June 28, 2021

Sub-licensing Agreement for Spleen Tyrosine Kinase Inhibitor "Fostamatinib (R788)" with JW Pharmaceutical Corporation

Kissei Pharmaceutical Co., Ltd. (Head Office: Matsumoto, Nagano; Chairman and CEO: Mutsuo Kanzawa; "Kissei") announced that it has entered into a sub-license agreement with JW Pharmaceutical Corporation (Head Office: The Republic of Korea, CEO: SY Lee) to license development and commercialization rights in Korea for fostamatinib (generic name, Product Code: R788), a spleen tyrosine kinase inhibitor discovered by Rigel Pharmaceuticals, Inc. (Headquarter: USA, President and CEO, Raul Rodriguez; "Rigel").

In October 2018, Kissei acquired the development and commercialization rights for fostamatinib in Japan, China, Korea and Taiwan from Rigel. Kissei is responsible for Phase III clinical trials in Japan and conducting partnering activities in the areas we obtained such rights outside Japan. By executing this agreement, JW Pharmaceutical Corporation will develop and commercialize fostamatinib in South Korea. Kissei will receive an upfront payment and milestone payments based on the progress of commercialization in Korea from JW Pharmaceutical and will supply the formulation to JW Pharmaceutical.

Fostamatinib is an oral spleen tyrosine kinase (SYK) inhibitor of Rigel's that suppresses destruction of platelets by macrophages and suppresses platelet depletion. Thereby, it improves the bleeding symptoms caused by immune thrombocytopenic purpura (ITP).

Fostamatinib was approved by the US Food and Drug Administration in April 2018 for the treatment of adult patients with chronic ITP who have had an insufficient response to a previous treatment and launched in May 2018 in the United States with orphan drug designation. In January 2020, fostamatinib was approved by the European Commission for the treatment of chronic ITP in adult patients who are refractory to other treatments and launched in Germany and other countries in July 2020.

Kissei seeks to contribute to the treatment of ITP, an intractable disease, by progressing the development of fostamatinib in its licensed areas.

The up-front income is triggered by this agreement, and it has already been incorporated into the consolidated earnings forecast for the fiscal year ending March 2022 announced on May 11, 2021.


About Idiopathic Thrombocytopenic Purpura (ITP)

ITP is a 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. ITP is classified into "acute ITP" in which the platelet count recovers normally within 6 months from the onset and "chronic ITP" in which thrombocytopenia continues for 6 months or more depending on the course of the medical condition. Fostamatinib is treatment for chronic ITP.

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 17,000* and 2.16 per 100,000** people are newly diagnosed with ITP every year in Japan. While the cause of ITP has still not been definitively elucidated, it is believed that the platelet count is decreased as a result of production of autoantibodies against platelets, leading to the destruction of platelets by macrophages in the spleen. ITP is currently treated with corticosteroids or thrombopoietin (TPO) receptor agonists as well as surgical removal of the spleen.

*: Estimated based on the number of patients having certificates issued for specific disease treatment (designated intractable disease)

**: Int J Hematol, 2011, 93: 329-35

About JW Pharmaceutical Corporation

JW Pharmaceutical Corporation is Korea's leading pharmaceutical company, founded in 1945. They lead innovation by engaging in the development of innovative new medicines and working to improve people's health and lives with cross-boundary efforts.

JW Pharmaceuticals Corporation and Kissei have concluded contracts for Silodosin, a drug for the improvement of urinary dysfunction, and Mitiglinide, a drug for the treatment of diabetes mellitus, both medicines created by Kissei. They are still utilized for the treatment of patients in Korea. For more details of JW Pharmaceutical Corporation, please visit

About Rigel Pharmaceuticals (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 hematologic disorders, cancer and rare immune diseases. Rigel's pioneering research focuses on signaling pathways that are critical to disease mechanisms. Rigel is headquartered in South San Francisco, California, U.S.A. For more details, please visit