(FORTUNE Magazine) – Visions of an eventual $1-billion-plus market sparked a race to develop a memory-enhancing drug, especially for victims of Alzheimer's disease (FORTUNE, January 20). In mid-November private researchers in California announced a / significant improvement in the memories of 16 of 17 Alzheimer's patients who were given a year-long dose of an experimental drug. Called tetrahydroaminoacridine, or THA, the drug blocks an enzyme that limits production of a crucial brain chemical. Major pharmaceutical companies have not worked with THA so far, but now they surely will.