Neurocrine Biosciences

Elagolix - Gonadotropin-Releasing Hormone (GnRH) Antagonist


Jana Cahill, Wife and Mother.
"We are very blessed to have a beautiful child in our lives, my 15 year old foster son.  I have a wonderful life, a wonderful marriage, and if something gets in the way of the plans of life, it is not worth the pain.  After surgery, I am now pain free."

Jana Cahill, Wife and Mother

Endometriosis is associated with a multitude of symptoms, some of the most common of which include pain related both to menstruation (dysmenorrhea) and sexual intercourse (dyspareunia) as well as chronic pelvic pain throughout the menstrual cycle, infertility, and menorrhagia, among many others. The wide range of symptoms associated with endometriosis serves to complicate and delay diagnosis due to the significant overlap of symptoms with the disease profiles of other conditions. The World Endometriosis Research Foundation estimates that there are over 170 million women worldwide who suffer from endometriosis. Datamonitor (2009) estimates that there are approximately 7.5 million women in the United States who suffer from the symptoms of endometriosis. We believe that the availability of an oral treatment, lacking the side effect profile of the currently available peptide GnRH agonists, may be a desirable alternative to current pharmaceutical therapies and ultimately encourage a significantly higher treatment rate.

Addressable Population

• 7.5 million women in the US alone are believed to suffer from clinically significant endometriosis (Datamonitor)
• When diagnosed, 75% of endometriosis sufferers have symptoms defined as ‘moderate or severe’ (IMS Health, NDTI)
• 10-20% of all oral contraceptive prescriptions are written off-label for endometriosis (IMS Health, Neurocrine market research)
• OBGYNs prescribe NSAIDs and opioids “off-label” to approximately 25% of their endometriosis patients

Neurocrine Approach - Nonpeptide GnRH Antagonists

Gonadotropin-releasing hormone, or GnRH, is a peptide that stimulates the secretion of the pituitary hormones that are responsible for sex steroid production and normal reproductive function. Researchers have found that chronic administration of GnRH agonists, after initial stimulation, reversibly shuts down this transmitter pathway and is clinically useful in treating hormone-dependent diseases such as endometriosis and uterine fibroids. Several companies have developed peptide GnRH agonists on this principle, such as Lupron® and Zoladex®. However, since they are peptides, they must be injected via a depot formulation rather than the preferred oral route of administration. In addition, GnRH agonists can take up to several weeks to exert their desired effect once the initial stimulation has occurred, a factor not seen with the use of GnRH antagonists. More importantly, until the desired effects are maximal, GnRH agonists have shown a tendency to exacerbate the condition via a hormonal flare. The ultimate profound suppression effect observed with GnRH agonists is similar to that seen after menopause and can be associated with hot flashes and the loss of bone mineral density.

Orally active, nonpeptide GnRH antagonists potentially offer several advantages over injectable GnRH peptide drugs, including rapid onset of hormone suppression without a hormonal flare. Also, injection site reactions commonly observed in peptide depots are avoided and dosing can be rapidly discontinued if necessary – a clinical management option not available with long-acting depot injections. Importantly, by using GnRH antagonists, it may be possible to alter the level of pituitary GnRH suppression thereby titrating circulating estrogen levels. Using this approach, an oral GnRH antagonist may provide patients relief from the painful symptoms of endometriosis while avoiding the need for the active management of bone loss.

Phase I and II Clinical Results


Following the success of NBI-56418 currently in Phase II clinical trials in endometriosis, Neurocrine’s research group is investigating the potential of certain GnRH antagonists in treating other hormone dependent diseases.

To date, 18 Phase I and II clinical trials of our lead, orally active nonpeptide GnRH antagonist, elagolix, for endometriosis have been completed. These studies demonstrated that elagolix was safe and well tolerated.  A dose-dependent suppression of estradiol with once a day dosing was observed with doses between 50mg and 400mg /day.  The reduction in estradiol has been correlated with a reduction in pain and other symptoms of endometriosis and is a useful biomarker for safety and efficacy.  Based on the results of these Phase I trials, we completed two separate exploratory three-month Phase IIa trials, during 2006, in endometriosis patients to assess efficacy and tolerability of elagolix.  Efficacy in these Phase II studies was assessed by the Composite Pelvic Sign and Symptoms Score (CPSSS), a monthly recall scale that measures dysmenorrhea, non-menstrual pelvic pain, dyspareunia, pelvic tenderness and induration (all elements of endometriosis pain) and Visual Analog Scale (VAS) industry-standard and validated measures utilized for evaluating pain reduction in endometriosis patients.  In addition to the standard clinical and laboratory assessments of safety, a biomarker for bone resorption (n-telopeptide) was also measured to assess potential impact on bone mineral density.

During 2008, we completed the first Phase IIb study of elagolix (PETAL or 603 study) in which 252 patients, with a laparoscopic diagnosis of endometriosis, were treated over the initial six-month period. This multi-center, randomized, double-blind, double-dummy study consisted of three treatment groups, elagolix 150mg once a day, elagolix 75mg twice daily, and an active control, DMPA-SC. The primary purpose of this study was to assess the impact of six months of treatment of elagolix on bone mineral density as measured by a dual energy x-ray absorptiometry (DXA) scan at the conclusion of treatment and at six and 12 months post treatment. This study also assessed, as secondary endpoints, the impact of treatment on endometriosis symptoms as measured by Composite Pelvic Signs and Symptoms Scale (CPSSS), a monthly recall scale that measures dysmenorrhea, non-menstrual pelvic pain, dyspareunia, pelvic tenderness and induration (all elements of endometriosis pain). Top-line results showed that elagolix met the primary endpoint by having minimal impact on bone mineral density at the conclusion of treatment. This study also showed that elagolix had both a statistical and clinically meaningful reduction in endometriosis symptoms as measured by CPSSS with an 86% responder rate in the 150mg once daily elagolix arm of the study. Additionally, elagolix was shown to be non-inferior to DMPA-SC under the CPSSS. Patient follow up both six and 12 months post treatment showed elagolix did not result in a significant reduction in bone mineral density as measured by DXA scan, with a mean time of return to ovulation of 24 days for elagolix subjects.

Toward the conclusion of the 603 study, the U.S. Food and Drug Administration (FDA) requested that the endpoints for dysmenorrhea and non-menstrual pelvic pain be assessed on a daily basis rather than utilizing the CPSSS monthly recall scale. In addition, the FDA also provided modified wording to assess the dysmenorrhea and non-menstrual pelvic pain scores on a daily basis. Given these new independent co-primary endpoints, we conducted two additional Phase IIb trials of elagolix to evaluate these modified endpoints as proposed by the FDA, to fully explore the elagolix dose range utilizing both 150mg and 250mg doses. These two trials were designed to assess elagolix for an initial three months, with the non-elagolix treatment arms re-randomized after three months into treatment groups of either 150mg or 250mg of elagolix once daily for an additional three months.

The first additional Phase IIb trial (Lilac PETAL or 702 study) consisted of three arms, elagolix 150mg once daily, elagolix 250mg once daily and placebo. We randomized 155 subjects with a laparoscopic diagnosis of endometriosis in this trial. The three-month placebo-controlled portion of the 702 study showed that elagolix provided endometriosis sufferers with clinical improvement of symptoms, coupled with an excellent safety and tolerability profile. However, the FDA-proposed non-menstrual pelvic pain daily scale had a low baseline score and was relatively insensitive to treatment effects. There were no treatment related serious adverse events in the 702 study and the two most common adverse events were headache and nausea, which were typically mild and transient and consistent with our previous studies. 

The second additional Phase IIb trial (Tulip PETAL or 703 study) consisted of four arms, elagolix 150mg once daily, elagolix 250mg once daily, Prostap® SR 3.75mg (leuprorelin) and placebo. We enrolled 174 subjects with a laparoscopic diagnosis of endometriosis in this trial. The three-month placebo-controlled portion of the 703 study confirmed that elagolix and leuprorelin are associated with reductions in dysmenorrhea and non-menstrual pelvic pain daily scores when compared to placebo. However, the FDA-proposed non-menstrual pelvic pain daily scale numeric changes and dynamic range were both small. Although the adverse events reported in the 703 study as occurring more often with elagolix than with placebo were nausea and headache (<12%), consistent with previous clinical studies of elagolix, these events were generally mild or moderate, transient and not generally associated with study discontinuation. There were no treatment related serious adverse events. 

In August 2009, we held a Type C meeting with the FDA to discuss the non-menstrual pelvic pain scale as proposed by the FDA and used in the 702 and 703 studies. Based on this meeting, we modified the wording of the non-menstrual pelvic pain and dysmenorrhea daily scales and launched a new clinical trial, the Daisy PETAL Study (901 study). This parallel, double-blind, placebo-controlled clinical trial was designed to provide an assessment of the modified scales over an eight-week treatment period of 150mg elagolix, followed by sixteen weeks of open-label treatment. This trial commenced in September 2009 and randomized approximately 130 subjects. In May 2010, we announced the results of this trial which showed the symptoms of dysmenorrhea and non-menstrual pelvic pain, as measured by the modified daily scales, both improved significantly in the elagolix treated arms (p-value<0.001 and p-value<0.01, respectively). Daily dysmenorrhea pain scores were a 2.1 at baseline (0-3 scale) with a 1.13 reduction in the elagolix arm compared to a 0.37 reduction in the placebo arm at eight weeks. Daily non-menstrual pelvic pain scores were a 1.4 at baseline (0-3 scale) with a 0.47 reduction in the elagolix arm compared to a 0.19 reduction in the placebo arm at eight weeks. There were no treatment related serious adverse events in the 901 study and the two most common adverse events were headache and nausea, which were typically mild and transient and consistent with our previous studies.

AbbVie Collaboration

In June 2010, we announced an exclusive worldwide collaboration with AbbVie to develop and commercialize elagolix and all next-generation GnRH antagonists (collectively, GnRH Compounds) for women's and men's health. Under the terms of our agreement with AbbVie, we and AbbVie will work jointly to advance GnRH Compounds towards commercialization. Abbott made an upfront payment of $75 million and agreed to make additional development and regulatory event based payments of up to $480 million and up to an additional $50 million in commercial event based payments. Under the terms of the agreement, AbbVie is responsible for all development, marketing and commercialization costs. We will be entitled to a percentage of worldwide sales of GnRH Compounds for the longer of ten years or the life of the related patent rights.

Elagolix Endometriosis Phase III Studies

The endometriosis Phase III program is assessing two separate doses of elagolix (150mg once-daily and another dose) over a 24-week treatment period. The initial randomized, parallel, double-blind, placebo-controlled pivotal trial (Violet PETAL) is expected to enroll 875 women in approximately 160 clinical sites throughout the United States, Canada and Puerto Rico. The co-primary endpoints are a comparison of the daily non-menstrual pelvic pain and daily dysmenorrhea scores during the third month of treatment to the respective daily baseline scores utilizing a responder analysis. Additional efficacy and safety endpoints include assessing persistence of pain reduction at month six and the impact on bone mineral density after one year of continuous dosing. 

The second Phase III study of elagolix was initiated by AbbVie during 2013. This study is similar in design to the Violet PETAL study with the same co-primary endpoints of daily non-menstrual pelvic pain and daily dysmenorrhea, comparing the third month of treatment to the respective daily baseline scores utilizing a responder analysis. This trial is anticipated to enroll 788 women with moderate to severe endometriosis-associated pain at more than 200 sites globally. AbbVie initiated the elagolix endometriosis Phase III program during the second quarter of 2012, with a new drug application (NDA) filing expected in 2016.

Uterine Fibroids

Uterine fibroids are benign hormonally responsive tumors that form in the wall of the uterus. They are the most common solid tumor in women with a prevalence rate of at least 25% (American College of Obstetricians and Gynecologists). While many women do not have symptoms, depending on the size, location and number, uterine fibroids can cause pelvic pain, reproductive problems, and severe bleeding that can lead to anemia. Due to the severity of symptoms, treatment sometimes requires surgery, including the removal of the uterus. In fact, uterine fibroids is a leading indication for hysterectomy in the United States, with approximately 250,000 hysterectomies performed each year related to uterine fibroids (Whiteman et al AJOG 2008, 198, e1). We believe that a safe and effective oral therapy would be a preferred treatment regimen rather than surgical intervention. 
During 2011, AbbVie initiated a randomized, double-blind, placebo-controlled, Phase IIa study of approximately 300 women to assess the safety and efficacy of elagolix in the treatment of uterine fibroids. The primary endpoint in this study was an assessment of blood loss after three months of treatment with elagolix. The dose ranging study evaluated various doses of elagolix compared to placebo. Additional efficacy endpoints were also evaluated including change in uterine volume, fibroid volume, and change in menstrual patterns. Based on the results of this study, AbbVie launched a Phase IIb uterine fibroids study for elagolix in early 2013. This Phase IIb clinical trial will enroll 520 women with heavy uterine bleeding due to uterine fibroids and assess uterine blood loss after six months of treatment across various dosing regimens of elagolix, utilizing a quantitative assessment tool for blood loss, alkaline hematin. Secondary efficacy endpoints include change in uterine volume, fibroid volume, and change in menstrual patterns. Safety assessments of bone mineral density, comparing baseline to month six, will be performed via DXA scan. Patients will also be followed off drug for up to six months. This study is expected to be completed in 2015.

Other Applications

Our Phase I and II data for elagolix in women support its potential use not only in endometriosis and uterine fibroids, but also in a range of other women’s health indications.  Menorrhagia (excessive uterine bleeding) and primary dysmenorrhea commonly result from underlying endometriosis, uterine fibroids or adenomyosis and, as such, may be amenable to treatment with a nonpeptide GnRH antagonist.  Current peptide antagonists are commercially available for prevention of premature luteinizing hormone (LH) surge as part of Assisted Reproductive Therapy.  Oral GnRH antagonists could reduce the burden of injections for women undergoing these procedures.  Additional women’s health indications such as premenstrual dysphoric disease (PMDD), polycystic ovarian syndrome (PCOS), breast cancer prevention, precocious puberty, or even contraception may also be appropriate indications for an oral nonpeptide antagonist.