Portola Pharmaceuticals Inc., of South San Francisco, began Phase I trials of PRT062607, a spleen tyrosine kinase-specific inhibitor being developed for chronic inflammatory diseases such as rheumatoid arthritis, systemic lupus erythematosus and certain cancers. The multiple ascending dose study will assess safety, pharmacokinetics and pharmacodynamics of the drug in 40 healthy subjects. It is expected to be competed in mid-2011.