Early human trials in the assessment of cognition activators

The assessment of cognition enhancers in the clinic is a broad topic that can be addressed from both academic/theoretical and therapeutic/drug development perspectives. The most important first step is to decide which perspective one is employing and to clearly specify, a priori, the goal of any intended study. Since the therapeutic benefit of cognition enhancers is not apparent until after many weeks of exposure, it is virtually impossible to demonstrate efficacy in early, short-duration Phase 2 trials. It is possible, however, to gain some knowledge of the doses that effect CNS, rCBF, PET etc. in either normal volunteers or the population of interest. However, these results should not be interpreted as evidence for, or lack of, efficacy. Recently, there has been growing interest in the reversal of scopolamine- or benzodiazepine-induced memory deficits in humans. A major problem is the potential for overinterpretation of the results of such studies. From a drug development approach, it is necessary to utilize larger numbers of subjects and longer-term studies. Specification of the indication should be as precise as possible and the outcome measures should accurately reflect both the current state of the patient and the course of the disease. The absence of normative and longitudinal data on such measures is a hurdle that is only now being overcome. Such data provide a scientific basis for the determination of the types of design and sample sizes that give adequate power to thoroughly assess new cognition enhancers.