Overview of preclinical and clinical studies investigating pharmacokinetics and drug-drug interactions of padsevonil.

BACKGROUND: Padsevonil is an antiseizure medication candidate intended to benefit patients with drug-resistant epilepsy. Our investigations aimed at characterizing pharmacokinetics and drug-drug interaction (DDI) profile of padsevonil. RESEARCH DESIGN AND METHODS: An overview of preclinical and clinical pharmacology studies conducted during padsevonil development is provided. RESULTS: In preclinical studies, cytochrome (CYP) 3A4 was identified as the main P450 isoform involved in padsevonil metabolism, with potential minor contribution from CYP2C19. Padsevonil was shown to be a time-dependent CYP2C19-inhibitor, weak CYP3A4-inducer, weak inhibitor of P-gp/OCT1/MATE2-K, and potent OCT2-inhibitor. Initial clinical pharmacology studies in healthy participants showed that padsevonil had (i) good absorption, (ii) clearance mediated mainly by metabolism, and (iii) time-dependent kinetics. A study in genotyped participants confirmed the role of CYP2C19 in clearance and time-dependent kinetics; the major contribution of CYP3A4 was confirmed in DDI studies with CYP3A4-inducers (carbamazepine, oxcarbazepine) and -inhibitor (erythromycin). Padsevonil did not affect pharmacokinetics of valproate/lamotrigine/levetiracetam/oxcarbazepine or oral contraceptives. In a cocktail clinical study, padsevonil showed moderate CYP2C19 inhibition (omeprazole) and weak CYP3A4 induction (oral midazolam). No specific effects on CYP1A2 (caffeine), CYP2C9 (S-warfarin), and CYP2D6 (dextromethorphan) were observed. CONCLUSIONS: The studies presented helped in understanding padsevonil disposition and risks of DDIs, which would inform dosing and prescribing. CLINICAL TRIAL REGISTRATION: https://www.clinicaltrials.gov identifiers are NCT04131517, NCT03480243, NCT03695094, NCT04075409.

Assessment of a white matter reference region for 11C-UCB-J PET quantification.

11C-UCB-J is a positron emission tomography (PET) radioligand that has been used in humans for synaptic vesicle glycoprotein 2A (SV2A) imaging and as a potential synaptic density marker. The centrum semiovale (CS) is a proposed reference region for noninvasive quantification of 11C-UCB-J, due to negligible concentrations of SV2A in this region in baboon brain assessed by in vitro methods. However, in displacement scans with SV2A-specific drug levetiracetam in humans, a decrease in 11C-UCB-J concentration was observed in the CS, consistent with some degree of specific binding. The current study aims to validate the CS as a reference region by (1) optimizing CS region of interest (ROI) to minimize spill-in from gray matter with high radioactivity concentrations; (2) investigating convergence of CS ROI values using ordered subset expectation maximization (OS-EM) reconstruction, and (3) comparing baseline CS volume of distribution (VT) to nondisplaceable uptake in gray matter, VND. Improving ROI definition and increasing OS-EM iterations during reconstruction decreased the difference between CS VT and VND. However, even with these corrections, CS VT overestimated VND by ∼35-40%. These measures showed significant correlation, suggesting that, though biased, the CS may be a useful estimate of nondisplaceable uptake, allowing for noninvasive quantification for SV2A PET.

A pharmacokinetic study of radiprodil oral suspension in healthy adults comparing conventional venous blood sampling with two microsampling techniques.

In this phase I, single-center, open-label study of ten heathy adults (18-45 years; NCT02647697), the PK, safety, and tolerability profile of radiprodil oral suspension in healthy adults were assessed, as well as two PK microsampling techniques. All participants received a single 30 mg radiprodil dose (12 mL oral suspension). Blood was collected at various time points using conventional venous sampling (intravenous catheter or venepuncture), and Mitra™ and Aqua-Cap™ Drummond microsampling (finger-prick and blood taken from venous blood sample tubes). Geometric mean radiprodil plasma concentrations from conventional venous samples were above the lower limit of quantification up to 48 hours after administration of a single oral dose of radiprodil. Geometric mean AUC inf and Cmax were 2042 h ng mL -1 and 89.4 ng mL -1, respectively. Geometric mean t½ was 15.8 hour; median tmax was 4 hour (range: 3-6 hour). Radiprodil exposure variables for Aqua-Cap™ Drummond sampling were similar to the conventional venous-derived data. Conversely, radiprodil exposure variables were lower with Mitra™ sampling compared with conventional venous sampling. The geometric mean ratio (90% confidence interval) for Cmax of conventional venous versus Mitra™ and Aqua-Cap™ Drummond sampling (finger-prick blood) was 0.89 (0.85, 0.94) and 1.03 (0.97,1.08), respectively, and therefore within the conventional bioequivalence range (0.80-1.25). Radiprodil oral suspension had an acceptable safety, tolerability, and palatability profile. The PK profile of radiprodil oral suspension was established in healthy adults, and was comparable when analyzed using conventional versus microsampling techniques. These results will support future radiprodil paediatric studies.

Effect of the novel anxiolytic drug deramciclane on cytochrome P(450) 2D6 activity as measured by desipramine pharmacokinetics.

BACKGROUND: In vitro findings have indicated that the novel anxiolytic drug, deramciclane, is an inhibitor of the cytochrome P(450) (CYP) 2D6 enzyme and co-administration of deramciclane and the CYP2D6 probe drug desipramine is possible in clinical practice. OBJECTIVE: To evaluate the effects of deramciclane on CYP2D6 activity as measured by desipramine pharmacokinetics and pharmacodynamics using paroxetine as a positive control for CYP2D6 inhibition. METHODS: Fifteen healthy subjects received either 60 mg deramciclane, 20 mg paroxetine or matched placebo for 8 days in randomized order in this double-blind, cross-over study. On day 8 of each study phase, the subjects received a 100-mg single dose of desipramine. Desipramine and its CYP2D6-dependent metabolite, 2-OH-desipramine, concentrations were measured for 240 h. Measurement of secretion of saliva, Visual Analogue Scale assessment of dryness of mouth and tiredness were carried out on day 7 and day 8 to assess the pharmacodynamic consequences of deramciclane or paroxetine co-administration with desipramine. RESULTS: Repeated administration of deramciclane doubled the AUC of desipramine ( P<0.001), while paroxetine caused a 4.8-fold increase in the AUC of desipramine ( P<0.001). Significant correlations were observed with paroxetine (r(s)=0.84, P<0.001) and deramciclane (r(s)=0.51, P=0.0498) concentrations and the magnitude of increase of desipramine AUC. Both deramciclane and paroxetine decreased the formation of 2-OH-desipramine in the first-pass phase. The AUC ratio of 2-OH-desipramine/desipramine was decreased by 39% ( P<0.001) by deramciclane and by 74% ( P<0.001) by paroxetine. There were no changes in the secretion of saliva during co-administration of desipramine with deramciclane compared with placebo. CONCLUSION: Although deramciclane seems to be a weaker inhibitor of CYP2D6 than paroxetine, dose adjustment of drugs metabolized by CYP2D6 may be needed when used concomitantly with deramciclane.

Pharmacokinetics and tolerability of a new manidipine and delapril fixed oral combination in young and elderly subjects.

OBJECTIVES: The aim of the present study was to compare the pharmacokinetic and pharmacodynamic properties of a fixed combination tablet containing 10 mg of manidipine dihydrochloride (CAS 89226-75-5), a calcium channel antagonist, and 30 mg of delapril hydrochloride (CAS 83435-67-0), an angiotensin converting enzyme (ACE) inhibitor, during once daily repeated dosing in young and elderly subjects and to assess the bioequivalence of the fixed combination tablet and the single ingredient tablets taken simultaneously in young healthy subjects after a single dose administration. METHODS: Eighteen young healthy male volunteers received a single oral dose of 10 mg manidipine and 30 mg delapril as two separate tablets or a fixed combination tablet, followed by a week of once daily dosing with the fixed combination. Eight male and eight female elderly volunteers also received a week of once daily dosing with the fixed combination. Blood samples were collected during 24 h on the first and last treatment day for plasma determination of manidipine, delapril and their main metabolites, using specific LC-MS/MS methods. Blood pressure and heart rate were also recorded during 24 h. RESULTS: Bioequivalence was strictly demonstrated between the extemporaneous and the fixed combination tablet after single dose administration. At steady-state in young subjects, manidipine AUC and Cmax were lower (-8 and -12%) and t1/2 was longer (+45%), while delapril and metabolites were little affected as compared to single dose. In elderly subjects, manidipine Cmax was 4% lower than after single dose, AUC was 13% higher, and t1/2 was increased 2.4-fold. For delapril and active metabolites, Cmax and AUC increased modestly. Blood pressure and heart rate versus time profiles after single dose and at steady-state were almost superimposable. In elderly compared to young subjects at steady-state, peak concentrations of manidipine and delapril changed by +35% and -15% while AUCs increased by +70% and +9.7%. CONCLUSION: The fixed combination tablet of 10 mg manidipine and 30 mg delapril is bioequivalent to mono-ingredient tablets. At steady-state, the pharmacokinetic and pharmacodynamic profiles in young and elderly subjects undergo minor changes and indicate negligible accumulation. Drug exposure is higher in elderly subjects.

Pharmacokinetic profile of a new controlled-release isosorbide-5-mononitrate 60 mg scored tablet (Monoket Multitab).

The influences of food, tablet splitting, and fractional dosing on the pharmacokinetics of a new controlled-release double-scored tablet containing 60 mg isosorbide-5-mononitrate (Monoket Multitab) were investigated in healthy male volunteers. Food interaction was evaluated after single dose administration under fasted conditions and after a standard high-fat breakfast. The effect of tablet splitting was assessed at steady-state, after 5 days of once daily dosing with the tablet taken intact or trisected. The influence of fractional dosing was assessed after 1 and 6 days of daily regimen of 40 mg in the morning (2/3 of a tablet) and 20 mg in the evening (1/3 of a tablet). The pharmacokinetics of isosorbide-5-mononitrate after taking the tablet intact or in three fragments were very similar with a mere 10% increase of maximum plasma concentration (C(max)) for the latter, while the time to peak (T(max)) decreased from 5 to 4 h and areas under the concentration vs. time curves (AUCs) were virtually unchanged. Morning trough concentration reached 53 and 46 ng/ml, respectively. Administration of the intact tablet after a high-fat breakfast increased C(max) by 18% and AUC by 21%, and slightly delayed T(max) from 5 to 6h. During fractional dosing, morning and evening C(max) reached 364 and 315 ng/ml on the first day, and 373 and 300 ng/ml on the 6th day, respectively. The ratio of AUC(0-24 h) on the last day to AUC(infinity) on the first day, was 82.1% (confidence limits 71.7-94.1%) possibly resulting from peripheral volume expansion. The release characteristics of Monoket Multitab are thus moderately influenced by concomitant intake of food and to a very minor extent by tablet breaking. Fractional dosing allows to achieve lower peak and higher morning trough levels, while total exposure is comparable to that during once daily dosing (AUC(0-24 h, s.s.) of 5.55+/-1.78 and 5.71+/-1.08 microg h/ml).