First open-label, single-arm, prospective study of real-world use of FIX replacement therapy in a predominantly pediatric hemophilia B population in China

BACKGROUND

Nonacog alfa (recombinant factor IX [FIX]) is approved in China for the control and prevention of bleeding events in patients with hemophilia B. This was the first study to assess prophylaxis and on-demand therapy with recombinant FIX replacement in a real-world setting in China. This study aimed to evaluate the safety and efficacy of nonacog alfa in Chinese patients with hemophilia B.

METHODS

In this open-label, multicenter study (clinicaltrials.gov identifier NCT02336178), patients received on-demand or prophylactic treatment with intravenous nonacog alfa for approximately 6 months or 50 exposure days, whichever occurred first. The primary safety outcome was medically important events (i.e., development of FIX inhibitors, allergic reactions, and thrombotic events). Key secondary efficacy outcomes included the annualized bleeding rate for on-demand treatment and prophylaxis, response to on-demand treatment, the number of infusions per bleeding event, and the number of breakthrough bleeding events within 48 hours of prophylaxis.

RESULTS

Seventy male patients (mean [standard deviation] age 7.8 [7.2] years) were enrolled (on-demand, n = 37; prophylaxis, n = 57 [24 patients were included in both groups]). Thirty-eight (54%) patients had up to 50 FIX exposure days before the study. The only medically important event was a transient low-titer FIX inhibitor (incidence 1.4%, 95% confidence interval, 0-7.7). The mean annualized bleeding rate was 26.3 for on-demand treatment and 6.5 for prophylaxis. A mean (standard deviation) of 1.5 (1.7) nonacog alfa infusions were given per bleeding episode; 78.8% of episodes resolved with 1 infusion. Response was "excellent" or "good" for 88% of the on-demand infusions. Twenty-three bleeding events (n = 11 patients) occurred within 48 hours of 2032 prophylaxis doses (1.13%).

CONCLUSION

In the real-world setting, nonacog alfa is safe and effective for on-demand treatment and for prophylaxis for patients with hemophilia B in China.

Safety and Efficacy of Moroctocog Alfa (AF-CC) in Chinese Patients with Hemophilia A: Results of Two Open-Label Studies

Introduction

Moroctocog alfa albumin-free cell culture (AF-CC) increases plasma levels of factor VIII (FVIII) activity and, in China, is indicated for the control and prevention of bleeding episodes in patients with hemophilia A. This study aimed to evaluate the efficacy, safety, and recovery data of moroctocog alfa (AF-CC) in patients with hemophilia participating in two open-label studies, both conducted in China.

Methods

The authorization study (clinicaltrials.gov identifier NCT00868530) enrolled patients aged ≥6 years, previously treated with ≥1 exposure day of FVIII replacement therapy. The real-world study (clinicaltrials.gov identifier NCT02492984) enrolled patients of any age who were previously untreated or requiring surgical prophylaxis. In both studies, on-demand treatment was administered over 6 months. Key assessments included response to treatment, FVIII inhibitor development, and recovery.

Results

In the authorization study (N = 53; mean age, 23.2 years; severe hemophilia, 23%), response was excellent/good for 90% of infusions at 24 hours. Seven patients developed inhibitors. Mean (SD) FVIII recovery at the initial and final visits was 1.77 (0.50) and 1.67 (0.45) (IU/dL)/(IU/kg), respectively. In the real-world study (N = 85; mean age, 9.5 years; severe hemophilia, 58%), response was rated as excellent or good for most (87%) on-demand infusions and for all surgical prophylaxis patients (n = 14). Seven patients developed FVIII inhibitors. Mean (SD) FVIII recovery at the initial and final visits was 1.71 (0.50) and 1.68 (0.31) (IU/dL)/(IU/kg), respectively. No new safety signals were observed in either study.

Conclusion

On-demand treatment and surgical prophylaxis with moroctocog alfa (AF-CC) is safe and effective for both previously treated and previously untreated Chinese patients with hemophilia A.

Effect of Renal or Hepatic Impairment on the Pharmacokinetics, Safety, and Tolerability of Intravenous Rivipansel

Two studies evaluated the effects of renal and hepatic impairment on pharmacokinetics and safety of rivipansel (NCT02813798, NCT02871570). A single intravenous 840-mg rivipansel dose was administered to subjects with renal impairment or normal renal function in study 1005 and subjects with moderate hepatic impairment or normal hepatic function in study 1006. Plasma (both studies) and urine (study 1005) samples were collected for 96 hours postdose. All subjects in studies 1005 (n = 28) and 1006 (n = 16) completed all study procedures. Rivipansel exposure (AUC_inf ) was 47%, 124%, and 437% higher and total clearance 30%, 57%, and 82% lower in the mild, moderate, and severe renal impairment groups, respectively, than in the normal renal function group. Overall rivipansel exposure was 20% lower and total clearance 31% higher in the moderate hepatic impairment group than in the normal hepatic function group. Ten treatment-emergent adverse events occurred in studies 1005 and 1006; no event was considered treatment related. As expected, clearance of rivipansel decreased with increasing renal impairment. The difference observed between rivipansel pharmacokinetics in subjects with moderate hepatic impairment and subjects with normal hepatic function was not considered clinically significant. Single doses of rivipansel were well tolerated in subjects with either renal or hepatic impairment.

The Path to Perfect Pediatric Posology - Drug Development in Pediatrics

Reluctance to enroll pediatric subjects in clinical trials has left gaps in information about dosing, safety, and efficacy of medications. Pharmacotherapeutic information for pediatric patients may be available for only a small range of ages and may be deficient, as children respond differently as they grow and mature from prematurity to adolescence. Current regulations, however, require early planning for the participation of children in drug development, as pediatric plans must be submitted at the end of phase 1 (European Union) or the end of phase 2 (United States). These plans are extensive, outlining planned studies, subjects to be enrolled, dose and dosage form justification, planned observations, and statistical analysis as well as planned modeling, simulation, and extrapolation analyses. The extent to which efficacy information in adults can be extrapolated to children depends on how similar the disease is in adults and each of the 5 pediatric age groups. Extrapolation may not be possible for conditions that do not occur in adults, requiring a complete development plan in adults, or extrapolation may be complete because of similar pathology and response to treatment. Pharmacokinetic and safety information cannot be extrapolated and must be collected in children of all ages, unless a waiver is granted. Physiologically based pharmacokinetic modeling, optimal design, population pharmacokinetics, and scavenged samples are all examples of new methodologies being used to study pediatric therapeutics. Clinicaltrials.gov and EU Clinical Trials registry are good sources of results of pediatric trials, although sponsors are also working toward prompt publication of study results in peer-reviewed journals.

An Open-label, Single-dose, Pharmacokinetic Study of Factor VIII Activity After Administration of Moroctocog Alfa (AF-CC) in Male Chinese Patients With Hemophilia A

PURPOSE

Hemophilia A represents up to 80% of all hemophilia cases in China. In patients with this condition, bleeding can be prevented and controlled by administering clotting factor VIII (FVIII). Since their initial availability, recombinant FVIII products have undergone several iterations to enhance their safety. Moroctocog alfa albumin-free cell culture (AF-CC) is among the third generation of recombinant FVIII products and received regulatory approval in China in August 2012. The present study characterizes the single-dose pharmacokinetic parameters of FVIII activity (FVIII:C) after administration of moroctocog alfa (AF-CC) in male Chinese patients with hemophilia A.

METHODS

This multicenter, open-label, single-dose study enrolled 13 male Chinese patients diagnosed with severe hemophilia A (FVIII:C <1%) and a history of at least 150 exposure-days to any FVIII-containing product. Eligible patients received a single dose of moroctocog alfa (AF-CC) 50 IU/kg IV within 10 minutes. Blood samples were collected within 2 hours before administration and through 72 hours after dosing.

FINDINGS

Pharmacokinetic parameters were assessed based on FVIII:C and were analyzed by age groups: ages 6 to <12 years (n = 3) and ≥12 years (n = 10). The mean plasma concentration-time profile for FVIII:C activity was consistently lower in patients aged 6 to <12 years compared with those aged ≥12 years. Geometric AUC_0-∞ and C_max were approximately 57% and 28% lower in the younger patients relative to the older patients, respectively. A total of 4 adverse events occurred in 4 patients. Low-titer, transient FVIII inhibitors were observed in 2 patients and were considered serious adverse events. Neither case resulted in clinical manifestations nor required treatment.

IMPLICATIONS

This is the first report of the pharmacokinetic parameters of FVIII:C after moroctocog alfa (AF-CC) in an all-Chinese population of males with hemophilia A. The pharmacokinetic profile in older patients was similar to that previously reported with recombinant FVIII products in studies with a predominantly white population; younger patients had reduced exposure to FVIII:C. The single doses of moroctocog alfa (AF-CC) were well tolerated; 2 cases of transient, low-titer FVIII inhibitor development were observed. ClinicalTrials.gov identifier: NCT02461992.

Lack of Effect of Rivipansel on QTc Interval in Healthy Adult African American Male Subjects

Rivipansel is a pan-selectin inhibitor in phase 3 development for the treatment of vaso-occlusive crises in patients with sickle cell disease. This single-dose, randomized, 3-period, 3-treatment (400 mg moxifloxacin open-label, 4 g rivipansel-blinded, and placebo-blinded) crossover study evaluated the effect of rivipansel on the QT/QTc interval in 48 healthy male African American subjects (age, 21-53 years; weight, 60-115 kg). Time-matched, placebo-adjusted change from baseline QT interval using Fridericia's correction method (QTcF) was determined using a repeated-measures mixed-effects model. The highest upper bound of the 2-sided 90% confidence interval (CI) for QTcF change was 3.22 milliseconds 3 hours postdose. Moxifloxacin showed the anticipated QTcF effect, indicating that the study had adequate sensitivity to detect changes in the QTcF interval. The study concluded that no QTcF effect was demonstrated with rivipansel compared with placebo, as the upper bound of the 2-sided 90%CI was less than 10 milliseconds at all times. Exposure-response modeling for rivipansel concentrations and change from baseline in QTcF data corroborated a lack of effect with rivipansel compared with placebo. Single doses of rivipansel 4 g by intravenous infusion over 20 minutes were well tolerated in this study.

Confirmation of longer FIX activity half-life with prolonged sample collection after single doses of nonacog alfa in patients with haemophilia B

A multicentre, single-dose study enrolled 12 previously treated patients with moderately severe to severe (factor IX [FIX] levels ≤2 IU/dl) haemophilia B to assess FIX pharmacokinetics after nonacog alfa administration and to evaluate the impact of length of sampling time on half-life (t_½). After refraining from FIX replacement for four days, patients received 50 IU/kg as an intravenous (IV) infusion over 10 minutes. Blood samples were collected predose and 0.25, 0.5, 1, 3, 6, 9, 24, 50, 72, and 96 h post dose. Tolerability and safety were assessed by monitoring adverse events and were subsequently summary tabulated. FIX activity was measured by a one-stage clotting assay with a lower limit of quantification of 0.010 IU/ml, and inhibitors to FIX were measured using the Bethesda assay. Pharmacokinetic parameters were calculated by noncompartmental analysis and were descriptively summarised. Half-life estimates were calculated first using all available data, then excluding 96-h observations (truncated at 72 h) and, finally, excluding both 72- and 96-h observations (truncated at 50 h). No patient was positive for FIX inhibitors. No treatment-emergent adverse events were reported. Prolonging the duration of the sample collection to 96 h resulted in a terminal t_½ estimate of 39.6 ±7.4 h in the eight patients aged 18 years and older, which was longer than the estimates obtained using shorter periods of observation: 29.6 ± 5.5 h (truncated at 72 h) and 27.2 ± 7.0 h (truncated at 50 h). To accurately assess an adult patient's t_½, sampling should be continued for at least 96 h.

Relative Bioavailability of Liquid and Tablet Formulations of the Antiparasitic Moxidectin

The antiparasitic agent moxidectin is under development for the treatment of onchocerciasis. As the first-in-human study of moxidectin used a liquid formulation but other trials used tablets, a study was performed to determine the relative bioavailability of the 2 formulations and to gain more information about the pharmacokinetics of moxidectin. Fifty-eight healthy male participants were randomized to receive open-label moxidectin (10 mg) as a tablet (n = 29) or liquid (n = 29) formulation. The mean ± SD pharmacokinetic parameters observed following administration of the tablet were peak concentration (Cmax) 67.1 ± 27.4 ng/mL, time to peak concentration (tmax) 3.2 ± 1.4 hours, area under the concentration time curve (AUC) 4403 ± 2360 ng·h/mL, apparent volume of distribution 3635 ± 1720 L, oral clearance 2.83 ± 1.25 L/h, and elimination half-life 1032 ± 502 hours. The Cmax and AUC observed following administration of the liquid formulation were 28.6% and 28.8% higher, respectively, and tmax 0.9 hours shorter compared with tablets. No serious adverse events (AEs) were observed. The most commonly reported AEs were headache, infection, diarrhea, asthenia, myalgia, and dizziness during the inpatient phase and flu syndrome, headache, and infection during the 6-month outpatient phase. There was no difference in reporting of these AEs between formulations.

Long-term evaluation of analytical methods used in sirolimus therapeutic drug monitoring

Results of therapeutic monitoring of sirolimus blood concentrations are assay and laboratory dependent. This study compared performance over time of the IMx microparticle enzyme immunoassay (MEIA), Architect chemiluminescent microparticle immunoassay (CMIA), and liquid chromatography with mass spectrometric detection (LC/MS/MS) as part of a proficiency testing scheme. Pooled samples from sirolimus-treated patients and whole-blood samples spiked with known quantities of sirolimus were assayed monthly between 2004 and 2012. When results of pooled patient samples were compared with LC/MS/MS, the MEIA assay showed an overall mean percent bias of -2.3% ± 11.2% that, although initially positive, became increasingly negative from 2007 through 2009. The CMIA, which replaced the MEIA assay, had a mean percent bias of 21.9% ± 12.3%, remaining stable from 2007 through 2012. Similarly, for spiked samples, the MEIA showed an increasingly negative bias over time vs. LC/MS/MS, whereas CMIA maintained a stable positive bias. Based on comparison of immunoassay measurements on individual patient samples, CMIA values were more than 25% higher than MEIA values. These results highlight the importance of continued proficiency testing and regular monitoring of sirolimus assay performance. Clinicians must be aware of the methodology used and adjust target levels accordingly to avoid potential effects on efficacy and toxicity.

Multicentre, randomized, open-label study of on-demand treatment with two prophylaxis regimens of recombinant coagulation factor IX in haemophilia B subjects

Few randomized studies have reported on the use of factor IX (FIX) for secondary prophylaxis in haemophilia B patients. This study aimed to evaluate the efficacy and safety of two secondary prophylaxis regimens of recombinant coagulation FIX, nonacog alfa, compared with on-demand therapy. Male subjects aged 6-65 years with severe or moderately severe haemophilia B (FIX:C ≤ 2, n = 50) and ≥12 bleeding episodes (including ≥6 haemarthroses episodes) within 12 months of study participation were enrolled in this multicentre, randomized, open-label, four-period crossover trial. The primary measure was the annualized bleeding rate (ABR) of two prophylactic regimens vs. on-demand therapy. In the intent-to-treat group, mean ABR values were 35.1, 2.6 and 4.6 for the first on-demand period, the 50 IU kg(-1) twice-weekly period, and the 100 IU kg(-1) once-weekly period respectively. Differences in ABR between the first on-demand period and both prophylaxis regimens were significant (P < 0.0001); no significant differences were observed between prophylaxis regimens (P = 0.22). Seven serious adverse events occurred in five subjects, none related to study drug. Results demonstrated that secondary prophylaxis therapy with nonacog alfa 50 IU kg(-1) twice weekly or 100 IU kg(-1) once weekly reduced ABR by 89.4% relative to on-demand treatment. Both prophylaxis regimens demonstrated favourable safety profiles in subjects with haemophilia B.

Pancreatitis in tigecycline Phase 3 and 4 clinical studies

Objectives

To examine the incidence of pancreatitis among subjects enrolled in the tigecycline clinical trial programme, summarize cases and examine concomitant use of other pancreatitis-causing medications.

Methods

Subject data from Phase 3 and 4 comparative tigecycline studies were included in the analysis; investigator-reported adverse events of ‘pancreatitis’, ‘necrotizing pancreatitis’ or ‘pancreas disorder’ were reviewed. Data were summarized and cases were reported. No statistical comparisons were made. The incidence of overall pancreatitis with 95% CIs was calculated. The Wilson score method was used to calculate CIs.

Results

Nineteen subjects with investigator-determined pancreatitis were identified from the programme database, which included 3788 subjects treated with tigecycline and 3646 subjects treated with a comparator. There were 9 cases identified among the tigecycline-treated subjects [9 of 3788 (0.24%; 95% CI, 0.11–0.45)] and 10 cases among the comparator-treated subjects [10 of 3646 (0.27%; 95% CI, 0.13–0.50)]. The demographic characteristics of the subjects with pancreatitis were similar between treatment groups. The median duration of tigecycline therapy was 8.0 days compared with 11.0 days of comparator treatment. Concomitant or prior exposure to a Badalov class I medication was evident in the majority of subjects who developed pancreatitis. A numerically higher number of tigecycline-treated subjects were exposed to furosemide prior to the onset of pancreatitis than comparator-treated subjects.

Conclusions

Pancreatitis was uncommon in subjects treated with tigecycline, with an occurrence of <1%. Concomitant medications known to cause pancreatitis should be considered when prescribing tigecycline, but may not identify those at risk of developing pancreatitis.

Effect of moxidectin on CYP3A4 activity as evaluated by oral midazolam pharmacokinetics in healthy subjects

In order to evaluate the potential for CYP3A4 induction by moxidectin, midazolam pharmacokinetic (PK) parameters were compared before and after moxidectin administration. Healthy subjects received a single 8 mg dose of moxidectin and 3 single 7.5 mg doses of midazolam 3 days before, and 7 and 89 days after the moxidectin. Blood samples were taken for 24 hours to measure midazolam and metabolites in plasma, and for 89 days to measure moxidectin in plasma after dose administration. Noncompartmental PK analyses were performed for each analyte. Analysis of variance was performed on log-transformed midazolam parameters with treatment day as a fixed effect. Adverse events were recorded and laboratory tests, physical examinations, pulse oximetry monitoring, vital sign measurement, and electrocardiograms performed. Thirty-nine subjects were enrolled in the study; PK data were available for 37 subjects. Moxidectin PK parameters were similar to previous studies. There were no significant changes in PK for midazolam or its metabolites 7 or 89 days after moxidectin administration. Adverse events were generally mild and there were no relevant changes in safety assessments. Thus, 8 mg moxidectin does not induce CYP3A4 activity and other CYP3A4 substrates are unlikely to be affected by moxidectin co-administration.

The effect of rifampin on the pharmacokinetics of sirolimus in healthy volunteers

Sirolimus, metabolized primarily by intestinal and hepatic CYP3A4, is a substrate for P-glycoprotein. CYP3A4 inducers would be expected to decrease sirolimus exposure. This open-label, nonrandomized study investigated effects of CYP3A4 induction, by rifampin, on sirolimus pharmacokinetics. Healthy volunteers received sirolimus 20 mg on day 1. After washout period, multiple 600-mg rifampin doses were administered daily for 14 days. On day 9, one 20-mg sirolimus dose was administered after an overnight fast (≥10 hours). Whole blood samples for sirolimus collected for 144 hours after each dose were analyzed by liquid chromatography/tandem mass spectrometry. Pharmacokinetic parameters, assessed using noncompartmental methods, were compared using analysis of variance. Geometric mean ratios of Cmax and AUCinf were 29% (90% CI: 26, 32%) and 18% (90% CI: 16, 21%), respectively, with rifampin co-administration versus sirolimus alone. Corresponding decreases in Cmax and AUC were 71% and 82%, respectively, which would likely cause trough concentrations to fall below the recommended therapeutic range. Mean CL/F increased approximately fivefold with rifampin versus sirolimus alone. Co-administering sirolimus and potent CYP3A inducers is not recommended. If co-administration is necessary, dose adjustment and concentration monitoring should be conducted.

Tigecycline does not prolong corrected QT intervals in healthy subjects

We evaluated the effect of tigecycline (50-mg and 200-mg doses) on corrected QT (QTc) intervals and assessed safety and tolerability in a randomized, placebo-controlled, four-period crossover study of 48 (44 male) healthy volunteers aged 22 to 53 years. Fed subjects received tigecycline (50 mg or 200 mg) or placebo in a blinded fashion or an open-label oral dose of moxifloxacin (400 mg) after 1 liter of intravenous fluid. Serial electrocardiograms were recorded before, and for 96 h after, dosing. Blood samples for tigecycline pharmacokinetics were collected after each recording. QTc intervals were corrected using Fridericia's correction (QTcF). Pharmacokinetic parameters were calculated using noncompartmental methods with potential relationships examined using linear mixed-effects modeling. Adverse events were recorded. The upper limits of the 90% confidence interval for the mean difference between both tigecycline doses and placebo for all time-matched QTcF interval changes from baseline were <5 ms. The tigecycline concentrations initially declined rapidly and then more slowly. In the group given 50 mg of tigecycline, the pharmacokinetic parameters and means were as follows: maximum concentration of drug in serum (C(max)), 432 ng/ml; area under the concentration-time curve from time zero extrapolated to infinity (AUC0-∞), 2,366 ng · h/ml; clearance (CL), 21.1 liters/h; volume of distribution at steady state (V(ss)), 610 liters; and terminal half-life (t(1/2)), 22.1 h. Proportional or similar values were found for the group given 200 mg of tigecycline. Linear mixed-effects modeling failed to show an effect on QTcF values by tigecycline concentrations (P = 0.755). Tigecycline does not prolong the QTc interval in healthy subjects. This study has been registered at ClinicalTrials.gov under registration no. NCT01287793.

Population Pharmacokinetics of Tigecycline in Healthy Volunteers

Tigecycline, a novel glycylcycline, possesses broad-spectrum antimicrobial activity. A structural population pharmacokinetic model for tigecycline was developed based on data pooled from 5 phase I studies. Intravenous tigecycline was administered as single (12.5-300 mg) or multiple (25-100 mg) doses every 12 hours for up to 10 days. Three-compartment models with zero-order input and first-order elimination separately described the single- or multiple-dose full-profile data. Additional models were evaluated using a subset of the phase I data mimicking the phase II/III trial sparse-sampling scheme and dosage. A 2-compartment model best described the reduced phase I data following single or multiple doses and provided reliably accurate estimates of tigecycline AUC(0-12). This modeling supported phase II/III population pharmacokinetic model development to further determine individual patient tigecycline exposures for safety and efficacy analyses.

Comparative Sirolimus Pharmacokinetics After Single-Dose Administration of Two Prototype 0.5-mg Tablets in Healthy Volunteers

Availability of a lower dose tablet would add to the dosing flexibility of currently available 1- and 2-mg sirolimus tablets for optimal concentrations and patient compliance. A randomized, 3-period crossover study was conducted in 30 fasting healthy volunteers (29 men, aged 31 ± 8 years, weight 79 ± 12 kg). Subjects were given 5 mg of sirolimus, either as doses of the 0.5-mg nonshellac-core prototype, 0.5-mg shellac-core prototype, or approved 1-mg tablet. Whole blood samples were collected at selected time points for 144 hours after dosing and analyzed using LC/MS/MS assay. Noncompartmental pharmacokinetic analysis was performed, followed by bioequivalence assessment. Twenty-four subjects completed all dosing periods, and no formulation-associated adverse events were reported. Ratios of maximum plasma concentration (Cmax ), area under the concentration-time curve to the last measured concentration (AUCT ), and area under the concentration-time curve from time 0 to infinity (AUC) for the nonshellac-core prototype compared with the 1-mg tablet were within the 80% to 125% range dictated by bioequivalence conventions. Similar results were observed when comparing the ratios of AUCT and AUC for the shellac-core prototype, while 90% confidence interval of the ratio of Cmax values was 105% to 129%. Within the context of clinical equivalence standards established by a phase 3 study comparing liquid to tablet formulations, it was concluded that both prototypes were clinically bioequivalent to the reference formulation.

The effect of a high-fat breakfast on the pharmacokinetics of moxidectin in healthy male subjects: a randomized phase I trial

The objective of this study was to assess the effect of a high-fat meal on the pharmacokinetics of moxidectin. Healthy male subjects were randomized to receive single oral 8 mg doses of moxidectin after an overnight fast or high-fat breakfast. In fasted subjects (N = 27), mean [SD] parameters were C(max): 58.9 [12.5] ng/mL; t(max): 3.7 [1.5] h; area under concentration-time curve (AUC): 3,387 [1,328] ng/h/mL; Vλ(z)/F: 2,829 [1,267] L; CL/F: 2.76 [1.28] L/h; and t(1/2): 784 [347] h. Compared with fasted subjects, fed subjects (N = 27) exhibited a 34% increase in C(max), delay in t(max) to 5.3 [2.1] h, 44% increase in AUC, 40% decrease in Vλ(z)/F, and a 35% decrease in CL/F. There was no significant change in t(1/2). The changes are consistent with an increase in moxidectin bioavailability following administration with food. There were no clinically relevant changes in vital signs, laboratory tests, or electrocardiograms.

Tigecycline pharmacokinetics in subjects with various degrees of renal function

The pharmacokinetic parameters of tigecycline were assessed in subjects with severe renal impairment (creatinine clearance <30 mL/min, n = 6), subjects receiving hemodialysis (4 received tigecycline before and 4 received tigecycline after hemodialysis), and subjects with age-adjusted, normal renal function (n = 6) after administration of single 100-mg doses. Serial serum and urine samples were collected and assayed using validated liquid chromatography with tandem mass spectrometer (LC/MS/MS) methods. Concentration-time data were then analyzed using noncompartmental pharmacokinetic methods. Tigecycline renal clearance in subjects with normal renal function represented approximately 20% of total systemic clearance. Tigecycline clearance was reduced by approximately 20%, and area under the tigecycline concentration-time curve increased by approximately 30% in subjects with severe renal impairment. Tigecycline was not efficiently removed by dialysis; thus, it can be administered without regard to timing of hemodialysis. Based on these pharmacokinetic data, tigecycline requires no dosage adjustment in patients with renal impairment.

Comparison of tigecycline with imipenem/cilastatin for the treatment of hospital-acquired pneumonia

To compare efficacy and safety of a tigecycline regimen with an imipenem/cilastatin regimen in hospital-acquired pneumonia patients, a phase 3, multicenter, randomized, double-blind, study evaluated 945 patients. Coprimary end points were clinical response in clinically evaluable (CE) and clinical modified intent-to-treat (c-mITT) populations at test-of-cure. Cure rates were 67.9% for tigecycline and 78.2% for imipenem (CE patients) and 62.7% and 67.6% (c-mITT patients), respectively. A statistical interaction occurred between ventilator-associated pneumonia (VAP) and non-VAP subgroups, with significantly lower cure rates in tigecycline VAP patients compared to imipenem; in non-VAP patients, tigecycline was noninferior to imipenem. Overall mortality did not differ between the tigecycline (14.1%) and imipenem regimens (12.2%), although more deaths occurred in VAP patients treated with tigecycline than imipenem. Overall, the tigecycline regimen was noninferior to the imipenem/cilastatin regimen for the c-mITT but not the CE population; this difference appears to have been driven by results in VAP patients.

Use of a clinically derived exposure-response relationship to evaluate potential tigecycline-Enterobacteriaceae susceptibility breakpoints

Potential tigecycline-Enterobacteriaceae susceptibility breakpoints were evaluated using 2 approaches, which differed in the nature of the probabilities assessed by MIC value. Using a previously derived tigecycline population pharmacokinetic model and Monte Carlo simulation, a probability density function of steady-state area under the concentration-time curve for 24 h (AUC(SS(0-24))) values for 9999 patients was generated. AUC(SS(0-24)) values were divided by clinically relevant fixed MIC values to derive AUC(SS(0-24))/MIC ratios, which were used to calculate the clinical response expectation by MIC value based upon a logistic regression model for efficacy (1st approach). For the 2nd approach, the probability of pharmacokinetic-pharmacodynamic (PK-PD) target attainment was calculated as the proportion of patients with AUC(SS(0-24))/MIC ratios greater than the threshold value of 6.96, the PK-PD target associated with optimal clinical response. Probabilities of clinical response and PK-PD target attainment were poorly correlated at MIC values >0.25 mg/L. For instance, the median probability of clinical success was 0.76, whereas the probability of PK-PD target attainment was 0.27 at an MIC value of 1 mg/L, suggesting that the probability of PK-PD target attainment metrics underestimates the clinical performance of tigecycline at higher MIC values.

Optimising piperacillin/tazobactam dosing in paediatrics

Piperacillin/tazobactam, an intravenous antibacterial combination product, has recently been approved for paediatric (age 2 months to 17 years) use in the USA. The purpose of this analysis is to describe the basis for the dosing recommendations in this age group. Pharmacokinetic (PK) parameters and demographic covariates from 53 children enrolled in two paediatric studies were used in the analysis. Individual drug clearance (CL) values calculated by non-compartmental methods were available. The influence of demographic covariates on CL was investigated by non-linear regression. The analysis identified CL to be dependent on body weight. CL was also found to be influenced by age in paediatric patients<or=2 years, which is consistent with the expectation based on maturation of renal function. The population PK analysis and simulations, utilising comparable adult exposures as a basis to explore optimal dosing, resulted in the following dosing recommendations: for paediatric patients>or=9 months, a dose of 100/12.5 mg/kg every 8h showed exposures similar to adults; for paediatric patients aged 2-9 months, the dose of 100/12.5 mg/kg should be reduced by a factor of 0.8 (i.e. 80/10 mg/kg), likely due to immature renal function. Based upon this analysis, dosing recommendations for paediatric patients down to 2 months of age were incorporated in the labelling. No data were available to allow additional recommendations for paediatric patients<2 months of age to be made.

Serum, tissue and body fluid concentrations of tigecycline after a single 100 mg dose

OBJECTIVES

The purpose of this study was to determine the tissue and corresponding serum concentration of tigecycline at selected time points in gall bladder, bile, colon, bone, synovial fluid (SF), lung and CSF in subjects undergoing surgical or medical procedures.

METHODS

One hundred and four adult subjects (aged 24-83 years; 64 women, 40 men) received a single intravenous (i.v.) dose of tigecycline (100 mg infused over 30 min). Subjects were randomly assigned to one of four collection times at 4, 8, 12 and 24 h after the start of the infusion. For CSF, samples were collected at approximately 1.5 and 24 h after the start of the infusion. All subjects had serum samples collected before the administration of tigecycline, at the end of the infusion and at the time corresponding to tissue or body fluid collection. Drug concentrations in serum, tissues and body fluids were determined by LC/MS/MS. The area under the mean concentration-time curve from 0 to 24 h (AUC(0-24)) was determined for the comparison of systemic exposure between tissue or body fluid to serum.

RESULTS

The mean serum concentrations of tigecycline were similar to those previously published. Tissue penetration, expressed as the ratio of AUC(0-24) in tissue or body fluid to serum, was 537 for bile, 23 for gall bladder, 2.6 for colon, 2.0 for lung, 0.41 for bone, 0.31 for SF and 0.11 for CSF.

CONCLUSIONS

A single 100 mg dose of intravenous tigecycline produced considerably higher tissue/fluid concentrations in bile, gall bladder, colon and lung compared with simultaneous serum concentrations. On average, the systemic exposure of tigecycline in bone, SF and CSF ranged from 11% to 41% of serum concentrations. The results in bone are inconsistent with previous radiolabelled studies in animals and it is unclear if tight binding to bone (versus low bone uptake) or poor extraction of tigecycline for LC/MS/MS detection or both may have contributed to the differences we observed in humans.

The comparability of etanercept pharmacokinetics in healthy Japanese and American subjects

Thirty Japanese (J) and 32 American (A) healthy subjects received single doses of etanercept by subcutaneous injection, in 3 separate trials. Serum samples were collected for 480 hours after dosing. Concentrations were determined using enzyme-linked immunosorbent assay methods. Pharmacokinetic parameters were calculated using both non-compartmental and compartmental methods. Etanercept was slowly absorbed, with mean+/-SD time to maximum serum concentration of 47+/-15 hours (J), and 51+/-20 hours (A). The maximum serum concentration and area under the concentration time curve increased for doses 10 mg, 25 mg, and 50 mg, in a linear relationship. Etanercept was slowly eliminated, with observed mean+/-SD half-life of 80+/-25 hours (J) and 75+/-15 hours (A) and mean+/-SD apparent clearance of 144+/-65 mL/h (J) and 132+/-74 mL/h (A). Very low concentrations of etanercept were observed in the urine samples collected in the Japanese subjects. All adverse reactions observed resolved without issue, and none required discontinuation from the study.

Population pharmacokinetics of tigecycline in patients with complicated intra-abdominal or skin and skin structure infections

Tigecycline, a first-in-class expanded glycylcycline antimicrobial agent, has demonstrated efficacy in the treatment of complicated skin and skin structure infections (cSSSI) and complicated intra-abdominal (cIAI) infections. A population pharmacokinetic (PK) model for tigecycline was developed for patients with cSSSI or cIAI enrolled in two phase 2 clinical trials, and the influence of selected demographic factors and clinical laboratory measures was investigated. Tigecycline was administered as an intravenous loading dose followed by a 0.5- or 1-h infusion every 12 h for up to 14 days. Blood samples were collected the day before or the day of hospital discharge for the determination of serum tigecycline concentrations. Patient covariates were evaluated using stepwise forward (alpha = 0.05) and backward (alpha = 0.001) procedures. The predictive performance of the model was assessed separately using pooled data from either two phase 3 studies for patients with cSSSI or two phase 3 studies for patients with cIAI. A two-compartment model with zero-order input and first-order elimination adequately described the steady-state tigecycline concentration-time data. Tigecycline clearance was shown to increase with increasing weight, increasing creatinine clearance, and male gender (P < 0.001). The final model provided a relatively unbiased fit to each data set. Individual predicted values of the area under the concentration-time curve from 0 to 12 h (AUC(0-12)) were generally unbiased (median prediction error, -1.60% to -3.78%) and were similarly precise (median absolute prediction error, <4%) when compared across data sets. The population PK model provided the basis to obtain individual estimates of steady-state AUC(0-12) in later exposure-response analyses of tigecycline safety and efficacy in patients with cSSSI or cIAI.

Interrupted time series analysis in clinical research

OBJECTIVE

To demonstrate the usefulness of interrupted time series analysis in clinical trial design.

METHODS

A safety data set of electrocardiographic (ECG) information was simulated from actual data that had been collected in a Phase I study. Simulated data on 18 healthy volunteers based on a study performed in a contract research facility were collected based on single doses of an experimental medication that may affect ECG parameters. Serial ECGs were collected before and during treatment with the experimental medication. Data from 7 real subjects receiving placebo were used to simulate the pretreatment phase of time series; data from 18 real subjects receiving active treatment were used to simulate the treatment phase of the time series. Visual inspection of data was performed, followed by tests for trend, seasonality, and autocorrelation by use of SAS.

RESULTS

There was no evidence of trend, seasonality, or autocorrelation. In 11 of 18 simulated individuals, statistically significant changes in QTc intervals were observed following treatment with the experimental medication. A significant time of day and treatment interaction was observed in 4 simulated patients.

CONCLUSIONS

Interrupted time series analysis techniques offer an additional tool for the study of clinical situations in which patients must act as their own controls and where serial data can be collected at evenly distributed intervals.

Licensure of gemtuzumab ozogamicin for the treatment of selected patients 60 years of age or older with acute myeloid leukemia in first relapse

This paper discusses background information and the body of clinical data that has been accumulated to demonstrate the efficacy and safety of gemtuzumab ozogamicin (Mylotarg, Wyeth Pharmaceuticals, Philadelphia, PA). Based on these data, gemtuzumab ozogamicin was approved by the United States Food and Drug Administration for the treatment of patients with CD33-positive acute myeloid leukemia in first relapse who are 60 years of age or older and who are not considered candidates for other cytotoxic chemotherapy. The recommended dosage of gemtuzumab ozogamicin is 9 mg/m2, administered as a 2-hour intravenous infusion for a total of 2 doses with 14 days between doses.

Impact of age and gender on the pharmacokinetics of gemtuzumab ozogamicin

STUDY OBJECTIVE

To determine the pharmacokinetic parameters of the components of gemtuzumab ozogamicin and to assess the possible influence of age and gender on the values.

DESIGN

Phase II, multicenter, open-label, nonrandomized, parallel study

SETTING

Hospitals and outpatient oncology clinics.

PATIENTS

Fifty-eight patients with acute myeloid leukemia in first relapse participated. Demographic data included 29 men and 29 women; 34 were younger than 60 years of age (mean age 53+/-16 yrs).

INTERVENTION

Patients received gemtuzumab ozogamicin as a single 2-hour infusion of 9 mg/m2. Serial plasma samples were collected over 10 days after the beginning of the infusion.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of components of gemtuzumab ozogamicin (hP67.6 antibody, total and unconjugated calicheamicin derivatives) were measured by validated enzyme-linked immunosorbent assays. Pharmacokinetic parameters were determined by noncompartmental methods and comparisons between groups were made by analysis of variance. No significant differences were seen between men and women or between those over 60 and those less than 60 years of age in maximum concentration, time to maximum concentration, area under the curve, clearance, or volume of distribution for components of gemtuzumab ozogamicin.

CONCLUSION

No differences occur in the pharmacokinetics of the components of gemtuzumab ozogamicin (hP67.6 or calicheamicin) based on gender or age.

Chiral bioequivalence: effect of absorption rate on racemic etodolac

BACKGROUND

For many racemic drugs, bioequivalence assessment based on isomer-nonspecific assays is appropriate because enantiomeric area under the concentration-time curve (AUC) exposure ratios are close to unity. Use of nonspecific methods in cases in which the ratio is substantially greater or less than 1, however, may obscure real therapeutic differences among formulations, especially if the enantiomers exhibit differing pharmacological potencies.

OBJECTIVE

To examine the influence of absorption rate on etodolac bioequivalence as measured by total [(R,S)-] and (S)-etodolac.

DESIGN

Single dose, 3-period, crossover, pharmacokinetic study in 24 healthy volunteers in which the administration rate of etodolac was varied.

METHODS

Participants received etodolac 400mg in solution, given as a single dose over 1 minute or as divided doses over 30 and 90 minutes. Unresolved and enantiomer concentrations of etodolac were measured by a validated HPLC assay. The enantiomer ratio was similarly measured by HPLC.

RESULTS

Bioequivalence parameters derived for both unresolved and (S)etodolac indicate that peak plasma drug concentration (Cmax) was not bioequivalent. By delaying absorption, bioequivalence was lost.

CONCLUSIONS

Collectively, these data demonstrate that bioequivalence between 2 products of etodolac based on enantiomerically nonspecific criteria alone may not generalise to the pharmacologically relevant (S)-enantiomer. This suggests that enantiospecific assays are necessary for bioequivalence assessments.

The pharmacokinetics of etanercept in healthy volunteers

OBJECTIVE

To describe the pharmacokinetics of etanercept when administered by subcutaneous injection in single doses to healthy volunteers.

METHODS

Twenty-six healthy volunteers between 19 and 50 years of age received single doses of etanercept 25 mg by subcutaneous injection into the abdomen. Serial serum samples were collected for 21 days. An enzyme-linked immunosorbent assay with a quantitation limit of 0.3 ng/mL was used to measure the drug concentrations.

RESULTS

Etanercept was well tolerated by healthy volunteers. A one-compartment model was found to best describe the concentration-time data and was used to determine the pharmacokinetic parameters. Etanercept is slowly absorbed from the site of injection with a time of peak concentration (+/- SD) of 51 +/- 14 hours; peak concentration was 1.46 +/- 0.72 mg/L. The AUC was 235 +/-98 mg x h/L, apparent clearance was 132 +/- 85 mL/h, apparent volume of distribution was 12 +/- 6 L, and the half-life was 68 +/- 19 hours.

CONCLUSIONS

Etanercept was slowly absorbed and slowly eliminated after subcutaneous administration. Dosing at the recommended rate of 25 mg twice weekly would be expected to result in concentrations of approximately 3 mg/L. Intersubject variability for apparent clearance in healthy volunteers was 64%.

Pharmacokinetics of etodolac in patients with stable juvenile rheumatoid arthritis

This was a single-center, open-label, single-dose pharmacokinetic study of etodolac in pediatric and adolescent patients with stable juvenile rheumatoid arthritis (JRA). Eleven male and female patients with JRA (8.1 to 14.8 years of age, weighing 26.4 to 59.5 kg) received a single oral dose of etodolac (200, 300, or 400 mg based on body weight). Clinical laboratory measurements, measurement of vital signs, and physical examinations were performed to monitor safety. Concentrations of etodolac were determined in plasma using high-performance liquid chromatography with ultraviolet detection with a limit of quantitation of 0.2 mg/L and were analyzed using a noncompartmental pharmacokinetic method. Pharmacokinetic parameters observed were consistent in magnitude and degree of variability with data from healthy adult subjects receiving a single 400- or 600-mg dose of etodolac. Although the mean fraction of unbound drug in patients with JRA was higher than in healthy adults, the oral clearance was independent of age. No serious adverse events occurred during this study. Etodolac yielded consistent pharmacokinetic values among stratified dose subgroups. Single doses of all etodolac treatments were well tolerated in both pediatric and adolescent patients.

The influence of bromfenac on the pharmacokinetics and pharmacodynamic responses to glyburide in diabetic subjects

STUDY OBJECTIVE

To assess the effect of bromfenac sodium, a nonnarcotic analgesic drug under development, on the pharmacokinetics and pharmacodynamics of glyburide in patients with type II diabetes.

DESIGN

Randomized, double-blind, placebo-controlled, multiple-dose study with a two-period crossover design.

PATIENTS

Eleven men and one woman (age 36-64 yrs) whose diabetes was responsive to oral sulfonylurea therapy.

INTERVENTIONS

Placebo or bromfenac 50 mg was given as a single oral dose 3 times/day for the first 3 days of the study. On days 4-6, patients received the alternative treatment. For at least 3 months before and during the study, patients took their usual single daily dose of glyburide 10 mg.

MEASUREMENTS AND MAIN RESULTS

Bromfenac concentrations were measured by high-performance liquid chromatography with ultraviolet detection. Glyburide concentrations were measured by gas chromatography with nitrogen-phosphorus detection. Glycemia was measured repeatedly on day 3 of each treatment. Pharmacokinetic analysis was performed with noncompartmental techniques. No significant differences in the pharmacokinetics of glyburide or in the pharmacodynamic response of serum glucose levels were observed between placebo and bromfenac. Intersubject variability of concentrations was modest for glyburide and glucose, with a CV of 43% or less.

CONCLUSION

Glyburide levels are not changed during concomitant administration of bromfenac.

Absolute bioavailability of bromfenac in humans

OBJECTIVE

To estimate absolute bioavailability of bromfenac and to compare its pharmacokinetics after intravenous and oral administration.

DESIGN

This was a randomized, open-label, single-dose, crossover study conducted under fasting conditions with a washout period of at least 48 hours between doses. Each subject received a 50-mg dose of bromfenac both intravenously and orally followed by collection of blood samples at specified time intervals. Bromfenac plasma concentrations were measured by using a validated HPLC method with ultraviolet detection.

SETTING

The study was conducted at the Drug Evaluation Unit. Hennepin County Medical Center, Minneapolis, MN.

SUBJECTS

The participants consisted of 12 healthy subjects between 18 and 45 years of age and within +/-15% of ideal body weight.

RESULTS

The mean +/- SD absolute bioavailability of bromfenac was 67% +/- 20%.

CONCLUSIONS

The pharmacokinetic parameters of bromfenac were similar after intravenous and oral administration, suggesting that the prototype oral dosage form is optimal and that the observed intersubject variability is due to bromfenac itself, not the type of dosage form.

Effects of age and gender on the pharmacokinetics of bromfenac in healthy volunteers

OBJECTIVE

To compare the pharmacokinetic parameters of bromfenac, a nonsteroidal antiinflammatory drug under development, in healthy volunteers of various ages and either gender, after single and multiple doses.

DESIGN

Open-label, single- and multiple-dose, nonrandomized, parallel study.

PARTICIPANTS

Twenty young (18-45 y), 12 young-elderly (65-74 y), and 12 elderly (75-85 y) subjects were studied. Half of the subjects in each group were women.

INTERVENTIONS

Bromfenac was given as a single 50-mg dose and then as 50-mg doses every 12 hours for 3 additional days. Twelve blood samples were collected for 12 hours after the first and last doses.

MAIN OUTCOME MEASURES

Bromfenac concentrations were measured by using an HPLC procedure with ultraviolet detection. Unbound bromfenac concentrations were measured by equilibrium dialysis. Pharmacokinetic analysis was performed by noncompartmental techniques.

RESULTS

No significant differences related to gender were detected. Significant differences were observed in half-life (t1/2), AUC, clearance, and apparent volume of distribution when the elderly group was compared with the young group and in t1/2 when the elderly group was compared with the young-elderly group, although substantial overlap among groups was observed.

CONCLUSIONS

Administration of bromfenac to young-elderly or elderly subjects of either gender does not require a dosage adjustment in acute settings. Consideration should be made to titrating dosages in patients over 75 years of age who require repeated doses.