Introduction: Prior medication treatment for hypoactive sexual desire disorder (HSDD) in women has left about half the subjects without benefit. Lorexys (LOR), a proprietary combination of the stimulating/excitatory dopamine-norepinephrine reuptake inhibitor bupropion (BUP) and the sedating/inhibitory serotonergic agonist-antagonist trazodone (TRZ), was developed as a multifunctional solution for this problem.

Aim: Test efficacy, safety, and tolerability of LOR in a range of doses in a combined phase IB/IIA study in premenopausal outpatients with HSDD.

Methods: Otherwise healthy premenopausal women from 25-50 years of age with HSDD were tested in an open-label, active-control, one-way crossover study, with three 4-week treatments of extended-release TRZ and/or sustained-release BUP. Evaluations were made before and after each treatment. A washout of at least a week followed each treatment. The order of treatments was a standard dose of BUP; a subtherapeutic dose of BUP and TRZ (LOR-low); and a threshold-therapeutic dose of BUP and TRZ (LOR-mod). A midpoint interim analysis was planned to consider adapting doses for efficacy or safety.

Main outcome measure: The primary efficacy measure was the Female Sexual Function Index, Desire domain; the main secondary efficacy measures included the Female Sexual Distress Scale-Revised 13th item, on bother about low desire, and a Patient's Global Impression of Change. The main outcome comparison was the proportions of responders. Safety measures were elicited adverse events, Epworth Sleepiness Scale, Columbia Suicide Severity Rating Scale 6-item SCREEN version, vital signs, electrocardiograms, and standard laboratory tests.

Results: Interim analysis did not require altering doses. Most evaluable subjects responded to LOR-mod (at the standard thresholds for response based on minimum clinically relevant difference from baseline, 79% on Female Sexual Function Index, Desire domain, 87% on Female Sexual Distress Scale-Revised Item 13, and 79% on Patient's Global Impression of Change; each P < .05 vs BUP). As expected, close to half responded to BUP (38%, 45%, and 52%, respectively). Response to LOR-low was intermediate (not significant vs BUP). Sensitivity analyses to compensate for carryover effects supported the efficacy of LOR-mod. Elicited adverse events showed the expected profile of TRZ, but led to no sedative-type dropouts or worsening on the Epworth Sleepiness Scale.

Clinical implications: The open-label 1-way crossover design of this phase IB/IIA study limits conclusions, but the consistency of responder analyses showing superiority of LOR-mod dose over control, and the lack of central depressant dropouts, favor further development in double-blind placebo-control trials.

Strength & limitations: Strengths include large margins of efficacy over control agent, rapid onset of action, and rigorous safety assessment. Limitations are open-label, cross-over design/lack of placebo control and 1-month duration of exposure.

Conclusion: Moderate-dose LOR was generally well-tolerated and was significantly more effective than BUP (active control). The results seem highly favorable compared to previously tested agents. Pyke RE, Clayton AH. Dose-Finding Study of Lorexys for Hypoactive Sexual Desire Disorder in Premenopausal Women. J Sex Med 2019;16:1885-1894.