Pharmacokinetics Of Alemtuzumab Research Articles

Population pharmacokinetics of subcutaneous alemtuzumab in kidney transplantation.

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. 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. 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 (>0.1mg/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. 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.

Pharmacokinetics of Alemtuzumab in Pediatric Patients Undergoing T-Cell Depleted Haploidentical Hematopoietic Cell Transplantation (HCT)

<h3>Introduction</h3> Haploidentical HCT is a viable option for patients with hematological malignancies who do not have a matched donor available. However, the presence of HLA-mismatch can be associated with increased risk of donor graft rejection, graft versus host disease (GVHD), infections due to delayed immune reconstitution and regimen-related toxicity. <h3>Methods</h3> We used alemtuzumab, a monoclonal antibody targeting CD52, for <i>in vivo</i> depletion of host and donor T cells - as CD52 is predominantly expressed in T cells. Recipients also received donor grafts that underwent <i>ex vivo</i> T-cell depletion (immunomagnetic depletion of CD3+ cells). The objective of this study is to study the pharmacokinetics of alemtuzumab in pediatric patients with hematological malignancies undergoing T-cell depleted haploidentical HCT, and to identify factors that might be associated with differences in drug exposure. Alemtuzumab was administered as described in Table 1, and levels were checked at days -10, -8, -3, and weeks 1, 2, 4, 8 and 16 from serum samples of 13 patients. A compartmental pharmacokinetic model was fit to the data using nonlinear mixed-effects modeling. <h3>Results</h3> Out of the thirteen patients, twelve engrafted neutrophils at a median of day +11 and platelets at a median of day +15. Seven patients were alive one year after transplant. Our cohort included one primary and one secondary graft failure, three relapses and six patients who had grade II-IV acute GVHD. In addition, seven patients experienced mixed chimerism, and required donor lymphocyte infusion (DLI) for correction. The median (range) clearance (ml/day/m²) and area under the curve (AUC) (µg*day/mL) were 255 (211, 600) and 117.1 (28.1, 165.4), respectively. The median serum level on day –3 was 3.8 µg/mL. 77% of the patients had detectable levels as late as week 4 and the median (range) half-life was 11 days (4.3, 12.9). Clearance increased with age, weight, and serum creatinine (p < 0.05) (Figure 1). Conversely AUC decreased with age, weight, and serum creatinine (p < 0.02). Although we did not notice a statistically significant relationship between AUC and absolute lymphocyte count (ALC), clearance increased with increase in ALC (p = 0.008) (Figure 1). Additionally, there was no association between AUC and immune reconstitution, survival, relapse, graft failure, or acute GVHD. <h3>Conclusion</h3> While our study is limited by small sample size, to our knowledge this is the first pharmacokinetic study of alemtuzumab in pediatric haploidentical transplant patients using a body surface area dosing strategy.

Alemtuzumab as First Line Treatment in Children with Familial Lymphohistiocytosis

Background Hemophagocytic lymphohistiocytosis (HLH) is an inflammatory condition caused by uncontrolled proliferation of activated lymphocytes and macrophages secreting an excess of inflammatory cytokines. When untreated, primary HLH is invariably fatal. Treatment requires the achievement of remission of HLH prior to allogeneic hematopoietic stem cell transplantation. Despite significant treatment progress, pre-HSCT mortality remains a challenge. In the Etoposide-based HLH-94 and HLH-2004 studies pre-HSCT mortality was 27% and 19%, respectively. A better understanding of the pathophysiology of primary HLH has opened new avenues for targeted immunotherapy. Based on our previous observation concerning the use of Antithymoglobulin in HLH, we propose a new therapeutic strategy with Alemtuzumab in association with steroids and cyclosporine A (CSA) as first line treatment in primary HLH. In contrast to ATG, Alemtuzumab does not activate T lymphocytes while killing them. Therefore, we expect a better tolerance and efficacy of Alemtuzumab. This may have a positive impact not only on survival until HSCT, but also on overall survival and quality of life, especially with regard to long-term neurological sequelae. Methods 24 consecutive treatment naïve patients with genetically confirmed primary HLH had received first line Alemtuzumab in association to steroids and CSA from 01/2009 to 06/2015 in the Unit for Pediatric Immunology in Necker Hospital Paris, as well as two additional patients in 10/2016 and 10/2018 respectively, who could not be included in the prospective trial. From 06/2015 to 06/2019, 29 patients have been enrolled in a multicenter, open, phase I/II, non-comparative, non randomized study (NCT02472054). Patients with lymphohistiocytic activation syndrome who had not received any specific treatment prior to enrollment except steroids and CSA were included. Treatment consisted in intravenous administration of Alemtuzumab in association to Methylprednisolone and CSA. The primary outcome measures is the number of surviving patients until HSCT, secondary outcome measures the number of complete remissions following treatment at Day (D)14, D21, D28. To assess the efficacy of the Alemtuzumab, the time of delay between the first administration of Alemtuzumab and complete remission will be determined. Alemtuzumab Pharmacokinetics will be done. All adverse events are reported. Results Retrospective analysis of 26 patients (pilot study): The median age of patients was 1.9 months (birth - 7 years), 6 patients were neonates. When Alemtuzumab was started, out of 26 patients 12 (46.1%) required intensive care, 8 (30.7%) mechanical ventilation, 13 (50%) had neurological involvement, 9 (34.6%) hepatocellular insufficiency. One 2-month-old Munc13-4 patient died at H+48 after two administrations of Alemtuzumab (total dose 1.5mg/kg) for hepatic failure and acute renal failure. A second patient with Perforin deficiency did not respond neither to three courses of Alemtuzumab (cumulative dose 6.5mg/kg) nor repeated Etoposid, 40mg/kg ATG, or Ruxulotinib. He died at D+65. The 24 remaining patients survived until HSCT (survival 92.3%). As shown in the figure, two patients required additional treatment. Overall 22 patients achieved CR, 2 PR at the time of HSCT. The prospective study enrolled 29 patients from 06/2015 to 06/2019. Median age at onset of HLH was 0.5 years (range 0.02 to 17.2 years), one patient withdrawed consent. 12 patients received one course, 13 two, 2 three and one patient 4 courses of Alemtuzumab. 24 patients with a genetic confirmed HLH predisposition reached the primary endpoint with 22 surviving until HSCT (91,6%). One patient is still awaiting HSCT. The three remaining patients are one CA-EBV patient and a newborn with secondary HLH due to fulminant HSV hepatitis, who both died, as well as a patient with predominant neurological HLH without genetic diagnosis who is in sustained remission without any specific treatment. Detailed results from the completed study will be presented. Conclusions This is the first report on Alemtuzumab as first line approach in the treatment of primary HLH. Our results in more than 50 pediatric patients treated in a pilot study and prospective trial indicate that Alemtuzumab allows controlling HLH activity with a favorable safety and tolerability profile in a very fragile population. 92.3% and 91.6% of patients respectively survived to HSCT. Figure Disclosures No relevant conflicts of interest to declare. Off Label Disclosure: Alemtuzumab (Campath) has been used in a prospective trial to evaluate its efficacy as first line treatment in Familial Lymphohistiocytosis.

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

Administration of alemtuzumab (targeting the CD52 antigen) to the patient (in-vivo) or to the graft (in-vitro) before allogeneic stem cell transplantation (alloSCT) decreases the incidence of graft-versus-host disease (GvHD). Effectiveness of this treatment relies on depletion of donor T cells. Currently, no data are available on alemtuzumab pharmacokinetics and pharmacodynamics in patients who received combined in-vivo and in-vitro alemtuzumab-based T-cell depletion. In this prospective study, we analyzed alemtuzumab pharmacokinetics and its effect on the circulating T cells in 36 patients who received an allogeneic T-cell-depleted graft by addition of 20 mg alemtuzumab “to the bag” with or without prior alemtuzumab (30 mg cumulative dose intravenously) as part of the conditioning regimen. Effective T-cell depletion was shown for all patients, even though alemtuzumab plasma levels varied considerably. Peak alemtuzumab levels were observed directly after graft infusion and were not associated with the number of circulating T cells pre-infusion, but with plasma volumes of the patients. All patients engrafted, confirming feasibility of this transplantation protocol. Only three patients with low alemtuzumab levels developed acute GvHD (grade II in 2 patients and grade III in 1 patient). Persistence of circulating alemtuzumab at 3 weeks after transplantation had prevented reconstitution of CD52-positive T cells when alemtuzumab plasma levels were above 0.7 μg/mL. However, overall T-cell reconstitution did not correlate with the levels of alemtuzumab exposure, due to early reconstitution of CD52-negative alemtuzumab-resistant T cells. The protective effect of these cells likely explains the low incidence of Epstein-Barr-virus- and cytomegalovirus-related disease despite circulating alemtuzumab.

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

Background and ObjectiveAlemtuzumab (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.MethodsA 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.ResultsAlemtuzumab 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.ConclusionThe 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.Electronic supplementary materialThe online version of this article (10.1007/s40262-019-00782-0) contains supplementary material, which is available to authorized users.

Pretransplant Absolute Lymphocyte Counts Impact the Pharmacokinetics of Alemtuzumab

Alemtuzumab is frequently used as part of reduced-intensity conditioning (RIC) regimens for allogeneic hematopoietic cell transplantation (HCT) in pediatric patients with nonmalignant diseases. We previously suggested an optimal day 0 targeted range of alemtuzumab, but there are no pediatric data regarding the pharmacokinetics (PK) of subcutaneous alemtuzumab to guide precision dosing trials. The goal of this study was to prospectively characterize alemtuzumab PK and to explore absolute lymphocyte count (ALC) as a predictor of interindividual variability. We prospectively enrolled 23 patients who received an alemtuzumab, fludarabine, and melphalan RIC regimen. Seventeen patients completed study and received 1 mg/kg alemtuzumab divided over 5 days subcutaneously, starting on day −14. The median age was 7 years (range, .5 to 18). Blood sampling for PK measurements and descriptive PK analyses were performed. The median maximum alemtuzumab concentration was 2.39 µg/mL (interquartile range, 1.98 to 2.92). The median terminal half-life was 5.2 days (interquartile range, 2.7 to 7.8). The median concentration at day 0 was 1.27 µg/mL (interquartile range, .35 to 1.51). Importantly, day 0 alemtuzumab levels and area under the curve negatively correlated with predose ALC and ALC area-time, respectively. In conclusion, we reported the PK of subcutaneous alemtuzumab given to pediatric allogeneic HCT patients and observed that almost all patients have persistence of lytic levels of alemtuzumab beyond day 0, at levels in excess of that needed to reduce the risk of acute graft-versus-host disease. Additionally, levels correlate with pretransplant ALC. These results will allow the development of population PK models for precision dosing trials.

Precision Dosing of Alemtuzumab: Population Pharmacokinetic Modeling in Pediatric Patients Undergoing Allogeneic Hematopoietic Cell Transplantation for Non-Malignant Diseases

INTRODUCTION:A commonly utilized reduced intensity conditioning (RIC) for allogeneic hematopoietic cell transplantation (HCT) of patients with non-malignant disorders consists of alemtuzumab (Campath), fludarabine, and melphalan. Our group recently showed that the risks of acute graft vs host disease (GVHD) and the development of mixed chimerism following this regimen are determined by the peri-transplant levels of alemtuzumab, and recommended a potential optimal Day 0 (D0) alemtuzumab level in the range of 0.2-0.4 µg/mL (Marsh et al, Blood 2016). Additionally, patients with Day 0 alemtuzumab levels >0.6ug/mL also had delayed immune reconstitution post-transplant.We have since conducted a prospective 'intensive sampling' pharmacokinetics (PK) study of subcutaneous alemtuzumab in pediatric patients undergoing HCT (Marsh et al. EBMT Oral Presentation 2016). PK data showed a large inter-individual variability in alemtuzumab exposure and D0 levels. Importantly, levels correlated with pre-transplant absolute lymphocyte count (ALC) and underlying diagnoses. Due to the direct effects of alemtuzumab levels on important HCT outcomes, it is desirable to optimize its dosing. Ideal dosing will be where there is adequate alemtuzumab on D0 to prevent acute GVHD but not too much so as to increase the risk of mixed chimerism and/or delay early post-HCT immune recovery. In order to support targeted precision dosing of alemtuzumab in a prospective clinical trial, we have developed a population PK (PPK) model for Bayesian adaptive control.METHODS: Pediatric patients (n=17) with non-malignant disorders receiving subcutaneous alemtuzumab as a part of their preparative regimen were prospectively enrolled in our 'intensive sampling' PK study. The median age of patients was 7.0 years (3.0-11.0) and median weight was 32.2 kg (16.2-58.9). Alemtuzumab was subcutaneously administered starting on Day -14 at a dose of 0.2 mg/kg/day for 5 days (total dose of 1 mg/kg). Alemtuzumab plasma concentrations were quantified by validated flow cytometric assay. The plasma concentrations at pre-dose, 30 minutes, and 8 hours after each dose, followed by daily levels until Day 0 were used for PPK analysis. PPK analysis was performed using nonlinear mixed effects modeling (NONMEM, version 7.2). Bayesian estimation was conducted using MW/Pharm software (version 3.6).RESULTS: A one-compartment model with first order absorption best described the PK of alemtuzumab (Figure 1). Model fit was significantly improved by including body weight with allometric scaling for clearance and the volume of distribution (p<0.01). Goodness-of-fit plots did not show systematic bias. Model parameter estimates were within the 95% CIs of median values obtained by bootstrap analysis. Bayesian estimation with the developed PPK resulted in well predicted alemtuzumab concentration-time profiles in each patient (Figure 2).CONCLUSION:This is a first study to develop a PPK model of alemtuzumab after subcutaneous administration in pediatric transplant patients. Our model can be used for Bayesian estimation of individual PK to support alemtuzumab precision dosing in pediatric patients undergoing allogeneic HCT using the alemtuzumab, fludarabine, and melphalan containing RIC. Precision dosing of alemtuzumab will in turn optimize transplant outcomes for these high risk patients, by minimizing acute GVHD and mixed chimerism, along with improving post-HCT immune reconstitution. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Pharmacokinetics of Alemtuzumab Used as Conditioning Agent in Reduced Intensity Transplantation for Pediatric Non-Malignant Disorders.

Background: Alemtuzumab (Campath-1H), a depleting humanized monoclonal antibody against CD52 has been successfully used for immunosuppression in reduced intensity transplantation (RIT) for non-malignant disorders in children (Shenoy et al, BMT 2005). The conditioning regimen used in this study included alemtuzumab on days -22 to -19, fludarabine 150mg/m2/day on days -8 to -4, and melphalan 140 mg/m2 on day -3. Doses were reduced for children<10kg (fludarabine 1mg/kg/day, melphalan 4.7mg/kg). Stem cell sources included related or unrelated matched or single locus mismatched bone marrow, cord blood, or peripheral blood.Aims: Pharmacokinetics and clearance of alemtuzumab following conditioning for RIT as above were determined in serial fashion to correlate with transplant related outcomes. All recipients were children undergoing RIT for non-malignant disorders.Methods: Alemtuzumab levels were measured serially in 29 patients who received the above conditioning regimen and RIT for hemoglobinopathies, bone marrow failure syndromes, metabolic disorders, or immune deficiencies/dysregulation. Recipients ≥10 kg received a total dose of 48 mg of alemtuzumab; those <10 kg received 33 mg. Serum levels were determined using the Campath antigen CD52 fusion protein (TFYO. CAMG2A.A6.1F2) by ELISA at BioAnaLab, UK on batched frozen samples on day -19 (end of infusion), day 0, day +30, and day +100 post-transplant. Outcomes are reported by patient size and include graft-versus-host-disease (GVHD), infection, graft rejection (GR), and survival. Kinetics of lymphocyte function and subpopulation recovery were serially tracked for 1 year post-transplant.Results: Of 28 patients, 1 died of adenovirus infection prior to engraftment. Donor engraftment was present in 92.5% (25 of 27 patients). Of these, 11 patients were <10 kg (total alemtuzumab dose 33 mg) and 17 were ≥10 kg (total dose 48 mg). Table 1 shows median and range of doses administered per kg as well as pharmacokinetics and transplant outcomes classified by patient size. Alemtuzumab was detected on day +100 in 4 recipients. Overall mortality was 3.5%; Graft rejection occurred in 10.7% - all patients were in the >25 kg weight category; 36% developed aGVHD (grade 1 –4) (higher prevalence in larger recipients). Acute toxicities were predominantly bacterial and viral infections within the first 100 days after transplant and diminished significantly following immune reconstitution. Other toxicities included reversible autoimmune hemolytic anemia in 5 patients.Conclusions: Alemtuzumab doses between 2.1 and 7.4mg/kg were well tolerated in the transplant setting and resulted in stable engraftment and low incidence of mortality and GVHD. Alemtuzumab serum levels were variable even among children with similar weights and presumably depend on the recipient CD52+ cell load. Even when administered >2 weeks prior to transplant, alemtuzumab levels were detectable as late as 30–100 days post-transplant. There was a trend towards increased graft rejection with lower alemtuzumab dosing per kg body weight suggesting that a higher dose in larger patients could benefit transplant outcomes.# of patients (weight range in kg)Median dose (range) in mg/kg of drugMedian Level (range) in ng/ml on day -19Median Level (range) in ng/ml on day 0Median Level (range) in ng/ml on day 30MortalityAcute GVHD (grade 1–4)Graft RejectionDuration of follow up in months Median (range)11 (<10)4.8 (2.5–7.4)455.6 (33–4079)137.7 (<31–843)<31 (<31–915.6)1*2015.5 (2.5–30)6 (10–25)3.4 (2.15–4.6)480.3 (243.4–690.69)<31 (<31–672.6)75.8 (<31–312.9)05011 (3–12)11 (>25)1.1 (0.7–1.3)283.6 (31–11051)88.8 (<31–2239.5)<31 (<31–777.9)03314 (6–26)*died due to complications from adenovirus prior to engraftment

Pharmacokinetics of alemtuzumab in combination with fludarabine in patients with relapsed or refractory B-cell chronic lymphocytic leukemia

In recent years, chemoimmunotherapies that combine cytotoxic agents and monoclonal antibodies have been studied intensively for the treatment of B-cell chronic lymphocytic leukemia (CLL). Of particular interest are fludarabine-based combination regimens such as FluCam (fludarabine and alemtuzumab),

Consolidation Therapy with Subcutaneous (SC) Alemtuzumab Results in Severe Infectious Toxicity in Previously Untreated CLL Patients Who Achieve a Complete Response (CR) after Fludarabine and Rituximab (FR) Induction Therapy: Interim Safety Analysis of the CALGB Study 10101.

Alemtuzumab (Campath-1H) is approved for the treatment of fludarabine-refractory chronic lymphocytic leukemia (CLL). Given the increasing role of chemoimmunotherapy in the treatment of CLL, the Cancer and Leukemia Group B initiated a phase II study administering FR followed by alemtuzumab for remission consolidation to previously untreated, symptomatic CLL patients (pts). Pts received fludarabine 25 mg/m2 IV on days 1–5; rituximab 50 mg/m2 IV on day 1, 325 mg/m2 IV on day 3, and 375 mg/m2 IV on day 5 of cycle 1, and 375 mg/m2 IV on day 1 of cycles 2–6; every 28 days for up to 6 cycles. Four months after the last dose of fludarabine, pts with stable or responsive disease by NCI 96 response criteria received consolidation therapy with SC alemtuzumab 3 mg on day 1, 10 mg on day 3, 30 mg on day 5, and 30 mg thrice weekly thereafter for 6 weeks. Pts received standard pneumocystis (PCP) and Varicella Zoster Virus prophylaxis and were monitored weekly for Cytomegalovirus (CMV) reactivation by PCR, antigen test, or hybrid capture. We report safety data on the first 51 pts who received alemtuzumab. Median age was 60 years (range, 23–82), and 75% were male. Of 34 pts who attained an NCI 96 partial response (PR) after FR induction, 9 (26%) experienced unacceptable toxicity to alemtuzumab, as defined prospectively by the study. Eight grade 3 toxicities (4 opportunistic infections, 3 CMV reactivation, 1 hemorrhagic cystitis), and 1 grade 5 EBV lymphoproliferative disorder were observed. In contrast, 17 pts had CR after FR induction and 8 (47%) had unacceptable toxicity. Complications included grade 3 infections in 3 pts (2 CMV, 1 cryptococcus) and 5 grade 5 infections (viral meningitis, Listeria meningitis, Legionella pneumonia, CMV and PCP pneumonia). These infections occurred both during therapy and for up to 16 months following therapy. Analysis of alemtuzumab pharmacokinetics and genomic tumor features is currently ongoing. Continuous real-time safety monitoring prompted a study amendment to prohibit further pts in CR after FR induction from receiving alemtuzumab consolidation. Accrual of new pts to the trial is complete. Only pts in PR or with stable disease after FR induction continue to receive alemtuzumab consolidation, with close monitoring for infectious and other toxicities. Detailed response and outcome data will be reported when all pts have completed therapy. We conclude that alemtuzumab cannot be safely administered as consolidation therapy to pts who achieve an NCI 96 CR following induction chemoimmunotherapy. The safety and feasibility of alemtuzumab consolidation for pts in PR after FR induction remains under study, and such therapy should not be pursued outside of a clinical trial due to concerns about serious infectious morbidity and mortality.

Population pharmacokinetics–pharmacodynamics of alemtuzumab (Campath®) in patients with chronic lymphocytic leukaemia and its link to treatment response

To characterize alemtuzumab pharmacokinetics and its exposure-response relationship with white blood cell (WBC) count in patients with B-cell chronic lymphocytic leukaemia (CLL). Nonlinear mixed effects models were used to characterize plasma concentration-time data and WBC count-time data from 67 patients. Logistic regression was used to relate summary measures of drug exposure to tumour response. Alemtuzumab pharmacokinetics were best characterized by a two-compartment model with nonlinear elimination where V(max) (microg h(-1)) was [1020 x (WBC count/10 x 10(9) l(-1))(0.194)], K(m) was 338 microg l(-1), V(1) was 11.3 l, Q was 1.05 l h(-1) and V(2) was 41.5 l. Intersubject variability (ISV) in V(max), K(m), V(1) and V(2) was 32%, 145%, 84% and 179%, respectively. The reduction in WBC over time was modelled by a stimulatory loss indirect response model with values of 18.2 for E(max), 306 microg l(-1) for EC(50), 1.56 x 10(9) cells l(-1) h(-1) for K(in) and 0.029 per h for K(out). The probability of achieving a complete or partial response was >/=50% when the maximal trough concentration exceeded 13.2 microg ml(-1) or when AUC(0-tau) exceeded 484 microg h(-1) ml(-1). Alemtuzumab displayed time- and concentration-dependent pharmacokinetics with large interpatient variability, both in pharmacokinetics and pharmacodynamics, which was probably reflective of differences in tumour burden among patients. A direct relationship between maximal trough concentrations and clinical outcomes was observed, with increasing alemtuzumab exposure resulting in a greater probability of positive tumour response.

Pharmacokinetics of alemtuzumab after haploidentical HLA-mismatched hematopoietic stem cell transplantation using in vivo alemtuzumab with or without CD52-positive malignancies

We recently reported that the addition of in vivo alemtuzumab to the conditioning regimen enables 2- or 3-locus-mismatched hematopoietic stem cell transplantation without an excessive risk of graft rejection or graft-versus-host disease. In a later series of patients, however, one patient with refractory chronic lymphocytic leukemia with large residual tumors at transplantation developed graft rejection. While the peak alemtuzumab concentration in the previous patients without graft rejection was higher than 5 micro g/ml, the peak alemtuzumab concentration in this patient was only 1.44 micro g/ml. We considered that alemtuzumab was bound to the large residual tumors, which resulted in a low blood concentration of alemtuzumab. Therefore, it is important to debulk tumors before the conditioning regimen for patients with refractory CD52-positive hematological malignancies, or the dose of alemtuzumab should be adjusted by monitoring the blood concentration, when alemtuzumab is used for in vivo T-cell depletion in 2- or 3-locus-mismatched transplantation.

Population Pharmacokinetics of Alemtuzumab in Patients with Hematologic Malignancies.

Alemtuzumab (Campath®, MabCampath®) is a humanized IgG monoclonal antibody targeting the CD52 antigen and is approved for treatment of B-cell chronic lymphocytic leukemia (B-CLL) following treatment with alkylating agents and failing fludarabine treatment. Nonlinear mixed effects modeling was used to characterize the population pharmacokinetics in patients with NHL and CLL after both single dose and multiple dose treatment regimens (n = 118). Model building followed standard procedures. First, an appropriate structural model was identified. Covariate screening was undertaken using generalized additive models to identify those patient characteristics that influenced alemtuzumab pharmacokinetics. Covariates deemed important were then tested using a forward stepwise approach. Only those covariates deemed statistically significant at the 0.05 level were retained in the model. Once the final forward model was identified, the model was reduced using more stringent criteria to remain in the model (P <0.001). The final model was validated using an independent data set after data-splitting (80:20, n = 32). A secondary analysis was also performed using noncompartmental analysis of pharmacokinetic data obtained from only B-CLL patients (n = 16). A 2-compartment model with Michaelis-Menten elimination best characterized alemtuzumab pharmacokinetics. White blood cell (WBC) count significantly influenced the maximal rate of elimination (Vmax) in a linear manner, while body weight affected Vmax based on a power function. Central volume of distribution was proportional to patient weight, estimated at 7.6 L for a 70 kg patient. Distribution volume at steady-state (Vdss) was 0.18 L/kg. Vdss in B-CLL patients ranged from 0.09 to 0.40 L/kg (median, 0.15 L/kg). The Michaelis constant was estimated at 6.1 mg/mL. Due to nonlinear elimination kinetics, no single estimate for half-life can be reported. For a typical 70-kg patient with elevated WBC of 100 × 109 cells/L, receiving a first dose of 3 mg, the model-predicted half-life was ~8 hours. After a log-decline in WBC to 1.0 × 109 cells/L, the half-life increased to ~50 hours, and a further log-decline in WBCs to 0.1 × 109 cells/L, after 5 doses, resulted in a half-life of ~9 days (214 hours). In B-CLL patients (n = 8), individual observed half-life values after the first 30 mg dose ranged from 2 to 32 hours (median, 8.3 hours) and after the last 30 mg dose (n = 16) ranged from 1 to 14 days (median, ~6 days). Model validation resulted in comparable results, thus indicating the model parameters were consistent across data sets. In summary, alemtuzumab pharmacokinetics were weight-dependent, concentration-dependent, and WBC-dependent. As the number of CD52 expressing cells is depleted, which is reflected in a decrease of WBC and lymphocyte counts, alemtuzumab half-life increases. Also, as alemtuzumab concentrations increase, the maximal rate of elimination further decreases thereby increasing alemtuzumab's half-life to a value of ~6 days.

Pharmacokinetic Analysis of Subcutaneous Alemtuzumab as Consolidation Therapy To Achieve MRD-Negative Responses.

Persistence of minimal residual disease (MRD) after therapy has been shown to be a powerful prognostic factor for relapse among patients with chronic lymphocytic leukemia (CLL). Treatment with the anti-CD52 monoclonal antibody alemtuzumab (Campath®), either as a single agent or in combination with fludarabine, has been shown to induce MRD-negative responses, even among patients who are not responsive to traditional therapeutic interventions. Dramatically improved responses and MRD negativity have also been achieved using alemtuzumab as consolidation therapy, to purge MRD after initial therapy with a fludarabine-based regimen. The pharmacokinetics (PK) of alemtuzumab administered subcutaneously to achieve MRD negativity after induction therapy with fludarabine are reported here. Of 41 patients (median age, 54 years) who received consolidation therapy with alemtuzumab, all 16 patients participating in the PK analysis were MRD-positive after receiving induction therapy as measured by PCR consensus primer. At least 8 weeks following the completion of induction therapy, dose escalated alemtuzumab 10 mg was administered for 6 weeks, 3 times a week. Plasma samples were collected from 16 patients on Days 1, 3, 5, 15, 17, 22 and 31, and ELISA was used to assess the PK of alemtuzumab. On Day 15, blood samples were drawn at 1, 2, 3, 4, 6, 8 and 12 hours after alemtuzumab administration. Alemtuzumab plasma concentrations gradually increased during the first 2 weeks, and reached concentrations 25.5-fold higher on Week 3. The median pre-dose concentrations (Cpre-dose) were: 0.01 μg/mL (range, 0–0.07 μg/mL) on Day 3, 0.58 μg/mL (range, 0–1.2 μg/mL) on Day 15, 0.51 μg/mL (range, 0–2.61 μg/mL) on Day 17, and 1.09 μg/mL (range, 0.19–3.08 μg/mL) on Day 31. The median Cmax plasma concentration was 1.05 μg/mL (range, 0.097–1.75 μg/mL) and the median Cpre-dose was 0.58 μg/mL (range, 0–1.2 μg/mL). An analysis was performed to correlate quantitative response as represented by polyclonal complete remission and AUC0–12 values. Preliminary data indicate that the systemic exposure associated with effective therapy corresponds with an AUC0–12 value higher than 5 μg•h/mL on Day 15 of the administration schedule. Therefore, complete response (CR) rates, expressed as percentage of patients with AUC0–12 values correlating with effective treatment, increased with higher levels of systemic exposure to alemtuzumab.

Alemtuzumab (Campath 1-H) Exposure Correlates with Risk of Chronic Graft vs Host Disease and CMV Viremia after Allogeneic Transplantation.

Conditioning regimens using in vivo alemtuzumab (Campath-1H, humanized anti-CD52) are characterized by low rates of acute and chronic GVHD, but may also result in delayed immune reconstitution. Optimization of such regimens will depend on an understanding of the relation between alemtuzumab exposure, immune reconstitution and GVHD. We have conducted a prospective study of fludarabine 30 mg/m2/d x 5 days, melphalan 140 mg/m2 x 1 day and alemtuzumab 20 mg/d x 5 days as conditioning for related and unrelated allografts. Using an enzyme-linked immunosorbent assay (ELISA), we determined serum free and total Campath levels in 46 patients with hematologic malignancies (45) or sickle cell disease (1) on day 0, day 7, day 14, day 28, day 50, day 75, day 100, day 150 and at one year after transplant (HSCT). 26 (57%) had a matched sibling donor, 16 (35%) a matched unrelated donor (MUD) and 4 (9%) a mismatched related or unrelated donor. 44 pts engrafted and are included in the analysis.Median follow up for survivors was 2.8 years. Grade II–IV aGVHD occurred in 8 pts after a median of 42 days (range 22 to 60). Eight pts developed cGVHD after a median of 107 days (range 89–140). 15/41 (37%) at risk pts developed CMV reactivation. The half-life of free alemtuzumab (fA) was 26 days after HSCT with wide interpatient variation in fA pharmacokinetics (e.g. Coefficient of variation was 138% on day 0). On day 0, 1 patient had an undetectable level of fA. By day 28, 50, and 100, there were 6 (14.6%), 12 (35.3%), and 13 (52%) pts with undetectable fA, respectively. Figure 1 shows the fitted means and 95% confidence intervals of fA over time.Using log-rank and Cox proportional hazard models, there was no association between fA on day 0, day 28, or the last available fA, and development of acute GVHD. However, pts with higher average free and total Campath levels in the first month had a lower risk of developing cGVHD (p=0.02). The median fA concentration in the first month for pts with cGVHD was 0.32 (inter-quarter range IQR: 0.22–0.41), as compared with 0.97 (IQR: 0.23–3.31) in those without cGVHD.No significant association between absolute lymphocyte count and fA concentration was found after adjusting for time (p=0.28). Finally, among pts at risk, a higher fA concentration on day 0 (p=0.002), and in the first month (p=0.003) was significantly associated with CMV viremia.In summary, the estimated half-life of serum fA is 26 days after HSCT, but with considerable interpatient variability. Higher concentrations of fA were associated with a decreased incidence of cGVHD, but an increased risk of CMV reactivation. In contrast to a previous preliminary analysis, no association existed between fA and lymphocyte reconstitution. Variation in alemtuzumab pharmacokinetics may predict important clinical outcomes, such as cGVHD and CMV reactivation. Future studies are warranted to determine an optimal alemtuzumab exposure that hastens immune reconstitution while minimizing chronic GVHD. [Display omitted]

Low-dose alemtuzumab (Campath) in myeloablative allogeneic stem cell transplantation for CD52-positive malignancies: decreased incidence of acute graft-versus-host-disease with unique pharmacokinetics.

Alemtuzumab is effective in reducing the risk of acute graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (ASCT). Alemtuzumab may also delay immune reconstitution and reduce graft-versus-leukemia effects. The optimal dose has not been established. We investigated engraftment, acute GVHD incidence and severity, and pharmacokinetics of alemtuzumab associated with the use of low-dose alemtuzumab/cyclophosphamide/total body irradiation and ASCT for patients with aggressive CD52-positive hematologic malignancies. In all, 12 patients were treated. Alemtuzumab 10 mg daily on days -7 to -3 was given intravenously. Tacrolimus and methotrexate were used for GVHD prophylaxis. Alemtuzemab was not detected in any of the 36 sequential serum samples tested between days -1 and +21 of transplant. All patients engrafted rapidly; the median time to an absolute neutrophil count >0.5 x 10(9)/l was 14 days (range 11-17 days), and the median time to a platelet count >20 x 10(9)/l was 16 days (range 6-30 days). By 1 month after transplant, nine patients had 100% donor chimerism, while three had mixed donor chimerism. At 3 months, 11 had achieved 100% donor chimerism. No cases of grade III/IV acute GVHD occurred. At a median follow-up interval of 14.7 months (range 4-24), seven patients remained alive, and five remained free of disease.

Pharmacokinetics of alemtuzumab used for in vivo and in vitro T-cell depletion in allogeneic transplantations: relevance for early adoptive immunotherapy and infectious complications

AbstractPersistence of alemtuzumab at lympholytic concentrations after reduced-intensity conditioning allogeneic stem cell transplantations (RITs) could impair immune reconstitution and reduce donor T-cell–mediated graft-versus-leukemia/lymphoma (GVL) effects, derived from the graft or subsequent adoptive immunotherapy. We have studied the pharmacokinetics of alemtuzumab in 2 different groups: RIT (100 mg alemtuzumab in vivo over 5 days) and myeloablative allografts (20 mg alemtuzumab added in vitro to the stem cells prior to return). Alemtuzumab concentrations in RIT patients were in excess of that required to kill infused donor CD52+ cells at the time of transplantation and remained at potentially lympholytic levels (> 0.1 μg/mL) for approximately 56 days after transplantation, 26 days longer than for the myeloablative group. Total lymphocyte counts were significantly lower in the RIT group persisting beyond 6 months after transplantation (P = .005), and median absolute CD4 counts higher than 200 × 106/L were delayed until 9 months after transplantation. (Blood. 2003;102:404-406)