Discovery of Sodium R-(+)-4-{2-[5-(2-Fluoro-3-methoxyphenyl)-3-(2-fluoro-6-[trifluoromethyl]benzyl)-4-methyl-2,6-dioxo-3,6-dihydro-2H-pyrimidin-1-yl]-1-phenylethylamino}butyrate (Elagolix), a Potent and Orally Available Nonpeptide Antagonist of the Human Gonadotropin-Releasing Hormone Receptor

Recent Development of Non-Peptide GnRH Antagonists

The decapeptide gonadotropin-releasing hormone, also referred to as luteinizing hormone-releasing hormone with the sequence (pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂) plays an important role in regulating the reproductive system. It stimulates differential release of the gonadotropins FSH and LH from pituitary tissue. To date, treatment of hormone-dependent diseases targeting the GnRH receptor, including peptide GnRH agonist and antagonists are now available on the market. The inherited issues associate with peptide agonists and antagonists have however, led to significant interest in developing orally active, small molecule, non-peptide antagonists. In this review, we will summarize all developed small molecule GnRH antagonists along with the most recent clinical data and therapeutic applications.

Alternative Oral Agents in Prophylaxis and Therapy of Uterine Fibroids-An Up-to-Date Review

Uterine fibroids (UFs) are the most common tumors of the female genital tract. The effect of UFs on the quality of life and the overall cost of treatment are significant issues worldwide. Tumor size and location are the two specific factors which influence the occurrence of symptoms, the need for, and method of, treatment (some tumors require surgery while some can be treated with selected drugs). Primary prevention and treatment of early UF disease are worthy goals that might have a great impact on health care systems. Several treatments and prophylactic methods can be used in this endeavor. This publication presents current data about lesser-known substances which may have a beneficial effect on the treatment or prophylaxis of UFs and can be administered orally, serving as an alternative to (or complement of) surgery or selective progesterone receptor modulators (SPRMs). Early prevention and treatment of UFs in women from high-risk groups should be our priority. Innovative forms of UF management are under intensive investigation and may be promising options in the near future. Many of them evaluated vitamin D, paricalcitol, epigallocatechin gallate (EGCG), elagolix, aromatase inhibitors (AIs), and cabergoline and deemed them to be safe and effective. The next step in such projects should be properly constructed randomized control trials (RCTs), carried out by successive phases.

Efficacy of elagolix in the treatment of endometriosis

INTRODUCTION

Much research has gone into developing medications that can be used to alleviate endometriosis-associated symptoms. In addition to already established medications, a new GnRH antagonist, elagolix, is in development. The novelty of this drug compared to other GnRH antagonists, is its nonpeptide structure, allowing it to be administered orally. Areas covered: We analyzed several Phase I, II and III clinical trials that have evaluated the safety and efficacy of this new medication. Expert opinion: Since many medications have been put on the market and have gained popularity for the treatment of endometriosis-associated symptoms, the demonstration of equality or superiority of effect, tolerability, as well as patient compliance should be assessed when introducing a new drug. While elagolix may have an advantage over established GnRH agonists, in that it does not lead to a 'flare-up' effect, it too, takes a toll on bone mineral density. Nevertheless, studies have shown that this new oral GnRH antagonist is well tolerated, and the side effects have been described as 'mild or moderate'. However, in order to examine whether elagolix can compete with or even surpass established gold-standard medical treatments in this field, further studies that directly compare elagolix to said treatments, might be necessary.

A Regioselective Synthesis of 6-Alkyl- and 6-Aryluracils by Cs2CO3- or K3PO4-Promoted Dimerization of 3-Alkyl- and 3-Aryl-2-Propynamides

A regioselective synthesis of 6-alkyl- and 6-aryluracils was developed by the dimerization of 3-alkyl- and 3-aryl-2-propynamides promoted by either Cs₂CO₃ or K₃PO₄. A range of 3-aryl-2-propynamides, with both electron-deficient and electron-rich 3-aryl substituents, were successfully reacted in high yields. Cs⁺ acts as a soft Lewis acid to polarize the carbon-carbon triple bond, and solid K₃PO₄ interacts with carbonyl oxygen, promoting intermolecular nucleophilic attack by the only weakly nucleophilic amide nitrogen. Experiments were conducted to support the proposed mechanism.

Dose-Dependent Suppression of Gonadotropins and Ovarian Hormones by Elagolix in Healthy Premenopausal Women

CONTEXT

Elagolix is a nonpeptide, oral gonadotropin-releasing hormone (GnRH) antagonist being developed for sex-hormone-dependent diseases in women.

OBJECTIVE

We evaluated the pharmacokinetics and pharmacodynamics of elagolix.

DESIGN, SETTING, AND PARTICIPANTS

This study was a randomized, double-blind, placebo-controlled, multiple-ascending dose study in 45 healthy premenopausal women at a research unit.

INTERVENTIONS

Elagolix [150 mg once daily or 100, 200, 300, or 400 mg twice daily (BID)] or placebo was administered for 21 days.

MAIN OUTCOME MEASURES

Main outcome measures were elagolix pharmacokinetics, suppression of gonadotropics [follicle-stimulating hormone (FSH), luteinizing hormone (LH)] and ovarian hormones [estradiol (E2), progesterone (P)], and adverse events.

RESULTS

Elagolix was rapidly absorbed after oral dosing, reaching maximum concentrations at 1.0 to 1.5 hours, with a half-life of 4 to 6 hours. FSH, LH, and E2 were suppressed within hours of elagolix administration on day 1. Dose-dependent suppression of E2 was observed, with maximum suppression achieved with elagolix 200 mg BID. Dose-dependent suppression of FSH and LH was also observed, with maximal or near-maximal suppression achieved at 300 mg BID and 200 mg BID, respectively. At elagolix doses ≥100 mg BID, P concentrations remained at anovulatory levels throughout 21 days of dosing. The most frequently reported adverse events were headache and hot flush.

CONCLUSIONS

Elagolix administration allows for modulation of gonadotropin and ovarian hormone concentrations, from partial suppression at lower doses to nearly full suppression at higher doses. The results of this study provide a rationale for elagolix dose selection for treatment of sex hormone-dependent diseases in women.

Overview of elagolix for the treatment of endometriosis

INTRODUCTION

Suppression of sex-steroid secretion is required in a variety of gynecological conditions. This can be achieved using gonadotropin releasing hormone (GnRH) agonists that bind pituitary gonadotropin receptors and antagonize the link-receptor of endogenous GnRH, inhibiting the mechanism of GnRH pulsatility. On the other hand, GnRH antagonists immediately reduce gonadal steroid levels, avoiding the initial stimulatory phase of the agonists. Potential benefits of GnRH antagonists over GnRH agonists include a rapid onset and reversibility of action. Older GnRH antagonists are synthetic peptides, obtained by modifications of certain amino acids in the native GnRH sequence. They require subcutaneous injections, implantation of long-acting depots. The peptide structure is responsible for histamine-related adverse events and the tendency to elicit hypersensitivity reactions.

AREAS COVERED

Research has worked towards the development of non-peptidic molecules exerting antagonist action on GnRH. They are available for oral administration and may have a more beneficial safety profile in comparison with peptide GnRH antagonists. This article focuses on the data of the literature about elagolix, a novel non-peptidic GnRHantagonist, in the treatment of endometriosis.

EXPERT OPINION

Elagolix demonstrated efficacy in the management of endometriosis-associated pain and had an acceptable safety and tolerability profile. However, further studies are necessary to evaluate its non-inferiority in comparison with other endometriosis's treatments.

Discovery of an Orally Bioavailable Gonadotropin-Releasing Hormone Receptor Antagonist

We developed a compound library for orally available gonadotropin-releasing hormone (GnRH) receptor antagonists that were based on a uracil scaffold. On the basis of in vitro activity and CYP inhibition profile, we selected 18a (SKI2496) for further in vivo studies. Compound 18a exhibited more selective antagonistic activity toward the human GnRH receptors over the GnRHRs in monkeys and rats, and this compound also showed inhibitory effects on GnRH-mediated signaling pathways. Pharmacokinetic and pharmacodynamic evaluations of 18a revealed improved bioavailability and superior gonadotropic suppression activity compared with Elagolix, the most clinically advanced compound. Considering that 18a exhibited highly potent and selective antagonistic activity toward the hGnRHRs along with favorable pharmacokinetic profiles, we believe that 18a may represent a promising candidate for an orally available hormonal therapy.

Elagolix, a novel, orally bioavailable GnRH antagonist under investigation for the treatment of endometriosis-related pain

Suppression of estrogen production and reduction of menstrual blood flow are the mainstays of medical treatment of endometriosis-related pain and have been traditionally achieved by methods such as combined hormonal contraception, progestins and GnRH analogs, all with comparable efficacies, though different side-effect profiles. Elagolix is the frontrunner among an emerging class of GnRH antagonists, which unlike their peptide predecessors has a nonpeptide structure resulting in its oral bioavailability. Phase I and II clinical trials have demonstrated safety of elagolix and its efficacy in partial and reversible suppression of ovarian estrogen production resulting in improvements in endometriosis-related pain. Phase III clinical trials are currently underway and elagolix may become a valuable addition to the armamentarium of pharmacological agents to treat endometriosis-related pain.

Pd-Catalyzed Dehydrogenative Cross-Coupling of 1,4-Quinones with N,N′-Dialkyluracils

A straightforward and efficient method for the palladium-catalyzed direct cross-coupling of quinones with N,N′-dialkyluracils via 2-fold C–H activation has been developed to rapidly construct uracil substituted quinone structural motifs.

Palladium-catalyzed direct arylation of 5-halouracils and 5-halouracil nucleosides with arenes and heteroarenes promoted by TBAF

The 1-N-benzyl-5-iodo(or bromo)uracil undergoes Pd-catalyzed [Pd₂(dba)₃] direct arylation with benzene and other simple arenes in the presence of TBAF in DMF without the necessity of adding any ligands or additives to give 5-arylated uracil analogues. The TBAF-promoted coupling also occurs efficiently with electron rich heteroarenes at 100 °C (1 h) even with only small excess of heteroarenes. The protocol avoids usage of the arylboronic acid or stannane precursors for the synthesis of 5-(2-furyl, or 2-thienyl, or 2-pyrrolyl)uracil nucleosides, which are used as important RNA and DNA fluorescent probes. The fact that 1-N-benzyl-3-N-methyl-5-iodouracil did not undergo the TBAF-promoted couplings with arenes or heteroarenes suggests that the C4-alkoxide (enol form of uracil) facilitates coupling by participation in the intramolecular processes of hydrogen abstraction from arenes. TBAF-promoted arylation was extended into the other enolizable heterocyclic systems such as 3-bromo-2-pyridone. The π-excessive heteroarenes also coupled with 5-halouracils in the presence of Pd(OAc)₂/Cs₂CO₃/PivOH combination in DMF (100 °C, 2 h) to yield 5-arylated uracils.

Original access to 5-aryluracils from 5-iodo-2′-deoxyuridine via a microwave assisted Suzuki-Miyaura cross-coupling/deglycosylation sequence in pure water

A facile and efficient methodology to obtain various 5-aryluracil derivatives was developed through a two steps sequence: a ligand-free Suzuki-Miyaura cross-coupling reaction starting from totally deprotected 5-iodo-(2′-deoxy)uridine followed by a very simple deglycosylation procedure in pure water with assistance of microwave irradiation.

Pd(II)-catalyzed ortho-trifluoromethylation of benzylamines

The Pd(II)-catalyzed ortho-C-H trifluoromethylation of benzylamines has been achieved utilizing an electrophilic CF3 reagent. Additives, such as H2O and Ag2O, were found to be crucial for obtaining good yields. This protocol will be useful in medicinal chemistry for the preparation of ortho-trifluoromethyl-substituted benzylamines.

Current and future applications of GnRH, kisspeptin and neurokinin B analogues

Reproductive hormones affect all stages of life from gamete production, fertilization, fetal development and parturition, neonatal development and puberty through to adulthood and senescence. The reproductive hormone cascade has, therefore, been the target for the development of numerous drugs that modulate its activity at many levels. As the central regulator of the cascade, gonadotropin-releasing hormone (GnRH) agonists and antagonists have found extensive applications in treating a wide range of hormone-dependent diseases, such as precocious puberty, prostate cancer, benign prostatic hyperplasia, endometriosis and uterine fibroids, as well as being an essential component of in vitro fertilization protocols. The neuroendocrine peptides that regulate GnRH neurons, kisspeptin and neurokinin B, have also been identified as therapeutic targets, and novel agonists and antagonists are being developed as modulators of the cascade upstream of GnRH. Here, we review the development and applications of analogues of the major neuroendocrine peptide regulators of the reproductive hormone cascade: GnRH, kisspeptin and neurokinin B.

Dehydrogenative alkenylation of uracils via palladium-catalyzed regioselective C-H activation

A regioselective Pd-catalyzed cross-dehydrogenative coupling between uracils and alkenes is reported. This protocol provides easy access to a variety of 5-alkenyluracil structural motifs.

GnRH receptors in cancer: from cell biology to novel targeted therapeutic strategies

The crucial role of pituitary GnRH receptors (GnRH-R) in the control of reproductive functions is well established. These receptors are the target of GnRH agonists (through receptor desensitization) and antagonists (through receptor blockade) for the treatment of steroid-dependent pathologies, including hormone-dependent tumors. It has also become increasingly clear that GnRH-R are expressed in cancer tissues, either related (i.e. prostate, breast, endometrial, and ovarian cancers) or unrelated (i.e. melanoma, glioblastoma, lung, and pancreatic cancers) to the reproductive system. In hormone-related tumors, GnRH-R appear to be expressed even when the tumor has escaped steroid dependence (such as castration-resistant prostate cancer). These receptors are coupled to a G(αi)-mediated intracellular signaling pathway. Activation of tumor GnRH-R by means of GnRH agonists elicits a strong antiproliferative, antimetastatic, and antiangiogenic (more recently demonstrated) activity. Interestingly, GnRH antagonists have also been shown to elicit a direct antitumor effect; thus, these compounds behave as antagonists of GnRH-R at the pituitary level and as agonists of the same receptors expressed in tumors. According to the ligand-induced selective-signaling theory, GnRH-R might assume various conformations, endowed with different activities for GnRH analogs and with different intracellular signaling pathways, according to the cell context. Based on these consistent experimental observations, tumor GnRH-R are now considered a very interesting candidate for novel molecular, GnRH analog-based, targeted strategies for the treatment of tumors expressing these receptors. These agents include GnRH agonists and antagonists, GnRH analog-based cytotoxic (i.e. doxorubicin) or nutraceutic (i.e. curcumin) hybrids, and GnRH-R-targeted nanoparticles delivering anticancer compounds.

The extrapituitary effects of GnRH antagonists and their potential clinical implications: a narrated review

Potential roles of gonadotropin-releasing hormone (GnRH) antagonists on GnRH/GnRH receptor systems and their effects on the extrapituitary tissues are largely elusive. In this narrated review, we summarized the systemic effects of GnRH antagonists on ovary, endometrium, embryo implantation, placental development, fetal teratogenicity, reproductive tissue cancer cells, and heart while briefly reviewing the GnRH and GnRH receptor system. GnRH antagonists may have direct effects on ovarian granulosa cells. Data are conflicting regarding their effects on endometrial receptivity. The GnRH antagonists may potentially have detrimental effect on early placentation by decreasing the invasive ability of cytotrophoblasts if the exposure to them occurs during early pregnancy. The GnRH antagonists were not found to increase the rates of congenital malformations. Comparative clinical data are required to explore their systemic effects on various extrapituitary tissues such as on cardiac function in the long term as well as their potential use in other human cancers that express GnRH receptors.

Innovative oral treatments of uterine leiomyoma

Uterine fibroids (leiomyoma), the benign tumors of the uterine wall, are very common cause of morbidity in reproductive age women usually in the form of excessive vaginal bleeding, chronic pelvic pain, miscarriage and infertility. These tumors are the leading indication for hysterectomy in the United States. Uterine fibroids are about 4 times higher in blacks compared to whites and constitute a major health disparity challenge. The estimated cost of uterine fibroids is up to $34.4 billion annually. Additionally, women who suffer from this disease and desire to maintain their future fertility have very limited treatment choices. Currently, there is no effective long-term medicinal treatment for uterine fibroids. While surgery has traditionally been the gold standard for the treatment of uterine fibroids, there is growing interest towards orally administered medications for the management of leiomyoma-related symptoms. In this paper, we will discuss these promising innovative oral medical treatments in detail.

Discovery of 1-{4-[1-(2,6-difluorobenzyl)-5-[(dimethylamino)methyl]-3-(6-methoxypyridazin-3-yl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]pyrimidin-6-yl]phenyl}-3-methoxyurea (TAK-385) as a potent, orally active, non-peptide antagonist of the human gonadotropin-releasing hormone receptor

We previously discovered an orally active human gonadotropin-releasing hormone (GnRH) receptor antagonist, thieno[2,3-d]pyrimidine-2,4-dione derivative 1 (sufugolix). To reduce the cytochrome P450 (CYP) inhibitory activity and improve in vivo GnRH antagonistic activity, further optimization of this scaffold was carried out. We focused our synthetic efforts on chemical modification at the 5 and 3 positions of the thieno[2,3-d]pyrimidine-2,4-dione ring based on computational modeling, which resulted in the discovery of 1-{4-[1-(2,6-difluorobenzyl)-5-[(dimethylamino)methyl]-3-(6-methoxypyridazin-3-yl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]pyrimidin-6-yl]phenyl}-3-methoxyurea (16b) as a highly potent and orally active GnRH antagonist. Compound 16b showed potent in vitro GnRH antagonistic activity in the presence of fetal bovine serum (FBS) without CYP inhibition. Oral administration of 16b maintained the suppressive effect of the plasma luteinizing hormone levels in castrated cynomolgus monkeys at a 3 mg/kg dose for more than 24 h. Compound 16b is currently under clinical development with the code name of TAK-385.

Luteinizing hormone-releasing hormone antagonists

BACKGROUND

Luteinizing hormone-releasing hormone (LH-RH) plays a central role in the vertebrate reproduction by regulating gonadal activity. Based on its binding to pituitary LH-RH receptors, as well as to LH-RH receptors expressed on cancer cells, LH-RH agonists and antagonists have been developed for different therapeutic applications.

OBJECTIVE/METHOD

Here we give an overview of the most relevant LH-RH antagonists and their therapeutic applications. Recently patented compounds as well as drug formulations and dosage are presented.

CONCLUSION

LH-RH antagonists have found clinical applications in in vitro fertilization, benign prostatic hyperplasia, endometriosis and in the treatment of hormone-dependent tumors. Work in progress is focused on further development of both peptidic and orally active non-peptidic LH-RH antagonists.

Suppression of gonadotropins and estradiol in premenopausal women by oral administration of the nonpeptide gonadotropin-releasing hormone antagonist elagolix

CONTEXT

Parenteral administration of peptide GnRH analogs is widely employed for treatment of endometriosis and fibroids and in assisted-reproductive therapy protocols. Elagolix is a novel, orally available nonpeptide GnRH antagonist.

OBJECTIVE

Our objective was to evaluate the safety, pharmacokinetics, and inhibitory effects on gonadotropins and estradiol of single-dose and 7-d elagolix administration to healthy premenopausal women.

DESIGN

This was a first-in-human, double-blind, placebo-controlled, single- and multiple-dose study with sequential dose escalation.

PARTICIPANTS

Fifty-five healthy, regularly cycling premenopausal women participated.

INTERVENTIONS

Subjects were administered a single oral dose of 25-400 mg or placebo. In a second arm of the study, subjects received placebo or 50, 100, or 200 mg once daily or 100 mg twice daily for 7 d. Treatment was initiated on d 7 (+/-1) after onset of menses.

MAIN OUTCOME MEASURES

Safety, tolerability, pharmacokinetics, and serum LH, FSH, and estradiol concentrations were assessed.

RESULTS

Elagolix was well tolerated and rapidly bioavailable after oral administration. Serum gonadotropins declined rapidly. Estradiol was suppressed by 24 h in subjects receiving at least 50 mg/d. Daily (50-200 mg) or twice-daily (100 mg) administration for 7 d maintained low estradiol levels (17 +/- 3 to 68 +/- 46 pg/ml) in most subjects during late follicular phase. Effects of the compound were rapidly reversed after discontinuation.

CONCLUSIONS

Oral administration of a nonpeptide GnRH antagonist, elagolix, suppressed the reproductive endocrine axis in healthy premenopausal women. These results suggest that elagolix may enable dose-related pituitary and gonadal suppression in premenopausal women as part of treatment strategies for reproductive hormone-dependent disease states.