Phase 2 study of low-dose clofarabine plus cytarabine for patients with higher-risk myelodysplastic syndrome who have relapsed or are refractory to hypomethylating agents

Advances in the management of higher-risk myelodysplastic syndromes: future prospects

Higher-risk myelodysplastic syndromes (HR-MDS) are defined using a number of prognostic scoring systems that include the degree of cytopenias, percentage of blasts, cytogenetic alterations, and more recently genomic data. HR-MDS encompasses characteristics such as progressive cytopenias, increased bone marrow blasts, unfavorable cytogenetics, and an adverse mutational profile. Survival is generally poor, and patients require therapy to improve outcomes. Hypomethylating agents (HMAs), such as azacitidine, decitabine, and more recently, oral decitabine/cedazuridine, are the only approved therapies for HR-MDS. These are often continued until loss of response, progression, or unacceptable toxicity. Combinations including an HMA plus other drugs have been investigated but have not demonstrated better outcomes compared to single-agent HMA. Moreover, in a disease of high genomic complexity such as HR-MDS, therapy targeting specific genomic abnormalities is of interest. This review will examine the biological underpinnings of HR-MDS, its therapeutic landscape in the frontline and relapsed settings, as well as the impact of hematopoietic stem cell transplantation, the only known curative intervention for this disease.

Infections and antimicrobial prophylaxis in patients with myelodysplastic syndromes

Infectious complications are an important cause of morbidity and mortality in patients with myelodysplastic syndromes (MDS). Preventing infections could significantly improve both survival and quality of life. Unfortunately, both infections and antimicrobial prophylaxis in patients with MDS are incompletely assessed due to the heterogeneity of disorders included in each publication, changing definitions over time, and lack of standardized prophylaxis practices. Despite these limitations, some basic statements can be made. Infections in MDS are associated with neutropenia. Patients with lower-risk (LR) MDS tend to have fewer infections compared to patients with higher-risk (HR) MDS, which may be related to the different prevalence of neutropenia in the 2 groups. Pneumonia is the most common infection, and bacteria are the most common pathogens. Invasive fungal infections (IFI) are uncommon. Reactivation of latent viruses are rare. With the limited data available, we agree that antibacterial prophylaxis can be considered in patients with HR-MDS during severe neutropenia and early cycles of therapy when infections are most likely to occur. Given the low prevalence of IFI and viral reactivation, antimicrobial prophylaxis for these pathogens is less likely to be advantageous for most patients, although antifungal prophylaxis with activity against mold is commonly used in patients with persistent, profound neutropenia. Ultimately, improved data collection regarding infections and antimicrobial prophylaxis is needed to improve care for patients with MDS.

Phase 1/2 study of CPX-351 for patients with Int-2 or high risk International Prognostic Scoring System myelodysplastic syndromes and chronic myelomonocytic leukaemia after failure to hypomethylating agents

Failure after hypomethylating agents (HMAs) is associated with dismal outcomes in higher risk myelodysplastic syndromes (HR-MDS) or chronic myelomonocytic leukaemia (CMML). We aimed to evaluate the safety and preliminary activity of lower doses of CPX-351, a liposomal encapsulation of cytarabine and daunorubicin, in a single-centre, phase 1/2 study for patients with HR-MDS or CMML after HMA failure. Four doses of CPX-351 (10, 25, 50 and 75 units/m2 ) administered on Days 1, 3 and 5 of induction and Days 1 and 3 of consolidation were evaluated. Between June 2019 and June 2023, 25 patients were enrolled (phase 1: n = 15; phase 2: n = 10) including 19 (76%) with HR-MDS and 6 (24%) with CMML. Most common grade 3-4 non-haematological treatment-emergent adverse events were febrile neutropenia (n = 12, 48%) and lung infection (n = 5, 20%). Three patients (age >75) experienced cardiac toxicity at the 75 units/m2 dose. Further enrolment continued at 50 units/m2 . Four- and 8-week mortality were 0% and 8% respectively. The overall response rate was 56% with median relapse-free and overall survivals of 9.2 (95% CI 3.2-15.1 months) and 8.7 months (95% CI 1.8-15.6 months) respectively. These data suggest that lower doses of CPX-351 are safe. Further studies are needed to evaluate its activity.

Clofarabine Preconditioning followed by Allogeneic Transplant Using TBI and Post-Transplant Cyclophosphamide for Relapsed Refractory Leukemia

Acute myeloid leukemia patients with induction failure or relapsed refractory disease have minimal chance of achieving remission with subsequent treatments. Several trials have shown the feasibility of clofarabine-based conditioning in allogeneic stem cell transplants (allo-HSCT) for non-remission AML patients. Pre-transplant conditioning with clofarabine followed by reduced-intensity allo-HSCT has also demonstrated a potential benefit in those patients with human leukocyte antigen (HLA)-identical donors, but it is not commonly used in haploidentical and mismatched transplants. In this case report, we describe our experience of seven cases of non-remission AML who received clofarabine preconditioning followed by an allo-HSCT with PTCy. The 2-year overall survival and disease-free survival was 83.3% (95% confidence interval (CI): 27.3-97.9%) and 85.7% (95% CI: 33.4-97.9%). Median days of neutrophil and platelet recovery were 16 (range of 13-23) and 28 (range of 17-75), respectively. The cumulative incidence of grade II-IV acute graft-versus-host disease (GVHD) at day 100 and chronic GVHD at 1-year showed 28.6% (95% CI: 8-74.2%) and 28.6% (95% CI: 3-63.9%), respectively. The two-year relapse rate was 14.3% (95% CI: 2.14-66.6%). One-year GVHD-free relapse-free survival (GFRS) at 1-year was 71.4% (95% CI: 25.8-92%). Our patients showed successful outcomes with clofarabine preconditioning to reduce the leukemic burden at the pre-transplant period followed by PTCy to reduce GVHD resulting in lower relapsed rate and better GFRS in these patients.

Optimizing Treatment Options for Newly Diagnosed Acute Myeloid Leukemia in Older Patients with Comorbidities

Traditionally, the goal of AML therapy has been to induce remission through intensive chemotherapy, maintain long-term remission using consolidation therapy, and achieve higher rates of a cure by allogeneic transplantation in patients with a poor prognosis. However, for the elderly patients and those with comorbidities, the toxicity often surpasses the therapeutic benefits of intensive chemotherapy. Consequently, low-intensity therapies, such as the combination of a hypomethylating agent with venetoclax, have emerged as promising treatment options for elderly patients. Given the rise of low-intensity therapies as the leading treatment option for the elderly, it is increasingly important to consider patients' age and comorbidities when selecting a treatment option. The recently proposed comorbidity-based risk stratification for AML allows prognosis stratification not only in patients undergoing intensive chemotherapy, but also in those receiving low-intensity chemotherapy. Optimizing treatment intensity based on such risk stratification is anticipated to balance treatment efficacy and safety, and will ultimately improve the life expectancy for patients with AML.

What's Next after Hypomethylating Agents Failure in Myeloid Neoplasms? A Rational Approach

Hypomethylating agents (HMA) such as azacitidine and decitabine are a mainstay in the current management of patients with myelodysplastic syndromes/neoplasms (MDS) and acute myeloid leukemia (AML) as either single agents or in multidrug combinations. Resistance to HMA is not uncommon, and it can result due to several tumor cellular adaptations. Several clinical and genomic factors have been identified as predictors of HMA resistance. However, the management of MDS/AML patients after the failure of HMA remains challenging in the absence of standardized guidelines. Indeed, this is an area of active research with several potential therapeutic agents currently under development, some of which have demonstrated therapeutic potential in early clinical trials, especially in cases with particular mutational characteristics. Here, we review the latest findings and give a rational approach for such a challenging scenario.

Current Understanding of DDX41 Mutations in Myeloid Neoplasms

The DEAD-box RNA helicase 41 gene, DDX41, is frequently mutated in hereditary myeloid neoplasms, identified in 2% of entire patients with AML/MDS. The pathogenesis of DDX41 mutation is related to the defect in the gene's normal functions of RNA and innate immunity. About 80% of patients with germline DDX41 mutations have somatic mutations in another allele, resulting in the biallelic DDX41 mutation. Patients with the disease with DDX41 mutations reportedly often present with the higher-grade disease, but there are conflicting reports about its impact on survival outcomes. Recent studies using larger cohorts reported a favorable outcome with a better response to standard therapies in patients with DDX41 mutations to patients without DDX41 mutations. For stem-cell transplantation, it is important for patients with DDX41 germline mutations to identify family donors early to improve outcomes. Still, there is a gap in knowledge on whether germline DDX41 mutations and its pathology features can be targetable for treatment, and what constitutes an appropriate screening/surveillance strategy for identified carriers. This article reviews our current understanding of DDX41 mutations in myeloid neoplasms in pathologic and clinical features and their clinical implications.

Therapeutic Advances in Immunotherapies for Hematological Malignancies

Following the success of immunotherapies such as chimeric antigen receptor transgenic T-cell (CAR-T) therapy, bispecific T-cell engager therapy, and immune checkpoint inhibitors in the treatment of hematologic malignancies, further studies are underway to improve the efficacy of these immunotherapies and to reduce the complications associated with their use in combination with other immune checkpoint inhibitors and conventional chemotherapy. Studies of novel therapeutic strategies such as bispecific (tandem or dual) CAR-T, bispecific killer cell engager, trispecific killer cell engager, and dual affinity retargeting therapies are also underway. Because of these studies and the discovery of novel immunotherapeutic target molecules, the use of immunotherapy for diseases initially thought to be less promising to treat with this treatment method, such as acute myeloid leukemia and T-cell hematologic tumors, has become a reality. Thus, in this coming era of new transplantation- and chemotherapy-free treatment strategies, it is imperative for both scientists and clinicians to understand the molecular immunity of hematologic malignancies. In this review, we focus on the remarkable development of immunotherapies that could change the prognosis of hematologic diseases. We also review the molecular mechanisms, development processes, clinical efficacies, and problems of new agents.

Impact of Lenalidomide Treatment on Overall Survival in Patients With Lower-Risk, Transfusion-Dependent Myelodysplastic Syndromes

BACKGROUND

For patients with lower-risk (LR) myelodysplastic syndromes (MDS), overall survival (OS) is rarely a primary clinical trial endpoint. Treatments such as lenalidomide can reduce red blood cell (RBC) transfusion burden (TB) and serum ferritin, but the long-term impact on OS remains undetermined.

PATIENTS AND METHODS

Data from 3 trials evaluating lenalidomide in patients with LR-MDS (the phase 2 MDS-003 and phase 3 MDS-004 trials in del[5q]; the phase 3 trial MDS-005 in non-del[5q] patients) were pooled. Predictors of OS were assessed by multivariate analysis using time-dependent models for TB and RBC transfusion independence (RBC-TI), and a landmark analysis of RBC-TI at 17 weeks. Separate analyses using MDS-004 and MDS-005 data determined the relationship between OS and serum ferritin.

RESULTS

Median follow-up for MDS-003, MDS-004, and MDS-005 was 3.2, 3.0, and 1.7 years, respectively. In multivariate analyses, transfusion of ≥6 RBC units over 8 weeks was a significant predictor of shorter OS vs. 0 units in the time-dependent TB model (hazard ratio [HR] 4.65; 95% confidence interval [CI] 3.32-6.52; P < .0001). RBC-TI achievement was associated with prolonged OS in the time-dependent (HR 0.48; 95% CI 0.37-0.62; P < .0001) and landmark model (HR 0.57; 95% CI 0.44-0.75; P < .0001). Increased serum ferritin was associated with shorter OS (P < .0001).

CONCLUSION

This analysis of prospective trial data in patients with LR-MDS confirms lenalidomide may improve OS by reducing TB and serum ferritin. OS should be considered as an endpoint in future lower risk MDS clinical trials.

Emerging treatment options for patients with high-risk myelodysplastic syndrome

Myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis with peripheral blood cytopenias, dysplastic cell morphology, and a variable risk of progression to acute myeloid leukemia (AML). The hypomethylating agents (HMA) azacitidine and decitabine have been used for over a decade in MDS treatment and lead to a modest survival benefit. However, response rates are only around 40% and responses are mostly transient. For HMA-refractory patients the prognosis is poor and there are no therapies approved by the United States Food and Drug Administration.

Combinations of HMAs, especially along with immune checkpoint inhibitors, have shown promising signals in both the frontline and HMA-refractory setting. Several other novel agents including orally available and longer acting HMAs, the BCL-2 inhibitor venetoclax, oral agents targeting driver mutations (IDH1/2, FLT3), immunotherapies, and new options for intensive chemotherapy have been studied with variable success and will be reviewed herein. Except for the minority of patients with targetable driver mutations, HMAs – likely as part of combination therapies – will remain the backbone of frontline MDS treatment. However, the wider use of genetic testing may enable a more targeted and individualized therapy of MDS patients.

Myelodysplastic syndromes: 2021 update on diagnosis, risk stratification and management

DISEASE OVERVIEW

The myelodysplastic syndromes (MDS) are a very heterogeneous group of myeloid disorders characterized by peripheral blood cytopenias and increased risk of transformation to acute myelogenous leukemia (AML). Myelodysplastic syndromes occur more frequently in older males and in individuals with prior exposure to cytotoxic therapy.

DIAGNOSIS

Diagnosis of MDS is based on morphological evidence of dysplasia upon visual examination of a bone marrow aspirate and biopsy. Information obtained from additional studies such as karyotype, flow cytometry and molecular genetics is usually complementary and may help refine diagnosis.

RISK-STRATIFICATION

Prognosis of patients with MDS can be calculated using a number of scoring systems. In general, all these scoring systems include analysis of peripheral cytopenias, percentage of blasts in the bone marrow and cytogenetic characteristics. The most commonly accepted system is the Revised International Prognostic Scoring System (IPSS-R). Somatic mutations can help define prognosis and therapy.

RISK-ADAPTED THERAPY

Therapy is selected based on risk, transfusion needs, percent of bone marrow blasts, cytogenetic and mutational profiles, comorbidities, potential for allogeneic stem cell transplantation (alloSCT) and prior exposure to hypomethylating agents (HMA). Goals of therapy are different in lower-risk patients than in higher-risk individuals and in those with HMA failure. In lower-risk MDS, the goal is to decrease transfusion needs and transformation to higher risk disease or AML, as well as to improve survival. In higher-risk disease, the goal is to prolong survival. In 2020, we witnessed an explosion of new agents and investigational approaches. Current available therapies include growth factor support, lenalidomide, HMAs, intensive chemotherapy and alloSCT. Novel therapeutics approved in 2020 are luspatercept and the oral HMA ASTX727. At the present time, there are no approved interventions for patients with progressive or refractory disease particularly after HMA-based therapy. Options include participation in a clinical trial, cytarabine-based therapy or alloSCT.

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.

Treating Leukemia in the Time of COVID-19

The coronavirus disease 2019 (COVID-19) pandemic poses several challenges to the management of patients with leukemia. The biology of each leukemia and its corresponding treatment with conventional intensive chemotherapy, with or without targeted therapies (venetoclax, FLT3 inhibitors, IDH1/2 inhibitors, Bruton's tyrosine kinase inhibitors), introduce additional layers of complexity during COVID-19 high-risk periods. The knowledge about COVID-19 is accumulating rapidly. An important distinction is the prevalence of "exposure" versus "clinical infectivity," which determine the risk versus benefit of modifying potentially highly curative therapies in leukemia. At present, the rate of clinical infection is <1-2% worldwide. With a mortality rate of 1-5% in CO-VID-19 patients in the general population and potentially of >30% in patients with cancer, careful consideration should be given to the risk of COVID-19 in leukemia. Instead of reducing patient access to specialized cancer centers and modifying therapies to ones with unproven curative benefit, there is more rationale for less intensive, yet effective therapies that may require fewer clinic visits or hospitalizations. Here, we offer recommendations on the optimization of leukemia management during high-risk COVID-19 periods.

Allogeneic Stem Cell Transplantation in Therapy-Related Myelodysplasia after Autologous Transplantation for Lymphoma: A Retrospective Study of the Francophone Society of Bone Marrow Transplantation and Cellular Therapy

Therapy-related myelodysplastic syndrome (t-MDS) after autologous stem cell transplantation (ASCT) is a rare complication with no curative option. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) may be considered for eligible patients and has been understudied in t-MDS. We report 47 consecutive patients with t-MDS after an ASCT who underwent allo-HSCT with a median age of 58 years (range, 30 to 71 years) at transplantation and a median follow-up of 22 months (range, 0.7 to 107). The median overall survival (OS) was 6.9 months (95% confidence interval [CI], 0 to 19 months). OS rates were 45% (29% to 60%) and 30% (15% to 45%) at 1 and 3 years after transplantation, respectively. On univariate analysis, prior therapy for t-MDS before allo-HSCT (P = .02) and mismatched donors (P = .004) were associated with poor OS. Three-year nonrelapse mortality (NRM) and relapse rates were 44% (25% to 63%) and 41% (22% to 61%), respectively. Mismatched donors (P < .001) were associated with higher NRM and a high-risk MDS (P = .008) with a higher relapse risk. On multivariate analysis, HLA mismatch was associated with higher NRM (hazard ratio, 6.21; 95% CI, 1.63 to 23.62; P = .007). In conclusion, our results suggest that one third of the patients who develop t-MDS after an ASCT for lymphoma are cured after an allo-HSCT. The use of mismatched donors with standard graft-versus-host disease prophylaxis should be avoided in such an indication for allo-HSCT. It will be worthwhile to see if the implementation of cyclophosphamide post-transplantation will improve the outcome with mismatched donors.

Chronic Myelomonocytic Leukemia With Fibrosis Is a Distinct Disease Subset With Myeloproliferative Features and Frequent JAK2 p.V617F Mutations

A subset of patients with chronic myelomonocytic leukemia (CMML) presents with significance myelofibrosis. In myelodysplastic syndromes, significant myelofibrosis has been associated with adverse outcomes and p53 dysregulation. However, in CMML the clinical and molecular correlates of significant myelofibrosis at presentation remain poorly understood. From a cohort of 651 CMML patients, we identified retrospectively 20 (3.1%) cases with moderate to severe reticulin fibrosis (CMML-F) detected at diagnosis, and we compared them to CMML patients without fibrosis (n=631) seen during the same period. Patients with CMML-F had a median age of 69.8 years (range, 24.8 to 91.2 y) and most (13; 65%) were men. Patients with CMML-F differed significantly from other CMML patients across the following parameters: white blood count, absolute monocyte count, serum lactate dehydrogenase level, splenomegaly, and bone marrow blast percentage. Notably, the frequency of JAK2 p.V617F mutation was higher in CMML-F patients compared with other CMML patients (P<0.001). Most CMML-F patients (12/20; 60%) had myeloproliferative CMML. Dysregulation of p53 was uncommon in CMML-F. CMML-F patients tended to have a shorter median overall survival compared with other CMML patients (P=0.079). Multivariate analysis using the Cox proportional hazards model showed an independent association between CMML-F and overall survival (P=0.047). In summary, unlike typical CMML, CMML-F is commonly associated with JAK2 p.V617F. The high frequency of myeloproliferative features and JAK2 p.V617F mutation, and the low frequency of p53 dysregulation, suggest that fibrosis in the context of CMML has a different pathogenesis from that previously reported in myelodysplastic syndrome.

Treatment of myelodysplastic syndrome in the era of next-generation sequencing

Next-generation sequencing (NGS) is rapidly changing the clinical care of patients with myelodysplastic syndrome (MDS). NGS can be used for various applications: (i) in the diagnostic process to discriminate between MDS and other diseases such as aplastic anaemia, myeloproliferative disorders and idiopathic cytopenias; (ii) for classification, for example, where the presence of SF3B1 mutation is one criterion for the ring sideroblast anaemia subgroups in the World Health Organization 2016 classification; (iii) for identification of patients suitable for targeted therapy (e.g. IDH1/2 inhibitors); (iv) for prognostication, for example, where specific mutations (e.g. TP53 and RUNX1) are associated with inferior prognosis, whereas others (e.g. SF3B1) are associated with superior prognosis; and (v) to monitor patients for progression or treatment failure. Most commonly, targeted sequencing for genes (normally 50-100 genes) reported to be recurrently mutated in myeloid disease is used. At present, NGS is rarely incorporated into clinical guidelines although an increasing number of studies have demonstrated the benefit of using NGS in the clinical management of MDS patients.

Management of myelodysplastic syndromes after failure of response to hypomethylating agents

Hypomethylating agents (HMAs) are the standard of care for patients with myelodysplastic syndrome (MDS). However, only around 50% of patients respond to these agents, and responses tend to be transient, with loss of response frequently happening within 2 years and being associated with very poor prognosis and limited therapeutic options. Identification of patients who will respond to HMAs is challenging. Mechanisms underlying resistance to HMAs are not clear yet. Recently, absence of response has been associated with increased cell-cycle quiescence among the hematopoietic progenitor cells. There are no standard-of-care options for patients after HMA failure. However, the increasing knowledge of MDS pathogenesis has led to the development of new potential therapies, including HMAs with longer half-life and exposure, inhibition of the antiapoptotic BCL2 protein with venetoclax or inhibition of immune-checkpoint regulatory proteins such as PD-1 or CTLA-4, innate immunity and targeting of CD33/CD3 with multiple monoclonal antibodies. In addition, multiple targeted agents are opening opportunities to treat subgroups of patients whose disease harbors mutations in TP53, IDH, FLT3, and genes involved in splicing machinery. Newer formulations of intensive chemotherapy and its different combinations may be considered a valid option in selected patients after HMA failure. Finally, decision making at the time of failure of response to HMAs should be personalized, taking into account that allogenic stem-cell transplantation remains the only therapeutic approach with curative potential in these patients. In the current review, we will focus on all the above aspects.

Evaluation of induction chemotherapies after hypomethylating agent failure in myelodysplastic syndromes and acute myeloid leukemia

Hypomethylating agent (HMA) failure in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) carries a poor prognosis with limited treatment options. Although intensive, remission induction chemotherapy is often used subsequently, in particular to bridge to allogeneic transplantation, it is not clear whether an advantage exists for any particular regimen. Based on an international collaboration, we retrospectively analyzed induction response rate and survival in 366 patients after HMA failure. Patients received 7+3, intermediate- to high-dose cytarabine (IDAC), or purine nucleoside analog-based regimens. For the MDS cohort (n = 307), the overall response rate (ORR) was 41%; median overall survival (OS) was 10.8 months, and 40% of responding patients bridged to allogeneic stem cell transplant (allo-SCT). For the AML cohort (n = 59), the ORR was 32%, OS 6 months, and 42% of responding patients bridged to allo-SCT. Prognostic factors for response in MDS included adverse cytogenetics (odds ratio [OR], 0.46, P = .01), age ≥65 years (OR, 0.47; P < .01), and use of IDAC (OR, 2.91, P = .01). Shorter survival was associated with adverse cytogenetics (hazard ratio [HR], 1.43; P = .06). In the AML cohort, OS was decreased by disease progression at time of HMA failure (HR, 2.66; P = .02) and prolonged with use of an anthracycline-containing regimen (HR, 0.37; P = .01). In conclusion, intensive chemotherapy after HMA failure may be a reasonable treatment option for selected patients as a bridge to allogeneic transplantation and should be considered a potential platform for future investigations.

Therapeutic choices after hypomethylating agent resistance for myelodysplastic syndromes

PURPOSE OF REVIEW

Hypomethylating agents (HMAs) are the standard of care for patients with myelodysplastic syndromes (MDS). Although these agents induce responses in up to 40% of patients, most patients ultimately experience loss of response. The purpose of this review is to provide an overview of the different therapies under development for MDS after HMA therapy.

RECENT FINDINGS

Recent advances in the understanding of MDS pathogenesis have led to the development of new potential therapies after HMA failure. Newer HMAs, less susceptible to in-vivo deamination, such as guadecitabine or ASTX727 have shown activity. Alterations of immune checkpoints in MDS have led to multiple clinical trials evaluating the activity of monoclonal antibodies targeting these proteins (pembrolizumab, nivolumab, ipilimumab). Different combinations and new formulations of cytotoxic agents, such as clofarabine or CPX-351, are newer options for specific subsets of patients. Finally, targeted agents inhibiting multiple kinases (rigosertib), BCL2 (venetoclax) or mutant IDH1 (ivosidenib), IDH2 (enasidenib), FLT3 (sorafenib, midostaurin) or spliceosome components (H3B-8800) are other novel options.

SUMMARY

Despite the poor prognosis associated with HMA failure, clinical trials, new cytotoxic agents and allogeneic stem-cell transplantation, can offer therapeutic opportunities for these patients for whom there is no standard of care.

A phase II study of omacetaxine mepesuccinate for patients with higher-risk myelodysplastic syndrome and chronic myelomonocytic leukemia after failure of hypomethylating agents

The outcome of patients with myelodysplastic syndromes (MDSs) after failure of hypomethylating agents (HMAs) failure is poor with a median overall survival (OS) of only 4-6 months. Omacetaxine mepesuccinate (OM) is safe and effective in myeloid malignancies but has not been studied in MDS with HMA failure. We conducted a phase II study of OM in patients with MDS or chronic myelomonocytic leukemia (CMML) who had previously failed or been intolerant to HMAs. Patients received OM at a dose of 1.25 mg/m² subcutaneously every 12 hours for 3 consecutive days on a 4- to 7-week schedule. The primary endpoints were the overall response rate (ORR) and OS. A total of 42 patients were enrolled with a median age of 76 years. The ORR was 33%. Patients with diploid cytogenetics were more likely to respond to OM than were those with cytogenetic abnormalities (58% vs 23%, respectively; P = .03). Overall, the median OS was 7.5 months and 1-year OS rate was 25%. Patients with diploid cytogenetics had superior OS to those with cytogenetic abnormalities (median OS 14.8 vs 6.8 months, respectively; P = .01). Two patients had ongoing response to OM of 2 years or longer (both MDS with diploid cytogenetics and RUNX1 mutation). The most common grade ≥ 3 adverse events were infections in 11 patients (26%), febrile neutropenia in 4 (10%), and hemorrhage in 3 (7%). Overall, OM was safe and active in patients with MDS or CMML who experienced HMA failure. These results support the further development of OM in this setting.

How I treat MDS after hypomethylating agent failure

Hypomethylating agents (HMA) azacitidine and decitabine are standard of care for myelodysplastic syndrome (MDS). Response to these agents occurs in ∼50% of treated patients, and duration of response, although variable, is transient. Prediction of response to HMAs is possible with clinical and molecular parameters, but alternative approved treatments are not available, and in the case of HMA failure, there are no standard therapeutic opportunities. It is important to develop a reasoned choice of therapy after HMA failure. This choice should be based on evaluation of type of resistance (primary vs secondary, progression of disease [acute leukemia or higher risk MDS] vs absence of hematological improvement) as well as on molecular and cytogenetic characteristics reassessed at the moment of HMA failure. Rescue strategies may include stem-cell transplantation, which remains the only curative option, and chemotherapy, both of which are feasible in only a minority of cases, and experimental agents. Patients experiencing HMA failure should be recruited to clinical experimental trials as often as possible. Several novel agents with different mechanisms of action are currently being tested in this setting. Drugs targeting molecular alterations (IDH2 mutations, spliceosome gene mutations) or altered signaling pathways (BCL2 inhibitors) seem to be the most promising.

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.

Serotonin receptor type 1B constitutes a therapeutic target for MDS and CMML

Myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML) are chronic myeloid clonal neoplasms. To date, the only potentially curative therapy for these disorders remains allogeneic hematopoietic progenitor cell transplantation (HCT), although patient eligibility is limited due to high morbimortality associated with this procedure coupled with advanced age of most patients. Dopamine receptors (DRs) and serotonin receptors type 1 (HTR1s) were identified as cancer stem cell therapeutic targets in acute myeloid leukemia. Given their close pathophysiologic relationship, expression of HTR1s and DRs was interrogated in MDS and CMML. Both receptors were differentially expressed in patient samples compared to healthy donors. Treatment with HTR1B antagonists reduced cell viability. HTR1 antagonists showed a synergistic cytotoxic effect with currently approved hypomethylating agents in AML cells. Our results suggest that HTR1B constitutes a novel therapeutic target for MDS and CMML. Due to its druggability, the clinical development of new regimens based on this target is promising.

Myelodysplastic syndromes: 2018 update on diagnosis, risk-stratification and management

DISEASE OVERVIEW

The myelodysplastic syndromes (MDS) are a very heterogeneous group of myeloid disorders characterized by peripheral blood cytopenias and increased risk of transformation to acute myelogenous leukemia (AML). MDS occurs more frequently in older males and in individuals with prior exposure to cytotoxic therapy.

DIAGNOSIS

Diagnosis of MDS is based on morphological evidence of dysplasia upon visual examination of a bone marrow aspirate and biopsy. Information obtained from additional studies such as karyotype, flow cytometry or molecular genetics is usually complementary and may help refine diagnosis.

RISK-STRATIFICATION

Prognosis of patients with MDS can be calculated using a number of scoring systems. In general, all these scoring systems include analysis of peripheral cytopenias, percentage of blasts in the bone marrow and cytogenetic characteristics. The most commonly used system is probably the International Prognostic Scoring System (IPSS). IPSS is now replaced by the revised IPSS-R score. Although not systematically incorporated into new validated prognostic systems, somatic mutations can help define prognosis and should be considered as new prognostic factors.

RISK-ADAPTED THERAPY

Therapy is selected based on risk, transfusion needs, percent of bone marrow blasts and cytogenetic and mutational profiles. Goals of therapy are different in lower risk patients than in higher risk. In lower risk, the goal is to decrease transfusion needs and transformation to higher risk disease or AML, as well as to improve survival. In higher risk, the goal is to prolong survival. Current available therapies include growth factor support, lenalidomide, hypomethylating agents, intensive chemotherapy and allogeneic stem cell transplantation. The use of lenalidomide has significant clinical activity in patients with lower risk disease, anemia and a chromosome 5 alteration. 5-azacitidine and decitabine have activity in both lower and higher-risk MDS. 5-azacitidine has been shown to improve survival in higher risk MDS. A number of new molecular lesions have been described in MDS that may serve as new therapeutic targets or aid in the selection of currently available agents. Additional supportive care measures may include the use of prophylactic antibiotics and iron chelation.

MANAGEMENT OF PROGRESSIVE OR REFRACTORY DISEASE

At the present time there are no approved interventions for patients with progressive or refractory disease particularly after hypomethylating based therapy. Options include participation in a clinical trial or cytarabine based therapy and stem cell transplantation.

Hypomethylating agents (HMA) treatment for myelodysplastic syndromes: alternatives in the frontline and relapse settings

INTRODUCTION

Hypomethylating agents (HMA) have played a pivotal role for treating myelodysplastic syndromes (MDS) over the past decade, inducing sustained hematological responses and delaying progression to leukemia. However, a vast majority of patients will experience treatment failure within 2 years, with poor prognoses and limited options, and management of this growing patient population remains unclear. Areas covered: With the introduction of new agents in the MDS field, a better understanding of the biology of MDS, and updated information on standard of care options (including allogeneic transplantation), we re-evaluate the global treatment strategy in MDS via novel agents, focusing in particular on investigational approaches for patients who fail to respond to HMA when applicable. This review aims to address two questions: what are reasonable alternatives to HMA in MDS, and what strategies can be used for patients experiencing HMA failure. Expert opinion/commentary: HMA therapy remains a mainstay of treatment, even if additional research is still warranted to maximize its benefits for the different groups of patients. The outcome of patients experiencing HMA failure remains grim, without standard of care, but several new approaches seem promising, as there is an increasing focus on studying treatments for patients refractory to HMA treatment.