ABSTRACT
A recent clinical trial in patients with Mild Cognitive Impairment (MCI) found an increased rate of possible or probable Alzheimer's disease (AD) diagnoses in patients assigned to rofecoxib compared to placebo. This unexpected finding was difficult to interpret due to methodological issues and a lack of confirmation on secondary endpoints, as well as a lack of confirmation in trials in related populations. We performed additional post hoc analyses to explore explanations for the finding based on possible neuropathological, cardiovascular/cerebrovascular, or cognitive effects of rofecoxib. 1) Neuropathological hypothesis: Of the 189 incident cases of possible or probable AD, 154 were probable AD. In probable AD patients, the treatment hazard ratio was reduced compared to the primary analysis -- a concordant finding would have strengthened a conclusion that rofecoxib accelerated the underlying neuropathology of AD. The treatment hazard ratio was increased in the remaining 35 patients with less certain diagnoses, but there was no single predominant reason for the reduced certainty of diagnosis. 2) Cardiovascular hypothesis: Neither cardiovascular risk status nor mean arterial blood pressure had an overall effect on AD diagnosis or modified the treatment difference. 3) Cognitive side-effects hypothesis: The percentages of patients with non-specific NSAID-type central nervous system adverse events were similar between the treatment groups. In summary, the present analyses are limited by their post hoc nature but provided little support for any of the possible explanations explored. The significance of the observation that rofecoxib increased the rate of conversion from MCI to AD remains uncertain.
Subject(s)
Alzheimer Disease/prevention & control , Cognition Disorders/drug therapy , Cyclooxygenase 2 Inhibitors/therapeutic use , Lactones/therapeutic use , Sulfones/therapeutic use , Alzheimer Disease/diagnosis , Alzheimer Disease/etiology , Anti-Inflammatory Agents, Non-Steroidal/adverse effects , Anti-Inflammatory Agents, Non-Steroidal/therapeutic use , Cognition Disorders/complications , Cyclooxygenase 2 Inhibitors/adverse effects , Disease Progression , Double-Blind Method , Humans , Lactones/adverse effects , Proportional Hazards Models , Risk Assessment , Sulfones/adverse effects , Treatment FailureABSTRACT
Inflammatory mechanisms have been implicated in Alzheimer's disease (AD) and might be mediated via the COX-2 enzyme. Previous studies with the selective COX-2 inhibitors, rofecoxib and celecoxib, have shown that they do not alter the progression of AD. We conducted a double-blind study to investigate whether rofecoxib could delay a diagnosis of AD in patients with mild cognitive impairment (MCI), a group with an expected annual AD diagnosis rate of 10-15%. MCI patients > or =65 years were randomized to rofecoxib 25 mg (N=725) or placebo (N=732) daily for up to 4 years. The primary end point was the percentage of patients with a clinical diagnosis of AD. The estimated annual AD diagnosis rate was lower than the anticipated 10-15%: 6.4% in the rofecoxib group vs 4.5% in the placebo group (rofecoxib : placebo hazard ratio=1.46 (95% CI: 1.09, 1.94), p=0.011). Analyses of secondary end points, including measures of cognition (eg the cognitive subscale of the AD Assessment Scale (ADAS-Cog)) and global function (eg the Clinical Dementia Rating (CDR)), did not demonstrate differences between treatment groups. There was also no consistent evidence that rofecoxib differed from placebo in post hoc analyses comparing ADAS-Cog and CDR-sum of boxes scores in overlapping subgroups of patients who had Mini Mental State Exam scores of 24-26 in the present MCI study and in a previous AD treatment study with a similar design. The results from this MCI study did not support the hypothesis that rofecoxib would delay a diagnosis of AD. In conjunction with the lack of effects observed in previous AD studies, the findings suggest that inhibition of COX-2 is not a useful therapeutic approach in AD.
