The history and use of the progesterone receptor modulator ulipristal acetate for heavy menstrual bleeding with uterine fibroids

Progesterone receptor modulators (PRM) or selective progesterone receptor modulators have two remarkable effects in treated women. They considerably suppress endometrial bleeding by incompletely understood mechanisms, and when administered in women with symptomatic fibroids, they produce a significant and potentially long-term decrease in fibroid volume. The crucial advantage of this therapy lies with the absence of suppression of ovarian oestrogen secretion, which is in contrast to GnRH agonists. Long-term treatments have proven to be useful, especially in women approaching the menopausal transition. However, their use is associated with endometrial modifications called PRM-associated endometrial changes (PAECs). Although these abnormalities are now described as benign, the treatment is best administered in an intermittent manner where the PAECs rapidly disappear, while the beneficial effects on fibroid size and uterine bleeding are maintained or even improved in the long term.