Integrated pharmacokinetic, pharmacodynamic and immunogenicity profiling of an anti-CCL21 monoclonal antibody in cynomolgus monkeys.

QBP359 is an IgG1 human monoclonal antibody that binds with high affinity to human CCL21, a chemokine hypothesized to play a role in inflammatory disease conditions through activation of resident CCR7-expressing fibroblasts/myofibroblasts. The pharmacokinetics (PK) and pharmacodynamics (PD) of QBP359 in non-human primates were characterized through an integrated approach, combining PK, PD, immunogenicity, immunohistochemistry (IHC) and tissue profiling data from single- and multiple-dose experiments in cynomolgus monkeys. When compared with regular immunoglobulin typical kinetics, faster drug clearance was observed in serum following intravenous administration of 10 mg/kg and 50 mg/kg of QBP359. We have shown by means of PK/PD modeling that clearance of mAb-ligand complex is the most likely explanation for the rapid clearance of QBP359 in cynomolgus monkey. IHC and liquid chromatography mass spectrometry data suggested a high turnover and synthesis rate of CCL21 in tissues. Although lymphoid tissue was expected to accumulate drug due to the high levels of CCL21 present, bioavailability following subcutaneous administration in monkeys was 52%. In human disease states, where CCL21 expression is believed to be expressed at 10-fold higher concentrations compared with cynomolgus monkeys, the PK/PD model of QBP359 and its binding to CCL21 suggested that very large doses requiring frequent administration of mAb would be required to maintain suppression of CCL21 in the clinical setting. This highlights the difficulty in targeting soluble proteins with high synthesis rates.

Pharmacokinetics, pharmacodynamics and safety of QGE031 (ligelizumab), a novel high-affinity anti-IgE antibody, in atopic subjects.

BACKGROUND: Using a monoclonal antibody with greater affinity for IgE than omalizumab, we examined whether more complete suppression of IgE provided greater pharmacodynamic effects, including suppression of skin prick responses to allergen. OBJECTIVE: To explore the pharmacokinetics, pharmacodynamics and safety of QGE031 (ligelizumab), a novel high-affinity humanized monoclonal IgG1κ anti-IgE. METHODS: Preclinical assessments and two randomized, placebo-controlled, double-blind clinical trials were conducted in atopic subjects. The first trial administered single doses of QGE031 (0.1-10 mg/kg) or placebo intravenously, while the second trial administered two to four doses of QGE031 (0.2- 4 mg/kg) or placebo subcutaneously at 2-week intervals. Both trials included an open-label omalizumab arm. RESULTS: Sixty of 73 (82%) and 96 of 110 (87%) subjects completed the intravenous and subcutaneous studies, respectively. Exposure to QGE031 and its half-life depended on the QGE031 dose and serum IgE level. QGE031 had a biexponential pharmacokinetic profile after intravenous administration and a terminal half-life of approximately 20 days. QGE031 demonstrated dose- and time-dependent suppression of free IgE, basophil FcεRI and basophil surface IgE superior in extent (free IgE and surface IgE) and duration to omalizumab. At Day 85, 6 weeks after the last dose, skin prick wheal responses to allergen were suppressed by > 95% and 41% in subjects treated subcutaneously with QGE031 (2 mg/kg) or omalizumab, respectively (P < 0.001). Urticaria was observed in QGE031- and placebo-treated subjects and was accompanied by systemic symptoms in one subject treated with 10 mg/kg intravenous QGE031. There were no serious adverse events. CONCLUSION AND CLINICAL RELEVANCE: These first clinical data for QGE031, a high-affinity IgG1κ anti-IgE, demonstrate that increased suppression of free IgE compared with omalizumab translated to superior pharmacodynamic effects in atopic subjects, including those with high IgE levels. QGE031 may therefore benefit patients unable to receive, or suboptimally treated with, omalizumab.

Pharmacokinetic/pharmacodynamic relationships of FTY720 in kidney transplant recipients.

FTY720 is a new and effective immunosuppressive agent, which produces peripheral blood lymphopenia through a lymphocyte homing effect. We investigated the relationship between the dose of FTY720 or blood concentration (pharmacokinetics, PK) and peripheral lymphopenia (pharmacodynamics, PD) in 23 kidney transplant recipients randomized to receive FTY720 (0.25-2.5 mg/day) or mofetil mycophenolate (2 mg/day) in combination with cyclosporine and steroids. FTY720 dose, blood concentrations and lymphocyte counts were determined weekly before and 4 to 12 weeks after transplantation. The effect of PD was calculated as the absolute lymphocyte count or its reductions. PK/PD modeling was used to find the best-fit model. Mean FTY720 concentrations were 0.36 +/- 0.05 (0.25 mg), 0.73 +/- 0.12 (0.5 mg), 3.26 +/- 0.51 (1 mg), and 7.15 +/- 1.41 ng/ml (2.5 mg) between 4 and 12 weeks after transplantation. FTY720 PK was linear with dose (r(2) = 0.98) and showed low inter- and intra-individual variability. FTY720 produced a dose-dependent increase in mean percent reduction of peripheral lymphocyte counts (38 vs 42 vs 56 vs 77, P < 0.01, respectively). The simple Emax model [E = (Emax * C)/(C + EC50)] was the best-fit PK/PD modeling for FTY720 dose (Emax = 87.8 +/- 5.3% and ED50 = 0.48 +/- 0.08 mg, r(2) = 0.94) or concentration (Emax = 78.3 +/- 2.9% and EC50 = 0.59 +/- 0.09 ng/ml, r(2) = 0.89) vs effect (% reduction in peripheral lymphocytes). FTY720 PK/PD is dose dependent and follows an Emax model (EC50 = 0.5 mg or 0.6 ng/ml). Using lymphopenia as an FTY720 PD surrogate marker, high % reductions (~80%) in peripheral lymphocytes are required to achieve best efficacy to prevent acute allograft rejection.

Pharmacokinetic/pharmacodynamic relationships of FTY720 in kidney transplant recipients

FTY720 is a new and effective immunosuppressive agent, which produces peripheral blood lymphopenia through a lymphocyte homing effect. We investigated the relationship between the dose of FTY720 or blood concentration (pharmacokinetics, PK) and peripheral lymphopenia (pharmacodynamics, PD) in 23 kidney transplant recipients randomized to receive FTY720 (0.25-2.5 mg/day) or mofetil mycophenolate (2 mg/day) in combination with cyclosporine and steroids. FTY720 dose, blood concentrations and lymphocyte counts were determined weekly before and 4 to 12 weeks after transplantation. The effect of PD was calculated as the absolute lymphocyte count or its reductions. PK/PD modeling was used to find the best-fit model. Mean FTY720 concentrations were 0.36 ± 0.05 (0.25 mg), 0.73 ± 0.12 (0.5 mg), 3.26 ± 0.51 (1 mg), and 7.15 ± 1.41 ng/ml (2.5 mg) between 4 and 12 weeks after transplantation. FTY720 PK was linear with dose (r² = 0.98) and showed low inter- and intra-individual variability. FTY720 produced a dose-dependent increase in mean percent reduction of peripheral lymphocyte counts (38 vs 42 vs 56 vs 77, P < 0.01, respectively). The simple Emax model [E = (Emax * C)/(C + EC50)] was the best-fit PK/PD modeling for FTY720 dose (Emax = 87.8 ± 5.3 percent and ED50 = 0.48 ± 0.08 mg, r² = 0.94) or concentration (Emax = 78.3 ± 2.9 percent and EC50 = 0.59 ± 0.09 ng/ml, r² = 0.89) vs effect ( percent reduction in peripheral lymphocytes). FTY720 PK/PD is dose dependent and follows an Emax model (EC50 = 0.5 mg or 0.6 ng/ml). Using lymphopenia as an FTY720 PD surrogate marker, high percent reductions ( about 80 percent) in peripheral lymphocytes are required to achieve best efficacy to prevent acute allograft rejection.

Comparative bioequivalence studies with Estradot and Menorest transdermal systems.

OBJECTIVES: To compare the relative bioavailability of Estradot, a small size, new generation estradiol transdermal system (ETS) to Menorest, in healthy postmenopausal women. METHODS: In two open-label, single center, randomized, crossover, bioequivalence studies, healthy postmenopausal women aged 40-65 years received treatment with all the test regimens. In Study 1 (single-dose study), patients wore 5 cm(2) (50 microg/day), 10 cm(2) (100 microg/day) Estradot and 29 cm(2) (100 microg/day) Menorest for 84 h. In Study 2 (multiple-dose study), patients wore a regimen of four consecutive treatments with a 5 cm(2) (50 microg/day) new generation patch, Estradot and a 14.5 cm(2) (50 microg/day) patch, Menorest. Blood samples were drawn at various time-points in both studies. Estradiol and estrone serum levels were determined by gas chromatography/mass spectrometry or radioimmunoassay methods. Skin irritation (erythema and edema), patch adherence and local skin reaction were assessed following patch removal. RESULTS: In Study 1, baseline-uncorrected C(max) for estradiol for Estradot 50 and 100 microg/day and Menorest 100 microg/day was 54.8, 106.2 and 101.6 pg/ml, respectively, and C(max) for estrone was 75.6, 97.0 and 98.3 pg/ml, respectively. In Study 2, the baseline-uncorrected mean maximum serum concentration (C(max)) for estradiol for Estradot 50 microg/day and Menorest 50 microg/day patches was 56.7 and 52.7 pg/ml, respectively, and C(max) for estrone was 41.7 and 41.3 pg/ml, respectively. No significant skin irritation was observed in either study, but Estradot caused less skin irritation than Menorest. CONCLUSIONS: Estradot produced comparable serum concentrations of estradiol and estrone and caused less skin irritation than Menorest.

Divergent effects of raloxifene HCI on the pharmacokinetics and pharmacodynamics of warfarin.

PURPOSE: Evista (raloxifene HCl) is a nonsteroidal selective estrogen receptor modulator that displays estrogen agonist effects on bone and lipid metabolism but estrogen antagonist effects on the breast and endometrium. The potential for drug-drug interaction between raloxifene and warfarin was assessed in 15 healthy postmenopausal women. METHODS: Single doses of warfarin (20 mg) were administered prior to and during 2 weeks of dosing with raloxifene 120 mg/day. Each warfarin dose was followed by pharmacokinetic sampling and prothrombin time measurements. RESULTS: Raloxifene administration resulted in 7.1% and 14.1% decreases in the clearance (CLp/F) and 7.4% and 9.8% decreases in the volume of distribution (Vss/F) of R- and S-warfarin, respectively (all p < or = 0.05). In contrast to the slightly higher plasma concentrations of R- and S-warfarin, raloxifene reduced the maximum prothrombin time (PTmax) by 10% and the area under the PT versus time curve from 0-120 h (AUCPT) by 8% (p < 0.01). CONCLUSIONS: Raloxifene administration may result in a small increase in systemic warfarin exposure that is associated with a diminution, not augmentation, of the pharmacodynamic effect. Due to the small magnitude of this effect, concomitant administration of raloxifene and warfarin is not likely to result in clinically significant drug-drug interaction.

Correlation of in vitro and in vivo paracetamol availability from layered excipient suppositories.

An in vivo investigation of paracetamol availability was carried out on eight healthy volunteers, comparing two paracetamol suppository formulations prepared using two different gliceride bases, a fast drug-releasing one and a slow drug-releasing one, i.e. Witepsol H15 and W35, respectively. The formulations were selected on the basis of a previous in vitro drug release study, which showed that, by superimposing the excipients in two layers within the same suppository, the drug release kinetics could be modulated using different ratios between the two layers. The comparison between the two different formulations in terms of plasma profiles and total amounts of drug excreted in urine revealed an increase in the extent of drug absorption from the layered excipient suppository. As the W35 has a higher monoglyceride content than the H15, this improved paracetamol availability could be ascribed to the absorption-enhancing effect of the monoglycerides. Moreover, the W35 has also a higher viscosity, which could possibly cause the suppository to be retained for a longer time in the lower part of the rectum, where the blood is drained directly to the systemic circulation. It was therefore hypothesized that the enhanced paracetamol availability could be also due to a liver bypass mechanism. For a further examination of the paracetamol absorption kinetics after rectal administration, a one-compartment model was fitted to the drug plasma concentration data. This approach allowed to draw absorption versus time profiles, which showed that a retardation actually occurred in paracetamol absorption when using suppositories containing the slow drug releasing excipient W35. These absorption data were then employed for an A level in vitro-in vivo correlation testing, and a linear relationship was found between in vitro release rate and in vivo absorption rate, both for fast releasing and for the layered excipient suppositories.

Mechanisms of nonlinear pharmacokinetics of mibefradil in chronically instrumented dogs.

The mechanisms of nonlinear pharmacokinetics after single- and multiple-dose treatments with a new calcium channel blocker, mibefradil, were studied. Four female, chronically instrumented dogs (22 +/- 2.1 kg) received a single i.v. dose (1 mg/kg), three single p.o. doses (1, 3 and 6 mg/kg) and a regimen of 3 mg/kg p.o. doses twice per day for 8 days; the order of treatment was randomized. Data on i.v. administration showed that hepatic clearance and systemic clearance values were similar (20.1 +/- 5.5 vs. 18.5 +/- 4.4 ml/min/kg, P > .05), suggesting that the liver is the main eliminating organ. The fraction of the administered dose absorbed from the gut after all p.o. treatments was approximately 60%, indicating that incomplete absorption and/or first-pass gut metabolism occurred. The fraction absorbed was not altered by dose or duration of treatment. The absolute bioavailability, however, was increased because of a dose- and duration of treatment-dependent reduction in hepatic elimination (absolute bioavailability changing from 0.25 +/- 0.18 at 1 mg/kg to 0.40 +/- 0.22 at 6 mg/kg and 0.48 +/- 0.14 after multiple dosing, P < .05). This change was mainly caused by a decrease of systemic clearance values from 15.6 +/- 9.7 to 9.0 +/- 1.3 and 7.0 +/- 3.5 ml/min/kg, respectively (P < .05). These data clearly indicate that the nonlinear pharmacokinetics of mibefradil after p.o. dosing are the result of an increase in bioavailability and a reduction in systemic clearance. Both changes are attributed to a reduction in the ability of the liver to eliminate the drug.

Nonlinear pharmacokinetics of mibefradil in the dog.

The pharmacokinetics of mibefradil in the dog was evaluated in this study. Single intravenous (1 mg/kg) and three oral doses (1, 3, 6 mg/kg) of mibefradil were administered to three dogs according to a randomized complete block design, where dogs were blocks and treatments randomly assigned to each block. Systemic plasma clearance, volume of distribution at steady-state and half-life after intravenous administration were as follows: ClS = 18.4 +/- 1.2 mL/min/kg, VSS = 9.7 +/- 3.8 L/kg, and T1/2 = 9.5 +/- 3.4 h. Oral plasma clearance decreased with an increase in dose, from 101.8 +/- 18.8 mL/min/kg at 1 mg/kg to 21.7 +/- 4.3 mL/min/kg at a 6 mg/kg dose (p < 0.05). Half-life values did not change significantly with an increase in oral dose in all the animals studied (10.6 +/- 1.5 h at 1 mg/kg to vs 13.4 +/- 3.5 h at 6 mg/kg). Dose-normalized AUC ratios between the oral and intravenous treatments increased from 0.18 +/- 0.03 at 1 mg/kg to 0.87 +/- 0.21 at a 6 mg/kg dose (p < 0.05). The nonlinear kinetic behavior of mibefradil is consistent with an increase in gut absorption and/or reduction in elimination after higher oral doses. Although both dogs and humans exhibit nonlinear pharmacokinetics after oral administration, there are substantial differences in the clearance and volume of distribution values between these two species. Even though these differences can, in part, be accounted for by the difference in plasma protein binding, the use of the dog as an animal model for human mibefradil pharmacokinetics need to be qualified.

High-performance liquid chromatographic analysis of mibefradil in dog plasma and urine.

The objective of the study was to develop a sensitive and specific assay for studying the pharmacokinetics of a novel calcium antagonist, a benzimidazolyl-substituted tetraline derivative, mibefradil (I) in the dog. The assay involves liquid-liquid extraction of a biological sample, reversed-phase HPLC separation and fluorescence detection (lambda ex = 270 nm and lambda em = 300 nm) of sample components. Each sample was eluted with a mobile phase pumping at a flow-rate of 2 ml/min. The mobile phase composition was a mixture of acetonitrile and aqueous solution (38:62, v/v). The aqueous solution contains 0.0393 M KH2PO4 and 0.0082 M Na-pentanesulphonic acid. The retention times were 10.7 min for I, and 12.2 min for internal standard Ro 40-6792. Calibration curves with concentrations of I ranging from 10 to 500 ng/ml were linear (r2 > 0.99). The detection limit for I was 0.5 ng/ml when 0.5 ml of plasma or urine was used. Intra- and inter-day accuracy and precision were within 10%. The assay was successfully applied to the pharmacokinetic studies of I in dogs.

Pharmacokinetics and presystemic gut metabolism of methyldopa in healthy human subjects.

This study examined the pharmacokinetics and metabolism of methyldopa after giving single 250-mg oral and intravenous doses to 16 healthy human volunteers. A 48-hour washout period was allowed between oral and intravenous treatments. Blood and urine samples were collected; methyldopa was assayed in blood and urine, and its metabolites (methyldopa sulfate, alpha-methyldopamine, and alpha-methyldopamine sulfate) were assayed in urine. Pharmacokinetic parameters were recorded as follows: half-life was 2.0 +/- 0.7 hours; total body and renal clearance were 268 +/- 72 and 107 +/- 35 mL/min, respectively; and volume of distribution at steady-state was 33 +/- 11 L. The absolute bioavailability of the drug was 42 +/- 16%. The measurable metabolites in urine after oral and intravenous administration accounted for 27% and 17% of the dose, respectively. Methyldopa sulfate was the most abundant metabolite recorded; its quantity was higher after oral than after intravenous administration, 20.1 +/- 5.7% versus 6.7 +/- 5.3% of the dose (P < .05), suggesting significant presystemic gut metabolism. First-pass gut metabolism for methyldopa was estimated to be 17.6 +/- 6.9% of the dose given.

Methyldopa kinetics before and after ingestion of methyldopa for eight weeks.

Methyldopa urine and plasma levels and urine metabolite levels were assessed following intravenous (IV) and oral (PO) methyldopa before, and after ingestion of methyldopa (500 mg) daily for eight weeks. There was no increase in (estimated) methyldopa absorption (8.4%) or renal clearance (PO 13.9%, IV 2.33%) after the eight weeks of methyldopa ingestion. However, the initial methyldopa absorption and renal clearance values in this study were higher than that in previous studies. There was an inverse relation between the initial methyldopa absorption and the change in absorption (r - 0.605) and between the initial methyldopa renal clearance and the change in renal clearance (PO r -0.874, IV r -0.891). Overall, this study did not confirm our previous studies showing induction of methyldopa absorption and renal clearance, possibly due to prior up regulation of transporter function. Consistent with methyldopa inducing drug transporters, those with low initial absorption and renal clearance values had the greatest increases.

Hepatic blood flow measurements and indocyanine green kinetics in a chronic dog model.

The objective of this study was to compare hepatic blood flow measurements using ultrasonic flow probes and ICG in a conscious dog model and to evaluate whether ICG can be used to estimate relative change in hepatic blood flow. Seven mongrel dogs (3 M, 4 F, BW = 21 +/- 1.8 kg, Hct = 0.39 +/- 0.05) were used in the study. Catheters were surgically inserted into carotid artery and portal, hepatic and jugular vein. Transit-time ultrasonic flow probes were implanted around the portal vein and hepatic artery. After two weeks of recovery, a single i.v. bolus dose of ICG (0.5 mg/kg) was administered to each dog. The disposition profiles for ICG in the four catheters were measured for 15 minutes and the hepatic blood flow reading from the probes recorded. Jugular vein ICG blood clearance (Cl = 5.9 +/- 1.1 ml/min/kg) was low compared to the electronically measured hepatic blood flow rate (Q = 27.8 +/- 9.1 ml/min/kg). Extraction ratios (E = 0.15 +/- 0.05) estimated using data from the inlet and the outlet of the liver were consistent with the clearance values, suggesting that ICG is not highly extracted by dog livers. Three dogs were used in experiments where liver blood flow was increased by food intake. Consistent with characteristics of low extraction ratio drugs, ICG was insensitive to blood flow changes while there was an overall increase in electronically measured liver blood flow of 30%.(ABSTRACT TRUNCATED AT 250 WORDS)