Comparison of Therapeutic Strategies With Cholinesterase Inhibitors (SOS TRIAL)

Cholinesterase inhibitors (CI) remain the only drugs with a recognized efficacy in mild to moderate Alzheimer's disease (AD) in spite of enormous research efforts. However, these drugs presented as "symptomatic treatment" of AD are considered as having only a weak effect on the course of AD. The reimbursement of these drugs is regularly challenged due to the lack of evidence for the impact of these drugs on milestones stages of AD evolution (survival without severe dementia, restriction in Basic Activities of Daily Living - BADL) and on major consequences in public health (hospitalization and institutionalization). The great majority of previous randomized controlled trials conducted with CI have had a too short duration and the end points were limited to cognition (ADAS Cog scale), IADL (Instrumental Activities of Daily Living) function and Global Impression of Change. New evidences from the DOMINO trial (1) conducted in UK, independently of the pharmaceutical industry, showed that the true effect of CI might be more to avoid or to delay the cognitive or functional decline in AD than to improve patients; the institutionalisation (2) was also delayed. However, this trial was conducted in patients with moderate to severe AD, and the interest of the drugs at the mild to moderate stage remains questionable. The investigators have shown that a good surrogate marker of survival without severe dementia would be an increase of ADAS Cog scale of more than six points (3). A post hoc reanalysis of the pivotal RCT with two CI showed that in mild to moderate patients, CI was associated with a 15% decrease of patients with a deterioration of ADAS-Cog of more than six points in six months. Thus at the beginning of dementia the real effect of CI might be more of delaying the cognitive and functional decline, than to improve the patients. The main objective of the SOS trial is to demonstrate that the benefit of CI at the early phase of dementia is the same as at the later phase.