination with prednisone and hematopoietic stem cell transplantation.

Treatment approaches in myelofibrosis with myeloid metaplasia: the old and the new

Myelofibrosis with myeloid metaplasia (MMM) is currently classified as a chronic myeloproliferative disorder (CMPD) and is characterized by prominent bone marrow stromal reaction including collagen fibrosis, osteosclerosis, and angiogenesis. Among the CMPD, MMM carries the worst prognosis with an overall median survival of 5 years; the clinical course is marred by profound constitutional symptoms, progressive anemia, and symptomatic splenomegaly. Causes of death include leukemic transformation, which occurs in approximately 10% of patients in the first decade of the disease. At present, allogeneic hematopoietic stem cell transplantation (HSCT) is the only treatment modality that has the potential to either cure the disease or prolong survival. Both drug therapy and autologous HSCT are currently palliative. Conventional treatment agents in MMM include androgen preparations, corticosteroids, erythropoietin (EPO), and hydroxyurea. In addition, both splenectomy and radiation therapy have defined therapeutic roles. Thalidomide is the most effective investigational agent at the present time. Optimal therapy for an individual patient requires a sound understanding of disease risk factors, as well as a full appreciation of the risk to benefit ratio for a specific treatment modality.

[Interferons and hematology]

BACKGROUND

IFN alpha are cytokines used for a number of years in the treatment of certain hemopathies, i.e. of a myeloid and lymphoid etiology. IFN alpha are a family of polypeptides produced by eukaryote cells in response to various stimulant agents. The first trials using this cytokine in humans were carried out by H. Strander in the years 1965-1970. IFN alpha contain anti-viral, anti-proliferative and immunomodulatory properties. The access of clinicians to IFN alpha molecules, in addition to elements produced by genetic engineering for approximately the past 20 years, has permitted a number of therapeutic trials to be carried out. In hematology the clinical interest of IFN alpha was primarily in chronic myeloid and lymphoid proliferating syndromes. Certain indications have to date been well demonstrated. However, the impact of IFN alpha on therapeutic care of certain hemopathies as compared to conventional treatment remains controversial. At the same time, the frequency of side effects from treatment with IFN alpha and its cost should be taken into consideration.

CURRENT POSITION AND MAJOR POINTS

The therapeutic trials carried out over the past ten years have proven the interest of IFN alpha in, essentially, two diseases: on one hand chronic myeloid leukemia with the acquisition of cytogenetic remission and on the other malignant non-Hodgkin's follicular type lymphoma. However, as regards other hemopathies the place of IFN alpha remains debatable.

PERSPECTIVES

The future of IFN alpha use in the treatment of hemopathies appears to be linked to its association with new treatments, an association, however, where its efficacy and superiority should be demonstrated. This is the case in chronic myeloid leukemia where IFN alpha could be associated with aracytine or the inhibitors of tyrosine kinase. Also, in the treatment of malignant non-Hodgkin's lymphomas as well as the studies concerning the association between IFN alpha and monoclonal antibodies, in particular antibody anti-CD 20.

The therapy of myelofibrosis: targeting pathogenesis

Myelofibrosis with myeloid metaplasia (MMM) encompasses the diagnoses of agnogenic myeloid metaplasia (idiopathic myelofibrosis), as well as the advanced phases of polycythemia vera and essential thrombocythemia (post polycythemic and post thrombocythemia myeloid metaplasia, respectively). MMM is a clonal, hematopoietic stem cell disorder in which neither the pathogenesis, nor a broadly applicable effective therapy have been described. Clinically, these patients experience progressive marrow replacement by fibrotic tissue, ineffective hematopoiesis, problematic cytopenia's, significant hepato-splenomegaly, extramedullary hematopoiesis, profound constitutional symptoms, and a risk of blastic transformation. Historically, therapies have been targeted at palliating symptoms (i.e. splenectomy, transfusions, hydroxyurea, erythropoietin, androgens, localized radiotherapy). Stem cell transplantation appears promising, but is often toxic and not broadly applicable due to co-morbidities and age of MMM patients. Non-myeloablative approaches to conditioning may broaden the applicability of stem cell transplantation in MMM, yet results to date are preliminary. Although a definitive molecular abnormality responsible for the pathogenesis of MMM has not been described, much has been learned about the aberrant expression of pro-fibrotic cytokines and the presence of increased angiogenesis in MMM. These pathogenetic insights have led to a series of pilot clinical trials with therapeutic agents targeting aberrantly expressed cytokines (and possibly angiogenesis) including Thalidomide (alone or in combination), Etanercept, and STI-571. Amongst these later agents Thalidomide has demonstrated the most promise (palliating disease associated cytopenia's), whereas the TNF-alpha inhibitor Etanercept has aided with MMM associated constitutional symptoms. Although these later trials have been helpful in a subset of patients, no agent to date has led to solid complete responses in MMM across the spectrum of disease manifestations. Further insights into the pathogenetic mechanisms responsible for myeloproliferation (aberrant cell signaling pathways, apoptotic resistance, other) are necessary to guide selection and testing of the expanding number of novel anti-neoplastic agents in chronic myeloid disorders and MMM.

Clinical and scientific advances in the Philadelphia-chromosome negative chronic myeloproliferative disorders

The chronic myeloproliferative disorders are clonal hematopoietic stem cell disorders and include chronic myeloid leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), and agnogenic myeloid metaplasia (AMM). These diseases are characterized by clonal expansion of the myeloid compartment, increased marrow angiogenesis, and varying risks for blastic transformation. A clear molecular abnormality exists (t(9;22) leading to the fusion of BCR-Abl) only for CML, which led to effective targeted therapy (STI-571). Since no similar pathogenetic mechanism has been discovered for the t(9;22) negative chronic myeloproliferative disorders, their respective diagnosis is currently based on a variety of rather cumbersome diagnostic criteria. Polycythemia vera is distinguished from reactive erythrocytosis through erythropoietin independent growth of erythroid progenitors in vitro, suppressed levels of endogenous erythropoietin, possible overexpression of PRV-1 (polycythemia rubra vera-1), decreased c-Mpl expression on megakaryocytes, as well as overexpression of bcl-xL, and potentially aberrant activity of the Jak-Stat pathway. ET is defined by thrombocytosis and is distinguished from reactive states by decreased megakaryocyte c-Mpl expression, and a propensity for thrombosis. AMM has been associated with a variety of observations including increased concentrations of pro-fibrotic cytokines, increased angiogenesis, and myeloid expansion. AMM is often indistinguishable clinically and prognostically from the advanced phases of other CMPD (specifically post-polycythemic and post-thrombocythemia myeloid metaplasia), all of which are subentities of a diagnosis of myelofibrosis with myeloid metaplasia (MMM). The management of CMPD patients is quite varied given the broad range of disease severity and survival observed. The role of stem cell transplantation is limited by the age and comorbidities encountered in CMPD patients. Since no broadly applicable therapy effects the mortality of the CMPD, management currently focuses on the prevention/palliation of disease morbidity (i.e. vascular complications, pruritus, organomegaly, constitutional symptoms). Palliative strategies which currently focus on non-specific myelosuppresion, will hopefully be soon replaced by targeted therapies as insight into pathogenetic mechanisms of these diseases evolves.