Effects of Combination of Estradiol with Selective Progesterone Receptor Modulators (SPRMs) on Human Breast Cancer Cells In Vitro and In Vivo

Experimental and new investigational drugs for the treatment of uterine fibroids

INTRODUCTION

Uterine fibroids, the most prevalent benign tumors among reproductive-age women, pose treatment challenges that range from surgical interventions to medical therapies for symptom control. Progestins and estroprogestins effectively manage uterine bleeding by suppressing dysfunctional endometrium over fibroids. While GnRH agonists represent a crucial milestone in symptom treatment, their prolonged use results in menopausal-like symptoms and irreversible bone mineral density loss. Advancements in understanding fibroid pathophysiology have prompted the exploration of new compounds to overcome current therapy limitations.

AREAS COVERED

This manuscript offers an updated overview of investigational drugs for symptomatic uterine fibroids.

EXPERT OPINION

Despite ulipristal acetate's well-established efficacy as a selective progesterone receptor modulator (SPRM) in fibroid treatment, its prescription has declined due to the rare but severe risk of liver damage. Oral GnRH antagonists, like elagolix, relugolix, and linzagolix, with their novel pharmacodynamic properties, are gaining traction in fibroid management, inducing a dose-dependent reduction in circulating sex hormone levels. Ongoing research on natural compounds, such as vitamin D and epigallocatechin gallate (EGCG), presents emerging options for treating uterine fibroids. This evolving landscape reflects the ongoing efforts to improve therapeutic outcomes for individuals with symptomatic uterine fibroids.

EC313-a tissue selective SPRM reduces the growth and proliferation of uterine fibroids in a human uterine fibroid tissue xenograft model

Uterine fibroids (UFs) are associated with irregular or excessive uterine bleeding, pelvic pain or pressure, or infertility. Ovarian steroid hormones support the growth and maintenance of UFs. Ulipristal acetate (UPA) a selective progesterone receptor (PR) modulator (SPRM) reduce the size of UFs, inhibit ovulation and lead to amenorrhea. Recent liver toxicity concerns with UPA, diminished enthusiasm for its use and reinstate the critical need for a safe, efficacious SPRM to treat UFs. In the current study, we evaluated the efficacy of new SPRM, EC313, for the treatment for UFs using a NOD-SCID mouse model. EC313 treatment resulted in a dose-dependent reduction in the fibroid xenograft weight (p < 0.01). Estradiol (E2) induced proliferation was blocked significantly in EC313-treated xenograft fibroids (p < 0.0001). Uterine weight was reduced by EC313 treatment compared to UPA treatment. ER and PR were reduced in EC313-treated groups compared to controls (p < 0.001) and UPA treatments (p < 0.01). UF specific desmin and collagen were markedly reduced with EC313 treatment. The partial PR agonism and no signs of unopposed estrogenicity makes EC313 a candidate for the long-term treatment for UFs. Docking studies have provided a structure based explanation for the SPRM activity of EC313.

The action of estrogens and progestogens in the young female breast

Evidence from different sources sustains a pro-oncogenic role of hormones, estrogens and progestogens, on the breast. The issue is of interest for young women, who are exposed to the hormonal changes imposed by the ovarian cycle and, often, take hormones with contraceptive purposes. Experimental and clinical studies show that both estrogens and progesterone are involved in mammary development during puberty and lactation, the changes being observed across mammalian species, including humans. Estrogen receptors, and more particularly the alpha isoform, participate in molecular processes of stem cells differentiation and epithelial proliferation through paracrine actions implicating growth factors. Progesterone also contributes through paracrine mechanisms involving one member of the tumor necrosis factor (TNF) family, the receptor activator of nuclear factor κB ligand (RANKL) and its receptor (RANK). Epidemiological studies have found that the length of the exposure to endogenous hormones, as determined by an early menarche or a late menopause, is a risk factor for breast cancer. Additional evidence has derived from studies with compounds modulating the estrogen or the progesterone receptors. Selective estrogen receptor modulators (SERM), like tamoxifen, have been shown to decrease the risk of breast cancer in both pre- and post-menopausal women. Aromatase inhibitors, which drastically reduce the levels of circulating estrogens, have reproduced the findings. The selective progesterone receptor modulators (SPRM) have been less investigated and issues concerning safety have arisen. These observations have interest for young women. High-risk women may consider the use of SERMs, for example, to reduce their risk. Much more common is the case of women who take hormones for contraception. The goal of the present article is twofold: i) to summarize the actual knowledge of the mechanisms implicating estrogens and progestogens on the risk for breast cancer and ii) to provide rationality for the debate about potential cancer risk of hormonal contraceptives, frequently used by premenopausal women.