Oxytocin antagonists: the next frontier in PE treatment

Oxytocin and vasopressin signaling in health and disease

Neurohypophysial peptides are ancient and evolutionarily highly conserved neuropeptides that regulate many crucial physiological functions in vertebrates and invertebrates. The human neurohypophysial oxytocin/vasopressin (OT/VP) signaling system with its four receptors has become an attractive drug target for a variety of diseases, including cancer, pain, cardiovascular indications, and neurological disorders. Despite its promise, drug development faces hurdles, including signaling complexity, selectivity and off-target concerns, translational interspecies differences, and inefficient drug delivery. In this review we dive into the complexity of the OT/VP signaling system in health and disease, provide an overview of relevant pharmacological probes, and discuss the latest trends in therapeutic lead discovery and drug development.

Vital function of DRD4 in dapoxetine medicated premature ejaculation treatment

BACKGROUND

Recently, dapoxetine has been widely accepted to treat premature ejaculation by fast-inhibiting 5-hydroxytryptamine reuptake. However, dapoxetine is not suitable for all premature ejaculation patients in clinical treatment. We need to investigate and reveal the mechanism deeply to solve this problem.

OBJECTIVES

To investigate and reveal the function of dopamine D4 receptor in dapoxetine medicated premature ejaculation treatment.

MATERIALS AND METHODS

A rat model was used to screen rapid ejaculators. The molecular mechanisms of histone serotonylation-mediated regulation of dopamine D4 receptor were demonstrated by chromatin immunoprecipitation, DNA pull-down, mass spectrometry analysis, and coimmunoprecipitation experiments. The biological function of dopamine D4 receptor was investigated through in vivo experiments by intrathecal injection of shDRD4 to knockdown dopamine D4 receptor.

RESULTS

In this study, we found that dapoxetine increased expression of 5-hydroxytryptamine and dopamine D4 receptor. We demonstrated that dapoxetine increased levels of 5-hydroxytryptamine, which promoted histone serotonylation (H3K4me3Q5ser) and transcription factor myeloid zinc-finger 1 complex binding on the dopamine D4 receptor promoter, upregulated the expression of dopamine D4 receptor and thus delayed ejaculation.

DISCUSSION

In this study, we demonstrated that dapoxetine increased the levels of 5-hydroxytryptamine, which promoted histone serotonylation and myeloid zinc-finger 1 complex binding to the dopamine D4 receptor promoter and upregulated the expression of dopamine D4 receptor, thus delaying ejaculation.

CONCLUSION

It is a novel mechanism that dapoxetine take effect of premature ejaculation treatment through upregulating the dopamine D4 receptor, which indicated that upregulated dopamine D4 receptor would enhance the dapoxetine effect in premature ejaculation treatment. This may lead to the development of novel therapeutic interventions for premature ejaculation.

Current and emerging treatment options for premature ejaculation

Premature ejaculation (PE) is a prevalent male sexual dysfunction. Current standard treatment regimens include behavioural therapies, topical anaesthetics, dapoxetine and other selective serotonin reuptake inhibitors (SSRIs). Most of the pharmacotherapeutic options target neurotransmitters (such as serotonin and oxytocin) that have a role in the ejaculation mechanism. However, these treatments are mildly effective and only provide a temporary delay in the ejaculation latency time, and PE recurs when the treatment is stopped. Thus, a treatment for PE is urgently needed and research is ongoing to find the ideal PE therapy. The efficacy and safety of topical anaesthetics and SSRIs in delaying ejaculation have been confirmed in many well-designed controlled trials. Both preclinical and clinical studies on new-generation SSRIs are ongoing. Moreover, promising results came from clinical trials in which the efficacy of on-demand PE therapies targeting neurotransmitters other than serotonin, such as α1-adrenoceptor antagonists and oxytocin antagonists, was assessed. Surgical intervention and neuromodulation have been proposed as potential treatment options for PE; however, current PE guidelines do not recommend these treatments owing to safety concerns.

Temperament-Character Traits and Attitudes Toward Premature Ejaculation in 4 Types of Premature Ejaculation

BACKGROUND

Although temperament-character traits and attitudes toward premature ejaculation (PE) are known to be associated with PE, it is of great significance to study them in PE. Moreover, few studies have evaluated these traits and attitudes in the new classification of 4 subtypes of PE.

AIM

We investigated the temperament-character traits and attitudes toward PE in 4 types of PE and their associations with PE.

METHODS

Between December 2018 and December 2019, we conducted a survey in our hospital, and enrolled 350 men who complained of PE and 252 men without any complaint of PE. Temperament-character traits and attitudes toward PE were independently assessed by the Temperament and Character Inventory-Revised and several targeted questions, respectively. The Index of Premature Ejaculation (IPE) was used to evaluate ejaculation control, sexual life satisfaction, and distress caused by PE.

OUTCOMES

The outcomes included differences of temperament-character traits and attitudes toward PE among 2 groups and their associations with PE.

RESULTS

Of the 2 groups, men with PE complaints had lower novelty seeking/self-transcendence (NS/ST) scores and higher harm avoidance (HA) scores vs men without any complaints of PE. Among the 4 types of PE, men with variable PE had the highest score of HA and lowest score of NS; the lowest score of ST was recorded in men with lifelong PE. Additionally, the total and subdomain scores of IPE in men with subjective PE were higher than the other subtypes of PE. After adjusting for age, positive correlations were observed in HA score and total and subdomain scores of IPE, whereas the inverse was true corresponding to NS and ST.

CLINICAL IMPLICATIONS

The current study has provided a new perspective for understanding the impact of psychological factors on PE.

STRENGTHS & LIMITATIONS

This is the first study to systematically assess the effects of personality traits and attitudes on PE, especially among the 4 types of PE. The main drawback is that the generalizability of this study may be limited by the fact that it was conducted in a single cultural/societal background.

CONCLUSION

Men who complained of PE tended to react with indifference or rejection to novelty, tended to feel unsatisfied, cannot effectively adapt to changes in the surrounding environment, and tended to avoid situations involving risk. These characteristics could lead to their becoming disheartened when faced with PE. Furthermore, the attitude of men with PE reflects the needs of the patient during treatment from one aspect. Gao P, Gao J Wang Y, et al. Temperament-Character Traits and Attitudes Toward Premature Ejaculation in 4 Types of Premature Ejaculation. J Sex Med 2021;18:72-82.

Opportunities for Tapping into Three-Dimensional Chemical Space through a Quaternary Carbon

A quaternary carbon bears four other carbon substituents or combination of four non-hydrogen substituents at four vertices of a tetrahedron. The spirocyclic quaternary carbon positioned at the center of a bioactive molecule offers conformational rigidity, which in turn reduces the penalty for conformational entropy. The quaternary carbon is a predominant feature of natural product structures and has been associated with more effective and selective binding to target proteins compared to planar compounds with a high sp² count. The presence of a quaternary carbon stereocenter allows the exploration of novel chemical space to obtain new molecules with enhanced three-dimensionality. These characteristics, coupled to an increasing awareness to develop sp³-rich molecules, boosted utility of quaternary carbon stereocenters in bioactive compounds. It is hoped that this Perspective will inspire the chemist to utilize quaternary carbon stereocenters to enhance potency, selectivity, and other drug-like properties.