Marissa Dockendorf

The BACE1 inhibitor verubecestat (MK-8931) reduces CNS β-amyloid in animal models and in Alzheimer’s disease patients

The BACE1 inhibitor verubecestat safely reduces β-amyloid deposition in rats, monkeys, healthy human subjects, and patients with Alzheimer’s disease. Getting to first BACE The discovery of BACE1 inhibitors that reduce β-amyloid peptides in Alzheimer’s disease (AD) patients has been an encouraging development in the quest for a disease-modifying therapy. Kennedy and colleagues now report the discovery of verubecestat, a structurally unique, orally bioavailable small molecule that potently inhibits brain BACE1 activity resulting in a reduction in Aβ peptides in the cerebrospinal fluid of animals, healthy volunteers, and AD patients. No dose-limiting toxicities were observed in chronic animal toxicology studies or in phase 1 human studies, thus reducing safety concerns raised by previous reports of BACE inhibitors and BACE1 knockout mice. β-Amyloid (Aβ) peptides are thought to be critically involved in the etiology of Alzheimer’s disease (AD). The aspartyl protease β-site amyloid precursor protein cleaving enzyme 1 (BACE1) is required for the production of Aβ, and BACE1 inhibition is thus an attractive target for the treatment of AD. We show that verubecestat (MK-8931) is a potent, selective, structurally unique BACE1 inhibitor that reduced plasma, cerebrospinal fluid (CSF), and brain concentrations of Aβ40, Aβ42, and sAPPβ (a direct product of BACE1 enzymatic activity) after acute and chronic administration to rats and monkeys. Chronic treatment of rats and monkeys with verubecestat achieved exposures >40-fold higher than those being tested in clinical trials in AD patients yet did not elicit many of the adverse effects previously attributed to BACE inhibition, such as reduced nerve myelination, neurodegeneration, altered glucose homeostasis, or hepatotoxicity. Fur hypopigmentation was observed in rabbits and mice but not in monkeys. Single and multiple doses were generally well tolerated and produced reductions in Aβ40, Aβ42, and sAPPβ in the CSF of both healthy human subjects and AD patients. The human data were fit to an amyloid pathway model that provided insight into the Aβ pools affected by BACE1 inhibition and guided the choice of doses for subsequent clinical trials.

An Integrated Strategy for Implementation of Dried Blood Spots in Clinical Development Programs

Dried blood spot (DBS) sample collection has gained increased interest across the pharmaceutical industry as a potential alternative to plasma for pharmacokinetic (PK) evaluations. However, regulatory guidelines and examples of late-stage clinical trial applications in the literature are lacking. This paper communicates Merck’s strategy for the implementation of DBS exemplified by experience on a late-stage program (MK-8931). In this program, DBS was proposed as the sole matrix for phase 3 studies to decrease logistical burden in an aging target patient population (Alzheimer’s disease). In vitro and bioanalytical tests demonstrated initial method feasibility and suitability for further evaluations in the clinic. An in vivo dataset was developed initially in healthy subjects (phase 1 study) and then in patients (phase 2/3 study) to establish a quantitative relationship between the blood and plasma concentrations (bridging dataset) using descriptive and population PK analyses. This allowed for PK conclusions to be seamlessly drawn across the clinical program without impact from the choice of matrix. This integrated information package (in vitro, bioanalytical and clinical) was presented to major regulatory agencies (FDA and EMA) for regulatory input. Based on this package, regulatory concurrence was gained on accepting DBS as the sole matrix in late-stage clinical trials.

Safety and pharmacokinetics of the novel BACE inhibitor MK-8931 in healthy subjects following single- and Multiple-Dose administration

Background:Alzheimer’s disease (AD) is a common, debilitating neurodegenerative disorder afflicting the aging population. Synaptic accumulation of Aß-protein oligomers and tau might be responsible for the neurological damage in AD. Thus, special interest has emerged in developing treatments that reduce the formation or facilitate the clearance of these oligomers. Utilizing molecular modeling and structure based design techniques we generated a series of novel organic heterocyclic compounds that are capable of recognizing the aggregated Aß-protein molecule and promoting clearance. Using cell-free and cell-based assays, a compound denominated NPT-400 with activity in the high nanomolar range was identified for pharmacokinetic (PK) and preliminary efficacy studies in APP transgenic (tg) mice. Methods: The mThy1-hAPP751 transgenic mouse was utilized for efficacy studies. This mouse combines the Swedish (K670M/N671L) and London (V717I) APPmutations, and these animals develop AD-like neuropathology and behavioral deficits starting at 3-4 months of age. Female non-tg and tg mice (w5 mo of age) received a single injection of vehicle or NPT-400-3 (IP, 10 mg/kg) three times per week for 6.5 weeks. Behavioral assessments were conducted during week 4 of treatment including locomotor activity and water maze. At the completion of treatment, brains were hemisected and tissue sections were processed for immunolabeling and confocal analysis, and homogenates were analyzed for levels of Abeta-protein by ELISA and immunoblot. For PK studies, wildtype C57Bl6 mice received IVor PO NPT-400-3 compound at 10 mg/kg and blood and plasma levels were analyzed at 0-24 hrs. Results: Treatment with NPT-400-3 resulted in a statistically significant normalization of locomotor activity accompanied by amelioration of the synaptic and dendritic pathology in the neocortex and hippocampus. By immunoblot and ELISA the levels of monomeric and oligomeric Aß-protein were statistically significantly reduced in the brains of the APP tg mice. PK studies showed that NPT400-3 is stable in plasma, is orally bioavailable and penetrates the brain with a B/P ratio of 0.8. Conclusions:NPT-400-3 is an orally bioavailable, brain penetrating Aß-protein stabilizing organic compound that reduces the accumulation of Aß-protein oligomers and ameliorates behavioral deficits and neuropathology in APP tg mice without overt adverse effects.

A study to evaluate the pharmacokinetics and pharmacodynamics of single and multiple oral doses of the novel BACE inhibitor MK-8931 in Japanese subjects

loid in the cerebral cortex (P 1⁄4 0.0001) and corpus callosum (P 1⁄4 0.001). In addition, the TBI rats treated with estrone had reduced cortical lesion volume and cortical levels of TUNEL + staining (w80%). Conclusions: Estrone given acutely after brain injury decreases cortical neuronal cell death and white matter injury. These results suggest that other estrogens in addition to estradiol may afford individuals protection secondary brain injury after TBI.

Population PK Analyses of Ubrogepant (MK‐1602), a CGRP Receptor Antagonist: Enriching In‐Clinic Plasma PK Sampling With Outpatient Dried Blood Spot Sampling

Merck & Co., Inc. (Kenilworth, New Jersey) has recently published an integrated strategy for implementation of dried blood spots (DBS) in late‐stage trials for population pharmacokinetic (PK) modeling. We applied this strategy for another late‐stage clinical program: ubrogepant (MK‐1602), a novel oral calcitonin gene‐related peptide receptor antagonist for acute treatment of migraine. At the time of implementation, ubrogepant was entering phase 2 development. DBS was implemented to acquire PK information proximal to an acute migraine event to enable exposure–response modeling. The clinical endpoint was a spontaneous event, which generally occurs outside a clinic visit. Thus, an innovative feature of this trial was facilitating DBS in an outpatient setting. In vitro and bioanalytical tests established initial method feasibility and suitability for further evaluations in the clinic. A quantitative relationship was developed between blood and plasma concentrations from concurrently collected samples in a phase 1 (healthy subjects) and phase 2 (target patient population) study using graphical and population PK approaches. This integrated information was presented to the Food and Drug Administration for regulatory input. Following regulatory concurrence, DBS was poised for use in further clinical studies. Population PK modeling was used to dissect sources of variability contributing to DBS collection in the outpatient setting. What has been learned from this program has informed the broader integrated strategy of Merck & Co., Inc. (Kenilworth, NJ) for DBS implementation in clinical trials and research to improve the precision of PK data collected in an outpatient setting.

Development and application of a mathematical model of modulation of cerebrospinal fluid Aβ40 after treatment with gamma- and beta-secretase inhibitors

Background:A mathematical model representation of key amyloid pathway physiology to describe A b 40 modulation in CSF was developed to: (1) quantify clinical drug potency of g-secretase (GS) and b -secretase (BACE1) inhibitors; (2) enable benchmarking across compounds; (3) facilitate dose selection for efficacy trials. Methods: Lumbar CSF A b 40 concentration data in healthy adults treated with placebo; GS inhibitors MK-0752 or semagacestat (from literature); or BACE inhibitor MK8931 were available. Model-predicted drug brain concentrations were used as driver for CSFA b 40 modulation. An Emax relationship described inhibition of A b 40 production and a distribution delay between brain and lumbar CSFA b 40 was incorporated. An additive baseline drift model informed by study-specific placebo data allowed for drift correction. Data were fit using non-linear mixed effects modeling and model performance was qualified. This model was combined with population PK models to predicted dose response profiles for brain and CSFA b 40 inhibition. Trial performance predictions were made taking into account AD population demographics and knowledge on non-compliance. Results: An E max inhibition model combined with delay compartments best described the CSF A b 40 response upon inhibition of GS or BACE. Maximum inhibition (E max) estimates were 0.87, 0.86, 0.96 and for plasma concentration at 50% of maximum (EC 50) were 933 ng.mL -1, 6250 ng.mL -1, 10.2 ng.mL -1 for semagacestat, MK-0752, and MK-8931, respectively. Dose response profiles demonstrated greater potency and achievable CSFA b 40 suppression with MK-8931 compared to other compounds at clinically feasible doses. CSF A b 40 reductions between 50-75%, and between 75-100% from baseline were predicted to be achieved in 90% of the patients at doses of 12 and 40 mg MK-8931, respectively. Conclusions: CSF A b 40 response following placebo and GS or BACE inhibition were characterized by a common model framework. Comparative analysis among compounds suggests that semagacestat produces only limited (<11%) inhibition of Ab production. MK-8931 showed superior potency in the expected therapeutic dose range resulting in almost full suppression of CSFA b 40. Simulations indicate that 12 and 40 mgMK-8931 inhibit Ab production by>50% and >75%, respectively, suggesting that clinical trials in AD with MK8931 may provide a more robust test of the amyloid hypothesis, compared to semagacestat.

Leveraging model-informed approaches for drug discovery and development in the cardiovascular space

Cardiovascular disease remains a significant global health burden, and development of cardiovascular drugs in the current regulatory environment often demands large and expensive cardiovascular outcome trials. Thus, the use of quantitative pharmacometric approaches which can help enable early Go/No Go decision making, ensure appropriate dose selection, and increase the likelihood of successful clinical trials, have become increasingly important to help reduce the risk of failed cardiovascular outcomes studies. In addition, cardiovascular safety is an important consideration for many drug development programs, whether or not the drug is designed to treat cardiovascular disease; modeling and simulation approaches also have utility in assessing risk in this area. Herein, examples of modeling and simulation applied at various stages of drug development, spanning from the discovery stage through late-stage clinical development, for cardiovascular programs are presented. Examples of how modeling approaches have been utilized in early development programs across various therapeutic areas to help inform strategies to mitigate the risk of cardiovascular-related adverse events, such as QTc prolongation and changes in blood pressure, are also presented. These examples demonstrate how more informed drug development decisions can be enabled by modeling and simulation approaches in the cardiovascular area.

Leveraging Digital Health Technologies and Outpatient Sampling in Clinical Drug Development: A Phase I Exploratory Study

Merck & Co, Inc (Kenilworth, NJ) is investing in approaches to enrich clinical trial data and augment decision making through use of digital health technologies, outpatient sampling, and real‐time data access. As part of this strategy, a phase I study was conducted to explore a few technologies of interest. In this fixed‐sequence two‐period trial, 16 healthy subjects were administered 50‐mg once‐daily sitagliptin packaged in a bottle that electronically captured the date and time study medication was dispensed (period 1) and in a traditional pharmacy bottle (period 2). Dried blood spot samples were collected for sitagliptin concentration analysis on select study days, both in clinic and at home, with collection time recorded using an electronic diary in period 1 and by clinic staff in period 2. Study results demonstrated the feasibility and subject acceptance of collecting digital adherence data and outpatient dried blood spot samples in clinical trials and highlighted areas for future improvements.