Fabry disease is a lysosomal storage disorder caused by a deficiency of the lysosomal enzyme ␣-galactosidase A (␣-gal A). This enzymatic defect results in the accumulation of the glycosphingolipid globotriaosylceramide (Gb 3; also referred to as ceramidetrihexoside) throughout the body. To investigate the effects of purified ␣-gal A, 10 patients with Fabry disease received a single i.v. infusion of one of five escalating dose levels of the enzyme. The objectives of this study were: (i) to evaluate the safety of administered ␣-gal A, (ii) to assess the pharmacokinetics of i.v.-administered ␣-gal A in plasma and liver, and (iii) to determine the effect of this replacement enzyme on hepatic, urine sediment and plasma concentrations of Gb3. ␣-Gal A infusions were well tolerated in all patients. Immunohistochemical staining of liver tissue approximately 2 days after enzyme infusion identified ␣-gal A in several cell types, including sinusoidal endothelial cells, Kupffer cells, and hepatocytes, suggesting diffuse uptake via the mannose 6-phosphate receptor. The tissue half-life in the liver was greater than 24 hr. After the single dose of ␣-gal A, nine of the 10 patients had significantly reduced Gb3 levels both in the liver and shed renal tubular epithelial cells in the urine sediment. These data demonstrate that single infusions of ␣-gal A prepared from transfected human fibroblasts are both safe and biochemically active in patients with Fabry disease. The degree of substrate reduction seen in the study is potentially clinically significant in view of the fact that Gb 3 burden in Fabry patients increases gradually over decades. Taken together, these results suggest that enzyme replacement is likely to be an effective therapy for patients with this metabolic disorder.
These findings provide a predictable outcome measure to assess the effect of molecular interventions on the cerebrovascular circulation in Fabry disease.
Background
Cognitive impairment is common in Parkinson’s disease (PD). There is a critical need for a brief, standard cognitive screening measure for use in PD trials whose primary focus is not on cognition.
Methods
The Parkinson Study Group (PSG) Cognitive/Psychiatric Working Group formed a Task Force to make recommendations for a cognitive scale that could screen for dementia and mild cognitive impairment in clinical trials of PD where cognition is not the primary outcome. This Task Force conducted a systematic literature search for cognitive assessments previously used in a PD population. Scales were then evaluated for their appropriateness to screen for cognitive deficits in clinical trials, including brief administration time (<15 minutes), assessment of the major cognitive domains, and potential to detect subtle cognitive impairment in PD.
Results
Five scales of global cognition met the predetermined screening criteria and were considered for review. Based on the Task Force’s evaluation criteria the Montreal Cognitive Assessment (MoCA), appeared to be the most suitable measure.
Conclusions
This Task Force recommends consideration of the MoCA as a minimum cognitive screening measure in clinical trials of PD where cognitive performance is not the primary outcome measure. The MoCA still requires further study of its diagnostic utility in PD populations but appears to be the most appropriate measure among the currently available brief cognitive assessments. Widespread adoption of a single instrument such as the MoCA in clinical trials can improve comparability between research studies on PD.
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