General Information

ella (ulipristal acetate) is a synthetic progesterone agonist/antagonist. When taken immediately before ovulation is to occur, ella postpones follicular rupture. The likely primary mechanism of action of ulipristal acetate for emergency contraception is therefore inhibition or delay of ovulation; however, alterations to the endometrium that may affect implantation may also contribute to efficacy.

ella is specifically indicated as an emergency contraceptive for prevention of pregnancy following unprotected intercourse or a known or suspected contraceptive failure.

ella is supplied as a tablet for oral administration. The recommended dose is one tablet taken orally as soon as possible, within 120 hours (5 days) after unprotected intercourse or a known or suspected contraceptive failure.

Clinical Results

FDA Approval
The FDA approval of ella was based on two studies: an open label study and a single-blind comparative study.
Open label study
This trial enrolled 1,242 healthy female subjects with a mean age of 24 years who requested emergency contraception 48 to 120 hours after unprotected intercourse. The subjects received 30 mg of ella. ella statistically significantly reduced the pregnancy rate, from an expected rate of 5.5% to an observed rate of 2.2% (27 pregnancies).
Single blind study
This multicenter, single-blind, randomized trial was designed to compare the efficacy and safety of 30 mg ella to levonorgestrel (another form of emergency contraception). The trial enrolled 844 female subjects with a mean age of 25 years who requested emergency contraception within 120 hours of unprotected intercourse. The subjects received ella or levonorgestrel 1.5 mg. ella statistically significantly reduced the pregnancy rate, from an expected 5.6% to an observed 1.9%, when taken within 72 hours after unprotected intercourse. There were no pregnancies observed in the women who were administered ella more than 72 hours after unprotected intercourse (10% of women who received ella).
Pooled analysis
Data from the two studies were pooled to provide a total efficacy population of women treated with ulipristal acetate up to 120 hours after unprotected intercourse. Time Trend analysis for the five 24-hour intervals from 0 to 120 hours between unprotected intercourse and treatment was conducted. There were no significant differences in the observed pregnancy rates across the five time intervals.

Literature References

Brache V, Cochon L, Jesam C, Maldonado R, Salvatierra AM, Levy DP, Gainer E, Croxatto HB Immediate pre-ovulatory administration of 30 mg ulipristal acetate significantly delays follicular rupture. Human Reproduction 2010 Sep;25(9):2256-63.

Glasier AF, Cameron ST, Fine PM, Logan SJ, Casale W, Van Horn J, Sogor L, Blithe DL, Scherrer B, Mathe H, Jaspart A, Ulmann A, Gainer E Ulipristal acetate versus levonorgestrel for emergency contraception: a randomised non-inferiority trial and meta-analysis. Lancet 2010 Feb 13;375(9714):555-62

Fine P, Mathé H, Ginde S, Cullins V, Morfesis J, Gainer E Fine P, Mathé H, Ginde S, Cullins V, Morfesis J, Gainer E Obstetrics and Gynecology 2010 Feb;115(2 Pt 1):257-63.