Rigel Pharmaceuticals, Inc. announced that the U.S. Food and Drug Administration (FDA) approved Tavalisse (fostamatinib disodium hexahydrate) for the treatment of thrombocytopenia in adult patients with chronic immune thrombocytopenia (ITP) who have had an insufficient response to a previous treatment. Tavalisse is an oral spleen tyrosine kinase (SYK) inhibitor that targets the underlying autoimmune cause of the…