Ana I. Loureiro

Pharmacokinetic and safety profile of trans-resveratrol in a rising multiple-dose study in healthy volunteers

This was a double-blind, randomised, placebo-controlled study to investigate the pharmacokinetics and safety of trans-resveratrol. In four groups of ten healthy adult subjects (five males and five females), two subjects were randomized to receive placebo and eight subjects to receive trans-resveratrol 25, 50, 100 or 150 mg, six times/day, for thirteen doses. Peak plasma concentrations of trans-resveratrol were reached at 0.8-1.5 h postdose. Following the 13th dose of trans-resveratrol 25, 50, 100 and 150 mg, mean peak plasma concentration (C(max)) was 3.89, 7.39, 23.1 and 63.8 ng/mL and mean area under the plasma concentration-time curve (AUC(0-tau)) was 3.1, 11.2, 33.0 and 78.9 ng.h/mL. Interindividual variability was high, with coefficients of variation >40%. Trans-resveratrol half-life was 1-3 h following single-doses and 2-5 h following repeated dosing. Trough (C(min)) concentrations were < or = 1 ng/mL following 25 and 50 mg, 3 ng/mL following 100 mg and < 10 ng/mL following 150 mg. Trans-resveratrol pharmacokinetics showed circadian variation. Adverse events were mild in severity and similar between all groups. In conclusion, repeated administration was well-tolerated but produced relatively low plasma concentrations of trans-resveratrol, despite the high doses and short dosing interval used. Bioavailability was higher after morning administration.

Pharmacokinetics of Trans‐resveratrol Following Repeated Administration in Healthy Elderly and Young Subjects

From the Department of Research and Development, S Mamede do Coronado, Portugal (Dr Nunes, Dr Almeida, Mr Rocha, Mr Fernandes-Lopes, Ms Loureiro, Dr Wright, Dr Vaz-da-Silva, Dr Soares-da-Silva); Institute of Pharmacology and Therapeutics, Faculty of Medicine, University of Porto, Porto, Portugal (Dr Almeida, Dr Vaz-da-Silva, Dr Soares-da-Silva); Department of Health Sciences, University of Aveiro, Portugal (Dr Almeida); and 4Health Consulting, BIOCANT, Cantanhede, Portugal (Dr Falcao). Submitted for publication February 27, 2009; revised version accepted May 10, 2009. Address for correspondence: Patricio Soares-da-Silva, MD, PhD, Department of Research & Development, BIAL, A Av da Siderurgia Nacional, 4745-457 S Mamede do Coronado, Portugal; e-mail: psoares.silva@bial.com.DOI: 10.1177/0091270009339191

Eslicarbazepine and the enhancement of slow inactivation of voltage-gated sodium channels: A comparison with carbamazepine, oxcarbazepine and lacosamide

This study aimed at evaluating the effects of eslicarbazepine, carbamazepine (CBZ), oxcarbazepine (OXC) and lacosamide (LCM) on the fast and slow inactivated states of voltage-gated sodium channels (VGSC). The anti-epileptiform activity was evaluated in mouse isolated hippocampal slices. The anticonvulsant effects were evaluated in MES and the 6-Hz psychomotor tests. The whole-cell patch-clamp technique was used to investigate the effects of eslicarbazepine, CBZ, OXC and LCM on sodium channels endogenously expressed in N1E-115 mouse neuroblastoma cells. CBZ and eslicarbazepine exhibit similar concentration dependent suppression of epileptiform activity in hippocampal slices. In N1E-115 mouse neuroblastoma cells, at a concentration of 250 μM, the voltage dependence of the fast inactivation was not influenced by eslicarbazepine, whereas LCM, CBZ and OXC shifted the V0.5 value (mV) by -4.8, -12.0 and -16.6, respectively. Eslicarbazepine- and LCM-treated fast-inactivated channels recovered similarly to control conditions, whereas CBZ- and OXC-treated channels required longer pulses to recover. CBZ, eslicarbazepine and LCM shifted the voltage dependence of the slow inactivation (V0.5, mV) by -4.6, -31.2 and -53.3, respectively. For eslicarbazepine, LCM, CBZ and OXC, the affinity to the slow inactivated state was 5.9, 10.4, 1.7 and 1.8 times higher than to the channels in the resting state, respectively. In conclusion, eslicarbazepine did not share with CBZ and OXC the ability to alter fast inactivation of VGSC. Both eslicarbazepine and LCM reduce VGSC availability through enhancement of slow inactivation, but LCM demonstrated higher interaction with VGSC in the resting state and with fast inactivation gating.

Opicapone: a short lived and very long acting novel catechol-O-methyltransferase inhibitor following multiple dose administration in healthy subjects.

AIMS The aim of this study was to assess the tolerability, pharmacokinetics and inhibitory effect on erythrocyte soluble catechol-O-methyltransferase (S-COMT) activity following repeated doses of opicapone. METHODS This randomized, placebo-controlled, double-blind study enrolled healthy male subjects who received either once daily placebo or opicapone 5, 10, 20 or 30 mg for 8 days. RESULTS Opicapone was well tolerated. Its systemic exposure increased in an approximately dose-proportional manner with an apparent terminal half-life of 1.0 to 1.4 h. Sulphation was the main metabolic pathway. Opicapone metabolites recovered in urine accounted for less than 3% of the amount of opicapone administered suggesting that bile is likely the main route of excretion. Maximum S-COMT inhibition (Emax ) ranged from 69.9% to 98.0% following the last dose of opicapone. The opicapone-induced S-COMT inhibition showed a half-life in excess of 100 h, which was dose-independent and much longer than plasma drug exposure. Such a half-life translates into a putative underlying rate constant that is comparable with the estimated dissociation rate constant of the COMT-opicapone complex. CONCLUSION Despite its short elimination half-life, opicapone markedly and sustainably inhibited erythrocyte S-COMT activity making it suitable for a once daily regimen.

Computation of the binding affinities of catechol-O-methyltransferase inhibitors: multisubstate relative free energy calculations.

Alchemical free energy simulations are amongst the most accurate techniques for the computation of the free energy changes associated with noncovalent protein–ligand interactions. A procedure is presented to estimate the relative binding free energies of several ligands to the same protein target where multiple, low‐energy configurational substates might coexist, as opposed to one unique structure. The contributions of all individual substates were estimated, explicitly, with the free energy perturbation method, and combined in a rigorous fashion to compute the overall relative binding free energies and dissociation constants. It is shown that, unless the most stable bound forms are known a priori, inaccurate results may be obtained if the contributions of multiple substates are ignored. The method was applied to study the complex formed between human catechol‐O‐methyltransferase and BIA 9‐1067, a newly developed tight‐binding inhibitor that is currently under clinical evaluation for the therapy of Parkinsons disease. Our results reveal an exceptionally high‐binding affinity (Kd in subpicomolar range) and provide insightful clues on the interactions and mechanism of inhibition. The inhibitor is, itself, a slowly reacting substrate of the target enzyme and is released from the complex in the form of O‐methylated product. By comparing the experimental catalytic rate (kcat) and the estimated dissociation rate (koff) constants of the enzyme‐inhibitor complex, one can conclude that the observed inhibition potency (Ki) is primarily dependent on the catalytic rate constant of the inhibitors O‐methylation, rather than the rate constant of dissociation of the complex.

Eslicarbazepine acetate for the treatment of focal epilepsy: an update on its proposed mechanisms of action

Eslicarbazepine acetate (ESL) is a once daily antiepileptic drug (AED) approved by the European Medicines Agency (EMA), the Food and Drug Administration (FDA) and Health Canada as an adjunctive therapy in adults with partial‐onset seizures (POS). In humans and in relevant animal laboratory species, ESL undergoes extensive first pass hydrolysis to its major active metabolite eslicarbazepine that represents ~95% of circulating active moieties. ESL and eslicarbazepine showed anticonvulsant activity in animal models. ESL may not only suppress seizure activity but may also inhibit the generation of a hyperexcitable network. Data reviewed here suggest that ESL and eslicarbazepine demonstrated the following in animal models: (1) the selectivity of interaction with the inactive state of the voltage‐gated sodium channel (VGSC), (2) reduction in VGSC availability through enhancement of slow inactivation, instead of alteration of fast inactivation of VGSC, (3) the failure to cause a paradoxical upregulation of persistent Na+ current (INaP), and (4) the reduction in firing frequencies of excitatory neurons in dissociated hippocampal cells from patients with epilepsy who were pharmacoresistant to carbamazepine (CBZ). In addition, eslicarbazepine effectively inhibited high‐ and low‐affinity hCaV3.2 inward currents with greater affinity than CBZ. These preclinical findings may suggest the potential for antiepileptogenic effects; furthermore, the lack of effect upon KV7.2 outward currents may translate into a reduced potential for eslicarbazepine to facilitate repetitive firing.

Human metabolism of nebicapone (BIA 3-202), a novel catechol-o-methyltransferase inhibitor: characterization of in vitro glucuronidation.

Nebicapone (BIA 3-202; 1-[3,4-dihydroxy-5-nitrophenyl]-2-phenylethanone), a novel catechol-O-methyltransferase inhibitor, is mainly metabolized by glucuronidation. The purpose of this study was to characterize the major plasma metabolites of nebicapone following p.o. administration of nebicapone to healthy volunteers, and to determine the human UDP-glucuronosyltransferase (UGT) enzymes involved in nebicapone glucuronidation. Plasma samples were collected as part of a clinical trial at different time points postdose and were analyzed for nebicapone and its metabolites using a validated method consisting of a solid-phase extraction, followed by high-performance liquid chromatography/mass spectrometry detection. The primary metabolic pathways of nebicapone in humans involve mainly 3-O-glucuronidation, the major early metabolite, and 3-O-methylation, the predominant late metabolite. Of the nine commercially available recombinant UGT enzymes studied (UGT1A1, UGT1A3, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B7, and UGT2B15), only UGT1A9 exhibited high nebicapone glucuronosyltransferase specific activity (24.3 ± 1.3 nmol/mg protein/min). UGT1A6, UGT1A7, UGT1A8, UGT1A10, UGT2B7, and UGT2B15 exhibited low activity (0.1–1.1 nmol/mg protein/min), and UGT1A1 and UGT1A3 showed extremely low activities (less than 0.03 nmol/mg protein/min). The results show that nebicapone is mainly glucuronidated in humans and that multiple UGT enzymes are involved in this reaction.

Bioavailability and bioequivalence of two enteric-coated formulations of omeprazole in fasting and fed conditions

AbstractObjective: To investigate the relative bioavailability and bioequivalence, in fasting and fed conditions, of repeated doses of two omeprazole enteric-coated formulations in healthy volunteers. Material and methods: Open label, single-centre study consisting of two consecutive randomised, two-way crossover trials (a fasting trial and a fed trial). Each trial consisted of two 7-day treatment periods in which subjects received one daily dose of the test (Ompranyt®) or reference (Mopral®) formulations. At day 7 and day 14 (fasting trial), products were administered in fasting conditions and blood samples were taken for omeprazole plasma assay over 12 hours. At day 21 and day 28 (fed trial), products were administered after a standard high-calorie and high-fat meal and 12-hour blood samples taken. Omeprazole plasma concentrations were quantified by a validated method using a reverse-phase high performance liquid chromatography with UV detection (HPLC-UV). Results: Twenty-four subjects were enrolled and 23 completed the study. Under fasting conditions, the mean ± SD maximum omeprazole plasma concentration (Cmax) was 797 ± 471 μg/L for Ompranyt® and 747 ± 313 μg/L for Mopral® with a point estimate (PE) of 1.01 and a 90% confidence interval (CI) of 0.88, 1.16. The mean ± SD area under the plasma concentration curve from administration to last observed concentration (AUC0–12) was 1932 ± 1611 μg · h/L and 1765 ± 1327 μg · h/L for Ompranyt® and Mopral®, respectively (PE = 1.09; 90% CI 0.95, 1.25). In the presence of food, the Cmax was 331 ± 227 μg/L and 275 ± 162 μg/L (PE = 1.21; 90% CI 0.92, 1.59) and AUC0–12 was 1250 ± 966 μg · h/L and 1087 ± 861 μg · h/L (PE = 1.16; 90% CI 0.92, 1.47) for Ompranyt® and Mopral®, respectively. Bioequivalence of the formulations in the fasting condition was demonstrated both for AUC0–12 and for Cmax because the 90% CI lay within the acceptance range of 0.80–1.25. In contrast with the fasting condition, there were significant reductions in rate (Cmax) and extent (AUC0–12) of systemic exposure when test and reference formulations were administered with food. The food effect was more marked with Mopral® than with Ompranyt®, and the bioequivalence criterion was not fulfilled because the 90% CI fell out of the acceptance range of 0.80, 1.25, for both Cmax and AUC0–12. The two formulations were similarly well tolerated. Conclusion: Bioequivalence of Ompranyt® (test formulation) and Mopral® (reference) formulations was demonstrated after repeated dosing in the fasting condition. Following a high-calorie and high-fat meal, there was a significant reduction in rate and extent of systemic exposure for both products, with Ompranyt® being less affected than Mopral® by the presence of food.

BIA 3-202, a novel catechol-O-methyltransferase inhibitor, enhances the availability of l-DOPA to the brain and reduces its O-methylation

1-[3,4-Dihydroxy-5-nitrophenyl]-2-phenyl-ethanone (BIA 3-202) is a new long-acting catechol-O-methyltransferase (COMT) inhibitor with limited access to the brain. The present study evaluated the interference of BIA 3-202 upon levels of L-3,4-dihydroxyphenylalanine (L-DOPA) and metabolites in plasma (3-O-methyl-L-DOPA) and brain [3-O-methyl-L-DOPA, dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA)] in rats orally treated with L-DOPA (20 mg/kg) plus benserazide (30 mg/kg). At different time points (1, 3 and 6 h) after the administration of BIA 3-202 (0, 3, 10 and 30 mg/kg) or L-DOPA plus benserazide, rats were sacrificed and the right striatum was quickly dissected out and stored for the assay of L-DOPA, 3-O-methyl-L-DOPA, dopamine and amine metabolites. Levels of L-DOPA, 3-O-methyl-L-DOPA, dopamine, DOPAC and HVA in the striatum in L-DOPA plus benserazide-treated rats were higher than in vehicle-treated rats. However, this increase in striatal L-DOPA, dopamine, DOPAC and HVA was, in a dose- and time-dependent manner, even higher (P<0.05) in rats given BIA 3-202 (3, 10 and 30 mg/kg). This effect was accompanied by a marked decrease in 3-O-methyl-L-DOPA levels in the striatum of L-DOPA plus benserazide-treated rats. Increases in levels of L-DOPA and decreases in 3-O-methyl-L-DOPA levels in plasma also accompanied the administration of BIA 3-202. BIA 3-202 did not significantly affect levels of DOPAC and HVA in the striatum in vehicle-treated rats. It is concluded that administration of BIA 3-202 enhances the availability of L-DOPA to the brain by reducing its O-methylation in the periphery, which may prove beneficial in parkinsonian patients treated with L-DOPA plus an aromatic amino acid decarboxylase inhibitor.

Single‐Dose Tolerability, Pharmacokinetics, and Pharmacodynamics of Etamicastat (BIA 5–453), a New Dopamine β‐Hydroxylase Inhibitor, in Healthy Subjects

The safety, tolerability, pharmacokinetics, and pharmacodynamics of etamicastat (BIA 5–453), a novel dopamine β‐hydroxylase (DβH) inhibitor, were investigated in 10 sequential groups of 8 healthy male subjects under a double‐blind, randomized, placebo‐controlled design. In each group, 6 subjects received a single dose of etamicastat (2, 10, 20, 50, 100, 200, 400, 600, 900, or 1200 mg) and 2 subjects received placebo. Etamicastat was well tolerated at all dose levels tested. Maximum plasma etamicastat concentrations occurred at 1 to 3 hours postdose. Elimination was biphasic, characterized by a first short early elimination half‐life followed by a longer elimination phase of 16 to 20 hours for etamicastat doses of 100 mg and above. A high interindividual variability of pharmacokinetic parameters of etamicastat and its acetylated metabolite was observed. Pharmacogenomic data showed that N‐acetyltransferase type 2 (NAT2) phenotype (rapid or slow N‐acetylating ability) was a major source of variability. In NAT2 poor acetylators, the area under the plasma concentration‐time curve from time zero to the last sampling time at which concentrations were at or above the limit of quantification (AUC0‐t) of etamicastat was twice that observed in rapid acetylators. Consistent with that finding, AUC0‐t of the acetylated metabolite was markedly higher in NAT2 rapid acetylators compared with poor acetylators. Inhibition of DβH activity was observed, reaching statistical significance for etamicastat doses of 100 mg and above.