L. Truyen

Although approaches to the prediction of drug-drug interactions (DDIs) arising via time-dependent inactivation have recently been developed, such approaches do not account for simple competitive inhibition or induction. Accordingly, these approaches do not provide accurate predictions of DDIs arising from simple competitive inhibition (e.g., ketoconazole) or induction of cytochromes P450 (e.g., phenytoin). In addition, methods that focus upon a single interaction mechanism are likely to yield misleading predictions in the face of mixed mechanisms (e.g., ritonavir). As such, we have developed a more comprehensive mathematical model that accounts for the simultaneous influences of competitive inhibition, time-dependent inactivation, and induction of CYP3A in both the liver and intestine to provide a net drug-drug interaction prediction in terms of area under the concentration-time curve ratio. This model provides a framework by which readily obtained in vitro values for competitive inhibition, time-dependent inactivation and induction for the precipitant compound as well as literature values for f_m and F_G for the object drug can be used to provide quantitative predictions of DDIs. Using this model, DDIs arising via inactivation (e.g., erythromycin) continue to be well predicted, whereas those arising via competitive inhibition (e.g., ketoconazole), induction (e.g., phenytoin), and mixed mechanisms (e.g., ritonavir) are also predicted within the ranges reported in the clinic. This comprehensive model quantitatively predicts clinical observations with reasonable accuracy and can be a valuable tool to evaluate candidate drugs and rationalize clinical DDIs.

MRI findings are increasingly used as outcome measures in therapeutic trials in MS. The discrepancy between the extent of the lesions on conventional T2 images and the clinical condition of the patient is one of the problems encountered in such studies. This clinical-radiological paradox prevents the use of MRI data as surrogate markers of disability in MS. A recent pilot study suggested a relationship between hypointense lesions on T1 MRI and disability. To assess in more detail the correlation of changes in hypointense lesion load on T1-weighted spin-echo MR images ("black holes") with changes in disability in MS, we studied 46 patients with clinically definite MS at baseline and after a median follow-up of 40 months. There was a significant correlation between baseline disability and hypointense lesion load (Spearman rank correlation coefficient [SRCC] = 0.46, p = 0.001). In secondary progressive patients, the rate of accumulation of these "black holes" was significantly related to progression rate (SRCC = 0.81, p < 0.0001). We speculate that the appearance of hypointense lesions is the MRI equivalent of a failure of remission. Overall, T1 lesion load measurements correlated better with clinical assessments than T2 lesion load measurements. Quantification of hypointense lesion load on T1-weighted spin-echo MRI helps to resolve the clinical-radiological paradox between disability and MRI and has the potential to be a surrogate marker of disability in MS.

OBJECTIVE: To assess the safety of galantamine in subjects with mild cognitive impairment (MCI), the ability of galantamine to benefit cognition and global functioning in subjects with MCI, and the ability of galantamine to delay conversion to dementia. METHODS: In two studies, 2,048 subjects, 990 in Study 1 and 1,058 in Study 2, with a Clinical Dementia Rating (CDR) = 0.5, CDR memory score > or =0.5, without dementia were randomized to double-blind galantamine (16-24 mg/day) or placebo for 24 months. Primary efficacy endpoint at month 24 was number (%) of subjects who converted from MCI to dementia (CDR > or = 1.0). RESULTS: There were no differences between galantamine and placebo in 24-month conversion rates (Study 1: 22.9% [galantamine] vs 22.6% [placebo], p = 0.146; Study 2: 25.4% [galantamine] vs 31.2% [placebo], p = 0.619). Mean CDR-sum of boxes declined less with galantamine than placebo at 12 and 24 months in Study 1 (p = 0.024 [12 months] and p = 0.028 [24 months]), but not in Study 2 (p = 0.662 [12 months] and p = 0.056 [24 months]). Digit Symbol Substitution Test scores improved with galantamine in Study 1 at 12 months and in Study 2 at 24 months (Study 1: p = 0.009 [month 12] and p = 0.079 [Month 24]; Study 2: p = 0.154 [month 12] and p = 0.020 [month 24]). The most frequently reported adverse event was nausea (galantamine, 29%; placebo, 10%). Serious AEs occurred in 19% of each group. Mortality of the cohort after retrospectively determining the status of subjects (98.3%) at 24 months was 1.4% (galantamine) and 0.3% (placebo); RR (95% CI), 1.70 (1.00, 2.90). CONCLUSIONS: Galantamine failed to significantly influence conversion to dementia. Galantamine was generally well tolerated. Whereas recorded mortality was greater in the galantamine group than in the placebo group in the original per-protocol assessment, a post hoc analysis of the cohort was consistent with no increased risk.

OBJECTIVES: To calculate age adjusted risks for multiple sclerosis in relatives of Flemish patients with multiple sclerosis. METHODS: Lifetime risks were calculated using the maximum likelihood approach. RESULTS: Vital information was obtained on 674 probands with multiple sclerosis in Flanders and a total of their 26225 first, second, and third degree relatives. Full medical information to allow documentation of multiple sclerosis status was available for 21351 (81.4%) relatives. The age adjusted risk for parents was 1.61 (SEM 0.35)%, for siblings 2.10 (SE 0.36)%, and for children 1.71 (SEM 0.70)%. For aunts and uncles, the risk was 0.66 (SEM 0.13)%. CONCLUSIONS: The risk for first degree relatives of patients with multiple sclerosis in Flanders is increased 10-fold to 12-fold; for second degree relatives, it is increased threefold. This information can be used for risk counselling in families and provides additional support for the role of more than one locus contributing to the susceptibility of multiple sclerosis.