A Single-Arm, Dose Escalation of an Intraurethral Alprostadil Paste for Erectile Dysfunction

May 20, 2026 updated by: Ryan Flannigan, MD

Phase 2 Clinical Trial of ST-04 Intraurethral Paste for Erectile Dysfunction

This is a single arm dose escalation trial of a mucoadhesive intraurethral polymer suspension of alprostadil (ST-04) and will investigate the efficacy of 3 dose levels of ST-04 in adult males with a clinical diagnosis of Erectile Dysfunction (ED). This study aims to determine if ST-04, with or without sildenafil, will improve erectile function (EF) compared to baseline.

Participants in this study will receive ST-04, a new formulation containing the vasodilator, alprostadil which is known to be an effective drug in treating erectile dysfunction. ST-04 will be dispersed along the urethra, forming a hydrogel which adheres to the lining of the urethra with the goal of penile tumescence and erection. Participants may receive up to 3 dose level escalations of ST-04 over a 12-week period, for a total of up to 11 administrations of ST-04. Dose escalation may also be done with and without sildenafil.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

83

Phase

  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Canada
    • British Columbia
      • Vancouver, British Columbia, Canada, V5Z1M9
        • Recruiting
        • Vancouver Prostate Centre
        • Principal Investigator:
          • Ryan Flannigan, MD
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Have had a confirmed clinical diagnosis of ED for more than three months based upon IIEF
  • Have failed PDE5 inhibitor therapy (inability to achieve an erection with adequate rigidity to allow penetrative sex)
  • Ability to take oral medication (sildenafil) and be willing to adhere to the study intervention regimen
  • Engaged in heterosexual relationship with partner for a minimum of 6 months

Exclusion Criteria:

  • History of unstable medical or psychiatric condition that, in the opinion of the principal investigator, could impact the patient's ability to complete the study investigations or protocol.
  • Spinal cord injury, or penile anatomical abnormalities
  • Cardiovascular conditions that prevent sexual activity (NYHA Class II or higher, any angina, or uncontrolled CHF or severe coronary artery disease)
  • History of myocardial infarction, stroke, or life-threatening arrhythmia within 6 months prior to enrollment into the study
  • Use of anti-androgens, or oral or injectable androgens
  • Documented hypotension or known orthostatic hypotension
  • Use of oral, topical or sublingual nitrates within 3 months prior to enrollment into the study
  • Hepatic (Child-Pugh Class C) or renal failure (eGFR < 30)
  • Inadequate response to intracavernosal injection therapy previously
  • Peyronie's disease or Meatal stenosis

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Single-Arm Dose Escalation
Dose Level 1 is 500 μg of ST-04; Dose Level 2 is 1000 μg of ST-04 with or without Sildenafil; Dose Level 3 is 1500 μg of ST-04 with or without Sildenafil.
Drug: ST-04
ST-04 consists of an alprostadil polymer suspension designed for intraurethral application

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change from Baseline in the Erectile Function Domain of the IIEF Questionnaire
Time Frame: From baseline to 1 month after start of the last dose level (Week 4, 8, 12 respectively)
The IIEF is a validated questionnaire assessing erectile function, with total scores ranging from 5 to 25; higher scores indicate better erectile function
From baseline to 1 month after start of the last dose level (Week 4, 8, 12 respectively)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change from Baseline in the Erectile Hardness Scale (EHS)
Time Frame: From baseline to the end of treatment at week 4, 8 or 12 respectively
The EHS is a self-reported assessment of penile hardness on a scale of 0 (no engorgement) to 4 (complete rigidity).
From baseline to the end of treatment at week 4, 8 or 12 respectively
Change from Baseline in the Sexual Encounter Profile (SEP)
Time Frame: From baseline to the end of treatment at week 4, 8 or 12 respectively
SEP is a log diary completed after each sexual attempt, providing information as to whether the erection was hard enough to penetrate (SEP 2), or whether it was maintained for completion (SEP 3).
From baseline to the end of treatment at week 4, 8 or 12 respectively
Percentage of Uses per Participant of ST-04 which Led to the Onset of Erection within up to 30 minutes of Application per Number of Intercourse Attempts
Time Frame: From baseline to the end of treatment at week 4, 8 or 12 respectively
Percentage of participants using ST-04 that could achieve an erection and/or penetrative intercourse within 30 minutes of application per number of intercourse attempts.
From baseline to the end of treatment at week 4, 8 or 12 respectively
Incidence and Severity of Adverse events
Time Frame: From baseline to the end of treatment at week 4, 8 or 12 respectively
Adverse events will be recorded at each follow-up visit and classified by type, severity, and relationship to the intervention.
From baseline to the end of treatment at week 4, 8 or 12 respectively

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Ryan Flannigan, MD

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

May 1, 2026

Primary Completion (Estimated)

April 1, 2027

Study Completion (Estimated)

May 1, 2027

Study Registration Dates

First Submitted

May 15, 2026

First Submitted That Met QC Criteria

May 15, 2026

First Posted (Actual)

May 22, 2026

Study Record Updates

Last Update Posted (Actual)

May 22, 2026

Last Update Submitted That Met QC Criteria

May 20, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • H25-00542

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Erectile Dysfunctions

Clinical Trials on ST-04

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

CROs by country

CROs in Ecuador

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Subscribe