Ligand Pharmaceuticals Incorporated (NASDAQ: LGND) (the "Company" or "Ligand") today announced that it has earned a $1 million milestone payment from Schering-Plough Corporation (NYSE: SGP) related to the progress of Schering-Plough's inhibitor of β-site of APP cleaving enzyme (BACE) for the treatment of Alzheimer's disease, which resulted from a research collaboration with Pharmacopeia (acquired by Ligand). Alzheimer's disease is characterized by plaques of the toxic amyloid-beta protein within the brain. Amyloid-beta is formed when the larger amyloid precursor protein (APP) is cleaved by two enzymes, BACE and gamma-secretase, which releases the amyloid-beta fragment. A BACE inhibitor is expected to reduce amyloid-beta generation in Alzheimer's disease patients.

The milestone payment arises from a drug discovery agreement between Schering-Plough and Pharmacopeia wherein Pharmacopeia contributed to Schering-Plough's medicinal chemistry optimization of compounds discovered by Schering-Plough. Ligand completed its acquisition of Pharmacopeia in December 2008. Under the terms of the collaboration agreement, Ligand is eligible to receive additional payments from Schering-Plough upon the achievement of certain development and regulatory milestones. Ligand is also eligible to receive royalties on potential sales of the drug…