Evaluation of the Pharmacokinetics of Single- and Multiple-dose Buprenorphine Buccal Film in Healthy Volunteers.

PURPOSE: Buprenorphine, a partial µ-receptor agonist, is approved for the management of moderate to severe pain, but it has low oral bioavailability. Two open-label studies were performed to determine the pharmacokinetic profile of buprenorphine from buccal film formulations of buprenorphine. METHODS: Both studies enrolled healthy volunteers, aged 18 to 55 years, who received concurrent oral naltrexone to reduce adverse events (AEs); subjects with a history or evidence of substance abuse or current use of any product affecting cytochrome P450 3A4 activity were excluded. The first study (n = 25) was a 5-period crossover trial with 4 single doses (75 and 300 and 300 and 1200 µg) of 2 formulations (F14 and F24) of buccal buprenorphine (BBUP) and a 300-µg intravenous dose of buprenorphine with a 7-day washout between periods. In the second study, each subject (n = 10) received 6 doses of 4 BBUP strengths (60, 120, 180, and 240 µg BID) in a dose-escalation design. Plasma concentrations of buprenorphine and norbuprenorphine were assayed, and pharmacokinetics were summarized with descriptive statistics and analyzed by using a linear mixed effects model (single-dose study). AEs were recorded. FINDINGS: In the single-dose study, the 2 formulations exhibited comparable bioavailability of 46% to 51% that was independent of dose, with a single buprenorphine peak concentration from each BBUP dose occurring at 2.5 to 3 hours. The mean buprenorphine Cmax across the doses ranged from 0.17 ng/mL for the 75-µg dose to 1.43 ng/mL for the 1200-µg dose. AUC0-∞, AUC0-last, and Cmax were proportional to the dose of BBUP administered. Cmax of norbuprenorphine after BBUP administration was approximately one tenth that of buprenorphine Cmax. In the multiple-dose study, steady state was reached within 3 days of BID dosing. There was a linear increase in exposure across the dose range from 60 to 240 µg BID. Treatment-emergent AEs in both studies were consistent with those reported with opiate administration to healthy volunteers. IMPLICATIONS: The absolute bioavailability of BBUP was 46% to 51% across a 16-fold dose range, with dose-proportional increases in systemic exposure. Apparent steady-state conditions occurred within 3 days of dosing. These pharmacokinetic results suggest that therapeutic buprenorphine plasma concentrations can be obtained with BBUP across a wide dose range in a shorter time than other (eg, transdermal) dosage forms.

Differentiating the Effect of an Opioid Agonist on Cardiac Repolarization From µ-Receptor-mediated, Indirect Effects on the QT Interval: A Randomized, 3-way Crossover Study in Healthy Subjects.

PURPOSE: A thorough QT study was conducted in healthy subjects to evaluate the effect of buprenorphine hydrochloride administered through a buccal soluble film under coverage of naltrexone to block confounding, secondary QT effects. METHODS: Healthy subjects were enrolled in a randomized, partially blinded, 4-way crossover designed study. Subjects received buprenorphine 3 mg with naltrexone, naltrexone alone (with placebo films), placebo (placebo films and placebo naltrexone), and open-label moxifloxacin 400 mg with placebo naltrexone in separate in-house treatment periods. Naltrexone treatment (50 mg) was initiated 12 hours before buprenorphine and was given every 12 hours for a total of 4 doses. ECG data were extracted from a continuous recording predose and serially after dosing on the treatment day. ECG intervals were measured at a central ECG laboratory by using the high-precision QT technique. The QT interval was corrected for heart rate with Fridericia's formula (QTcF), and change-from-predose baseline QTcF (∆QTcF) was analyzed by using a mixed effect model. FINDINGS: Fifty-eight subjects (35 males) with a mean age of 32 were enrolled into the study. Treatment with buprenorphine 3 mg resulted in a small QT effect with the largest mean naltrexone-corrected ∆QTcF reaching 5.8 msec at 8 hours' postdosing (upper bound of the 90% CI below 10 msec). Exposure response analysis with a linear model demonstrated a significant linear relationship between plasma levels and naltrexone-corrected ∆QTcF, with an estimated mean slope of 0.65 msec per nanogram/milliliter (90% CI, 0.22 to 1.08). Using the exposure response model, an effect on ∆QTcF of 4.5 msec (2.80 to 6.12) can be predicted at the observed geometric peak plasma level after administration of the 3-mg buprenorphine dose in this study (3.6 ng/mL [3.33 to 3.98]). Naltrexone alone did not have a relevant effect on the QTcF interval. IMPLICATIONS: The present study showed that buprenorphine plasma levels up to 5 ng/mL had no effect on the QTc above the level of clinical concern.

A subcutaneous octreotide hydrogel implant for the treatment of acromegaly.

OBJECTIVE: To evaluate the pharmacokinetics, efficacy, and safety of a subcutaneous octreotide hydrogel implant in patients with acromegaly. METHODS: In 2 phase II open-label randomized studies, patients aged ≥ 18 years with confirmed acromegaly and octreotide responsiveness received one or two 52 mg hydrated implants (52 mg study) or a hydrated or nonhydrated 84 mg implant (84 mg study) inserted subcutaneously in the upper arm. Implants were removed after 6 months. The 84 mg study assessed pharmacokinetics in patients with undetectable baseline octreotide concentrations. Both studies assessed efficacy (serum growth hormone [GH], insulin-like growth factor 1 [IGF-1]) and safety (adverse events, physical examination, clinical chemistry). RESULTS: Eleven patients received 1 (n = 5) or 2 (n = 6) 52 mg implants; 34 received a hydrated (n = 17 [safety]; n = 16 [efficacy analysis]) or nonhydrated (n = 17) 84 mg implant. With the nonhydrated versus hydrated 84 mg implant, mean maximum serum concentration (Cmax) and mean area under the drug concentration versus time curve from time 0 to 6 months were decreased (P = 0.002 and P = 0.03, respectively) and mean time to Cmax was increased (P = 0.002). In both studies, IGF-1 and GH declined in month 1 and were significantly suppressed during the 6-month treatment versus baseline (P<0.001). With the 52 mg and 84 mg implants, respectively, 3 of 11 patients (27%) and 17 of 33 patients (52%) achieved IGF-1 normalization and 8 of 11 patients (73%) and 13 of 33 patients (39%) exhibited GH <2.5 ng/mL; 9 of 11 patients (82%) and 11 of 34 patients (32%) experienced treatment-related adverse events, which were mainly gastrointestinal. CONCLUSION: Octreotide hydrogel implants were well tolerated and maintained stable octreotide release and suppression of IGF-1 and GH over 6 months.

Pharmacokinetics and pharmacodynamics of the erythropoietin Mimetibody construct CNTO 528 in healthy subjects.

BACKGROUND AND OBJECTIVE: Anaemia is a serious comorbidity that is common in patients with renal failure or cancer. CNTO 528 is the first Mimetibody developed to mimic the effects of erythropoietin (EPO), a hormone that stimulates the production of red blood cells (RBCs). The objective of this study was to develop a pharmacokinetic and pharmacodynamic model for CNTO 528 in healthy male subjects. METHODS: A pharmacokinetic/pharmacodynamic model for CNTO 528 was developed to describe the serum concentration versus time profile and the pharmacological responses of percentage of reticulocytes, total RBC counts and haemoglobin concentration after a single intravenous administration of CNTO 528 at 0.03, 0.09, 0.3 and 0.9 mg/kg in 24 healthy subjects. An open, linear, two-compartment model was used to characterize the pharmacokinetic parameters of CNTO 528. A catenary cell production and lifespan loss model was used to fit the pharmacodynamic data, yielding estimates of drug potency (SC(50)), efficacy (S(max)) and other pharmacodynamic parameters. Bootstrap and posterior predictive checks (PPC) were used to evaluate the model. RESULTS: Administration of CNTO 528 stimulated the production of reticulocytes, RBCs and haemoglobin. CNTO 528 exhibits a half-life of 141 hours, or approximately 5.9 days. The SC(50) was estimated to be 0.37 mg/L, indicating that low serum CNTO 528 concentration was sufficient to produce pharmacological effects. Compared with historical controls, CNTO 528 S(max) appears to be 2-fold higher than recombinant human EPO. Bootstrap analysis and PPCs confirmed the accuracy and precision in the parameter estimates and the adequacy of the model to describe the CNTO 528 pharmacokinetics and pharmacodynamics. CONCLUSION: The mechanistic population model was suitable to characterize the pharmacokinetics and pharmacodynamics of intravenously administered CNTO 528 in healthy subjects. This qualified model is deemed appropriate to conduct clinical trial simulations and to support the decision-making process for dose selection in studies of EPO-stimulating agents.

A phase I, single and fractionated, ascending-dose study evaluating the safety, pharmacokinetics, pharmacodynamics, and immunogenicity of an erythropoietin mimetic antibody fusion protein (CNTO 528) in healthy male subjects.

The erythropoietin mimetic antibody fusion protein CNTO 528 was developed as a novel antibody fusion protein by constructing an active hematopoietic peptide onto an IgG1-based scaffold. This resulted in a molecule with a long circulating half-life and a prolonged effect of stimulating reticulocyte production and hemoglobin (Hgb) synthesis. To assess the safety, pharmacokinetics, and pharmacodynamics of CNTO 528, the authors gave 44 adult healthy male subjects single or fractionated doses of intravenous CNTO 528 or placebo. CNTO 528 was generally well tolerated. The maximum observed concentration (Cmax) and the area under the concentration versus time curve (AUC) increased in an approximately dose-dependent manner between the 0.09-mg/kg and 0.9-mg/kg doses. The maximum effect on the reticulocyte response occurred approximately 8 to 9 days after administration. A median increase in Hgb (> or =1 g/dL above baseline) was achieved 9 to 10 days after administration, with a maximum effect between 19 and 26 days. Two subjects in the 0.9-mg/kg dose group had elevated Hgb concentrations requiring phlebotomy. In this first-in-human study, CNTO 528 was well tolerated and effective in elevating and maintaining Hgb by at least 1 g/dL following a single intravenous administration, which suggests that an erythropoietin mimetic molecule, such as CNTO 528, may be an effective therapy for patients with anemia.

N-in-1 dosing pharmacokinetics in drug discovery: experience, theoretical and practical considerations.

N-in-1 (or cassette) dosing pharmacokinetics (PK) has been used in drug discovery for rapid assessment of PK properties of new chemical entities. However, because of potential for drug-drug interactions this procedure is still controversial. This study was to retrospectively evaluate the N-in-1 dosing approach in drug discovery with an emphasis on the potential for drug-drug interactions. The systemic clearance, volume of distribution, oral bioavailability, and renal excretion of the 31 lead compounds in rats, dogs or chimpanzees were significantly correlated between the N-in-1 dosing and discrete studies with r values of 0.69, 0.91, 0.53, and 0.83 (p < 0.005 for all), respectively. PK parameters for 11 quality control compounds which were involved in 194 N-in-1 studies for screening approximately 1000 compounds had coefficient of variations of less than 70%. The intrinsic microsomal clearances generated from the N-in-1 and discrete incubations were nearly identical (r = 0.97, p < 0.0001). The intrinsic clearances of quality control compound from the N-in-1 incubations were consistent with its discrete CL(int) estimate (cv: 5.4%). Therefore, N-in-1 dosing is a useful approach in drug discovery to quickly obtain initial PK estimates. Potential drug-drug interactions that result in confounding PK estimates do not occur as frequently as expected.

Pharmacokinetics and pharmacodynamics of DPC 333 ((2R)-2-((3R)-3-amino-3{4-[2-methyl-4-quinolinyl) methoxy] phenyl}-2-oxopyrrolidinyl)-N-hydroxy-4-methylpentanamide)), a potent and selective inhibitor of tumor necrosis factor alpha-converting enzyme in rodents, dogs, chimpanzees, and humans.

DPC 333 ((2R)-2-((3R)-3-amino-3{4-[2-methyl-4-quinolinyl) methoxy] phenyl}-2-oxopyrrolidinyl)-N-hydroxy-4-methylpentanamide)) is a potent and selective inhibitor of tumor necrosis factor (TNF)-alpha-converting enzyme (TACE). It significantly inhibits lipopolysaccharide-induced soluble TNF-alpha production in blood from rodents, chimpanzee, and human, with IC(50) values ranging from 17 to 100 nM. In rodent models of endotoxemia, DPC 333 inhibited the production of TNF-alpha in a dose-dependent manner, with an oral ED(50) ranging from 1.1 to 6.1 mg/kg. Oral dosing of DPC 333 at 5.5 mg/kg daily for 2 weeks in a rat collagen antibody-induced arthritis model suppressed the maximal response by approximately 50%. DPC 333 was distributed widely to tissues including the synovium, the site of action for antiarthritic drugs. Pharmacokinetic and pharmacodynamic studies in chimpanzee revealed a systemic clearance of 0.4 l/h/kg, a V(ss) of 0.6 l/kg, an oral bioavailability of 17%, and an ex vivo IC(50) for the suppression of TNF-alpha production of 55 nM (n = 1). In a phase I clinical trial with male volunteers after single escalating doses of oral DPC 333, the terminal half-life was between 3 and 6 h and the ex vivo IC(50) for suppressing TNF-alpha production was 113 nM. Measurement of the suppression of TNF-alpha production ex vivo may serve as a good biomarker in evaluating the therapeutic efficacy of TACE inhibitors. Overall, the pharmacological profiles of DPC 333 support the notion that suppression of TNF-alpha with TACE inhibitors like DPC 333 may provide a novel approach in the treatment of various inflammatory diseases including rheumatoid arthritis, via control of excessive TNF-alpha production.

Preparation of 1-(3-aminobenzo[d]isoxazol-5-yl)-1H-pyrazolo[4,3-d]pyrimidin-7(6H)-ones as potent, selective, and efficacious inhibitors of coagulation factor Xa.

Previously, potent factor Xa inhibitors were described based on the 1H-pyrazolo[4,3-d]pyrimidin-7(6H)-one bicyclic core and a 4-methoxyphenyl P1 moiety. This manuscript describes 1H-pyrazolo[4,3-d]pyrimidin-7(6H)-one and related bicyclic cores with the 3-aminobenzisoxazole P1 moiety. Many of these compounds are potent, selective, and efficacious inhibitors of coagulation factor Xa.

Preparation of 1-(4-methoxyphenyl)-1H-pyrazolo[4,3-d]pyrimidin-7(6H)-ones as potent, selective and bioavailable inhibitors of coagulation factor Xa.

Previously, potent factor Xa inhibitors were described based on a pyrazole core. Modifications of the pyrazole core have provided additional novel, highly potent factor Xa inhibitors. This manuscript will describe the synthesis and biological activity of factor Xa inhibitors containing the 1H-pyrazolo[4,3-d]pyrimidin-7(6H)-one and related bicyclic cores. Many of these compounds are potent, selective, and orally bioavailable inhibitors of coagulation factor Xa.

Phase I study of BMS-214662, a farnesyl transferase inhibitor in patients with acute leukemias and high-risk myelodysplastic syndromes.

PURPOSE: To investigate the dose-limiting toxicity (DLT) and maximum-tolerated dose (MTD) of BMS-214662, a farnesyl transferase (FTase) inhibitor, in patients with acute leukemias and high-risk myelodysplastic syndromes (MDS). PATIENTS AND METHODS: Patients with relapsed or refractory acute leukemias or MDS, or previously untreated but poor candidates for chemotherapy, were included in this phase I study with a 3 + 3 dose escalation design. BMS-214662 was administered as a 1-hour bolus once weekly at doses of 42 to 157 mg/m2. Once the MTD was identified, the schedule was changed to a 24-hour continuous infusion once weekly (starting dose, 300 mg/m2). RESULTS: Thirty patients were treated at a dose of 42 (n = 1), 56 (n = 3), 84 (n = 3), 118 (n = 13), 157 (n = 6) or 300 mg/m2 (n = 4). DLT occurred in 3 patients at 157 mg/m2, including nausea, vomiting, diarrhea, hypokalemia and cardiovascular problems. No DLT occurred with 24-hour continuous infusion. MTD with a 1-hour infusion was 118 mg/m2, with no MTD identified with the 24-hour infusion. Plasma concentrations of BMS-214662 correlated with the dose. Inhibition of FTase activity of approximately 60% occurred after the infusion with recovery to near baseline after 24 hours. Five patients had evidence of antileukemia activity, including two with complete remission with incomplete platelet recovery, one with hematologic improvement, and two with morphologic leukemia-free state. CONCLUSION: BMS-214662 is well tolerated at doses of up to 118 mg/m2 as a 1-hour infusion. The toxicity profile and efficacy may be improved with prolonged exposure. Further investigation of this agent in leukemia is warranted.

The chimpanzee (Pan troglodytes) as a pharmacokinetic model for selection of drug candidates: model characterization and application.

The chimpanzee (CHP) was evaluated as a pharmacokinetic model for humans (HUMs) using propranolol, verapamil, theophylline, and 12 proprietary compounds. Species differences were observed in the systemic clearance of theophylline (approximately 5-fold higher in CHPs), a low clearance compound, and the bioavailability of propranolol and verapamil (lower in CHPs), both high clearance compounds. The systemic clearance of propranolol (approximately 1.53 l/h/kg) suggested that the hepatic blood flow in CHPs is comparable to that in humans. No substantial differences were observed in the in vitro protein binding. A preliminary attempt was made to characterize cytochrome P450 (P450) activities in CHP and HUM liver microsomes. Testosterone 6beta-hydroxylation and tolbutamide methylhydroxylation activities were comparable in CHP and HUM liver microsomes. In contrast, dextromethorphan O-demethylation and phenacetin O-deethylation activities were approximately 10-fold higher (per mg protein) in CHP liver microsomes. Intrinsic clearance estimates in CHP liver microsomes were higher for propranolol (approximately 10-fold) and theophylline (approximately 5-fold) and similar for verapamil. Of the 12 proprietary compounds, 3 had oral clearances that differed in the two species by more than 3-fold, an acceptable range for biological variability. Most of the observed differences are consistent with species differences in P450 enzyme activity. Oral clearances of proprietary compounds in HUMs were significantly correlated to those from CHPs (r = 0.68; p = 0.015), but not to estimates from rat, dog, and monkey. In summary, the chimpanzee serves as a valuable surrogate model for human pharmacokinetics, especially when species differences in P450 enzyme activity are considered.

Structure-based design of novel guanidine/benzamidine mimics: potent and orally bioavailable factor Xa inhibitors as novel anticoagulants.

As part of an ongoing effort to prepare orally active factor Xa inhibitors using structure-based drug design techniques and molecular recognition principles, a systematic study has been performed on the pharmacokinetic profile resulting from replacing the benzamidine in the P1 position with less basic benzamidine mimics or neutral residues. It is demonstrated that lowering the pK(a) of the P1 ligand resulted in compounds (3-benzylamine, 15a; 1-aminoisoquinoline, 24a; 3-aminobenzisoxazole, 23a; 3-phenylcarboxamide, 22b; and 4-methoxyphenyl, 22a) with improved pharmacokinetic features mainly as a result of decreased clearance, increased volume of distribution, and enhanced oral absorption. This work resulted in a series of potent and orally bioavailable factor Xa inhibitors that ultimately led to the discovery of SQ311, 24a. SQ311, which utilizes a 1-aminoisoquinoline as the P1 ligand, inhibits factor Xa with a K(i) of 0.33 nM and demonstrates both good in vivo antithrombotic efficacy and oral bioavailability.