Joseph Giuliano

Pharmacokinetics of memantine in rats and mice.

To evaluate the potential of memantine as a therapeutic agent for Huntington’s disease (HD) we have undertaken a series of in vitro, ex vivo and whole animal studies to characterize its pharmacokinetics (PK) and pharmacodynamics (PD) in rats and mice. Results from these studies will enable determination of memantine exposures needed to engage the related functional PD marker and help predict the dose regimen for clinical trials to test its proposed mechanism of action; the selective blockade of extrasynaptic, but not synaptic, NMDA receptors. The studies reported here describe the PK of memantine in rats and mice at low (1 mg/kg) and high (10 mg/kg) doses. Our studies indicate that the clearance mechanisms of memantine in rats and mice are different from those in human, and that clearance needs to be taken into account when extrapolating to the human. In rats only, there is a significant metabolic contribution to memantine clearance at lower dose levels. While memantine is primarily cleared renally in all three species, the proportion of total systemic clearance above the glomerular filtration rate (GFR) is much higher in rats and mice (~13, 4.5, and 1.4 times higher than GFR in rats, mice, and humans, respectively), suggesting that the contribution of active transport to memantine elimination in rats and mice is more significant than in the human. In rats and mice, memantine had a short half-life (<4 h) and steep Cmax/Cmin ratios (>100). In the human, the half-life of memantine was reported to be very long (60-80 h) with a Cmax/Cmin ratio at steady state concentrations of ~1.5. A small change in the clearance of memantine - for example due to renal impairment or competition for the elimination pathway with a co-administered drug - will likely affect exposure and, therefore, the selectivity of memantine on NMDA receptors . The PK differences observed between these species demonstrate that the PK in mice and rats cannot be directly extrapolated to the human. Further, the relationship between the plasma concentration (and therefore dose) needed to elicit a mechanism-related in vivo functional effect (PD readout) while maintaining the selectivity of the extrasynaptic blockade of the NMDA receptors needs to be established before clinical trials can be appropriately planned.

An item response analysis of the motor and behavioral subscales of the unified Huntington's disease rating scale in huntington disease gene expansion carriers.

Although the Unified Huntingtons Disease Rating Scale (UHDRS) is widely used in the assessment of Huntington disease (HD), the ability of individual items to discriminate individual differences in motor or behavioral manifestations has not been extensively studied in HD gene expansion carriers without a motor‐defined clinical diagnosis (ie, prodromal‐HD or prHD). To elucidate the relationship between scores on individual motor and behavioral UHDRS items and total score for each subscale, a nonparametric item response analysis was performed on retrospective data from 2 multicenter longitudinal studies. Motor and behavioral assessments were supplied for 737 prHD individuals with data from 2114 visits (PREDICT‐HD) and 686 HD individuals with data from 1482 visits (REGISTRY). Option characteristic curves were generated for UHDRS subscale items in relation to their subscale score. In prHD, overall severity of motor signs was low, and participants had scores of 2 or above on very few items. In HD, motor items that assessed ocular pursuit, saccade initiation, finger tapping, tandem walking, and to a lesser extent, saccade velocity, dysarthria, tongue protrusion, pronation/supination, Luria, bradykinesia, choreas, gait, and balance on the retropulsion test were found to discriminate individual differences across a broad range of motor severity. In prHD, depressed mood, anxiety, and irritable behavior demonstrated good discriminative properties. In HD, depressed mood demonstrated a good relationship with the overall behavioral score. These data suggest that at least some UHDRS items appear to have utility across a broad range of severity, although many items demonstrate problematic features.

Data Analytics from Enroll-HD, a Global Clinical Research Platform for Huntington's Disease

The study of complex neurodegenerative diseases is moving away from hypothesis‐driven biological methods toward large scale multimodal approaches, requiring standardized collaborative efforts. Enroll‐HD exemplifies such an integrated clinical research platform, designed and implemented to meet the research and clinical needs of Huntingtons disease (HD). The aim of this study was to describe the unique organization of Enroll‐HD and report baseline data analyses of its core study.

Assessment of Motor Symptoms and Functional Impact in Prodromal and Early Huntington Disease

The Functional Rating Scale Taskforce for pre-Huntington Disease (FuRST-pHD) is a multinational, multidisciplinary initiative with the goal of developing a data-driven, comprehensive, psychometrically sound, rating scale for assessing symptoms and functional ability in prodromal and early Huntington disease (HD) gene expansion carriers. The process involves input from numerous sources to identify relevant symptom domains, including HD individuals, caregivers, and experts from a variety of fields, as well as knowledge gained from the analysis of data from ongoing large-scale studies in HD using existing clinical scales. This is an iterative process in which an ongoing series of field tests in prodromal (prHD) and early HD individuals provides the team with data on which to make decisions regarding which questions should undergo further development or testing and which should be excluded. We report here the development and assessment of the first iteration of interview questions aimed to assess functional impact of motor manifestations in prHD and early HD individuals.

The direct medical costs of Huntington’s disease by stage. A retrospective commercial and Medicaid claims data analysis

Abstract Objective: This study quantified the direct healthcare costs and major cost drivers among patients with Huntington’s disease (HD), by disease stage in commercial and Medicaid databases. Methods: This retrospective database analysis used healthcare utilization/cost data for HD patients (ICD-9-CM 333.4) from Thomson Reuters’ MarketScan Commercial and Medicaid 2002–2009 databases. Patients were classified by disease stage (Early/Middle/Late) by a hierarchical assessment of markers of disease severity, confirmed by literature review and key opinion leader input. Costs were measured over the follow-up time of each patient with total costs per patient per stage annualized using a patient-year cost approach. Results: Among 1272 HD patients, the mean age was similar in commercial (752 patients) and Medicaid (520 patients) populations (48.5 years (SD = 13.3) and 49.3 years (SD = 17.2), respectively). Commercial patients were evenly distributed by stage (30.5%/35.5%/34.0%; Early/Middle/Late). However, most (74.0%) Medicaid HD patients were classified as Late stage. The mean total annualized cost per patient increased by stage (commercial:

M02 Enroll-HD: a prospective observational study in a global huntington's disease cohort

4947 (SD = 

L07 The functional rating taskforce for pre-huntington's disease: development of the furst-21 scale

6040)–

F08 The functional rating taskforce for pre-huntington's disease: results so far

22,582 (SD = 

F09 Progression of motor symptoms prior to diagnosis in HD-gene carriers

39,028); Medicaid:

J13 Prescription usage for treatment of irritability, perseverative behaviors, and chorea in huntington's disease

3257 (SD =