Fezolinetant: a novel nonhormonal therapy for vasomotor symptoms due to menopause.

INTRODUCTION: During menopause, the majority of women experience vasomotor symptoms which may lead to several untoward effects and negatively impact quality of life. Fezolinetant, a novel agent directly targeting the underlying pathophysiology of menopause-associated vasomotor symptoms, offers an alternative to hormonal therapies for which many patients have a contraindication or unwillingness to take due to safety concerns. AREAS COVERED: This review summarizes key pharmacologic, pharmacokinetic, and pharmacodynamic parameters of fezolinetant along with efficacy and safety data derived from clinical trials. A literature search of peer-reviewed publications evaluating the efficacy and safety of fezolinetant was conducted using PubMed and EMBASE databases. A review of registered trials in clinicaltrials.gov was evaluated to identify ongoing studies. EXPERT OPINION: Placebo-controlled studies demonstrated that fezolinetant led to a statistically significant reduction in vasomotor symptom frequency and severity among patients with moderate-to-severe vasomotor symptoms. The most common adverse event is headache (5-10%) and no serious safety signals have been noted. Direct head-to-head comparison with hormonal therapies and nonhormonal therapies for vasomotor symptoms, assessment of sleep outcomes, and evaluation of efficacy and safety beyond 1 year are key areas where additional data are still needed.

Are the promnestic effects of neurokinin 3 receptor mediated by hippocampal neurogenesis in a Aß-induced rat model of Alzheimer's disease?

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterised by cognitive dysfunction, memory loss and mood changes. Hippocampal neurogenesis has been suggested to play a role in learning and memory. Neurokinin 3 receptor (NK3R) has been shown to be prevalent in the hippocampus region. The aim of the project was to investigate the role of hippocampal neurogenesis in the promnestic effects of NK3R agonist administration in an amyloid beta-induced AD rat model. Wistar albino rats were divided into control, Alzheimer, NK3R agonist and Alzheimer + NK3R agonist groups. The open field (OF) test and Morris water maze (MWM) test were performed for locomotor activity and memory analysis. Peptide gene expression levels (Nestin, DCX, Neuritin, MASH1, Neun, BDNF) were analysed by quantitative reverse transcription polymerase chain reaction (RT-PCR). In the OF test, the group-time relationship was found to be statistically different in the parameters of distance travelled and percentage of movement (p < 0.05). In MWM, the time to reach the platform and the time spent in the target quadrant were statistically significant between the groups (p < 0.05). Statistically significant differences were observed in gene expression levels (Nestin, DCX, Neuritin, MASH1) in the hippocampal tissue of rats between the groups (p < 0.05). NK3 receptor agonism favourably affected hippocampal neurogenesis in AD model rats. It was concluded that NK3 receptor agonism in the hippocampus, which is the first affected region in the physiopathology of AD, may be effective in both the formation of neural precursor cells and the reduction of neuronal degeneration. The positive effect of NK3R on cognitive functions may be mediated by hippocampal neurogenesis.

Efficacy and safety of fezolinetant for moderate to severe vasomotor symptoms associated with menopause among women in East Asia: a phase 3 randomized study (MOONLIGHT I).

OBJECTIVE: To evaluate the efficacy and safety of fezolinetant for moderate to severe vasomotor symptoms (VMS) associated with menopause in East Asian women. METHODS: In this phase 3, randomized, double-blind study, postmenopausal women with moderate to severe VMS (minimum average frequency in the 10 days before randomization, ≥7/day or 50/week) received fezolinetant 30 mg/day or placebo (weeks 1-12), followed by an open-label extension phase with fezolinetant 30 mg/day (weeks 13-24). The co-primary endpoints were the mean changes in the daily frequency and severity of VMS at weeks 4 and 12. RESULTS: Among 301 participants, the difference in the least squares mean change (95% confidence interval) from baseline in the daily frequency of moderate to severe VMS versus placebo was -0.65 (-1.41 to 0.12) at week 4 and -0.55 (-1.35 to 0.26) at week 12. The differences in the least squares mean change from baseline in the VMS severity score versus placebo were -0.06 (-0.14 to 0.03) and -0.13 (-0.27 to 0.01) at weeks 4 and 12, respectively. Serious adverse events occurred in 0.7% of participants receiving fezolinetant in weeks 1 to 12, compared with 1.3% of those receiving placebo. CONCLUSIONS: Fezolinetant was generally safe but did not reduce the frequency or severity of VMS versus placebo in postmenopausal women in this study.ClinicalTrials.Gov Identifier: NCT04234204.

Long-term safety of fezolinetant in Chinese women with vasomotor symptoms associated with menopause: the phase 3 open-label MOONLIGHT 3 clinical trial.

OBJECTIVE: We aimed to assess long-term safety and tolerability of fezolinetant, a nonhormonal neurokinin 3 receptor antagonist, among Chinese women with vasomotor symptoms associated with menopause participating in the MOONLIGHT 3 trial. METHODS: In this phase 3 open-label study, women in menopause aged 40-65 years received fezolinetant 30 mg once daily for 52 weeks. The primary endpoint was frequency and severity of treatment-emergent adverse events (TEAEs), assessed at every visit through week 52 and one follow-up visit at week 55. RESULTS: Overall, 150 women were enrolled (mean age, 54 years) and 105 completed treatment. The frequency of TEAEs was 88.7%. Most TEAEs were mild (63.3%) or moderate (22.7%). The most common TEAE was upper respiratory tract infection (16.0%), followed by dizziness, headache, and protein urine present (10.7% each). There was no clinically relevant change (mean ± standard deviation) in endometrial thickness (baseline, 2.95 ± 1.11 mm; week 52, 2.94 ± 1.18 mm). Alanine aminotransferase and/or aspartate aminotransferase levels >3 times the upper limit of normal were reported in 1.4% of women; no Hy's Law cases occurred. CONCLUSIONS: Fezolinetant 30 mg once daily was generally safe and well tolerated over a 52-week period among women in China with vasomotor symptoms associated with menopause.ClinicalTrials.gov Identifier: NCT04451226.

Effectiveness and safety of fezolinetant in alleviating vasomotor symptoms linked to Menopause.: A systematic review and Meta-Analysis.

BACKGROUND & OBJECTIVE: Vasomotor symptoms (VMS) are the most common symptoms during menopause including hot flushes and night sweats. They are highly disruptive to the quality of life. Fezolinetant is an FDA-approved non-hormonal selective neurokinin3 receptor antagonist for the treatment of VMS. In this study, we aim to assess the efficacy and safety of fezolinetant for VMS associated with menopause. METHODS: Databases were searched until September 2023 for relevant studies comparing fezolinetant against placebo. Data was extracted into an online form and analyzed using RevMan (Version 5.4.1). The GRADE approach was conducted to evaluate the quality of evidence regarding efficacy outcomes. We included randomized controlled trials (RCTs) comparing fezolinetant to placebo in postmenopausal women experiencing VMS. Exclusion criteria comprised studies involving participants with contraindications to fezolinetant or those evaluating its efficacy for indications other than VMS associated with menopause. RESULTS: Six studies were included in this study involving 3301 patients. Compared to placebo, fezolinetant reduced the frequency of VMS episodes from baseline (SMD = -0.64, 95 % CI [-0.77, -0.5]) and (SMD = -0.63, 95 % CI [-0.72, -0.53] at weeks 4 and 12 respectively. Additionally, fezolinetant reduced VMS severity score (SMD = -0.59, 95 %CI [-0.77, -0.42]) and (SMD = -0.4, 95 % CI [-0.54, -0.27]) at weeks 4 at 12 respectively. These reductions were positively reflected on Menopause specific quality of life score (SMD = -0.46, 95 %CI [-57, -0.34]), (SMD = -0.37, 95 %CI [-0.48, -0.25]) at weeks 4 and 12 respectively. Regarding safety analysis, fezolinetant showed increased risk for drug-related TEAEs (RR = 1.47, 95 %CI [1.06,2.04]), serious TEAEs (RR = 1.67, 95 %CI [1.09,2.55]), fatigue (RR = 4.05, 95 %CI [1.27,12.88]), arthralgia (RR = 2.83, 95 %CI [1.02,7.8]) and ALT or AST > 3 times (RR = 2, 95 %CI [1.12,3.57]), with no other statistically significant difference regarding other safety terms. CONCLUSION: Fezolinetant has demonstrated efficacy in reducing the frequency and severity of VMS in postmenopausal women, leading to an improvement in their quality of life. These findings suggest that Fezolinetant may serve as a viable alternative to hormonal therapy for managing VMS.

Fezolinetant for the treatment of vasomotor symptoms associated with menopause: a meta-analysis.

This systematic review and meta-analysis investigated the efficacy and safety of fezolinetant for the treatment of moderate-to-severe vasomotor symptoms (VMS) associated with menopause. PubMed, Cochrane Library, Embase and Web of Science were searched for randomized controlled trials (RCTs) published from inception to June 2023, comparing fezolinetant to placebo in postmenopausal women suffering from moderate-to-severe VMS. The mean difference and risk ratio were calculated for continuous and binary outcomes, respectively. R software was used for the statistical analysis, and RoB-2 (Cochrane) to assess the risk of bias. We performed subgroup analysis based on different dosing regimens. Five RCTs comprising 3302 patients were included. Compared with placebo, at 12-week follow-up, fezolinetant significantly reduced the daily frequency of moderate-to-severe VMS (weighted mean difference [WMD] - 2.36; 95% confidence interval [CI] - 2.92, -1.81) and daily severity of moderate-to-severe VMS (WMD -0.22; 95% CI -0.31, -0.13). Also, fezolinetant significantly improved the quality of life (WMD -0.42; 95% CI -0.58, -0.26) and sleep disturbance (WMD -1.10; 95% CI -1.96, -0.24). There were no significant differences between groups in adverse events. These findings support the efficacy and safety of fezolinetant for the treatment of VMS related to menopause.

Neuroanatomical, electrophysiological, and morphological characterization of melanin-concentrating hormone cells coexpressing cocaine- and amphetamine-regulated transcript.

Melanin-concentrating hormone (MCH) cells in the hypothalamus regulate fundamental physiological functions like energy balance, sleep, and reproduction. This diversity may be ascribed to the neurochemical heterogeneity among MCH cells. One prominent subpopulation of MCH cells coexpresses cocaine- and amphetamine-regulated transcript (CART), and as MCH and CART can have opposing actions, MCH/CART+ and MCH/CART- cells may differentially modulate behavioral outcomes. However, it is not known if there are differences in the cellular properties underlying their functional differences; thus, we compared the neuroanatomical, electrophysiological, and morphological properties of MCH cells in male and female Mch-cre;L10-Egfp reporter mice. Half of MCH cells expressed CART and were most prominent in the medial hypothalamus. Whole-cell patch-clamp recordings revealed differences in their passive and active membrane properties in a sex-dependent manner. Female MCH/CART+ cells had lower input resistances, but male cells largely differed in their firing properties. All MCH cells increased firing when stimulated, but their firing frequency decreases with sustained stimulation. MCH/CART+ cells showed stronger spike rate adaptation than MCH/CART- cells. The kinetics of excitatory events at MCH cells also differed by cell type, as the rising rate of excitatory events was slower at MCH/CART+ cells. By reconstructing the dendritic arborization of our recorded cells, we found no sex differences, but male MCH/CART+ cells had less dendritic length and fewer branch points. Overall, distinctions in topographical division and cellular properties between MCH cells add to their heterogeneity and help elucidate their response to stimuli or effect on modulating their respective neural networks.

Fezolinetant impact on health-related quality of life for vasomotor symptoms due to the menopause: Pooled data from SKYLIGHT 1 and SKYLIGHT 2 randomised controlled trials.

OBJECTIVE: To assess the effect of fezolinetant treatment on health-related quality of life using pooled data from SKYLIGHT 1 and 2 studies. DESIGN: Prespecified pooled analysis. SETTING: USA, Canada, Europe; 2019-2021. POPULATION: 1022 women aged ≥40 to ≤65 years with moderate-to-severe vasomotor symptoms (VMS; minimum average seven hot flushes/day), seeking treatment for VMS. METHODS: Women were randomised to 12-week double-blind treatment with once-daily placebo or fezolinetant 30 or 45 mg. Completers entered a 40-week, active extension (those receiving fezolinetant continued that dose; those receiving placebo re-randomised to fezolinetant received 30 or 45 mg). MAIN OUTCOME MEASURES: Mean changes from baseline to weeks 4 and 12 on Menopause-Specific Quality of Life (MENQoL) total and domain scores, Work Productivity and Activity Impairment questionnaire specific to VMS (WPAI-VMS) domain scores, Patient Global Impression of Change in VMS (PGI-C VMS); percentages achieving PGI-C VMS of 'much better' (PGI-C VMS responders). Mean reduction was estimated using mixed model repeated measures analysis of covariance. RESULTS: Fezolinetant 45 mg mean reduction over placebo in MENQoL total score was -0.57 (95% confidence interval [CI] -0.75 to -0.39) at week 4 and -0.47 (95% CI -0.66 to -0.28) at week 12. Reductions were similar for 30 mg. MENQoL domain scores were also reduced and WPAI-VMS scores improved. Twice as many women receiving fezolinetant reported VMS were 'much better' than placebo based on PGI-C VMS assessment. CONCLUSIONS: Fezolinetant treatment was associated with improvement in overall QoL, measured by MENQoL, and work productivity, measured by WPAI-VMS. A high proportion receiving fezolinetant felt VMS were 'much better' based on PGI-C VMS responder analysis.

New advances in menopause symptom management.

Vasomotor symptoms (VMS) are characteristic of menopause experienced by over 75% of postmenopausal women with significant health and socioeconomic implications. Although the average duration of symptoms is seven years, 10% of women experience symptoms for more than a decade. Although menopausal hormone therapy (MHT) remains an efficacious and cost-effective treatment, its use may not be suitable in all women, such as those at an increased risk of breast cancer or gynaecological malignancy. The neurokinin B (NKB) signaling pathway, together with its intricate connection to the median preoptic nucleus (MnPO), has been postulated to provide integrated reproductive and thermoregulatory responses, with a central role in mediating postmenopausal VMS. This review describes the physiological hypothalamo-pituitary-ovary (HPO) axis, and subsequently the neuroendocrine changes that occur with menopause using evidence derived from animal and human studies. Finally, data from the latest clinical trials using novel therapeutic agents that antagonise NKB signaling are reviewed.

Tachykinin Receptor-Selectivity of the Potential Glioblastoma-Targeted Therapy, DOTA-[Thi8,Met(O2)11]-Substance P.

Radiopharmaceutical development hinges on the affinity and selectivity of the biological component for the intended target. An analogue of the neuropeptide Substance P (SP), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-[Thi8,Met(O2)11]-SP (DOTA-[Thi8,Met(O2)11]SP), in the theranostic pair [68Ga]Ga-/ [213Bi]Bi-DOTA-[Thi8,Met(O2)11]SP has shown promising clinical results in the treatment of inoperable glioblastoma. As the theranostic targeting component, modifications to SP that affect the selectivity of the resulting analogue for the intended target (neurokinin-1 receptor [NK1R]) could be detrimental to its therapeutic potential. In addition to other closely related tachykinin receptors (neurokinin-2 receptor [NK2R] and neurokinin-3 receptor [NK3R]), SP can activate a mast cell expressed receptor Mas-related G protein-coupled receptor subtype 2 (MRGPRX2), which has been implicated in allergic-type reactions. Therefore, activation of these receptors by SP analogues has severe implications for their therapeutic potential. Here, the receptor selectivity of DOTA-[Thi8,Met(O2)11]SP was examined using inositol phosphate accumulation assay in HEK293-T cells expressing NK1R, NK2R, NK3R or MRGPRX2. DOTA-[Thi8,Met(O2)11]SP had similar efficacy and potency as native SP at NK1R, but displayed greater NK1R selectivity. DOTA-[Thi8,Met(O2)11]SP was unable to elicit significant activation of the other tachykinin receptors nor MRGPRX2 at high concentrations nor did it display antagonistic behaviour at these receptors. DOTA-[Thi8,Met(O2)11]SP, therefore has high potency and selectivity for NK1R, supporting its potential for targeted theranostic use in glioblastoma multiforme and other conditions characterised by NK1R overexpression.

Efficacy and Safety of Fezolinetant in Moderate to Severe Vasomotor Symptoms Associated With Menopause: A Phase 3 RCT.

CONTEXT: Vasomotor symptoms (VMS) are common, bothersome, and can persist for years before and after menopause. OBJECTIVE: We aimed to assess efficacy/safety of fezolinetant for treatment of moderate to severe VMS associated with menopause. METHODS: In this double-blind, placebo-controlled, 12-week phase 3 trial with a 40-week active treatment extension (NCT04003142; SKYLIGHT 2), women aged 40 to 65 years with minimum average 7 moderate to severe VMS/day were randomized to 12 weeks of once-daily placebo, fezolinetant 30 mg, or fezolinetant 45 mg. Completers were rerandomized to fezolinetant 30/45 mg for 40 additional weeks. Coprimary efficacy endpoints were mean daily change from baseline to week 4 (W4) and W12 in VMS frequency and severity. Safety was also assessed. RESULTS: Both fezolinetant doses statistically significantly reduced VMS frequency/severity at W4 and W12 vs placebo. For VMS frequency, W4 least squares mean (SE) reduction vs placebo: fezolinetant 30 mg, -1.82 (0.46; P < .001); 45 mg, -2.55 (0.46; P < .001); W12: 30 mg, -1.86 (0.55; P < .001); 45 mg, -2.53 (0.55; P < .001). For VMS severity, W4: 30 mg, -0.15 (0.06; P < .05); 45 mg, -0.29 (0.06; P < .001); W12: 30 mg, -0.16 (0.08; P < .05); 45 mg, -0.29 (0.08; P < .001). Improvement in VMS frequency and severity was observed by W1 and maintained through W52. Serious treatment-emergent adverse events were infrequent, reported by 2%, 1%, and 0% of those receiving fezolinetant 30 mg, fezolinetant 45 mg, and placebo, respectively. CONCLUSION: Daily fezolinetant 30 and 45 mg were efficacious and well tolerated for treating moderate to severe VMS associated with menopause.

How does neurokinin 3 receptor agonism affect pathological and cognitive impairments in an Alzheimer's disease-like rat model?

Alzheimer's disease (AD) is accepted as a form of progressive dementia. Cholinergic systems are commonly affected in AD. Neurokinin 3 receptor (NK3R) is involved in learning memory-related processes. It is known that the activation of NK3R affects the release of many neurotransmitters. The aim of this project was to investigate the effects of NK3R agonist senktide administration on neurobehavioral mechanisms in the experimental AD-like rat model. 50 male Wistar albino rats were divided into Control (C), AD, Control + NK3R agonist (CS), AD + NK3R agonist (ADS), AD + NK3Ragonist + antagonist groups (ADSO). We designed AD-like model by intrahippocampal administration of Aß1-42. After NK3R agonist + antagonist injections, open field (OF), Morris water maze (MWM) tests were applied. Cholinergic mechanism analysis from hippocampus-cortex tissues was performed by ELISA and catecholamine analysis from brain stem tissue were performed by HPLC method. The transitions from edge to center, rearing, grooming parameters were found to be reduced in final values of OF. While the group-time interaction was significant in the OF test findings, there was no significant difference between the groups. In MWM test, ADS group showed a learning level close to control group and animals in AD and ADSO groups could not learn target quadrant in MWM test. The brain stem NA and DA concentrations were not statistically significant. Hippocampal AChE-ChAT levels were supported by positive effects of senktide on learning via the cholinergic mechanisms. As a result, NK3R agonists were found to be effective in improving cognitive functions in rats with AD pathology. In the experimental AD model, positive effects of NK3R on learning memory may be mediated by cholinergic mechanisms.

The overexpression of neurokinin B-neurokinin 3 receptor system exerts direct effects on the ovary under PCOS-like conditions to interfere with mitochondrial function.

PROBLEM: The increased hypothalamic neurokinin B (NKB) level may contribute to the hyperactive LH pulse secretion in Polycystic ovary syndrome (PCOS). However, the expression and role of the neurokinin B-neurokinin 3 receptor (NKB-NK3R) system in the local ovarian tissue of PCOS have not been clarified. We constructed in vivo and in vitro models to elucidate the mechanism of the NKB-NK3R pathway in reproductive endocrine disorders of PCOS. METHOD OF STUDY: The granulosa cell line-KGN cells were set in palmitic acid (PA) and dihydrotestosterone (DHT) to simulate the PCOS-like conditions. And we used the high-fat/high-glucose diet to build a PCOS-like mice model and neurokinin 3 receptor antagonist (NK3Ra) was administered to half of the mice. The expression of the NKB-NK3R system, mitochondrial functions, hormone levels, and inflammatory state was evaluated. RESULTS: The PCOS-like stimulations induced the NKB-NK3R system and MAPK-ERK pathway overexpression in KGN cells, in an approximate dose and time-dependent manner. The NKB-NK3R system overactivated the MAPK-ERK pathway to increase NNT overexpression, disturb NADH/NADPH pools, aggravate the oxidation state, and decrease ATP production. With overexpression of the NKB-NK3R system in the local ovarian tissue, ovulatory dysfunction, progesterone deficiency, and pro-inflammatory states were apparent in PCOS-like mice. Antagonizing the receptor, NK3R, reversed the adverse reproductive endocrine phenotypes via improving mitochondrial dysfunction. CONCLUSIONS: In addition to the central regulation, local ovarian overexpression of the NKB-NK3R system participated in the adverse reproductive endocrine phenotypes, supporting the therapeutic implications of NK3Ra for PCOS.

Fezolinetant: A Potential Treatment for Moderate to Severe Vasomotor Symptoms of Menopause.

The most common symptom of menopause is vasomotor symptoms (VMS), which occur in more than 80% of postmenopausal women. Furthermore, VMS are the manifestation of menopause for which women most commonly seek treatment, namely, to address their impacted quality of life, including sleep, and work-and non-work-related productivity. VMS vary in frequency, intensity and duration. Hormone therapy (HT) has been our most effective treatment for VMS and has been approved for this indication by the United States Food and Drug Administration (FDA). Despite being a safe and effective treatment option, many patients and providers are hesitant to consider HT. Moreover, HT is contraindicated for some women. While many over-the-counter and non-HT options are available, we lack data on the efficacy and safety of most of these. This has left a void for women. Fezolinetant was recently approved by the FDA for the treatment of moderate-to-severe VMS. So far, clinical trials have shown positive results in terms of safety and efficacy. Fezolinetant is a non-hormonal, neurokinin 3 receptor antagonist that works in the hypothalamus at the thermoregulatory centre. Blocking the non-hormonal neurokinin 3 receptor antagonist modulates hot flashes and night sweats. As early as 4 weeks from initiating fezolinetant, women experienced a statistically significant reduction of both severity and frequency of VMS per day, resulting in an improved quality of life.

Nk3R blockade has sex-divergent effects on memory in mice.

BACKGROUND: Memory consolidation is a process required for the formation of long-term memories. The G-protein-coupled receptor (GPCR) neurokinin-3-receptor (Nk3R) and its interactions with sex hormones seem important for the modulation of fear memory consolidation: Nk3R antagonism in male mice impairs fear memory, but enhances it in females. However, the involvement of the Nk3R as a modulator of other memories in both sexes remains unexplored. METHODS: We use the novel object recognition paradigm to test the effect of a systemic blockade of Nk3R during memory consolidation. Further, we assess the expression of estrogen receptor α, estrogen receptor ß, and androgen receptor and heterodimerization with Nk3R in the medial prefrontal cortex (mPFC) and dorsal hippocampus (DH) of mice. RESULTS: Nk3R systemic antagonism elicited decreased memory consolidation in males while it enhanced it in females during proestrus. Nk3R analysis in the different subregions of the mPFC and the DH showed a higher expression in males than females. Moreover, females presented upregulation of the androgen receptor in the CA1 and the estrogen receptor beta in the cingulate cortex, CA1, and dentate gyrus. Overall, males presented an upregulation of the estrogen receptor alpha. We also explored the heterodimerization of GCPR membrane sex hormone receptors with the Nk3R. We found a higher percentage of Nk3R-membrane G-protein estrogen receptors heterodimers in the prelimbic cortex of the mPFC in females, suggesting an interaction of estradiol with Nk3R in memory consolidation. However, males presented a higher percentage of Nk3R-membrane G-protein androgen receptors heterodimers compared to females, pointing to an interaction of testosterone with Nk3R in memory consolidation. CONCLUSION: These data propose novel ideas on functional interactions between Nk3R, sex hormones, estrogen receptors, and androgen receptors in memory consolidation.

Functional Rescue of Inactivating Mutations of the Human Neurokinin 3 Receptor Using Pharmacological Chaperones.

G protein-coupled receptors (GPCRs) facilitate the majority of signal transductions across cell membranes in humans, with numerous diseases attributed to inactivating GPCR mutations. Many of these mutations result in misfolding during nascent receptor synthesis in the endoplasmic reticulum (ER), resulting in intracellular retention and degradation. Pharmacological chaperones (PCs) are cell-permeant small molecules that can interact with misfolded receptors in the ER and stabilise/rescue their folding to promote ER exit and trafficking to the cell membrane. The neurokinin 3 receptor (NK3R) plays a pivotal role in the hypothalamic-pituitary-gonadal reproductive axis. We sought to determine whether NK3R missense mutations result in a loss of cell surface receptor expression and, if so, whether a cell-permeant small molecule NK3R antagonist could be repurposed as a PC to restore function to these mutants. Quantitation of cell surface expression levels of seven mutant NK3Rs identified in hypogonadal patients indicated that five had severely impaired cell surface expression. A small molecule NK3R antagonist, M8, increased cell surface expression in four of these five and resulted in post-translational receptor processing in a manner analogous to the wild type. Importantly, there was a significant improvement in receptor activation in response to neurokinin B (NKB) for all four receptors following their rescue with M8. This demonstrates that M8 may have potential for therapeutic development in the treatment of hypogonadal patients harbouring NK3R mutations. The repurposing of existing small molecule GPCR modulators as PCs represents a novel and therapeutically viable option for the treatment of disorders attributed to mutations in GPCRs that cause intracellular retention.

Menopause review: Emerging treatments for menopausal symptoms.

Vasomotor symptoms (VMS) affect 2 out of 3 women during menopause and are highly disruptive and intolerable. They exert a negative impact on a woman's physical and mental well-being and are considered a high clinical priority requiring effective treatment. Although hormone therapy remains the gold-standard treatment for hot flushes, it is associated with several side effects and contraindications. Furthermore, alternative treatments for VMS are currently less efficacious and have limited availability; therefore, a new medication to treat VMS would benefit millions of women worldwide. Neurokinin 3 receptor (NK3R) antagonists have recently been developed as novel therapeutic agents for the amelioration of VMS through their action on NK3 receptors within the hypothalamus and consequent regulation of the thermoregulatory centre. So far, three NK3R antagonists have been studied in menopausal women, which have demonstrated significant reductions in VMS frequency and severity and have shown their ability to transform patients' quality of life.

Hypothalamic neurokinin signalling and its application in reproductive medicine.

The discovery of the essential requirement for kisspeptin and subsequently neurokinin B signalling for human reproductive function has sparked renewed interest in the neuroendocrinology of reproduction. A key discovery has been a population of cells co-expressing both these neuropeptides and dynorphin in the hypothalamus, directly regulating gonadotropin hormone releasing hormone (GnRH) secretion and thus pituitary secretion of gonadotropins. These neurons also project to the vasomotor centre, and their overactivity in estrogen deficiency results in the common and debilitating hot flushes of the menopause. Several antagonists to the neurokinin 3 receptor, for which neurokinin B is the endogenous ligand, have been developed, and are entering clinical studies in human reproductive function and clinical trials. Even single doses can elicit marked declines in testosterone levels in men, and their use has elicited evidence of the regulation of ovarian follicle growth in women. The most advanced indication is the treatment of menopausal vasomotor symptoms, where these drugs show remarkable results in both the degree and speed of symptom control. A range of other reproductive indications are starting to be explored, notably in polycystic ovary syndrome, the most common endocrinopathy in women.

Neurokinin B-Expressing Neurons of the Central Extended Amygdala Mediate Inhibitory Synaptic Input onto Melanin-Concentrating Hormone Neuron Subpopulations.

The lateral hypothalamic area (LHA) is a highly conserved brain region critical for maintaining physiological homeostasis and goal-directed behavior. LHA neurons that express melanin-concentrating hormone (MCH) are key regulators of arousal, energy balance, and motivated behavior. However, cellular and functional diversity among LHAMCH neurons is not well understood. Previous anatomic and molecular data suggest that LHAMCH neurons may be parsed into at least two distinct subpopulations, one of which is enriched in neurokinin-3 receptor (NK3R), the receptor for neurokinin B (NKB), encoded by the Tac2 gene. This tachykininergic ligand-receptor system has been implicated in reproduction, fear memory, and stress in other brain regions, but NKB interactions with LHAMCH neurons are poorly understood. We first identified how LHAMCH subpopulations may be distinguished anatomically and electrophysiologically. To dissect functional connectivity between NKB-expressing neurons and LHAMCH neurons, we used Cre-dependent retrograde and anterograde viral tracing in male Tac2-Cre mice and identified Tac2/EYFP+ neurons in the bed nucleus of the stria terminalis and central nucleus of the amygdala, the central extended amygdala, as major sources of NKB input onto LHAMCH neurons. In addition to innervating the LHA, these limbic forebrain NKB neurons also project to midbrain and brainstem targets. Finally, using a dual-virus approach, we found that optogenetic activation of these inputs in slices evokes GABA release onto a subset of LHAMCH neurons but lacked specificity for the NK3R+ subpopulation. Overall, these data define parallel tachykininergic/GABAergic limbic forebrain projections that are positioned to modulate multiple nodes of homeostatic and behavioral control.SIGNIFICANCE STATEMENT The LHA orchestrates fundamental behavioral states in the mammalian hypothalamus, including arousal, energy balance, memory, stress, and motivated behavior. The neuropeptide MCH defines one prominent population of LHA neurons, with multiple roles in the regulation of homeostatic behavior. Outstanding questions remain concerning the upstream inputs that control MCH neurons. We sought to define neurochemically distinct pathways in the mouse brain that may communicate with specific MCH neuron subpopulations using viral-based retrograde and anterograde neural pathway tracing and optogenetics in brain slices. Here, we identify a specific neuropeptide-defined forebrain circuit that makes functional synaptic connections with MCH neuron subpopulations. This work lays the foundation for further manipulating molecularly distinct neural circuits that modulate innate behavioral states.