TOKYO, August 29, 2025 - (JCN Newswire) - Eisai Co., Ltd. (Headquarters: Tokyo, CEO: Haruo Naito, “Eisai”) announced today that it has received orphan drug designation for anticancer agent the EZH2*1 inhibitor tazemetostat hydrobromide (generic name, product name “Tazverik® Tablets 200 mg”, “tazemetostat”) for unresectable INI1*2-negative epithelioid sarcoma that has progressed after chemotherapy, from the Ministry of Health, Labour and Welfare (MHLW).

Epithelioid sarcoma is a type of soft tissue sarcoma that is a rare cancer estimated to account for about 1% of all soft tissue sarcoma.1 Only 174 cases were registered from major hospitals across Japan over a10-year period from 2006 to 2015.2 Loss of INI1, which is a negative regulator of EZH2, is observed in over 90% of epithelioid sarcoma cases,3 leading to EZH2 activation that is believed to drive tumor onset and malignant progression. Treatment options are limited, resulting in an extremely high unmet medical need.

Tazemetostat was approved in Japan in June 2021 for relapsed or refractory EZH2 gene mutation-positive follicular lymphoma (only when standard treatment is not applicable). For INI1-negative unresectable epithelioid sarcoma that has progressed after chemotherapy, a Phase II investigator-initiated trial of tazemetostat (A Phase II Trial of Tazemetostat for Patients with Unresectable or Metastatic Epithelioid Sarcoma: TAZETTA trial), led by the National Cancer Center Hospital, is currently underway.

Eisai identifies oncology as one of its priority areas and strives to develop ground breaking new therapies aimed at curing cancer. We remain committed to meeting the diverse needs of cancer patients worldwide, their families, and healthcare professionals, and to enhancing the benefits delivered to them.

*1 A type of histone methyl group elongation enzyme, it is a protein that controls gene expression by methylating the 27th lysine residue of histone H3 (H3K27).
*2 One of the proteins that make up the SWI/SNF chromatin complex (a protein complex that modifies chromatinstructure to regulate gene function), it is involved in regulating gene expression.

For more details, please visit: https://www.eisai.com/news/2025/pdf/enews202558pdf.pdf

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