In vivo CAMPATH-1H prevents GvHD following nonmyeloablative stem-cell transplantation

Effect of alemtuzumab-based T-cell depletion on graft compositional change in vitro and immune reconstitution early after allogeneic stem cell transplantation

BACKGROUND AIMS

To reduce the risk of graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (alloSCT), T-cell depletion (TCD) of grafts can be performed by the addition of alemtuzumab (ALT) "to the bag" (in vitro) before transplantation. In this prospective study, the authors analyzed the effect of in vitro incubation with 20 mg ALT on the composition of grafts prior to graft infusion. Furthermore, the authors assessed whether graft composition at the moment of infusion was predictive for T-cell reconstitution and development of GVHD early after TCD alloSCT.

METHODS

Sixty granulocyte colony-stimulating factor-mobilized stem cell grafts were obtained from ≥9/10 HLA-matched related and unrelated donors. The composition of the grafts was analyzed by flow cytometry before and after in vitro incubation with ALT. T-cell reconstitution and incidence of severe GVHD were monitored until 12 weeks after transplantation.

RESULTS

In vitro incubation of grafts with 20 mg ALT resulted in an initial median depletion efficiency of T-cell receptor (TCR) α/β T cells of 96.7% (range, 63.5-99.8%), followed by subsequent depletion in vivo. Graft volumes and absolute leukocyte counts of grafts before the addition of ALT were not predictive for the efficiency of TCR α/β T-cell depletion. CD4^pos T cells were depleted more efficiently than CD8^pos T cells, and naive and regulatory T cells were depleted more efficiently than memory and effector T cells. This differential depletion of T-cell subsets was in line with their reported differential CD52 expression. In vitro depletion efficiencies and absolute numbers of (naive) TCR α/β T cells in the grafts after ALT incubation were not predictive for T-cell reconstitution or development of GVHD post- alloSCT.

CONCLUSIONS

The addition of ALT to the bag is an easy, fast and generally applicable strategy to prevent GVHD in patients receiving alloSCT after myeloablative or non-myeloablative conditioning because of the efficient differential depletion of donor-derived lymphocytes and T cells.

Non-myeloablative matched sibling stem cell transplantation with the optional reinforced stem cell infusion for patients with hemoglobinopathies

BACKGROUND

The NIH protocol for non-myeloablative (NMA) conditioning allogeneic stem cell transplantation (alloSCT) with alemtuzumab and low-dose total body irradiation corrected the abnormal sickle cell disease (SCD) phenotype without the risk of graft-versus-host disease. However, alloSCT using NMA conditioning had been rarely applied to β-thalassemia major (β-TM) patients.

METHODS

To avoid prolonged immunosuppression, we developed a two-stage strategy. Mixed donor chimerism was initially achieved using the protocol developed by the NIH protocol. Thereafter, we facilitated donor chimerism using the optional reinforced stem cell (SC) infusion in cases requiring protracted immunosuppression or experiencing impending graft failure.

RESULTS

In this study, β-TM (n = 9) and SCD (n = 4) patients were equally effectively treated with eradicating the abnormal hemoglobin phenotype. Five patients, including four β-TM, achieved stable mixed chimerism without receiving optional reinforced SC infusion. All patients that received optional reinforced infusion achieved complete (n = 4) or mixed chimerism (n = 1). The overall survival rate and event-free survival at 4 years were 91.7% (95% CI; 53.9-98.8) in both groups, with a thalassemia-free survival rate in β-TM patients of 87.5% (95% CI; 38.7-98.1).

CONCLUSION

This study is the first to report successful NMA conditioning alloSCT to achieve stable mixed chimerism correcting the abnormal hemoglobin phenotype in adult β-TM patients.

Invasive fungal disease is associated with chronic graft-versus-host disease after allogeneic hematopoietic stem cell transplant: a single center, retrospective study

BACKGROUND

Invasive fungal disease (IFD) and graft-versus-host disease (GVHD) are major causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the impacts of IFD on chronic GVHD remain unknown.

METHODS

We conducted a retrospective study of 510 patients with hematologic malignancy undergoing allo-HSCT to explore the effects of IFD on chronic GVHD.

RESULTS

The 2-year cumulative incidences of overall (limited and extensive) and extensive chronic GVHD post-transplantation were higher in patients with IFD compared with those without IFD (69.5% ± 4.2% versus 32.9% ± 2.4%, P < .001; 43.0% ± 5.2% versus 6.6% ± 1.4%, P < .001, respectively). Moreover, the patients with IFD had higher 5-year transplant-related mortality, lower 5-year overall survival and lower 5-year disease-free survival (29.8% ± 4.3% versus 9.8% ± 1.6%, P < .001; 50.5% ± 4.9% versus 71.3% ± 2.4%, P < .001 and 48.8% ± 4.7% versus 71.8% ± 2.3%, P < .001, respectively). Multivariable analyses demonstrated that IFD increased the risk of chronic GVHD.

CONCLUSION

Our results suggest that IFD significantly contributes to the development of chronic GVHD after allo-HSCT.

Clinical pharmacology of alemtuzumab, an anti-CD52 immunomodulator, in multiple sclerosis

Alemtuzumab, a humanized anti‐CD52 monoclonal antibody, is approved for treatment of relapsing multiple sclerosis (MS). In the Phase II/III trials, patients received 12 or 24 mg/day of alemtuzumab in two treatment courses (5 days for course 1 and 3 days for course 2), 12 months apart. Serum concentrations of alemtuzumab peaked on the last day of dosing in each course and mostly fell below the limit of quantitation by day 30. Alemtuzumab rapidly depleted circulating T and B lymphocytes, with the lowest observed values occurring within days. Lymphocytes repopulated over time, with B cell recovery usually complete within 6 months. T lymphocytes recovered more slowly and generally did not return to baseline by 12 months post‐treatment. Approximately 40 and 80% of patients had total lymphocyte counts, reaching the lower limit of normal by 6 and 12 months after each course, respectively. The clearance of alemtuzumab is dependent on circulating lymphocyte count. A majority of treated patients tested positive for anti‐alemtuzumab antibodies, including inhibitory antibodies, during the 2‐year studies, and a higher proportion of patients tested positive in course 2 than in course 1. The presence of anti‐alemtuzumab antibody appeared to be associated with slower clearance of alemtuzumab from the circulation but had no impact on the pharmacodynamics. No effects of age, race or gender on the pharmacokinetics or pharmacodynamics were observed. Together, the pharmacokinetics, pharmacodynamics and immunogenicity results support the continued development and use of alemtuzumab for the treatment of MS, and probably explain its sustained effects beyond the dosing interval.

Predicting CD4 T-Cell Reconstitution Following Pediatric Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is an increasingly common treatment for children with a range of hematological disorders. Conditioning with cytotoxic chemotherapy and total body irradiation leaves patients severely immunocompromised. T‐cell reconstitution can take several years due to delayed restoration of thymic output. Understanding T‐cell reconstitution in children is complicated by normal immune system maturation, heterogeneous diagnoses, and sparse uneven sampling due to the long time spans involved. We describe here a mechanistic mathematical model for CD4 T‐cell immune reconstitution following pediatric transplantation. Including relevant biology and using mixed‐effects modeling allowed the factors affecting reconstitution to be identified. Bayesian predictions for the long‐term reconstitution trajectories of individual children were then obtained using early post‐transplant data. The model was developed using data from 288 children; its predictive ability validated on data from a further 75 children, with long‐term reconstitution predicted accurately in 81% of the patients.

Impact of pre-transplant co-morbidities on outcome after alemtuzumab-based reduced intensity conditioning allo-SCT in elderly patients: a British Society of Blood and Marrow Transplantation study

The advent of reduced intensity conditioning (RIC) regimens has permitted the extension of allo-SCT to selected patients into their eighth decade but GVHD remains a major cause of morbidity and mortality. Alemtuzumab is increasingly used to reduce the risk of severe GVHD, but there are concerns that T-cell depletion may compromise outcome particularly in older patients. We therefore studied the impact of pre-transplant factors on the outcome of 187 patients with a haematological malignancy over the age of 60 transplanted using an alemtuzumab-based RIC regimen of whom co-morbidity scoring was possible in 169. Of the patients, 120 had a haematopoietic cell transplantation co-morbidity index (HCT-CI) of 0 or 1 and 49 had a score of 2 or more. The 5-year OS was 33%. In multivariable analysis, OS was determined by co-morbidity score (P=0.001) and disease status at transplant (P=0.004) but not by patient age. Non-relapse mortality was determined by co-morbidity score (P=0.001). Two-year OS for patients with a HCT-CI of 0-1 was 59 versus 6% for patients with a higher score. Alemtuzumab-based RIC allografts can be delivered safely in patients aged over 60 but co-morbidity scoring is mandatory to identify patients who will benefit.

Complications of allogeneic hematopoietic stem cell transplantation

Infection, graft-versus-host disease (GVHD), and to a lesser extent sinusoidal obstructive syndrome (SOS) represent the major causes of morbidity and mortality in patients undergoing allogeneic hematopoietic stem cell transplantation (AHSCT). During the last decade, progress in prevention and treatment of these complications led to improvement in the outcome of these patients. Despite the fact that nonmyeloablative regimens have been increasingly used in elderly patients and in patients with co-morbidities, the nonrelapse related mortality remains a challenge and long-term follow-up is required. The objective of this manuscript is to provide an updated concise review of the complications of AHSCT and of the available treatment interventions.

A review of Campath in autoimmune disease: Biologic therapy in the gray zone between immunosuppression and immunoablation

Campath, the subject of this review, is an example of a broadly targeted biologic agent, approved for patients with B-CLL, which may combine immunosuppressive as well as immunoablative properties. For many years Campath has been in clinical use as an immunosuppressive agent for various autoimmune diseases and as part of the preparative regimes for allogeneic HSCT, successfully preventing graft-versus-host-disease (GVHD). This review summarizes the experience of 24 studies including a total of 323 patients treated with Campath for various autoimmune diseases such as arthritis, MS, vasculitis, autoimmune cytopenias and others. The results demonstrate that Campath is fairly safe and 75% of the patients experienced clinical improvement and 15% of the patients were reported in clinical remission even though improvements were often transient.While other biologic drugs may have to narrow targets, Campath, is able to bridge the gap between immunosuppression and immunoablation and may offer an alternative to human stem cell transplantation avoiding the risks of chemotherapy and radiation.

Pretransplant conditioning with Campath-1H (alemtuzumab) in pediatric matched unrelated hematopoietic stem cell transplants: an institutional experience

Graft versus host disease (GVHD) remains a major cause of mortality and morbidity after matched unrelated hematopoietic stem cell transplantation (HSCT). Campath-1 H (alemtuzumab), a humanized monoclonal antibody to CD52 antigen, is thought to reduce GVHD incidence through in vivo T-cell depletion. Through the same mechanism it can potentially increase the risk of relapse by reducing the graft versus leukemia effect and possibly increase the risk of infection due to delayed immune recovery. A retrospective case analysis of 17 pediatric matched unrelated HSCTs done in our institution between January 2003 and June 2009 with Campath-1H as part of the pretransplant conditioning regimen was conducted. Grade I-II acute GVHD was noted in 29.4% of the HSCTs. No patient developed chronic GVHD. All but one patient with severe aplastic anemia engrafted. A relapse of primary disease was noted in 35.3% of the transplants. Three patient deaths were due to relapse and 1 due to disseminated varicella infection. Overall survival was 100% and 94% at 100 days and 1 year, respectively. Our experience suggests Campath-1H used as part of pretransplant conditioning regimen in pediatric unrelated HSCTs effectively reduces the risk of serious GVHD with no apparent increase in life-threatening infections or relapse compared with that reported with conventional regimens. Larger studies, with longer duration of follow-up, are required to further assess its role with regards to graft versus leukemia effect and to establish if the decreased incidence of GVHD and infectious complications is sustained in larger cohorts.

[Alemtuzumab: a further option for treatment of multiple sclerosis]

Alemtuzumab is a humanized monoclonal therapeutic antibody that targets the CD52 antigen which s expressed on most cells of the lymphoid lineage, exclusive of precursors. Alemtuzumab rapidly depletes CD52(+) cells from the peripheral blood. This depletion is long-lasting, and cells repopulate in a specific pattern with B cells and regulatory T cells peaking first. Alemtuzumab was examined for clinical utility in two open-labelled intervention trials in multiple sclerosis (MS). Because of very promising results its clinical efficacy was further explored in a clinical phase-II trial using s.c. interferon beta-1a as the active comparator. Severe or opportunistic infections were surprisingly rare given the long-term lymphopenia. However, up to 30% of patients developed some antibody-mediated autoimmunity. The thyroid gland was the most frequently affected organ. Immune-mediated thrombocytopenic purpura and Goodpasture's syndrome were additionally observed. This review summarizes the pre-clinical and clinical development of alemtuzumab and discusses potential modes of action as well as the pathogenetic link to the treatment emergent autoimmune phenomena.

Therapeutic implications of variable expression of CD52 on clonal cytotoxic T cells in CD8+ large granular lymphocyte leukemia

BACKGROUND

T-cell large granular lymphocytic leukemia is a clonal proliferation of cytotoxic T-lymphocytes which often results in severe cytopenia. Current treatment options favor chronic immunosuppression. Alemtuzumab, a humanized monoclonal antibody against glycophosphatidylinositol-anchored CD52, is approved for patients refractory to therapy in other lymphoid malignancies.

DESIGN AND METHODS

We retrospectively examined treatment outcomes in 59 patients with CD8+ T-cell large granular lymphocytic leukemia, 41 of whom required therapy. Eight patients with severe refractory cytopenia despite multiple treatment regimens had been treated with subcutaneous alemtuzumab as salvage therapy. Flow cytometry was used to monitor expression of glycophosphatidylinositol-anchored CD52, CD55, and CD59 as well as to characterize T-cell clonal expansions by T-cell receptor variable beta-chain (Vbeta) repertoire.

RESULTS

Analysis of the effects of alemtuzumab revealed remissions with restoration of platelets in one of one patient, red blood cell transfusion independence in three of five patients and improvement of neutropenia in one of three, resulting in an overall response rate of 50% (4/8 patients). Clonal large granular lymphocytes exhibited decreased CD52 expression post-therapy in patients refractory to treatment. Samples of large granular lymphocytes collected prior to therapy also unexpectedly had a significant proportion of CD52-negative cells while a healthy control population had no such CD52 deficiency (p=0.026).

CONCLUSIONS

While alemtuzumab may be highly effective in large granular lymphocytic leukemia, prospective serial monitoring for the presence of CD52-deficient clonal cytotoxic T-lymphocytes should be a component of clinical trials investigating the efficacy of this drug. CD52 deficiency may explain lack of response to alemtuzumab, and such therapy may confer a survival advantage to glycophosphatidylinositol-negative clonal cytotoxic T-lymphocytes.

T-cell-depleted allogeneic transplant without donor leukocyte infusions results in excellent long-term survival in patients with multiply relapsed Lymphoma. Predictors for survival after transplant relapse

We analyzed 67 patients with lymphoma who received alemtuzumab-based conditioning regimens for allogeneic stem cell transplant and no post-transplant DLI. The median age was 54 (24-70), 43% had unrelated donors, 34% had chemotherapy refractory disease, and 25% had an elevated LDH. With a median follow-up for survivors of 35 months, the estimated 3-year progression-free survival (PFS) and overall survival (OS) were 30% and 47%, respectively. Chemosensitivity by CT and pre-transplant LDH were independent prognostic factors for both overall survival and progression-free survival. Patient age, performance status, donor type, lymphoma subtype, disease sensitivity by PET, and conditioning regimen did not correlate with PFS and OS. Patients who relapsed greater than 6 months after allogeneic transplant were frequently able to re-enter a subsequent durable remission. Our experience confirms the curative potential of alemtuzumab-containing RIC regimens for allogeneic HCT in patients with relapsed lymphoma without prophylactic DLI. An elevated pre-transplant LDH and chemorefractory disease prior to transplant confer a worse prognosis, while PET scan findings do not have this same implication. Patients who relapse greater than 6 months after their transplant are likely to achieve a subsequent remission with any of a variety of interventions, suggesting that GVL effects can be operative even after recurrence. Our outcomes challenge the utility of the common practice of prophylactic DLI after T-depleted transplant for lymphoma.

Antithymocyte globulins and chronic graft-vs-host disease after myeloablative allogeneic stem cell transplantation from HLA-matched unrelated donors: a report from the Sociéte Française de Greffe de Moelle et de Thérapie Cellulaire

This retrospective report assessed the impact of rabbit antithymocyte globulins (ATG), incorporated within a standard myeloablative conditioning regimen prior to allogeneic stem cell transplantation (allo-SCT) using human leukocyte antigen-matched unrelated donors (HLA-MUD), on the incidence of acute and chronic graft-vs-host disease (GVHD). In this series of leukemia patients, 120 patients (70%) did not receive ATG ('no-ATG' group), whereas 51 patients received ATG ('ATG' group). With a median follow-up of 30.3 months, the cumulative incidence of grade 3-4 acute GVHD was 36% in the no-ATG group and 20% in the ATG group (P = 0.11). The cumulative incidence of extensive chronic GVHD was significantly lower in the ATG group as compared to the no-ATG group (4 vs 32%, respectively; P = 0.0017). In multivariate analysis, the absence of use of ATG was the strongest parameter associated with an increased risk of extensive chronic GVHD (relative risk) = 7.14, 95% CI: 1.7-33.3, P = 0.008). At 2 years, the probability of nonrelapse mortality, relapse, overall and leukemia-free survivals was not significantly different between the no-ATG and ATG groups. We conclude that the addition of ATG to GVHD prophylaxis resulted in decreased incidence of extensive chronic GVHD without an increase in relapse or nonrelapse mortality, and without compromising survival after myeloablative allo-SCT from HLA-MUD.

Factors predicting long-term survival after T-cell depleted reduced intensity allogeneic stem cell transplantation for acute myeloid leukemia

BACKGROUND

Reduced intensity conditioning regimens permit the delivery of a potentially curative graft-versus-leukemia effect in older patients with acute myeloid leukemia. Although T-cell depletion is increasingly used to reduce the risk of graft-versus-host disease its impact on the graft-versus-leukemia effect and long-term outcome post-transplant is unknown.

DESIGN AND METHODS

We have characterized pre- and post-transplant factors determining overall survival in 168 patients with acute myeloid leukemia transplanted using an alemtuzumab based reduced intensity conditioning regimen with a median duration of follow-up of 37 months.

RESULTS

The 3-year overall survival for patients transplanted in CR1 or CR2/CR3 was 50% (95% CI, 38% to 62%) and 44% (95% CI, 31% to 56%), respectively compared to 15% (95% CI, 2% to 36%) for patients with relapsed/refractory disease. Multivariate analysis demonstrated that both survival and disease relapse were influenced by status at transplant (P=0.008) and presentation cytogenetics (P=0.01). Increased exposure to cyclosporine A (CsA) in the first 21 days post-transplant was associated with an increased relapse risk (P<0.0001) and decreased overall survival (P<0.0001).

CONCLUSIONS

Disease stage, presentation karyotype and post-transplant CsA exposure are important predictors of outcome in patients undergoing a T-cell depleted reduced intensity conditioning allograft for acute myeloid leukemia. These data confirm the presence of a potent graft-versus-leukemia effect after a T-cell depleted reduced intensity conditioning allograft in acute myeloid leukemia and identify CsA exposure as a manipulable determinant of outcome in this setting.

Favorable outcomes with alemtuzumab-conditioned unrelated donor stem cell transplantation in adults with high-risk Philadelphia chromosome-negative acute lymphoblastic leukemia in first complete remission

BACKGROUND

Approximately 40% of adults with Philadelphia chromosome-negative acute lymphoblastic leukemia achieve long-term survival following unrelated donor hematopoietic stem cell transplantation in first complete remission but severe graft-versus-host disease remains a problem affecting survival. Although T-cell depletion abrogates graft-versus-host disease, the impact on disease-free survival in acute lymphoblastic leukemia is not known.

DESIGN AND METHODS

We analyzed the outcome of 48 adults (median age 26 years) with high-risk, Philadelphia-chromosome-negative acute lymphoblastic leukemia undergoing T-cell depleted unrelated donor-hematopoietic stem cell transplantation (67% 10 of 10 loci matched) in first complete remission reported to the British Society of Blood and Marrow Transplantation Registry from 1993 to 2005.

RESULTS

T-cell depletion was carried out by in vivo alemtuzumab administration. Additional, ex vivo T-cell depletion was performed in 21% of patients. Overall survival, disease-free survival and non-relapse mortality rates at 5 years were 61% (95% CI 46-75), 59% (95% CI 45-74) and 13% (95% CI 3-25), respectively. The incidences of grades II-IV and III-IV acute graft-versus-host disease were 27% (95% CI 16-44) and 10% (95% CI 4-25), respectively. The actuarial estimate of extensive chronic graft-versus-host disease at 5 years was 22% (95%CI 13-38). High-risk cytogenetics at diagnosis was associated with a lower 5-year overall survival (47% (95% CI 27-71) vs. 68% (95% CI 44-84), p=0.045).

CONCLUSIONS

T-cell depleted hematopoietic stem cell transplantation from unrelated donors can result in good overall survival and low non-relapse mortality for adults with high-risk acute lymphoblastic leukemia in first complete remission and merits prospective evaluation.

Neutrophils express CD52 and exhibit complement-mediated lysis in the presence of alemtuzumab

Neutropenia is a recognized adverse event in patients treated with the humanized anti-CD52 monoclonal antibody alemtuzumab. However, as it is widely believed that neutrophils do not express CD52, the etiology of alemtuzumab-associated neutropenia is unclear. We have found that neutrophils express both mRNA coding for CD52 and the protein itself on the cell surface. We confirmed cell-surface expression using 3 different anti-CD52 antibodies, and note that neutrophils express lower levels of CD52 than lymphocytes and eosinophils. Further, incubation of alemtuzumab with neutrophils results in dose-dependent, complement-mediated lysis in the presence of both heterologous and autologous complement. These data offer an explanation for the etiology of alemtuzumab-associated neutropenia. In a climate of increased use of alemtuzumab in leukemia and other disease states, as well as in transplantation, these data highlight the need for increased vigilance of emerging neutropenia in patients treated with alemtuzumab.

Alemtuzumab markedly reduces chronic GVHD without affecting overall survival in reduced-intensity conditioning sibling allo-SCT for adults with AML

By retrospective analysis of 88 patients from the British Society of Blood and Marrow Transplantation registry, we investigated the effect of in vivo T-cell depletion in HLA-identical sibling reduced-intensity conditioning (RIC) allografts for adult AML by comparing patients who received alemtuzumab with those without alemtuzumab conditioning. Both groups were equivalent for age, sex, karyotype and disease status at transplant. With a median follow-up of 27 months (3-72 months) and 48 months (7-72 months), the 2- and 5-year overall survival, with or without alemtuzumab, is 60 and 60% (P=0.80) and 61 and 53%, respectively (P=0.85). The 2-year non-relapse mortality is 12% with alemtuzumab, and 17% without alemtuzumab (P=0.49). The 2-year relapse rate is 35% with alemtuzumab compared with 19% without alemtuzumab (P=0.28). Grades II-IV acute GVHD occurred in 22% (8/37) without alemtuzumab compared with 14% (7/51) given alemtuzumab (P=0.25). Extensive chronic GVHD occurred in 47% (14/30) not given alemtuzumab compared with 4% (2/45) who were given alemtuzumab (P=0.001). Among evaluable patients, the risk of infections was higher in those treated with alemtuzumab compared with those not treated with alemtuzumab (79 vs 57%, respectively, P=0.02). In conclusion, alemtuzumab has a beneficial effect by reducing chronic GVHD without affecting overall survival. Further studies are warranted before alemtuzumab can be recommended as standard in RIC allografts for AML.

Posttransplantation imatinib as a strategy to postpone the requirement for immunotherapy in patients undergoing reduced-intensity allografts for chronic myeloid leukemia

Disease relapse is a major cause of treatment failure after reduced-intensity allografts and while donor lymphocyte infusions (DLIs) can be effective salvage therapy they are associated with severe graft-versus-host disease (GVHD) when administered early after transplantation. We have therefore examined whether imatinib mesylate can delay relapse and postpone the requirement for DLI in 22 patients with chronic myeloid leukemia (CML) allografted using a reduced-intensity regimen. Imatinib was commenced on day + 35 and continued until 1 year after transplantation. Posttransplantation imatinib was well tolerated and abolished the risk of relapse during this period. Twenty-one patients completed 11 months of imatinib therapy, 15 of whom subsequently relapsed and received DLI. Ten patients to date have achieved molecular remission after DLI. Adjunctive targeted therapy allows the kinetics of disease relapse after a reduced-intensity allograft to be manipulated and represents a novel strategy by which outcome may be improved in patients who undergo transplantation for CML and other leukemias.

Allogeneic hematopoietic cell transplantation (HCT) in Hurler's syndrome using a reduced intensity preparative regimen

Allogeneic hematopoietic cell transplantation (HCT) in patients with Hurler's syndrome can improve survival and ameliorate many aspects of Hurler's syndrome including neurologic decline and cardiac compromise. Unfortunately, the toxicity of traditional preparative regimens to organs affected by the syndrome may have deleterious effects. Additionally, despite the intensity of these regimens, achieving stable donor chimerism can be difficult. We report transplant outcomes following a reduced intensity, highly immunosuppressive preparative regimen consisting of alemtuzumab, fludarabine and melphalan prior to HCT in seven patients with Hurler's syndrome treated at two centers. Six patients received grafts from unrelated donors and one received a sibling donor graft. The preparative regimen was well tolerated. All patients had initial donor engraftment at 100 days; one patient had delayed loss of donor chimerism. There was no severe acute GVHD (no GI GVHD of grade II or more, no grade IV skin GVHD). Six of the seven children are surviving at a median of 1014 (726-2222) days post transplant. This reduced intensity preparative regimen has the potential to support engraftment and improve survival and outcome in patients with Hurler's syndrome undergoing HCT.

Transplantation tolerance: lessons from experimental rodent models

Immunological tolerance or functional unresponsiveness to a transplant is arguably the only approach that is likely to provide long-term graft survival without the problems associated with life-long global immunosuppression. Over the past 50 years, rodent models have become an invaluable tool for elucidating the mechanisms of tolerance to alloantigens. Importantly, rodent models can be adapted to ensure that they reflect more accurately the immune status of human transplant recipients. More recently, the development of genetically modified mice has enabled specific insights into the cellular and molecular mechanisms that play a key role in both the induction and maintenance of tolerance to be obtained and more complex questions to be addressed. This review highlights strategies designed to induce alloantigen specific immunological unresponsiveness leading to transplantation tolerance that have been developed through the use of experimental models.

Regulatory T-cell recovery in recipients of haploidentical nonmyeloablative hematopoietic cell transplantation with a humanized anti-CD2 mAb, MEDI-507, with or without fludarabine

OBJECTIVE

We have evaluated T-cell reconstitution and reactivity in patients receiving nonmyeloablative haploidentical hematopoietic cell transplantation (HCT) protocols involving an anti-CD2 monoclonal antibody (MEDI 507) to treat chemorefractory hematopoietic malignancies.

METHODS

Three cohorts of four patients each and one cohort of six patients received one of four Medi-507-based regimens, all of which included cyclophosphamide, thymic irradiation, and a short posttransplantation course of cyclosporine.

RESULTS

Following marked T-cell depletion, initially recovering CD4 and CD8 T cells were mainly memory-type cells. A high percentage of CD4 T cells expressed high levels of CD25 in recipients of all protocols, except the only protocol to include fludarabine, early post-HCT. CD25 expression varied inversely with T-cell concentrations in blood. CD25(high) CD4 T cells expressed Foxp3 and cytotoxic T-lymphocyte-associated protein 4, indicating that they were regulatory T cells (Treg).

CONCLUSIONS

Fludarabine treatment prevents Treg enrichment after haploidentical nonmyeloablative stem cell transplantation, presumably by depleting recipient Tregs. In vitro analyses of allorecognition were consistent with a cytokine-mediated rejection process in one case and in another provided proof of principle that mixed chimerism achieved without graft-vs-host disease induces donor- and recipient-specific tolerance. More reliable achievement of this outcome could provide a promising strategy for organ allograft tolerance induction.

Impact of HLA class I and class II DNA high-resolution HLA typing on clinical outcome in adult unrelated stem cell transplantation after in vivo T-cell depletion with alemtuzumab

Survival after volunteer unrelated donor (VUD) stem cell transplantation (SCT) is influenced by matching for human leucocyte antigens (HLA). We analysed the effects of serological and molecular typing at HLA-A, -B, -C and -DRB1 in 100 patient/VUD pairs from a single transplant centre. Patients received SCT for good risk [chronic myeloid leukaemia in first chronic phase (CML-CP1), n=55] or poor risk (n=45) diseases after myeloablative conditioning and T-cell depletion with alemtuzumab. By serological typing, 70 pairs were fully matched, whereas molecular typing revealed 10 pairs with additional mismatches. The day 100 transplant related mortality was 15%. Acute graft versus host disease (GvHD) grades III-IV occurred in 11%, whilst extensive chronic GvHD in 13% of evaluable patients. There was no statistical difference in GvHD rates between patients who received grafts from fully matched or from mismatched donors. In univariate analysis the disease risk group and CMV seronegativity of recipient and donor were the only significant predictors for survival, with 3-year survival probabilities of 71.2% for CML-CP1 and 28% for poor risk diseases. In the poor risk group, HLA mismatches had a negative impact on survival (p=0.003) and progression free survival (p=0.009) contrary to CML-CP1 patients, in whom HLA mismatches at molecular or serological level did not have any impact.

Advances in the understanding of acute graft-versus-host disease

Allogeneic stem cell transplantation (SCT) remains the definitive immunotherapy for malignancy. However, morbidity and mortality due to graft-vs.-host disease (GVHD) remains the major barrier to its advancement. Emerging experimental data highlights the immuno-modulatory roles of diverse cell populations in GVHD, including regulatory T cells, natural killer (NK) cells, NK T cells, gammadelta T cells, and antigen presenting cells (APC). Knowledge of the pathophysiology of GVHD has driven the investigation of new rational strategies to both prevent severe GVHD and treat steroid-refractory GVHD. Novel cytokine inhibitors, immune-suppressant agents known to preserve or even promote regulatory T-cell function and the depletion of specific alloreactive T-cell sub-populations all promise significant advances in the near future. As our knowledge and therapeutic options expand, the ability to limit GVHD whilst preserving anti-microbial and tumour responses becomes a realistic prospect.

A study of a reduced-intensity conditioning regimen followed by allogeneic stem cell transplantation for patients with hematologic malignancies using Campath-1H as part of a graft-versus-host disease strategy

Nonmyeloablative transplantation (NMT) is intended to be less toxic than traditional allografts, but such regimens as fludarabine/melphalan still pose a significant risk of graft-versus-host disease (GVHD). We used Campath-1H in an attempt to reduce the risk of GVHD in NMT. Patients with hematologic malignancies suitable for allogeneic transplantation underwent transplantation using a regimen of fludarabine 30 mg/m(2) on days -5 to -2 (total, 120 mg/m(2)), total body irradiation of 200 cGy on day -1, and Campath-1H 20 mg/day on days -7 to -3 (total dose, 100 mg). After loss of graft in 5 of the first 6 patients, the protocol was amended by decreasing the Campath-1H dose to 20 mg on days -4 and -3 and 10 mg on day -2 (total dose, 50 mg) for all subsequent patients. GVHD prophylaxis consisted of only cyclosporine, due to the immunosuppressive effect of Campath-1H. Patients received prophylactic acyclovir, fluconazole, and a quinolone. Other requirements included creatinine clearance > or = 25 mL/min, diffusing capacity > or = 45% of predicted, and cardiac ejection fraction > or = 40%. Twenty-five patients with hematologic malignancies entered the study. The median age was 40 years (range, 26-71 years). Median time to engraftment (defined as a neutrophil count of 500 mm(3) and a platelet count of 20,000 mm(3) without platelet support on at least 2 days) was 19 days (range, 9-32 days). All patients who were treated after the amendment engrafted with 90%-100% donor cells by day 100 except for 2 early deaths. Acute GVHD developed in 40% of the patients. Patients who underwent related transplants developed GVHD after donor lymphocyte infusions for poor engraftment or relapse whereas those undergoing unrelated transplants developed GVHD de novo. Two patients (8%) developed chronic GVHD, and 48% had cytomegalovirus reactivation, which was easily managed medically. Nonrelapse mortality within the first 12 months was 12%; 32% of the patients survived at a median of 269 days. We conclude that Campath-1H, fludarabine, and melphalan is a reasonable preparative regimen for reduced-intensity transplantation with a low nonrelapse mortality, but that issues of GVHD remain problematic, due to either the use of donor lymphocyte infusions or the use of volunteer unrelated donors.

Comparable Outcomes of Matched-Related and Alternative Donor Stem Cell Transplantation for Pediatric Severe Aplastic Anemia

Matched sibling donor (MSD) bone marrow transplantation is the treatment of choice for pediatric patients with severe aplastic anemia (SAA); however, only about 33% of patients will have an HLA-identical sibling. Alternative donor (AD) transplants may be an option for these patients, but such therapies have been associated with greater incidence of graft failure and graft-versus-host disease (GVHD). We retrospectively analyzed 36 pediatric patients who received 38 bone marrow or peripheral blood stem cell transplants (15 MSD and 23 AD) for SAA at our institution from April 1997 to October 2005. Nineteen AD recipients received reduced intensity conditioning with cyclophosphamide, low-dose total body irradiation, and antithymocyte globulin (ATG) or Campath. The 4-year overall survival for MSD recipients was 93% versus 89% for AD recipients treated with reduced intensity conditioning regimens at a median follow-up of 52 months (range, 6-99 months). No patient receiving Campath, compared with 3 of 9 patients receiving ATG, developed extensive, chronic GVHD. We conclude that, for children with SAA, AD transplantation is as effective as MSD transplantation. Further, compared with ATG, preparatory regimens containing Campath may be associated with a lower incidence of extensive, chronic GHVD.

Long-term follow-up of myeloablative allogeneic stem cell transplantation using Campath "in the bag" as T-cell depletion: the Leiden experience

Graft-versus-host disease (GVHD) is a major cause of mortality and morbidity after allogeneic stem cell transplantation (alloSCT) but can be prevented by removing T-lymphocytes from the graft. Campath (anti-CD52) antibodies have been widely used in vivo for T-cell depletion following conventional and reduced intensity conditioning regimens. The use of Campath in vivo was associated with a significant reduction in GVHD but at the cost of impaired immune reconstitution. We evaluated the long-term outcome of 73 myeloablative allogeneic stem cell transplants with HLA-identical sibling donors using Campath "in the bag" as method of in vitro T-cell depletion. All patients engrafted and hematopoietic recovery was uneventful, resulting in a median of 99% donor chimerism at 3 months after alloSCT. Cytomegalovirus (CMV) reactivation occurred in 53% of the patients. No CMV disease was observed probably as a result of pre-emptive (val)ganciclovir treatment. The incidence of aGVHD was low (22% grade II). No grades III-IV aGVHD was observed and extensive chronic GVHD (cGVHD) occurred in 19% of the patients. The low incidence of GVHD and successful pre-emptive antiviral therapy resulted in low TRM of 8%. Sixteen patients died due to disease relapse after alloSCT, resulting in an overall survival of 48% at 5-years after alloSCT.

Stem cell transplantation with reduced-intensity conditioning regimens: a review of ten years experience with new transplant concepts and new therapeutic agents

The realization in the 1990s that allogeneic stem cell transplants (SCT) have a potentially curative graft-versus-leukemia (GVL) effect in addition to the antileukemic action of myeloablative conditioning regimens was a major stimulus for the development of reduced-intensity conditioning (RIC) regimens, aimed primarily at securing engraftment to provide the GVL effect, while minimizing regimen-related toxicity. It is now over 10 years since RIC regimens were heralded as a new direction in the field of SCT. Over the last decade much has been learned about the ways in which the conditioning regimen can be tailored to provide adequate immunosuppression, and modulated to deliver a chosen degree of antimalignant treatment. The huge literature of clinical data with RIC transplantation now permits us to more clearly define the success and limitations of the approach. This review examines the origins of RIC SCT, explores the degree to which the initial expectations and purpose of the approach have been realized, and outlines some ways forward for the field.

CAMPATH: from concept to clinic

Lymphocyte depletion has a long history in the area of therapeutic immunosuppression. CAMPATH-1H (alemtuzumab) was generated in an attempt to replace anti-lymphocyte globulins in the transplant arena. Its efficacy in killing lymphocytes has established it as a licensed drug for the management of chronic lymphocyte leukaemia. Short-term therapy with alemtuzumab has demonstrated long-term benefit in a number of autoimmune conditions. This drug has the potential to facilitate recruitment of tolerance processes so enabling drug minimization in transplantation, autoimmune and hypersensitivity diseases.

Emerging therapies for graft-versus-host disease

Acute graft-versus-host disease (GVHD) and chronic GVHD remain the major barriers to successful haematopoietic cell transplantation. The induction of GVHD may be divided into three phases: (i) recipient conditioning, (ii) donor T cell activation, and (iii) effector cells mediating GVHD. Standard agents and agents under development to prevent and treat GVHD are discussed. The various pharmacological agents impact on different phases of the GVHD cascade. Sirolimus is a new immunophilin binding agent that appears to be synergistic with tacrolimus and cyclosporin. It also seems to promote allograft tolerance. Mycophenolate mofetil (MMF) is an antimetabolite that is currently under study for prophylaxis and treatment of acute and chronic GVHD; results are encouraging. Other agents such as the purine analogue pentostatin and the monoclonal antibodies alemtuzumab, daclizumab and infliximab are discussed at length within the GVHD context. The most effective approach to GVHD prevention will likely be a combination regimen where the three phases of the GVHD cascade are disrupted. Once GVHD has occurred, all three phases of the cascade are activated. Developments of combination therapy for the treatment of both acute and chronic GVHD will likely yield better results than monotherapy. The numerous new treatment modalities presented should improve the outlook for acute and chronic GVHD.

Anti-CD52 antibody, alemtuzumab, binds to Langerhans cells in Langerhans cell histiocytosis

BACKGROUND

The humanized anti-CD52 monoclonal antibody, alemtuzumab (or Campath-1H), has been shown to potently deplete lymphocytes in human patients. It has been used to successfully treat graft versus host disease and chronic lymphocytic leukemia (CLL). CD52 is expressed on normal lymphocytes, monocytes, and some dendritic cell subsets. However, normal Langerhans cells (LC's) in the skin do not bind alemtuzumab. We sought to determine whether the pathologic LC's of Langerhans cell histiocytosis (LCH) express CD52 and thus could be targeted by this antibody.

METHODS

Immunohistochemistry was performed on both frozen and fixed/paraffin-embedded tissue specimens using either Campath-1G (the parental rat isotype) or Campath-1H (the humanized version of Campath in clinical use).

RESULTS

Both Campath-1H and Campath-1G were found to bind to the pathologic LC's in LCH, but not the normal LC's of skin. Specific staining was demonstrated in all (13 of 13) LCH specimens examined, though staining was somewhat variable among specimens, and tended to be weaker in paraffin-embedded specimens.

CONCLUSIONS

Expression of CD52 by the pathologic LC's seen in LCH suggests that alemtuzumab may represent a new, targeted therapy for this disease. Such therapy is particularly needed for patients with refractory, high-risk disease. Further investigation of the possible clinical use of this antibody in these patients is warranted.

Favorable effect on acute and chronic graft-versus-host disease with cyclophosphamide and in vivo anti-CD52 monoclonal antibodies for marrow transplantation from HLA-identical sibling donors for acquired aplastic anemia

Between August 1989 and November 2003, 33 patients at our center with acquired aplastic anemia underwent bone marrow transplantation (BMT) from HLA-identical sibling donors with cyclophosphamide and in vivo anti-CD52 monoclonal antibodies (MoAb) for conditioning. The median age at BMT was 17 years (range, 4-46 years). Before BMT, 58% were heavily transfused (>50 transfusions), and 42% had previously experienced treatment failure with antithymocyte globulin-based immunosuppressive therapy. Unmanipulated bone marrow was used as the source of stem cells in all patients except 1. Graft-versus-host disease (GVHD) prophylaxis was with cyclosporine alone in 19 (58%) patients; 14 received anti-CD52 MoAb in addition to cyclosporine. The conditioning regimen was well tolerated without significant acute toxicity. Graft failure was seen in 8 patients (primary, n = 4; secondary, n = 4). Of those whose grafts failed, 4 survived long-term (complete autologous recovery, n = 2; rescue with previously stored marrow, n = 1; second allograft, n = 1). The cumulative incidence of graft failure and grade II to IV acute and chronic GVHD was 24%, 14%, and 4%, respectively. None developed extensive chronic GVHD. With a median follow-up of 59 months, the 5-year survival was 81% (95% confidence interval, 68%-96%). No unexpected early or late infectious or noninfectious complications were observed. We conclude that the conditioning regimen containing cyclophosphamide and anti-CD52 MoAb is well tolerated and effective for acquired aplastic anemia with HLA-matched sibling donors. The favorable effect on the incidence and severity of GVHD is noteworthy in this study and warrants further investigation.

Graft-versus-host disease: How to translate new insights into new therapeutic strategies

Graft-versus-host disease occurs when transplanted donor-derived T lymphocytes recognize major or minor histocompatibility complex proteins and their associated peptides expressed by recipient antigen-presenting cells. A widely accepted paradigm for the pathophysiology of acute GVHD is based on the existence of 3 sequential steps: (1) injury to the host environment (as would occur during conditioning regimens); (2) donor T-cell activation, proliferation, and differentiation; and (3) damage to the target tissue caused by either cytotoxicity or indirectly by inflammatory cytokines. In order to reduce the incidence of GVHD, recent studies have focused on methods of prophylaxis as well as novel treatments for established GVHD. We review each phase in the development of acute GVHD and discuss recently developed interventions aimed to prevent or treat GVHD by interfering with these pathways.

Favourable outcome for patients with myeloid disorders treated with fludarabine-melphalan reduced-intensity conditioning and allogeneic bone marrow stem cell transplantation without the use of T-lymphocyte-depleting antibodies

We report the use of reduced-intensity conditioning (RIC)-matched sibling allogeneic bone marrow stem cell transplantation as a method of establishing a graft-vs.-leukaemia (GvL) effect against myeloid disorders using a fludarabine-melphalan protocol without the use of T-lymphocyte-depleting antibodies. The 16 patients in this group had predominantly poor-risk acute myeloid leukaemia (AML) (n=10), AML/myelodysplasia (MDS) (n=2) and MDS (n=4). All but one patient achieved full haematopoietic engraftment. Thirteen of 16 patients are alive and in continued complete remission on completion of this study with a median follow-up of 426 d (range 83-1524). The actuarial 4 yr disease-free and overall survival is 79% for both. Only one patient relapsed following transplant, giving a relapse rate of 6% during the study period. The treatment-related mortality was 13% (n= 2). Overall, acute graft-vs.-host disease (GvHD) occurred in 53% (8/15), with acute GvHD grade II or above occurring in 47% (7/15). In the 13 evaluable patients, chronic GvHD occurred in 46% (6/13), with this being extensive in three patients. These results suggest that a GvL effect can be delivered against poor-risk myeloid disorders with a low non-relapse mortality using this fludarabine-melphalan RIC protocol.

Alemtuzumab (Campath-1H) in allogeneic stem cell transplantation: where do we go from here?

Alemtuzumab (Campath-1H) has been widely used for T-cell depletion following both conventional and reduced-intensity conditioning allografts. We studied the impact of alemtuzumab used in vivo and in vitro on infections, immune reconstitution, and allograft outcome. The use of alemtuzumab in vivo following reduced-intensity conditioning and unrelated donor conventional transplantation was associated with durable engraftment and significant reduction in graft-versus-host disease (GVHD) but at the cost of impaired immune reconstitution and increased infectious complications. Alemtuzumab exposure in vitro was associated with durable engraftment and reduced GVHD following conventional transplants without affecting immune recovery to the same extent. Improved results were obtained following a further reduction in the alemtuzumab dose in vitro from 20 mg to 10 mg. Subsequent pharmacokinetic studies on alemtuzumab demonstrated that the antibody persisted at a higher concentration at the time of transplant and for at least 2 months thereafter when used in vivo compared to persistence for less than 30 days when used at 20 mg in vitro. In this context; an antibody with a shorter half-life, like the original rat CD52 antibody Campath-1G, would be preferable. Otherwise, our cumulative experience with alemtuzumab suggests that better results might be achieved by tailoring the dose and mode of antibody use to match the clinical situation. Further studies are needed to optimize the dose of alemtuzumab in vivo and in vitro, determined by the type of conditioning and the graft.

The role of monoclonal antibodies in stem cell transplantation

Monoclonal antibodies directed at the lymphoid antigens have become established treatments for hematological malignancies either alone or in combination with chemotherapy. However, their incorporation in the transplant setting remains investigational. This review focuses on the currently available data for in vitro and in vivo purging with these antibodies as well as their role in modulating graft-versus-host disease (GVHD).

Allogeneic stem cell transplantation for autoimmune diseases: nonmyeloablative conditioning regimens

Hematopoietic stem cell transplantation (HSCT) for autoimmune diseases have been, because of safety reasons, overwhelmingly autologous. Results are, in general, encouraging with improvement in quality of life, a remission of up to several years, and perhaps in some diseases improved survival. This indicates that further study of autologous HSCT especially under phase III design is warranted. However, the ultimate goal of HSCT is cure of otherwise incurable autoimmune diseases. For this reason, allogeneic HSCT in carefully selected high-risk patients with autoimmune diseases using strategies to minimize both regimen-related toxicity and graft-versus-host disease (GVHD) is ongoing at Northwestern University and will be reviewed briefly.