HQ Team
July 2, 2025: Organon & Co. has discontinued its clinical development programme for an oral medicine to treat endometriosis-related pain after it failed to meet its main efficacy goal.
The investigational candidate, called OG-6219 or linustedastat, is an inhibitor of the enzyme 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1).
This enzyme plays a critical role in the conversion of estrone to estradiol, the most potent form of estrogen in the body.
By inhibiting HSD17B1, the oral therapy reduces the production of estradiol, thereby exerting antiestrogenic effects in estrogen-dependent tissues such as endometriosis lesions.
Lower estrogen levels
The mechanism is particularly relevant for treating estrogen-dependent conditions, such as endometriosis, where excessive local estrogen production fuels the growth of endometrial-like tissue outside the uterus.
OG-6219 is designed to lower estrogen levels locally by blocking this key step in estrogen biosynthesis, potentially reducing disease symptoms and progression. The targeted enzymatic inhibition aims to reduce estrogen-driven disease activity while preserving overall hormonal balance.
Clinically, OG-6219 has been investigated primarily for endometriosis treatment. It has undergone early and mid-stage clinical trials to evaluate its safety, pharmacokinetics, and efficacy.
A recent mid-stage trial did not show significant improvement in endometriosis-related pelvic pain compared to the dummy drug, leading to the discontinuation of its clinical development by Organon, according to a statement.
Global study
The global multi-centre study aimed to evaluate the efficacy of three dose levels of OG-6219 in pre-menopausal women between 18 to 49 years of age who have been surgically diagnosed with endometriosis with moderate-to-severe endometriosis-related pain.
The HSD17B1 inhibitor was acquired through Organon’s acquisition of Forendo Pharma in 2021.
“While these study results are disappointing, Organon remains committed to our long-term vision to create a better and healthier everyday life for all women, including those living with endometriosis,” said Juan Camilo Arjona Ferreira, M.D., Head of Research & Development and Chief Medical Officer at Organon, headquartered in Jersey City, New Jersey.
