ActivX Biosciences, Inc. (www.activx.com), a wholly-owned subsidiary of Tokyo-based Kyorin Pharmaceutical Co., Ltd., in La Jolla, California, is applying proprietary chemical technologies and high-throughput protein analysis to the drug discovery process. By focusing on functional proteins, ActivX addresses disease mechanisms directly, in contrast to approaches such as expression profiling, in which the measured analyte is several steps removed from the site of drug action. ActivX and its partners are using its proprietary technology to address critical challenges in drug discovery, including selectivity profiling of candidate drug molecules across whole protein families in biological samples to guide their medicinal chemistry optimization; identifying novel drug targets and biomarkers; and characterizing off-target activities of candidate and established drugs to understand the basis for their efficacy and toxicity.