Myelodysplastic syndromes: a review of therapeutic progress over the past 10 years

INTRODUCTION

Myelodysplastic syndromes (MDS) represent a range of bone marrow disorders, with patients affected by cytopenias and risk of progression to AML. There are limited therapeutic options available for patients, including hypomethylating agents (azacitidine/decitabine), growth factor support, lenalidomide, and allogeneic stem cell transplant.

AREAS COVERED

This review provides an overview of the progress made over the past decade for emerging therapies for lower- and higher-risk MDS (MDS-HR). We also cover advances in prognostication, supportive care, and use of allogeneic SCT in MDS.

EXPERT OPINION

While there have been no FDA-approved therapies for MDS in the past decade, we anticipate the approval of luspatercept based on results from the MEDALIST trial for patients with lower-risk MDS (MDS-LR) and ringed sideroblasts who have failed or are ineligible for erythropoiesis stimulating agents (ESAs). With growing knowledge of the biologic and molecular mechanisms underlying MDS, it is anticipated that new therapies will be approved in the coming years.

Evolving therapies for lower-risk myelodysplastic syndromes

The development in the therapeutic landscape of myelodysplastic syndromes (MDS) has substantially lagged behind other hematologic malignancies with no new drug approvals for MDS for 13 years since the approval of decitabine in the United States in 2006. While therapeutic concepts for MDS patients continue to be primarily defined by clinical-pathologic risk stratification tools such as the International Prognostic Scoring System (IPSS) and its revised version IPSS-R, our understanding of the genetic landscape and the molecular pathogenesis of MDS has greatly evolved over the last decade. It is expected that the therapeutic approach to MDS patients will become increasingly individualized based on prognostic and predictive genetic features and other biomarkers. Herein, we review the current treatment of lower-risk MDS patients and discuss promising agents in advanced clinical testing for the treatment of symptomatic anemia in lower-risk MDS patients such as luspatercept and imetelstat. Lastly, we review the clinical development of new agents and the implications of the wider availability of mutational analysis for the management of individual MDS patients.

Treatment of Lymphoid and Myeloid Malignancies by Immunomodulatory Drugs

Thalidomide and its derivatives (lenalidomide, pomalidomide, avadomide, iberdomide hydrochoride, CC-885 and CC-90009) form the family of immunomodulatory drugs (IMiDs). Lenalidomide (CC5013, Revlimid®) was approved by the US FDA and the EMA for the treatment of multiple myeloma (MM) patients, low or intermediate-1 risk transfusion-dependent myelodysplastic syndrome (MDS) with chromosome 5q deletion [del(5q)] and relapsed and/or refractory mantle cell lymphoma following bortezomib. Lenalidomide has also been studied in clinical trials and has shown promising activity in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Lenalidomide has anti-inflammatory effects and inhibits angiogenesis. Pomalidomide (CC4047, Imnovid® [EU], Pomalyst® [USA]) was approved for advanced MM insensitive to bortezomib and lenalidomide. Other IMiDs are in phases 1 and 2 of clinical trials. Cereblon (CRBN) seems to have an important role in IMiDs action in both lymphoid and myeloid hematological malignancies. Cereblon acts as the substrate receptor of a cullin-4 really interesting new gene (RING) E3 ubiquitin ligase CRL4CRBN. This E3 ubiquitin ligase in the absence of lenalidomide ubiquitinates CRBN itself and the other components of CRL4CRBN complex. Presence of lenalidomide changes specificity of CRL4CRBN which ubiquitinates two transcription factors, IKZF1 (Ikaros) and IKZF3 (Aiolos), and casein kinase 1α (CK1α) and marks them for degradation in proteasomes. Both these transcription factors (IKZF1 and IKZF3) stimulate proliferation of MM cells and inhibit T cells. Low CRBN level was connected with insensitivity of MM cells to lenalidomide. Lenalidomide decreases expression of protein argonaute-2, which binds to cereblon. Argonaute-2 seems to be an important drug target against IMiDs resistance in MM cells. Lenalidomide decreases also basigin and monocarboxylate transporter 1 in MM cells. MM cells with low expression of Ikaros, Aiolos and basigin are more sensitive to lenalidomide treatment. The CK1α gene (CSNK1A1) is located on 5q32 in commonly deleted region (CDR) in del(5q) MDS. Inhibition of CK1α sensitizes del(5q) MDS cells to lenalidomide. CK1α mediates also survival of malignant plasma cells in MM. Though, inhibition of CK1α is a potential novel therapy not only in del(5q) MDS but also in MM. High level of full length CRBN mRNA in mononuclear cells of bone marrow and of peripheral blood seems to be necessary for successful therapy of del(5q) MDS with lenalidomide. While transfusion independence (TI) after lenalidomide treatment is more than 60% in MDS patients with del(5q), only 25% TI and substantially shorter duration of response with occurrence of neutropenia and thrombocytopenia were achieved in lower risk MDS patients with normal karyotype treated with lenalidomide. Shortage of the biomarkers for lenalidomide response in these MDS patients is the main problem up to now.

Azacitidine with or without lenalidomide in higher risk myelodysplastic syndrome & low blast acute myeloid leukemia

Standard treatment for higher risk myelodysplastic syndromes, chronic myelomonocytic leukemia and low blast acute myeloid leukemia is azacitidine. In single arm studies, adding lenalidomide had been suggested to improve outcomes. The ALLG MDS4 phase II trial randomized such patients to standard azacitidine or combination azacitidine (75mg/m²/d days 1 to 5) with lenalidomide (10mg days 1–21 of 28-day cycle from cycle 3) to assess clinical benefit (alive without progressive disease) at 12 months. A total of 160 patients were enrolled; median age 70.7 years (range 42.5-87.2), 31.3% female with 14% chronic myelomonocytic leukemia, 12% acute myeloid leukemia and 74% myelodysplastic syndromes. Adverse events were similar in both arms. There was excellent delivery of protocol therapy (median azacitidine cycles 11 both arms) with few dose reductions, delays or early cessations. At median follow up 33.1 months (range 0.7-59.5), the rate of clinical benefit at 12 months was 65% azacitidine arm and 54% lenalidomide+azacitidine arm (P=0.2). There was no difference in clinical benefit between each arm according to WHO diagnostic subgroup or IPSS-R. Overall response rate was 57% in azacitidine arm and 69% in lenalidomide+azacitidine (P=0.14). There was no difference in progression- free or overall survival between the arms (each P>0.12). Although the combination of lenalidomide and azacitidine was tolerable, there was no improvement in clinical benefit, response rates or overall survival in higher risk myelodysplastic syndrome, chronic myelomonocytic leukemia or low blast acute myeloid leukemia patients compared to treatment with azacitidine alone. This trial was registered at www.anzc-tr.org.au as ACTRN12610000271000.

Infections in Myelodysplastic Syndrome in Relation to Stage and Therapy

Infections remain a significant problem in myelodysplastic syndromes (MDS) in treated as well in non-treated patients and assume a particular complexity. The susceptibility to infections is due, in the absence of intensive chemotherapies, mainly to functional defects in the myeloid lineage with or without neutropenia. Furthermore, MDS includes a heterogeneous group of patients with very different prognosis, therapy and risk factors regarding survival and infections. You should distinguish risk factors related to the disease, like as neutrophils function impairment, neutropenia, unfavorable cytogenetics and bone marrow insufficiency; factors related to the patient, like as age and comorbidities, and factors related to the therapy. When the patients with MDS are submitted to intensive chemotherapy with and without hematopoietic stem cell transplantation (HSCT), they have a risk factor for infection very similar to that of patients with acute myeloid leukemia (AML), and mostly related to neutropenia. Patients with MDS treated with supportive therapy only or with demethylating agent or lenalidomide or immunosuppressive drugs should have a tailored approach. Most of the infections in MDS originate from bacteria, and the main risk factors are represented by neutropenia, thrombocytopenia, and unfavorable cytogenetics. Thus, it is reasonable to give antibacterial prophylaxis to patients who start the therapy with demethylating agents with a number of neutrophils <500 × 10⁹/L, or with thrombocytopenia and unfavorable cytogenetics. The antifungal prophylaxis is not considered cost/benefit adequate and should be taken into consideration only when there is an antecedent fungal infection or presence of filamentous fungi in the surveillance cultures. Subjects submitted to immunosuppression with ATG+CSA have a high rate of infections, and when severely neutropenic should ideally be nursed in isolation, should be given prophylactic antibiotics and antifungals, regular mouth care including an antiseptic mouthwash.

Trends in Clinical Investigation for Myelodysplastic Syndromes

Myelodysplastic syndrome (MDS) paradigms have been dramatically changed over the last 10 years by major breakthroughs on both pathophysiologic and therapeutic aspects. It is currently a field of intense clinical investigation as new challenges have emerged in both low-risk and high-risk populations. In low-risk MDS, long-term control of anemia is a major issue, and second-line treatments after failure of erythropoiesis-stimulating agents are warranted. Several promising therapies are available, and there are many open questions on how to select the most adapted agent and/or sequence of agents in a specific individual. For high-risk MDS patients, improvement of frontline treatment (namely hypomethylating agents) and identification of valid treatments for relapsed/refractory patients are of paramount importance. This review attempts to define these challenges, summarize the results of the most recent and promising investigational strategies in the field, and to describe the future directions.

Increasing the effectiveness of hematopoiesis in myelodysplastic syndromes: erythropoiesis-stimulating agents and transforming growth factor-β superfamily inhibitors

Patients with lower-risk myelodysplastic syndromes (MDS) are mainly affected by chronic anemia and fatigue. Treatment strategies aim to improve anemia and quality of life, as well as iron overload due to red blood cell transfusion support. To promote proliferation and differentiation of erythropoiesis, erythropoiesis-stimulating agents (ESAs) such as erythropoietin (EPO) and mimetics are applied as first-line therapy in a large fraction of lower-risk MDS patients. In general, ESAs yield favorable responses in about half of the patients, although responses are often short-lived. In fact, many ESA-refractory patients harbor defects in late-stage erythropoiesis downstream of EPO action. Novel transforming growth factor (TGF)-β superfamily inhibitors sotatercept and luspatercept represent a promising approach to alleviate anemia by stimulating erythroid differentiation.

Management of lower-risk myelodysplastic syndromes without del5q: current approach and future trends

INTRODUCTION

Myelodysplastic syndromes (MDS) are characterized by progressive bone marrow failure manifesting as blood cytopenia and a variable risk of progression into acute myeloid leukemia. MDS is heterogeneous in biology and clinical behavior. MDS are generally divided into lower-risk (LR) and higher-risk (HR) MDS. Goals of care in HR-MDS focus on changing the natural history of the disease, whereas in LR-MDS symptom control and quality of life are the main goals. Areas covered: We review the epidemiology, tools of risk assessment, and the available therapeutic modalities for LR-MDS. We discuss the use of erythropoiesis stimulating agents (ESAs), immunosuppressive therapy (IST), lenalidomide and the hypomethylating agents (HMAs). We also discuss the predictors of response, combination treatment modalities, and management of iron overload. Lastly, we overview the most promising investigational agents for LR-MDS. Expert commentary: It remains unclear how to best incorporate a wealth of new genetic and epigenetic prognostic markers into risk assessment tools especially for LR-MDS patients. Only a subset of patients respond to current treatment modalities and most responders eventually lose their response. Once standard therapeutic options fail, management becomes more challenging. Combination-based approaches have been largely unsuccessful. Among the most promising investigational are the TPO agonists, TGF- β pathway inhibitors, telomerase inhibitors, and the splicing modifiers.

Lenalidomide use in myelodysplastic syndromes: Insights into the biologic mechanisms and clinical applications

Myelosysplastic syndromes (MDS) include a heterogeneous group of clonal myeloid neoplasms characterized by ineffective hematopoiesis leading to blood cytopenias and a variable risk of progression into acute myeloid leukemia (AML). Although the hypomethylating agent azacitidine prolongs survival among patients with higher risk (HR)-MDS compared with conventional care, no drug has been shown conclusively to prolong survival or delay progression to AML among patients with lower-risk MDS (LR-MDS). Lenalidomide is the drug with the most impressive clinical activity in the subset of anemic LR-MDS patients who harbor a deletion of the long arm of chromosome 5 (5q-), where it leads to high rates of transfusion independence and cytogenetic responses. Furthermore, lenalidomide delays progression to AML and prolongs survival among responders. In this article, we review the recently recognized mechanisms of action of lenalidomide and discuss the most recent clinical data regarding its use in patients with both 5q- MDS as well as non-5q- MDS. Finally, we forecast the future directions to improve the efficacy of lenalidomide in MDS with and without 5q-. Cancer 2017;123:1703-1713. © 2017 American Cancer Society.

Efficacy and Safety of Lenalidomide for Treatment of Low-/Intermediate-1-Risk Myelodysplastic Syndromes with or without 5q Deletion: A Systematic Review and Meta-Analysis

Background

Lenalidomide could effectively induce red blood cell (RBC) transfusion independence (TI) in patients with lower-risk (Low/Intermediate-1) myelodysplastic syndrome (MDS) with or without 5q deletion. However whether lenalidomide ultimately improves the overall survival (OS) of lower-risk MDS patients and reduces the progression to AML remains controversial.

Method

A meta-analysis was conducted to examine the efficacy and safety of lenalidomide in the treatment of lower-risk MDS. Efficacy was assessed according to erythroid hematologic response (HI-E), cytogenetic response (CyR), OS and AML progression. Safety was evaluated based on the occurrence rates of grades 3–4 adverse events (AEs).

Results

Seventeen studies were included consisting of a total of 2160 patients. The analysis indicated that the overall rate of HI-E was 58% with 95% confidence interval (CI) of 43–74%. The pooled estimates for the rates of CyR, complete CyR, and partial CyR were 44% (95% CI 19–68%), 21% (95% CI 13–30%) and 23% (95% CI 15–32%), respectively. The patients with 5q deletion had significantly higher rate of HI-E and CyR than those without 5q deletion (P = 0.002 and 0.001, respectively). The incidences of grades 3–4 neutropenia, thrombocytopenia, leukopenia, anemia, deep vein thrombosis, diarrhea, fatigue and rash were 51% (95% CI 30–73%), 31% (95% CI 20–42%), 9% (95% CI 5–13%), 7% (95% CI 2–12%), 3% (95% CI 2–5%), 3% (95% CI 1–5%), 2% (95% CI 1–4%) and 2% (95% CI 1–3%), respectively. Lenalidomide significantly improved OS (HR: 0.62, 95% CI 0.47–0.83, P = 0.001) and lowered the risk of AML progression in del(5q) patients (RR: 0.61, 95% CI 0.41–0.91, P = 0.014).

Conclusions

In spite of the AEs, lenalidomide could be effectively and safely used for the treatment of lower-risk MDS patients with or without 5q deletion.

Myelodysplastic Syndromes and Acute Myeloid Leukemia in the Elderly

Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are hematologic diseases that frequently affect older adults. Treatment is challenging. Management of older adults with MDS and AML needs to be individualized, accounting for both the heterogeneity of disease biology and patient characteristics, which can influence life expectancy and treatment tolerance. Clinical trials accounting for the heterogeneity of tumor biology and physiologic changes of aging are needed to define optimal standards of care. This article highlights key evidence related to the management of older adults with MDS and AML and highlights future directions for research.

Myelodysplastic Syndromes in the Elderly: Treatment Options and Personalized Management

Myelodysplastic syndromes (MDS) are typical diseases of the elderly, with a median age of 68-75 years at initial diagnosis. Demographic changes producing an increased proportion of elderly in our societies mean the incidence of MDS will rise dramatically. Considering the increasing number of treatment options, ranging from best supportive care to hematopoietic stem cell transplantation (HSCT), decision making is rather complex in this cohort of patients. Moreover, aspects of the aging process also have to be considered in therapy planning. Treatment of elderly MDS patients is dependent on the patient's individual risk and prognosis. Comorbidities play an essential role as predictors of survival and therapy tolerance. Age-adjusted models and the use of geriatric assessment scores are described as a basis for individualized treatment algorithms. Specific treatment recommendations for the different groups of patients are given. Currently available therapeutic agents, including supportive care, erythropoiesis-stimulating agents (ESAs), immune-modulating agents, hypomethylating agents, and HSCT are described in detail and discussed with a special focus on elderly MDS patients. The inclusion of elderly patients in clinical trials is of utmost importance to obtain data on efficacy and safety in this particular group of patients. Endpoints relevant for the elderly should be integrated, including maintenance of quality of life and functional activities as well as evaluation of use of healthcare resources.

Effect of lenalidomide treatment on clonal architecture of myelodysplastic syndromes without 5q deletion

Non-del(5q) transfusion-dependent low/intermediate-1 myelodysplastic syndrome (MDS) patients achieve an erythroid response with lenalidomide in 25% of cases. Addition of an erythropoiesis-stimulating agent could improve response rate. The impact of recurrent somatic mutations identified in the diseased clone in response to lenalidomide and the drug's effects on clonal evolution remain unknown. We investigated recurrent mutations by next-generation sequencing in 94 non-del(5q) MDS patients randomized in the GFM-Len-Epo-08 clinical trial to lenalidomide or lenalidomide plus epoetin β. Clonal evolution was analyzed after 4 cycles of treatment in 42 cases and reanalyzed at later time points in 18 cases. The fate of clonal architecture of single CD34(+)CD38(-) hematopoietic stem cells was also determined in 5 cases. Mutation frequency was >10%: SF3B1 (74.5%), TET2 (45.7%), DNMT3A (20.2%), and ASXL1 (19.1%). Analysis of variant allele frequencies indicated a decrease of major mutations in 15 of 20 responders compared with 10 of 22 nonresponders after 4 cycles. The decrease in the variant allele frequency of major mutations was more significant in responders than in nonresponders (P < .001). Genotyping of single CD34(+)CD38(-) cell-derived colonies showed that the decrease in the size of dominant subclones could be associated with the rise of founding clones or of hematopoietic stem cells devoid of recurrent mutations. These effects remained transient, and disease escape was associated with the re-emergence of the dominant subclones. In conclusion, we show that, although the drug initially modulates the distribution of subclones, loss of treatment efficacy coincides with the re-expansion of the dominant subclone. This trial was registered at www.clinicaltrials.gov as #NCT01718379.

Lenalidomide with or without erythropoietin in transfusion-dependent erythropoiesis-stimulating agent-refractory lower-risk MDS without 5q deletion

After failure of erythropoiesis-stimulating agents (ESAs), lenalidomide (LEN) yields red blood cell (RBC) transfusion independence (TI) in 20-30% of lower-risk non-del5q myelodysplastic syndrome (MDS). Several observations suggest an additive effect of ESA and LEN in this situation. We performed a randomized phase III study in 131 RBC transfusion-dependent (TD, median transfusion requirement six RBC units per 8 weeks) lower-risk ESA-refractory non-del5q MDS. Patients received LEN alone, 10 mg per day, 21 days per 4 weeks (L arm) or LEN (same schedule) + erythropoietin (EPO) beta, 60,000 U per week (LE arm). In an intent-to-treat (ITT) analysis, erythroid response (HI-E, IWG 2006 criteria) after four treatment cycles (primary end point) was 23.1% (95% CI 13.5-35.2) in the L arm and 39.4% (95% CI 27.6-52.2) in the LE arm (P=0.044), while RBC-TI was reached in 13.8 and 24.2% of the patients in the L and LE arms, respectively (P=0.13). Median response duration was 18.1 and 15.1 months in the L and LE arms, respectively (P=0.47). Side effects were moderate and similar in the two arms. Low baseline serum EPO level and a G polymorphism of CRBN gene predicted HI-E. Combining LEN and EPO significantly improves erythroid response over LEN alone in lower-risk non-del5q MDS patients with anemia resistant to ESA.

Acute myeloid leukemia and myelodysplastic syndromes in older adults

Treatment of older adults with acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS) is challenging because of disease morbidity and associated treatments. Both diseases represent a genetically heterogeneous group of disorders primarily affecting older adults, with treatment strategies ranging from supportive care to hematopoietic stem-cell transplantation. Although selected older adults can benefit from intensive therapies, as a group they experience increased treatment-related morbidity, are more likely to relapse, and have decreased survival. Age-related outcome disparities are attributed to both tumor and patient characteristics, requiring an individualized approach to treatment decision making beyond consideration of chronologic age alone. Selection of therapy for any individual requires consideration of both disease-specific risk factors and estimates of treatment tolerance and life expectancy derived from evaluation of functional status and comorbidity. Although treatment options for older adults are expanding, clinical trials accounting for the heterogeneity of tumor biology and aging are needed to define standard-of-care treatments for both disease groups. In addition, trials should include outcomes addressing quality of life, maintenance of independence, and use of health care services to assist in patient-centered decision making. This review will highlight available evidence in treatment of older adults with AML or MDS and unanswered clinical questions for older adults with these diseases.

Past, present and future treatment strategies in peripheral T-cell lymphomas

SUMMARY 

Nodal peripheral T-cell lymphomas (PTCLs) are very aggressive tumors characterized by poor response to conventional chemotherapy and dismal prognosis. Recent evidence has indicated that, at least for patients aged less than 60 years, frontline high-dose chemotherapy followed by autologous stem cell transplantation can be an effective strategy. Unfortunately, however, a significant fraction of patients cannot benefit from this approach, due to age, poor performance status or early relapse. In addition, a percentage of transplanted patients eventually relapse. In this article, based on their experience and on the most recent literature, the authors review the current concept on PTCL treatment, focusing on the most common PTCL nodal subtypes.

Analysis of the efficacy of lenalidomide in patients with intermediate-1 risk myelodysplastic syndrome without 5q deletion

The aim of this study was to evaluate the efficacy and adverse effects of lenalidomide in the treatment of intermediate-1 risk non-5q deletion [non-del (5q)] myelodysplastic syndrome (MDS). A total of 30 patients with MDS were classified through G-banding chromosome karyotype analysis and fluorescence in situ hybridization (FISH). According to the International Prognostic Scoring System scores, among the 30 patients, 23 and seven cases had scores of 0.5 and 1.0, respectively. Lenalidomide (Revlimid^®), 10 mg/day) was administered for 21 days every 28 days. All 30 cases were treated with lenalidomide for at least three cycles, including 20 cases with four cycles. The patients did not require erythropoietin, cyclosporine or iron chelation treatments. Statistical analysis was performed using SPSS statistical software version 13.0, and comparisons among groups were conducted using a t-test. The efficacy of lenalidomide was demonstrated in patients with intermediate-1 risk non-del (5q) MDS. Peripheral blood cell counts were improved following treatment, and absolute neutrophil, haemoglobin and platelet counts increased following 2–4 cycles of treatment. All patients became stable having undergone three cycles of treatment; however, 17 patients with chromosomal abnormalities had no cytogenetic response to the treatment, as confirmed through the FISH test. Patients with intermediate-1 risk non-del (5q) MDS treated with lenalidomide did not achieve complete haematological remission, although they demonstrated haematological improvement.

Current therapy of myelodysplastic syndromes

After being a neglected and poorly-understood disorder for many years, there has been a recent explosion of data regarding the complex pathogenesis of myelodysplastic syndromes (MDS). On the therapeutic front, the approval of azacitidine, decitabine, and lenalidomide in the last decade was a major breakthrough. Nonetheless, the responses to these agents are limited and most patients progress within 2 years. Allogeneic stem cell transplantation remains the only potentially curative therapy, but it is associated with significant toxicity and limited efficacy. Lack or loss of response after standard therapies is associated with dismal outcomes. Many unanswered questions remain regarding the optimal use of current therapies including patient selection, response prediction, therapy sequencing and combinations, and management of resistance. It is hoped that the improved understanding of the underpinnings of the complex mechanisms of pathogenesis will be translated into novel therapeutic approaches and better prognostic/predictive tools that would facilitate accurate risk-adaptive therapy.

Signal transduction inhibitors in treatment of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a group of hematologic disorders characterized by ineffective hematopoiesis that results in reduced blood counts. Although MDS can transform into leukemia, most of the morbidity experienced by these patients is due to chronically low blood counts. Conventional cytotoxic agents used to treat MDS have yielded some encouraging results but are characterized by many adverse effects in the predominantly elderly patient population. Targeted interventions aimed at reversing the bone marrow failure and increasing the peripheral blood counts would be advantageous in this cohort of patients. Studies have demonstrated over-activated signaling of myelo-suppressive cytokines such as TGF-β, TNF-α and Interferons in MDS hematopoietic stem cells. Targeting these signaling cascades could be potentially therapeutic in MDS. The p38 MAP kinase pathway, which is constitutively activated in MDS, is an example of cytokine stimulated kinase that promotes aberrant apoptosis of stem and progenitor cells in MDS. ARRY-614 and SCIO-469 are p38 MAPK inhibitors that have been used in clinical trials and have shown activity in a subset of MDS patients. TGF-β signaling has been therapeutically targeted by small molecule inhibitor of the TGF-β receptor kinase, LY-2157299, with encouraging preclinical results. Apart from TGF-β receptor kinase inhibition, members of TGF-β super family and BMP ligands have also been targeted by ligand trap compounds like Sotatercept (ACE-011) and ACE-536. The multikinase inhibitor, ON-01910.Na (Rigosertib) has demonstrated early signs of efficacy in reducing the percentage of leukemic blasts and is in advanced stages of clinical testing. Temsirolimus, Deforolimus and other mTOR inhibitors are being tested in clinical trials and have shown preclinical efficacy in CMML. EGF receptor inhibitors, Erlotinib and Gefitinib have shown efficacy in small trials that may be related to off target effects. Cell cycle regulator inhibitors such as Farnesyl transferase inhibitors (Tipifarnib, Lonafarnib) and MEK inhibitor (GSK1120212) have shown acceptable toxicity profiles in small studies and efforts are underway to select mutational subgroups of MDS and AML that may benefit from these inhibitors. Altogether, these studies show that targeting various signal transduction pathways that regulate hematopoiesis offers promising therapeutic potential in this disease. Future studies in combination with high resolution correlative studies will clarify the subgroup specific efficacies of these agents.

Dendritic cells in myelodysplastic syndromes: from pathogenesis to immunotherapy

Myelodysplastic syndromes (MDS) are clonal disorders of the hematopoietic stem cell characterized by ineffective hematopoiesis leading to peripheral cytopenias. Different processes are involved in its pathogenesis, such as (epi)genetic alterations and immunological dysfunctions. The nature of immune dysregulation is markedly different between various MDS risk groups. In low-risk MDS, the immune system is in a proinflammatory state, whereas in high-risk disease, immunosuppressive features facilitate expansion of the dysplastic clone and can eventually lead to disease progression to acute myeloid leukemia. Various cell types contribute to dysregulation of immune responses in MDS. Dendritic cells (DCs) are important regulators of immunity. However, the role of DCs in MDS has yet to be elucidated. It has been suggested that impaired DC function can hamper adequate immune responses. This review focuses on the involvement of DCs in immune dysregulation in low- and high-risk MDS and the implications for DC-targeted therapies.

How we treat lower-risk myelodysplastic syndromes

Lower-risk myelodysplastic syndromes (MDSs) are defined as having low or intermediate 1 risk by the International Prognostic Scoring System and are characterized mainly by anemia in most cases. Supportive care--primarily red blood cell transfusions--remains an important component of their treatment, but exposes patients to insufficient correction of anemia, alloimmunization, and organ iron overload (for which the role of iron chelation remains debated). Treatment aimed at preventing anemia recurrence should therefore be used whenever possible. Erythropoiesis stimulating agents remain the first-line treatment of anemia in most lower-risk MDS without del(5q), whereas anemia of low-risk MDS with del 5q responds to lenalidomide in two-thirds of the cases, but this drug should be used cautiously because profound cytopenias may occur initially. Treatment after failure of those first-line therapies are disappointing overall, with many patients eventually requiring long-term transfusions, but encouraging results have been reported with hypomethylating agents and lenalidomide. Selected patients respond to antithymocyte globulins, and thrombopoietin receptor agonists are under investigation in lower-risk MDS with thrombocytopenia. Some patients, while remaining at a "lower risk" MDS level, have severe cytopenias and/or poor prognostic factors, found using newer prognostic parameters, or resistance to treatment, making them urgent candidates for more intensive approaches, including allogeneic stem cell transplantation.

The application and biology of immunomodulatory drugs (IMiDs) in cancer

Immunomodulatory drugs (IMiDs) have been used in hematologic malignancies for the last decade. However, the mechanism of action of IMiDs is largely unknown. Here we provide a comprehensive overview of pivotal studies, recent advances in the application of IMiDs in cancer as well as their effects on hematopoietic stem cells including the risk of secondary malignancies. IMiDs have a well-established role as first-line therapy for patients with newly diagnosed and relapsed/refractory multiple myeloma (MM). Variant combinations of IMiDs with other chemotherapy reagents show promising outcomes in MM. Recent concerns on increased rate of secondary cancer in MM patients treated with maintenance lenalidomide were raised. But analysis of maintenance studies showed that the benefit of maintenance outweighs the risk of secondary cancers in MM. IMiDs also show efficacy in myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), Non-Hodgkin's lymphoma (NHL) and myelofibrosis (MF), but not in solid tumors. The major adverse effects are venous thromboembolism, neuropathy and cytopenias. IMiDs induce expansion and self-renewal of CD34+ hematopoietic progenitors and inhibit lineage maturation/differentiation by affecting critical transcription factors which might contribute to myelosuppression effect of IMiDs.