The effect of the serotherapy regimen used and the marrow cell dose received on rejection, graft-versus-host disease and outcome following unrelated donor bone marrow transplantation for leukaemia

Harvest Quality, Nucleated Cell Dose and Clinical Outcomes in Bone Marrow Transplantation: A Retrospective Study

Higher doses of infused nucleated cells (NCs) are associated with improved clinical outcomes in bone marrow transplantation (BMT) recipients. Most clinicians recommend infusing at least 2.0 × 108 NCs/kg. BMT clinicians request a target NC dose, but the harvested NC dose may be below the requested NC dose even before cell processing. We conducted this retrospective study to investigate the quality of bone marrow (BM) harvest and factors that influence infused NC doses at our institution. We also correlated infused NC doses with clinical outcomes. The study population included 347 BMT recipients (median age, 11 years; range, <1 to 75 years) at the University of Minnesota between 2009 and 2019. Underlying diagnoses mainly included 39% malignant and 61% nonmalignant diagnoses. Requested, harvested, and infused NC doses, as well as cell processing data, were obtained from the Cell Therapy Laboratory; clinical outcomes data were obtained from the University of Minnesota BMT Database. BM harvests were facilitated either by our institution (61%) or by the National Marrow Donor Program (39%). Associations of infused doses with baseline characteristics were assessed using the general Wilcoxon test/Pearson's correlation coefficient. The association of infused dose with neutrophil engraftment (absolute neutrophil count >500) by day 42, platelet engraftment (>20,000) by 6 months, acute graft-versus-host disease grade II-IV, and overall survival (OS) at 5 years were evaluated using regression and Kaplan-Meier curves. The median requested NC dose was 3.0 × 108/kg (range, 2 to 8 × 108/kg), and the median harvested and infused NC doses were 4.0 × 108/kg and 3.6 × 108/kg, respectively. Only 7% of donors had a harvested dose below the minimum requested dose. Moreover, the correlation between requested doses and harvested doses was adequate, with a harvested/requested dose ratio <.5 observed in only 5% of harvests. Additionally, the harvest volume and cell processing method were significantly correlated with the infused dose. Harvest volume exceeding the median of 948 mL was related to a significantly lower infused dose (P < .01). Moreover, hydroxyethyl starch (HES)/buffy coat processing (used to reduce RBCs with major ABO incompatibility) led to a significantly lower infused dose (P < .01). Donor age (median, 19 years; range, <1 to-70 years) and sex did not significantly influence the infused dose. Finally, the infused dose was significantly correlated with neutrophil and platelet engraftment (P < .05) but not with 5-year OS (P = .87) or aGVHD (P = .33). In our program's experience, BM harvesting is efficient and meets the requested minimum dose for 93% of recipients. Harvest volume and cell process play significant roles in determining the final infused dose. Minimizing harvest volume and cell processing could lead to increased infused dose and thus improved outcomes. Moreover, a higher infused dose leads to a better rate of neutrophil and platelet engraftment but not to improved OS, which may be linked to the sample size of our study.

Role of abatacept in the prevention of graft-versus-host disease: current perspectives

Administration of abatacept following transplantation has been reported to inhibit graft rejection and graft-versus-host-disease (GvHD) in mouse models associated with allogeneic hematopoietic stem cell transplant (HSCT). This strategy has recently been adopted in clinical practice for GvHD prevention in human allogeneic HSCT and offers a unique approach to optimizing GvHD prophylaxis following alternative donor HSCTs. When combined with calcineurin inhibitors and methotrexate, abatacept had shown to be safe and effective in preventing moderate to severe acute GvHD in myeloablative HSCT using human leukocyte antigen (HLA) unrelated donors. Equivalent results are being reported in recent studies using alternative donors, in reduced-intensity conditioning HSCT and nonmalignant disorders. These observations have led to hypothesizing that even in the setting of increasing donor HLA disparity, abatacept when given with traditional GvHD prophylaxis does not worsen general outcomes. In addition, in limited studies, abatacept have being protective against the development of chronic GvHD through extended dosing and in the treatment of steroid-refractory chronic GvHD. This review summarized all the limited reports of this novels approach in the HSCT setting.

Targeted genome editing for the correction or alleviation of primary Immunodeficiencies

Primary immunodeficiencies (PID) are a growing list of unique disorders that result in a failure of the innate/adaptive immune systems to fully respond to disease or infection. PIDs are classified into five broad categories; B cell disorders, combined B and T cell disorders, phagocytic disorders, complement disorders, and disorders with recurrent fevers and inflammation. Many of these disorders, such as X-SCID, WAS, and CGD lead to early death in children if intervention is not implemented. At present, the predominant method of curative therapy remains an allogeneic transplant from a healthy donor, however many complications and limitations exist with his therapy such as availability of donors, graft vs host disease, graft rejection, and infection. More recently, gene therapy using viral based complementation vectors have successfully been implemented to functionally correct patient cells in an autologous transplant, but these methods carry significant risks, including insertional mutagenesis, and provide non-physiological gene expression. For these reasons, gene-editing reagents such as targeted nucleases, base editors (BE), and prime editors (PE) are being explored. The BE and PE tools, sometimes referred to as digital editors, are of very high interest as they provide both enhanced molecular specificity and do not rely on DNA repair pathways after DSBs to change individual base pairs or directly replace DNA sequences responsible for pathogenic phenotypes. With this in mind the purpose of this chapter is to highlight some of the most common PIDs found within the human population, discuss successes and shortcomings of previous intervention strategies, and highlight how the next generation of gene-editing tools may be deployed to directly repair the underlying genetic causes of this class of disease.

Low dose anti-thymocyte globulin reduces chronic graft-versus-host disease incidence rates after matched unrelated donor transplantation

Anti-thymocyte globulin (ATG) is often added to hematopoietic stem cell transplant conditioning regimens to prevent graft rejection and reduce graft-versus-host disease (GVHD). Doses used in retrospective and prospective clinical trials have ranged from 2.5 to 20 mg/kg with rates of grade II-IV acute GVHD and chronic GVHD up to 40 and 60%, respectively. We retrospectively compared outcomes in recipients of matched unrelated donor (MUD) grafts given low dose rabbit ATG IV 3 mg/kg (n = 52) versus recipients of matched related donor (MRD) grafts (n = 48) without ATG. One year cumulative incidence of chronic GVHD was 25.2% in the MUD group versus 33.3% in the MRD group (p = .5). One-year cumulative incidence of extensive chronic GVHD was 9.6% in the MUD group versus 26.6% in the MRD group (p = .042). Our analysis supports the use of low dose ATG in MUD transplantation as an effective therapy to prevent chronic GVHD.

The Role of Anti-Thymocyte Globulin or Alemtuzumab-Based Serotherapy in the Prophylaxis and Management of Graft-Versus-Host Disease

Allogeneic hematopoietic stem cell transplant is an established treatment modality for hematologic and non-hematologic diseases. However, it is associated with acute and long-term sequelae which can translate into mortality. Graft-versus-host disease (GVHD) remains a glaring obstacle, especially with the advent of reduced-intensity conditioning. Serotherapy capitalizes on antibodies which target T cells and other immune cells to mitigate this effect. This article focuses on the utility of two such agents: anti-thymocyte globulin (ATG) and alemtuzumab. ATG has demonstrated benefit in prophylaxis against GVHD, especially in the chronic presentation. However, there is limited impact of ATG on overall survival and it has little utility in the treatment context. There may be an initial improvement, particularly in skin manifestations, but no substantial benefit has been elicited. Alemtuzumab has shown benefit in both prophylaxis and treatment of GVHD, but at the consequence of a more profound immunosuppressive phase, mandating aggressive viral prophylaxis. There remains heterogeneity in the doses and regimens of the agents, with no standardized protocol in place. Furthermore, it seems that once steroid-refractory GVHD has been established, there is little that can be offered to offset the ultimately dismal outcome. Here we present a systematic overview of ATG- or alemtuzumab-based serotherapy in the prophylaxis and management of GVHD.

Reduced-Intensity Conditioning with Busulfan, Fludarabine, and Antithymocyte Globulin for Hematopoietic Cell Transplantation from Unrelated or Haploidentical Family Donors in Patients with Acute Myeloid Leukemia in Remission

To investigate the role of antithymocyte globulin (ATG)-containing reduced-intensity conditioning (RIC) in hematopoietic cell transplantation (HCT) from unrelated (UD) or haploidentical family donors (HFD), we conducted a phase 2 trial of 237 patients (age range, 16 to 69 years) with acute myeloid leukemia (AML) in remission. Patients undergoing UD-HCT (n = 93) or HFD-HCT (n = 59) received RIC comprising busulfan, fludarabine, and ATG, 9 mg/kg, whereas those undergoing HCT from matched sibling donors (MSD, n = 85) received myeloablative busulfan and cyclophosphamide conditioning or aforementioned RIC with ATG, 4.5 mg/kg. For graft-versus-host disease (GVHD) prophylaxis, cyclosporine and methotrexate were administered. The median follow-up period was 44.7 months after HCT for 161 survivors. For UD-HCT versus HFD-HCT, there were no significant differences in leukemia recurrence, nonrelapse mortality, relapse-free survival, grades 2 to 4 acute GVHD, and moderate-to-severe chronic GVHD. Furthermore, when the outcomes of UD-HCT and HFD-HCT were combined and compared with those of MSD-HCT, there were no significant differences in leukemia recurrence (3-year cumulative incidence, 30% versus 29%), nonrelapse mortality (3-year cumulative incidence, 7% versus 8%), relapse-free survival (3-year estimate, 63% versus 63%), and grades 2 to 4 acute GVHD (120-day cumulative incidence, 16% versus 13%). Moderate-to-severe chronic GVHD, however, occurred less frequently in UD/HFD-HCT (2-year cumulative incidence, 22% versus 40%; P = .006). The addition of ATG to conditioning regimen was a significant predictor for less chronic GVHD (subdistribution hazard ratio, .59). In AML in remission, UD/HFD-HCT after ATG-containing RIC achieved leukemia control equivalent to that of MSD-HCT. Despite HLA disparity in UD/HFD-HCT, chronic GVHD occurred less frequently after ATG-containing RIC, suggesting a strong GVHD-modulating effect of ATG.

Population pharmacokinetic modeling of Thymoglobulin(®) in children receiving allogeneic-hematopoietic cell transplantation: towards improved survival through individualized dosing

BACKGROUND AND OBJECTIVES

To prevent graft-versus-host disease and rejection in hematopoietic cell transplantation (HCT), children receive Thymoglobulin(®), a polyclonal antibody acting mainly by depleting T cells. The therapeutic window is critical as over-exposure may result in delayed immune reconstitution of donor T cells. In this study, we describe the population pharmacokinetics of Thymoglobulin(®) as a first step towards an evidence-based dosing regimen of Thymoglobulin(®) in pediatric HCT.

METHODS

Serum active Thymoglobulin(®) concentrations were measured in all pediatric HCTs performed between 2004 and 2012 in two pediatric HCT centers in The Netherlands. Population pharmacokinetic analysis was performed using NONMEM(®) version 7.2.

RESULTS

A total of 3,113 concentration samples from 280 pediatric HCTs were analyzed, with age ranging from 3 months to 23 years old. The cumulative Thymoglobulin(®) dose was 10 mg/kg in 94 % of the patients given in 4 consecutive days. A model incorporating parallel linear and concentration-dependent clearance of Thymoglobulin(®) was identified. Body weight [for linear clearance (CL) and central volume of distribution] as well as lymphocyte count pre-Thymoglobulin(®) infusion (for CL) were important covariates. As such, the current dosing regimen results in higher exposure in children with a higher bodyweight and/or a lower lymphocyte count pre-Thymoglobulin(®) infusion.

CONCLUSION

This model can be used to develop an individual dosing regimen for Thymoglobulin(®), based on both body weight and lymphocyte counts, once the therapeutic window has been determined. This individualized regimen may contribute to a better immune reconstitution and thus outcome of allogeneic HCT.

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.

Outcomes of matched sibling donor hematopoietic stem cell transplantation for severe sickle cell disease with myeloablative conditioning and intermediate-dose of rabbit anti-thymocyte globulin

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative therapy for sickle cell disease (SCD) in children. Despite excellent outcomes of matched sibling donor (MSD) HSCT, there is still 5-10% chance of rejection and transplant related mortality (TRM) with 12-23% incidence of graft versus host disease (GVHD). We postulated that an intermediate dose of rabbit anti-thymocyte globulin (r-ATG, 10 mg/kg cumulative) would be effective in preventing both rejection and GVHD.

PATIENTS AND METHODS

Fifteen patients, median age 5 (range 1.5-18) years, underwent MSD HSCT using busulfan (≥ 12.8 mg/kg with first dose pharmacokinetics), cyclophosphamide (total 200 mg/kg) and r-ATG. Bone marrow was the stem cell source; tacrolimus and methotrexate were given for GVHD prophylaxis.

RESULTS

All patients achieved donor engraftment and there was no TRM. One patient rejected donor cells at 2 months post-transplant. Majority of the patients had high and sustained level of donor chimerism. None of the patients developed ≥ Grade II GVHD. Incidence of CMV (10%) and EBV (9%) reactivations was low with rapid immune-reconstitution. Overall survival was 100% with event free survival of 93%.

CONCLUSIONS

Eliminating the risks of TRM and GVHD by optimizing the regimen may lead to further acceptance of HSCT for SCD.

Quality of harvest and role of cell dose in unrelated bone marrow transplantation: an Italian Bone Marrow Donor Registry-Gruppo Italiano Trapianto di Midollo Osseo Study

In this study, we investigated the factors affecting cell dose harvest and the role of cell dose on outcome. We analysed data from a cohort of 703 patients who underwent unrelated bone marrow transplantation facilitated by IBMDR in GITMO centers between 2002 and 2008. The median-infused cell doses is 3.7 × 10(8)/kg, the correlation between the nucleated cells requested from transplant centers and those harvested by collection centers was adequate. A harvested/requested cells ratio lower than 0.5 was observed only in 3% of harvests. A volume of harvested marrow higher than the median value of 1270 ml was related to a significant lower infused cell dose (χ(2): 44.4; P < 0.001). No patient- or donor-related variables significantly influenced the cell dose except for the recipient younger age (χ(2): 95.7; P < 0.001) and non-malignant diseases (χ(2): 33.8; P < 0.001). The cell dose resulted an independent predictor factor for a better outcome in patients affected by non-malignant disease (P = 0.05) while early disease malignant patients receiving a lower cell dose showed a higher risk of relapse (P = 0.05).

A high antithymocyte globulin dose increases the risk of relapse after reduced intensity conditioning HSCT with unrelated donors

The study included 110 consecutive patients with hematological malignancies receiving fludarabine-based reduced intensity conditioning (RIC) and hematopoietic stem cell transplantation (HSCT) from matched unrelated donors. The median age was 55 yr (range 11-68) and all but 15 patients received peripheral blood stem cell grafts. Antithymocyte globulin (ATG) (Thymoglobulin, Genzyme) at a total dose of 6 mg/kg (n = 66) or 8 mg/kg (n = 44) was given to all patients according to protocol. The ATG dose did not affect time-to-neutrophil or platelet engraftment. The incidences of acute GVHD grades II-IV were 34% and 18% (p = 0.11) and of chronic GVHD were 40% and 26% (p = 0.46) in patients receiving 6 and 8 mg/kg of ATG, respectively. The five-yr relapse-free survival (RFS) was 61% and 36% (p = 0.14) in patients, given low and high ATG dose, respectively. In patients given low-dose ATG, the incidence of relapse was lower compared to those given high-dose ATG, 19% vs. 41% (p = 0.04). In multivariate analysis, age >50 yr (p < 0.001), absence of acute (p < 0.001) and chronic GVHD (p = 0.001) were correlated to relapse, and low-dose ATG was associated with improved RFS (p < 0.05). A high dose (8 mg/kg) of ATG in RIC HSCT with unrelated donors increased the risk for relapse and reduced the RFS.

Clinical effect of reduced-intensity conditioning regimen containing antithymocyte globulin for hematopoietic cell transplantation from unrelated-donors

The impact of reduced-intensity conditioning (RIC) on the outcomes of hematopoietic cell transplantation (HCT) from unrelated -donors (UD) remains to be determined. We therefore assessed 128 patients, aged 16 to 66 years, with acute leukemia (n = 105) or myelodysplastic syndrome (n = 23) in a UD-HCT trial using RIC with busulfan, fludarabine, and antithymocyte globulin. Patients were transplanted with unmanipulated bone marrow (BM, n = 41) or mobilized peripheral blood mononuclear cells (M-PB, n = 87) and received cyclosporine and methotrexate for graft-versus-host disease (GVHD) prophylaxis. After a median follow-up of 26.7 months (range, 5.9-70.7 months) in surviving patients, 19 patients had died without progression/recurrence of underlying disease, giving a cumulative incidence of transplantation-related mortality (TRM) of 17% (95% confidence interval, 11%-27%; 1-year TRM, 14%). Graft failure (n = 7) and infections (n = 5) were the most common causes of TRM. Only three patients died due to GVHD (acute, one; chronic, two). Graft failure, which occurred in eight patients, showed a significant correlation with graft source (BM, 6/41 vs. M-PB, 2/87; P = 0.009). Donor-patient HLA-disparity did not correlate with GVHD, 1-year TRM, and graft failure. RIC containing antithymocyte globulin led to decreased GVHD-associated, as well as overall, TRM after UD-HCT.

Evaluating the impact of antithymocyte globulin on lung function at 1 year after allogeneic stem cell transplantation

The use of antithymocyte globulin (ATG) in hematopoietic stem cell transplantation (HSCT) conditioning regimens has reduced the incidence of graft-versus-host disease, particularly in its chronic form. The impact of this approach on the prevention of lung dysfunction has not been well characterized, however. We performed a retrospective analysis of pulmonary function in patients who underwent HSCT after conditioning with oral busulfan followed by either cyclophosphamide or fludarabine with or without the addition of ATG. A total of 393 patients were included; 75 patients received ATG, and 318 did not. No differences between the 2 groups were seen in the mean percentage of the predicted values for forced expiratory volume in 1 second (FEV(1)), forced vital capacity (FVC), total lung capacity, and lung CO diffusing capacity at 80 days or 1 year after transplantation. However, the mean value of FEV(1)/FVC ratio at 1 year was higher in the patients who received ATG. The difference in mean change in pulmonary function parameters from baseline to 1 year post-HSCT was statistically nonsignificant for all parameters except FEV(1)/FVC ratio, which demonstrated less decline in the ATG group. The risk of developing severe airflow obstruction or a restrictive pattern was similar in the 2 treatment groups at 1 year post-HSCT. Incorporation of ATG into the HSCT conditioning regimen provided protection against a decline in FEV(1)/FVC ratio but did not decrease the risk of other pulmonary events that we evaluated within the first year after HSCT. Further evaluations in larger numbers of patients are needed to better clarify the role of ATG in the development of delayed pulmonary complications.

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.

Reduced-intensity conditioned allogeneic haematopoietic stem cell transplantation results in durable disease-free and overall survival in patients with poor prognosis myeloid and lymphoid malignancies: eighty-month follow-up

The long-term outcome of patients with haematological malignancies treated with reduced-intensity conditioned allogeneic peripheral blood stem cell transplantation is not known. We report the outcome of 79 patients with poor-risk myeloid and lymphoid malignancies transplanted with reduced-intensity conditioning (RIC) regimens. The diagnoses include AML/myelodysplastic syndrome (n=43), non Hodgkin's lymphoma (n=30), Hodgkin's lymphoma (n=3), ALL (n=2) and CML (n=1). For the entire cohort, the disease-free survival (DFS) and OS were 61.2 and 35.7%, respectively. Twenty patients relapsed, 18 within the first three years, and 14 patients succumbed to progressive disease. Overall, 31 patients died from transplant-related complications within the first three years. Day 100 non-relapse mortality correlated with a higher total nucleated cell dose in the graft (odds ratio: 3.9). For those in CR at 3 years, the DFS and OS were 84.2 and 81.1%, respectively. Furthermore, of 43 patients with active disease at the time of transplantation, 16 remained in CR after 3 years. The majority of the long-term survivors were functioning independently. One patient died from a second malignancy. No post-transplant lymphoproliferative disorder was seen. In conclusion, durable disease control was achieved after RIC allogeneic stem cell transplantation for patients with advanced myeloid and lymphoid malignancies.

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.

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.

Risk factors for acute graft-versus-host disease grades II-IV after reduced intensity conditioning allogeneic stem cell transplantation with unrelated donors: a single centre study

We analysed factors associated with moderate to severe acute GVHD in 111 patients treated with fludarabin-based reduced intensity conditioning (RIC) and allogeneic haematopoietic stem cell transplantation (HSCT). Most patients had a haematological malignancy. Donors were 97 HLA-A, -B and -DRbeta1 identical unrelated and 14 HLA-A, -B or -DRbeta1 allele mismatched unrelated donors. In the univariate analysis, we found ten factors associated with acute GVHD. These were diagnosis (P=0.06), GVHD prophylaxis with combinations other than CsA+MTX (P=0.006), graft nucleated (P<0.001) and CD34 (P<0.001) cell-dose, bidirectional ABO mismatch (P=0.001), conditioning (P=0.002), hospital vs home-care (P=0.06), ATG dose (P<0.001), donor herpes virus serology (P=0.07) and an immunized female donor to male recipient (P=0.05). In the multivariate analysis, three factors remained significant: a high CD34 cell dose (P<0.001), low dose (4 mg/kg) ATG (P<0.001), and an immunized female donor to male recipient (P<0.01). Patients receiving a CD34 cell dose > or =17.0 x 10(6) per kg had a higher incidence of GVHD, 53.7%, compared to 22.3% in patients receiving a lower dose (P=0.002). In patients without any of these risk factors (n=70), the incidence of acute GVHD was 14.1%, while it was 38.0 and 85.0% in patients with one (n=29) or two (n=10) risk factors (P<0.001). We concluded that risk factors for acute GVHD using RIC are similar as using myeloablative conditioning.

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.

Subcutaneous alemtuzumab vs ATG in adjusted conditioning for allogeneic transplantation: influence of Campath dose on lymphoid recovery, mixed chimerism and survival

Sixty-nine consecutive patients (median age 54 years) were prospectively enrolled in a single-institution protocol for allogeneic transplantation with adjusted non-myeloablative fludarabine-melfalan-based conditioning including cyclosporin A and MMF, and one of three modes of serotherapy. Thirty-one donors (45%) were unrelated. The first cohort of 29 had ATG (Thymoglobulin 2 mg/kg x 3 days), the subsequent 26 had Campath 30 mg x 3 days subcutaneously, and the final cohort of 14 had 30 mg Campath once. The groups were similar as regards age, diagnosis and risk factors. Campath-patients had no acute toxicity, fewer days with fever and antibiotics, and required fewer transfusions than ATG-treated patients. 3-d-Campath patients showed lower lymphocyte counts from day +4, and CD4+, CD8+, CD19+ and NK cells recovered slower than in ATG-treated patients. More Campath patients developed mixed chimerism that required DLI. 3-d-Campath induced more serious and opportunistic infections than ATG, which resulted in a greater non-relapse mortality and an impaired overall survival despite a low tumor-related mortality. The change of the Campath dosing schedule to one dose abrogated the deleterious effect of 3-d-Campath on immune recovery, severe infections and survival. Subcutaneous Campath is simple and provides strong immune suppression with no early toxicity, but dose limitation to 30 mg once is recommended.

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.

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.

Antithymocyte globulin for the prevention of graft-versus-host disease after unrelated hematopoietic stem cell transplantation for acute myeloid leukemia: results from the multicenter German cooperative study group

A total of 155 patients with acute myeloid leukemia (AML) received hematopoietic stem cell transplants from unrelated donors after standard conditioning. Clinical outcome after the use of two different antithymocyte globulins for the prevention of graft-versus-host disease (GvHD) was analyzed in a retrospective study as follows: rabbit ATG (Thymoglobulin Sangstat/Genzyme, n=49, median age 42 years, 53% in CR, further ATG-S); rabbit ATG (ATG-Fresenius, n=38, median age 42 years, 58% in CR, further ATG-F) or no ATG (n=68, median age 36 years, 55% in CR). The groups were comparable regarding disease status at transplant, age, CMV status and cytogenetics. Grade III-IV acute GvHD was found in 15% in the ATG and 27% in the no ATG group (P=0.44). The most important independent risk factors for chronic GvHD (cGvHD) were the use of ATG, disease status at transplant and conditioning. cGvHD developed significantly more frequently in no ATG group. With the median follow-up of 34 months, the 5-year survival is 42% for those transplanted in CR. To conclude, these data demonstrate that the transplants performed in CR, with ATG, are associated with a good outcome, low incidence of cGvHD and no increase of relapse.

A novel reduced intensity regimen for allogeneic hematopoietic stem cell transplantation associated with a reduced incidence of graft-versus-host disease

SUMMARY

In all, 55 patients at high risk or ineligible for a conventional allogeneic hematopoietic stem cell transplant (HSCT) received a regimen consisting of extracorporeal photopheresis, pentostatin, and reduced dose total body irradiation. The median age was 49 years (18-70 years); 44 received a sibling and 11 an unrelated HSCT; 44% were over the age of 50 years and 31% had undergone a prior HSCT. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine and methotrexate. Full donor chimerism was documented in 98% by day +100. The 1000-day nonrelapse mortality was 11%. The median follow-up is 502 days (154-1104 days). The 1- and 2-year overall survival (OS) and event-free survival (EFS) are 67, 58 and 55%, and 47%, respectively. Patients who had not received a prior HSCT or had less than three prior chemotherapy regimens had a 71% OS and 67% EFS at 1 year. Greater than grade II aGVHD developed in 9% and chronic GVHD (cGVHD) in 43%, and extensive in 12% and limited in 31%. Of the patients, 86% who engrafted had a disease response, 72% had complete and 14% partial responses. This novel reduced intensity preparative regimen was well tolerated and associated with a low incidence of transplant-related mortality and serious acute and cGVHD.

Which donor should be chosen for hematopoietic stem cell transplantation among unrelated HLA-A, -B, and -DRB1 genomically identical volunteers?

The aim of this study was to identify significant prognostic factors by using unrelated genomically HLA-A, -B and -DRB1-identical donors. Such data could help to choose the best donor. We studied 136 consecutive patients with hematologic malignancies and a median age of 32 years (range, 0-55 years) who received hematopoietic stem cell transplantation. Bone marrow grafts were given to 83 and peripheral blood stem cells to 53 patients. The cumulative incidence of grade II to IV acute graft-versus-host disease (GVHD) was 30% and of chronic GVHD was 54%. At 5 years, the overall transplant-related mortality (TRM) was 34%, and patient survival was 50%. In Cox multivariate analysis, 32 potential risk factors were analyzed. Monoclonal antibody OKT-3 during conditioning was correlated with grade II to IV acute GVHD, chronic GVHD, and TRM. HLA-DP mismatch was associated with poor TRM and poor survival. Cytomegalovirus-seropositive patients with a seronegative donor had a decreased leukemia-free survival. Five-year TRM was 14% with no risk factor, 38% with 1 risk factor, and 87% with 2 risk factors. The 5-year survival was 72%, 48%, and 30% with 0, 1, and 2 risk factors, respectively. We concluded that unrelated hematopoietic stem cell transplantation may be improved if an optimal donor and immunosuppression are chosen.

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.

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.

Transplant-related mortality and long-term graft function are significantly influenced by cell dose in patients undergoing allogeneic marrow transplantation

We have studied the impact of cell dose on short- and long-term graft function and outcome in 905 patients undergoing an unmanipulated allogeneic bone marrow transplantation (BMT) from an HLA-identical sibling (n = 735), a one-antigen mismatched related donor (n = 35), or a matched unrelated donor (n = 135). Median number of nucleated cells infused was 3.4 x 10(8)/kg (25th percentile 2.4 x 10(8)/kg, 75th percentile 5 x 10(8)/kg). Patients were stratified according to cells infused in 3 groups: < or = 2.4 x 10(8)/kg (n = 247; low dose); >2.4 x 10(8)/kg and < or = 5 x 10(8)/kg (n = 452; intermediate dose); and >5 x 10(8)/kg (n = 206; high dose). Patients receiving high cell dose had significantly higher platelet counts on days +20, +50, +100, +180, and +365 after BMT (P <.01) and higher white blood cell counts on days +50, +100, and +180 after BMT (P <.01) as compared with other patients. The actuarial 5-year transplant-related mortality (TRM) was 41% versus 36% versus 28% (P =.01); overall survival was 45% versus 51% versus 56% (P =.0008); and disease-free survival was 41% versus 42% versus 48%, respectively, (P =.04) in patients receiving low, intermediate, or high cell dose. The cell dose effect was more pronounced in patients older than 30 years of age, with advanced disease, with chronic myeloid leukemia, and with alternative donors. In multivariate Cox analysis on TRM, cell dose was a significant predictor (P =.002; relative risk 0.6) together with donor type (P =.0001), year of transplantation (P =.0001), conditioning regimen (P =.02), and recipient age (P =.02). In conclusion, transplantation of high marrow cell dose is associated with reduced transplant mortality and improved survival and results in improved graft function both short and long term.

Unrelated donor BMT recipients given pretransplant low-dose antithymocyte globulin have outcomes equivalent to matched sibling BMT: a matched pair analysis

Fifty-seven patients receiving unrelated donor (UD) BMT were matched for disease and stage with 57 recipients of genotypically matched related donor (MRD) BMT. All UD recipients were matched serologically for A and B and by high resolution for DR and DQ antigens. All patients received CsA and 'short course' methotrexate with folinic acid. Unrelated donor BMT patients also received thymoglobulin 4.5 mg/kg (6 mg/kg if <30 kg) in divided doses over 3 days pretransplant. For UD and RD BMT, respectively, incidence of acute GVHD grade II-IV was 19 +/- 6% vs 36 +/- 8%, grade III-IV 10 +/- 6% vs 18 +/- 7%, chronic GVHD 44 +/- 8% vs 51 +/- 8%, non-relapse mortality 15 +/- 5% vs 8 +/- 4% at 100 days, 28 +/- 8% vs 36 +/- 7% at 3 years. At 3 years, relapse was 45 +/- 7% vs 42 +/- 7%, and disease-free survival 39 +/- 7% vs 37 +/- 7%. None of these differences are significant. Three-year overall survival was identical at 42 +/- 7%. For 29 patients with low/intermediate risk leukemia, disease-free survival was 68 +/- 10% after UD BMT vs 59 +/- 9% for RD BMT recipients (P = NS). Corresponding figures for high risk patients were 14 +/- 7% and 21 +/- 8%, respectively. We conclude that UD BMT recipients matched as above and given pretransplant ATG have similar outcomes to recipients of MRD BMT using conventional drug prophylaxis. Unrelated donor BMT should be considered in any circumstance where MRD BMT is routine.

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.

Peripheral blood but not tissue dendritic cells express CD52 and are depleted by treatment with alemtuzumab

CAMPATH antibodies recognize CD52, a phosphatidylinositol-linked membrane protein expressed by mature lymphocytes and monocytes. Since some antigen-presenting dendritic cells (DCs) differentiate from a monocytic progenitor, we investigated the expression of CD52 on dendritic cell subsets. Four-color staining for lineage markers (CD3, 14, 16, 19, 20, 34, and 56), HLA-DR, CD52, and CD123 or CD11c demonstrated that myeloid peripheral blood (PB) DCs, defined as lineage−HLA-DR+CD11c+, express CD52, while expression by CD123+ lymphoid DCs was variable. Depletion of CD52+ cells from normal PB strongly inhibited their stimulatory activity in an allogeneic mixed lymphocyte reaction and also reduced the primary autologous response to the potent neoantigen keyhole limpet hemocyanin. CD52 is thus expressed by a myeloid subset of PBDCs that is strongly allostimulatory and capable of initiating a primary immune response to soluble antigen. Administration of alemtuzumab, a humanized monoclonal antibody against CD52, to patients with lymphoproliferative disorders or as conditioning for hematopoietic stem cell transplantation resulted in a marked reduction in circulating lineage−HLA-DR+ DCs (mean 31-fold reduction,P = .043). Analysis of monocyte-derived DCs in vitro revealed a reduction in CD52 expression during culture in granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4, with complete loss following activation-induced maturation with lipopolysaccharide. In contrast to the findings in PB, epidermal and small-intestine DCs did not express CD52, suggesting either that transit from blood to epidermis and gut is associated with loss of CD52 or that DCs in these tissues originate from another population of cells.

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.

Bone marrow transplantation for beta-thalassaemia major by an HLA-mismatched parent

A six-year-old boy was diagnosed with beta-thalassaemia major during infancy. Since then, he required monthly blood transfusion and irregular iron chelation therapy. He had hepatosplenomegaly and elevated liver enzymes; the serum ferritin was up to 3800 ng/mL. An echocardiogram showed left-ventricular enlargement. His one-antigen-mismatched mother was chosen as a bone marrow donor. He was pretreated with intensive red blood cell transfusion and hydroxyurea for 6 weeks prior to conditioning. The conditioning included total body irradiation (300 cGy), busulfan (14 mg/kg), cyclophosphamide (160 mg/kg) and anti-thymocyte globulin (rabbit; 90 mg/kg). Marrow cell dose was 5.4 x 108/kg. Graft versus host disease (GVHD) prophylaxis included cyclosporine A (CSA) and methylprednisolone. Neutrophil engraftment occurred on day 23. Grade II acute GVHD occurred on day 45. The patient developed complications including septicaemia, haemorrhagic cystitis, intracranial haemorrhage and heart failure. He subsequently recovered from the complications without sequelae. The patient remained transfusion-independent at a follow-up examination after 18 months. This case suggested that a mismatched family member may be considered as a bone marrow donor for beta-thalassaemia major. In places where conventional treatment is not feasible, for example, in China, this approach may be an alternative option. A more intensive immunosuppressive regimen and a higher marrow cell dose may be important for successful engraftment. High-dose anti-thymocyte globulin may also prevent severe GVHD.

Campath-1G causes rapid depletion of circulating host dendritic cells (DCs) before allogeneic transplantation but does not delay donor DC reconstitution

Graft-versus-host disease (GVHD), a major complication after allogeneic transplantation, can be abrogated by the Campath (anti-CD52) monoclonal antibody. The induction of acute GVHD requires host antigens to be presented to donor T cells by antigen-presenting cells (APCs). Recent evidence has suggested that only host APCs can interact with donor T cells in the induction of GVHD. Because CD52 has been reported to be expressed on DCs, we reasoned that pretransplant Campath-1G might have a direct effect on circulating DCs in addition to any effects on donor T cells. Using direct immunostaining, we demonstrated expression of CD52 on DCs and that Campath-1G killed purified DCs in vitro. In vivo Campath also depleted DCs. Twenty-four hours after the first dose of Campath-1G, circulating DCs were reduced by a mean of 79% (range, 44%-96%). By day 0 after 5 doses of Campath-1G and chemoradiotherapy conditioning, DCs became undetectable in 7 of 9 cases, whereas in 6 of 7 patients receiving conditioning therapy without Campath-1G, host DCs were still detectable. The reconstitution of circulating DCs after transplantation was not affected by Campath-1G and in both groups DC1 (CD11c(+)) recovered more rapidly than DC2 (CD11c(-)). Analysis of chimerism confirmed that the DCs recovering after transplantation in patients receiving Campath-1G were of donor origin. We conclude that in vivo Campath-1G causes a rapid depletion of host circulating DCs and that this may, in part, explain the low incidence of acute GVHD. The reconstitution of donor DCs was not delayed, which may be important in preserving immune reconstitution.

Second hematopoietic stem cell transplantation for the treatment of graft failure, graft rejection or relapse after allogeneic transplantation

Failure to engraft after hematopoietic stem cell transplantation (graft dysfunction) or to sustain engraftment (graft rejection) is a formidable complication due to many possible factors. These include inadequate stem cell numbers, infections, graft-versus-host disease and immunological mediated processes. Fortunately, this complication is uncommon and can be overcome by additional hematopoietic stem cell infusions. Multiple treatment alternatives have been explored including hematopoietic growth factors, additional infusions of stem cells alone, with augmented immunosuppression or with additional cytotoxic therapy. Various sources of the additional stem cells are feasible including the original donor, using another donor, using stem cells collected from the marrow or after cytokine mobilization from the peripheral blood. This report will overview this complication and review the various studies that have attempted to define both cause and therapy. However, a lack of well-designed prospective studies has made definitive recommendations difficult although basic principles have been established.

Association between pretransplant Thymoglobulin and reduced non-relapse mortality rate after marrow transplantation from unrelated donors

A matched cohort study was designed to test the efficacy of polyclonal rabbit antiserum specific for human T cells (Thymoglobulin), administered in vivo on days 1-5 (2 mg/kg/day) before T cell-replete unrelated donor marrow transplantation. Thymoglobulin was given to 52 leukemic patients at Huddinge Hospital. Control patients matched for diagnosis, disease stage, age and treated with a similar regimen, apart from the omission of Thymoglobulin, were selected in Seattle during the same period (n = 104). All received conditioning with cyclophosphamide and TBI. In the study group all patients received 10 Gy single dose TBI, while the controls were given 12-14.4 Gy fractionated TBI. GVHD prophylaxis was cyclosporine and methotrexate. Patients were treated for grade I acute GVHD in the study group, and for grade II GVHD in the control group. Multivariable analyses were adjusted for patient and donor age and CMV serology, HLA matching, donor gender and marrow cell dose. Non-relapse mortality was lower in the study patients (hazard ratio = 0.30, 95% CI 0.12-0.75, P value = 0.005). The 5-year cumulative incidence of non-relapse mortality was 19% in the study cohort, and 35% in the control cohort. Overall mortality was also lower in study patients (hazard ratio 0.51, 95% CI 0.27-0.97, P value = 0.03). No significant difference in the risk of relapse was seen (P = 0.63). This suggests that Thymoglobulin during conditioning may reduce non-relapse mortality after unrelated donor marrow transplantation.

Allogeneic transplantation using peripheral blood stem cells

Over the past 9 years there has been a remarkable increase in the use of peripheral blood stem cells (PBSC) for allogeneic transplantation, primarily for matched sibling transplants but also increasingly for unrelated donor transplantation. In 1999 over 50% of all sibling transplants and over 25% of unrelated donor transplants reported to the European Group for Blood and Marrow Transplantation (EBMT) used PBSC. The major reason for this increasing use of PBSC relates to the rapid haemopoietic recovery seen which mirrors the advantages of using PBSC in autologous transplantation. This improvement in engraftment is a consequence of the larger number of stem cells that can be collected from G-CSF-mobilized peripheral blood compared to bone marrow. Evidence from randomized trials now shows a survival advantage for the use of PBSC in patients with advanced leukaemia. The reason for this improved survival appears primarily to relate to a reduced risk of transplant-related mortality and, possibly, a reduced risk of relapse, However, these randomized studies have also confirmed that there is an increased risk of chronic graft-versus-host disease associated with PBSC transplantation and further follow-up is required to determine the long-term impact on outcome.

Naso-jejunal feeding in allogeneic bone marrow transplant recipients: results of a pilot study

Patients undergoing allogeneic bone marrow transplants (BMT) are often malnourished prior to commencing the procedure. They face intensive treatment with often marked nutritional consequences. There is no consensus on the optimal nutritional management of these patients. Elective parenteral nutrition (PN), beginning pre-transplant irrespective of the patients nutritional status, or the use of "salvage" PN, beginning during the post-transplant period if the patient fails to maintain nutritional status with oral diet, have been used. Enteral nutrition may benefit the patient by maintaining nutritional support throughout the transplant period, avoiding the complications and expense of PN and possibly, by using specific diets, protecting the gastrointestinal tract from the effects of chemoradiation. However, naso-gastric feeding during a transplant is not without risks, including the safe insertion of a tube in patients with mucositis and pan-cytopenias, tube displacement by vomiting and aspiration from gastro-oesophageal reflux. An alternative approach is to use naso-jejunal (NJ) feeding tubes which are associated with less risk of loss due to vomiting and less risk of aspiration. We report a pilot study of 15 allogeneic BMT patients who had elective NJ feeding initiated before conditioning therapy irrespective of perceived nutritional compromise. This was well tolerated and feasible with a motivated nutritional team.

Antithymocyte globulin for graft-versus-host disease prophylaxis in transplants from unrelated donors: 2 randomized studies from Gruppo Italiano Trapianti Midollo Osseo (GITMO)

One hundred nine patients with hematologic malignancies, undergoing bone marrow transplants (BMT) from unrelated donors, were randomized in 2 consecutive trials to receive or not to receive antithymocyte globulin (ATG) in the conditioning regimen, as follows: (A) 54 patients (median age, 28 years; 39% with advanced disease) were randomized to no ATG (n = 25) versus 7.5 mg/kg rabbit ATG (Thymoglobulin; Sangstat, Lyon, France) (n = 29); (B) 55 patients (median age, 31 years, 71% with advanced disease) were randomized to no ATG (n = 28) versus 15 mg/kg rabbit ATG (n = 27). Grade III-IV graft-versus-host disease (GVHD) was diagnosed in 36% versus 41% (P =.8) in the first and in 50% versus 11% (P =.001) in the second trial. Transplant-related mortality (TRM), relapse, and actuarial 3-year survival rates were comparable in both trials. In fact, despite the reduction of GVHD in the second trial, a higher risk for lethal infections (30% vs 7%; P =.02) was seen in the arm given 15 mg/kg ATG. Extensive chronic GVHD developed overall more frequently in patients given no ATG (62% vs 39%; P =.04), as confirmed by multivariate analysis (P =.03). Time to 50 x 10(9)/L platelets was comparable in the first trial (21 vs 24 days; P =.3) and delayed in the ATG arm in the second trial (23 vs 38 days; P =.02). These trials suggest that (1) 15 mg/kg ATG before BMT significantly reduces the risk for grade III-IV acute GVHD, (2) this does not translate to a reduction in TRM because of the increased risk for infections, and (3) though survival is unchanged, extensive chronic GVHD is significantly reduced in patients receiving ATG.

Jurkat cell-reactive anti-thymocyte globulin assessed ex vivo by flow cytometry persists three weeks in circulation

Rabbit anti-thymocyte globulin (ATG-Fresenius) is a polyclonal anti-serum raised against the lymphoblastic T cell line Jurkat. It is used for in vivo depletion of host and donor T cells for allogeneic stem cell transplantation. After administration of 90 mg/kg prior to transplant, rabbit immunoglobulin G (IgG) remains present for 4-5 weeks, but it is unknown how long T cell-reactive antibodies persist. Therefore, we measured anti-Jurkat antibodies by flow cytometry. The detection limit for Jurkat-reactive antibodies was 0.1 microg/ml rabbit IgG; half-maximal labeling of Jurkat cells required 183 microg/ml rabbit ATG. The mean half-life of Jurkat-reactive antibodies in 7 patients was 4 days. Detectable levels persisted up to 3 weeks with antibody levels equivalent to 0.2-4.1 microg/ml rabbit ATG. Jurkat-reactive antibodies were eliminated two-fold faster than rabbit IgG, as assessed by enzyme-linked immunosorbent assay (ELISA). The results suggest that in patients pretreated with ATG before transplantation, residual anti T-cell antibodies may effectively modulate recovery of T cells generated after transplantation, thereby lowering the incidence of severe GVHD.

Patient cytomegalovirus seropositivity with or without reactivation is the most important prognostic factor for survival and treatment-related mortality in stem cell transplantation from unrelated donors using pretransplant in vivo T-cell depletion with anti-thymocyte globulin

We evaluated the cytomegalovirus (CMV) serostatus as a risk factor for survival and treatment-related mortality (TRM) in 125 patients allografted from an unrelated donor between 1994 and 1999. All patients received pretransplant in vivo T-cell depletion using rabbit anti-thymocyte globulin (ATG). Only one patient had primary graft failure and severe grade III/IV graft-versus-host disease occurred in 14% of the patients. The overall survival (OS) at 3 years was 70% for CMV-negative patients (n = 76) and 29% in the seropositive cohort (n = 49) (P > 0.001). In multivariate analyses, CMV seropositivity remained an independent negative prognostic factor for OS (RR: 2.1; CI: 1.2-3.8; P = 0.014), apart from age > 20 years (RR: 2.74; CI: 1.2-3.8; P = 0.004) and late leucocyte engraftment (RR: 2.4; CI: 1.2-4.9; P = 0.015). The TRM for all patients was 27%. Despite monitoring for CMV antigenaemia and preemptive therapy with ganciclovir when reactivation occurred, seropositive patients had a three times higher risk of fatal treatment-related complications than seronegative patients. In multivariate analyses, CMV seropositivity remained the strongest independent negative factor for TRM (RR: 5.3; CI: 1.9-14.6; P = 0.002), followed by age > 20 years (RR: 4.8; CI: 1.3-18.1; P = 0.02) and delayed leucocyte engraftment (RR: 3.6; CI: 1.2-11; P = 0.02). The TRM was identical in seropositive patients with (n = 27) or without (n = 22) CMV reactivation (44% versus 50%). We conclude that CMV seropositivity, despite preemptive ganciclovir therapy and even without reactivation, is a major negative prognostic factor for survival as well as for TRM in unrelated stem cell transplantation using pretransplant in vivo T-cell depletion with ATG.