Clinical utility of progesterone receptor modulators and their effect on the endometrium

Irving M. Spitz, Spitz IM
Current opinion in obstetrics & gynecology · 2009 · vol. 21(4) , pp. 318–324 · doi:10.1097/gco.0b013e32832e07e8 · PMID:19602929 · W2126753591
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⚙ AI-generated summary by gemini-2.5-flash-lite, 2026-06-13 ⓘ

Progesterone receptor modulators like mifepristone are effective for uterine fibroids and endometriosis, but require careful monitoring for unique endometrial changes that do not indicate hyperplasia.

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This review evaluates the clinical utility of progesterone receptor modulators, including mifepristone and asoprisnil, based on randomized controlled trials. The authors report that these compounds effectively reduce pain, bleeding, and fibroid size, while also demonstrating efficacy in treating endometriosis. A significant limitation noted is the risk of long-term endometrial thickening due to cystic glandular dilatation, which mimics hyperplasia but is histologically distinct. Consequently, current guidelines restrict treatment duration to three or four months to mitigate these uterine effects. Relevance to endometriosis: CDB-4124 is explicitly cited as efficacious for this condition, although the paper primarily focuses on its use for uterine fibroids and associated endometrial changes.

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Abstract

PURPOSE OF REVIEW: In view of the spate of recent publications related to mifepristone and some second generation progesterone receptor modulators (PRMs), this appears to be an opportune time to view the clinical status of these compounds. RECENT FINDINGS: Randomized double-blind placebo-controlled trials have been conducted with mifepristone, CDB-4124 (Proellex), CDB-2914 (VA 2914, Ulipristal) and asoprisnil (J867). All these PRMs are effective in the treatment of uterine fibroids where they are associated with a reduction in pain, bleeding and improvement in quality of life and decrease in fibroid size. CDB-4124 is also efficacious in endometriosis. Long-term treatment with PRMs may be associated with endometrial thickening on ultrasound and there have been reports of endometrial hyperplasia. Several reassuring recent publications have done much to explain the mechanism underlying these endometrial changes. The most common histological finding is cystic glandular dilatation often associated with both admixed estrogen (mitotic) and progestin (secretory) epithelial effects. This histology has not been previously encountered in clinical practice and should not be confused with endometrial hyperplasia. The endometrial thickness is related to this cystic glandular dilatation. SUMMARY: At this stage of development, PRMs cannot be administered for longer than 3 or 4 months. Even over this time, there is improvement of symptoms associated with fibroids and endometriosis. Clinicians and pathologists need to be aware that the endometrial thickening and histological appearance do not represent endometrial hyperplasia.
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Clinical utility of progesterone receptor modulators and their effect on the endometrium - Irving M Spitz Purpose of review In view of the spate of recent publications related to mifepristone and some second generation progesterone receptor modulators (PRMs), this appears to be an opportune time to view the clinical status of these compounds. Recent findings Randomized double-blind placebo-controlled trials have been conducted with mifepristone, CDB-4124 (Proellex), CDB-2914 (VA 2914, Ulipristal) and asoprisnil (J867). All these PRMs are effective in the treatment of uterine fibroids where they are associated with a reduction in pain, bleeding and improvement in quality of life and decrease in fibroid size. CDB-4124 is also efficacious in endometriosis. Long-term treatment with PRMs may be associated with endometrial thickening on ultrasound and there have been reports of endometrial hyperplasia. Several reassuring recent publications have done much to explain the mechanism underlying these endometrial changes. The most common histological finding is cystic glandular dilatation often associated with both admixed estrogen (mitotic) and progestin (secretory) epithelial effects. This histology has not been previously encountered in clinical practice and should not be confused with endometrial hyperplasia. The endometrial thickness is related to this cystic glandular dilatation. Summary At this stage of development, PRMs cannot be administered for longer than 3 or 4 months. Even over this time, there is improvement of symptoms associated with fibroids and endometriosis. Clinicians and pathologists need to be aware that the endometrial thickening and histological appearance do not represent endometrial hyperplasia.

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Condition tags

endometriosis

MeSH descriptors

Endometrium Endometrium Hormone Antagonists Receptors, Progesterone Drug Administration Schedule Endometriosis Endometriosis Endometriosis Endometrium Estrenes Estrenes Estrenes Female Hormone Antagonists Hormone Antagonists Humans Leiomyoma Leiomyoma Leiomyoma Mifepristone

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References (47)

Cited by (26)

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