Clinical-Genetic Associations in the Prospective Huntington at Risk Observational Study (PHAROS): Implications for Clinical Trials.

IMPORTANCE: Identifying measures that are associated with the cytosine-adenine-guanine (CAG) expansion in individuals before diagnosis of Huntington disease (HD) has implications for designing clinical trials. OBJECTIVE: To identify the earliest features associated with the motor diagnosis of HD in the Prospective Huntington at Risk Observational Study (PHAROS). DESIGN, SETTING, AND PARTICIPANTS: A prospective, multicenter, longitudinal cohort study was conducted at 43 US and Canadian Huntington Study Group research sites from July 9, 1999, through December 17, 2009. Participants included 983 unaffected adults at risk for HD who had chosen to remain unaware of their mutation status. Baseline comparability between CAG expansion (≥37 repeats) and nonexpansion (<37 repeats) groups was assessed. All participants and investigators were blinded to individual CAG analysis. A repeated-measures analysis adjusting for age and sex was used to assess the divergence of the linear trend between the expanded and nonexpanded groups. Data were analyzed from April 27, 2010, to September 3, 2013. EXPOSURE: Huntington disease mutation status in individuals with CAG expansion vs without CAG expansion. MAIN OUTCOMES AND MEASURES: Unified Huntington's Disease Rating Scale motor (score range, 0-124; higher scores indicate greater impairment), cognitive (symbol digits modality is the total number of correct responses in 90 seconds; lower scores indicate greater impairment), behavioral (score range, 0-176; higher scores indicate greater behavioral symptoms), and functional (Total Functional Capacity score range, 0-13; lower scores indicate reduced functional ability) domains were assessed at baseline and every 9 months up to a maximum of 10 years. RESULTS: Among the 983 research participants at risk for HD in the longitudinal cohort, 345 (35.1%) carried the CAG expansion and 638 (64.9%) did not. The mean (SD) duration of follow-up was 5.8 (3.0) years. At baseline, participants with expansions had more impaired motor (3.0 [4.2] vs 1.9 [2.8]; P < .001), cognitive (P < .05 for all measures except Verbal Fluency, P = .52), and behavioral domain scores (9.4 [11.4] vs 6.5 [8.5]; P < .001) but not significantly different measures of functional capacity (12.9 [0.3] vs 13.0 [0.2]; P = .23). With findings reported as mean slope (95% CI), in the longitudinal analyses, participants with CAG expansions showed significant worsening in motor (0.84 [0.73 to 0.95] vs 0.03 [-0.05 to 0.11]), cognitive (-0.54 [-0.67 to -0.40] vs 0.22 [0.12 to 0.32]), and functional (-0.08 [-0.09 to -0.06] vs -0.01 [-0.02 to 0]) measures compared with those without expansion (P < .001 for all); behavioral domain scores did not diverge significantly between groups. CONCLUSIONS AND RELEVANCE: Using these prospectively accrued clinical data, relatively large treatment effects would be required to mount a randomized, placebo-controlled clinical trial involving premanifest HD individuals who carry the CAG expansion.

Levels of the light subunit of neurofilament triplet protein in cerebrospinal fluid in Huntington's disease.

BACKGROUND: Neurofilaments are major structural elements of neuronal cells. The light subunit of neurofilament triplet protein (NFL) has been shown to be increased in several neurological diseases (e.g. vascular, infectious, neurodegenerative), indicating axonal damage. METHODS: In this study we analyzed the NFL levels in all (N=35) available cerebrospinal fluid (CSF) samples from a clinical trial in Huntington's disease (HD) and compared them to age and gender matched controls. RESULTS: The CSF-NFL levels were significantly higher in HD subjects compared with age and genders matched controls, and were correlated with scores on the Unified Huntington's Disease Rating Scale Total Functional Capacity assessment. The potential of CSF-NFL levels as a disease activity marker in HD needs to be further investigated.

The relationship between CAG repeat length and clinical progression in Huntington's disease.

The objective of this study was to examine the relationship between CAG repeat length (CAGn) and clinical progression in patients with Huntington's disease (HD). There are conflicting reports about the relationship between CAGn and clinical progression of HD. We conducted an analysis of data from the Coenzyme Q10 and Remacemide Evaluation in Huntington's Disease (CARE-HD) clinical trial. We modeled progression over 30 months on the Unified Huntington's Disease Rating Scale (UHDRS) and supplemental neuropsychological and behavioral tests using multiple linear regression. Mean subject age was 47.9 +/- 10.5 years and mean CAGn was 45.0 +/- 4.1. Multiple linear regression revealed statistically significant associations between CAGn and worsening on several motor, cognitive, and functional outcomes, but not behavioral outcomes. Many effects were clinically important; 10 additional CAG repeats were associated with an 81% increase in progression on the Independence Scale. These associations were not observed in the absence of age adjustment. Age at the time of assessment confounds the association between CAGn and progression. Adjusting for age shows that longer CAGn is associated with greater clinical progression of HD. This finding may account for the variable results from previous studies examining CAGn and progression. Adjusting for CAGn may be important for clinical trials.

Impact of pramipexole on the onset of levodopa-related dyskinesias.

Dyskinesias are a major complication of dopaminergic therapy in the long-term treatment of Parkinson's disease. In the CALM-PD trial, subjects were initially randomized to levodopa or pramipexole and could later add levodopa if needed. After adjusting for disease duration and daily levodopa dosage, the incidence of dyskinesias after initiating levodopa was not significantly different among subjects initially randomized to levodopa and those initially randomized to pramipexole.

Malignant melanoma in early Parkinson's disease: the DATATOP trial.

The available epidemiological data on the incidence of malignant melanoma in Parkinson's disease are contradictory. The role of levodopa therapy in this context has been debated. We identified all known cases of malignant melanoma (N = 5) in the DATATOP clinical trial cohort and compared that to published expected values (N = 1.5) for a standard healthy population. The standardized event ratio was 3.3 (95% confidence interval, 1.1-7.8), indicating that incidence of malignant melanoma was higher than expected. We found no association between levodopa therapy and the incidence of melanoma.