A randomized, cross-over controlled study to compare the pharmacokinetic profiles of sublingual administered testosterone solution followed by a sildenafil citrate tablet, versus sublingual testosterone and sildenafil citrate combined in one tablet in healthy premenopausal women

Lybrido (0.5 mg testosterone + 50 mg sildenafil) is under development by
Emotional Brain BV as an on-demand treatment for (the subset) of women with
hypoactive sexual desire disorder (HSDD) characterized by low attention to
sexual cues. Hence, Lybrido is intended for use on a per need (i.e., not
continuous) basis before proposed sexual activity. The cause of low attention
to sexual cues is not well elucidated, but both physiological and psychological
factors are believed to be involved. Thus a combined treatment targeting
central (testosterone) as well as peripheral/local factors (sildenafil) has
been shown to be associated with significant increases in genital arousal, as
well as the frequency and quality of sexual encounters (Van der Made et al.
2009a and Tuiten et al., 2011 in preparation).

In the penis, NO released from nerves and endothelium, induces production of
cyclic guanosine monophosphate (cGMP); cGMP plays a key role in relaxing smooth
muscle, necessary for the induction of an erection. This nucleotide is
hydrolyzed by phosphodiesterases, of which PDE 5 exerts the main activity in
the corpora cavernosa. Therefore, PDE 5 inhibitors will, during sexual
stimulation, enhance the action of NO/cGMP on erectile function (Klotz et al
2001). The genitals of both sexes have common embryological origins. The
clitoris consists of an erectile tissue complex, which embeds the anterior
vaginal wall. Clitoral erection and the anterior wall of the vagina are highly
involved in female sexual arousal and response. This leads to the hypothesis
that PDE-5 inhibitors could be effective in women with FSD, but the studies
investigating this hypothesis have failed to show comparable efficacy as in
men.

Sublingually administered testosterone (0.5mg) has been shown to have a delay
in effect of about 4 hours on subjective and peripheral sexual arousal (Tuiten
et al, 2000 & 2002) in sexually functional women, but not in women with HSDD
(Van der Made 2009a & 2009b). If this central effect of testosterone
administration is coupled with enhancement of the peripheral sexual response
through the use of a PDE-5 inhibitor, an increase in subjective and peripheral
sexual arousal may be observed in women with HSDD. However, the peak effect of
the PDE-5 inhibitor must coincide with the peak effect of the 4 hour delay
effect of testosterone, So for the PDE-5 inhibitor sildenafil (Tmax approx.
30-120 minutes), one would have to administer the sublingual testosterone
first, and after 2-3 hours the sildenafil.

In the first proof of concept study, 0.5 mg testosterone combined with 10 mg
vardenafil (which is comparable to 50 mg sildenafil) was compared to 0.5 mg
testosterone alone, 10 mg vardenafil alone and a placebo employing a double
blind, randomized cross-over design in 13 women with HSDD. Peripheral sexual
arousal was measured with the vaginal pulse amplitude (VPA) in response to
erotic film excerpts. In a subset of women with low preconscious attentional
bias for erotic cues, the VPA increased significantly in the condition of 0.5
mg testosterone combined with 10 mg vardenafil, as compared to the other 3 drug
conditions. Neither 0.5 mg testosterone alone, nor 10 mg vardenafil alone
showed significant increase as compared to placebo (Van der Made et al.,
2009a). This finding was replicated in a second double blind, randomized
placebo-controlled cross-over study with 28 women with HSDD, of which 17 showed
low preconscious attentional bias for erotic cues. In this study, the
participants also reported an increase in subjective sexual arousal following
the viewing of erotic film clips in the condition of 0.5 mg testosterone
combined with 10 mg vardenafil, as compared to these substances separately and
placebo (Van der Made et al., 2009b). The combination of 0.5 mg testosterone
with 50 mg sildenafil was investigated in a double blind, randomized
placebo-controlled cross-over study where 57 women with HSDD could use the
study medication on demand at home during a period of 4 weeks (4 weeks for
Lybrido and 4 weeks for placebo). After each sexual encounter the participants
filled in a short sexual event questionnaire in which various aspects of sexual
functioning were inventoried. The subjective and physiological sexual response
in response to erotic film clips was also measured at the participants* homes
using an ambulatory laboratory (see Bloemers et al., 2010). As expected,
Lybrido increased subjective and physiological sexual responding at home in the
subset of women with low preconscious attentional bias for erotic cues (n=30).
More importantly, these women reported more and better sexual activity (i.e.
more genital arousal and sexual desire) during the 4-week period of on-demand
Lybrido use, as compared to the 4-week placebo period (manuscript in
preparation).

In the above reviewed clinical studies, 0.5 mg testosterone was administered
sublingually as a solution, followed 2.5 hours later (thus creating overlapping
peaks in effect of testosterone and sildenafil) by a 50 mg sildenafil citrate
tablet (or 10 mg vardenafil). Because compliance to this method of
administration requires accurate and thorough instructions, Emotional Brain
has recently developed a combination tablet that will deliver testosterone (0.5
mg) sublingually and, 2.5 hours later, 50 mg sildenafil citrate This will allow
women with HSDD to take just one single preparation 3-6 hours before
anticipated sexual activity.
This new developed drug product is a mint flavored white tablet of 9 mm in
diameter intended for sublingual administration followed by swallowing; after
90 seconds, when the testosterone and mint flavor coating is dissolved. The
quickly dissolving outer coating will deliver testosterone (0.5 mg)
sublingually, and the time-delayed release core will deliver sildenafil citrate
(50 mg) 2.5 hours later. The outer coating comprises testosterone and a mint
flavor, so when the mint flavor is gone (estimated to be around 30 sec), the
testosterone is fully dissolved and maximally available for absorption via the
mucosal membranes.

The present study is part of the ongoing drug development program for Lybrido.
This research proposal describes a pharmacokinetic study of which the main goal
is to compare the pharmacokinetics of testosterone and sildenafil citrate
following administration of a sublingual solution of testosterone with an
encapsulated tablet versus the newly developed combination product.
The purpose of this study is not to determine bioequivalence, but to explore
the pharmacokinetic profiles of both administration methods. Additionally, this
study explores the speed in which the testosterone dissolves in the mouth by
measuring the time the mint flavor is gone.

Primary objective:

To compare the pharmacokinetics of testosterone and sildenafil citrate
following administration of a sublingual solution of testosterone with an
encapsulated tablet versus a combination product.


Secondary objective:

To investigate the time frame in which the mint flavored testosterone coating
is dissolved.

This is a single-center, randomized, cross-over controlled study with two
pharmaceutical formulations containing testosterone and sildenafil citrate.
A total of 12 subjects receive each investigational drug product once in random
order, so that 6 subjects will start with the first formulation and 6 subjects
with the second formulation.
Wash-out between treatments will be at least 7 days. Baseline pharmacokinetic
assessments will be performed each experimental visit before each dosing.
Pharmacokinetic assessments will be performed at pre-determined time points.
Subjects visit the site a total of 4 times: 1 day screening (V0), 2 admission
period and 1 follow up visit. During all visits the subjects* health will be
monitored.

Two interventions will be performed on all participants:
- Administration of sublingual testosterone (0.5 mg) and an oral tablet
containing sildenafil (50 mg).
- Administration of a single fixed-combination oral tablet containing 0.5 mg
testosterone and 50 mg sildenafil

Following drug administration, blood samles will be taken at several times (29
in total) during the day in order to determine the pharmacokinetic profiles of
the two formulations.

General

The subjects will receive reimbursement of expenses for participation. A
standard reimbursement of 828 Euros is given for study completion. Travel
expenses are also reimbursed (fixed fee, 38 Euros).


Blood sampling
A total amount of 453.2 ml will be drawn in each included subject during the
course of the experiment.


Medication
The main adverse reactions to exogenous androgens given chronically in
physiological to slightly supraphysiological concentrations are androgenic side
effects, primarily hirsutism and acne. We consider it to be highly unlikely
that testosterone administration in the doses and frequency to be used in this
study will give rise to any serious health risks. In our previous studies, no
serious health risks/adverse reactions were observed. Within 15 minutes of
testosterone (0.5 mg, sublingually) intake plasma testosterone concentration
increased 10-fold, and returned to baseline levels within 150 minutes.(Tuiten
et al., 2000, van Rooij et al., in preparation). Testosterone is administered
over two experimental visits with a 7 day wash-out between the experimental
visits. The dosing regime regarding testosterone is therefore considered to be
safe.
The most commonly reported adverse reactions in sildenafil treated patients
(based on almost 9000 patients) were headache, flushing, dyspepsia, visual
disorders, nasal congestion, dizziness and visual colour distortion (website
medicines.org). Sildenafil is rapidly absorbed. Maximum observed plasma
concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral
dosing in the fasted state. The total body clearance of sildenafil is 41 l/h
with a resultant terminal phase half life of 3-5 h.
There are no reports of serious health risks of studies which investigated the
combination of testosterone (dosed as gels or via patches) and sildenafil.
Furthermore, in our previous studies no serious adverse events were attributed
to the use of the combination of testosterone and sildenafil. Most common
adverse events were minor headaches and flushing.
Data on the effect of sildenafil and testosterone on oral contraceptives is
lacking. For this reason, participants on oral contraceptives will be
instructed to use a second anti-conception method (double barrier). All
participants will be instructed not to become pregnant during the study.

Clinically relevant abnormalities in ECG and chemistry may be noticed, in which
case a medical specialist may be asked for advice, upon decision of the
research team. If the specialist confirms that medical treatment is necessary,
the participant*s GP physician will be informed. This procedure is mandatory
and explained to the subject in the Informed Consent form.