August 5, 2021

Sub-licensing Agreement for Spleen Tyrosine Kinase Inhibitor Fostamatinib with Inmagene Biopharmaceuticals

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 Inmagene Biopharmaceuticals(Head Office: People's Republic of China, Chairman and CEO: Jonathan Wang; "Inmagene") to license development and commercialization rights in China (including Hong Kong and Macau) 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, a biotech company in South San Francisco. Kissei is responsible for conducting Phase III clinical trials in Japan and partnering activities in the areas we obtained such rights outside Japan. By executing this agreement, In China, including Hong Kong and Macau, Inmagene will develop and commercialize fostamatinib. Kissei will receive an upfront payment and milestone payments based on the progress of the development and commercialization conducted by Inmagene and will supply the product to Inmagene.

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

Fostamatinib has been granted orphan drug status in the United States and Japan. It 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. 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.In South Korea, in June 2021, Kissei entered into a sublicense agreement with JW Pharmaceutical Co., Ltd. ("JWP") regarding development and commercialization rights for fostamatib, and JWP proceeds with the development and commercialization.

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

The up-front income is triggered by this agreement, and it has neglible effects on Kissei's consolidated business forecasts for the fiscal year ending in March 2022.

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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 a 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 Inmagene Biopharmaceuticals
Inmagene, with wholly owned subsidiaries in San Diego, Shanghai, Hangzhou and Wuhan, is a leading biotech company focused on developing novel therapeutics for immunology-related diseases. Believing in "borderless innovation", the Inmagene team integrates efficient resources worldwide to make such therapeutics available to patients globally. The company is building a pipeline of many inovative drug candidates and has formed strategic partnerships with biotech companies to develop and commercialize highly innovative drug candidates. For more details, please visit