Impact of alemtuzumab pharmacokinetics on T-cell dynamics, graft-versus-host disease and viral reactivation in patients receiving allogeneic stem cell transplantation with an alemtuzumab-based T-cell-depleted graft

High-dose alemtuzumab and cyclosporine vs tacrolimus, methotrexate, and sirolimus for chronic graft-versus-host disease prevention

ABSTRACT

Chronic graft-versus-host disease (cGVHD) remains a significant problem for patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Although in vivo lymphodepletion for cGVHD prophylaxis has been explored in the myeloablative setting, its effects after reduced-intensity conditioning (RIC) are not well described. Patients (N = 83) with hematologic malignancies underwent targeted lymphodepletion chemotherapy followed by a RIC allo-HSCT using peripheral blood stem cells from unrelated donors. Patients were randomized to 2 GVHD prophylaxis arms: alemtuzumab and cyclosporine (AC; n = 44) or tacrolimus, methotrexate, and sirolimus (TMS; n = 39), with the primary end point of cumulative incidence of severe cGVHD. The incidence of severe cGVHD was lower with AC vs TMS prophylaxis at 1- and 5-years (0% vs 10.3% and 4.5% vs 28.5%; overall, P = .0002), as well as any grade (P = .003) and moderate-severe (P < .0001) cGVHD. AC was associated with higher rates of grade 3 to 4 infections (P = .02) and relapse (52% vs 21%; P = .003) with no difference in 5-year GVHD-free-, relapse-free-, or overall survival. AC severely depleted naïve T-cell reconstitution, resulting in reduced T-cell receptor repertoire diversity, smaller populations of CD4Treg and CD8Tscm, but a higher ratio of Treg to naïve T-cells at 6 months. In summary, an alemtuzumab-based regimen successfully reduced the rate and severity of cGVHD after RIC allo-HSCT and resulted in a distinct immunomodulatory profile, which may have reduced cGVHD incidence and severity. However, increased infections and relapse resulted in a lack of survival benefit after long-term follow-up. This trial was registered at www.ClinicalTrials.gov as #NCT00520130.

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.

Allogeneic Hematopoietic cell Transplantation Using Alemtuzumab in Asian Patients with Inborn Errors of Immunity

Alemtuzumab is used with reduced-toxicity conditioning (RTC) in allogeneic hematopoietic cell transplantation (HCT), demonstrating efficacy and feasibility for patients with inborn errors of immunity (IEI) in Western countries; however, the clinical experience in Asian patients with IEI is limited. We retrospectively analyzed patients with IEI who underwent the first allogeneic HCT with alemtuzumab combined with RTC regimens in Japan. A total of 19 patients were included and followed up for a median of 18 months. The donors were haploidentical parents (n = 10), matched siblings (n = 2), and unrelated bone marrow donors (n = 7). Most patients received RTC regimens containing fludarabine and busulfan and were treated with 0.8 mg/kg alemtuzumab with intermediate timing. Eighteen patients survived and achieved stable engraftment, and no grade 3-4 acute graft-versus-host disease was observed. Viral infections were observed in 11 patients (58%) and 6 of them presented symptomatic. The median CD4+ T cell count was low at 6 months (241/µL) but improved at 1 year (577/µL) after HCT. Whole blood cells continued to exhibit > 80% donor type in most cases; however, 3/10 patients exhibited poor donor chimerism only among T cells and also showed undetectable levels of T-cell receptor recombination excision circles (TRECs) at 1 year post-HCT. This study demonstrated the efficacy and safety of alemtuzumab; however, patients frequently developed viral infections and slow reconstitution or low donor chimerism in T cells, emphasizing the importance of monitoring viral status and T-cell-specific chimerism. (238 < 250 words).

Competitive Repopulation and Allo-Immunologic Pressure Determine Chimerism Kinetics after T Cell-Depleted Allogeneic Stem Cell Transplantation and Donor Lymphocyte Infusion

After allogeneic stem cell transplantation (alloSCT), patient-derived stem cells that survived the pretransplantation conditioning compete with engrafting donor stem cells for bone marrow (BM) repopulation. In addition, donor-derived alloreactive T cells present in the stem cell product may favor establishment of complete donor-derived hematopoiesis by eliminating patient-derived lymphohematopoietic cells. T cell-depleted alloSCT with sequential transfer of potentially alloreactive T cells by donor lymphocyte infusion (DLI) provides a unique opportunity to selectively study how competitive repopulation and allo-immunologic pressure influence lymphohematopoietic recovery. This study aimed to determine the relative contribution of competitive repopulation and donor-derived anti-recipient alloimmunologic pressure on the establishment of lymphohematopoietic chimerism after alloSCT. In this retrospective cohort study of 281 acute leukemia patients treated according to a protocol combining alemtuzumab-based T cell-depleted alloSCT with prophylactic DLI, we investigated engraftment and quantitative donor chimerism in the BM and immune cell subsets. DLI-induced increase of chimerism and development of graft-versus-host disease (GVHD) were analyzed as complementary indicators for donor-derived anti-recipient alloimmunologic pressure. Profound suppression of patient immune cells by conditioning sufficed for sustained engraftment without necessity for myeloablative conditioning or development of clinically significant GVHD. Although 61% of the patients without any DLI or GVHD showed full donor chimerism (FDC) in the BM at 6 months after alloSCT, only 24% showed FDC in the CD4⁺ T cell compartment. In contrast, 75% of the patients who had received DLI and 83% of the patients with clinically significant GVHD had FDC in this compartment. In addition, 72% of the patients with mixed hematopoiesis receiving DLI converted to complete donor-derived hematopoiesis, of whom only 34% developed clinically significant GVHD. Our data show that competitive repopulation can be sufficient to reach complete donor-derived hematopoiesis, but that some alloimmunologic pressure is needed for the establishment of a completely donor-derived T cell compartment, either by the development of GVHD or by administration of DLI. We illustrate that it is possible to separate the graft-versus-leukemia effect from GVHD, as conversion to durable complete donor-derived hematopoiesis following DLI did not require induction of clinically significant GVHD.

Population pharmacokinetics of subcutaneous alemtuzumab in kidney transplantation

AIM

Alemtuzumab is a monoclonal antibody used as induction immunosuppressive therapy in kidney transplantation. It targets CD52 on lymphocytes, inducing profound immune cell depletion upon administration. Owing to its off-label status in kidney transplantation, its pharmacokinetic characteristics are largely unknown in this setting, and its current fixed dosing algorithm originates from other populations. We developed a population pharmacokinetic model for alemtuzumab in kidney transplant recipients and investigated the potential of personalized alemtuzumab therapy.

METHODS

In total, 362 pharmacokinetic observations drawn 0-165 days after transplantation were available from 61 adult kidney transplant recipients who received two consecutive doses of 15 mg alemtuzumab subcutaneously. A population pharmacokinetic model was developed using nonlinear mixed-effects modelling and applied to simulate various dosing regimens.

RESULTS

The alemtuzumab concentration-time data were best described by a two-compartmental model with first-order absorption and parallel first-order and time-varying concentration-dependent elimination, with between-subject variability on the first-order elimination (39.6%) and central distribution volume (39.6%). Alemtuzumab pharmacokinetics varied with body size, rendering lighter individuals exposed to lympholytic alemtuzumab concentrations (>0.1 mg/L) for prolonged durations as compared to their heavier peers. This between-subject variability could be reduced through lean bodyweight-adjusted dosing, showing a twofold to threefold reduction in the slope of the median alemtuzumab exposure over the bodyweight range.

CONCLUSION

Alemtuzumab displays substantial pharmacokinetic variability in kidney transplant recipients, which may warrant a personalized treatment strategy. Lean bodyweight-adjusted dosing poses an option for individualized dosing, but further evaluation of its potential clinical benefit is warranted.

Clinical and Molecular Profiling to Develop a Potential Prediction Model for the Response to Alemtuzumab Therapy for Acute Kidney Transplant Rejection

Alemtuzumab, a monoclonal antibody that depletes CD52‐bearing immune cells, is an effective drug for the treatment of severe or glucocorticoid‐resistant acute kidney transplant rejection (AR). Patient‐specific predictions on treatment response are, however, urgently needed, given the severe side effects of alemtuzumab. This study developed a multidimensional prediction model with the aim of generating clinically useful prognostic scores for the response to alemtuzumab. Clinical and histological characteristics were collected retrospectively from patients who were treated with alemtuzumab for AR. In addition, targeted gene expression profiling of AR biopsy tissues was performed. Least absolute shrinkage and selection operator (LASSO) logistic regression modeling was used to construct the ALEMtuzumab for Acute Rejection (ALEMAR) prognostic score. Response to alemtuzumab was defined as patient and allograft survival and at least once an estimated glomerular filtration rate (eGFR) > 30 mL/min/1.73 m² during the first 6 months after treatment. One hundred fifteen patients were included, of which 84 (73%) had a response to alemtuzumab. The ALEMAR‐score accurately predicted the chance of response. Gene expression analysis identified 13 differentially expressed genes between responders and nonresponders. The combination of the ALEMAR‐score and selected genes resulted in improved predictions of treatment response. The present preliminary prediction model is potentially helpful for the development of stratified alemtuzumab treatment for acute kidney transplant rejection but requires validation.

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

BACKGROUND AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CD52-negative T cells predict acute graft-versus-host disease after an alemtuzumab-based conditioning regimen

Allogeneic haematopoietic stem cell transplantation (HSCT) after a reduced-intensity conditioning (RIC) regimen with fludarabine, melphalan and alemtuzmab is an effective therapy for haematological malignancies. Alemtuzumab, a monoclonal antibody against CD52, a glycosylphosphatidylinositol-anchor-bound surface protein on lymphocytes, depletes T cells to prevent graft-versus-host disease (GVHD). Despite this, acute and chronic GVHD (a/cGVHD) remain life-threatening complications after HSCT. The aim of the present study was to identify parameters to predict GVHD. In 69 patients after HSCT, T-cell subsets were functionally analysed. Reconstitution of CD52^neg T cells and CD52^neg regulatory T cells (Tregs) correlated with onset, severity and clinical course of aGVHD. Patients with aGVHD showed significantly lower levels of CD52^pos T cells compared to patients with cGVHD or without GVHD (P < 0·001). Analysis of T-cell reconstitution revealed a percentage of <40% of CD52^pos CD4^pos T cells or CD52^pos Tregs at day +50 as a risk factor for the development of aGVHD. In contrast, CD52^neg Tregs showed significant decreased levels of glycoprotein A repetitions predominant (GARP; P < 0·001), glucocorticoid-induced TNFR-related protein (GITR; P < 0·001), chemokine receptor (CXCR3; P = 0·023), C-C chemokine receptor type 5 (CCR5; P = 0·004), but increased levels of immunoglobulin-like transcript 3 (ILT3; P = 0·001), as well as a reduced suppressive capacity. We conclude that reconstitution of CD52^neg T cells and CD52^neg Tregs is a risk factor for development of aGVHD.