 SOUTH SAN FRANCISCO, Calif., May 5, 2021 PRNewswire -- Rigel Pharmaceuticals, Inc. Nasdaq: RIGL today reported financial results for the first quarter ended March 31, 2021, including sales of TAVALISSE fostamatinib disodium hexahydrate tablets, for the treatment of adults with chronic immune thrombocytopenia ITP who have had an insufficient response to a previous treatment. 