AbbVie's Elagolix Demonstrates Significant Efficacy in Two Phase 3 Trials for Uterine Fibroids
Key Insights
AbbVie (search)'s investigational drug elagolix met primary endpoints in two pivotal Phase 3 studies, achieving clinical response rates of 68.5% and 76.2% compared to placebo rates of 8.7% and 10.1% respectively in women with uterine fibroids (search).
The oral GnRH receptor (search) antagonist, combined with low-dose hormone add-back therapy, significantly reduced heavy menstrual bleeding (search) as measured by the alkaline hematin method in premenopausal women aged 18-51.
Both ELARIS UF-I and UF-II studies met all ranked secondary endpoints, with safety profiles consistent with previous Phase 2 studies, though hypoestrogenic effects including hot flashes and bone mineral density reduction were observed.
AbbVie (search), in cooperation with Neurocrine Biosciences, announced positive topline results from two pivotal Phase 3 studies evaluating elagolix for the treatment of uterine fibroids (search). The ELARIS UF-I and UF-II trials both met their primary endpoints, demonstrating significant reductions in heavy menstrual bleeding (search) compared to placebo.
Strong Efficacy Results Across Both Studies
In the ELARIS UF-I study, 68.5% of women receiving elagolix in combination with low-dose hormone add-back therapy achieved clinical response at month six, compared to only 8.7% in the placebo group (p<0.001). The second study, ELARIS UF-II, showed even stronger results with 76.2% of women achieving clinical response versus 10.1% with placebo (p<0.001).
Clinical response was defined as menstrual blood loss volume of less than 80 mL during month six and a 50% or greater reduction in menstrual blood loss volume from baseline to month six, as measured by the alkaline hematin method. Both studies also met all ranked secondary endpoints, which included measures of bleeding, bleeding suppression, and hemoglobin changes.
Addressing a Significant Unmet Medical Need
Uterine fibroids (search) represent the most common type of abnormal growth in a woman's pelvis, affecting up to 80% of women by age 50. While fibroids can be asymptomatic, approximately 25% of women experience symptoms including heavy menstrual bleeding (search), painful periods, vaginal bleeding at times other than menstruation, and anemia (search). African American women are disproportionately affected, experiencing fibroids more frequently and at younger ages.
"Current non-surgical treatments are limited and women suffering from uterine fibroids (search) need more therapeutic options," said Dawn Carlson, M.D., M.P.H., vice president of general medicine development at AbbVie (search). "The results from this study represent a significant advancement in the development of elagolix and demonstrate our continued commitment to address serious disease."
Study Design and Patient Population
Both ELARIS studies were replicate, pivotal, six-month Phase 3 trials evaluating the safety, tolerability, and efficacy of elagolix alone and in combination with low-dose hormone add-back therapy (estradiol/norethindrone acetate). The studies enrolled premenopausal women aged 18-51 years with uterine fibroids (search) diagnosed by pelvic transvaginal and transabdominal ultrasound.
ELARIS UF-I was conducted at approximately 90 sites in the United States and Canada, while ELARIS UF-II was conducted at approximately 100 sites across the same regions. The primary endpoint in both studies assessed reduction in heavy menstrual bleeding (search) using the alkaline hematin method, an objective measurement of total menstrual blood loss based on quantitation of menstrual blood collected on sanitary products.
Mechanism of Action and Safety Profile
Elagolix is an orally administered, short-acting gonadotropin-releasing hormone (GnRH) receptor antagonist that blocks endogenous GnRH signaling by binding competitively to GnRH receptors in the pituitary gland. This results in rapidly reversible, dose-dependent inhibition of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion, leading to reduced ovarian production of estradiol and progesterone.
The safety profile observed in both Phase 3 studies was consistent with previous Phase 2 trials. Hypoestrogenic effects, including hot flashes and reduction in bone mineral density, were observed with elagolix treatment. To date, elagolix has been studied in over 40 clinical studies involving more than 3,700 subjects.
Regulatory Path Forward
The positive results from both Phase 3 studies will support regulatory submissions for elagolix. Data from these trials will be presented at upcoming medical conferences, and women participating in the studies will continue in either post-treatment follow-up or blinded six-month extension studies.
Dr. Carlson emphasized the potential clinical impact: "Millions of women currently diagnosed with uterine fibroids (search) are faced with limited non-surgical options. The results from this study demonstrate elagolix has the potential to be an important oral treatment option for women suffering from uterine fibroids."