Another promising drug that reached human clinical testing stimulated production of nerve growth factors, proteins that regulate nerve cell maturation, survival, and repair. Nerve growth factors are an active area of research in stroke, spinal cord injury, and other nerve-damaging conditions as well as in Alzheimer’s disease.

Memantine, an Alzheimer drug already approved in Germany that recently won preliminary approval in the rest of the European Union, is now under development in the United States where it has reached Phase III trials. Because memantine treats Alzheimer's symptoms in a different way than the four currently approved drugs, some of the Phase III trials are exploring whether individuals may be able to take both types of drugs simultaneously.