Pharmacokinetics of CAMPATH-1H in BMT patients

Early recovery of natural killer cells post T-cell depleted allogeneic stem cell transplantation using alemtuzumab "in the bag"

BACKGROUND

Allogeneic stem cell transplantation (SCT) is a critical therapy for haematological malignancy but may lead to acute and chronic graft versus host disease (GvHD). T-cell depletion with alemtuzumab, either in vivo or ex vivo, reduces the incidence of GvHD but is a risk factor for disease relapse and poor immune reconstitution. Natural killer (NK) cells are the first lymphocytes to recover. Classical NK cells make up >90% of the normal circulating population and can directly kill neoplastic or virally infected cells while the regulatory subset makes up <10%, secretes cytokines and is not cytotoxic. The recovery and balance of these subsets post SCT remains controversial, with most studies analysing patients who received unmanipulated grafts and in vivo immunosuppression.

OBJECTIVE

The aim was to assess the early recovery of NK cells in 18 consecutive patients receiving ex vivo T-cell depleted SCT and to compare the results to 25 individuals receiving haploidentical non-T cell depleted grafts.

METHODS

All patients received myeloablative conditioning. After stem cell collection, the stem cells of the T cell depleted group were treated "in the bag" with alemtuzumab (CAMPATH 1H) at a concentration of 1mg/108 mononuclear cells and thereafter immediately infused. For those receiving non-T cell depleted grafts, GvHD prophylaxis was with post infusion therapeutic doses of cyclophosphamide. Blood samples were collected at days 21, 28 and 90. Complete blood counts were performed on an automated analyser while lymphocyte and NK subsets were examined using multiparameter flowcytometry. NK cells were defined as lymphocytes which were CD3-/CD56+. The classical subset was recognised as CD56dim/CD16+ while the regulatory population as CD56bright/CD16-. The results for both transplant types were compared at all time points using SPSS v8 statistical software.

RESULTS

The recovery of lymphocytes was slow in both groups. Those receiving non-T cell depleted grafts had significantly higher T cell counts at day 21 and 28 when compared to the T cell depleted group (P < 0.05). In contrast, NK cells in the ex vivo T-cell depleted patients recovered rapidly and by day 21 was no different to normal (p > 0.05), while the non-T cell depleted group had significantly decreased numbers (p < 0.001), only recovering at day 90. Both groups had abnormal NK cell subset ratios with significantly elevated percentages of regulatory cells (p < 0.05). However, significant differences were observed between the two groups with those receiving T cell depleted grafts having lower percentages of regulatory cells as well as higher numbers of classical NK cells at day 21 and 28 (p < 0.01).

CONCLUSION

This study of ex vivo T-cell depleted SCT's demonstrates that NK cells recover quicker when compared to those receiving unfractionated grafts. These results may have implications for GvHD and the GvL effect which warrants further study.

The role of graft T-cell size in patients receiving alemtuzumab serotherapy for non-malignant disorders: results of an institutional protocol

Although graft T cells assist in engraftment, mediate antiviral immune-reconstitution, and cause graft-versus-host disease, graft size is not determined by T-cell content of the graft. The conventional method of graft size determination based on CD34+ cells with alemtuzumab serotherapy is associated with delayed immune reconstitution, contributing to an increased risk of viral infections and graft failure. Alemtuzumab, a long half-life anti-CD52 monoclonal antibody is a robust T-cell depleting serotherapy, and relatively spares memory-effector T cells compared to naïve T cells. We therefore hypothesized that graft size based on T-cell content in patients receiving peripheral blood stem cell graft with alemtuzumab serotherapy would facilitate immune-reconstitution without increasing the risk of graft-versus-host disease. We retrospectively analysed twenty-six consecutive patients with non-malignant disorders grafted using alemtuzumab serotherapy and capping of graft T cells to a maximum of 600 million/kg. The graft T-cell capping protocol resulted in early immune-reconstitution without increasing the risk of severe graft-versus-host disease. Graft T-cell content correlated with CD4+ T-cell reconstitution and acute graft-versus-host disease. The course of CMV viraemia was predictable without recurrence and associated with early T-cell recovery. No patient developed chronic graft-versus-host disease. Overall survival at one year was 100% and disease-free survival was 96% at a median of 899 days (range: 243-1562). Graft size determined by peripheral blood stem cell graft T-cell content in patients receiving alemtuzumab serotherapy for non-malignant disorders is safe and leads to early T-cell immune-reconstitution with excellent survival outcomes.

Exposure-response analysis of alemtuzumab in pediatric allogeneic HSCT for nonmalignant diseases: the ARTIC study

Alemtuzumab (anti-CD52 antibody) is frequently prescribed to children with nonmalignant diseases undergoing allogeneic hematopoietic stem cell transplantation (HSCT) to prevent graft failure (GF) and acute graft-versus-host disease (aGVHD). The aim of this multicenter study was the characterization of alemtuzumab population pharmacokinetics to perform a novel model-based exposure-response analysis in 53 children with nonmalignant immunological or hematological disease and a median age of 4.4 years (interquartile range [IQR], 0.8-8.7). The median cumulative alemtuzumab dose was 0.6 mg/kg (IQR, 0.6-1) administered over 2 to 7 days. A 2-compartment population pharmacokinetics model with parallel linear and nonlinear elimination including allometrically scaled bodyweight (median, 17.50 kg; IQR, 8.76-33.00) and lymphocyte count at baseline (mean, 2.24 × 109/L; standard deviation ± 1.87) as significant pharmacokinetic predictors was developed using nonlinear mixed effects modeling. Based on the model-estimated median concentration at day of HSCT (0.77 μg/mL; IQR, 0.33-1.82), patients were grouped into a low- (≤0.77 μg/mL) or high- (>0.77 μg/mL) exposure groups. High alemtuzumab exposure at day of HSCT correlated with delayed CD4+ and CD8+ T-cell reconstitution (P value < .0001) and increased risk of GF (P value = .043). In contrast, alemtuzumab exposure did not significantly influence the incidence of aGVHD grade ≥2, mortality, chimerism at 1 year, viral reactivations, and autoimmunity at a median follow-up of 3.3 years (IQR, 2.5-8.0). In conclusion, this novel population pharmacokinetics model is suitable for individualized intravenous precision dosing to predict alemtuzumab exposure in pediatric allogeneic HSCT for nonmalignant diseases, aiming at the achievement of early T-cell reconstitution and prevention of GF in future prospective studies.

Development and Validation of an Efficient and Highly Sensitive Enzyme-Linked Immunosorbent Assay for Alemtuzumab Quantification in Human Serum and Plasma

BACKGROUND

Alemtuzumab is a humanized monoclonal antibody that targets the CD52 glycoprotein expressed on most lymphocytes, subsequently inducing complement-mediated and antibody-mediated cytotoxicity. Owing to its ability to induce profound immune depletion, alemtuzumab is frequently used in patients before allogeneic hematopoietic stem cell transplantation to prevent graft rejection and acute graft-versus-host disease. In this clinical context, a stable immunoassay with high sensitivity and specificity to determine alemtuzumab levels is essential for performing pharmacokinetic and pharmacodynamic analyses; however, the available methods have several limitations. Here, we report the successful development and validation of an efficient and highly sensitive enzyme-linked immunosorbent assay technique based on commercially available reagents to quantify alemtuzumab in human serum or plasma.

METHODS

This enzyme-linked immunosorbent assay technique was developed and validated in accordance with the European Medicines Agency guidelines on bioanalytical method validation.

RESULTS

The assay sensitivity (lower limit of quantification) is 0.5 ng·mL -1 , and the dynamic range is 0.78-25 ng·mL -1 . To accommodate quantification of peak concentration and concentrations below the lympholytic level (<0.1 mcg·mL -1 ), patients' serum samples were prediluted 20-400 times according to the expected alemtuzumab concentration. The overall within-run accuracy was between 96% and 105%, whereas overall within-run precision (coefficient of variation) was between 3% and 9%. The between-run assessment provided an overall accuracy between 86% and 95% and an overall coefficient of variation between 5% and 14%.

CONCLUSIONS

The developed assay provides accurate insight into alemtuzumab exposure and its effects on the clinical response to treatment, which is key to optimizing treatment strategies.

Alemtuzumab clearance, lymphocyte count, and T-cell chimerism after hematopoietic stem cell transplant in sickle cell disease

STUDY OBJECTIVE

Alemtuzumab is a monoclonal antibody that targets the cell surface antigen CD52 on lymphocytes. Although it is used for the treatment of hematologic malignancies, such as chronic lymphocytic leukemia, and incorporated into many hematopoietic stem cell transplant (HSCT) conditioning regimens, few studies have evaluated the pharmacology of alemtuzumab in adult patients with sickle cell disease (SCD). We therefore examined the pharmacokinetics (PK) and pharmacodynamics (PD) of alemtuzumab in adults with SCD who received a matched related donor HSCT to determine if the clearance of alemtuzumab affects transplant outcomes.

DESIGN

PK and PD analysis of patient data from a single-center clinical trial.

SETTING

Clinical research center.

PATIENTS

Twenty-two adult patients with SCD who received one of two nonmyeloablative allogeneic HSCT regimens: alemtuzumab and total body irradiation (Alem-TBI) or pentostatin, cyclophosphamide, alemtuzumab, and total body irradiation (Pento-Cy-Alem-TBI).

MEASUREMENTS AND MAIN RESULTS

Alemtuzumab serum concentrations, absolute lymphocyte counts, T-cell (CD3), and myeloid (CD14/15) chimerism were collected at distinct time points and analyzed. A semi-mechanistic PK population model was built to understand inter-individual differences in pharmacology. Alemtuzumab was detectable up to 28 days post-HSCT. The mean alemtuzumab level 7 days after transplant for patients on Alem-TBI was 818 ng/ml, significantly lower than the mean level of 1502 ng/ml for patients on Pento-Cy-Alem-TBI (p < 0.001), but this difference decreased as time progressed. The clearance of alemtuzumab was linear, and the half-life was longer in the Pento-Cy-Alem-TBI group (average half-life = 61.1 h) compared to the Alem-TBI group (average half-life = 44.1 h) (p < 0.001). The CD3 chimerism at 2 and 4 months after transplant positively correlated with alemtuzumab levels collected on day 14 after transplant (R²  = 0.40 and p = 0.004 at 2 months, R²  = 0.36 and p = 0.005 at 4 months), but this significance was lost by 6 months after HSCT. No correlation was seen between alemtuzumab levels and CD14/15 chimerism.

CONCLUSION

Between 2 and 4 months after transplant, higher alemtuzumab levels measured 14 days after transplant correlated with patients having better engraftment, suggesting more lymphodepletion may be needed to reduce graft failure in these two non-myeloablative matched related donor HSCT regimens.

Pharmacokinetics of alemtuzumab in pediatric patients undergoing ex vivo T-cell-depleted haploidentical hematopoietic cell transplantation

PURPOSE

Alemtuzumab is a humanized monoclonal antibody against CD52 which is predominantly present on T and B lymphocytes. Alemtuzumab has been used as part of conditioning regimens for prophylaxis against rejection and GVHD. While the mechanism of action is well understood, the pharmacokinetics of this drug in children needed to be studied in more detail especially in the setting of ex vivo T-cell-depleted hematopoietic cell transplantation (HCT).

METHODS

Serum alemtuzumab levels were measured at various time points in 13 patients who underwent haploidentical HCT utilizing ex vivo donor T-cell depletion. Alemtuzumab was administered subcutaneously at a cumulative dose of 45 mg/m² from days - 13 to - 11. A one-compartmental model was used to fit the data using non-linear mixed effects modeling.

RESULTS

We determined the median half-life to be 11 days. Alemtuzumab clearance increased with increasing baseline lymphocyte count (p = 0.008). Additionally, clearance increased with weight and age (p ≤ 0.035). AUC of alemtuzumab did not have any significant relationship with type of leukemia, overall survival, engraftment, immune reconstitution, mixed chimerism or GVHD, although the number of subjects in this pilot study was limited.

CONCLUSION

Absolute lymphocyte count and body weight affect alemtuzumab clearance. We also demonstrate feasibility of body-surface area-based dosing of alemtuzumab in pediatric HCT patients. Further studies are needed to evaluate the role of monitoring alemtuzumab serum concentrations to balance the prevention of graft rejection and GVHD with the promotion of rapid donor immune reconstitution.

Population Pharmacokinetics of Alemtuzumab (Campath) in Pediatric Hematopoietic Cell Transplantation: Towards Individualized Dosing to Improve Outcome

BACKGROUND AND OBJECTIVE

Alemtuzumab (Campath^®) is used to prevent graft-versus-host disease and graft failure following pediatric allogeneic hematopoietic cell transplantation. The main toxicity includes delayed immune reconstitution, subsequent viral reactivations, and leukemia relapse. Exposure to alemtuzumab is highly variable upon empirical milligram/kilogram dosing.

METHODS

A population pharmacokinetic (PK) model for alemtuzumab was developed based on a total of 1146 concentration samples from 206 patients, aged 0.2-19 years, receiving a cumulative intravenous dose of 0.2-1.5 mg/kg, and treated between 2003 and 2015 in two centers.

RESULTS

Alemtuzumab PK were best described using a two-compartment model with a parallel saturable and linear elimination pathway. The linear clearance pathway, central volume of distribution, and intercompartmental distribution increased with body weight. Blood lymphocyte counts, a potential substrate for alemtuzumab, did not impact clearance.

CONCLUSION

The current practice with uniform milligram/kilogram doses leads to highly variable exposures in children due to the non-linear relationship between body weight and alemtuzumab PK. This model may be used for individualized dosing of alemtuzumab.

Differential Interaction of Peripheral Blood Lymphocyte Counts (ALC) With Different in vivo Depletion Strategies in Predicting Outcomes of Allogeneic Transplant: An International 2 Center Experience

Dosing regimens for antithymocyte globulin (ATG) and anti-CD52 antibody (alemtuzumab) for graft vs. host disease prophylaxis (GVHD) are empiric or weight-based, and do not account for individual patient factors. Recently, it has been shown that recipient peripheral blood absolute lymphocyte count (ALC) on the day of ATG administration interacts with the dose of ATG administered to predict transplantation outcome. Similarly, we wanted to analyze if the recipient ALC interacts with alemtuzumab dosing to predict outcomes. We retrospectively compared 364 patients, 124 patients receiving ATG (anti-thymocyte globulin) for GVHD prophylaxis, and undergoing unrelated first allogeneic transplant for myeloid and lymphoid malignancies (group 1) to 240 patients receiving alemtuzumab (group 2), in similar time period. There was no difference in survival or acute and chronic GVHD between 60 and 100 mg of alemtuzumab dosing. Unlike ATG (where the pre-transplant recipient ALC interacted with ATG dose on day of its administration (day 1) to predict OS and DFS (p = 0.05), within alemtuzumab group, the recipient ALC on second day of alemtuzumab administration (day 2) and its interaction with alemtuzumab dose strongly predicted OS, DFS and relapse (p = 0.05, HR-1.81, 1.1–3.3; p = 0.002, HR-2.41, CI, 1.3–4.2; and p = 0.003, HR-2.78, CI, 1.4–5.2), respectively. ALC (day 2) of 0.08 × 10⁹/lit or higher, had a specificity of 96% in predicting inferior DFS. Like ATG, there is definite but differential interaction between the recipient peripheral blood ALC and alemtuzumab dose to predict OS, DFS, and relapses.

Reduced-intensity conditioning for hematopoietic cell transplant for HLH and primary immune deficiencies

Allogeneic hematopoietic cell transplantation (HCT) with myeloablative conditioning for disorders associated with excessive inflammation such as hemophagocytic lymphohistiocytosis (HLH) is associated with early mortality. A multicenter prospective phase 2 trial of reduced-intensity conditioning with melphalan, fludarabine, and intermediate-timing alemtuzumab was conducted for HLA matched or single HLA locus mismatched related or unrelated donor HCT in a largely pediatric cohort. Graft-versus-host disease (GVHD) prophylaxis was cyclosporine with methylprednisolone. The primary end point was 1-year overall survival (OS). Thirty-four patients with HLH and 12 with other primary immune deficiencies were transplanted. With a median follow-up of 20 months, the 1-year OS for transplanted patients was 80.4% (90% confidence interval [CI], 68.6%-88.2%). Five additional deaths by 16 months yielded an 18-month OS probability of 66.7% (90% CI, 52.9%-77.3%). Two patients experienced primary graft failure, and 18 patients either experienced a secondary graft failure or required a second intervention (mostly donor lymphocyte infusion [DLI]). At 1 year, the proportion of patients alive with sustained engraftment without DLI or second HCT was 39.1% (95% CI, 25.2%-54.6%), and that of being alive and engrafted (with or without DLI) was 60.9% (95% CI, 45.4 %-74.9%). The day 100 incidence of grade II to IV acute GVHD was 17.4% (95% CI, 8.1%-29.7%), and 1-year incidence of chronic GVHD was 26.7% (95% CI, 14.6%-40.4%). Although the trial demonstrated low early mortality, the majority of surviving patients required DLI or second HCT. These results demonstrate a need for future approaches that maintain low early mortality with improved sustained engraftment. The trial was registered at Clinical Trials.gov (NCT 01998633).

Principles of alemtuzumab immunoablation in hematopoietic cell transplantation for non-malignant diseases in children: A review

Alemtuzumab is a humanized mAb targeted to CD52. Alemtuzumab is highly immunosuppressive with the ability to deplete T and B cells (in addition to other immune cell lines). A growing understanding of the PKs, dosing, and timing of administration of alemtuzumab has allowed for the study of its use as a conditioning agent for allogeneic HCT. The highly immunosuppressive properties of the drug are particularly appealing in the setting of non-malignant HCT, where GVHD provides no clinical benefit and relapse of malignancy is not applicable. In addition, the degree of immune suppression achieved with alemtuzumab has allowed for a reduction in the intensity of myeloablative cytotoxic agents included in some HCT conditioning regimens, allowing for fewer acute and late toxicities. This review paper will provide a comprehensive summary of the mechanism of action, PKs, dosing, and timing of alemtuzumab, a brief description of its use in various allogeneic HCT protocols for non-malignant conditions and a summary of the data regarding its use for GVHD therapy. The goal of this review was to provide an understanding as to how alemtuzumab might be safely incorporated into HCT conditioning regimens for children with non-malignant disease, allowing for expanded access to curative HCT therapy.

Review of the Clinical Pharmacokinetics and Pharmacodynamics of Alemtuzumab and Its Use in Kidney Transplantation

Alemtuzumab is a humanized monoclonal antibody against CD52 and causes depletion of T and B lymphocytes, monocytes, and NK cells. Alemtuzumab is registered for the treatment of multiple sclerosis (MS) and is also used in chronic lymphocytic leukemia (CLL). Alemtuzumab is used off-label in kidney transplantation as induction and anti-rejection therapy. The objective of this review is to present a review of the pharmacokinetics, pharmacodynamics, and use of alemtuzumab in kidney transplantation. A systematic literature search was conducted using Ovid Medline, Embase, and Cochrane Central Register of controlled trials. No pharmacokinetic or dose-finding studies of alemtuzumab have been performed in kidney transplantation. Although such studies were conducted in patients with CLL and MS, these findings cannot be directly extrapolated to transplant recipients, because CLL patients have a much higher load of CD52-positive cells and, therefore, target-mediated clearance will differ between these two indications. Alemtuzumab used as induction therapy in kidney transplantation results in a lower incidence of acute rejection compared to basiliximab therapy and comparable results as compared with rabbit anti-thymocyte globulin (rATG). Alemtuzumab used as anti-rejection therapy results in a comparable graft survival rate compared with rATG, although infusion-related side effects appear to be less. There is a need for pharmacokinetic and dose-finding studies of alemtuzumab in kidney transplant recipients to establish the optimal balance between efficacy and toxicity. Furthermore, randomized controlled trials with sufficient follow-up are necessary to provide further evidence for the treatment of severe kidney transplant rejection.

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

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

Greatly reduced risk of EBV reactivation in rituximab-experienced recipients of alemtuzumab-conditioned allogeneic HSCT

EBV-associated post-transplant lymphoproliferative disease (PTLD) remains an important complication of allogeneic haematopoietic stem cell transplantation (allo-HSCT). We retrospectively analysed the incidence and risk factors for EBV reactivation in 186 adult patients undergoing consecutive allo-HSCT with alemtuzumab T-cell depletion at a single centre. The cumulative incidence of EBV reactivation was 48% (confidence interval (CI) 41-55%) by 1 year, with an incidence of high-level EBV reactivation of 18% (CI 13-24%); 8 patients were concurrently diagnosed with PTLD. Amongst patients with high-level reactivation 31/38 (82%) developed this within only 2 weeks of first EBV qPCR positivity. In univariate analysis age⩾50 years was associated with significantly increased risk of EBV reactivation (hazard ratio (HR) 1.54, CI 1.02-2.31; P=0.039). Furthermore, a diagnosis of non-Hodgkin lymphoma (NHL) was associated with greatly reduced risk of reactivation (HR 0.10, CI 0.03-0.33; P=0.0001) and this was confirmed in multivariate testing. Importantly, rituximab therapy within 6 months prior to allo-HSCT was also highly predictive for lack of EBV reactivation (HR 0.18, CI 0.07-0.48; P=0.001) although confounding with NHL was apparent. Our data emphasise the risk of PTLD associated with alemtuzumab. Furthermore, we report the clinically important observation that rituximab, administered in the peri-transplant period, may provide effective prophylaxis for PTLD.

Alemtuzumab levels impact acute GVHD, mixed chimerism, and lymphocyte recovery following alemtuzumab, fludarabine, and melphalan RIC HCT

Reduced intensity conditioning (RIC) allogeneic hematopoietic cell transplantation (HCT) with alemtuzumab, fludarabine, and melphalan is an effective approach for patients with nonmalignant disorders. Mixed chimerism and graft-versus-host-disease (GVHD) remain limitations on success. We hypothesized that higher levels of alemtuzumab at day 0 would result in a low risk of acute GVHD, a higher risk of mixed chimerism, and delayed early lymphocyte recovery and that alemtuzumab level thresholds for increased risks of these outcomes would be definable. We collected data from 105 patients to examine the influence of peritransplant alemtuzumab levels on acute GVHD, mixed chimerism, and lymphocyte recovery. The cumulative incidences of initial grades I-IV, II-IV, and III-IV acute GVHD in patients with alemtuzumab levels ≤0.15 vs ≥0.16 μg/mL were 68% vs 18% (P < .0001), 47% vs 13% (P = .0002), and 32% vs 8%, respectively (P = .005). The cumulative incidence of mixed chimerism in patients with an alemtuzumab level ≤0.15 μg/mL was 21%, vs 42% with levels of 0.16 to 4.35 μg/mL, and 100% with levels >4.35 μg/mL (P = .003). Patients with alemtuzumab levels ≤0.15 or 0.16 to 0.56 μg/mL had higher lymphocyte counts at day +30 and higher T-cell counts at day +100 compared with patients with levels ≥0.57 μg/mL (all P < .05). We conclude that peritransplant alemtuzumab levels impact acute GVHD, mixed chimerism, and lymphocyte recovery following RIC HCT with alemtuzumab, fludarabine, and melphalan. Precision dosing trials are warranted. We recommend a day 0 therapeutic range of 0.2 to 0.4 μg/mL.

Experience with Alemtuzumab, Fludarabine, and Melphalan Reduced-Intensity Conditioning Hematopoietic Cell Transplantation in Patients with Nonmalignant Diseases Reveals Good Outcomes and That the Risk of Mixed Chimerism Depends on Underlying Disease, Stem Cell Source, and Alemtuzumab Regimen

Alemtuzumab, fludarabine, and melphalan reduced-intensity conditioning (RIC) regimens are increasingly used for the hematopoietic cell transplantation (HCT) of pediatric and young adult patients with nonmalignant diseases. Early experience suggests that these regimens are associated with good survival but a high incidence of mixed chimerism, which we have previously shown to be influenced by the alemtuzumab schedule. We hypothesized that the underlying diagnosis and donor graft source would also affect the development of mixed chimerism and that the majority of patients would survive RIC HCT without graft loss. To examine this, we conducted a retrospective study of 206 patients with metabolic diseases, non-Fanconi anemia marrow failure disorders, and primary immune deficiencies who underwent 210 consecutive RIC HCT procedures at Cincinnati Children's Hospital. Ninety-seven percent of the patients engrafted. Mixed donor and recipient chimerism developed in 46% of patients. Patients with marrow failure had a low risk of mixed chimerism (hazard ratio [HR], .208; 95% confidence interval [CI], .061 to .709; P = .012). The risk of mixed chimerism was high in patients who received a cord blood graft (HR, 3.122; 95% CI, 1.236 to 7.888; P = .016). As expected, patients who received a proximal or higher dose per kilogram of alemtuzumab schedule also experienced higher rates of mixed chimerism (all HR > 2, all P < .05). At the time of last follow-up (median, 654 days; range, 13 to 3337), over 75% of patients had greater than 90% whole blood donor chimerism. A second transplantation was performed in 5% of patients. Three-year survival without retransplantation was 84% (95% CI, 71% to 98%) for patients who underwent transplantation with an HLA-matched sibling donor. Survival without retransplantation was negatively affected by lack of a matched related donor, increasing age, and development of grades III and IV acute graft-versus-host disease. We conclude that alemtuzumab, fludarabine, and melphalan RIC HCT offers good results for many patients and that the risk of developing mixed chimerism is influenced by underlying diagnosis, graft source, and alemtuzumab dosing.

Haploidentical stem cell transplantation augmented by CD45RA negative lymphocytes provides rapid engraftment and excellent tolerability

BACKGROUND

Haploidentical donors are being increasingly used for allogeneic hematopoietic cell transplantation (HCT). However, the requisite T-cell depletion results in a profound and often long-lasting immunocompromised state, and donor lymphocyte infusions bring a risk of graft-versus-host disease (GVHD). Naïve T-cells are believed to be among the most alloreactive T-cell subset and can be identified by CD45RA expression. Allogeneic HCT using CD45RA depletion has not been previously described for haploidentical donors.

PROCEDURE

Eight children with relapsed or refractory solid tumors were transplanted following myeloablative conditioning. Each patient received two cell products, one created by CD3 depletion and the other through CD45RA depletion.

RESULTS

Median CD34 recovery was 59.2% with CD45RA depletion, compared to 82.4% using CD3 depletion. Median CD3+ T-cell dose after CD45RA reduction was 99.2 × 10(6)  cells/kg, yet depletion of CD3+ CD45RA+ cells exceeded 4.5 log. CD45RA depletion also resulted in substantial depletion of B-cells (median 2.45 log). All eight patients engrafted within 14 days and rapidly achieved 100% donor chimerism. No acute GVHD or secondary graft failure was observed.

CONCLUSIONS

CD45RA depletion is a novel approach to haploidentical HCT that offers rapid engraftment with minimal risk of GVHD.

Alemtuzumab for the treatment of relapsing-remitting multiple sclerosis

Alemtuzumab, a humanized monoclonal antibody that targets CD52, was recently approved in the EU and Canada for the treatment of patients with active relapsing-remitting multiple sclerosis. Alemtuzumab induces rapid depletion of circulating B- and T-lymphocytes followed by repopulation that leads to a distinctive lymphocyte profile, including an increased proportion of regulatory T-lymphocytes and memory B- and T-lymphocytes. In early open-label studies, alemtuzumab treatment reduced the number of clinical relapses and new MRI lesions in participants with secondary progressive MS. However, most participants had continued worsening of disability, which led to the evaluation of alemtuzumab in patients with early stages of disease in the Genzyme (MA, USA)-sponsored clinical development program in MS. In one Phase II and two Phase III trials, alemtuzumab reduced the number of clinical relapses versus the active comparator, subcutaneous IFN-β-1a, in treatment-naive and treatment-experienced participants with relapsing-remitting multiple sclerosis. Two of these trials showed reduction in risk of confirmed worsening of disability, and all showed reduction in cerebral atrophy. Safety issues include infusion reactions that are mitigated by pretreatment with corticosteroids in addition to symptomatic management with antihistamines; mild to moderate infections; and autoimmune adverse events. In this context, post-marketing risk mitigation strategies will be needed so that potential adverse events can be identified and managed early and effectively.

Impact of serotherapy on immune reconstitution and survival outcomes after stem cell transplantations in children: thymoglobulin versus alemtuzumab

The outcome of allogeneic hematopoietic stem cell transplantation (HSCT) is strongly affected by the kinetics of reconstitution of the immune system. This study compared the effects of antithymocyte globulin (ATG) and alemtuzumab on various outcome parameters after HSCT. The study cohort consisted of 148 children, with a median age of 9.6 years (range, .4 to 19.0), who underwent HSCT for malignant and benign hematological disorders in a single HSCT unit. Conditioning included ATG (n = 110) or alemtuzumab (n = 38). Cox proportional hazard regression analysis showed that alemtuzumab significantly delayed the recovery of CD3(+) T cells and CD4(+)as well as CD8(+) T cell subsets (P ≤ .001) and natural killer (NK) cells (P = .008) compared with ATG. In both ATG- and alemtuzumab-treated patients, shorter drug exposure lead to significantly faster recovery of T cells. Alemtuzumab was associated with lower donor chimerism 3 and 6 months after transplantation and a higher risk of disease relapse (P = .001). The overall survival and event-free survival risks were significantly lower for alemtuzumab-treated patients (P = .020 and P < .001, respectively). Patients who received alemtuzumab showed a trend to lower risk of acute graft-versus-host disease, more human adenovirus, and less Epstein-Barr virus reactivations compared with patients who received ATG. These data indicate that children treated with alemtuzumab as part of the conditioning regimen have a slower T cell and NK cell reconstitution compared with those treated with ATG, which compromises the overall and event-free survival. Prolonged length of lympholytic drug exposure delayed the T cell recovery in both ATG- and alemtuzumab-treated patients. Therefore, we recommend detailed pharmacokinetic/pharmacodynamic (PK/PD) analyses in a larger cohort of patients to develop an algorithm aiming at optimization of the serotherapy containing conditioning regimen.

Optimizing drug therapy in pediatric SCT: focus on pharmacokinetics

Given age-related differences in drug metabolism and indications for hematopoietic SCT (HSCT), personalized drug dosing of the conditioning regimen and post-transplant immunosuppression may reduce graft rejection, relapse rates and toxicity in pediatric HSCT recipients. This manuscript summarizes the pharmacokinetic/dynamic data of HSCT conditioning and post-grafting immunosuppression, presented at the First Annual Pediatric Bone Marrow Transplant Consortium (PBMTC) meeting in April 2013. Personalized dosing of BU to a target plasma exposure reduces graft rejection in children and improves relapse/toxicity rates in adults. Current weight-based dosing achieves the target BU exposure in only a minority (24.3%) of children. The initial BU dose should be based on the European Medicines Agency nomogram or population pharmacokinetic models to improve the numbers of children achieving the target exposure. There are limited pharmacokinetic data for treosulfan, CY, fludarabine and alemtuzumab as HSCT conditioning in children. For post-grafting immunosuppression, mycophenolic acid (MPA) clearance may be increased in younger children (<12 years). The preferred MPA pharmacokinetic monitoring parameters and target range are still evolving in HSCT recipients. Multi-institutional trials incorporating properly powered pharmacokinetic/dynamic studies are needed to assess the effect of variability in the plasma exposure of drugs/metabolites on clinical outcomes in pediatric HSCT recipients.

Mixed chimerism and graft loss in pediatric recipients of an alemtuzumab-based reduced-intensity conditioning regimen for non-malignant disease

BACKGROUND

Reduced-intensity conditioning (RIC) regimens can mitigate the toxicity of hematopoietic cell transplantation (HCT) in children with non-malignant diseases, but are associated with increased risk for post-transplant mixed donor/recipient chimerism (MC) and/or graft loss (GL). Intervention with donor lymphocytes or stem cell boosts (DLI/boost) may be necessary, but there is limited information about timing and results of intervention.

PROCEDURE

We retrospectively evaluated 31 consecutive pediatric recipients of an alemtuzumab-based RIC HCT at the Children's Hospital of Philadelphia from May 2007 to December 2012 to determine the incidence of MC, GL, and use of DLI/boost. All patients received alemtuzumab with either fludarabine (150 mg/m(2) )/melphalan (140 mg/m(2) ) (n = 30) or fludarabine/busulfan (n = 1), and unmanipulated marrow grafts from related (48%) or matched unrelated (52%) donors.

RESULTS

Of surviving patients, 67% and 44% displayed MC and MC with ≤80% donor contribution (MC ≤ 80%), respectively. Rates of MC, MC ≤ 80%, DLI/boost, and GL were significantly higher in recipients of proximal/intermediate (100%, 73%, 46%, and 46%, respectively) compared to distal alemtuzumab (44%, 25%, 6%, and 6%, respectively). Event-free and overall survival was significantly lower in HLH compared with non-HLH patients. Twenty percent of patients required DLI/boost, and DLI/boost did not affect the incidence of GL.

CONCLUSIONS

RIC with proximal/intermediate alemtuzumab is associated with high rates of MC, need for DLI/boost, and GL.

A trial of alemtuzumab adjunctive therapy in allogeneic hematopoietic cell transplantation with minimal conditioning for severe combined immunodeficiency

For infants with SCID the ideal conditioning regimen before allogeneic HCT would omit cytotoxic chemotherapy to minimize short- and long-term complications. We performed a prospective pilot trial with alemtuzumab monotherapy to overcome NK-cell mediated immunologic barriers to engraftment. We enrolled four patients who received CD34-selected haploidentical cells, two of whom failed to engraft donor T cells. The two patients who engrafted had delayed T-cell reconstitution, despite rapid clearance of circulating alemtuzumab. Although well-tolerated, alemtuzumab failed to overcome immunologic barriers to donor engraftment. Furthermore, alemtuzumab may slow T-cell development in patients with SCID in the setting of a T-cell depleted graft.

Drug safety evaluation of alemtuzumab for multiple sclerosis

INTRODUCTION

Alemtuzumab is a humanised anti-CD52 mAb which has recently been licensed for the treatment of relapsing multiple sclerosis in Europe.

AREAS COVERED

The efficacy and safety of alemtuzumab from open label, Phase II and Phase III trials is reported.

EXPERT OPINION

Alemtuzumab causes rapid and profound complement mediated lysis of circulating lymphocytes and allows beneficial modulation of the immune system during a subsequent reconstitution phase. Clinical trials have demonstrated superior efficacy against an active comparator, with reduction in annualised relapse rates and sustained accumulation of disability at 3 years and sustained efficacy at 5 years. The main adverse effects are mild to moderate infusion reactions, an increased incidence of mild to moderate infections and autoimmune adverse events. Thyroid disorders are the most common form of autoimmune adverse events, occurring in approximately one third of patients. Overt Graves' hyperthyroidism represents approximately half of these cases. Careful patient selection and structured monitoring programs allow for effective patient management resulting in a favourable risk benefit profile.

EBV-associated post-transplant lymphoproliferative disorder following in vivo T-cell-depleted allogeneic transplantation: clinical features, viral load correlates and prognostic factors in the rituximab era

EBV-associated post-transplant lymphoproliferative disease (PTLD) following Alemtuzumab-based allo-SCT is a relatively uncommon and challenging clinical problem but has not received detailed study in a large cohort. Quantitative-PCR (qPCR) monitoring for EBV reactivation post allo-SCT is now commonplace but its diagnostic and predictive value remains unclear. Sixty-nine patients with PTLD following Alemtuzumab-based allo-SCT were studied. Marked clinicopathological heterogeneity was evident; lymphadenopathy was frequently absent, whereas advanced extranodal disease was common. The median viral load at clinical presentation was 49 300 copies/mL (50-65 200 000 copies/mL) and, notably, 23% and 45% of cases, respectively, had 10 000 and 40 000 copies/mL. The overall response rate to rituximab as first-line therapy was 70%. For rituximab failures, chemotherapy was ineffectual but DLIs were successful. A four-parameter prognostic index predicted response to therapy (OR 0.30 (0.12-0.74); P=0.009] and PTLD mortality (hazard ratio (HR) 1.81 (1.12-2.93) P=0.02) on multivariate analysis. This is the largest detailed series of EBV-associated PTLD after allo-SCT. At clinical presentation, EBV-qPCR values are frequently below customary thresholds for pre-emptive therapy, challenging current paradigms for monitoring and intervention. A four-point score identifies a proportion of patients at risk of rituximab-refractory disease for whom alternative therapy is needed.

An intermediate alemtuzumab schedule reduces the incidence of mixed chimerism following reduced-intensity conditioning hematopoietic cell transplantation for hemophagocytic lymphohistiocytosis

Reduced-intensity conditioning (RIC) improves the outcomes of hematopoietic cell transplantation (HCT) in patients with hemophagocytic lymphohistiocytosis (HLH). Proximal (ie, close to graft infusion) dosing of alemtuzumab is associated with a high incidence of mixed chimerism, whereas distal (ie, distant from graft infusion) dosing is associated with less mixed chimerism but more acute graft-versus-host disease (GVHD). The alemtuzumab dose per kilogram of body weight also influences these outcomes. We hypothesized that an intermediate alemtuzumab dosing schedule would reduce mixed chimerism and maintain a low incidence of acute GVHD. In this study, 24 consecutive HCTs were performed in patients with HLH or a related disorder using a novel intermediate alemtuzumab schedule of 1 mg/kg starting on day -14. The cumulative incidences (CIs) of mixed chimerism, upfront acute GVHD grades II-IV, and receipt of additional hematopoietic cell products after HCT were compared in patients treated with a distal alemtuzumab schedule (n = 15) and those treated with a proximal alemtuzumab schedule (n = 33). All patients received fludarabine and melphalan. The CI of mixed chimerism was 31% in the intermediate group, 72% in the proximal group (P < .01), and 75% in the distal group patients who received ≥2 mg/kg alemtuzumab (P = .03). The CI of acute GVHD grades II-IV before the development of mixed chimerism was 4% in the intermediate group, 0% in the proximal group, and 13% in the distal group (P = .04, proximal versus distal). The 1-year CI of administration of additional hematopoietic cell products for mixed chimerism (donor lymphocyte infusion ± hematopoietic stem cell boost ± repeat HCT) was 14% in the intermediate group, 53% in the proximal group (P = .01), and 38% in the distal ≥2 mg/kg alemtuzumab group (P = .02). Our findings indicate that intermediate RIC reduces the incidence of mixed chimerism, is associated with a low incidence of upfront acute GVHD, and decreases the need for additional hematopoietic cell products after HCT.

Allogeneic stem cell transplantation using alemtuzumab-containing regimens in severe aplastic anemia

Alemtuzumab, a humanized anti-CD52, IgG1 monoclonal antibody, is used to reduce graft-versus- host disease (GVHD) and aid engraftment after allogeneic haemopoietic stem cell transplant (HSCT). Its associated low incidence of GVHD makes it an attractive alternative to anti-thymocyte globulin (ATG) in transplant conditioning regimen for severe aplastic anaemia (SAA). We have reviewed the use of alemtuzumab-based conditioning regimen for HSCT in SAA and show that it results in sustained haematological engraftment, a very low incidence of chronic GVHD without an increase in viral infections. Intriguingly, alemtuzumab appears to induce tolerance post-HSCT with the findings of stable mixed T cell chimerism with full donor myeloid chimerism and the absence of chronic GVHD, and which persist on withdrawal of post-graft immunosuppression. Finally, its low toxicity profile may permit future application of HSCT to older patients with SAA who fail to respond to immunosuppressive therapy.

Use of the ImmuKnow assay to evaluate the effect of alemtuzumab-depleting induction therapy on cell-mediated immune function after renal transplantation

BACKGROUND

Good outcomes after renal transplantation are dependent on effective immunosuppression while minimizing infection. Alemtuzumab (Campath or Campath-1H) is an anti-CD52 humanized monoclonal IgG1 antibody which induces rapid and sustained depletion of circulating lymphocytes and has been effectively used as an immunosuppressant in post-transplant induction therapy.

METHODS

We used the ImmuKnow assay to compare cell-mediated immune function in renal transplant patients treated with alemtuzumab or with conventional immunosuppressive tri-therapy. The ImmuKnow method determines the levels of adenosine triphosphate (ATP) released from CD4 cells following stimulation with a mitogen.

RESULTS

We showed a statistically significant difference in the distribution of outcome after transplantation between the conventional and the Campath groups (P = 0.010). A significantly higher number of patients treated with alemtuzumab induction therapy were stable after transplantation compared to those treated with conventional immunosuppressive tri-therapy (96.6 vs. 75.7 %). ATP values were significantly higher in the conventional group compared to the Campath group at 180 days after transplantation (P < 0.001). ATP levels did not change significantly over time in clinically stable kidney recipients treated with alemtuzumab induction therapy (P = 0.554).

CONCLUSIONS

The ImmuKnow assay is a useful tool for evaluating the global immune response in alemtuzumab-treated renal transplant patients. Alemtuzumab-depleting induction therapy remains effective for at least 180 days.

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

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

Immune profile of pediatric renal transplant recipients following alemtuzumab induction

The incidence of developing circulating anti-human leukocyte antigen antibodies and the kinetics of T cell depletion and recovery among pediatric renal transplant recipients who receive alemtuzumab induction therapy are unknown. In a collaborative endeavor to minimize maintenance immunosuppression in pediatric renal transplant recipients, we enrolled 35 participants from four centers and treated them with alemtuzumab induction therapy and a steroid-free, calcineurin-inhibitor-withdrawal maintenance regimen. At 3 months after transplant, there was greater depletion of CD4(+) than CD8(+) T cells within the total, naive, memory, and effector memory subsets, although depletion of the central memory subset was similar for CD4(+) and CD8(+) cells. Although CD8(+) T cells recovered faster than CD4(+) subsets overall, they failed to return to pretransplant levels by 24 months after transplant. There was no evidence for greater recovery of either CD4(+) or CD8(+) memory cells than naïve cells. Alemtuzumab relatively spared CD4(+)CD25(+)FoxP3(+) regulatory T cells, resulting in a rise in their numbers relative to total CD4(+) cells and a ratio that remained at least at pretransplant levels throughout the study period. Seven participants (20%) developed anti-human leukocyte antigen antibodies without adversely affecting allograft function or histology on 2-year biopsies. Long-term follow-up is underway to assess the potential benefits of this regimen in children.

In the absence of clinically significant graft vs. host disease, myeloablative conditioning may allow an effective graft vs. leukaemia effect

In AML, prevention of GvHD leads to better tolerance of myeloablative therapy. 66 individuals with AML in CR underwent myeloablative conditioning and transplantation with allogeneic PBPC grafts. Median presentation age was 44.5 years. Karyotyping was intermediate in 48% and of unfavourable risk in 36%. For GvHD prophylaxis, PBPC harvests were incubated ex vivo with anti CD52 antibodies. TRM at day 100 and 1 year was 9% and 17%. At a median of 1018 days 65% are alive. Grade >1 GvHD was seen in 11%. GvHD and adverse karyotype were associated with treatment failure. In younger patients preservation of the dose intensity may improve cure rates.

IgG antibodies to ATG early after pediatric hematopoietic SCT increase the risk of acute GVHD

Anti-thymocyte globulin (ATG), raised in rabbits, is frequently used in allogeneic hematopoietic SCT (HSCT), to prevent graft rejection and acute GVHD. In solid organ transplant patients, antibodies to rabbit IgG result in an enhanced clearance of ATG. The occurrence of such antibodies in HSCT recipients and their clinical impact is unknown. Concentrations of ATG and anti-ATG antibodies were measured in 72 pediatric HSCT recipients treated with ATG as part of the conditioning. Anti-ATG antibodies were detected in 20 children (28%), all transplanted with a non-depleted graft. IgG anti-ATG, alone or combined with IgM and/or IgA anti-ATG, appeared in 10 children. Four patients developed IgG anti-ATG antibodies early (before day 22) post-HSCT. They had steep drops in ATG levels and showed rapid T-cell recovery, which was associated with a significantly increased risk of acute GVHD. In six patients IgG anti-ATG responses occurred later (range 28-46 days) after HSCT without an increased risk of GVHD. A total of 10 children only mounted an IgM (and IgA) anti-ATG response, which was without major impact on ATG levels. These results indicate that early development of IgG anti-ATG antibodies has a major impact on acute GVHD. Routine analysis ATG/anti-ATG Ab measurement should be considered.

Alemtuzumab with fludarabine and cyclophosphamide reduces chronic graft-versus-host disease after allogeneic stem cell transplantation for acquired aplastic anemia

We evaluated a novel alemtuzumab-based conditioning regimen in HSCT for acquired severe aplastic anemia (SAA). In a multicenter retrospective study, 50 patients received transplants from matched sibling donors (MSD; n = 21) and unrelated donors (UD; n = 29), using fludarabine 30 mg/m2 for 4 days, cyclophosphamide 300 mg/m2 for 4 days, and alemtuzumab median total dose of 60 mg (range:40-100 mg). Median age was 35 years (range 8-62). Overall survival at 2 years was 95% ± 5% for MSD and 83% for UD HSCT (p 0.34). Cumulative incidence of graft failure was 9.5% for MSD and 14.5% for UD HSCT. Full-donor chimerism (FDC) in unfractionated peripheral blood was 42%; no patient achieved CD3 FDC. Acute GVHD was observed in only 13.5% patients (all grade I-II) and only 2 patients (4%) developed chronic GVHD. A low incidence of viral infections was seen. Factors influencing overall survival were HSCT comorbidity 2-year index (92% with score 0-1 vs 42% with score ≥ 2, P < .001) and age (92% for age < 50 years vs 71% ≥ 50 years, P < .001). Our data suggest that the use of an alemtuzumab-based HSCT regimen for SAA results in durable engraftment with a low incidence of chronic GVHD.

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

BACKGROUND

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

DESIGN AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Multicenter study of subcutaneous alemtuzumab administered at reduced dose in patients with fludarabine-relapsed/refractory chronic lymphocytic leukemia: final analysis

Optimal management of patients with relapsed/refractory chronic lymphocytic leukemia (CLL) has been the motive behind a large number of studies in recent years, and previous response, its duration, and development of clonal evolution appear to be the best indicators for the choice of a new regimen. Although alemtuzumab in relapsed/refractory CLL may be beneficial, the optimal dosage and risk of infection related to its use remain thus far deeply controversial issues. In this pilot phase II study we investigated the feasibility of, toxicity of, and response to alemtuzumab at a reduced dose (30 mg s.c. for 2 weeks and then once a week at extended intervals: every 2, 4, 6 weeks up to 1 year). The overall response rate was 95%, with 51% complete response. The complete response range was 55% in fludarabine-relapsed patients and 28% in patients with fludarabine-refractory disease, without significant difference between the two groups. The regimen was well tolerated with mild toxicity and few cytomegalovirus (CMV) infections. With a median follow-up of 27 months, the overall survival (46% at 3 years) appears to be similar to that with other regimens although with fewer adverse events. In conclusion, treatment with alemtuzumab at a reduced dose seems to be safe and increases the event-free survival of patients with relapsed/refractory CLL, compared with the standard dose. A randomized study comparing both regimens including a larger number of patients is warranted.

Alemtuzumab in allogeneic hematopoetic stem cell transplantation

INTRODUCTION

With the use of reduced-intensity conditioning (RIC), early toxicity of allogeneic stem cell transplantation (SCT) has been much reduced. Graft-versus-host disease (GvHD) causes morbidities and mortality. Alemtuzumab is a mAb directed against CD52. When administered prior to transplant, it leads to T-cell depletion. Incorporation of alemtuzumab in RIC results in low rates of GvHD and treatment-related mortality (TRM) in haematological diseases, even in the setting of mismatched-donor transplantation.

AREAS COVERED

The use of alemtuzumab for GvHD prophylaxis in SCT. The benefit of alemtuzumab-based conditioning is partially offset by increased disease relapse due to impaired graft-versus-tumor effect (GvT) and by slower immune reconstitution, necessitating special precautions. While GvHD is prevented with alemtuzumab, post-SCT interventions are often required. Most studies find that alemtuzumab-based conditioning results in decreased chronic GvHD and TRM, but also in decreased progression-free survival. Overall survival after 3 - 5 years is usually equivalent and quality of life may be improved because of a lower incidence of sequelae of chronic GvHD. Many aspects of alemtuzumab treatment are under investigation.

EXPERT OPINION

Alemtuzumab reduces GvHD and TRM after SCT. Use of alemtuzumab requires awareness and strict management of the risk of opportunistic infections and of an increased risk of disease recurrence.

Allogeneic immunotherapy to optimize the graft-versus-tumor effect: concepts and controversies

This article focuses on the recent evolution of novel conditioning regimens in combination with adoptive cellular therapy in the allogeneic transplant setting for hematologic malignancies. Building on data from animal models, the field of allogeneic transplantation is undergoing a paradigm shift toward immunosuppressive regimens with less toxicity that allow donor hematopoietic engraftment in order to provide a graft-versus-tumor effect as the primary goal of transplantation, rather than chemoablation. In addition, the strategies described in this article, including the use of T-cell subsets as adoptive therapy, will apply to a much broader pool of patients than traditional transplant approaches, thereby allowing more patients with life-limiting illnesses, previously deemed ineligible, to pursue therapy with curative intent.

Unrelated donor peripheral blood stem cell transplants incorporating pre-transplant in-vivo alemtuzumab are not associated with any increased risk of significant acute or chronic graft-versus-host disease

There is little information published comparing peripheral blood stem cells (PBSC) with bone marrow (BM) as the stem cell source in the long-term outcome in recipients of T-cell depleted (TCD) unrelated donor (UD) transplants. We present retrospective outcome data on 306 recipients of myeloablative, human leucocyte antigen-matched UD allografts using pre-transplant in-vivo Alemtuzumab. Transplants were performed between 2000 and 2007 for chronic myeloid leukaemia in first chronic phase and acute leukaemia in first or second complete remission; 184 patients received BM and 122 PBSC. The median age was 28·9 years (<1-58) and the median follow-up was 48 months. Overall survival at 8 years was 53%. The incidence of acute graft-versus-host disease (GvHD) was significantly higher in PBSC (65%) than BM recipients (49%; P=0·012). This represented only grade 1 GvHD with no difference in grade II-IV aGvHD (BM 23% PBSC 24%). The incidence of chronic GvHD, either overall (BM 47%, PBSC 49%) or extensive (BM 15%, PBSC 13%) was not increased with PBSC. The incidence of relapse, non-relapse mortality and survival were not significantly different. Whilst accepting the limitations of retrospective analyses, we suggest the increased risk of GvHD in recipients of PBSC in T-replete transplants is offset by in-vivo Alemtuzumab, and that either stem cell source can be used with good outcomes in this setting.

Relationship between pharmacokinetic profile of subcutaneously administered alemtuzumab and clinical response in patients with chronic lymphocytic leukemia

Alemtuzumab serum levels and clinical response after subcutaneous administration (10 mg 3 times/week for six weeks) have been explored in 29 chronic lymphocytic leukemia patients receiving the monoclonal antibody as consolidation. Serum concentrations after each administration gradually increased during the first week and more markedly during weeks 2 and 3, approaching the steady-state at week 6. Absorption continued slowly through the tissues for about 2-3 weeks after the last administration, starting to decrease thereafter. Difference between Responders and Non-responders was statistically significant: maximal concentration (Cmax) was 1.69 μg/mL vs. 0.44 μg/mL; concentration before subcutaneous administration (Cpre-dose) on day 15 was 0.7 vs. 0.21 μg/mL, area under curve (AUC0-12h) was 11.09 vs. 2.26 μgxh/mL for Responders and Non-responders, respectively. Higher systemic exposure to alemtuzumab correlated with a better clinical response and minimal residual disease. Results suggest that an adjusted schedule according to serum level could improve clinical outcome of patients receiving subcutaneous alemtuzumab.

Pharmacokinetics and clinical activity of very low-dose alemtuzumab in transplantation for acute leukemia

The optimal dose of in vivo-administrated alemtuzumab in the allogeneic transplantation setting has not been defined. We report our experience on 37 patients with high-risk diseases, mainly acute leukemia (AML 23, ALL 10 patients), who underwent sibling (49%) or unrelated (51%) PBSCT (35 patients), and received a total dose of only 10-20 mg Campath-1H as part of the conditioning, and post-transplant CYA without MTX. The neutrophil and especially the platelet engraftment were rapid. There were only two grade III-IV acute GvHD cases, which occurred in unrelated transplants in the Campath-10 cohort. Chronic GvHD developed in six cases (17%) and was limited to skin in five of them. After a median follow-up of 371 days (59-1191), 70% patients are alive and in CR (Karnofsky 100%), and 11 died (TRM n=6, relapse n=5). From the five patients relapsed, three were at advanced stage at transplant and four underwent sibling HCT with the higher (20 mg) alemtuzumab dose. With the 10 mg alemtuzumab schedule (5 mg/day at days -2 and -1) we achieve at day of transplantation low but still lymphotoxic alemtuzumab serum concentrations (176 ng/mL), whereas levels declined fast thereafter, and at engraftment nearly no Campath antibody remained in the patient's serum.

Non-human primate regulatory T cells: current biology and implications for transplantation

Regulatory T cells (Treg) offer potential for improving long-term outcomes in cell and organ transplantation. The non-human primate model is a valuable resource for addressing issues concerning the transfer of Treg therapy to the clinic. Herein, we discuss the properties of non-human primate Treg and prospects for their evaluation in allotransplantation and xenotransplantation.

Evaluation of a surveillance strategy for early detection of adenovirus by PCR of peripheral blood in hematopoietic SCT recipients: incidence and outcome

Adenoviruses (AdV) have emerged as important causes of morbidity and mortality in patients after hematopoietic SCT (HSCT). Early diagnosis of the infection by detection of viral DNA may improve the prognosis. A surveillance strategy was evaluated for detection of AdV DNA by PCR in a prospective study of unselected allogeneic HSCT recipients. In parallel with a routine CMV surveillance program, plasma from 20 children and 77 adults was analyzed by quantitative PCR for detection of AdV DNA. In addition, in 12 unselected patients, the presence of AdV-specific T cells were analyzed by enzyme-linked immunosorbent spot (ELISPOT) at 1 to 3 months after transplantation. A total of 5 of 97 (5%) patients had detectable AdV DNA in peripheral blood. Only one patient had high titers and none developed AdV disease. BM as a source of stem cells and myelodysplastic syndrome as the indication for transplantation were independently associated with higher risk of acquiring AdV infection. AdV-specific T cells were detected in 7 (58%) of 12 patients. Although AdV DNA was found in peripheral blood by quantitative PCR in 5% of patients undergoing allogeneic HSCT, the present surveillance program did not have a significant effect on the clinical outcome.

Investigation of lymphocyte depletion and repopulation using alemtuzumab (Campath-1H) in cynomolgus monkeys

As the target CD52 molecule is expressed on erythrocytes of most nonhuman primate strains, using alemtuzumab in these species would cause massive hemolysis. Six cynomolgus monkeys of Indonesian origin, screened by agglutination assay for absence of CD52 on erythrocytes, were administered alemtuzumab in a cumulative dose to a maximum of 60 mg/kg. In two monkeys, mycophenolate mofetil (MMF) was added as maintenance therapy. Complete depletion of T and B lymphocytes (>99.5%) was achieved with 20 mg/kg alemtuzumab and was more profound than in monkeys treated with antithymocyte globulin (n = 5), as quantified by flow cytometry. Repopulation was suppressed by weekly injections of 10 mg/kg. Without MMF, repopulation of CD20(+)B cells and CD8(+)T cells was complete within 2 and 3 months, respectively, and repopulation of CD4(+)T cells was 67% after 1 year. MMF significantly delayed CD4(+)T-cell repopulation. Among repopulating CD4(+) and CD8(+) T cells, a phenotypic shift was observed from CD45RA(hi)CD62L(hi) naïve cells toward CD45RA(lo)CD62L(lo) effector memory cells. In lymph nodes, the depletion of naïve cells was more profound than of memory cells, which may have initiated a proliferation of memory cells. This model offers opportunities to investigate lymphocyte depletion/repopulation phenomena, as well as the efficacy of alemtuzumab in preclinical transplantation models.

Allogeneic hematopoietic stem-cell transplantation for sickle cell disease

BACKGROUND

Myeloablative allogeneic hematopoietic stem-cell transplantation is curative in children with sickle cell disease, but in adults the procedure is unduly toxic. Graft rejection and graft-versus-host disease (GVHD) are additional barriers to its success. We performed nonmyeloablative stem-cell transplantation in adults with sickle cell disease.

METHODS

Ten adults (age range, 16 to 45 years) with severe sickle cell disease underwent nonmyeloablative transplantation with CD34+ peripheral-blood stem cells, mobilized by granulocyte colony-stimulating factor (G-CSF), which were obtained from HLA-matched siblings. The patients received 300 cGy of total-body irradiation plus alemtuzumab before transplantation, and sirolimus was administered afterward.

RESULTS

All 10 patients were alive at a median follow-up of 30 months after transplantation (range, 15 to 54). Nine patients had long-term, stable donor lymphohematopoietic engraftment at levels that sufficed to reverse the sickle cell disease phenotype. Mean (+/-SE) donor-recipient chimerism for T cells (CD3+) and myeloid cells (CD14+15+) was 53.3+/-8.6% and 83.3+/-10.3%, respectively, in the nine patients whose grafts were successful. Hemoglobin values before transplantation and at the last follow-up assessment were 9.0+/-0.3 and 12.6+/-0.5 g per deciliter, respectively. Serious adverse events included the narcotic-withdrawal syndrome and sirolimus-associated pneumonitis and arthralgia. Neither acute nor chronic GVHD developed in any patient.

CONCLUSIONS

A protocol for nonmyeloablative allogeneic hematopoietic stem-cell transplantation that includes total-body irradiation and treatment with alemtuzumab and sirolimus can achieve stable, mixed donor-recipient chimerism and reverse the sickle cell phenotype. (ClinicalTrials.gov number, NCT00061568.)

The risk of early and late CMV DNAemia associated with Campath use in stem cell transplant recipients

The risks associated with in vivo and ex vivo use of Campath-1H and -1G in a cohort of 206 stem cell transplant recipients for human CMV (HCMV) DNAemia have been quantified. DNAemia showed a biphasic incidence pattern with an inflexion at day 60. The first phase had a linear risk rate for HCMV DNAemia of 0.3% per day, whereas the second phase had a substantially lower risk rate of 0.058% per day. In multivariable analyses, risk factors for early DNAemia were HCMV serostatus, radiotherapy-based conditioning and CD34 stem cell dose, with the use of in vivo Campath-1H having the most significant risk (hazards ratio=3.68; 95% CI=2.02-6.72; P<0.001). Ex vivo use of Campath was not associated with an increased risk for HCMV DNAemia. Patients receiving either in vivo Campath-1H or -1G experienced HCMV DNAemia earlier (27 and 33 days, respectively) compared with patients receiving no Campath (time to DNAemia, 51 days; P=0.0006). Multivariable analysis of risk factors for HCMV DNAemia occurring beyond 100 days after transplant were older age, acute GVHD>grade II and a lower CD34 stem cell dose, whereas Campath-1H use was not associated with late HCMV DNAemia.