September 20, 2019

Kissei Initiates Phase III Clinical Trial for Fostamatinib in Japanese Patients with Chronic Idiopathic Thrombocytopenic Purpura

Kissei Pharmaceutical Co., Ltd. (Chairman and CEO: Mutsuo Kanzawa; "Kissei") announced today that Kissei initiated a Japanese Phase III clinical study of fostamatinib disodium hexahydrate (generic name: fostamatinib), a small molecule tyrosine kinase inhibitor in chronic idiopathic thrombocytopenic purpura (ITP) *1. Kissei and Rigel Pharmaceuticals, Inc. (Headquarter: USA, President and CEO, Raul Rodriguez; "Rigel") entered into an agreement to exclusively develop and sell this product in Japan, China, Korea, and Taiwan in October 2018.

Chronic ITP is designated as an intractable disease by the Minister of Health, Labour and Welfare in Japan. Chronic ITP causes serious bleeding events and bruising due to a decrease in platelet count despite the absence of other obvious illnesses or medications that cause thrombocytopenia. In this trial, the efficacy and safety of orally administered fostamatinib will be assessed by comparing with placebo in randomized, double-blind way in patients with chronic ITP.

Fostamatinib is an orally available small molecule that was discovered by Rigel. By inhibiting SYK*2 which is a tyrosine kinase, fostamatinib suppresses phagocytosis and destruction of platelets by macrophages, and it is expected to improve Chronic idiopathic thrombocytopenic purpura.

It is designated as an orphan drug for the indication of chronic ITP in the USA where it has been marketed by Rigel since May 2018 under the commercial name TAVALISSE®. In October 2018, the European Medicines Agency (EMA) completed its validation of the Marketing Authorization Application (MAA) for fostamatinib which is currently under review for approval.

Kissei will proceed with this phase 3 study appropriately to bring fostamatinib to patients with chronic ITP as soon as possible.

*1: Idiopathic thrombocytopenic purpura (ITP)
ITP is an autoimmune disease which causes serious bleeding events and bruising due to a decrease in platelet count below 100,000/μL, despite the absence of other obvious illnesses and medications that cause thrombocytopenia. The clinical symptoms of ITP include subcutaneous bleeding (petechiae or purpura) as well as bleeding from the gums or nose, blood in the urine or stool, and intracranial bleeding.

ITP is designated as an " intractable disease" by the Minister of Health, Labour and Welfare. The number of patients with ITP is estimated to be approximately 20,000 and 2.4 per 100,000 people are newly diagnosed with ITP every year in Japan. ITP is currently treated with corticosteroids or thrombopoietin (TPO) receptor agonists and surgical removal of the spleen.

*2: SYK (Spleen Associated Tyrosine Kinase)
SYK is a tyrosine kinase, an enzyme that specifically phosphorylates tyrosine residues in proteins. It is involved in histamine release and cytokine production by mast cells via the activation of the IgE receptor, phagocytosis/destruction of autoantibody (IgG)-bound platelets by macrophages, activation of osteoclasts, and differentiation as well as activation of B lymphocytes. It is also known to be related to certain types of cancer, autoimmune diseases, and fungal and viral infections.

About Rigel Pharmaceuticals, Inc.
Rigel Pharmaceuticals, Inc., is a biotechnology company dedicated to discovering, developing and providing novel small molecule drugs that significantly improve the lives of patients with immune and hematologic disorders, cancer and rare diseases. Rigel's pioneering research focuses on signaling pathways that are critical to disease mechanisms. The company's first FDA approved product is TAVALISSE® (fostamatinib disodium hexahydrate), the only oral spleen tyrosine kinase (SYK) inhibitor, for the treatment of adult patients with chronic immune thrombocytopenia who have had an insufficient response to a previous treatment. Rigel's clinical programs include a Phase 3 study of TAVALISSE in warm autoimmune hemolytic anemia (AIHA). In addition, Rigel has product candidates in clinical development with several global partners. For more details of Rigel, please visit