A Study of the Histopathological Changes within Ectopic Endometrial Tissue, in Subjects with Known Pelvic Endometriosis Following Treatment with Ulipristal Acetate, a Selective Progesterone Receptor Modulator (SPRM).

Endometriosis is a common disease, affecting 10% of women of reproductive age. Pharmacological agents play an important role in control of symptoms as well as disease suppression but are limited by systemic side effects. Although surgical management is helpful for some, there is an increasing reliance on medical treatment and the exploration of new treatments such as selective progesterone receptor modulators (SPRMs). \n \nThe aim of this interventional descriptive cohort study was to assess the changes in the ectopic endometrial deposits of twenty patients with pelvic endometriosis after a three-month treatment course of ulipristal acetate (Esmya). Post treatment histological and immunohistochemistry changes were correlated to changes in the macroscopic appearance of the disease and changes in symptom severity. \n \nFeatures of progesterone receptor modulator associate endometrial changes (PAEC) were seen within eutopic endometrial samples, as expected, but no single specimen exhibited the full features of PAEC. The ectopic endometrium exhibited a different pattern of features with cystic dilatation, ciliated metaplasia and infrequent mitoses a more common finding. The presence of these features correlated with the clinical impact of the drug and may offer some insight into the drugs mechanism of action. \n \nA good clinical response to ulipristal acetate was seen in 56% of the cohort with statistically significant improvements in pain scores and overall quality of life relating to endometriosis, which was maintained after stopping treatment. Ulipristal acetate was considered acceptable by the cohort with the median change described as ‘better, and a definite improvement that has made a real and worthwhile difference’. \n \nUlipristal acetate appears to offer an effective treatment for endometriosis with histological changes in keeping with the known experience of PAEC. The safety of this compound remains to be elucidated but the results from this pilot study are encouraging and should prompt further exploration.