This article summarizes how biochemical markers may aid in the development of novel treatments that interfere with fundamental pathogenic processes in Alzheimer's disease. Details are given on the potential use of biomarkers in Alzheimer's disease clinical trials as additional inclusion criteria to enrich study populations with participants who really suffer from the disease, as a means to stratify study participants into meaningful subgroups that may benefit differently from the treatment, and as tools to detect desired biochemical effects and undesired side effects of the drug.