Hematopoietic Growth Factors in Myelodysplastic Syndromes

Advanced protein drugs and formulations

For a long time, proteins were a subset of molecules rarely applied as therapeutically active molecules. Some of the first applications of proteins as drugs have been insulin and vaccines for supply a physiological deficiency and the prevention of diseases, respectively. Nowadays, proteins have increased their range of application, not only as drugs but also as drug delivery systems to be administered by different routes. Due to their nature, proteins show different behavior while the conditions of the environment are modified. For this reason, it has been necessary to study their behavior for predicting the correct manufacturing, storing, or combination with other possible molecules in a formulation or into the body. The application of techniques for predicting the behavior of proteins in different environments has led to associate this type of behavior into the body with the occurrence of diseases such as celiac disease or Alzheimer's disease. Thus, this work shows an overview of the main types of proteins applied as active therapeutically molecules, proteins-based drug delivery systems, and techniques for predicting their stability into the storing container and the body.

Current challenges and unmet medical needs in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) represent a heterogeneous group of myeloid neoplasms that are characterized by ineffective hematopoiesis, variable cytopenias, and a risk of progression to acute myeloid leukemia. Most patients with MDS are affected by anemia and anemia-related symptoms, which negatively impact their quality of life. While many patients with MDS have lower-risk disease and are managed by existing treatments, there currently is no clear standard of care for many patients. For patients with higher-risk disease, the treatment priority is changing the natural history of the disease by delaying disease progression to acute myeloid leukemia and improving overall survival. However, existing treatments for MDS are generally not curative and many patients experience relapse or resistance to first-line treatment. Thus, there remains an unmet need for new, more effective but tolerable strategies to manage MDS. Recent advances in molecular diagnostics have improved our understanding of the pathogenesis of MDS, and it is becoming clear that the diverse nature of genetic abnormalities that drive MDS demands a complex and personalized treatment approach. This review will discuss some of the challenges related to the current MDS treatment landscape, as well as new approaches currently in development.

Unravelling the Epigenome of Myelodysplastic Syndrome: Diagnosis, Prognosis, and Response to Therapy

Simple Summary

Myelodysplastic syndrome (MDS) is a type of blood cancer that mostly affects older individuals. Invasive tests to obtain bone samples are used to diagnose MDS and many patients do not respond to therapy or stop responding to therapy in the short-term. Less invasive tests to help diagnose, prognosticate, and predict response of patients is a felt need. Factors that influence gene expression without changing the DNA sequence (epigenetic modifiers) such as DNA methylation, micro-RNAs and long-coding RNAs play an important role in MDS, are potential biomarkers and may also serve as targets for therapy.

Abstract

Myelodysplastic syndrome (MDS) is a malignancy that disrupts normal blood cell production and commonly affects our ageing population. MDS patients are diagnosed using an invasive bone marrow biopsy and high-risk MDS patients are treated with hypomethylating agents (HMAs) such as decitabine and azacytidine. However, these therapies are only effective in 50% of patients, and many develop resistance to therapy, often resulting in bone marrow failure or leukemic transformation. Therefore, there is a strong need for less invasive, diagnostic tests for MDS, novel markers that can predict response to therapy and/or patient prognosis to aid treatment stratification, as well as new and effective therapeutics to enhance patient quality of life and survival. Epigenetic modifiers such as DNA methylation, long non-coding RNAs (lncRNAs) and micro-RNAs (miRNAs) are perturbed in MDS blasts and the bone marrow micro-environment, influencing disease progression and response to therapy. This review focusses on the potential utility of epigenetic modifiers in aiding diagnosis, prognosis, and predicting treatment response in MDS, and touches on the need for extensive and collaborative research using single-cell technologies and multi-omics to test the clinical utility of epigenetic markers for MDS patients in the future.

Erythropoietin regulation of red blood cell production: from bench to bedside and back

More than 50 years of efforts to identify the major cytokine responsible for red blood cell (RBC) production (erythropoiesis) led to the identification of erythropoietin (EPO) in 1977 and its receptor (EPOR) in 1989, followed by three decades of rich scientific discovery. We now know that an elaborate oxygen-sensing mechanism regulates the production of EPO, which in turn promotes the maturation and survival of erythroid progenitors. Engagement of the EPOR by EPO activates three interconnected signaling pathways that drive RBC production via diverse downstream effectors and simultaneously trigger negative feedback loops to suppress signaling activity. Together, the finely tuned mechanisms that drive endogenous EPO production and facilitate its downstream activities have evolved to maintain RBC levels in a narrow physiological range and to respond rapidly to erythropoietic stresses such as hypoxia or blood loss. Examination of these pathways has elucidated the genetics of numerous inherited and acquired disorders associated with deficient or excessive RBC production and generated valuable drugs to treat anemia, including recombinant human EPO and more recently the prolyl hydroxylase inhibitors, which act partly by stimulating endogenous EPO synthesis. Ongoing structure-function studies of the EPOR and its essential partner, tyrosine kinase JAK2, suggest that it may be possible to generate new "designer" drugs that control selected subsets of cytokine receptor activities for therapeutic manipulation of hematopoiesis and treatment of blood cancers.

Current and Future Treatment Options for Myelodysplastic Syndromes: More Than Hypomethylating Agents and Lenalidomide?

Myelodysplastic syndromes are a heterogeneous group of bone marrow disorders that result in cytopenias and a propensity to develop secondary leukemia. While allogeneic transplantation still remains the only potential curative treatment option, it can only be offered to a limited number of patients. For the majority, who are not transplant candidates, treatment strategies cover iron chelation, growth factors, lenalidomide, and hypomethylating agents to improve cytopenia and potentially delay disease progression. These limited options underpin the urgent need for more translational research-based clinical trials in well-defined subgroups of patients with myelodysplastic syndromes. Indeed, myelodysplastic syndromes are a moving target with maximum innovation in the understanding of the complex molecular pathways during the last decade. Compared with other hematological diseases such as myeloma, this has unfortunately not yet translated into approval of novel treatment options. Given the current developments in the field, we are optimistic that recent frustrations will be overcome shortly and this will pave the way for exciting opportunities, especially for patients not responding to first-line therapeutic options.

Myelodysplastic syndromes current treatment algorithm 2018

Myelodysplastic syndromes (MDS) include a group of clonal myeloid neoplasms characterized by cytopenias due to ineffective hematopoiesis, abnormal blood and marrow cell morphology, and a risk of clonal evolution and progression to acute myeloid leukemia (AML). Because outcomes for patients with MDS are heterogeneous, individual risk stratification using tools such as the revised International Prognostic Scoring System (IPSS-R) is important in managing patients-including selecting candidates for allogeneic hematopoietic stem cell transplantation (ASCT), the only potentially curative therapy for MDS. The IPSS-R can be supplemented by molecular genetic testing, since certain gene mutations such as TP53 influence risk independent of established clinicopathological variables. For lower risk patients with symptomatic anemia, treatment with erythropoiesis-stimulating agents (ESAs) or lenalidomide (especially for those with deletion of chromosome 5q) can ameliorate symptoms. Some lower risk patients may be candidates for immunosuppressive therapy, thrombopoiesis-stimulating agents, or a DNA hypomethylating agent (HMA; azacitidine or decitabine). Among higher risk patients, transplant candidates should undergo ASCT as soon as possible, with HMAs useful as a bridge to transplant. Non-transplant candidates should initiate HMA therapy and continue if tolerated until disease progression. Supportive care with transfusions and antimicrobial drugs as needed remains important in all groups.

Application of the FDA Biosimilar Extrapolation Framework to Make Off-Label Determinations

BACKGROUND

The FDA's extrapolation framework allows for a biosimilar to obtain licensure for indications that were not explicitly studied in the context of a clinical trial by extending conclusions from studies in 1 population to make inferences in other populations. Within routine clinical care, drugs and biologics are routinely used for medically accepted off-label indications. The appropriateness of these products for off-label indications are typically curated by compendia and guidelines, which have established processes and criteria for reviewing and evaluating the evidence to make such determinations. The evidence paradigm for biosimilars is different from originator biologics and is one of comparability to a reference product, not to reestablish clinical benefit. Thus, this paradigm shift can be applied to the exercise of making off-label determinations for biosimilars, and the FDA's framework of extrapolation can be used by clinicians and coverage policy decision makers to determine appropriate off-label indications for biosimilars.

OBJECTIVE

To highlight how the FDA's biosimilar extrapolation framework can be used to make off-label policy decisions, using to 2 approved biosimilars for filgrastim and infliximab as case studies.

METHODS

This study describes the FDA extrapolation framework for evaluating whether there are any differences in the mechanism of action, pharmacokinetics/biosdistribution, immunogenicity, and toxicity between on-label and off-label indications. Two case studies are presented that evaluate the biosimilars filgrastim-sndz and infliximab-dyyb for the offlabel indications of treating symptomatic anemia in patients with myelodysplastic syndromes and immune-mediated colitis, respectively. The analytical, nonclinical, and clinical pharmacology, along with clinical studies demonstrating that filgrastim-sndz and infliximab-dyyb are biosimilar to their respective reference products, are reviewed and discussed in context with the extrapolation framework to ascertain whether use of the biosimilar within the off-label indications is scientifically justified.

RESULTS

The mechanism of action of filgrastim and infliximab between their FDA-approved and off-label indications are the same. In addition, there is a high degree of similarity with the analytical and nonclinical characteristics of filgrastim-sndz and infliximab-dyyb and their respective reference products. There is no expectation of differences in safety and immunogenicity across the patient populations. Thus, some decision makers may determine that filgrastim-sndz and infliximab-dyyb be used for the off-label indications of treating symptomatic anemia in patients with myelodysplasia and immune-mediated colitis, respectively.

CONCLUSIONS

In some cases, the use of biosimilars for off-label indications can be scientifically justified. Since coverage policy decisions are intimately tied to compendia and guideline listings, it is incumbent upon these groups to conduct formal assessments of biosimilar off-label indications using the FDA extrapolation framework.

DISCLOSURES

No outside funding supported this study. Li discloses that he has received honoraria and/or paid travel expenses as an advisory board and speaker's bureau participant for Pfizer; for speaking on behalf of Mylan and Apobiologix; and for participating on advisory boards for Eli Lilly and Mylan. Lobaina has nothing to disclose. Li was responsible for study design and manuscript revision. Li took the lead in data collection and interpretation and manuscript preparation, along with Lobaina.

Hematopoietic growth factors in lung cancer

PURPOSE OF REVIEW

Most patients affected by lung cancer are treated with chemotherapy, and hence are at risk of myelosuppression. Hematopoietic growth factors have a relevant role in this setting, as they can improve quality of life, reduce the rate of chemotherapy-induced complications and allow the administration of full-dose chemotherapy.

RECENT FINDINGS

Most data of hematologic growth factors in lung cancer come from dated publications or large trials involving different malignancies, thus limiting specific information for lung neoplasms. Nonetheless, most studies consistently identified myeloid growth factors as effective on specific end-points such as the duration and severity of neutropenia, or complications such as hospitalizations and febrile neutropenia; on the other hand, erythropoiesis-stimulating agents (ESAs) consistently improved anemia-specific end-points including hemoglobin values, transfusions rate and fatigue, although some specific safety issues characterized this drug class. The most recent international guidelines address these characteristics and include the main indications for hematologic growth factors in solid neoplasms, including lung cancer.

SUMMARY

Myeloid growth factors and ESAs have a relevant role in selected patients undergoing chemotherapy for nonsmall cell lung cancer and small cell lung cancer. Notably, a comprehensive risk-benefit assessment is required in the specific case of ESAs.

Brief report: serpin Spi2A as a novel modulator of hematopoietic progenitor cell formation

Prime regulation over hematopoietic progenitor cell (HPC) production is exerted by hematopoietins (HPs) and their Janus kinase-coupled receptors (HP-Rs). For HP/HP-R studies, one central challenge in determining specific effects involves the delineation of nonredundant signal transduction factors and their lineage restricted actions. Via loss-of-function studies, we define roles for an HP-regulated Serpina3g/Spi2A intracellular serpin during granulomyelocytic, B-cell, and hematopoietic stem cell (HSC) formation. In granulomyelocytic progenitors, granulocyte macrophage colony stimulating factor (GMCSF) strongly induced Serpina3g expression with Stat5 dependency. Spi2A-knockout (KO) led to 20-fold decreased CFU-GM formation, limited GMCSF-dependent granulocyte formation, and compromised neutrophil survival upon tumor necrosis factor alpha (TNF-α) exposure. In B-cell progenitors, Serpina3g was an interleukin-7 (IL7) target. Spi2A-KO elevated CFU-preB greater than sixfold and altered B-cell formation in competitive bone marrow transplant (BMT), and CpG challenge experiments. In HSCs, Serpina3g/Spi2A expression was also elevated. Spi2A-KO compromised LT-HSC proliferation (as well as lineage(neg) Sca1(pos) Kit(pos) (LSK) cell lysosomal integrity), and skewed LSK recovery post 5-FU. Spi2A therefore functions to modulate HP-regulated immune cell and HSC formation post-5-FU challenge.

Myelodysplastic Syndromes: Diagnosis and Treatment

In the past few years, new biological insights into the myelodysplastic syndromes (MDS) resulting from molecular genetic analysis have improved pathologic understanding, but treatment advances have not kept pace. More than 40 genes are now known to be recurrently mutated in MDS. However, because most of these genes encode spliceosome components, chromatic remodeling factors, epigenetic pattern modulators, or transcription factors rather than more easily inhibited activated tyrosine kinases, there are as of yet few narrowly targeted therapies available for MDS. Three drugs--azacitidine, decitabine, and lenalidomide--were approved by the US Food and Drug Administration for MDS indications a decade ago, and these agents can improve hematopoiesis, delay disease progression, and improve survival and quality of life for a subset of patients. However, only a few patients with MDS respond to these agents, and their benefit is temporary. The only potentially curative therapy for MDS is allogeneic hematopoietic stem cell transplant, but owing to the advanced age of many patients with MDS and the frequency of serious comorbid conditions, less than 10% of patients currently undergo stem cell transplant. This narrative review summarizes the current understanding of MDS and treatment options for these challenging disorders.

Variations in erythropoiesis-stimulating agent administration in transfusion-dependent myelodysplastic syndromes impact response

INTRODUCTION

Erythropoiesis-stimulating agents (ESAs) reduce red blood cell (RBC) transfusions in approximately 40% of patients with myelodysplastic syndrome (MDS) in clinical trials. We studied the association of timing of ESA initiation, agent (epoetin alfa, darbepoetin) and number of weeks of ESA use with response in MDS patients in routine practice.

METHODS

Patients diagnosed with MDS from 2001 to 2005 were identified in the Surveillance Epidemiology and End Results-Medicare linked database. The study cohort consisted of patients with new-onset transfusion dependence (TD). All patients received an ESA at least once during the study period, which began the week that criteria for TD were met and continued until transfusion independence (TI). Kaplan-Meier statistics and Cox Proportional Hazard models were used to assess relationships between time to ESA initiation, agent and number of weeks of ESA use and TI attainment.

RESULTS

Of 610 TD patients treated with ESAs, 210 (34.4%) achieved TI. Median time from ESA initiation to TI was 13 weeks. Shorter time from TD to ESA initiation and use of darbepoetin were associated with higher probability of achieving TI. The probability of achieving TI decreased beyond 8 weeks of treatment, and was very low beyond 16 weeks (8-15 weeks: HR=0.64, 16-31 weeks: HR=0.25, 32+ weeks HR=0.10).

CONCLUSIONS

In this observational, population-based study, variations in ESA administration impacted response in transfusion-dependent MDS patients, with higher response rates with early administration and use of darbepoetin, and low response likelihood in non-responders beyond 16 weeks of therapy.

Recent developments in myelodysplastic syndromes

Once thought to be rare disorders, the myelodysplastic syndromes (MDS) are now recognized as among the most common hematological neoplasms, probably affecting >30 000 patients per year in the United States. US regulatory approval of azacitidine, decitabine, and lenalidomide between 2004 and 2006 seemed to herald a new era in the development of disease-modifying therapies for MDS, but there have been no further drug approvals for MDS indications in the United States in the last 8 years. The available drugs are not curative, and few of the compounds that are currently in development are likely to be approved in the near future. As a result, MDS diagnoses continue to place a heavy burden on both patients and health care systems. Incomplete understanding of disease pathology, the inherent biological complexity of MDS, and the presence of comorbid conditions and poor performance status in the typical older patient with MDS have been major impediments to development of effective novel therapies. Here we discuss new insights from genomic discoveries that are illuminating MDS pathogenesis, increasing diagnostic accuracy, and refining prognostic assessment, and which will one day contribute to more effective treatments and improved patient outcomes.

Maitake mushroom extract in myelodysplastic syndromes (MDS): a phase II study

Background

Myelodysplastic syndromes (MDS) are characterized by ineffective erythropoiesis with dysplastic bone marrow leading to peripheral cytopenia, risk of infection, and progression to acute myelogenous leukemia. Maitake mushroom beta-glucan, a dietary supplement, stimulates hematopoietic progenitor cell differentiation, granulocyte colony-stimulating factor production, and recovery of peripheral blood leukocytes after bone marrow injury. This phase II trial examined the effects of Maitake on innate immune function in MDS.

Methods

Myelodysplastic syndromes patients with International Prognostic Scoring System Low- and Intermediate-1-risk disease received oral Maitake extract at 3 mg/kg twice daily for 12 weeks. Primary endpoints included neutrophil count and function tested as endogenous or stimulated neutrophil production of reactive oxygen species (ROS) by flow cytometry compared with age-matched healthy controls (HC). ROS activators were Escherichiacoli, phorbol ester, and the bacterial peptide N-formylmethionyl-leucyl-phenylalanine (fMLP). Complete blood counts, chemistry panels, iron studies, and monocyte function were evaluated.

Results

Of 21 patients enrolled, 18 completed the study and were evaluable. Maitake increased endogenous (basal) neutrophil (p = 0.005) and monocyte function (p = 0.021). Pre-treatment monocyte response to E. coli was reduced in MDS patients compared with HC (p = 0.002) and increased (p = 0.0004) after treatment. fMLP-stimulated ROS production response also increased (p = 0.03). Asymptomatic eosinophilia occurred in 4 patients (p = 0.014). Other changes in albumin, hemoglobin, and total protein were not clinically relevant.

Conclusions

Maitake was well tolerated. Enhanced in vitro neutrophil and monocyte function following treatment demonstrate that Maitake has beneficial immunomodulatory potential in MDS. Further study is warranted.

Modulators of erythropoiesis: emerging therapies for hemoglobinopathies and disorders of red cell production

Use of new compound such as inhibitors of JAK2 or transforming growth factor β-like molecules might soon revolutionize the treatment of β-thalassemia and related disorders. However, this situation requires careful optimization, noting the potential for off-target immune suppression for JAK2 inhibitors and the lack of mechanistic insights for the use of the ligand trap soluble molecules that sequester ligands of activin receptor IIA and B.

Multiple-dose, safety, pharmacokinetic, and pharmacodynamic study of sotatercept (ActRIIA-IgG1), a novel erythropoietic agent, in healthy postmenopausal women

Ligands of the transforming growth factor-beta superfamily and activin-receptor signaling play an important role in erythropoiesis. Sotatercept, an activin receptor type IIA (ActRIIA) ligand trap, is a novel, recombinant, fusion protein comprising the extracellular domain of human ActRIIA linked to the Fc portion of human immunoglobulin G1. Sotatercept, originally developed to increase bone mineral density, was noted to have robust effects on erythropoiesis. Here, we evaluated the safety, pharmacokinetic properties, and pharmacodynamic effects of sotatercept in 31 healthy postmenopausal women. Sotatercept was administered at dose level 0.1, 0.3, or 1 mg/kg every 28 days subcutaneously for up to four doses. Sotatercept was generally safe and well tolerated, and elicited clinically significant, dose-dependent increases in hemoglobin, hematocrit, and red blood cell counts that persisted for up to 4 months. The effect of sotatercept on hemoglobin was dose-limiting. Sotatercept also increased bone mineral density and biomarkers of bone formation. The sotatercept serum exposure-dose relationship was linear, with a mean terminal half-life of approximately 23 days. ActRIIA ligands are important regulators of erythrocyte production in healthy individuals. Clinical studies are ongoing to explore the potential of sotatercept to treat anemia and diseases of ineffective erythropoiesis as well as an agent to increase bone mineral density.

Myelodysplastic syndromes: what do hospitalists need to know?

Myelodysplastic syndromes (MDS) comprise a heterogeneous group of clonal hematopoietic stem cell disorders characterized by dysplasia, ineffective hematopoiesis leading to peripheral blood cytopenias, and a variable risk of leukemic progression. MDS primarily affects the elderly, and although its prevalence is increasing, MDS is frequently overlooked and underdiagnosed. MDS should be suspected in any patient with unexplained cytopenias, and a bone marrow evaluation is ultimately needed to make the diagnosis and exclude other causes of bone marrow failure. The last 15 years have witnessed significant advances in our understanding of the complex pathogenesis, classification and prognostication, and therapeutic approaches to MDS. Several prognostic models facilitate outcome prediction and risk-adapted therapy. The addition of azacitidine, decitabine, and lenalidomide to erythropoiesis-stimulating agents in our armamentarium offered new effective therapeutic options for many patients who are not candidates for intensive interventions. Improved understanding of the genetic, epigenetic, and immunologic mechanisms that operate in MDS will help develop better prognostication tools and rationally design more effective therapies. Hospitalists are likely to encounter both patients with MDS and patients in whom MDS should be suspected. In this review of MDS, we focus on the epidemiology, diagnosis, pathogenesis, classification and prognostic tools, and treatment options.

Predicting infections in high-risk patients with myelodysplastic syndrome/acute myeloid leukemia treated with azacitidine: a retrospective multicenter study

Hypomethylating agents have become the standard therapy for patients with high-risk myelodysplastic syndrome (MDS). In Israel, azacitidine (AZA) is routinely used. Yet, infectious complications are common during AZA therapy. The current study was aimed to evaluate the incidence and predisposing risk factors for infections in AZA-treated patients. This retrospective study included patients treated with AZA in 18 Israeli medical institutions between 2008 and 2011. Data on 184 patients [157 high-risk MDS and 27 acute myeloid leukemia (AML)], with a median age of 71.6 (range 29-92) were recorded. Overall, 153 infectious events were reported during 928 treatment cycles (16.5%) administered to 100 patients. One hundred fourteen, 114/153 (75%) events required hospitalization and 30 (19.6%) were fatal. In a univariate analysis, unfavorable cytogenetics, low neutrophil, hemoglobin (Hb) and platelet (PLT) counts were found to be associated with infections (24.4% vs. 12.9%, P < 0.0001; 27% vs. 13.5%, P < 0.0001; 20.4% vs. 11%, P < 0.0001 and 29.2% vs. 14.2%, P < 0.0001, respectively). In multivariate analysis, only low Hb level, low PLT count, and unfavorable cytogenetics remained significant. Prior to therapy, poor cytogenetics, PLT count below 20 × 10⁹/L and neutrophil count below 0.5 × 10⁹/L were predictive of the risk of infection during the first two cycles of therapy. In conclusion, patients with unfavorable cytogenetics, presenting with low neutrophil and PLT counts, are susceptible to infections. Evaluation of infection risk should be repeated prior to each cycle. Patients with poor cytogenetics in whom AZA is prescribed despite low PLT count are particularly at high risk for infections and infection prophylaxis may be considered.

Activin receptor antagonists for cancer-related anemia and bone disease

INTRODUCTION

Antagonists of activin receptor signaling may be beneficial for cancer-related anemia and bone disease caused by malignancies such as multiple myeloma and solid tumors.

AREAS COVERED

We review evidence of dysregulated signaling by activin receptor pathways in anemia, myeloma-associated osteolysis, and metastatic bone disease, as well as potential involvement in carcinogenesis. We then review properties of activin receptor antagonists in clinical development.

EXPERT OPINION

Sotatercept is a novel receptor fusion protein that functions as a soluble trap to sequester ligands of activin receptor type IIA (ActRIIA). Preclinically, the murine version of sotatercept increased red blood cells (RBC) in a model of chemotherapy-induced anemia, inhibited tumor growth and metastasis, and exerted anabolic effects on bone in diverse models of multiple myeloma. Clinically, sotatercept increases RBC markedly in healthy volunteers and patients with multiple myeloma. With a rapid onset of action differing from erythropoietin, sotatercept is in clinical development as a potential first-in-class therapeutic for cancer-related anemia, including those characterized by ineffective erythropoiesis as in myelodysplastic syndromes. Anabolic bone activity in early clinical studies and potential antitumor effects make sotatercept a promising therapeutic candidate for multiple myeloma and malignant bone diseases. Antitumor activity has been observed preclinically with small-molecule inhibitors of transforming growth factor-β receptor type I (ALK5) that also antagonize the closely related activin receptors ALK4 and ALK7. LY-2157299, the first such inhibitor to enter clinical studies, has shown an acceptable safety profile so far in patients with advanced cancer. Together, these data identify activin receptor antagonists as attractive therapeutic candidates for multiple diseases.

Infections in myelodysplastic syndromes

Myelodysplastic syndromes are associated with a risk of severe infections. While neutropenia is likely to be the main predisposing factor, several other immune defects have been reported, including impaired neutrophil function, B-, T- and NK-cell defects and the possible consequences of iron overload due to red blood cell transfusions. The advanced age of most patients, their frequent comorbidities, and the fact that drugs such as hypomethylating agents and lenalidomide, which are effective in myelodysplastic syndromes but can transiently worsen neutropenia, may increase the risk of infection and their severity in this context. The majority of infections in myelodysplastic syndromes are bacterial, while the incidence of fungal infections is not well known and viral infections seem to be rare. No prophylactic measures against infections have demonstrated efficacy in myelodysplastic syndromes. However, pending more data, we propose here some recommendations for the management of patients with myelodysplastic syndromes. In the future, an important contribution can be made by prospective trials testing the efficacy of prophylactic and therapeutic approaches to infection in these patients, especially in the context of the new drugs available for myelodysplastic syndromes.