ABSTRACT:Semagacestat is a functional ␥-secretase inhibitor that has been shown to reduce the rate of formation of amyloid-␤ 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 ϳ0.5 h) and eliminated from the systemic circulation (terminal t 1/2 ϳ2.4 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 radiochro- Alzheimer's disease (AD) is a progressive, neurodegenerative disease characterized by cognitive impairment. The prevalence rate is approximately 6% among those aged more than 65 years. Currently more than 4 million Americans suffer from AD, and this number is expected to quadruple by year 2050 as average lifespan increases (Rice et al., 2001;Joyce et al., 2007). AD has a substantial impact on patients, caregivers, and the healthcare system. Average total medical costs for AD patients are more than 5-fold higher than those for control populations. Development of pharmaceuticals for the treatment of AD would greatly benefit AD patients and society. The cause of AD is not yet clear. Pathological studies revealed the existence of neuritic plaques in the brains of AD patients (Desai and Grossberg, 2005;Blennow et al., 2006). The plaques are mainly composed of amyloid-␤ (A␤) peptides that are formed by the sequential cleavage of the amyloid precursor protein (APP). APP is first cleaved by the ␤-site APP-cleaving enzyme to form the N terminus of A␤, which is further cleaved by ␥-secretase at multiple sites to form A␤ isoforms ranging from 37 (A␤37) to 43 (A␤43) residues (Olson and Albright, 2008). Mutations in APP near cleavage sites resulting in the A␤ formation have been linked to AD in several families (Selkoe, 2001;Imbimbo, 2008). This observation suggests that a reduction in A␤ synthesis could slow the disease progression in patients with AD.Semagacestat, an azepine class ␥-secretase inhibitor, is one of a very few ␥-secretase inhibitors that have been advanced into clinical trials as potential disease-modifying agents for the treatment of AD (Olson and Albright, 2008). Semagacestat reduces the rate of formation of A␤ in whole cell assays, as well as in transgenic and nontransgenic mice, beagle dogs, and guinea pigs Hyslop et al., 2004;May et al., 2004;Lanz et al., 2006). A transgenic mouse model of AD was generated using a platelet-derived growth factor ␤ promoter driving a human APP minigene encoding the APP V171F mutation (PDAPP mouse). These mice express high levels of human mutant APP and progressively develop many of the pathologArticle, publication date, and citation ...

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ABSTRACT:Naveglitazar [LY519818; benzenepropanoic acid, ␣-methoxy-4-[3-(4-phenoxyphenoxy)propoxy], (␣-S)-] is a nonthiozolidinedione peroxisome proliferator-activated receptor ␣-␥ dual, ␥-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 Renantiomer 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.Type 2 diabetes mellitus is a major and expanding health issue throughout the world (Burke et al., 1999). This form of diabetes, which constitutes 90% of all diabetes cases, is characterized by hepatic and peripheral insulin resistance, and impaired ␤-cell function and insulin secretion (Diamant and Heine, 2003). In addition to elevated glucose levels, type 2 diabetes is most often associated with a variety of cardiovascular risk factors including dyslipidemia, hypertension, and obesity (DeFronzo, 1992;Ferrannini, 1998).Naveglitazar [LY519818; benzenepropanoic acid, ␣-methoxy-4-[3-(4-phenoxyphenoxy)propoxy], (␣-S)-] (Fig. 1), is a peroxisome proliferator-activated receptor (PPAR) ␣-␥ dual, ␥-dominant agonist. PPAR compounds are members of the nuclear receptor superfamily, and have been shown to play a role in lipid and carbohydrate homeostasis (Keller et al., 1993). PPAR-␥, which is predominately expressed in adipose tissue, regulates the transcription of genes involved in glucose and lipid metabolism (Auwerx, 1999;Kersten et al., 2000). A class of agents known as thiazolidinediones (TZDs), or glitazones, have been shown to modulate PPAR-␥, resulting in lower plas...

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 [13C8]‐evacetrapib as a tracer. Plasma samples collected through 168 h were analyzed for evacetrapib and [13C8]‐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 13C‐labeled IV microdose tracer at about 1/1000th 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.

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.