FDA position statement "Early Alzheimer's disease: Developing drugs for treatment, Guidance for Industry".

Despite billions of dollars invested in clinical trials to develop novel therapeutics for Alzheimer's disease, no approved treatments have been developed in the past 15 years. In that span, new classes of drugs have been developed and tested, including monoclonal antibodies, γ-secretase modulators, γ-secretase inhibitors, BACE inhibitors, RAGE inhibitors, nicotinic agonists, 5HT6 antagonists, and others. The one constant for all of these clinical trials programs is the use of the ADAS-cog as the primary scale to determine efficacy. The question that needs to be considered is whether it is the target engagement of the drug or the clinical trial measure testing the efficacy. The FDA put out a new position statement in 2018 informing the field on possible considerations for demonstrating efficacy to open the path for approval. Here, we propose and comment on a variety of approaches that are alternatives to the ADAS for FDA-specified stage 3 and 4 Alzheimer's disease. These novel outcomes are being validated in current clinical trials and could be used as efficacy measures moving forward.