Prediction of the Renal Organic Anion Transporter 1 (OAT1)- Mediated Drug Interactions for LY404039, the Active Metabolite of Pomaglumetad Methionil.

PURPOSE: The objective of this work was to demonstrate that clinical OAT1-mediated DDIs can be predicted using physiologically based pharmacokinetic (PBPK) modeling. METHODS: LY404039 is a metabotropic glutamate receptor 2/3 agonist and the active moiety of the prodrug pomaglumetad methionil (LY2140023). After oral administration, pomaglumetad methionil is rapidly taken up by enterocytes via PEPT1 and once absorbed, converted to LY404039 via membrane dehydropeptidase 1 (DPEP1). LY404039 is renally excreted by both glomerular filtration and active secretion and in vitro studies showed that the active secretion of LY404039 was mediated by the organic anion transporter 1 (OAT1). Both clinical and in vitro data were used to build a PBPK model to predict OAT1-mediated DDIs. RESULTS: In vitro inhibitory potencies (IC50) of the known OAT inhibitors, probenecid and ibuprofen, were determined to be 4.00 and 2.63 µM, respectively. Subsequently, clinical drug-drug interaction (DDI) study showed probenecid reduced the renal clearance of LY404039 by 30 to 40%. The PBPK bottom-up model, predicted a renal clearance that was approximately 20% lower than the observed one. The middle-out model, using an OAT1 relative activity factor (RAF) of 3, accurately reproduced the renal clearance of LY404039 and pharmacokinetic (PK) changes of LY404039 in the presence of probenecid. CONCLUSIONS: OAT1- mediated DDIs can be predicted using in vitro measured IC50 and PBPK modeling. The effect of ibuprofen was predicted to be minimal (AUC ratio of 1.15) and not clinically relevant.

In Vitro and Clinical Evaluations of the Drug-Drug Interaction Potential of a Metabotropic Glutamate 2/3 Receptor Agonist Prodrug with Intestinal Peptide Transporter 1.

Despite peptide transporter 1 (PEPT1) being responsible for the bioavailability for a variety of drugs, there has been little study of its potential involvement in drug-drug interactions. Pomaglumetad methionil, a metabotropic glutamate 2/3 receptor agonist prodrug, utilizes PEPT1 to enhance absorption and bioavailability. In vitro studies were conducted to guide the decision to conduct a clinical drug interaction study and to inform the clinical study design. In vitro investigations determined the prodrug (LY2140023 monohydrate) is a substrate of PEPT1 with Km value of approximately 30 µM, whereas the active moiety (LY404039) is not a PEPT1 substrate. In addition, among the eight known PEPT1 substrates evaluated in vitro, valacyclovir was the most potent inhibitor (IC50 = 0.46 mM) of PEPT1-mediated uptake of the prodrug. Therefore, a clinical drug interaction study was conducted to evaluate the potential interaction between the prodrug and valacyclovir in healthy subjects. No effect of coadministration was observed on the pharmacokinetics of the prodrug, valacyclovir, or either of their active moieties. Although in vitro studies showed potential for the prodrug and valacyclovir interaction via PEPT1, an in vivo study showed no interaction between these two drugs. PEPT1 does not appear to easily saturate because of its high capacity and expression in the intestine. Thus, a clinical interaction at PEPT1 is unlikely even with a compound with high affinity for the transporter.

Absolute bioavailability of evacetrapib in healthy subjects determined by simultaneous administration of oral evacetrapib and intravenous [(13) C8 ]-evacetrapib as a tracer.

This open-label, single-period study in healthy subjects estimated evacetrapib absolute bioavailability following simultaneous administration of a 130-mg evacetrapib oral dose and 4-h intravenous (IV) infusion of 175 µg [(13) C8 ]-evacetrapib as a tracer. Plasma samples collected through 168 h were analyzed for evacetrapib and [(13) C8 ]-evacetrapib using high-performance liquid chromatography/tandem mass spectrometry. Pharmacokinetic parameter estimates following oral and IV doses, including area under the concentration-time curve (AUC) from zero to infinity (AUC[0-∞]) and to the last measureable concentration (AUC[0-tlast ]), were calculated. Bioavailability was calculated as the ratio of least-squares geometric mean of dose-normalized AUC (oral : IV) and corresponding 90% confidence interval (CI). Bioavailability of evacetrapib was 44.8% (90% CI: 42.2-47.6%) for AUC(0-∞) and 44.3% (90% CI: 41.8-46.9%) for AUC(0-tlast ). Evacetrapib was well tolerated with no reports of clinically significant safety assessment findings. This is among the first studies to estimate absolute bioavailability using simultaneous administration of an unlabeled oral dose with a (13) C-labeled IV microdose tracer at about 1/1000(th) the oral dose, with measurement in the pg/mL range. This approach is beneficial for poorly soluble drugs, does not require additional toxicology studies, does not change oral dose pharmacokinetics, and ultimately gives researchers another tool to evaluate absolute bioavailability.

Effect of pomaglumetad methionil on the QT interval in subjects with schizophrenia.

OBJECTIVE: This thorough QT/QTc (TQT) study assessed the effects of a supratherapeutic dose of pomaglumetad methionil, a potential treatment for schizophrenia, compared to placebo on the QT interval in subjects with schizophrenia. METHODS: This double-blind, 3-period crossover study enrolled 86 subjects aged 22 - 63 years, who met Diagnostic and Statistical Manual, Fourth Edition, Test Revision (DSM-IV-TR) criteria for schizophrenia; 78 subjects completed the study. Subjects were randomly assigned to sequences of 3 treatment periods of single oral doses of pomaglumetad methionil 400 mg, moxifloxacin 400 mg, and placebo. Quadruplicate electrocardiograms (ECGs) were extracted from 2 hours predose to 12 hours postdose and were overread by a blinded central reader. Time-matched pharmacokinetic (PK) parameters were assessed. RESULTS: At all-time points, the upper bound of the 90% 2-sided confidence interval (CI) for the least squares (LS) mean difference in changes from baseline in Fridericia's corrected QT interval (ΔQTcF) between pomaglumetad methionil and placebo was < 10 milliseconds (msec). Sufficient assay sensitivity was not achieved, likely due to food effect; although the maximum observed drug concentration (Cmax) with moxifloxacin (1,410 ng/mL) was lower than expected, the slope of the regression line of moxifloxacin plasma concentrations versus placebo-subtracted ΔQTcF was similar to that reported in the literature. CONCLUSIONS: A single supratherapeutic dose of 400 mg pomaglumetad methionil did not prolong QTcF to a clinically significant degree and, importantly, did not result in any absolute QTcF > 450 msec or increase in QTcF from predose > 30 msec.

The effects on metabolic clearance when administering a potent CYP3A autoinducer with the prototypic CYP3A inhibitor, ketoconazole.

Ketoconazole is recognized as the prototypical CYP3A inhibitor and is often used to determine the metabolic CYP3A liabilities of new chemical entities in preclinical and clinical studies. Ketoconazole has been commercially available for approximately 30 years and was marketed before drug-metabolizing enzymes were well characterized; consequently, little is known about its metabolic profile. Semagacestat, a γ-secretase inhibitor investigated as a potential therapy for Alzheimer's disease, was determined to be a potent CYP3A autoinducer in human hepatocytes. Two human studies were conducted to assess the induction potential of semagacestat. In the first study (study 1, n = 20), semagacestat increased the mean apparent clearance (CL/F) of oral midazolam (76-324 l/h) and nifedipine (63-229 l/h) as predicted from hepatocytes. In a second (steady-state) study (study 2, n = 20), semagacestat CL/F increased from 22 after a single dose to 31 l/h. Ketoconazole decreased semagacestat CL/F by 32% after a single dose of semagacestat [geometric means ratio estimate, 0.68; 90% confidence interval (CI). 0.64, 0.73] and 46% at steady state (geometric means ratio estimate. 0.54; 90% CI, 0.51, 0.58). Ketoconazole area under the concentration-time curve over 8 h decreased 49% from first to last day of semagacestat dosing. Semagacestat significantly increases the oral clearance of CYP3A substrates, confirming its inducer designation. More importantly, when administered with a potent CYP3A inducer at steady state, ketoconazole's plasma exposure decreased, indicating that it may also be cleared by CYP3A, other inducible enzymes or transporters, or both.

QT effect of semagacestat at therapeutic and supratherapeutic doses.

OBJECTIVE: This thorough QT/ QT interval corrected for heart rate (QTc) study was designed to assess the potential of semagacestat, a functional gamma-secretase inhibitor, to delay cardiac repolarization. METHODS: In this Phase I, single-dose, randomized, 4-period crossover study, semagacestat was compared with placebo in 54 healthy male and female subjects between the ages of 19 and 63 years, inclusive. Each study period included single oral-dose administrations of semagacestat 140 mg, semagacestat 280 mg, moxifloxacin 400 mg, or placebo. Study subjects and the investigator were blinded to the identity of semagacestat and placebo; however, moxifloxacin was administered as open-label. Moxifloxacin was compared with placebo for assay sensitivity analysis. Pharmacokinetic parameters were also assessed. RESULTS: For each QTc, the upper bound of the 2-sided 90% confidence interval (CI) for the least squares mean difference between semagacestat (at both the 140- and 280-mg dose levels) and placebo was < 10 msec at all time points, and thus, within the limits set for clinical relevance in regulatory guidelines. CONCLUSIONS: The results of this study indicate that single doses of 140 and 280 mg semagacestat did not prolong QTc to a clinically significant degree.

Disposition and metabolism of semagacestat, a {gamma}-secretase inhibitor, in humans.

Semagacestat is a functional gamma-secretase inhibitor that has been shown to reduce the rate of formation of amyloid-beta in vitro and in vivo. This study was conducted to characterize the disposition of semagacestat in humans. After a single 140-mg dose of [(14)C]semagacestat administered as an oral solution to six healthy male subjects, semagacestat was rapidly absorbed (T(max) approximately 0.5 h) and eliminated from the systemic circulation (terminal t(1/2) approximately 2.4 h). The major circulating metabolites of semagacestat, M2 (hydrolysis of the amide bond proximal to the benzazepine ring) and M3 (benzylic hydroxylation of the benzazepine ring), accounted for approximately 27 and 10% of total radioactivity exposure, respectively, as calculated from relative area under the plasma concentration versus time curve from 0 to 24 h derived from the plasma radiochromatograms. The radioactive dose was almost completely recovered after 7 days postdose, with 87% of the dose in urine and 8% in feces. Unchanged [(14)C]semagacestat in urine accounted for approximately 44% of the dose, which indicates that renal excretion played an important role in elimination. Metabolites M2 and M3, with their related secondary metabolites, each accounted for approximately 20% of the dose in excreta. In vitro data indicate the formation of M3 is primarily mediated by CYP3A, with cDNA-expressed CYP3A5 approximately 2 times more efficient than CYP3A4 in forming M3. Thus, the relative content of CYP3A4 and CYP3A5 in humans will likely determine the formation clearance of M3 after exposure to semagacestat.

Relative contributions of presystemic and systemic peptidases to oral exposure of a novel metabotropic glutamate 2/3 receptor agonist (LY404039) after oral administration of prodrug pomaglumetad methionil (LY2140023).

Pomaglumetad methionil (LY2140023) is the prodrug of a novel metabotropic glutamate 2/3 receptor agonist (LY404039) being investigated for the treatment of schizophrenia. Using accelerator mass spectrometry (AMS) and an intravenous (i.v.) radiolabeled tracer approach, the absolute bioavailability of the prodrug and the extent of its conversion to active moiety (LY404039) were estimated at presystemic (intestinal/first pass) and systemic sites after simultaneous oral and i.v. dosing in healthy subjects. The mean absolute bioavailability of prodrug (80 mg oral) was 0.68. On the basis of these data and a previous radiolabeled mass balance study in which no prodrug was recovered in feces, we concluded that 0.32 of the dose is converted to active drug in the intestinal tract. The fraction of prodrug converted to active moiety was approximately 1, indicating complete conversion of the prodrug that reaches the systemic circulation to the active moiety. Prodrug (80 mg oral and 100 µg i.v.) and active moiety (100 µg i.v.) were well tolerated in healthy subjects. Thus, the absolute bioavailability of prodrug LY2140023 and the fraction converted presystemically and systemically to active moiety LY404039 were estimated simultaneously using radiolabeled tracer microdosing and AMS.

Semagacestat pharmacokinetics are not significantly affected by formulation, food, or time of dosing in healthy participants.

Semagacestat, a γ-secretase inhibitor, reduces formation of amyloid beta peptide. Two single-dose (140 mg), open-label, randomized, 3-period, crossover studies evaluated the effect of formulation, food, and time of dosing on the pharmacokinetics and pharmacodynamics of semagacestat in healthy participants. The first study (n = 14) compared tablet to capsules. For all formulations, the median time to maximum plasma concentration (t(max)) was generally 1.0 hour. Plasma elimination was rapid, with a half-life of approximately 2.5 hours. Tablet form II bioavailability (F) relative to capsule was approximately 100% (F = 1.03 [90% confidence interval (CI), 0.96-1.10]). In the second study, participants (n = 27) received semagacestat either fed or fasting in the morning or fasting in the evening. No significant change in exposure (AUC(0-∞) [area under the concentration-time curve from 0 to infinity] ratio = 1.02, [90% CI, 0.990-1.05]) occurred with food, whereas maximum plasma concentration (C(max)) declined approximately 15%, and median t(max) was delayed to 1.5 hours. Time of dosing made no significant difference in AUC(0-∞), C(max), or t(max) (AUC(0-∞) ratio 1.01, [90% CI, 0.975-1.04]). No clinically significant safety concerns occurred in either study. Accordingly, semagacestat may be dosed without regard to formulation, food, or time of administration.

The disposition and metabolism of naveglitazar, a peroxisome proliferator-activated receptor alpha-gamma dual, gamma-dominant agonist in mice, rats, and monkeys.

Naveglitazar [LY519818; benzenepropanoic acid, alpha-methoxy-4-[3-(4-phenoxyphenoxy)propoxy], (alpha-S)-] is a nonthiozolidinedione peroxisome proliferator-activated receptor alpha-gamma dual, gamma-dominant agonist that has shown glucose-lowering potential in animal models and in the clinic. Studies have been conducted to characterize the disposition, metabolism, and excretion of naveglitazar in mice, rats, and monkeys after oral and/or i.v. bolus administration. After oral administration of [(14)C]naveglitazar, naveglitazar was well absorbed and moderately metabolized in all species evaluated, with total recoveries of radioactivity ranging from 90 to 96%. Naveglitazar was the most abundant peak observed in circulation at C(max), representing 68 to 81% of the total radioactivity in plasma. The most prominent metabolite observed in circulation was the R-enantiomer of naveglitazar, LY591026, which is formed via enzymatic chiral inversion. para-Hydroxy naveglitazar and the sulfate conjugate of para-hydroxy naveglitazar were also observed in circulation in most species, especially in the monkey. The metabolic pathways observed include enzymatic chiral inversion, aromatic hydroxylation, oxidative dehydrogenation, and/or various phase II conjugation pathways. Naveglitazar was highly bound to plasma proteins among the species examined (>99%), and binding was independent of concentration. Biliary excretion was recognized as the most prominent excretion pathway in bile duct-cannulated rats (79 of the 96% recovered), producing an acyl glucuronide conjugate of naveglitazar and a sulfate and glucuronide diconjugate of para-hydroxy naveglitazar, which were shown to be reversible. The primary excretory pathway observed in mice and monkeys was via the feces. In summary, naveglitazar was well absorbed, moderately metabolized, and excreted via the feces in mice, rats, and monkeys.