IntroductionThe aim of the study was to assess the clinical efficacy, safety, and disease-modification effects of tramiprosate (homotaurine, ALZHEMEDTM) in mild-to-moderate Alzheimer’s disease (AD).Material and methodsDouble-blind, placebo-controlled, randomized trial in 67 clinical centres across North America. Patients aged ≥ 50 years, with mild-to-moderate AD (Mini-Mental State Examination score between 16 and 26) and on stable doses of cholinesterase inhibitors, alone or with memantine. Intervention: 78-week treatment with placebo, tramiprosate 100 mg or tramiprosate 150 mg BID. Measurements: Alzheimer Disease Assessment Scale – cognitive subscale (ADAS-cog) and Clinical Dementia Rating – Sum of Boxes (CDR-SB) assessments were performed at baseline and every 13 weeks. Baseline and 78-week magnetic resonance imaging (MRI) hippocampus volume (HV) measurements were conducted in a subgroup of patients.
ResultsA total of 1,052 patients were enrolled and 790 (75.1%) completed the 78-week trial. Patient discontinuation and reasons for withdrawal were similar across groups. Planned analyses did not reveal statistically significant between-group differences. Lack of adequate statistical validity of the planned analysis models led to the development of revised predictive models. These adjusted models showed a trend toward a treatment effect for ADAS-cog (P = 0.098) and indicated significantly less HV loss for tramiprosate 100 mg (P = 0.035) and 150 mg (P = 0.009) compared to placebo. The incidence of adverse events was similar across treatment groups.
ConclusionsThe primary planned analyses did not show a significant treatment effect, but were confounded by unexplained variance. Post-hoc analyses showed a significant treatment-related reduction in HV loss. However, there was only a trend towards slowing of decline on the ADAS-cog and no slowing of decline on the CDR-SB. These results must be interpreted in consideration of the limitations of clinical and disease-modification outcome measures and their relationship, the heterogeneity of the disease and the impact of confounding demographic and clinical variables.
Exploratory analysis of the vMRI subgroup suggests that tramiprosate slows hippocampal atrophy, and reveals some evidence of a beneficial effect on cognition. The clinical validity of the vMRI biomarker is discussed.
Results section, page 554, second column, the P values for the change in ADAS-cog scores are given incorrectly. The correct sentence should read as follows (revisions in bold): "Results for the change in ADAS-cog scores showed a marginally significant overall treatment effect (P = 0.091) and a nonsignificant interaction of treatment with time (P = 0.883)." These corrections have no impact on the conclusions of the study outcomes. The authors regret the errors.
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