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

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
83

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • 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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

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

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
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

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
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

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
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

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
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)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
May 1, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
April 1, 2027

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
May 1, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
May 15, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 15, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
May 22, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
May 22, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 20, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant 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.

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