Subcutaneous alemtuzumab plus cyclosporine for the treatment of aplastic anemia

Autoimmune pathogenesis, immunosuppressive therapy and pharmacological mechanism in aplastic anemia

Acquired aplastic anemia (AA) is an autoimmune disease of bone marrow failure mediated by abnormally activated T cells, manifested by severe depletion of hematopoietic stem and progenitor cells (HSPCs) and peripheral blood cells. Due to the limitation of donors for hematopoietic stem cell transplantation, immunosuppressive therapy (IST) is currently an effective first-line treatment. However, a significant proportion of AA patients remain ineligible for IST, relapse, and develop other hematologic malignancies, such as acute myeloid leukemia after IST. Therefore, it is important to elucidate the pathogenic mechanisms of AA and to identify treatable molecular targets, which is an attractive way to improve these outcomes. In this review, we summarize the immune-related pathogenesis of AA, pharmacological targets, and clinical effects of the current mainstream immunosuppressive agents. It provides new insight into the combination of immunosuppressive drugs with multiple targets, as well as the discovery of new druggable targets based on current intervention pathways.

New Trends of Nontransplant therapy for Acquired Aplastic Anemia

Aplastic anemia (AA) is a hematological disease that is characterized by pancytopenia and hypofunctional bone marrow hematopoiesis. Patients with AA are treated with either immunosuppressive therapy (IST) using anti-thymocyte globulin (ATG) and Cyclosporine (CsA) or hematopoietic stem cell transplantation (HSCT), if a matched donor is available. The standard IST regimen for AA patients which results in response rates up to 70%, and even higher overall survival. However, primary and secondary failures after IST remain frequent, and to date all attempts aiming to overcome this problem have been unfruitful. The nontransplant therapeutic options for AA have significantly expanded during the last few years. Here, we review the new trends of nontransplant therapy for AA and summarize the current therapeutic effect of AA.

Evaluation of efficacy of alemtuzumab in 5 patients with aplastic anemia and/or myelodysplastic neoplasm

Patients with aplastic anemia or hypoplastic myelodysplastic syndrome (MDS) may respond to immunosuppressive therapy, including the anti-CD52 antibody alemtuzumab. We analyzed treatment responses to alemtuzumab in 5 patients with MDS or aplastic anemia (AA) evolving to MDS. Two patients with hypoplastic MDS (hMDS) showed a partial response (PR) to alemtuzumab. In both responding patients, a concomitant paroxysmal nocturnal hemoglobinuria (PNH) clone was detected before therapy. One responder relapsed after 15 months and underwent successful allogeneic stem cell transplantation. Both patients are still alive and in remission after 40 and 20 months, respectively. The other patients showed no response to alemtuzumab. One patient died from pneumonia 4 months after treatment. In summary, our data confirm that alemtuzumab is an effective treatment option for a subset of patients with MDS, even in the presence of a PNH clone.

Immunosuppressive therapy for transplant-ineligible aplastic anemia patients

Aplastic anemia is a rare life-threatening bone marrow failure that is characterized by bicytopenia or pancytopenia in the peripheral blood and a hypoplastic or aplastic bone marrow. The patients are at risk of infection and hemorrhage due to neutropenia and thrombocytopenia and suffer from symptoms of anemia. The main treatment approaches are allogeneic stem cell transplantation and immunosuppression. Here, we review current standard immunosuppression and the attempts that have been made in the past two decades to improve results: review of recent developments also reveals that sometimes not only the advent of new drugs, good ideas and well-designed clinical trials decide the progress in the field but also marketing considerations of pharmaceutical companies. Aplastic anemia experts unfortunately had to face the situation that efficient drugs were withdrawn simply for marketing considerations. We will discuss the current options and challenges in first-line treatment and management of relapsing and refractory patients with an emphasis on adult patients. Some promising new approaches are currently under investigation in prospective, randomized trials.

Recent Developments in Drug Therapy for Aplastic Anemia

Objective: This article reviews recent developments in immunosuppressive therapy (IST) for aplastic anemia (AA) patients who are not candidates for stem cell transplant (SCT); including, front-line, salvage, and novel treatment options with a focus on response rates (RRs) and overall survival (OS). Data Sources: A PubMed literature search was performed from 1977 to June 2014 using the search terms aplastic anemia, horse antithymocyte globulin (hATG), rabbit ATG (rATG), thymoglobulin, and cyclosporine (CSA). Additional references were identified from a review of literature citations. Study Selection and Data Extraction: All English-language studies investigating IST for treatment of AA in non–SCT candidates were evaluated. Data Synthesis: Studies indicate addition of CSA and corticosteroids to hATG for treatment of AA improves RRs, decreases relapse rates, and improves 5-year OS. hATG improved RRs, relapse rates, and OS compared to rATG in the front-line setting. Studies support the use of rATG when front-line IST with hATG fails or when hATG is unavailable. Front-line daclizumab can be considered for nonsevere AA (NAA); however, data is limited. Alemtuzumab or eltrombopag are options for relapsed AA in select patients. Conclusions: hATG with methylprednisolone and CSA is recommended for front-line treatment of AA, whereas rATG is reserved for salvage therapy. Front-line use of daclizumab has been studied in NAA patients, but additional prospective trials are needed before this is adopted into clinical practice. Alemtuzumab and eltrombopag have been studied for treatment of AA; recruiting is ongoing in clinical trials to assess the appropriate dosing strategy and place in therapy.

Alternative immunosuppression in patients failing immunosuppression with ATG who are not transplant candidates: Campath (Alemtuzumab)

Antithymocyte globulin (ATG)-based immunosuppression remains the standard immunosuppressive therapy (IST) for aplastic anemia (AA) patients lacking a sibling donor; however, treatment failures are relatively frequent, including about one-quarter to one-third of patients who do not show any response to initial IST, and about half of the initial responders who may experience subsequent relapses or require continuous maintenance IST. For these patients, there is the option of further IST, which may include additional courses of ATG-based IST, or attempts with alternative IST regimens. Alemtuzumab is a monoclonal anti-CD52 Ab, which has been recently investigated as novel IS agent for the treatment of AA patients. Recent data from different groups have clearly demonstrated the biological efficacy of Alemtuzumab in AA patients, ruling out the initial concerns about possible unacceptable infectious risks secondary to its extremely powerful lympholytic effect. Preliminary data demonstrate a remarkable efficacy, especially in the context of relapsed and, to less extent, refractory patients, whereas data in naïve patients are still limited. On the basis of these results, Alemtuzumab-based immunosuppression is a worthy option for AA and other marrow failure patients requiring a second-line IST. Here we describe a consensus regimen that the European Group for Blood and Marrow Transplantation Severe Aplastic Anemia Working Party suggests for AA patients failing initial IST who are not indicated for SCT.

Aplastic anemia: therapeutic updates in immunosuppression and transplantation

Advances in hematopoietic stem cell transplantation (HSCT) and immunosuppressive therapy (IST) have improved survival in severe aplastic anemia (SAA) from 10%-20% in the 1960s to 80%-90% today. A matched sibling HSCT is the treatment of choice in younger patients, whereas IST is often used in older patients or in those who lack a histocompatible sibling. Graft rejection, GVHD, and poor immune reconstitution (with associated infectious complications) limit the success of HSCT, whereas lack of response, relapse, and clonal evolution limit the success of IST. The historically high rate of graft rejection in SAA is now less problematic in the matched setting, but with greater rates observed with unrelated and umbilical cord donors. The correlation of increasing age with the risk of GVHD and the significant morbidity and mortality of this transplantation complication continue to affect the decision to pursue HSCT versus IST as initial therapy in adults with SAA. Outcomes with matched unrelated donor HSCT have improved, likely due to better donor selection, supportive care, and improved transplantation protocols. Results with mismatched unrelated donor and umbilical HSCT are not as favorable, with higher rates of graft rejection, GVHD, and infectious complications. Investigation of several upfront alternative IST protocols has not improved outcomes beyond horse antithymocyte globulin and cyclosporine. More recently, the role of alemtuzumab in SAA has been better defined and an oral thrombomimetic, eltrombopag, is showing promising activity in refractory cases. The most recent advances in HSCT and IST in SAA are discussed in this review.

Prospective study of rabbit antithymocyte globulin and cyclosporine for aplastic anemia from the EBMT Severe Aplastic Anaemia Working Party

Rabbit antithymocyte globulin (rATG; thymoglobulin, Genzyme) in combination with cyclosporine, as first-line immunosuppressive therapy, was evaluated prospectively in a multicenter, European, phase 2 pilot study, in 35 patients with aplastic anemia. Results were compared with 105 age- and disease severity–matched patients from the European Blood and Marrow Transplant registry, treated with horse ATG (hATG; lymphoglobulin) and cyclosporine. The primary end point was response at 6 months. At 3 months, no patients had achieved a complete response to rATG. Partial response occurred in 11 (34%). At 6 months, complete response rate was 3% and partial response rate 37%. There were 10 deaths after rATG (28.5%) and 1 after subsequent HSCT. Infections were the main cause of death in 9 of 10 patients. The best response rate was 60% for rATG and 67% for hATG. For rATG, overall survival at 2 years was 68%, compared with 86% for hATG (P = .009). Transplant-free survival was 52% for rATG and 76% for hATG (P = .002). On multivariate analysis, rATG (hazard ratio = 3.9, P = .003) and age more than 37 years (hazard ratio = 4.7, P = .0008) were independent adverse risk factors for survival. This study was registered at www.clinicaltrials.gov as NCT00471848.

Antibodies in the treatment of aplastic anemia

Antibodies have been the cornerstone of treatment of acquired aplastic anemia for more than 25 years. Treatment with antithymocyte globulin (ATG) is considered pivotal and the addition of cyclosporine improves the overall response rate. This antibody is heterogeneous and horse ATG is apparently more effective than rabbit ATG. Several issues remain unsolved in relation to the combination of ATG and cyclosporine: cost, toxicity and late clonal disorders. In recent years, alternative immunosuppressive therapy has been proposed and new antibodies have emerged: porcine ATG, alemtuzumab, daclizumab, and rituximab. Experience with these antibodies is limited to a few studies with alemtuzumab being the most promising, but the results are interesting and provocative. More studies are needed to find the perfect antibody.

Immunosuppressive therapies in the management of acquired immune-mediated marrow failures

PURPOSE OF REVIEW

Immunosuppression is a key treatment strategy for patients suffering from aplastic anemia or related immune-mediated bone marrow failure syndromes. Several attempts have been performed to improve the standard immunosuppression regimen of horse antithymocyte globulin (h-ATG) and cyclosporine A (CyA).

RECENT FINDINGS

The addition of a third immunosuppression agent to h-ATG + CyA did not result in any improvement. Antilymphocyte agents other than h-ATG have been investigated. A rabbit-ATG preparation, which was known to be more immunosuppressive than h-ATG, resulted in markedly inferior outcome in a large randomized study from the National Institutes of Health. These data seem to be confirmed in additional experiences with rabbit-ATG from other groups. Cyclophosphamide and alemtuzumab have been proven to be biologically active in small studies, but available data suggest inferior outcomes when compared with h-ATG. All these alternative agents result in a more pronounced lymphocyte depletion, suggesting that the actual mechanisms of action of immunosuppressive therapy in aplastic anemia are not fully understood.

SUMMARY

Immunosuppression by h-ATG and CyA remains the standard of care for aplastic anemia patients lacking a low-risk transplant procedure, resulting in a 60-70% response rate. Rabbit-ATG, cyclophosphamide and alemtuzumab demonstrated a biological activity, but resulted in inferior outcome as compared with h-ATG; thus, they are not recommended as front-line therapy of aplastic anemia.

Activity of alemtuzumab monotherapy in treatment-naive, relapsed, and refractory severe acquired aplastic anemia

Antithymocyte globulin (ATG) + cyclosporine is effective in restoring hematopoiesis in severe aplastic anemia (SAA). We hypothesized that the humanized anti-CD52 mAb alemtuzumab might be active in SAA because of its lymphocytotoxic properties. We investigated alemtuzumab monotherapy from 2003-2010 in treatment-naive, relapsed, and refractory SAA in 3 separate research protocols at the National Institutes of Health. Primary outcome was hematologic response at 6 months. For refractory disease, patients were randomized between rabbit ATG + cyclosporine (n = 27) and alemtuzumab (n = 27); the response rate for alemtuzumab was 37% (95% confidence interval [CI], 18%-57%) and for rabbit ATG 33% (95% CI, 14%-52%; P = .78). The 3-year survival was 83% (95% CI, 68%-99%) for alemtuzumab and 60% (95% CI, 43%-85%) for rabbit ATG (P = .16). For relapsed disease (n = 25), alemtuzumab was administered in a single-arm study; the response rate was 56% (95% CI, 35%-77%) and the 3-year survival was 86% (95% CI, 72%-100%). In treatment-naive patients (n = 16), alemtuzumab was compared with horse and rabbit ATG in a 3-arm randomized study; the response rate was 19% (95% CI 0%-40%), and the alemtuzumab arm was discontinued early. We conclude that alemtuzumab is effective in SAA, but best results are obtained in the relapsed and refractory settings. The present trials were registered at www.clinicaltrials.gov as NCT00195624, NCT00260689, and NCT00065260.

Aplastic anemia: immunosuppressive therapy in 2010

Acquired aplastic anemia (AA) is the typical bone marrow failure syndrome characterized by an empty bone marrow; an immune-mediated pathophysiology has been demonstrated by experimental works as well as by clinical observations. Immunusuppressive therapy (IST) is a key treatment strategy for aplastic anemia; since 20 years the standard IST for AA patients has been anti-thymocyte globuline (ATG) plus cyclosporine A (CyA), which results in response rates ranging between 50% and 70%, and even higher overall survival. However, primary and secondary failures after IST remain frequent, and to date all attempts aiming to overcome this problem have been unfruitful. Here we review the state of the art of IST for AA in 2010, focusing on possible strategies to improve current treatments. We also discuss very recent data which question the equality of different ATG preparations, leading to a possible reconsideration of the current standards of care for AA patients.

Immunosuppressive therapies in the management of immune-mediated marrow failures in adults: where we stand and where we are going

Immunosuppression is a key treatment strategy for aplastic anaemia (AA) and the related immune-mediated bone marrow failure syndromes (BMFS). For the last 20 years the standard immunosuppressive regimen for AA patients has been anti-thymocyte globulin (ATG) plus ciclosporin A (CyA), which results in response rates ranging between 50% and 70%, and even higher overall survival. However, primary and secondary failures after immunosuppressive therapy remain frequent, and to date all attempts aiming to overcome this problem have been unfruitful. This article reviews the state of the art of current immunosuppressive therapies for AA, focusing on open questions linked to standard immunosuppressive treatment, and on experimental immunosuppressive strategies which could lead to future improvement of current treatments. Specific immunosuppressive strategies employed for other BMFS, such as lineage-restricted marrow failures, myelodysplastic syndromes and large granular lymphocyte leukaemia-associated cytopenias, are also briefly discussed.

Low-dose rituximab and alemtuzumab combination therapy for patients with steroid-refractory autoimmune cytopenias

Treatment of autoimmune cytopenias remains unsatisfactory for patients refractory to first-line management. We evaluated the safety and efficacy of low-dose rituximab plus alemtuzumab in patients with steroid-refractory autoimmune hemolytic anemia and immune thrombocytopenic purpura. Nineteen of 21 included patients were assessable for response (11 with immune thrombocytopenic purpura, 8 with autoimmune hemolytic anemia). Treatment with 10 mg of alemtuzumab subcutaneously on days 1 to 3, plus 100 mg of rituximab intravenously weekly in 4 doses, was administered. The overall response rate was 100%, with complete response in 58%. The median response duration was 46 weeks (range, 16-89 weeks). Median follow-up was 70 weeks (range, 37-104 weeks). Most toxicity was grade 1 fever related to the first dose. Six patients developed infections. The combination of rituximab and alemtuzumab is feasible and has an acceptable safety profile and remarkable clinical activity in this group of patients. This study is registered at www.clinicaltrials.gov as #NCT00749112.