A Study to Assess the Safety, Tolerability and Pharmacokinetics of Viaca (Sildenafil + Cabergoline) Compared With Sildenafil and Cabergoline

An Open-Label Single-Ascending Dose Study to Investigate the Safety, Tolerability and Pharmacokinetics of Viaca (Sildenafil + Cabergoline) Compared With Sildenafil and Cabergoline in Healthy Volunteers

This is a Phase 1, open-label, single-ascending-dose study evaluating the safety, tolerability, and pharmacokinetics (PK) of Viaca - a fixed-dose oral combination of sildenafil (a PDE5 inhibitor) and cabergoline (a dopamine D2 agonist) - versus sildenafil monotherapy and cabergoline monotherapy in healthy adult male volunteers. Approximately 30 participants are enrolled across 5 sequential cohorts (6 each). Each participant receives a single oral dose. The combination targets erectile dysfunction through both vascular and neuroendocrine pathways, aiming for efficacy at lower component doses.

Study Overview

• Status: Not yet recruiting
• Conditions: Healthy Volunteer; Erectile Dysfunctions
• Intervention / Treatment: Drug: Viaca; Drug: Sildenafil 50 mg; Drug: Cabergoline 0.5 MG

Detailed Description

Five cohorts of 6 healthy male participants each (n≈30). Viaca dose cohorts: Cohort 1 (25/0.25 mg), Cohort 2 (50/0.5 mg), Cohort 3 (75/0.75 mg). Active-comparator cohorts: Cohort 4 (sildenafil 50 mg) and Cohort 5 (cabergoline 0.5 mg). Cohort 1 runs first; after Safety Review Committee (SRC) review of safety/tolerability/PK through Day 3, Cohorts 2, 4 and 5 may proceed in parallel; Cohort 3 proceeds after SRC review of Cohort 2. Participants fast ≥8 h overnight before dosing and 2 h after. They are confined to a Phase 1 unit and discharged on Day 5 (Cohorts 1-3 and 5) or Day 2 (Cohort 4), with a follow-up visit on Day 8 (±1). Total participation ~33 days including screening. (V2.0 amendment removed the former optional high-dose Viaca cohort.)

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Phase 1

Contacts and Locations

• Study Contact: Name: Clinical Research Coordinator at Nucleus Network Brisbane; Phone Number: 1800 243 733; Email: brisbane@nucleusnetwork.com

Study Locations

• Australia
  • Queensland
    • Herston, Queensland, Australia, 4006
      • Nucleus Network Brisbane

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Male participants, aged 18 to 65 years (inclusive) at the time of informed consent.
• In good general health (Investigator judgement) with no significant medical history and no clinically significant abnormalities on physical examination, vital signs, or 12-lead ECG - including systolic blood pressure 110-140 mmHg (inclusive) at Screening and Day -1 - at Screening and/or before first IP administration.
• BMI ≥ 18.0 and ≤ 32.0 kg/m² and weight ≥ 50 kg.
• Nonsmoker or casual smoker (< 5 cigarettes/week equivalent) with no tobacco use within 2 months prior to Screening (Investigator discretion).
• Clinical laboratory values within normal range (or not clinically significant per Investigator).
• Fertile men agree to acceptable contraception from Screening until 90 days after last IP dose, and no sperm donation from first dose until ≥ 90 days after last dose.
• Able and willing to attend required study visits.
• Able and willing to provide written informed consent before any study procedures.

Exclusion Criteria:

• Physical or psychological condition that would impair protocol compliance or study completion (Investigator judgement).
• History of, or condition that would contraindicate study medication or interfere with study evaluations (Investigator judgement).
• Previous history of any of: myocardial infarction; cerebrovascular accident; arrhythmia; congestive heart failure; unstable angina; recent (<6 months) need for calcium-channel/beta-blocker/nitrate/anti-epileptic therapy; uncontrolled hypertension (SBP >140 or DBP >100 mmHg); hypotension (SBP <90 or DBP <60 mmHg) incl. syncope/orthostatic/vasovagal; pulmonary/pericardial/retroperitoneal fibrotic disorders; sickle-cell disease or trait; cardiac valve disease; severe psychiatric disorders; Raynaud's/vasospastic disorders; bariatric surgery (cholecystectomy acceptable).
• Blood/plasma donation or significant blood loss (450 mL) within 30 days prior to first IP dose.
• Fever (>38°C) or symptomatic viral/bacterial infection within 2 weeks prior to Screening.
• Infections requiring parenteral antibiotics within 1 month prior to Screening.
• Concomitant use of an indwelling urethral catheter.
• Concomitant nitrates/nitric-oxide donors, potent CYP3A4 inhibitors (e.g. ritonavir, indinavir, ketoconazole) or moderate inhibitors (e.g. erythromycin); unwilling to avoid St. John's wort and CYP3A4-active herbals (e.g. grapefruit) within 14 days prior and throughout the study.
• Medications that significantly affect BP: nitrates (any form), alpha-blockers (e.g. doxazosin, terazosin, tamsulosin), guanylate cyclase stimulators (e.g. riociguat).
• Positive HCV antibody, HBsAg, or HIV antibody.
• Live vaccine within 4 weeks prior to first IP dose.
• Poor pill-swallowing ability or poor venous access.
• History of severe allergic/anaphylactic reactions or sensitivity to IP or constituents.
• History of malignancy (except non-melanoma skin cancer excised >5 years prior to Screening).
• Clinically significant abnormal Screening ECG (e.g. QRS ≥ 120 msec and/or QTcF > 450 msec, per Investigator).
• History/evidence of renal disease or eGFR < 60 mL/min/1.73 m² at Screening (2021 CKD-EPI creatinine equation).
• Immunosuppressive drug exposure (incl. experimental therapies) within 4 months or 5 half-lives (whichever longer) prior to Screening.
• Positive urine toxicology panel (barbiturates, THC, amphetamines/methamphetamines, methadone, MDMA, phencyclidine, tricyclic antidepressants, benzodiazepines, opiates, cocaine) or positive alcohol breath test.
• Unwilling to abstain from alcohol, caffeine and nicotine from 48 h prior to admission, during confinement, and 48 h prior to follow-up visits.
• History of substance abuse/dependency or recreational IV drug use in the last 12 months (self-declared).
• Unwilling to refrain from strenuous exercise (incl. weightlifting) 48 h prior to admission and follow-up visits.
• Anything the Investigator considers would jeopardize participant safety, prevent full participation, or compromise data interpretation.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Non-Randomized
• Interventional Model: Sequential Assignment
• Masking: None (Open Label)

Number of Arms

5

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Cohort 1: Viaca 25/0.25 mg; Single oral dose of Viaca (sildenafil 25 mg / cabergoline 0.25 mg; one low-dose tablet) in 6 healthy male participants.	Drug: Viaca; fixed-dose oral tablet of sildenafil + cabergoline (low-dose 25/0.25 mg; high-dose 50/0.5 mg). Single oral dose.
Experimental: Cohort 2: Viaca 50/0.5 mg; Single oral dose of Viaca (sildenafil 50 mg / cabergoline 0.5 mg; one high-dose tablet	Drug: Viaca; fixed-dose oral tablet of sildenafil + cabergoline (low-dose 25/0.25 mg; high-dose 50/0.5 mg). Single oral dose.
Experimental: Cohort 3: Viaca 75/0.75 mg; Single oral dose of Viaca (sildenafil 75 mg / cabergoline 0.75 mg; one low + one high tablet	Drug: Viaca; fixed-dose oral tablet of sildenafil + cabergoline (low-dose 25/0.25 mg; high-dose 50/0.5 mg). Single oral dose.
Active Comparator: Cohort 4: Sildenafil 50 mg; Single oral dose of sildenafil 50 mg (two 25 mg tablets).	Drug: Sildenafil 50 mg; single oral dose
Active Comparator: Cohort 5: Cabergoline 0.5 mg; Single oral dose of cabergoline 0.5 mg (one 0.5 mg tablet).	Drug: Cabergoline 0.5 MG; single oral dose

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Participants with AEs/SAEs	Number of participants with treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs). Unit: participants (summarised by severity and relatedness).	Day 1 (dosing) through Day 8
Blood pressure	Change from Baseline in systolic and diastolic blood pressure. Unit: mmHg.	Baseline through Day 8.
Pulse rate	Change from Baseline in pulse rate. Unit: beats/min.	Baseline through Day 8.
Respiratory rate	Change from Baseline in respiratory rate. Unit: breaths/min.	Baseline through Day 8.
Body temperature	Change from Baseline in body temperature. Unit: °C.	Baseline through Day 8.
ECG heart rate	Change from Baseline in 12-lead ECG heart rate. Unit: beats/min.	Baseline through Day 8.
ECG intervals	Change from Baseline in 12-lead ECG intervals (QTcF, PR, QRS). Unit: milliseconds.	Baseline through Day 8.
Laboratory tests	Number of participants with clinically significant safety laboratory abnormalities. Unit: participants.	Baseline through Day 8.
Physical examination	Number of participants with clinically significant physical examination findings. Unit: participants.	Baseline through Day 8.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Cmax	Maximum observed plasma concentration (Cmax). Unit: e.g. ng/mL.	Predose (Day 1) through 168 hours post-dose (Day 8).
Tmax	Time to maximum plasma concentration (Tmax). Unit: hours.	Predose (Day 1) through 168 hours post-dose (Day 8).
AUC0-t	Area under the plasma concentration-time curve from time 0 to the last measurable concentration (AUC0-t). Unit: e.g. ng·h/mL.	Predose (Day 1) through 168 hours post-dose (Day 8)
AUC0-24	AUC from time 0 to 24 hours (AUC0-24). Unit: e.g. ng·h/mL.	Predose (Day 1) through 168 hours post-dose (Day 8).
AUC0-inf	AUC from time 0 extrapolated to infinity (AUC0-inf). Unit: e.g. ng·h/mL.	Predose (Day 1) through 168 hours post-dose (Day 8).
%AUCextrap	Percentage of AUC0-inf obtained by extrapolation (%AUCextrap). Unit: percentage.	Predose (Day 1) through 168 hours post-dose (Day 8).
t½	Apparent terminal elimination half-life (t½). Unit: hours.	Predose (Day 1) through 168 hours post-dose (Day 8).
kel	Terminal elimination rate constant (kel). Unit: 1/hour.	Predose (Day 1) through 168 hours post-dose (Day 8).
CL/F	Apparent total clearance after oral dosing (CL/F). Unit: e.g. L/h.	Predose (Day 1) through 168 hours post-dose (Day 8).
Vz/F	Apparent volume of distribution during the terminal phase after oral dosing (Vz/F). Unit: e.g. L.	Predose (Day 1) through 168 hours post-dose (Day 8).
Cmax/D	Dose-normalised maximum plasma concentration (Cmax/D). Unit: e.g. ng/mL per mg.	Predose (Day 1) through 168 hours post-dose (Day 8).
AUC0-inf/D	Dose-normalised AUC0-inf (AUC0-inf/D). Unit: e.g. ng·h/mL per mg.	Predose (Day 1) through 168 hours post-dose (Day 8).
AUC0-t/D	Dose-normalised AUC0-t (AUC0-t/D). Unit: e.g. ng·h/mL per mg.	Predose (Day 1) through 168 hours post-dose (Day 8).
Dose proportionality	Dose proportionality of Cmax and AUC across Viaca dose levels. Unit: e.g. slope (power-model estimate).	Predose (Day 1) through 168 hours post-dose (Day 8).

Collaborators and Investigators

• Sponsor: Yanping Kong
• Collaborators: Novotech (Australia) Pty Limited
• Investigators: Principal Investigator: Emma Trowbridge, MD, Nucleus Network Brisbane

Study record dates

Study Major Dates

• Study Start (Estimated): August 1, 2026
• Primary Completion (Estimated): September 19, 2026
• Study Completion (Estimated): September 19, 2026

Study Registration Dates

• First Submitted: July 13, 2026
• First Submitted That Met QC Criteria: July 23, 2026
• First Posted (Actual): July 28, 2026

Study Record Updates

• Last Update Posted (Actual): July 28, 2026
• Last Update Submitted That Met QC Criteria: July 23, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: pharmacokinetics; sildenafil; erectile dysfunction; Phase 1; healthy volunteers; single ascending dose; dopamine agonist; PDE5 inhibitor; cabergoline; fixed-dose combination; viaca
• Additional Relevant MeSH Terms: Urogenital Diseases; Genital Diseases; Mental Disorders; Genital Diseases, Male; Male Urogenital Diseases; Sexual Dysfunction, Physiological; Sexual Dysfunctions, Psychological; Erectile Dysfunction; Sulfur Compounds; Organic Chemicals; Heterocyclic Compounds, 1-Ring; Heterocyclic Compounds; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring; Alkaloids; Amides; Purines; Heterocyclic Compounds, 4 or More Rings; Sulfonamides; Sulfones; Piperazines; Ergot Alkaloids; Ergolines; Sildenafil Citrate; Cabergoline
• Other Study ID Numbers: CR-067-001; EC00372 (Other Identifier: Bellberry HREC code); 462/26 (Other Identifier: Alfred governance)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No