Clinical experience with moroctocog alfa (AF-CC) in younger paediatric patients with severe haemophilia A: Two open-label studies

INTRODUCTION

The pharmacokinetics (PK), efficacy and safety of moroctocog alfa (AF-CC) have been demonstrated in haemophilia A patients aged ≥6 years.

AIM

These studies aimed to further describe moroctocog alfa (AF-CC) experience in paediatric patients (<12 years) with severe haemophilia A (FVIII:C < 1%).

METHODS

Two prospective, open-label studies enrolled patients aged <12 years: one study with 37 previously treated patients (PTPs) and another with 23 previously untreated patients (PUPs). All patients initially received 50 IU/kg of moroctocog alfa (AF-CC) to evaluate either recovery alone, or with other PK parameters (6 to <12 years) before continuing treatment for 100 exposure days (EDs) or 24 months.

RESULTS

At baseline, mean (±SD) recovery ranged between 1.32 ± 0.65 (PUPs aged <2 years) and 2.13 ± 0.82 (PTPs aged 6 to <12 years). The mean (±SD) half-life was 9.12 ± 1.94 hours in PTPs aged 6 to <12 years. No new safety signals were detected in either study, 2 transient lower titre inhibitors occurred in PTPs while 8 inhibitors (3 low and 5 high titre) were detected in PUPs. Most bleeding episodes resolved with one infusion (94% [893/954]). The annualised bleeding rate (ABR) in the PTP study was 27.5 and 4.2 for patients reporting an on-demand and routine prophylaxis regimen at baseline, respectively. In the PUP study, the overall ABR was 5.9.

CONCLUSION

Moroctocog alfa (AF-CC) had expected PK findings (lower recovery in young children compared with older children) along with being safe and efficacious in a population of young severe haemophilia A patients.

Use of pharmacokinetics in the coagulation factor treatment of patients with haemophilia

Dosing decisions for replacement coagulation factors in patients with haemophilia should be made on an individual patient basis, with the required dose dependent on factors including the clinical situation, the severity of the factor deficiency, and the location and extent of bleeding. Moreover, there is considerable variability in the pharmacokinetics of coagulation products that needs to be considered; in particular, with both factor (F) IX and FVIII products, there is considerable inter-patient variability in in vivo recovery and terminal half-life values. In the present report, we provide a practical guide to calculating and applying pharmacokinetic parameters relevant to the optimal dosing of coagulation products. We discuss the conduct of a pharmacokinetic study in an individual patient, how to calculate pharmacokinetic values from raw data and clinical situations where an individual pharmacokinetic study is helpful. We highlight the importance of considering an individual pharmacokinetic study in all patients starting a new coagulation product.

Pharmacokinetics of gemtuzumab ozogamicin, an antibody-targeted chemotherapy agent for the treatment of patients with acute myeloid leukemia in first relapse

The purpose of this study was to characterize the pharmacokinetics of gemtuzumab ozogamicin (Mylotarg; Wyeth-Ayerst Laboratories, St. Davids, PA) in patients with acute myeloid leukemia (AML) in first relapse. Gemtuzumab ozogamicin is an antibody-chemotherapeutic conjugate characterized as antibody-targeted chemotherapy, consisting of an engineered human anti-CD33 antibody (hP67.6) linked to a potent cytotoxic agent, N-acetyl-gamma calicheamicin DMH. The pharmacokinetics of gemtuzumab ozogamicin was evaluated in 59 adult AML patients in first relapse, enrolled in a phase II study. Plasma was collected following each dose at specified times, and the pharmacokinetics was characterized by measures of hP67.6, total calicheamicin derivatives, and unconjugated calicheamicin derivatives. After administration of the first 9 mg/m2 dose of gemtuzumab ozogamicin, the pharmacokinetic parameters (mean +/- SD) of hP67.6 following the first dose were as follows: peak plasma concentration, 2.86 +/- 1.35 mg/L; AUC, 123 +/- 105 mg x h/L; t 1/2, 72.4 +/- 42.0 hours; and clearance, 0.265 +/- 0.229L/h. Increased concentrations were observed after the second dose and are believed to be due to a decrease in clearance by CD33-positive blast cells, a result of the reduced tumor burden following the first dose. The concentration profiles of calicheamicin followed the same time course as hP67.6, evidence that calicheamicin remained conjugated to the antibody and delivered to leukemic cells. No relationship was found between plasma concentration and response at the recommended dose. The pharmacokinetics of gemtuzumab ozogamicin has been characterized in AML patients receiving doses at the proposed therapeutic level.

Evaluating possible pharmacokinetic interactions between tobramycin, piperacillin, and a combination of piperacillin and tazobactam in patients with various degrees of renal impairment

A study was performed to further investigate the apparent instability of tobramycin when coadministered with piperacillin/tazobactam in subjects with renal impairment. Twenty-six otherwise healthy volunteers between 23 and 74 years of age were studied. Eight subjects had moderate renal impairment, 10 had mild renal impairment, and 8 had normal renal function. Each subject received single doses of piperacillin/tazobactam and tobramycin alone as well as combined doses in a randomized, three-way crossover design. The subjects with normal renal function also received combined doses of piperacillin and tobramycin. Considerable care was taken to protect against in vitro inactivation of plasma and urine samples after collection. No systematic changes in pharmacokinetic parameters were observed. It is concluded that piperacillin, either alone or with tazobactam, did not change the pharmacokinetics of tobramycin in subjects with renal impairment. The apparent in vivo inactivation of tobramycin in the presence of piperacillin or piperacillin/tazobactam reported by others may be an artifact of ex vivo inactivation.

Pharmacokinetic and pharmacodynamic action of etodolac in patients after oral surgery

The objective of this double-blind, randomized, parallel-group study was to evaluate the pharmacokinetics of etodolac and the pharmacodynamic response of pain in patients following oral surgery who had received 200 or 400 mg of etodolac immediate release (IR), 400 or 1200 mg of etodolac extended release (ER), or a placebo. Etodolac concentrations in 441 plasma samples from 187 patients were analyzed for population pharmacokinetics using the NONMEM program. A one-compartment pharmacokinetic model with first-order absorption described the observed data. For etodolac IR, the population mean (%CV) estimates were 3.01 L/h (5.3%) for clearance, 13.6 L (6.8%) for volume of distribution, and 2.31 h-1 (33%) for ka. Respective values for etodolac ER were 3.68 L/h (11%) for clearance, 24.3 L (22%) for volume of distribution, and 0.172 h-1 (24%) for ka. These values generally agreed with previously reported values in healthy adults. Pharmacodynamic assessments included collection of a four-level categorical rating of pain intensity for up to 24 hours after treatment. Pain intensity difference scores were temporally related to etodolac concentrations and were described using an indirect response model. Mean (%CV) pharmacodynamic parameters were IC50 of 14.0 mg/L (9.5%), kout of 1.62 h-1 (13%), FR of 0.56 (8.2%), and Hill coefficients that ranged from 1.26 to 3.34 units. A single 1200 mg dose of etodolac ER given once daily was shown to provide substantial efficacy for 13 hours after dose, modest effect through 24 hours, and a more sustained duration of action than the IR dosage form.

Population pharmacokinetics of intravenous amiodarone and comparison with two-stage pharmacokinetic analysis

The disposition of amiodarone, an antiarrhythmic agent was evaluated after a single intravenous infusion (5 mg/kg over 15 minutes) in patients of various ages and with various degrees of renal function and left ventricular function. The plasma concentration-time data were obtained from three clinical studies with similar protocols. The data were analyzed by nonlinear mixed-effects modeling (NONMEM) to estimate the population pharmacokinetic parameters of amiodarone and to determine the significant demographic covariates affecting these parameters. The pharmacokinetic parameters of amiodarone (weight-corrected) also were calculated using two-stage analysis and were compared with the results obtained from the mixed-effects analysis. The population plasma concentration-time profile of amiodarone was best described by a four-compartment model. Demographic covariates (i.e., creatinine clearance and ejection fraction) did not improve the final pharmacostatistical model significantly. The results from the two-stage analysis showed no significant relationship between amiodarone pharmacokinetic parameters and age, gender, renal function, or ejection fraction. The results from one study, however, demonstrated that advanced age (> or = 65 years) resulted in reduced amiodarone clearance coupled with a prolonged elimination half-life. No such correlation was detected with NONMEM analysis, which may be partly attributable to the small number of elderly patients. Overall, the results from NONMEM analysis validated the results obtained from the two-stage analysis.