Kissei Initiates Phase III Clinical Trial for GnRH Antagonist "Linzagolix" Indicated for Endometriosis

Kissei Pharmaceutical Co., Ltd. (Head Office: Matsumoto, Nagano; Chairman and CEO: Mutsuo Kanzawa; "Kissei") announced that Kissei initiates Phase III clinical trial for the GnRH antagonist "Linzagolix" (generic name, development code in Japan: KLH-2109), which was developed by Kissei, as indicated for endometriosis.

Endometriosis is a condition in which the endometrium or similar tissue proliferates and sheds outside the uterus, causing various types of pain. It typically develops in women in their 20s to 30s and tends to worsen over time, often becoming most severe in their 30s to 40s. The main symptoms of endometriosis are "pain" and "infertility," with menstrual pain (dysmenorrhea) being observed in 90% of patients with endometriosis. Additionally, symptoms such as constant lower abdominal or back pain (chronic pelvic pain) outside of menstruation, and pain during bowel movements or sexual intercourse, are also present.

In the Phase III clinical trial to be conducted this time, we will target patients with endometriosis who suffer from pelvic pain. We will evaluate the efficacy of the oral administration of Linzagolix on pain during menstruation and non-menstrual periods, using a double-blind method with GnRH receptor agonists as the control. Additionally, we will also assess the safety of Linzagolix.

Regarding Linzagolix, Kissei submitted a new drug application on February 26, 2025, for the indication of uterine fibroids, in Japan.^１ Additionally, overseas, Theramex (UK), our licensee, is set to launch the drug for uterine fibroids in Europe in September 2024,^２ and received approval from the European Medicines Agency (EMA) for the additional indication of endometriosis in November of the same year.^３ Additionally, other licensee companies are progressing with development in South Korea and Taiwan.

Kissei is dedicated to focusing on the development of Linzagolix to make it available to endometriosis patients as soon as possible.

¹ News Release: February 26, 2025
Submission of New Drug Application for GnRH Antagonist "Linzagolix" Indicated for Uterine Fibroids, in Japan

² News Release: September 17, 2024
Launch of Yselty® (generic name linzagolix) for uterine fibroid treatment in Europe

³ News Release: December 23, 2024
Regarding the approval of the additional indication for endometriosis in Europe for the GnRH antagonist Yselty® (generic name linzagolix)


《 Reference 》

About Linzagolix (KLH-2109)
Linzagolix, which was discovered by Kissei is an orally administrable GnRH (gonadotropin-releasing hormone) antagonist. It competes with GnRH at the GnRH receptors in the pituitary gland, suppressing the secretion of gonadotropins, which are gonadal-stimulating hormones. By reducing the production of estrogen in the ovaries, it is expected to improve the symptoms of uterine fibroids and endometriosis.
Linzagolix, which was licensed out to Theramex (U.K.), was launched to the market in Germany in September 2024 under the product name Yselty® for the indication of uterine fibroids, followed by the launch and preparations for launch in other European countries. In Taiwan, an approval application has been submitted by Synmosa Biopharma Corporation (Taiwan), and in South Korea, JW Pharmaceutical Corporation (South Korea) is preparing for development.
In Japan, Kissei is submitted a new drug application for approval of manufacturing and marketing, as indicated for uterine fibroids.