Fostamatinib is commercially available in the U.S. under the brand name TAVALISSE® and is the first and only spleen tyrosine kinase (SYK) inhibitor indicated for the treatment of thrombocytopenia in adult patients with chronic immune thrombocytopenia (ITP) who have had an insufficient response to a previous treatment.

Rigel will exclusively supply Kissei product and will receive tiered transfer price payments based on net sales of the product in the Territory.

Development of fostamatinib in Japan:

  • Kissei announced positive topline results from a Japanese phase 3 clinical study of fostamatinib in patients with chronic ITP in December 2021
  • In April 2023, Kissei announced the availability of TAVALISSE for the treatment of adult chronic ITP in Japan.