Effects of antiprogestins on the uterus

Uterine fibroids and current clinical challenges

Uterine fibroids (UF) are the most common gynecological tumors in premenopausal women. Hysterectomy remains the major and definitive therapeutic option. Minimally invasive surgical techniques for performing hysterectomy have many advantages over laparotomy. Current drug therapies for UF remain unsatisfactory. Unquestionably, continued investigation of novel agents is necessary. The currently used drugs for UF treatment which exclusively modulate a single target, typically either the estrogen or progesterone signaling pathways, are limited in their therapeutic effects. By contrast, multi-target drugs which simultaneously modulate multiple critical hubs in the network of the signaling pathways underlying UF pathogenesis should achieve robust and durable therapeutic effects.

The state-of-the-art of emergency contraception with the cutting edge drug

The objective of this study is to evaluate and elucidated the potential of selective progesterone receptor modulators (SPRMs) to be an effective emergency contraception (EC). The data are extracted from the literature through the MEDLINE database service from 2000-2010. The SPRMs are in fact progesterone receptor ligands that could bind to progesterone receptor (PR) and exert antagonistic, agonistic or mixed agonist-antagonistic effects. These SPRMs are mifepristone, onapristone, asoprisnil, ulipristal, proellex among other compounds. Currently developed SPRMs may exert contraceptive effects by inhibiting ovulation and retarding endometrial synchronization. Low-doses of progesterone antagonists retard endometrial maturation without affecting ovulation. Mifepristone being a SPRM is effective for prevention of pregnancy but with prostaglandin acts as an excellent abortifacient; yet could not compete with levonorgestrel as EC. However, a single dose of 30 mg ulipristal acetate, another SPRM with similar effectiveness and side effect profiles as 1.5 mg levonorgestrel EC, has shown wider 'window of effect' by inhibition of the LH peak even if administered at the advanced pre-ovulatory phase, a time when use of levonorgestrel EC is no longer effective. Thus, ulipristal acetate goes one-step ahead of levonorgestrel in the field of emergency contraception treatment. Further studies are needed to explore the potential of other SPRMs to be cutting edge emergency contraceptive drugs.