Bremelanotide: First Approval

Secondary Structure Stabilization of Macrocyclic Antimicrobial Peptides via Cross-Link Swapping

Lactam cross-links have been employed to stabilize the helical secondary structure and enhance the activity and physiological stability of antimicrobial peptides; however, stabilization of β-sheets via lactamization has not been observed. In the present study, lactams between the side chains of C- and N-terminal residues have been used to stabilize the β-sheet conformation in a short ten-residue analogue of chicken angiogenin-4. Designed using a combination of molecular dynamics simulations and Markov state models, the lactam cross-linked peptides are shown to adopt stabilized β-sheet conformations consistent with simulated structures. Replacement of the peptide side-chain Cys-Cys disulfide by a lactam cross-link enhanced the broad-spectrum antibacterial activity compared to the parent peptide and exhibited greater propensity to induce proinflammatory activity in macrophages. The combination of molecular simulations and conformational and biological analyses of the synthetic peptides provides a useful paradigm for the rational design of therapeutically active peptides with constrained β-sheet structures.

Short-Term Dorsal Genital Nerve Stimulation Increases Subjective Arousal in Women With and Without Spinal Cord Injury: A Preliminary Investigation

OBJECTIVES

Female sexual dysfunction (FSD) affects an estimated 40% of women. Unfortunately, FSD is understudied, leading to limited treatment options for FSD. Neuromodulation has shown some success in alleviating FSD symptoms. We developed a pilot study to investigate the short-term effect of electrical stimulation of the dorsal genital nerve and tibial nerve on sexual arousal in healthy women, women with FSD, and women with spinal cord injury (SCI) and FSD.

MATERIALS AND METHODS

This study comprises a randomized crossover design in three groups: women with SCI, women with non-neurogenic FSD, and women without FSD or SCI. The primary outcome measure was change in vaginal pulse amplitude (VPA) from baseline. Secondary outcome measures were changes in subjective arousal, heart rate, and mean arterial pressure from baseline. Participants attended one or two study sessions where they received either transcutaneous dorsal genital nerve stimulation (DGNS) or tibial nerve stimulation (TNS). At each session, a vaginal photoplethysmography sensor was used to measure VPA. Participants also rated their level of subjective arousal and were asked to report any pelvic sensations.

RESULTS

We found that subjective arousal increased significantly from before to after stimulation in DGNS study sessions across all women. TNS had no effect on subjective arousal. There were significant differences in VPA between baseline and stimulation, baseline and recovery, and stimulation and recovery periods among participants, but there were no trends across groups or stimulation type. Two participants with complete SCIs experienced genital sensations.

CONCLUSIONS

To our knowledge, this is the first study to measure sexual arousal in response to short-term neuromodulation in women. This study indicates that short-term DGNS but not TNS can increase subjective arousal, but the effect of stimulation on genital arousal is inconclusive. This study provides further support for DGNS as a treatment for FSD.

Synthesis of Asp-based lactam cyclic peptides using an amide-bonded diaminodiacid to prevent aspartimide formation

Asp-based lactam cyclic peptides are considered promising drug candidates. However, using Fmoc solid-phase peptide synthesis (Fmoc-SPPS) for these peptides also causes aspartimide formation, resulting in low yields or even failure to obtain the target peptides. Here, we developed a diaminodiacid containing an amide bond as a β-carboxyl-protecting group for Asp to avoid aspartimide formation. The practicality of this diaminodiacid has been illustrated by the synthesis of lactam cyclic peptide cyclo[Lys9,Asp13] KIIIA7-14 and 1Y.

Small Effects, Questionable Outcomes: Bremelanotide for Hypoactive Sexual Desire Disorder

Efficacy outcomes are only informative to the extent that they are validated. We examined the measurement properties of efficacy measures from the phase III ("RECONNECT") bremelanotide trials for hypoactive sexual desire disorder (HSDD) in women. Continuous efficacy outcomes, including a) the Female Sexual Function Index (FSFI) and its Desire domain (FSFI-D) and b) the Female Sexual Distress Scale-Desire/Arousal/Orgasm (FSDS-DAO) and its item assessing distress due to low desire (FSDS-DAO #13) have questionable, at best, validity evidence for women with HSDD. We found no validity evidence for previously published categorical treatment response outcomes from the RECONNECT trials. All efficacy results should be reported, but results on 8 of the 11 clinicaltrials.gov-specified efficacy outcomes were heretofore unpublished (including FSDS-DAO total score, FSFI total score, FSFI arousal domain, and items from the Female Sexual Encounter Profile-Revised). We analyzed these outcomes, upon which effect sizes ranged from nil to small. Several other continuous and categorical outcomes generated modest apparent benefits, though nearly all of these outcomes were likely derived post-hoc. Across RECONNECT trial data from two prior publications and the current study, bremelanotide's benefits are statistically modest and limited to outcomes for which scant evidence of validity among women with HSDD exists.

Melanocortin agonism in a social context selectively activates nucleus accumbens in an oxytocin-dependent manner

Social deficits are debilitating features of many psychiatric disorders, including autism. While time-intensive behavioral therapy is moderately effective, there are no pharmacological interventions for social deficits in autism. Many studies have attempted to treat social deficits using the neuropeptide oxytocin for its powerful neuromodulatory abilities and influence on social behaviors and cognition. However, clinical trials utilizing supplementation paradigms in which exogenous oxytocin is chronically administered independent of context have failed. An alternative treatment paradigm suggests pharmacologically activating the endogenous oxytocin system during behavioral therapy to enhance the efficacy of therapy by facilitating social learning. To this end, melanocortin receptor agonists like Melanotan II (MTII), which induces central oxytocin release and accelerates formation of partner preference, a form of social learning, in prairie voles, are promising pharmacological tools. To model pharmacological activation of the endogenous oxytocin system during behavioral therapy, we administered MTII prior to social interactions between male and female voles. We assessed its effect on oxytocin-dependent activity in brain regions subserving social learning using Fos expression as a proxy for neuronal activation. In non-social contexts, MTII only activated hypothalamic paraventricular nucleus, a primary site of oxytocin synthesis. However, during social interactions, MTII selectively increased oxytocin-dependent activation of nucleus accumbens, a site critical for social learning. These results suggest a mechanism for the MTII-induced acceleration of partner preference formation observed in previous studies. Moreover, they are consistent with the hypothesis that pharmacologically activating the endogenous oxytocin system with a melanocortin agonist during behavioral therapy has potential to facilitate social learning.

Low resting metabolic rate and increased hunger due to β-MSH and β-endorphin deletion in a canine model

Mutations that perturb leptin-melanocortin signaling are known to cause hyperphagia and obesity, but energy expenditure has not been well studied outside rodents. We report on a common canine mutation in pro-opiomelanocortin (POMC), which prevents production of β-melanocyte-stimulating hormone (β-MSH) and β-endorphin but not α-MSH; humans, similar to dogs, produce α-MSH and β-MSH from the POMC propeptide, but rodents produce only α-MSH. We show that energy expenditure is markedly lower in affected dogs, which also have increased motivational salience in response to a food cue, indicating increased wanting or hunger. There was no difference in satiety at a modified ad libitum meal or in their hedonic response to food, nor disruption of adrenocorticotropic hormone (ACTH) or thyroid axes. In vitro, we show that β-MSH signals comparably to α-MSH at melanocortin receptors. These data implicate β-MSH and β-endorphin as important in determining hunger and moderating energy expenditure and suggest that this role is independent of the presence of α-MSH.

Cyclic Peptides for Drug Development

Cyclic peptides are fascinating molecules abundantly found in nature and exploited as molecular format for drug development as well as other applications, ranging from research tools to food additives. Advances in peptide technologies made over many years through improved methods for synthesis and drug development have resulted in a steady stream of new drugs, with an average of around one cyclic peptide drug approved per year. Powerful technologies for screening random peptide libraries, and de novo generating ligands, have enabled the development of cyclic peptide drugs independent of naturally derived molecules and now offer virtually unlimited development opportunities. In this review, we feature therapeutically relevant cyclic peptides derived from nature and discuss the unique properties of cyclic peptides, the enormous technological advances in peptide ligand development in recent years, and current challenges and opportunities for developing cyclic peptides that address unmet medical needs.

Development and Challenges of Cyclic Peptides for Immunomodulation

Cyclic peptides are polypeptide chains formed by cyclic sequences of amide bonds between protein-derived or non-protein-derived amino acids. Compared to linear peptides, cyclic peptides offer several unique advantages, such as increased stability, stronger affinity, improved selectivity, and reduced toxicity. Cyclic peptide has been proved to have a promising application prospect in the medical field. In addition, this paper mainly describes that cyclic peptides play an important role in anti-cancer, anti-inflammatory, anti-virus, treatment of multiple sclerosis and membranous nephropathy through immunomodulation. In order to know more useful information about cyclic peptides in clinical research and drug application, this paper also summarizes cyclic peptides currently in the clinical trial stage and cyclic peptide drugs approved for marketing in the recent five years. Cyclic peptides have many advantages and great potential in treating various diseases, but there are still many challenges to be solved in the development process of cyclic peptides.

Acute dorsal genital nerve stimulation increases subjective arousal in women with and without spinal cord injury: a preliminary investigation

Introduction

Female sexual dysfunction (FSD) impacts an estimated 40% of women. Unfortunately, female sexual function is understudied, leading to limited treatment options for FSD. Neuromodulation has demonstrated some success in improving FSD symptoms. We developed a pilot study to investigate the short-term effect of electrical stimulation of the dorsal genital nerve and tibial nerve on sexual arousal in healthy women, women with FSD, and women with spinal cord injury (SCI) and FSD.

Methods

This study consists of a randomized crossover design in three groups: women with SCI, women with non-neurogenic FSD, and women without FSD or SCI. The primary outcome measure was change in vaginal pulse amplitude (VPA) from baseline. Secondary outcome measures were changes in subjective arousal, heart rate, and mean arterial pressure from baseline. Participants attended one or two study sessions where they received either transcutaneous dorsal genital nerve stimulation (DGNS) or tibial nerve stimulation (TNS). At each session, a vaginal photoplethysmography sensor was used to measure VPA. Participants also rated their level of subjective arousal and were asked to report any pelvic sensations.

Results

We found that subjective arousal increased significantly from before to after stimulation in DGNS study sessions across all women. TNS had no effect on subjective arousal. There were significant differences in VPA between baseline and stimulation, baseline and recovery, and stimulation and recovery periods among participants, but there were no trends across groups or stimulation type. Two participants with complete SCIs experienced genital sensations.

Discussion

This is the first study to measure sexual arousal in response to acute neuromodulation in women. This study demonstrates that acute DGNS, but not TNS, can increase subjective arousal, but the effect of stimulation on genital arousal is inconclusive. This study provides further support for DGNS as a treatment for female sexual dysfunction.

Mesoporous silica nanoparticles: An emerging approach in overcoming the challenges with oral delivery of proteins and peptides

Proteins and peptides (PPs), as therapeutics are widely explored in the past few decades, by virtue of their inherent advantages like high specificity and biocompatibility with minimal side effects. However, owing to their macromolecular size, poor membrane permeability, and high enzymatic susceptibility, the effective delivery of PPs is often challenging. Moreover, their subjection to varying environmental conditions, when administered orally, results in PPs denaturation and structural conformation, thereby lowering their bioavailability. Hence, for effective delivery with enhanced bioavailability, protection of PPs using nanoparticle-based delivery system has gained a growing interest. Mesoporous silica nanoparticles (MSNs), with their tailored morphology and pore size, high surface area, easy surface modification, versatile loading capacity, excellent thermal stability, and good biocompatibility, are eligible candidates for the effective delivery of macromolecules to the target site. This review highlights the different barriers hindering the oral absorption of PPs and the various strategies available to overcome them. In addition, the potential benefits of MSNs, along with their diversifying role in controlling the loading of PPs and their release under the influence of specific stimuli, are also discussed in length. Further, the tuning of MSNs for enhanced gene transfection efficacy is also highlighted. Since extensive research is ongoing in this area, this review is concluded with an emphasis on the potential risks of MSNs that need to be addressed prior to their clinical translation.

A gel-forming α-MSH analog promotes lasting melanogenesis

The α-MSH peptide plays a significant role in the regulation of pigmentation via the melanocortin 1 receptor (MC1R). It increases the DNA repair capacity of melanocytes and reduces the incidence of skin cancers. As such, α-MSH analogs could have the utility for protecting against UV-induced skin DNA damage in susceptible patients. Recently, α-MSH analogs have been approved for the treatment of erythropoietic protoporphyria, hypoactive sexual desire, or pediatric obesity. However, the delivery of these drugs requires inconvenient implants or frequent injections. We recently found that select palmitoylated melanocortin analogs such as afamelanotide and adrenocorticotropin peptides self-assemble to form liquid gels in situ. To explore the utility of these novel analogs, we studied their pharmacological characteristics in vitro and in vivo. Acylated afamelanotide (DDE 313) and ACTH1-24 (DDE314) analogs form liquid gels at 6-20% and have a significantly increased viscosity at >2.5% compared to original analogs. Using the DDE313 analog as a prototype, we showed gel-formation reduces the passage of DDE313 through Centricon filters, and subcutaneous injection of analog gel in rats leads to the sustained presence of the peptide in circulation for >12 days. In addition, DDE313 darkened the skin of frogs for >4 weeks, whereas those injected with an equivalent dose of afamelanotide lost the tanning response within a few days. Because self-assembled gels allow sustained activation of melanocortin receptors, further studies of these analogs may allow the development of effective and convenient tanning therapies to prophylactically protect against UV-induced malignant transformation of skin cells in susceptible patients.

Targeting the central melanocortin system for the treatment of metabolic disorders

A large body of preclinical and clinical data shows that the central melanocortin system is a promising therapeutic target for treating various metabolic disorders such as obesity and cachexia, as well as anorexia nervosa. Setmelanotide, which functions by engaging the central melanocortin circuitry, was approved by the FDA in 2020 for use in certain forms of syndromic obesity. Furthermore, the FDA approvals in 2019 of two peptide drugs targeting melanocortin receptors for the treatment of generalized hypoactive sexual desire disorder (bremelanotide) and erythropoietic protoporphyria-associated phototoxicity (afamelanotide) demonstrate the safety of this class of peptides. These approvals have also renewed excitement in the development of therapeutics targeting the melanocortin system. Here, we review the anatomy and function of the melanocortin system, discuss progress and challenges in developing melanocortin receptor-based therapeutics, and outline potential metabolic and behavioural disorders that could be addressed using pharmacological agents targeting these receptors.

Female sexual dysfunction in undergraduate medical education: a survey of U.S. medical students

Background

Physicians often report low levels of confidence in diagnosing and treating female sexual dysfunction (FSD), which may stem from inadequate education and exposure to the topic.

Aim

The study sought to determine the extent to which FSD is covered in undergraduate medical education and evaluate student comfort with the topic and familiarity with treatments.

Methods

We created a novel, 50-question survey to be administered online to any current U.S. medical student. Obstetrician-gynecologist clerkship directors at 146 U.S. medical schools were contacted and asked to invite any current student at their school to participate. A link to the electronic REDCap (Research Electronic Data Capture) survey was distributed to eligible students via the clerkship directors. The survey collected data regarding (1) coverage of FSD and male sexual dysfunction (MSD) in preclinical and clinical curricula, (2) student self-ratings of comfort in hypothetical scenarios in which a patient exhibits symptoms of FSD or MSD, and (3) student familiarity with treatments for FSD and MSD.

Outcomes

Outcomes included the proportion of students reporting that their school covered FSD/MSD in its preclinical/clinical curriculum, the mean comfort ratings for each of the FSD and MSD scenarios, and the proportion of students indicating knowledge of various FSD and MSD treatments.

Results

A smaller proportion of students (N = 236) reported receiving instruction in FSD (58.5%) compared with MSD (78.4%) in their preclinical curriculum (P < .001). Students' average self-ratings of comfort in the sexual dysfunction scenarios were significantly lower for patients with symptoms of FSD compared with MSD (P < .001). Students had higher average self-ratings of confidence in FSD scenarios if their intended specialty was obstetrician-gynecologist (P = .003), if their school included FSD in its clinical curriculum (P = .01), and if they had ever participated in the care of a patient with FSD (P = .006).

Clinical Implications

There are important gaps in the coverage of FSD in undergraduate medical education that may be mitigated through improvements to curriculum and increased exposure to patients with FSD.

Strengths and Limitations

This is the first study, to our knowledge, to directly survey medical students regarding their educational experience and comfort with FSD. Our study was limited by a small sample size, the use of a novel and nonvalidated questionnaire, and the potential for bias given our sampling method.

Conclusion

Medical schools must work toward improving instruction in FSD for their students to address these disparities and improve students' comfort with the topic.

Targeting Melanocortin Receptors Using SNAr-Type Macrocyclization: A Doubly Orthogonal Route to Cyclic Peptide Conjugates

While a range of strategies exist to accomplish peptide macrocyclization, they are frequently limited by the need for orthogonal protection or provide little opportunity for structural diversification. We have evaluated an efficient macrocyclization method that employs nucleophilic aromatic substitution (S_NAr) to create thioether macrocycles. This versatile macrocyclization, orthogonal to conventional peptide synthesis, can be performed in solution on unprotected peptidomimetics or on resin-bound peptides with side-chain protection in place. We show that the electron-withdrawing groups present in the products can be further utilized in subsequent orthogonal reactions to alter the peptide properties or to add prosthetic groups. The macrocyclization strategy was applied to the design of melanocortin ligands, generating a library of potent melanocortin agonists that exhibit distinct subtype selectivity.

Strategies to improve the physicochemical properties of peptide-based drugs

Peptides are a rapid-growing class of therapeutics with unique and desirable physicochemical properties. Due to disadvantages such as low membrane permeability and susceptibility to proteolytic degradation, peptide-based drugs have limited bioavailability, a short half-life, and rapid in vivo elimination. Various strategies can be applied to improve the physicochemical properties of peptide-based drugs to overcome limitations such as limited tissue residence time, metabolic instability, and low permeability. Applied strategies including backbone modifications, side chain modifications, conjugation with polymers, modification of peptide termini, fusion to albumin, conjugation with the Fc portion of antibodies, cyclization, stapled peptides, pseudopeptides, cell-penetrating peptide conjugates, conjugation with lipids, and encapsulation in nanocarriers are discussed.

Asymmetric Synthesis of US-FDA Approved Drugs over Five Years (2016–2020): A Recapitulation of Chirality

Chirality is a major theme in the design, discovery, and development of new drugs. Historically, pharmaceuticals have been synthesized as racemic mixtures. However, the enantiomeric forms of drug molecules have distinct biological properties. One enantiomer may be responsible for the desired therapeutic effect (eutomer), whereas the other may be inactive, interfere with the therapeutic form, or exhibit toxicity (distomer). Classical chemical synthesis usually leads to a racemic mixture unless stereospecific synthesis is employed. To meet the requirements of single-enantiomeric drugs, asymmetric synthesis has evolved at the forefront of drug discovery. Asymmetric synthesis involves the conversion of an achiral starting material into a chiral product. This review emphasizes the methods used for synthesizing FDA-approved chiral drugs during 2016–2020, with a special focus on asymmetric synthesis by means of chiral induction, resolution, or chiral pool.

An evaluation of bremelanotide injection for the treatment of hypoactive sexual desire disorder

INTRODUCTION

Female sexual response implies a deep intertwining between psychosocial and neurobiological mediators. Regulation of central melanocortin signaling may enhance sexual desire. In premenopausal women with hypoactive sexual desire disorder (HSDD), melanocortin receptor agonist bremelanotide (Vyleesi) has been hypothesized to trigger excitatory brain pathways.

AREAS COVERED

Hereby we summarize bremelanotide's proposed mechanism of action, pharmacokinetics, efficacy and safety data derived from clinical trials. A literature search of peer-reviewed publications on the current evidence on the pharmacotherapy with bremelanotide was performed using the PubMed database.

EXPERT OPINION

Bremelanotide appears to be moderately safe and well-tolerated; the most common adverse reaction is nausea (40%). Although data from clinical trials demonstrated a significant change in validated questionnaires, the overall clinical benefit appears to be modest. However, these results should be interpreted in the light of the dramatic challenges in conducting well-designed clinical trials for female sexual dysfunction, due to the significant placebo effect of pharmacotherapy, and the frequent use of outcome measures that are likely to be highly susceptible to expectation biases, such as long periods of recall of sexual and emotional response.

Pharmacotherapy for female sexual dysfunctions (FSDs): what is on the market and where is this field heading?

INTRODUCTION

Female sexual dysfunctions (FSDs) are common in women of any age and have a huge impact on quality of life and relationships. They have a multifaceted etiology limiting the development of pharmacotherapies with a high rate of effectiveness. Safety issues are also a concern.

AREAS COVERED

The authors report the most recent advances in pharmacotherapy for premenopausal and postmenopausal women with a main focus on hypoactive sexual desire disorders (HSDD) and associated sexual symptoms. Good levels of evidence have emerged for psychoactive agents, such as flibanserin and bremelanotide, as well as hormonal compounds (transdermal testosterone). The authors also report briefly on intravaginal DHEA (prasterone), local estrogen therapy (LET), and ospemifene to manage effectively vulvovaginal atrophy/genitourinary syndrome of menopause (VVA/GSM). In addition, they discuss promising therapeutic options highlighting the main reasons that hamper the availability of new labeled products. Finally, they include the importance of the multimodal approach to address FSDs.

EXPERT OPINION

Approved pharmacotherapies for FSD are limited. Validated multidimensional instruments and adequate objective measures of physical and mental responses to sexual external and internal incentives are mandatory to identify women suitable to chronic or on-demand treatments and to assess their pattern of response in research and practice.

Pharmacologic therapeutic options for sexual dysfunction

PURPOSE OF REVIEW

Sexual problems are reported by up to 45% of individuals assigned female at birth. Although sexual function is a complex biopsychosocial construct, there are a number of pharmacologic treatment options aimed at addressing the changing vaginal hormonal milieu in postmenopausal individuals and moderating the excitatory and inhibitory aspects of the central nervous system in those with hypoactive sexual desire disorder.

RECENT FINDINGS

The last decade has seen an increase in the number and type of pharmacologic treatment options for dysfunction primarily associated with menopause and hypoactive sexual desire disorder. Recent publications and systematic reviews have strengthened the safety data of existing FDA-approved medications as well as off-label therapies.

SUMMARY

Pharmacologic treatment with local estrogen and testosterone replacement in postmenopausal individuals and with centrally-acting therapies such as flibanserin, bremelanotide, and testosterone in premenopausal individuals assigned female at birth are safe and can be used to improve sexual desire and sexual satisfaction.

Sexual Health after a Breast Cancer Diagnosis: Addressing a Forgotten Aspect of Survivorship

Breast cancer is the most common cancer in women. The life expectancy after a breast cancer diagnosis is improving steadily, leaving many more persons with the long-term consequences of treatment. Sexual problems are a common concern for breast cancer survivors yet remain overlooked in both the clinical setting and the research literature. Factors that contribute to sexual health concerns in breast cancer survivors are biopsychosocial, as are the barriers to addressing and treating these health concerns. Sexual health needs and treatment may vary by anatomy and gender. Multidisciplinary management may comprise lifestyle modifications, medications, sexual health aids such as vibrators, counseling, and referrals to pelvic health physical therapy and specialty care. In this article, we review the contributing factors, screening, and management of sexual difficulties in cisgender female breast cancer survivors. More information is needed to better address the sexual health of breast cancer survivors whose sexual/gender identity differs from that of cisgender women.

Melanocortin 4 receptor agonism enhances sexual brain processing in women with hypoactive sexual desire disorder

BACKGROUND

Hypoactive sexual desire disorder (HSDD) is characterized by a persistent deficiency of sexual fantasies and desire for sexual activity, causing marked distress and interpersonal difficulty. It is the most prevalent female sexual health problem globally, affecting approximately 10% of women, but has limited treatment options. Melanocortin 4 receptor (MC4R) agonists have emerged as a promising therapy for women with HSDD, through unknown mechanisms. Studying the pathways involved is crucial for our understanding of normal and abnormal sexual behavior.

METHODS

Using psychometric, functional neuroimaging, and hormonal analyses, we conducted a randomized, double-blinded, placebo-controlled, crossover clinical study to assess the effects of MC4R agonism compared with placebo on sexual brain processing in 31 premenopausal heterosexual women with HSDD.

RESULTS

MC4R agonism significantly increased sexual desire for up to 24 hours after administration compared with placebo. During functional neuroimaging, MC4R agonism enhanced cerebellar and supplementary motor area activity and deactivated the secondary somatosensory cortex, specifically in response to visual erotic stimuli, compared with placebo. In addition, MC4R agonism enhanced functional connectivity between the amygdala and the insula during visual erotic stimuli compared with placebo.

CONCLUSION

These data suggest that MC4R agonism enhanced sexual brain processing by reducing self-consciousness, increasing sexual imagery, and sensitizing women with HSDD to erotic stimuli. These findings provide mechanistic insight into the action of MC4R agonism in sexual behavior and are relevant to the ongoing development of HSDD therapies and MC4R agonist development more widely.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04179734.

FUNDING

This is an investigator-sponsored study funded by AMAG Pharmaceuticals Inc., the Medical Research Council (MRC) (MR/T006242/1), and the National Institute for Health Research (NIHR) (CS-2018-18-ST2-002 and RP-2014-05-001).

Ligands for Melanocortin Receptors: Beyond Melanocyte-Stimulating Hormones and Adrenocorticotropin

The discovery of melanocortins in 1916 has resulted in more than 100 years of research focused on these peptides. Extensive studies have elucidated well-established functions of melanocortins mediated by cell surface receptors, including MSHR (melanocyte-stimulating hormone receptor) and ACTHR (adrenocorticotropin receptor). Subsequently, three additional melanocortin receptors (MCRs) were identified. Among these five MCRs, MC3R and MC4R are expressed primarily in the central nervous system, and are therefore referred to as the neural MCRs. Since the central melanocortin system plays important roles in regulating energy homeostasis, targeting neural MCRs is emerging as a therapeutic approach for treating metabolic conditions such as obesity and cachexia. Early efforts modifying endogenous ligands resulted in the development of many potent and selective ligands. This review focuses on the ligands for neural MCRs, including classical ligands (MSH and agouti-related peptide), nonclassical ligands (lipocalin 2, β-defensin, small molecules, and pharmacoperones), and clinically approved ligands (ACTH, setmelanotide, bremelanotide, and several repurposed drugs).

Late-Stage Functionalization with Cysteine Staples Generates Potent and Selective Melanocortin Receptor-1 Agonists

In this work, cysteine staples were used as a late-stage functionalization strategy to diversify peptides and build conjugates targeting the melanocortin G-protein-coupled receptors [melanocortin receptor-1 (MC1R) and MC3R-MC5R]. Monocyclic and bicyclic agonists based on sunflower trypsin inhibitor-1 were used to generate a selection of stapled peptides that were evaluated for binding (pK_i) and functional activation (pEC₅₀) of the melanocortin receptor subtypes. Stapled peptides generally had improved activity, with aromatic stapled peptides yielding selective MC1R agonists, including a xylene-stapled peptide (2) with an EC₅₀ of 1.9 nM for MC1R and >150-fold selectivity for MC3R and MC4R. Selected stapled peptides were further functionalized with linkers and payloads, generating a series of conjugated peptides with potent MC1R activity, including one pyridazine-functionalized peptide (21) with picomolar activity at MC1R (K_i 58 pM; EC₅₀ < 9 pM). This work demonstrates that staples can be used as modular synthetic tools to tune potency and selectivity in peptide-based drug design.

Efficient aqueous remote loading of peptides in poly(lactic-co-glycolic acid)

Poly(lactic-co-glycolic acid) (PLGA) long-acting release depots are effective for extending the duration of action of peptide drugs. We describe efficient organic-solvent-free remote encapsulation based on the capacity of common uncapped PLGA to bind and absorb into the polymer phase net positively charged peptides from aqueous solution after short exposure at modest temperature. Leuprolide encapsulated by this approach in low-molecular-weight PLGA 75/25 microspheres slowly and continuously released peptide for over 56 days in vitro and suppressed testosterone production in rats in an equivalent manner as the 1-month Lupron Depot®. The technique is generalizable to encapsulate a number of net cationic peptides of various size, including octreotide, with competitive loading and encapsulation efficiencies to traditional methods. In certain cases, in vitro and in vivo performance of remote-loaded PLGA microspheres exceeded that relative to marketed products. Remote absorption encapsulation further removes the need for a critical organic solvent removal step after encapsulation, allowing for simple and cost-effective sterilization of the drug-free microspheres before encapsulation of the peptide.

Encapsulation of bioactive peptides in slow-release particles is complex and relies on organic solvents. Here, the authors absorb peptides in a polymer phase from water, creating a simple low-cost encapsulation process in a class of polymer depot.

Female sexual dysfunctions: an overview on the available therapeutic interventions

INTRODUCTION

There are different types of female sexual dysfunctions (FSDs), and FSD in general has a high prevalence worldwide. Studies of FSD should consider it as a multifactorial disorder that has biological, psychological, environmental, and relational aspects. In this review we discuss the available therapeutic interventions for FSD.

EVIDENCE ACQUISITION

For the current narrative review the PubMed database was searched to identify all publications up to 30 March 2021 that were systematic reviews and meta-analyses which examined therapeutic interventions for FSDs based on the diagnostic classifications of ICD-10 and ICD-11.

EVIDENCE SYNTHESIS

Thirty systematic reviews and meta-analyses were included in this review. Hormone therapy (HT) and testosterone are effective to improve sexual desire in menopausal women. In these women HT and ospemiphene may improve pain during intercourse. Flibanserin may improve sexual desire and may reduce desire-related distress in premenopausal women. Bremelanotide is effective to improve desire, arousal, and orgasm scores. Evidence are still limited on the efficacy of psychoactive drugs, phosphodiesterase type 5 (PDE5), oxytocin, herbal drugs, and tibolone to treat FSDs. Psychological interventions such as cognitive-behavior therapy, mindfulness training, sensate focus, bibliotherapy are effective for the management of several different FSDs.

CONCLUSIONS

The management of FSDs may require multidisciplinary and interdisciplinary approaches. Pharmacological and nonpharmacological interventions appears to have potential as a treatment for FSDs, but there are currently no gold standards regarding recommended treatment modalities, and the duration, frequency, and intensity of therapy sessions.

Therapeutic peptides: current applications and future directions

Peptide drug development has made great progress in the last decade thanks to new production, modification, and analytic technologies. Peptides have been produced and modified using both chemical and biological methods, together with novel design and delivery strategies, which have helped to overcome the inherent drawbacks of peptides and have allowed the continued advancement of this field. A wide variety of natural and modified peptides have been obtained and studied, covering multiple therapeutic areas. This review summarizes the efforts and achievements in peptide drug discovery, production, and modification, and their current applications. We also discuss the value and challenges associated with future developments in therapeutic peptides.

Bremelanotide for Treatment of Female Hypoactive Sexual Desire

Hypoactive sexual desire disorder (HSDD) is a persistent deficiency or absence of sexual fantasies and desire resulting in significant distress or interpersonal difficulty. Women with this disorder may display a lack of motivation for sexual activity, reduced responsiveness to erotic cues, a loss of interest during sexual activity, and avoidance of situations that could lead to sexual activity. The pathophysiology of HSDD is thought to be centered around inhibitory and excitatory hormones, neurotransmitters, and specific brain anatomy. Due to the multifactorial nature of HSDD, treatment can be complex and must attempt to target the biological and psychosocial aspects of the disorder. Bremelanotide is a melanocortin receptor agonist and has been recently approved by the FDA to treat HSDD. Bremelanotide is administered intranasally or as a subcutaneous injection. The recommended dosage of bremelanotide is 1.75 mg injected subcutaneously in the abdomen or thigh at least 45 min before sexual activity. Studies showed improvements in desire, arousal, and orgasm scores when 1.75 mg of bremelanotide was administered before sexual activity compared to a placebo. Bremelanotide is a promising way to treat HSDD.

Guideline No. 422d: Menopause and Sexuality

OBJECTIVE

Provide strategies for improving the care of perimenopausal and postmenopausal women based on the most recent published evidence.

TARGET POPULATION

Perimenopausal and postmenopausal women.

BENEFITS, HARMS, AND COSTS

Target population will benefit from the most recent published scientific evidence provided via the information from their health care provider. No harms or costs are involved with this information since women will have the opportunity to choose among the different therapeutic options for the management of the symptoms and morbidities associated with menopause, including the option to choose no treatment.

EVIDENCE

Databases consulted were PubMed, MEDLINE, and the Cochrane Library for the years 2002-2020, and MeSH search terms were specific for each topic developed through the 7 chapters.

VALIDATION METHODS

The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and weak recommendations). INTENDED AUDIENCE: physicians, including gynaecologists, obstetricians, family physicians, internists, emergency medicine specialists; nurses, including registered nurses and nurse practitioners; pharmacists; medical trainees, including medical students, residents, fellows; and other providers of health care for the target population.

SUMMARY STATEMENTS

RECOMMENDATIONS.

Sexual Health

Women's sexual health is a frequently ignored area of geriatric medicine. There are clearly defined criteria for sexual dysfunction that are organized by phase of sexual function, including desire, arousal, orgasm, and pain. The menopause transition and comorbid medical conditions (as well as their treatments) can contribute to alterations in sexual function. The partner must be included and involved in the evaluation and management to achieve a better intimate relationship in an established couple. A variety of effective and evidence-based treatments are available to women for sexual concerns in the geriatric population.

Structural insights into ligand recognition and activation of the melanocortin-4 receptor

Melanocortin-4 receptor (MC4R) plays a central role in the regulation of energy homeostasis. Its high sequence similarity to other MC receptor family members, low agonist selectivity and the lack of structural information concerning MC4R-specific activation have hampered the development of MC4R-seletive therapeutics to treat obesity. Here, we report four high-resolution structures of full-length MC4R in complex with the heterotrimeric G_s protein stimulated by the endogenous peptide ligand α-MSH, FDA-approved drugs afamelanotide (Scenesse™) and bremelanotide (Vyleesi™), and a selective small-molecule ligand THIQ, respectively. Together with pharmacological studies, our results reveal the conserved binding mode of peptidic agonists, the distinctive molecular details of small-molecule agonist recognition underlying receptor subtype selectivity, and a distinct activation mechanism for MC4R, thereby offering new insights into G protein coupling. Our work may facilitate the discovery of selective therapeutic agents targeting MC4R.

The melanocortin-3 receptor is a pharmacological target for the regulation of anorexia

Ablation of hypothalamic AgRP (Agouti-related protein) neurons is known to lead to fatal anorexia, whereas their activation stimulates voracious feeding and suppresses other motivational states including fear and anxiety. Despite the critical role of AgRP neurons in bidirectionally controlling feeding, there are currently no therapeutics available specifically targeting this circuitry. The melanocortin-3 receptor (MC3R) is expressed in multiple brain regions and exhibits sexual dimorphism of expression in some of those regions in both mice and humans. MC3R deletion produced multiple forms of sexually dimorphic anorexia that resembled aspects of human anorexia nervosa. However, there was no sexual dimorphism in the expression of MC3R in AgRP neurons, 97% of which expressed MC3R. Chemogenetic manipulation of arcuate MC3R neurons and pharmacologic manipulation of MC3R each exerted potent bidirectional regulation over feeding behavior in male and female mice, whereas global ablation of MC3R-expressing cells produced fatal anorexia. Pharmacological effects of MC3R compounds on feeding were dependent on intact AgRP circuitry in the mice. Thus, the dominant effect of MC3R appears to be the regulation of the AgRP circuitry in both male and female mice, with sexually dimorphic sites playing specialized and subordinate roles in feeding behavior. Therefore, MC3R is a potential therapeutic target for disorders characterized by anorexia, as well as a potential target for weight loss therapeutics.

Application of tert-Butyl Disulfide-Protected Amino Acids for the Fmoc Solid-Phase Synthesis of Lactam Cyclic Peptides under Mild Metal-Free Conditions

Lactam cyclic peptides are a class of interesting and pharmaceutically active molecules, but their previous syntheses have required the use of heavy metals and/or forcing conditions. Here, we describe the efficient application of the previously reported tert-butyl disulfide-protected amino acids and their use in the efficient, solid-phase synthesis of a series of lactam cyclic peptides under mild, metal-free conditions.

A Melanocortin-4 Receptor Agonist Induces Skin and Hair Pigmentation in Patients with Monogenic Mutations in the Leptin-Melanocortin Pathway

BACKGROUND AND OBJECTIVES

Gene mutations within the leptin-melanocortin signaling pathway lead to severe early-onset obesity. Recently, a phase 2 trial evaluated new pharmacological treatment options with the MC4R agonist setmelanotide in patients with mutations in the genes encoding proopiomelanocortin (POMC) and leptin receptor (LEPR). During treatment with setmelanotide, changes in skin pigmentation were observed, probably due to off-target effects on the closely related melanocortin 1 receptor (MC1R). Here, we describe in detail the findings of dermatological examinations and measurements of skin pigmentation during this treatment over time and discuss the impact of these changes on patient safety.

METHODS

In an investigator-initiated, phase 2, open-label pilot study, 2 patients with loss-of-function POMC gene mutations and 3 patients with loss-of-function variants in LEPR were treated with the MC4R agonist setmelanotide. Dermatological examination, dermoscopy, whole body photographic documentation, and spectrophotometric measurements were performed at screening visit and approximately every 3 months during the course of the study.

RESULTS

We report the results of a maximum treatment duration of 46 months. Skin pigmentation increased in all treated patients, as confirmed by spectrophotometry. During continuous treatment, the current results indicate that elevated tanning intensity levels may stabilize over time. Lips and nevi also darkened. In red-haired study participants, hair color changed to brown after initiation of setmelanotide treatment.

DISCUSSION

Setmelanotide treatment leads to skin tanning and occasionally hair color darkening in both POMC- and LEPR-deficient patients. No malignant skin changes were observed in the patients of this study. However, the results highlight the importance of regular skin examinations before and during MC4R agonist treatment.

Development of hMC1R Selective Small Agonists for Sunless Tanning and Prevention of Genotoxicity of UV in Melanocytes

Activation of the human melanocortin 1 receptor (hMC1R) expressed on melanocytes by α-melanocortin plays a central role in regulating human pigmentation and reducing the genotoxicity of UV by activating DNA repair and antioxidant defenses. For the development of a hMC1R-targeted photoprotection strategy, we designed tetra- and tripeptide agonists with modifications that provide the necessary lipophilicity and hMC1R selectivity to be effective drugs. These peptides proved to be superior to most of the existing analogs of the physiological tridecapeptide α-melanocortin because of their small size and high hMC1R selectivity. Testing on primary cultures of human melanocytes showed that these peptides are highly potent with prolonged stimulation of melanogenesis, enhanced repair of UV-induced DNA photoproducts, and reduced apoptosis. One of the tripeptides, designated as LK-514 (5), with a molecular weight of 660 Da, has unprecedented (>100,000) hMC1R selectivity when compared with the other melanocortin receptors hMC3R, hMC4R, and hMC5R, and increases pigmentation (sunless tanning) in a cultured, three-dimensional skin model. These new analogs should be efficacious in preventing skin cancer, including melanoma, and treatment of skin disorders, such as vitiligo and polymorphic light eruptions.

Management of hypoactive sexual desire disorder in transgender women: a guide for clinicians

Hypoactive sexual desire disorder (HSDD) represents a common condition among transgender women. However, to date no specific guidelines for the management of HSDD in transgender persons are available. The aim of the present narrative Review is to evaluate evidence-based treatment for HSDD and to suggest treatment options for HSDD in transgender women. Clinically relevant publications on the management of HSDD (from 1985 to 2020) were searched in PubMed and Medline databases, using the following terms: "sexual desire", "sexual health", "HSDD", "transgender", "gender-affirming treatment", "sexual therapy", "testosterone treatment", "Central nervous system-active medications", and variants. Since sexual desire could be affected by several factors, a comprehensive assessment of HSDD- exploring biological, psychological, and social domains- is recommended, in order to identify possible predisposing, precipitating and maintaining factors. Among treatment options, transgender women may benefit of different sex therapy strategies and/or central nervous system-active medications-such as flibanserin, bremelanotide, bupropion and buspirone-and transdermal testosterone, bearing in mind that this option could be poorly accepted by patients due to the risk of virilizing effects. The lack of data regarding the efficacy of HSDD treatment options in transgender women emphasize the need for literature to focus more on this topic in the future.

Restoration of Cardiac Function After Myocardial Infarction by Long-Term Activation of the CNS Leptin-Melanocortin System

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Leptin protects against progression to heart failure after myocardial infarction.

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This beneficial effect requires activation of the brain melanocortin system.

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Stimulation of brain MC4R recapitulates the cardiac protective effects of leptin.

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Leptin-MC4R activation improves cardiac substrate oxidation and mitochondrial function.

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It also improves Ca²⁺ coupling and contractile function in viable cardiomyocytes after MI.

Heart failure has a high mortality rate, and current therapies offer limited benefits. The authors demonstrate that activation of the central nervous system leptin-melanocortin pathway confers remarkable protection against progressive heart failure following severe myocardial infarction. The beneficial cardiac-protective actions of leptin require activation of brain melanocortin-4 receptors and elicit improvements in cardiac substrate oxidation, cardiomyocyte contractility, Ca²⁺ coupling, and mitochondrial efficiency. These findings highlight a potentially novel therapeutic approach for myocardial infarction and heart failure.

Combining MALDI mass spectrometry imaging and droplet-base surface sampling analysis for tissue distribution, metabolite profiling, and relative quantification of cyclic peptide melanotan II

Peptides have become a fast-growing segment of the pharmaceutical industry over the past few decades. It is essential to develop cutting edge analytical techniques to support the discovery and development of peptide therapeutics, especially to examine their absorption, distribution, metabolism and excretion (ADME) properties. Herein, we utilized two label-free mass spectrometry (MS) based techniques to investigate representative challenges in developing therapeutic peptides, such as tissue distribution, metabolic stability and clearance. A tool proof-of-concept cyclic peptide, melanotan II, was used in this study. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), which is a well-developed label-free imaging technique, was used to map the detailed molecular distribution of melanotan II and its metabolites. Droplet-based liquid microjunction surface sampling liquid chromatography-high resolution mass spectrometry (LMJ-SSP-LC-HRMS) was used in combination with MALDI-MSI to rapidly profile molecular information and provide structural insights on drug and metabolites. Using both techniques in parallel allowed a more comprehensive and complementary data set than using either technique independently. We envision MALDI-MSI and droplet-based LMJ-SSP-LC-HRMS, which can be used in combination or as standalone techniques, to become valuable tools for assessing the in vivo fate of peptide therapeutics in support of drug discovery and development.

Structural Complexity and Plasticity of Signaling Regulation at the Melanocortin-4 Receptor

The melanocortin-4 receptor (MC4R) is a class A G protein-coupled receptor (GPCR), essential for regulation of appetite and metabolism. Pathogenic inactivating MC4R mutations are the most frequent cause of monogenic obesity, a growing medical and socioeconomic problem worldwide. The MC4R mediates either ligand-independent or ligand-dependent signaling. Agonists such as α-melanocyte-stimulating hormone (α-MSH) induce anorexigenic effects, in contrast to the endogenous inverse agonist agouti-related peptide (AgRP), which causes orexigenic effects by suppressing high basal signaling activity. Agonist action triggers the binding of different subtypes of G proteins and arrestins, leading to concomitant induction of diverse intracellular signaling cascades. An increasing number of experimental studies have unraveled molecular properties and mechanisms of MC4R signal transduction related to physiological and pathophysiological aspects. In addition, the MC4R crystal structure was recently determined at 2.75 Å resolution in an inactive state bound with a peptide antagonist. Underpinned by structural homology models of MC4R complexes simulating a presumably active-state conformation compared to the structure of the inactive state, we here briefly summarize the current understanding and key players involved in the MC4R switching process between different activity states. Finally, these perspectives highlight the complexity and plasticity in MC4R signaling regulation and identify gaps in our current knowledge.

Pharmacological treatment strategies for patients with monogenic obesity

The leptin melanocortin signaling pathway is playing a pivotal role for body weight regulation. Genetic defects within this cascade are leading to severe hyperphagia and early onset obesity. In most cases, due to persistent hyperphagia the affected patients are not able to stabilize body weight for a longer period of time with conservative treatment strategies based on lifestyle interventions. Therefore, it is of importance to implement alternative treatment options for these patients. This review provides an overview about the published pharmacological treatment attempts in respect to monogenic forms of obesity and summarizes recent research progress about the role of MC4R signaling and POMC derivatives for body weight regulation.

New Medications for Neuropsychiatric Disorders

This article seeks to summarize the mechanisms of action, clinical trials, and FDA approval status of several psychiatric medications that are either newly available or in the FDA approval process. This article highlights medications that demonstrate novel mechanisms of action, examines nonpsychiatric medications that are being used to augment existing psychiatric treatments, and elucidates treatments for illnesses that have not previously received FDA indications.

Topical Alpha-1 Adrenergic Receptor Agonist Applied to the Nipple/Areola Complex Improves Female Orgasmic Function

Background: The impact of nipple sensation and its relationship to sexual function have often been neglected in medical literature. However, several recent studies report the importance of the nipple/areola complex (NAC) in sexual arousal and overall function. The nipple is composed of smooth muscle that can be erected via adrenergic nerves. In two complementary studies, we demonstrate that stimulation of the alpha-1 adrenergic receptor in the NAC with topical adrenergic agents can initiate erection of the nipple, increase NAC sensitivity, and improve sexual function. Materials and Methods: Thirteen breast surgery patients with nipple sensitivity loss were recruited to an unblinded study of topical phenylephrine hydrochloride. Sensitivity to pressure was measured before and after the application of the intervention to the NAC. In a second pilot study, 35 women completed a double-blinded placebo-controlled trial of a novel formulation, RJ101, containing a norepinephrine releasing agent. The intervention or placebo was applied to the NAC 30 minutes before sexual activity over the 4-week trial period. The arousal, lubrication, and orgasm domains of the female sexual function index (FSFI) were used to measure sexual function. Results: The application of phenylephrine hydrochloride was shown to increase nipple sensitivity to pressure by an average of 20% in our cohort of 13 breast augmentation patients. In addition, it was shown that intermittent application of the alpha-1 agonist for 8 weeks increased basal NAC sensitivity. In the follow-up pilot study, we demonstrate that stimulation of the NAC with RJ101 produced statistically significant increases versus placebo in the lubrication and orgasm domains of the FSFI, p = 0.0226 and p = 0.0269, respectively. Conclusion: For the first time, we demonstrate that the application of a topical alpha-1 adrenergic receptor agonist or a norepinephrine-releasing agent increases the sensitivity of the NAC and subsequently significantly improves sexual function.

Novel Emerging Therapies for Erectile Dysfunction

Currently, several treatments exist for the improvement of erectile dysfunction (ED). These include medical therapies such as phosphodiesterase type 5 inhibitors (PDE5-Is), invasive methods such as intracavernosal injection therapy of vaso-active substances, vacuum erection devices, and penile prosthesis implants. However, the percentage of patients that are unresponsive to available treatments and who drop out from treatments remains high. Current evidence reveals that the pathogenesis of ED is related to multiple factors including underlying comorbidities, previous surgery, and psychological factors. Diverse approaches using novel molecular pathways or new technologies have been tested as potential therapeutic options for difficultto-treat ED populations. Melanocortin receptor agonist, a centrally acting agent, showed promising results by initiating erection without sexual stimulation in non-responders to PDE5-Is. Recent clinical and pre-clinical studies using human tissues suggested that new peripherally acting agents including the Max-K channel activator, guanylate cyclase activator, and nitric oxide donor could be potential therapies either as a monotherapy or in combination with PDE5-Is in ED patients. According to several clinical trials, regeneration therapy using stem cells showed favorable data in men with diabetic or post-prostatectomy ED. Low-intensity shock wave therapy also demonstrated promising results in patients with vasculogenic ED. There are growing evidences which suggest the efficacy of these emerging therapies, though most of the therapies still need to be validated by well-designed clinical trials. It is expected that, should their long-term safety and efficacy be proven, the emerging treatments can meet the needs of patients hitherto unresponsive to or unsatisfied by current therapies for ED.

2019 FDA TIDES (Peptides and Oligonucleotides) Harvest

2019 has been an excellent year in terms of peptides and oligonucleotides (TIDES) approved by the FDA. Despite the drop in the number of total drugs approved by the FDA in 2019 in comparison with 2018 (48 vs. 59), the total number of TIDES authorized increased (seven vs. three). Year after year, TIDES are increasingly present in therapy, as imaging agents, theragnostic and constituent moieties of other complex drugs, such as antibody drug conjugates. This means a consolidation of these kinds of drugs in the pharmaceutical arena, paving the way in the coming years for the approval of others for diverse medical indications. Here the TIDES approved in 2019 are analyzed in terms of chemical structure, medical target, mode of action, and adverse effects.

Bremelanotide: New Drug Approved for Treating Hypoactive Sexual Desire Disorder

Objective: To review data regarding bremelanotide, a recently approved therapy for hypoactive sexual desire disorder (HSDD). Data Sources: Literature search of Medline, SCOPUS, and EMBASE was performed using the search terms bremelanotide, bremelanotide injection, Vyleesi, and melanocortin 4 receptor agonist between January 1, 1996, and December 15, 2019. Reference lists from included articles were also reviewed for pertinent citations. Study Selection/Data Extraction: We included phase 2 and 3 trials of bremelanotide. There were 2 reports of phase 3 trials and 2 reports of phase 2 trials. Additional information from supplementary analyses was also referenced. Data Synthesis: Bremelanotide demonstrates significant improvement in desire and a significant decrease in distress related to lack of desire. The most common adverse effects include nausea (39.9%), facial flushing (20.4%), and headache (11%). Relevance to Patient Care and Clinical Practice: Bremelanotide is the second Food and Drug Administration–approved medication for the treatment of HSDD. Bremelanotide’s place in therapy is unknown, as the HSDD guidelines were last updated in 2017. Although the trials met statistical significance for change in sexual desire elements and distress related to sexual desire, the clinical benefit may only be modest. Conclusion: Bremelanotide is a subcutaneous injection that can be administered as needed approximately 45 minutes prior to sexual activity. Bremelanotide is safe and has limited drug-drug interactions, including no clinically significant interactions with ethanol. Prescribing guidelines recommend no more than 1 dose in 24 hours and no more than 8 doses per month. Individuals should discontinue use after 8 weeks without benefit.