FOR-6219 is an experimental small molecule designed to regulate estrogen production, being developed by Forendo Pharma to possibly treat endometriosis.

How FOR-6219 works

Endometriosis is a condition in which tissue resembling the endometrium (tissue that normally lines the uterus) grows outside of the uterus. This tissue still responds to hormones that control the menstrual cycle. These hormones are produced both in the ovaries and in the endometrial tissue itself. During menstruation, a hormone called estrone is converted to a stronger hormone called estradiol, and their increased levels cause the endometrium to swell and shed. But endometrial-like tissue outside of the uterus cannot properly be expelled through menstruation, resulting in pain and inflammation. Left untreated, the lesions may turn into scar tissue.

Treating endometriosis can be difficult, because the endometrial lesions themselves produce some estrogens. (Estrone and estradiol are among the four types of estrogen.)

FOR-6219 is a small molecule that binds to an enzyme called HSD17B1, which converts estrone into estradiol. By inhibiting this enzyme, the production of estradiol is slowed, hopefully reducing swelling and inflammation. FOR-6219 is thought to block the production of estradiol within endometrial lesions, possibly without affecting overall estrogen production, which may reduce side effects.

FOR-6219 in clinical trials

A Phase 1a clinical trial (NCT03709420) tested the safety and pharmacokinetics (movement in the body) of FOR-6219. The study enrolled 36 healthy postmenopausal women and evaluated increasing doses of the therapy at its single test site in London. Participants were randomly assigned to receive either placebo, a single dose of FOR-6219, or multiple doses of up to 150 mg treatment twice daily for 10 days.

Forendo announced that Phase 1a results indicated that the oral treatment is safe and well-tolerated. The company is now planning a Phase 1b trial in healthy premenopausal women to further test FOR-6219’s safety, and to demonstrate its ability to selectively target estrogen production.


Last updated: July 29, 2019


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