Rigel Pharmaceuticals, Inc., a clinical-stage drug development company, engages in the discovery and development of novel, small-molecule drugs for the treatment of inflammatory and autoimmune diseases, as well as muscle disorders. Its product development programs include fostamatinib, an oral spleen tyrosine kinase (SYK) inhibitor that is in Phase III clinical trials for rheumatoid arthritis; R343, an inhaled SYK inhibitor, which completed Phase I clinical trials for asthma; R333, a topical JAK/SYK inhibitor, which is in Phase I clinical trials for the treatment of discoid lupus; and R548, an oral janus kinase 3 (JAK3) inhibitor that in Phase I clinical trials for the treatment of transplant rejection and other immune disorders. The company’s research/preclinical programs comprise R348, a soluble JAK/SYK inhibitor for topical ophthalmic use; R256, an inhaled interleukin 13 signaling inhibitor for chronic asthma; an oral activator of adenosine monophosphate activated protein kinase for enhancing the body’s energy utilization and restore muscle endurance in chronically ill subjects; and growth/differentiation factor 8 inhibitor to prevent muscle loss. Rigel Pharmaceuticals, Inc. has collaboration agreements with AstraZeneca AB to develop and commercialize oral SYK inhibitors; and Daiichi Sankyo Co., Ltd. to conduct research related to drug targets called ligases that control cancer cell proliferation through protein degradation, as well as a license agreement with BerGenBio AS for the development and commercialization of an oncology program. The company was founded in 1996 and is based in South San Francisco, California.