The  US Food and Drug Administration has issued a proposal which it claims is designed to assist companies develop new treatments for early stages of Alzheimer’s disease, before the onset of noticeable dementia.

The draft guidance explains the agency's current thinking about the way researchers can select patients with early Alzheimer’s, or those who are at risk of developing the disease, for clinical trials. In recent years, researchers have tried to find ways to identify these patients using biomarkers and "tried to develop sensitive clinical measures that can detect subtle mental decline", the FDA notes.

For drugs designed to treat overt dementia, the FDA requires that treatments not only show an effect on abnormal thinking, but also how well patients function. However, the agency acknowledges that because patients with early Alzheimer’s "have little-to-no impairment of global functioning, it is difficult to assess changes in function in these patients". This "can make it difficult to determine if a given treatment’s effect is clinically important".

Russell Katz, director of the division of neurology products in the agency's Center for Drug Evaluation and Research, said that "the scientific community and the FDA believe that it is critical to identify and study patients with very early Alzheimer’s disease before there is too much irreversible injury to the brain". He added that "it is in this population that most researchers believe that new drugs have the best chance of providing meaningful benefit to patients".

The FDA has put up the draft guidance for public comment for 60 days.