San Diego-based pharmaceuticals firm Ligand Pharmaceuticals said Thursday morning that it has entered into a definitive merger agreement to acquire Pharmacopeia. The deal is worth $70M. According to the firm, the deal is a stock-for-stock exchange plus up to $15M in contingent cash payments. Pharmacopeia is a biopharmaceuticals firm developing small molecule therapeutics; the firm has nine clinical compounds in Phase 2 or Phase 1 development. Ligand has a pipeline of compounds targeted at a wide range of conditions. According to Ligand, it was advised by Goldman Sachs and Latham & Watkins LLP in the deal; Pharmacopeia was advised by Cowen and Company and Ligand and Dechert LLP.