On February 5, 2013, FDA announced the availability of Draft Guidance relating to the development of drugs for the treatment of early stage Alzheimer's disease. The Draft Guidance, titled, "Alzheimer's Disease: Developing Drugs for the Treatment of Early Stage Disease" addresses: (1) diagnostic criteria for early stage Alzheimer's disease; (2) appropriate clinical outcome measures; and (3) ways to demonstrate disease modification. Addressing these issues in early stage Alzheimer's disease poses unique difficulties, because patients may have little to no impairment of global functioning. FDA is seeking public comment on the Draft Guidance within sixty days.
The Draft Guidance provides FDA's current thinking on useful diagnostic criteria for early Alzheimer's disease. FDA cited useful research in developing diagnostic criteria, such as the research criteria for prodromal Alzheimer's disease and preclinical Alzheimer's disease. Specifically, FDA also cited as useful efforts by the research community to incorporate biomarkers into the diagnostic criteria. FDA concluded that, "we support the concept of enriching trial populations with patients most likely to progress to more overt dementia, using both clinical biomarker-based criteria." FDA also indicated, however, that FDA could not formally endorse any specific diagnostic framework, because more work was necessary to assess the specificity and sensitivity of these criteria, as well as the validation of these methodologies.
The Draft Guidance also provides FDA's current thinking on ways to establish clinical efficacy in trials involving patients suffering from early stage Alzheimer's disease. While FDA requires a co-primary outcome measure to demonstrate efficacy on both cognitive and functional levels for clinical trials on the dementia stage of Alzheimer's disease, in the draft guidance, FDA acknowledged that these endpoints may be impractical for patients suffering from early stage disease. Therefore, FDA indicated that for early stage disease "clear evidence of an effect on delaying cognitive impairment may provide sufficient evidence of effectiveness."