Allogeneic bone marrow transplantation from unrelated donors using in vivo anti-T-cell globulin

Influence of anti-thymocyte globulin plasma levels on outcome parameters in stem cell transplanted children

INTRODUCTION

Allogenic hematopoietic stem cell transplantation is a curative option for malignant and non-malignant pediatric diseases. Serotherapy is often employed to avoid graft-versus-host disease (GvHD) on one hand and graft rejection on the other hand. Therapeutic drug monitoring is increasingly used to allow for more precise dosing especially in pediatric patients due to their specific pharmacological characteristics. Application of T-cell directed antibodies is not routinely monitored, but may benefit from more precise dosing regimens.

METHODS

Two different preparations of rabbit anti-thymocyte globulin (rATG), Thymoglobuline® and ATG-F (Grafalon®), are frequently used to prevent GvHD in pediatric patients by in vivo T-cell depletion. Total rATG levels and active rATG levels were analyzed prospectively in pediatric patients undergoing HSCT. Clinical and laboratory outcome parameters were recorded.

RESULTS

rATG levels were measured in 32 patients, 22 received thymoglobuline and 10 received ATG-F. The median total peak plasma level was 419.0 µg/ml for ATG-F and 60.4 µg/ml for thymoglobuline. For ATG-F, exposure could be predicted from the calculated dose more precisely than for thymoglobuline. Active peak plasma levels neither of ATG-F, nor of thymoglobuline correlated significantly with the number of lymphocytes prior to serotherapy. There was no significant difference in incidence of aGvHD, cGvHD, rejection, mixed chimerism or viral infections in the two cohorts. However, in our cohort, patients with high thymoglobuline exposure showed a compromised reconstitution of T cells.

CONCLUSIONS

ATG-F and thymoglobuline show different pharmacological and immunological impact in children, whose clinical significance needs to be investigated in larger cohorts.

Immune reconstitution and outcomes after conditioning with anti-thymocyte-globulin in unrelated cord blood transplantation; the good, the bad, and the ugly

Unrelated umbilical cord blood transplantation (UCBT) exhibits a low risk of graft-versus-host-disease (GvHD) and has unique potent anti-virus and anti-leukemia effects. Anti-thymocyte globulin (ATG) in the conditioning regimen for UCBT is successful in reducing graft rejection and GvHD. Nevertheless, this beneficial effect of ATG coincides with its detrimental effect on immune reconstitution. The latter directly relates to a high incidence of viral infections and leukemia relapses. ATG has been used in transplant patients for over 30 years. In recent years, the knowledge on the mechanisms of action of ATG and its implementation in the UCBT setting has increased dramatically. Important data became available showing the highly variable pharmacokinetics (PK) of ATG and its consequence on outcome measures. Here, we review the effects of ATG on immune reconstitution and subsequent outcomes after UCBT, and describe the mechanisms causing these effects. We highlight the importance of optimizing ATG exposure before and after UCBT and discuss strategies to maintain the 'good' and overcome the 'bad and ugly' effects of ATG on UCBT outcome.

Excellent T-cell reconstitution and survival depend on low ATG exposure after pediatric cord blood transplantation

Successful immune reconstitution (IR) is associated with improved outcomes following pediatric cord blood transplantation (CBT). Usage and timing of anti-thymocyte globulin (ATG), introduced to the conditioning to prevent graft-versus-host disease and graft failure, negatively influences T-cell IR. We studied the relationships among ATG exposure, IR, and clinical outcomes. All pediatric patients receiving a first CBT between 2004 and 2015 at the University Medical Center Utrecht were included. ATG-exposure measures were determined with a validated pharmacokinetics model. Main outcome of interest was early CD4⁺ IR, defined as CD4⁺ T-cell counts >50 × 10⁶/L twice within 100 days after CBT. Other outcomes of interest included event-free survival (EFS). Cox proportional-hazard and Fine-Gray competing-risk models were used. A total of 137 patients, with a median age of 7.4 years (range, 0.2-22.7), were included, of whom 82% received ATG. Area under the curve (AUC) of ATG after infusion of the cord blood transplant predicted successful CD4⁺ IR. Adjusted probability on CD4⁺ IR was reduced by 26% for every 10-point increase in AUC after CBT (hazard ratio [HR], 0.974; P < .0001). The chance of EFS was higher in patients with successful CD4⁺ IR (HR, 0.26; P < .0001) and lower ATG exposure after CBT (HR, 1.005; P = .0071). This study stresses the importance of early CD4⁺ IR after CBT, which can be achieved by reducing the exposure to ATG after CBT. Individualized dosing of ATG to reach optimal exposure or, in selected patients, omission of ATG may contribute to improved outcomes in pediatric CBT.

Effect of ATG-F on B-cell reconstitution after hematopoietic stem cell transplantation

Antithymocyte globulin Fresenius (ATG-F) is used before hematopoietic stem cell transplantation to prevent graft rejection and graft-versus-host disease in patients with HLA-matched unrelated donors or mismatched volunteers. However, little is known about the effect of ATG-F on the reconstitution of B-cell subsets. Sixty-seven patients were longitudinally studied at day 15, day 30, and then monthly after hematopoietic stem cell transplantation. Conditioning regimes included ATG-F, which was infused at days 3, 2 and 1 at a dosage of 10 mg/kg/d. Twenty-seven patients received conditioning regimes without ATG. ATG-treated patients showed a significant delay of CD19+ B cells in the early recovery period. The absolute numbers of circulating CD19+ B cells were significantly lower (P < 0.05) up to 5 months post-transplantation compared to non-ATG patients. The recovery of the memory compartment was delayed in both groups and did not reach normal values 1-year post-transplantation. ATG-treated patient showed significantly lower absolute numbers of circulating CD27+ memory B cells in the first-month after transplantation compared to non-ATG patients. In conclusion, treatment with ATG in the conditioning regime of patients undergoing allogeneic hematopoietic stem cell transplantation leads to a significant delay of CD19+ B cells. Thus, ATG seems also to negatively influence B-cell immune reconstitution.

Less graft-versus-host disease after rabbit antithymocyte globulin conditioning in unrelated bone marrow transplantation for leukemia and myelodysplasia: comparison with matched related bone marrow transplantation

One of the major drawbacks for unrelated donor (UD) bone marrow transplantation (BMT) is graft-versus-host disease (GVHD). Despite results from randomized trials, antithymocyte globulin (ATG) is not routinely included for GVHD prophylaxis in UD BMT by many centers. One of ways to demonstrate the usefulness of rabbit ATG in UD BMT is to evaluate how its results approximate to those observed in matched related (MRD) BMT. Therefore, we compared the outcomes between UD BMT with rabbit ATG (Thymoglobulin) for GVHD prophylaxis (n = 25) and MRD BMT (n = 91) for leukemia and myelodysplasia. All but one patient received a myeloablative conditioning regimen. Grades II–IV acute GVHD were similar (39.5% vs. 36%, p = 0.83); however, MRD BMT recipients developed more moderate-severe chronic GVHD (36.5% vs. 8.6%, p = 0.01) and GVHD-related deaths (32.5% vs. 5.6%, p = 0.04). UD BMT independently protected against chronic GVHD (hazard ratio 0.23, p = 0.04). The 6-month transplant-related mortality, 1-year relapse incidence, and 5-year survival rates were similar between patients with non-advanced disease in the MRD and UD BMT groups, 13.8% vs. 16.6% (p = 0.50), 20.8% vs. 16.6% (p = 0.37), and 57% vs. 50% (p = 0.67), respectively. Stable full donor chimerism was equally achieved (71.3% vs. 71.4%, p = 1). Incorporation of rabbit ATG in UD BMT promotes less GVHD, without jeopardizing chimerism evolution, and may attain similar survival outcomes as MRD BMT for leukemia and myelodysplasia especially in patients without advanced disease.

Acute graft-versus-host disease: new treatment strategies

PURPOSE OF REVIEW

Graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT), despite improvements in our understanding of its pathophysiology as well as the generation of new monoclonal antibodies, immunomodulatory chemotherapy, cellular therapeutics and supportive care. Herein, we review therapies that have proven effective as well as newer agents that have recently improved GVHD response rates and survival following HCT.

RECENT FINDINGS

Novel approaches to prevent or treat GVHD are often based on evidence from experimental models. Our understanding of the pathophysiology of GVHD may lead to the development of innovative strategies that target both soluble and cellular effectors. Among such agents are sirolimus, anti-tumor necrosis factor antibodies, anti-LFA-3-IgG fusion protein, extracorporeal photopheresis, mesenchymal stem cells and regulatory T cells.

SUMMARY

Obstacles to the improvement of HCT include the tight linkage between GVHD toxicity and the beneficial graft-versus-leukemia (GVL) effect, as well as the impairment of immune reconstitution by immunomodulatory drugs leading to life-threatening infections. The design of newer phase I/II clinical trials are underway. Future therapies are likely to include modulation of cell types that play key roles in the GVH process, including regulatory T cells, dendritic cells, natural killer T cells and B cells.

A novel GVHD-prophylaxis with low-dose alemtuzumab in allogeneic sibling or unrelated donor hematopoetic cell transplantation: the feasibility of deescalation

Prophylaxis of acute graft-versus-host disease (aGVHD), while maintaining the graft-versus-leukemia (GVL)/lymphoma effect and preventing severe infectious diseases, remains the main challenge in allogeneic hematopoetic cell transplantation (allo-HCT). To evaluate this, we examined the feasibility of deescalating the dose of alemtuzumab (MabCampath) in combination with cyclosporine (CsA) as the sole GVHD-prophylaxis in patients after fludarabine (Flu)-based reduced-intensity conditioning (RIC) in an observational cohort study. We included 127 consecutive patients (median age 63 years) with an unrelated (UD; n=69) or related donor (SIB; n=58) after their first transplantation, mostly presenting with advanced disease. The first 30 patients received 20 mg/day on day -2 and -1 (40 mg), the following 48 patients 10 mg/day on day -2 and -1 (20 mg), and the last 49 patients 10 mg on day -1 (10 mg) alemtuzumab intravenous (i.v.) prior to transplant. We observed no statistical differences comparing the 40 mg, 20 mg, or 10 mg dose groups, in terms of cumulative incidences of aGVHD grade III-IV 7% (confidence interval [CI] 95%; 1-51), 12% (1-40), 6% (1-40), extensive chronic GVHD (cGVHD) 24.4% (3.3-55.8), 17% (2.5-42), and 14.2% (1.5-41.5) and of aGVHD grade II-IV 7 % (0-51.5), 29% (11.9-49.1), 21% (15.3-43.1), respectively. The difference between the 20-mg and 40-mg groups was significant for aGVHD grade II-IV(P < .05). In conclusion, we demonstrate the feasibility of reducing the dose of alemtuzumab as GVHD-prophylaxis to 10 mg absolute in combination with CsA only for UD transplantation in particular.

Improved nonrelapse mortality and infection rate with lower dose of antithymocyte globulin in patients undergoing reduced-intensity conditioning allogeneic transplantation for hematologic malignancies

We sought to reduce the risk of infectious complications and nonrelapse mortality (NRM) associated with the use of antithymocyte globulin (ATG) without compromising control of acute graft-versus-host disease (aGVHD) in patients undergoing reduced-intensity conditioning (RIC) transplantation. As part of an ongoing quality improvement effort, we lowered the dose of rabbit ATG from 7.5 mg/kg of ATG (R-ATG) (n = 39) to 6.0 mg/kg of ATG (r-ATG) (n = 33) in association with fludarabine (Flu) and busulfan (BU) RIC transplantation and then monitored patients for adverse events, relapse, and survival. Of the 72 mostly high risk (82%) patients studied, 89% received unrelated donor allografts, 25% of which were HLA-mismatched. No differences in posttransplantation full donor-cell chimerism rates were observed between the 2 ATG-dose groups (P > .05). When R-ATG versus r-ATG patients were compared, we observed no significant difference in the cumulative incidence of grade II-IV aGVHD (32% versus 27%; P = .73) or grade III-IV aGVHD (23% versus 11%; P = .28). However, the r-ATG group had significantly less cytomegalovirus (CMV) reactivation (64% versus 30%; P = .005) and bacterial infections (56% versus 18%; P = .001), a better 1-year cumulative incidence of NRM (18% versus 3%; P = .03), and a trend for better 1-year overall survival (OS) (64% versus 84%; P = .07) compared to R-ATG patients. A seemingly modest reduction in the dose of rabbit ATG did not compromise control of aGVHD or achievement of donor chimerism, but led to a significant decrease in the risk of serious infections and NRM in high-risk RIC allograft recipients.

Feasibility of conditioning with thymoglobulin and reduced intensity TBI to reduce acute GVHD in recipients of allogeneic SCT

Murine studies using anti-T-cell antibodies for conditioning in allogeneic SCT demonstrate engraftment with low rates of GVHD. On the basis of this preclinical model, we conditioned 30 patients with advanced hematologic malignancies with rabbit antithymocyte globulin (ATG) and TBI, to reduce rates of fatal acute GVHD. Patients were enrolled in two sequential groups: cohort 1 received ATG 10 mg/kg in divided doses (days -4 to -1)+200 cGy TBI (n=16), and cohort 2 received ATG (days -10 to -7)+450 cGy TBI (n=14). Median donor blood chimerism for the combined group was 94, 93 and 93% in the first, second and third months after transplant. Only three developed grade II acute GVHD despite 43% of patients receiving unrelated donor transplants. One-year survival was 71+/-11 and 54+/-14%, respectively, in recipients of related and unrelated donor SCT. Donor lymphocyte infusions were needed in 12 patients for the management of relapse and for mixed donor-recipient chimerism in 4 patients. We conclude that 10 mg/kg ATG and TBI allows engraftment with a low risk of acute GVHD; however, further dose optimization of ATG is required to achieve a balance between GVHD and disease relapse.

Long-term outcome of unrelated donor transplantation for AML using myeloablative conditioning incorporating pretransplant Alemtuzumab

The outcome of 55 patients who underwent matched unrelated donor (MUD) transplantation for acute myelogenous leukemia (AML) following a conditioning regimen of cyclophosphamide and total-body irradiation (TBI) with the addition of Alemtuzumab 10 mg/kg/day on days -5 to -1 is described. All patients received graft-versus-host disease (GVHD) prophylaxis with cyclosporine as well as 3 doses of posttransplant methotrexate. Forty-one patients were transplanted in complete remission (CR) (20 in CR1, 20 in CR2, and 1 in CR3), and 14 were not in remission at the time of transplantation as they were refractory to chemotherapy either at induction or at relapse. The group consisted of adult patients with a median age of 37 years. Thirty-five patients were fully matched at HLA-A, -B, -C, and -DRB1. All patients engrafted and there were no cases of graft rejection. Grade II-IV acute GVHD occurred in only 2 patients. Chronic GVHD developed in 30% of patients but was extensive in only 3 cases. The predicted TRM was 11% at day 100 and 26% at 1 year. In multivariate analysis the receipt of an HLA mismatched transplant was associated with a higher transplant-related mortality (TRM) (55% versus 15%). Twelve of the 14 transplant-related deaths were due to infection. The 5-year cumulative incidence of relapse was 36% for the whole group and 28% for patients in CR at transplantation. The 5-year cumulative survival for the whole group was 38% and was 49% for those in remission at transplantation. Seven of the 12 patients transplanted in CR1 with adverse risk cytogenetics remain alive and in remission, and the predicted 5-year overall survival (OS) for this group is 50%. These results support the use of Alemtuzumab for unrelated donor hematopoietic stem cell transplant (HSCT) for poor risk AML in CR1 and for relapsed AML in CR2. The addition of Alemtuzumab is highly effective in preventing both rejection and severe acute and extensive chronic GVHD without an increased relapse risk.

Management of acute graft-versus-host disease

Acute graft-versus-host disease (GvHD) is a frequent complication of allogeneic haemopoietic stem cell transplantation (HSCT) and donor lymphocyte infusions (DLI). Its incidence and severity depends on several factors, such as prophylaxis method, donor/recipient matching, intensity of the conditioning regimen and composition of the graft. Significant progress has been made in recent years in understanding the pathogenesis of the disease, and some of these advances have been translated into clinical trials. First-line treatment of acute GvHD is based on corticosteroids, and produce sustained responses in 50-80% of patients depending on the initial severity. Non-responders are offered second-line therapy, with combinations of immunosuppressive agents, but 1-year survival is 30% in most large trials. New strategies explored include infusion of expanded mesenchymal stem cells (MSC), down regulation of antigen-presenting cells (APC) and suicide gene transduced T cells. Acute GvHD is complicated by severe immunodeficiency causing life-threatening infections. To date, GvHD has not been differentiated from the graft-versus-leukaemia effect. The present review will discuss some of these aspects.

Thymoglobulin prevents chronic graft-versus-host disease, chronic lung dysfunction, and late transplant-related mortality: long-term follow-up of a randomized trial in patients undergoing unrelated donor transplantation

This is an update of a randomized study on antithymocyte globulin (ATG; Thymoglobulin) before transplantation in patients undergoing unmanipulated marrow transplantation from unrelated donors. The median follow-up for surviving patients is 5.7 years. At last follow-up, chronic graft-versus-host disease (GVHD) was scored in 60% of non-ATG and in 37% of ATG patients (P=.05), and extensive chronic GVHD was present in 41% and 15%, respectively (P=.01). Chronic lung dysfunction was diagnosed in 51% versus 19% of patients (P=.005). Forced vital capacity decreased significantly with time in non-ATG patients (P=.005), but not in patients who received ATG (P=.30). The proportion of patients with Karnofsky scores of >or=90% at 4 years was 57% versus 89% in non-ATG versus ATG patients (P=.03). The actuarial 6-year survival for all patients randomized was 31% versus 44% (non-ATG versus ATG; P=.80). The cumulative incidence of transplant-related mortality was 51% versus 41% (P=.70) and of relapse was 32% versus 40% (P=.90). For patients who survived 1 year, transplant-related mortality was 25% versus 3% (P=.03), and actuarial survival was 58% versus 85% (P=.09). In conclusion, the addition of ATG to cyclosporine/methotrexate provides significant protection against extensive chronic GVHD and chronic lung dysfunction, reduces late transplant mortality, and improves quality of life in patients undergoing unrelated donor transplantation.

Allogeneic haematopoietic cell transplantation for multiple myeloma: reducing transplant-related mortality while harnessing the graft-versus-myeloma effect

Allogeneic haematopoietic cell transplantation (allo-HCT) provides effective therapy for patients with various haematological malignancies. In multiple myeloma (MM) this approach can induce response rates in 35-75% of patients. However, the outcome is hampered by high rates of treatment-related mortality (TRM). Reduced intensity conditioning to lower TRM has been successfully applied. The fact that previous clinical reports have documented graft-versus-myeloma (GVM) activity without graft-versus-host disease (GVHD) suggests that at least two distinct immunocompetent cell populations mediating GVHD and/or GVM may exist. Further characterization of effectors after allo-HCT and their targets may help to clarify the immune response that mediates the GVM effect. This review considers the clinical results with myeloablative and reduced intensity conditioning prior to allo-HCT for MM, with emphasis on attempts to prevent GVHD while preserving the GVM effect. Strategies including donor lymphocyte infusions as part of the allogeneic protocol and antigenic targets for GVM effect are reviewed.

Antithymocyte globulin for prevention of graft-versus-host disease

PURPOSE OF REVIEW

This review aims to discuss current clinical trial using antithymocyte globulin in the context of hematopoietic stem cell transplantation. Published papers, as well as abstracts from European and American meetings, have been used together with original data.

RECENT FINDINGS

The review shows that antithymocyte globulin is used frequently in Europe in the setting of unrelated or family mismatched donor transplants. This may not be the case for American centers, reluctant to introduce antithymocyte globulin possibly due to known side effects such as prolonged immune deficiency and increased incidence of infections, including life threatening Epstein-Barr virus-associated lymphoproliferative disorders. Results from few randomized trials show that antithymocyte globulin reduces acute and chronic graft-versus-host disease, and this is in keeping with results from retrospective analysis on large number of patients.

SUMMARY

Several issues remain open, such as optimal dose, optimal timing with respect to infusion of stem cells and whether the commercially available agents have comparable effects. Prospective trials are needed to answer these important questions.

What role is there for antithymocyte globulin in allogeneic nonmyeloablative canine hematopoietic cell transplantation?

We investigated whether pretransplantation immunosuppression with canine-specific rabbit antithymocyte globulin (ATG), combined with a suboptimal dose of 1 Gy of total body irradiation (TBI), would permit engraftment of canine dog leukocyte antigen-identical marrow. Cumulative ATG doses of 2 to 5 mg/kg produced a T-cell depletion of 1 log in the peripheral blood and 50% in the lymph nodes. Serum levels of ATG peaked on days 4 to 6 after initiation of therapy and became undetectable by day 13 as a result of canine antibody responses to ATG. ATG prolonged allogeneic skin graft survival to 14 days (n = 5), compared with 8 days in control dogs (P = .0003). Five dogs were given marrow transplants after ATG (3.5-5 mg/kg) and 1 Gy of TBI. Posttransplantation immunosuppression consisted of mycophenolate mofetil and cyclosporine. All dogs showed initial engraftment, with maximum donor chimerism levels of 25%. However, only 1 dog achieved sustained engraftment, and 4 rejected their grafts. The duration of engraftment ranged from 8 to > or = 36 weeks (median, 11 weeks), and this is comparable to that in 6 historical controls not given ATG (range, 3-12 weeks; median, 10 weeks; P = .20). The total nucleated cell doses in the marrow grafts had the highest correlation coefficient with the duration of engraftment: 0.82 (P = .09). We concluded that administering ATG before an otherwise suboptimal conditioning dose of 1 Gy of TBI failed to secure uniform stable hematopoietic engraftment.

Heterogeneous Clearance of Antithymocyte Globulin after CD34+-Selected Allogeneic Hematopoietic Progenitor Cell Transplantation

Antithymocyte globulins (ATG) are purified, concentrated preparations of polyclonal immunoglobulin G from hyperimmune serum of horses or rabbits immunized with human thymus lymphocytes. Both the horse and the rabbit products induce immunosuppression as a result of lymphocyte depletion and immune modulation. The exact mechanism of action is unknown but may include T-cell clearance from the circulation and modulation of T-cell activation, homing, and cytotoxic activities. Both horse and rabbit ATG include multiple antibodies against T-cell surface antigens and have been used extensively in allogeneic hematopoietic progenitor cell transplantation (HPCT) for the treatment and prevention of graft-versus-host disease or graft rejection. To quantify the active ATG after HPCT, we developed a flow-based assay to measure residual ATG capable of binding to lymphocytes. In contrast to prior assays that measure total rabbit or horse immunoglobulin, this assay quantitates only the antibody capable of binding to lymphocytes, which presumably reflects the functionally active fraction of the xenoantiserum. Thirty patients with hematologic malignancies underwent T cell-depleted HPCT and had ATG levels assayed during the peritransplantation period. The time required for ATG levels to decay to background was quite variable (mean, 46 days; range, 14-91 days), although most patients demonstrated a rapid early clearance followed by a slower decline. The actual mean half-life was 6.8 days (range, 2.4-14.0 days). The persistence of ATG for months after administration has significant implications for the pace of immune reconstitution after transplantation and is a potentially confounding variable in any study that involves early administration of donor lymphocyte infusions or other cellular transfer. These findings indicate that ATG levels should be explicitly measured in studies that involve early donor lymphocyte administration so that proper conclusions regarding dose, safety, and efficacy can be reached.

Antilymphocyte/thymocyte globulin for graft versus host disease prophylaxis: efficacy and side effects

Antilymphocyte/thymocyte globulins (ALGs/ATGs) have now been used for over 30 years in the setting of hemopoietic stem cell transplants (HSCT), with the aim of preventing graft-versus-host disease (GvHD). This is true especially for transplants from alternative donors. In this review, we will be discussing available published and unpublished data on the advantages and disadvantages of using ALG/ATG before or after an allogeneic HSCT. These studies show that ALG/ATG significantly reduce the incidence and severity of acute and chronic GvHD. Unfortunately, they also show that immune deficiency is a more prolonged and infectious complication more frequent in patients receiving ALG/ATG, suggesting the importance of aggressive monitoring of viral and fungal infections. In particular, the emerging problem of Epstein-Barr virus (EBV) infections and EBV-related lymphoproliferative disorders will be discussed, together with the use of pre-emptive therapy with rituximab. I personally believe ALG/ATG has an important role in allogeneic HSCT, especially today with the increasing use of peripheral blood transplants and the consequent high risk of chronic GvHD. ALG/ATG should be used with caution, and the negative consequences must be understood and possibly prevented.

Evaluation of immunomodulatory treatment based on conventional and lineage-specific chimerism analysis in patients with myeloid malignancies after myeloablative allogeneic hematopoietic cell transplantation

Both conventional chimerism analysis (CCA) and lineage-specific chimerism analysis (LCA) have potential pitfalls as diagnostic means for the detection of minimal residual disease after allogeneic hematopoietic cell transplantation (aHCT). Therefore, the present study examines the results of both methods in order to determine how predictive consecutive evaluations were, with respect to the risk that the patient would relapse during post-transplant follow-up and with respect to responsiveness to immunomodulatory treatment. A total of 168 individuals with acute myeloid leukemia (AML) (n = 137) and myelo dysplastic syndrome (n = 31) were investigated with CCA and LCA at mean intervals of 24 days (range: 11-116). The median follow-up after myeloablative aHCT was 22 months (range: 4-49). Of 168 patients, 65 experienced a clinical relapse after aHCT. CCA and LCA were comparatively sensitive and specific for relapse at the intervals of chimerism testing employed in this study. Of 32 patients, 10 who were offered donor lymphocyte infusions (DLI) treatment for increasing (n = 29) or stable (n = 3) mixed chimerism (MC) achieved at least transitory CC. The observation that all patients with increasing MC relapsed despite DLI treatment (54%) or withdrawal of immune suppression (24%) indicates that novel strategies to deal with rapidly evolving relapse in AML patients, such as shortening of chimerism monitoring intervals, need to be evaluated.

Facilitating T-cell immune reconstitution after haploidentical transplantation in adults

Delayed reconstitution of cellular immunity following T-cell-depleted, CD34-enriched, allogeneic hematopoietic progenitor cell transplantation (HPCT) is the major cause of morbidity and mortality following haploidentical transplantation in adults. This is illustrated in our recent study of 28 high-risk adult patients (median age 31) who were treated with conditioning regimens containing antithymocyte globulin (ATG) before T-cell-depleted, CD34-enriched allogeneic HPCT. Overall mortality was 93% (26/28 patients) with a median survival of 4 months posttransplant. Poor cellular immune reconstitution contributed to death of 21/28 patients, with eight deaths due to opportunistic infections and seven deaths due to relapse. While recovery of normal numbers of circulating NK cells and B-cells occurred within the first 1-2 months posttransplant, recovery of normal numbers of blood T-cells was suppressed for more than 1 year. The mean half-life of active ATG levels in serum was 6 days; rapid clearance suggested that residual ATG did not contribute to the delay of posttransplant T-cell reconstitution. Rapid T-cell reconstitution was seen only in younger patients, indicating that poor thymic function and the absence of T-cells in the graft are the major causes of delayed recovery of cellular immunity. Improved cellular immunity after T-cell-depleted haploidentical HPCT will thus require novel strategies to adoptively transfer antigen specific donor T-cells without inducing lethal graft-versus-host disease (GvHD). This problem has been addressed in a preclinical murine model of MHC-mismatched bone marrow transplantation. Donor T-cells treated ex vivo with fludarabine or a UVA light-activated psoralen compound (amotosalen) have a markedly reduced ability to induce GvHD, yet the treated T-cells confer protection against murine cytomegalovirus and an infused leukemic cell line. Polyclonal donor T-cells reconstituted the blood and lymphoid compartments posttransplant and expanded in vivo. Derivatives of ex-vivo-treated donor T-cells retained the ability to produce cytokines and proliferate in response to antigen challenge. The mechanism of reduced GvHD potential of ex-vivo-treated T-cells appears to be selection of a subset of memory donor T-cells that do not initially home to secondary lymphoid organs and have reduced capacity for producing inflammation in the immediate posttransplant period. Direct selection of the memory subset by high-speed FACS confirmed the improved therapeutic index in the murine model system. Preclinical data indicate the feasibility of treating human T-cells with fludarabine, psoralen, or direct selection based upon the memory phenotype to efficiently produce a population of polyclonal donor T-cells with reduced GvHD activity. A planned clinical phase 1 trial of adoptive therapy utilizing ex vivo psoralen-treated donor T-cells in recipients of T-cell-depleted haploidentical HPCT is presented.

Transplantation of allogeneic CD34-selected stem cells after fludarabine-based conditioning regimen for children with mucopolysaccharidosis 1H (M. Hurler)

Hurler syndrome (MPS1H) is a progressive inborn error of mucopolysaccharide metabolism leading to premature death. Allogeneic hematopoietic cell transplantation (HCT) can achieve stabilization and improve long-term survival. However, large studies have shown that preparative regimen-related toxicity (RRT) and graft failure rates have been relatively high. We transplanted five Hurler children with a fludarabine-based conditioning regimen, consisting of fludarabine/busulphan/ATG for matched family donor (MFD), with the addition of melphalan for mismatched family donor and matched unrelated donor (MUD) transplantations. Median age at HCT was 27 months (range 10-36). The source of stem cells was bone marrow in one MFD and CD34-selected PBSC in four patients. Median CD34+ cell dose was 25 x 10(6)/kg (range 11.5-54). No RRT > grade II was observed. All patients are surviving at a median of 32 months (range 14-41) and show sustained donor engraftment with 3/5 having full donor chimerism, and 2/5 mixed chimerism (> 85%). We conclude that this regimen is feasible and has low toxicity in Hurler children. In combination with high doses of CD34+ selected cells (> 10 x 10(6)/kg) and donor lymphocyte infusions, stable engraftment could be achieved in unrelated and mismatched related transplantations.

Extramedullary vs medullary relapse after autologous or allogeneic hematopoietic stem cell transplantation (HSCT) in multiple myeloma (MM) and its correlation to clinical outcome

Risk-adapted treatment of multiple myeloma (MM) includes autologous (auto-) and allogeneic (allo-) hematopoietic stem cell transplantation (HSCT). Case reports on extramedullary (EM) compared to bone marrow (BM) relapse after HSCT suggest a dismal prognosis. We compared the outcome of 78 MM patients relapsing after auto- (group A: n = 53) or allo- (group B: n = 25) HSCT, stratified into BM (64 patients) vs EM (14 patients) relapse. The relapse-specific groups were also compared with respect to risk factors, including age, beta2-microglobulin, pretreatment, cytogenetics and stage. EM relapse sites were lungs (5), soft tissue (4), pericardium (2), bone (1), skin (1) and CNS (1). As of May 2004, the overall (OS) and progression-free (PFS) survival after HSCT in patients relapsing from EM sites was not significantly different from BM relapse patients, both after auto- and allo-HSCT. Although MM patients relapsing from EM sites after allo-HSCT used to be regarded as having few therapeutic options, we observed encouraging responses to donor lymphocyte infusions (DLI). Treatment responses to DLIs were observed in 5/9 (56%) BM relapse patients, and in 3/4 (75%) EM relapse patients. These observations suggest that EM relapse after HSCT is common and needs an individualized diagnostic and therapeutic approach in MM during clinical follow-up after HSCT.

Long-term follow-up after high-dose chemotherapy and autologous stem-cell transplantation for high-grade B-cell lymphoma suggests an improved outcome for high-risk patients with respect to the age-adjusted International Prognostic Index

BACKGROUND

To evaluate the long-term benefit from high-dose chemotherapy (HDCT) with autologous stem-cell transplantation (ASCT), as part of the initial treatment for patients with chemosensitive, high-grade B non-Hodgkin's lymphoma (hg B-NHL), stratified according to the age-adjusted International Prognostic Index (aaIPI).

PATIENTS AND METHODS

Eligible patients were 33 consecutive hg B-NHL patients responding to first-line chemotherapy and fulfilling at least one of the following criteria: stage III or IV, bulky disease, elevated lactate dehydrogenase or failure to achieve complete remission (CR). Twenty-two of 33 patients (67%) had two or three risk factors with respect to the aaIPI. All patients received HDCT with ASCT after a minimum of 6 weeks of VACOP-B standard therapy and VIP-E for mobilization.

RESULTS

After ASCT, 31 patients (94%) achieved CR. No treatment-related death occurred. The cumulative incidence of relapse at a medium follow-up of 10 years is 16% for 31 of 33 patients achieving CR. Twenty-five of 33 patients are in sustained CR with a disease-free survival of 76% [95% confidence interval (CI) 67% to 86%]. The overall survival at a median follow-up of 122 months (range 86-148) is 79% (95% CI 68% to 89%).

CONCLUSIONS

The results suggest that up-front HDCT with ASCT may improve long-term outcome in high-risk patients with chemotherapy-sensitive hg B-NHL when compared to historic populations treated solely with dose-intense chemotherapy. We observed that long-term survival of high-risk (two to three risk factors) patients is comparable to low-risk (zero to one risk factor) patients after HDCT and ASCT with a low incidence of late relapse.

Use of ApoB3′ hyper variable region in studying mixed chimerism and maternal contamination in North Indian populations

ApoB3' hyper variable region is one of the highly polymorphic genetic marker and reveals a high degree of allelic variation in different populations therefore; it can be a useful marker for different clinical tests in which individual differences at DNA level form the basis of detection. In the present study we compared Apo B3 HVR with other 28 STR markers at allele frequency level, heterozygosity, polymorphism information content (PIC) and power of exclusion. Our results indicated a high degree of heterozygosity, PIC and power of exclusion for Apo B3 HVR. These criteria lead us to investigate this marker for different purposes like detection of maternal contamination in chorionic villus samples and chimerism studies after the engraftment of bone marrow in bone marrow transplantation patients. The utility of this marker has been discussed in comparison of other markers.

T-cell depleting antibodies: new hope for induction of allograft tolerance in bone marrow transplantation?

Graft versus host disease (GVHD) remains the main barrier to successful allogeneic bone marrow transplant outcomes. Depletion of graft T cells is an effective way of reducing the incidence of acute and chronic GVHD, and a variety of methods have been used to achieve this depletion. Donor CD8+ T cells seem to be the critical effector cells; GVHD is reduced when the depletion process eliminates these cells, but not when CD4 cells are targeted alone. However, despite the successful reduction in GVHD, transplant outcomes are usually inferior with T-cell depleted transplants, because of increased graft failure, infections and relapse. Alternative approaches are needed. In vivo T-cell depletion, using antithymocyte globulin (ATG) as part of the conditioning regimen, seems an attractive option. Pre-transplant ATG lingers in the bone marrow to deplete engrafting donor T cells, but also depletes host T cells to prevent graft rejection and allow de-escalation of the conditioning regimen. It also avoids the need for graft manipulation with its associated costs, need for expertise and CD34+ cell loss. The efficacy of pre-transplant horse ATG remains anecdotal but it has been reported to modestly lower GVHD in single arm studies. Rabbit ATG has been studied in prospective randomised trials. There is evidence of a dose-response effect in reducing GVHD; however, there was no improvement in outcome, because of increased mortality associated with infection. In contrast, pre-transplant alemtuzumab (campath-1H) or an earlier version of this molecule (campath-1G), which target CD52+ cells, do appear to be effective in reducing both acute and chronic GVHD. There is speculation that this is not solely due to the effect of campath on T cells but that it may also be due to the elimination of host antigen-presenting cells (APC), which seem to be important in GVHD pathogenesis. Host APC are more efficient at expressing endogenous and exogenous host antigens on class I MHC to donor CD8+ cells than donor APC, which need to cross-prime exogenous antigen. Campath-1G eliminates host dendritic cells by the time of graft infusion, supporting this as a possible mechanism of action. Pre-transplant alemtuzumab has not yet been studied in a prospective randomised study, and this is required to quantify any benefit on outcome; despite this, published studies do show cause for optimism.

Antithymocyteglobulin as prophylaxis of graft failure and graft-versus-host disease in recipients of partially T-cell-depleted grafts from matched unrelated donors: a dose-finding study

OBJECTIVE

In this study, we set out to evaluate the effect of three different antithymocyteglobulin (ATG) doses on graft failure and incidence of graft-vs-host disease (GVHD) among recipients of partially T-cell-depleted (TCD) grafts from matched unrelated donors (MUDs).

PATIENTS AND METHODS

Data of 74 consecutively treated MUD recipients were analyzed. Fifty-two, 13, and 9 MUD patients were treated with ATG in a total dose of 8 mg/kg, 6 mg/kg, and 4 mg/kg (given from days -8 until -4), respectively.

RESULTS

Granulocyte and platelet engraftment were not different between the groups, while graft failure was observed in two patients only (receiving 8 mg/kg and 4 mg/kg ATG, respectively). The cumulative incidence of severe (grade III-IV) acute GVHD and extensive chronic GVHD was 4%, 0%, 44% and 11%, 8%, 44% in groups receiving ATG in a dose of 8 mg/kg, 6 mg/kg, and 4 mg/kg, respectively (severe acute GVHD: p<0.001; extensive chronic GVHD: p=0.05).

CONCLUSION

Based on these findings, we recommend when ATG is used in the setting of stem cell transplantation with (partially) TCD grafts from MUDs, to give a total dose of 6 to 8 mg/kg. A further decrease in dosage resulted in a highly significant increased incidence of severe acute and extensive chronic GVHD.

Immune reconstitution following reduced-intensity transplantation with cladribine, busulfan, and antithymocyte globulin: serial comparison with conventional myeloablative transplantation

The primary object of the conditioning regimen for allogeneic reduced-intensity stem cell transplantation (RIST) is immunosuppression to achieve stable engraftment of donor cells, rather than bone marrow ablation. Therefore, immune reconstitution after RIST might be different from that after conventional stem cell transplantation (CST). In this study, 22 patients underwent RIST and 28 underwent CST. The RIST regimen consisted of cladribine (2-CdA; 0.11 mg/kg/day for 6 days), BU (4 mg/kg/day for 2 days), and rabbit anti-thymocyte globulin (ATG; 2.5 mg/kg/day for 2-4 days). The CST group received either the BU (4 mg/kg/day x 4 days)/CY (60 mg/kg/day x 2 days) (n=13) or CY (60 mg/kg/day x 2 days)/TBI (4 Gy/day x 3 days) regimen (n=15). All patients underwent transplantation with G-CSF-mobilized blood stem cells. Engraftment speed after RIST was fast and seven of 22 patients did not require platelet transfusion. We noted that the numbers of CD4+, CD4+CD45RA+, and CD4+CD45RO+ T cells after transplant in the RIST group were significantly lower than those in the CST group (P=0.0001 for both the comparisons). However, the reconstitution of CD20+ B cells was faster in the RIST group (P=0.0001). The response of T cells to PHA stimulation was lower in the RIST group (P=0.0001 on day 30 and P=0.02 on day 90). Nevertheless, there were no significant differences in the incidence of bacterial, fungal, or viral infections between the two groups. We concluded that our RIST regimen might delay laboratory-evaluated T-cell immune reconstitution compared to CST; however, the observed setbacks did not directly translate into clinically significant increases in infectious episodes.

ATG as part of the conditioning regimen reduces transplant-related mortality (TRM) and improves overall survival after unrelated stem cell transplantation in patients with chronic myelogenous leukemia (CML)

Matched unrelated donor transplants have an increased risk of severe graft-versus-host disease and transplant-related mortality (TRM). ATG has been introduced to decrease GvHD and to facilitate engraftment. We conducted a retrospective analysis of 333 patients with chronic myelogenous leukemia, who were treated with Fresenius ATG (n=145, average=90 mg/kg bw, range 40-90 mg/kg bw) or standard immunosuppression without ATG (n=188). Both groups were comparable regarding distribution of age, sex, HLA-matched vs mismatched donors. ATG Fresenius led to a faster leukocyte engraftment, decreased the incidence of acute GvHD and TRM (P=0.01 and P=0.03) and led to a significant better overall survival (70 vs 57%, P=0.03). We concluded that a prospective randomized study is needed to evaluate the definite role of ATG in hemopoietic stem cell transplantation.

Reduced incidence of GVHD without increase in relapse with low-dose rabbit ATG in the preparative regimen for unrelated bone marrow transplants in CML

SUMMARY

Antithymocyte globulin (ATG) treatment prevents graft failure and results in a low incidence of GVHD, but an increased risk of relapse could be expected as a consequence of reduced GVHD. From September 1995 to June 2001, 28 consecutive chronic myeloid leukemia (CML) patients underwent unrelated bone marrow transplants: 21 were in chronic phase (CP) and seven in advanced phase (AP). Median age was 35.5 years (range 20-50). HLA typing was based on high-resolution molecular techniques; in eight cases there were one or more allele mismatches. The preparative regimen consisted of TBI, EDX 120 mg/kg and rabbit ATG 15 mg/kg. All patients engrafted and no rejection occurred. Acute GVHD grade III-IV occurred in six patients (21%). Chronic GVHD occurred in 10 (40%) and it was extensive in one. Four out of seven patients transplanted in AP had a hematological relapse. Of 21 in CP, there was one cytogenetic and one molecular relapse: these two patients are now in complete remission with imatinib mesylate. With a median follow-up of 45.7 months, the 5-year survival is 76.2% for those transplanted in CP. These data demonstrate that transplants performed in CP, with low-dose ATG, are associated with a good outcome, low incidence of GVHD and no increase of relapse.

Dose-dependent effects of in vivo antithymocyte globulin during conditioning for allogeneic bone marrow transplantation from unrelated donors in patients with chronic phase CML

We conducted a dose-escalation study with antithymocyte globulin (ATG) in patients undergoing unrelated donor bone marrow transplantation (URD-BMT). This study analyzes the results for 97 patients with chronic myelogenous leukemia (CML) in first chronic phase. Median age was 36 years (16-51). In all, 40 patients were transplanted within 2 years after diagnosis and 57 later during disease. ATG-S (Fresenius) 20-120 mg/kg body weight (b.w.) was given prior to transplantation. A total of 31 patients received less than 60 mg/kg b.w. and 66 patients received 60 mg/kg b.w. or more. All patients except one were grafted with bone marrow, and graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporin A and methotrexate. Graft failure did occur in one patient. Grade II-IV acute GVHD developed in 56.7% and extensive chronic GVHD in 11.3% of the patients. The relapse rate was 13.4%. With a median follow-up of 5.8 years (1.5-12.1), 5-year disease-free and overall survival for all patients were 56 and 66%, and for patients transplanted within 2 years of diagnosis it was 72 and 82%. A lower dose of ATG was a significant risk factor for poor outcome. In summary, URD-BMT remains an excellent treatment option for patients with early phase CML, if a sufficient amount of ATG is included in the preparative regimen.

Monoclonal antibodies for the prevention and treatment of graft-versus-host disease

Acute and chronic graft-versus-host disease (GvHD) remain major obstacles to successful allogeneic hematopoietic stem cell transplantation, contributing substantially to morbidity and non-relapse mortality. Better understanding of the immunopathophysiology of GvHD has identified a number of targets for intervention. Among newly developed agents suitable for the prevention and treatment of GvHD, monoclonal antibodies hold much promise. Monoclonal antibodies currently available, such as infliximab and anti-interferon-gamma (anti-IFN-gamma), are capable of blocking of the action of initiating and effector cytokines. Antibodies directed against activated T cells, including daclizumab, visilizumab and ABX-CBL, may offer more specificity than the more broadly acting pan-T-cell-depleting agents. Finally, the clinical investigation of antibodies to adhesion molecules (such as LFA-1), or distal effector mechanisms (such as FasL) may offer another level of specificity. Many of these monoclonal antibodies have already undergone clinical testing. Campath-1H has been used for the prevention of acute GvHD with success. Daclizumab, infliximab, visilizumab, and ABX-CBL have shown promising activity in steroid-resistant acute GvHD in early clinical testing. This review summarizes current experience with monoclonal antibodies in the management of acute and chronic GvHD. Over the next decade, however, the challenge will be to define the relative place of these antibodies in the therapeutic armamentarium for GvHD and their impact on long-term survival.

A prospective comparison of immune reconstitution in pediatric recipients of positively selected CD34+ peripheral blood stem cells from unrelated donors vs recipients of unmanipulated bone marrow from related donors

Positively selected CD34(+) hematopoietic stem cells from unrelated donors (UD-HSCT) have been successfully transplanted, but little is known about immune reconstitution in this setting. Here we report a prospective comparison of immune reconstitution in recipients of UD-HSCT and of unmanipulated bone marrow from matched sibling donors (MSD-BMT). T-cell reconstitution occurred more than 100 days later in the UD-HSCT than in the MSD-BMT group. The first T cells after UD-HSCT were almost exclusively CD45RO(+) HLA-DR(+), whereas early-emerging T cells after MSD-BMT more frequently expressed CD62L, CD28, and CD25. In both groups, numbers of CD45RA(+) naive T cells increased after 180 days. After UD-HSCT, the T-cell-receptor (TCR)-repertoire was severely skewed and showed significantly reduced diversity during the first year, but only minor abnormalities were seen after MSD-BMT. TCR-diversity increased simultaneously with the number of naive T cells. In both groups, we observed transient expansions of gammadelta T cells. B cells were reconstituted more rapidly in UD-HSCT than in MSD-BMT recipients, whereas the rapidity of NK-cell reconstitution was similar in the two groups. In summary, T-cell reconstitution was slower after UD-HSCT than after MSD-BMT because of the delayed recovery of early memory-type T cells with reduced TCR-diversity, whereas naive T-, NK-, and B cells were reconstituted similarly in the two groups.

Pharmacokinetics and pharmacodynamics of anti-thymocyte globulin in recipients of partially HLA-matched blood hematopoietic progenitor cell transplantation

Polyclonal anti-thymocyte globulin (ATG) administered before allogeneic blood hematopoietic progenitor cell transplantation reduces the risks of graft rejection and graft-versus-host disease, but may delay posttransplant immune reconstitution caused by delayed clearance of ATG from the blood. We studied graft-versus-host disease, infections, and the kinetics of immune reconstitution in 28 patients with very poor-risk hematologic malignancies who received lymphocyte-depleted, CD34(+) cell-enriched hematopoietic progenitor cell grafts from partially HLA-matched related donors (PMRD). The incidence of these clinical events was correlated with blood ATG levels in 19 transplant recipients who received rabbit ATG (r-ATG, thymoglobulin) during conditioning. Total r-ATG and the fraction of ATG antibodies that bind human cells (active ATG) were measured for up to 45 days posttransplantation using enzyme-linked immunosorbent assay and flow cytometry assays. Three patients received equine ATG (e-ATG; total dose of 60 mg/kg/day), 3 patients received 10 mg/kg r-ATG, and 22 patients received 6 mg/kg r-ATG during conditioning. All evaluable patients engrafted. Median numbers of blood CD4(+) and CD8(+) T cells at 100 days posttransplantation were 15 and 8 cells/microL, respectively. Acute graft-versus-host disease developed in 3 of 3 recipients of e-ATG and 1 of 25 recipients of r-ATG. Rapid T-cell reconstitution was seen only in younger patients. Overall mortality was 93% (26/28 patients) with poor immune reconstitution contributing to death in 21 of 28 patients. Recipients of 6 mg/kg r-ATG had peak levels of total and active r-ATG of 64+/-20 microg/mL and 9.2+/-5.8 microg/mL, respectively, with clearance of active r-ATG (t(1/2)6 days) to sub-therapeutic levels (<1 microg/mL) by a median of 15 days posttransplantation (range, 8-38 days). Delayed immune reconstitution is likely a consequence of ex vivo and in vivo purging of donor T cells in the graft coupled with inadequate thymic function rather than persistence of active r-ATG in the blood for months posttransplantation.

Myeloablative intensified conditioning regimen with in vivo T-cell depletion (ATG) followed by allografting in patients with advanced multiple myeloma. A phase I/II study of the German Study-group Multiple Myeloma (DSMM)

We investigated toxicity and efficacy of in vivo T-cell depletion with anti-thymocyte globulin (ATG) as part of an intensified myeloablative conditioning regimen followed by allogeneic stem cell transplantation in patients with advanced multiple myeloma. The conditioning regimen consisted of modified total body irradiation, busulfan and cyclophosphamide (n=15) or in the case of prior dose-limiting radiotherapy of busulfan and cyclophosphamide (n=3). The median age was 44 years (range, 29-53) and the median time from diagnosis to transplant was 12 months (range, 6-144). Grade II-IV acute graft-versus-host disease (GvHD) occurred in six patients (35%). Severe grade III/IV GvHD developed in one patient (6%). Three patients died of therapy-related causes (17%). A complete remission (CR) with negative immunofixation after allogeneic transplantation was seen in eight of the evaluable patients (53%). After a median follow-up of 41 months (range, 8-84), the estimated overall survival at 6 years for all patients is 77% (CI 95%: 58-96%). The estimated progression-free survival at 6 years for all patients is 31% (CI 95%: 2-59%) and 46% (CI 95%: 9-83%) for patients with CR. In vivo T-cell depletion with ATG resulted in a low rate of severe GvHD with low treatment-related mortality, and a substantial number of long-term survivors.

Non-overt disseminated intravascular coagulation in patients during treatment with antithymocyte globulin for unrelated allogeneic hematopoietic stem cell transplantation

We assessed the effect of rabbit antithymocyte globulin manufactured by Fresenius (ATG-F) on the hemostatic system in patients (n=12) with various hematological malignancies undergoing hematopoietic stem cell transplantation (HSCT) from HLA-matched unrelated donors. For this purpose, we monitored different parameters of coagulation before, during and after the administration of ATG-F. As a control group, we recruited patients (n=10) undergoing HSCT from their HLA-identical siblings who did not receive ATG-F as part of their preparative regimens. At 24 and 48 h after ATG-F treatment had been initiated, we found a temporary rise in D-Dimer, tissue factor, soluble thrombomodulin and thrombin-antithrombin III complex levels and a significant decrease of platelet counts in patients treated with ATG-F as compared to the control group. No differences between the two groups could be detected with regard to global coagulation tests as well as the incidence of bleeding manifestations, thromboembolic complications or the development of vascular-occlusive-disease of the liver. This temporary state of a stressed but compensated coagulation system under ATG-F therapy can be addressed as nonovert disseminated intravascular coagulation (DIC). The effect was independent from the different conditioning regimens and eased off after cessation of ATG-F. We conclude that ATG-F can induce nonovert DIC in patients receiving antithymocyte globulin as part of their conditioning regimen for HSCT.

Allogeneic stem-cell transplantation from related and unrelated donors in older patients with myeloid leukemia

PURPOSE

To improve outcome for older patients with poor-prognosis myeloid malignancies by using allogeneic hematopoietic stem-cell transplantation (alloHSCT) from unrelated and sibling donors after reduced-intensity conditioning (RIC).

PATIENTS AND METHODS

Nineteen older patients (median age, 64 years; range, 60 to 70 years) with active myeloid malignancies were treated with an RIC regimen that was based on fludarabine, melphalan, and carmustine followed by alloHSCT from matched unrelated (n = 12) or sibling donors (n = 7). Before transplantation, patients had a median of 50% bone marrow blasts (range, 0% to 70%). Graft-versus-host-disease (GvHD) prophylaxis consisted of cyclosporine and mycophenolate mofetil or methotrexate. Eleven of 12 patients with an unrelated donor also received anti-T-lymphocyte globulin (ATG).

RESULTS

Engraftment was successful for all 19 patients. Seventeen assessable patients achieved complete response (CR). Four patients experienced relapse; three achieved CR again after donor lymphocyte infusion (n = 1) or a second alloHSCT (n = 2). Six patients died as a result of relapse (n = 2), GvHD-associated complications (n = 2), or fungal infections (n = 2), resulting in a 1-year nonrelapse mortality rate of 22%. With a median follow-up of 825 days (range, 595 to 1,028 days), 13 of 19 patients are alive, resulting in a 1-year survival rate of 68% (95% confidence interval, 48% to 89%).

CONCLUSION

In older patients with untreated poor-prognosis leukemia, this RIC regimen combined with alloHSCT sufficiently reduces the leukemic burden, resulting in a high CR rate. When ATG is added, matched unrelated donor transplantation can be performed safely in older patients. For these patients, early transplantation after diagnosis offers a fair chance of cure.

Matched and mismatched allogeneic stem-cell transplantation from unrelated donors using combined graft-versus-host disease prophylaxis including rabbit anti-T lymphocyte globulin

PURPOSE

With improved HLA-typing techniques, it is presently unclear what degree of identity is necessary for successful unrelated-donor stem-cell transplantation (UD SCT). Here, we describe the outcome after matched and mismatched UD SCT using a graft-versus-host disease (GVHD) prophylaxis including high-dose rabbit anti-T lymphocyte globulin (ATG).

PATIENTS AND METHODS

One hundred adult patients (median age, 37 years; range, 17 to 65 years) with hematologic malignancies underwent transplantation in early disease (first complete remission [CR1] or first chronic phase [CP1]; n = 34) or in advanced disease (second complete remission or second chronic phase, no remission, refractory; n = 66) with nondepleted bone marrow (n = 87) or peripheral-blood-derived (n = 13) stem cells from an HLA-A, HLA-B, HLA-DRB1*, or HLA-DQB1* identical (n = 75) or mismatched (one antigen, n = 21; two to three antigens, n = 4) unrelated donor. GVHD prophylaxis consisted of rabbit ATG before transplantation in addition to cyclosporine and short-course methotrexate.

RESULTS

The cumulative incidence of acute GVHD degrees II- degrees IV was 21% (95% confidence interval [CI], 14% to 33%) and 20% (95% CI, 9% to 44%) and acute GVHD degrees III- degrees IV was 5.3% (95% CI, 2% to 14%) and 4% (95% CI, 0.6% to 28%) in HLA-matched and HLA-mismatched transplantations, respectively. The risk for extensive chronic GVHD was 43% (95% CI, 32% to 59%) and 44% (95% CI, 26% to 75%) for HLA-matched and HLA-mismatched patients, respectively. The risk of relapse at 4 years was 17% (95% CI, 7% to 43%) and 43% (95% CI, 31% to 60%) for CR1/CP1 and advanced disease patients, respectively. With a median follow-up of 1,068 days (range, 12 to 1,958 days), 3-year disease-free and overall survival for patients who underwent transplantation in CR1/CP1 was 63% (95% CI, 46% to 81%) and 75% (95% CI, 59% to 90%), respectively; and for patients with advanced disease, it was 34% (95% CI, 22% to 46%) and 39% (95% CI, 25% to 53%), respectively.

CONCLUSION

A certain degree of one antigen mismatching may not compromise the outcome after UD SCT when using this rabbit ATG in addition to standard GVHD prophylaxis regimen.

Unrelated stem cell transplantation in multiple myeloma after a reduced-intensity conditioning with pretransplantation antithymocyte globulin is highly effective with low transplantation-related mortality

We investigated the feasibility of unrelated stem cell transplantation in 21 patients with advanced stage II/III multiple myeloma after a reduced-intensity conditioning regimen consisting of fludarabine (150 mg/m(2)), melphalan (100-140 mg/m(2)), and antithymocyte globulin (ATG; 10 mg/kg on 3 days). The median patient age was 50 years (range, 32-61 years). All patients had received at least one prior autologous transplantation, in 9 cases as part of an autologous-allogeneic tandem protocol. No graft failure was observed. At day 40 complete donor chimerism was detected in all patients. Grade II to IV acute graft-versus-host disease (GVHD) was seen in 8 patients (38%), and severe grade III/IV GVHD was observed in 4 patients (19%). Six patients (37%) developed chronic GVHD, but only 2 patients (12%) experienced extensive chronic GVHD. The estimated probability of nonrelapse mortality at day 100 was 10% and at 1 year was 26%. After allografting, 40% of the patients achieved a complete remission, and 50% achieved a partial remission, resulting in an overall response rate of 90%. After a median follow-up of 13 months, the 2-year estimated overall and progression-free survival rates are 74% (95% CI, 54%-94%) and 53% (95% CI, 29%-87%), respectively. A shorter progression-free survival was seen in patients who already experienced relapse to prior autograft (26% versus 86%, P =.04). Dose-reduced conditioning with pretransplantation ATG followed by unrelated stem cell transplantation provides durable engraftment and donor chimerism, reduces substantially the risk of transplant-related organ toxicity, and induces high remission rates.

Immune reconstitution after haematopoietic transplantation with two different doses of pre-graft antithymocyte globulin

Antithymocyte globulin is widely used before haematopoietic transplantation with HLA-matched unrelated donors or mismatched relatives to prevent rejection and graft-versus-host disease (GVHD). However, optimal dosage is still under debate. Thirty-one consecutive children, mainly with haematological malignancies, were transplanted in a single institution with such donors, selected by HLA-A -B compatibility by serology and DRB1* by DNA typing. Antithymocyte globulin (Thymoglobuline; Sangstat) was infused at days -3, -2, -1. Total dosage varied: 16 patients received a median of 7.5 mg/kg (2.5 to 10.5: low-dose group), and 15 a median of 15.5 mg/kg (14.4 to 19.4: high-dose group). Post-transplant GVHD prophylaxis consisted of cyclosporine, short-course methotrexate and steroids. CD3(+), CD4(+) and CD19(+) cell reconstitution was slower in the high-dose group. Median time to reach 100 CD4(+) cells was 8 months vs 4 months (P = 0.03). Median time to normal CD19(+) cells was 16 months vs 8 months (P = 0.01). CD16(+)CD56(+) and CD8(+) cell reconstitution was similar. Nine patients in the high-dose group and two in the low-dose group experienced life-threatening opportunistic infections (P = 0.009). Although obtained from a limited number of patients, our data suggest that a higher pre-graft dose of antithymocyte globulin may negatively influence immune reconstitution.

In vivo T cell depletion with low-dose rabbit antithymocyte globulin results in low transplant-related mortality and low relapse incidence following unrelated hematopoietic stem cell transplantation

Stem cell transplantation from unrelated donors is associated with an increased risk of graft failure and graft-versus-host disease (GVHD). Addition of pretransplant antithymocyte globulin (ATG), although reducing the risk of graft rejection and GVHD, bears the risk of overimmunosuppression, resulting in an increased relapse rate and transplant-related mortality. Therefore, we evaluated in 21 consecutive patients receiving unrelated stem cell grafts from either HLA-matched (38%) or -mismatched (62%) donors whether low-dose rabbit ATG added to cyclosporin A and methotrexate at a total dose of 3.5 mg/kg for HLA-identical and 5.0 mg/kg for HLA-mismatched transplants given in two divided doses on days -2 and -1 provides sufficient immunosuppression for prevention of GVHD and graft rejection but is associated with an acceptable risk of relapse and transplant-related mortality. Stable leukocyte engraftment was achieved in all patients (100%). Overall survival after a median follow-up of 26 (median, range 14-42) months was 56 +/- 26% (95% confidence interval, CI) and the overall relapse rate at 3 years was 24 +/- 21%. Three-year survival for standard-risk patients, i.e., chronic myeloid leukemia (CML) in first chronic phase or acute leukemia in first complete remission, was 87% +/- 13% versus 40% +/- 31% for patients with more advanced disease. The incidence of acute GVHD II-IV degrees was 55 +/- 22%; that of severe acute GVHD III-IV degrees was 21 +/- 19%. Chronic GVHD was observed in 5/17 (29%) patients surviving more than 100 days post stem cell transplantation. Transplant-related mortality was 16 +/- 15% (95% CI) at day + 100 and 25 +/- 19% (95% CI) at 1 year after the transplant. The data presented show that pretransplant in vivo T cell depletion with low-dose rabbit ATG results in a low transplant-related mortality due to a low incidence of severe acute and chronic GVHD and a low relapse rate. To find out the optimal rabbit ATG dose in the unrelated stem cell transplantation setting, further dose-finding studies comparing high- and low-dose regimens are necessary.

Detection of a novel specificity (CTLA-4) in ATG/TMG globulins and sera from ATG-treated leukemic patients

BACKGROUND

T-cell costimulation has been shown to provide positive signals for T-cell activation and generation of effector activity. In this study, we analyzed the presence of antibodies (Abs) against the T-lymphocyte costimulatory molecules CD28, CTLA-4, CD80, and CD86 in anti-T-lymphocyte (ATG) and antithymocyte (TMG) globulin preparations to address their mechanism of action. We focused our attention on the role of CTLA-4-specific Abs in the immunosuppressive effect of ATG/TMG, because anti-CTLA-4 agonistic Abs may suppress T-cell proliferation and nonagonistic Abs may lead to T-cell depletion through an Ab-dependent cell cytotoxicity mechanism.

METHODS

ATG/TMG and patients' sera were tested for binding to recombinant human costimulatory molecules by ELISA techniques. CTLA-4 specificity was also analyzed by cytoplasmic immunofluorescence staining of a CTLA-4 transfectant by competitive inhibition immunofluorescence and by cell proliferation assay in allogeneic mixed lymphocyte reaction (MLR).

RESULTS

Either ATG or TMG predominantly contained anti-CTLA-4 Abs, with higher reactivity in ATG followed by anti-CD86 and -CD28 Abs, whereas anti-CD80 Abs were found only in ATG. Anti-CTLA-4 Abs present in ATG/TMG recognized the native form of CTLA-4 molecule, and their removal reduced the effect of ATG in an allogeneic MLR. Kinetic studies indicated that such Abs were present in the sera of 12 ATG-treated leukemic patients up to 21 days after ATG administration.

CONCLUSIONS

These data suggest that the novel anti-CTLA-4 Abs found in ATG may greatly contribute to its immunosuppressive effect, thus accounting for the absence of rejection and exceptionally low incidence of graft-versus-host disease in the group of patients analyzed.

In vivo T cell depletion with pretransplant anti-thymocyte globulin reduces graft-versus-host disease without increasing relapse in good risk myeloid leukemia patients after stem cell transplantation from matched related donors

One-hundred and two patients with good risk myeloid leukemia (CML first chronic phase or AML first CR) were transplanted from HLA-related donors after conditioning with (n = 45) or without anti-thymocyte globulin (ATG) (n = 57). One graft failure was observed in the non-ATG and none in the ATG group. The median time to leukocyte engraftment (> 1 x 10(9)/l) was 16 (range 12-33) in the ATG group and 17 days (range 11-29) in the non-ATG group (NS) and for platelet engraftment (> 20 x 10(9)/l) 24 and 19 days (P = 0.002), respectively. Acute GVHD grade II-IV was observed in 47% of the non-ATG and in 20% of the ATG group (P = 0.004). Grade III/IV GVHD occurred in 7% of the ATG and in 32% of the non-ATG group (P = 0.002). Chronic GVHD was seen in 36% and 67% (P = 0.005), respectively. After a median follow-up of 48 months (range 2-128), the 5-year estimated OS is 66% (95% KI: 51-81%) for the ATG group and 59% (95% KI: 46-72%) for the non-ATG group (NS). The 5-year estimated DFS is 64% (95% KI: 50-78%) for ATG and 55% (95% KI: 43-67%) for the non-ATG regimen (NS). The 5-year probability of relapse was 5% in the ATG and 15% in the non-ATG group (NS). ATG as part of the conditioning regimen leads to a significant reduction in GVHD without increase of relapse in patients with myeloid leukemia after stem cell transplantation from HLA-related donors.

Tecelac as antithymocyte globulin in conditioning for childhood allogeneic stem cell transplantation

Antithymocyte globulin (ATG) preparations in allogeneic stem cell transplantation are used in various conditioning regimens both to prevent graft rejection and reduce the incidence and severity of graft-versus-host disease. Tecelac (RATG) is a highly purified ATG preparation with high specific activity. The high specific antibody content implies the need for lower doses, with reduced side-effects in comparison to other ATGs. Here, we report on the first 10 patients worldwide who received RATG as part of conditioning. Patients were heterogeneous with regard to diagnoses and graft characteristics. RATG was given in cases of matched unrelated donors, mismatched family donors, reduced conditioning, or high risk for graft failure. Mostly mild allergic reactions toward RATG were seen. All of the patients engrafted in due time. Two died within 2 months of transplant of pulmonary complications not related to RATG. Two developed GVHD grade I, no chronic GVHD was seen to date. Viremia occurred in two, with no viral disease developed. Of the eight patients surviving, one suffered relapse of acute leukemia, one shows impending graft failure. The others are well. Using RATG in conditioning is feasible.