Melanocortins in the treatment of male and female sexual dysfunction.

Melanocortinergic agents are currently being investigated for a possible therapeutic role in male and female sexual dysfunction. These investigations were sparked by findings that systemic administration of a synthetic analog of alpha-MSH, MT-II, causes penile erections in a variety of species, including humans. Several other melanocortinergic agents including HP-228, THIQ, and bremelanotide (PT-141) have since been shown to have erectogenic properties thought to be due to binding to melanocortin receptors in the central nervous system, particularly the hypothalamus. Bremelanotide, a nasally administered synthetic peptide, is the only melanocortinergic agent that has been clinically studied in both males and females. Data from Phase II clinical trials of bremelanotide support the use of melanocortin-based therapy for erectile dysfunction. Studies using animal models have demonstrated that pre-copulatory behaviors in female rats analogous to sexual arousal are evoked, and preliminary clinical data also suggest a role in promoting sexual desire and arousal in women. Based on bremelanotide clinical experience, administration of a melanocortin agonist is well tolerated and not associated the hypotension observed with phosphodiesterase-5 inhibitors currently used to treat erectile dysfunction. This review discusses investigations of melanocortin agonists for the treatment of sexual dysfunction with emphasis on proposed sites and mechanisms of action in the central nervous system that appear to be involved in melanocortinergic modulation of sexual function. Current research validates use of melanocortinergic agents for the treatment of both male and female sexual dysfunction.

An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist.

INTRODUCTION: Melanocortins affect multiple physiological responses, including sexual behaviors. Bremelanotide is a synthetic peptide melanocortin analog of alpha-melanocyte-stimulating hormone that is an agonist at melanocortin receptors MC3R and MC4R. AIM: To evaluate a single intranasal dose of bremelanotide for potential effects on physiological and subjective measurements of sexual arousal and desire in premenopausal women with sexual arousal disorder. MAIN OUTCOME MEASURES: Change in vaginal pulse amplitude during neutral and erotic videos after treatment with bremelanotide or placebo and subjects' perceptions of physiological and sexual response within 24 hours of treatment with bremelanotide or placebo. METHODS: Eighteen premenopausal women with a primary diagnosis of female sexual arousal disorder were randomly assigned to receive a single intranasal dose of 20 mg bremelanotide or matching placebo in a double-blind manner during the first in-clinic treatment session, and the alternate medication during the second in-clinic treatment session. During each session, subjects viewed a 20-minute neutral video followed by a 20-minute sexually explicit video. Vaginal photoplethysmography was used to monitor vaginal vasocongestion and questionnaires were used to evaluate perceptions of sexual response within the following 24-hour period. RESULTS: More women reported moderate or high sexual desire following bremelanotide treatment vs. placebo (P = 0.0114), and a trend toward more positive responses regarding feelings of genital arousal occurred after bremelanotide compared with placebo (P = 0.0833). Among women who attempted sexual intercourse within 24 hours after treatment, significantly more were satisfied with their level of sexual arousal following bremelanotide, compared with placebo (P = 0.0256). Vaginal vasocongestion did not change significantly while viewing erotic videos following bremelanotide administration compared with placebo. CONCLUSION: This preliminary evaluation suggests the potential for bremelanotide to positively affect desire and arousal in women with female sexual arousal disorder and indicates that bremelanotide is a promising candidate for further evaluation in an at-home study.

Evaluation of human anti-mouse antibody response in normal volunteers following repeated injections of fanolesomab (NeutroSpec), a murine anti-CD15 IgM monoclonal antibody for imaging infection.

BACKGROUND: Fanolesomab (NeutroSpec) is a murine monoclonal Tc labelled anti-CD15 IgM antibody that localizes collections of human polymorphonuclear neutrophils (PMNs) at sites of infection. OBJECTIVES: The objectives of this study were to evaluate the safety of repeated injections of fanolesomab and the extent of induction of human anti-mouse antibody (HAMA) response. METHODS: Thirty healthy adults (15 men and 15 women) were enrolled in the study. Subjects were injected on two separate occasions, separated by 21 days, with 125 microg of fanolesomab that had been labelled with decayed Tc. HAMA assays were performed on blood samples drawn prior to each injection, and at 7 and 28 days following the second injection. Safety was determined by monitoring for adverse events, and for changes in vital signs, physical examination and clinical laboratory measurements. RESULTS: Five subjects exhibited induction of HAMA (16.7%; 95% CI, 6.3-34.2%). Two were considered marginal responses (increase from 5 to 31, and 5 to 20 and 24 ng x ml), and three were considered moderate (7 to 228, 7 to 140 and 270, and 7 to 35 and 450 ng x ml). There were no strong responses (greater than 1000 ng x ml). Seven subjects experienced adverse events, most of which were coincidental to administration of fanolesomab. There were no serious or severe adverse events. CONCLUSIONS: Repeated fanolesomab injections at clinically useful doses does not appear to induce a strong HAMA response nor does it present a risk for serious adverse events.