Gender DysphoriaPhase 2/3NCT05897086
Polyethylene-glycol Assisted Nerve Repair in Phalloplasty
A Phase 2/3 study testing Polyethylene Glycol 3350 in people with Gender Dysphoria, run by Vanderbilt University Medical Center at 1 site in United States.
Trial summary
Phalloplasty, a genitourinary surgery for transmasculine patients, reconstructs a neophallus using tissue transferred from other parts of the body to the groin. However, this technique fails to provide adequate sensation, causing regret and persistent dysphoria. Read more about this study
- Who is it for?
- Ages 18 years and older, women only
- Conditions the study is for
- Gender Dysphoria
- What is being tested?
- Polyethylene Glycol 3350
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 30 participants
- Where
- 1 siteUnited States
- Study dates
- 1 Aug 2023to 1 Dec 2029
- Phase
- Phase 2/3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- Women only
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- over the age of 18
- preoperative diagnosis of gender dysphoria and present for planned radial forearm free flap phalloplasty
- willing to comply with all aspects of treatment as well as the study evaluation schedule
Who cannot join
- a known allergy to the study drug
- a hematocrit of 54% or higher
- a history of venous thromboembolism (VTE), peripheral phlebitis, stroke, or myocardial infarction within the last 6 months.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site
Vanderbilt University Medical Center
Nashville, Tennessee, 37232
About this study
Official title: Nerve Repair Using Hydrophilic Polymers to Improve Tactile and Erogenous Neophallus Sensation
Phalloplasty, a genitourinary surgery for transmasculine patients, reconstructs a neophallus using tissue transferred from other parts of the body to the groin. However, this technique fails to provide adequate sensation, causing regret and persistent dysphoria. Peripheral nerve regeneration is the greatest barrier to sensory recovery, given the slow rate of regrowth coupled with the negative effects of axonal degeneration. Topical application of polyethylene glycol (PEG) fuses severed axonal membranes, restoring the nerve's immediate ability to conduct electrical signals across the repair site. The investigators hypothesize that utilizing PEG in phalloplasties will significantly improve neophallus sensation and postoperative quality of life.
Read the detailed description
With more than 1.6 million transgender and nonbinary (TGNB) individuals in the United States, the investigators have witnessed an exponential increase in the number of gender-affirming surgeries performed in the last 2 decades. Of the affirming surgical spectrum, "bottom" genitourinary surgeries remain the most challenging. Specifically, phalloplasty is a masculinizing surgery for neophallus creation using free tissue transfer from other parts of the body and microvascular techniques for nerve and vessel reattachment. In radial forearm free flap (RFFF) phalloplasty, nerves from the forearm are harvested with the flap and sutured to nerves in the groin to provide postoperative sensation in the neophallus. Despite transmasculine patients ranking sensation as one of their top priorities, standard nerve coaptations performed in phalloplasty fail to provide consistent sensation with scarce dedicated research aimed at enhancing neophallus sensory outcomes. Without scientific advances, phalloplasty will remain far from perfect, negatively affecting patients' sexual health, causing dissatisfaction, and increasing the risk of surgical regret and persistent dysphoria.
Peripheral nerve regeneration remains the limiting factor for ideal sensory recovery due to the slow and inconsistent rates of regeneration, and the negative effects of axonal degeneration that occurs post-injury. The investigators advocate for using polyethylene glycol as a "fusogen" to achieve nerve fusion in peripheral nerve coaptations. Polyethylene glycol (PEG) is a hydrophilic compound that enhances the fusion of the lipid bilayer membrane of severed axons, restoring the nerve's immediate ability to conduct electrical signals across the repair site. The investigators have conducted extensive mammalian and preliminary human studies using our novel PEG-fusion protocol for nerve coaptations. In both ex-vivo and in-vivo studies in rats with severed sciatic nerves, PEG-assisted nerve coaptation restored morphological continuity and led to a remarkable early improvement in functional outcomes. In the first human PEG fusion of injured digital nerves performed by our team, the investigators saw rapid nerve recovery and early functional outcomes as early as one week. Based on the investigator's experience with PEG fusion, the investigators will be conducting a randomized clinical trial to test the efficacy of PEG-assisted nerve coaptation in achieving superior neophallus sensory function following phalloplasty.
- Conditions
- Gender Dysphoria
- Being tested
- Polyethylene Glycol 3350
- Keywords
- Phalloplasty
- Medical subject headings
- Gender Dysphoria
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Polyethylene Glycol 3350Drug
Topical irrigation with approximately 2 ccs of a 190 mM solution of 50% PEG 3.35 kD in sterile water
| Study group | Role | What they receive |
|---|---|---|
| Control (No Intervention) | No intervention | For the control groups, epineural repair will be undertaken in the standard end-to-end fashion using interrupted nylon suture after irrigation of the wound with normal saline as deemed necessary by the operating surgeon. |
| Experimental | Experimental | For the experimental group, after obtaining hemostasis, prior to neurorrhaphy, the operative field will be irrigated with calcium-free Plasmalyte A® (Baxter: Deerfield, IL) throughout the neurorrhaphy. At this point, the nerves will be repaired using standard suture neurorrhaphy techniques. Subsequently, approximately 1 or 2 drops of 5mg/ml (0.5%) methylene blue in sterile water solution are applied to the trimmed nerve endings. Then, approximately 2 ccs of a 190 mM solution of 50% PEG 3.35 kD in sterile water will be irrigated onto the neurorrhaphy site and the surgeon will wait one minute prior to continuing. Following this, the repaired nerve will be irrigated with calcium-containing Lactated Ringers (Hospira; Lake Forest, IL). Receives: Drug: Polyethylene Glycol 3350 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Medical Research Council Classification (MRCC)
measures sensory recovery
Measured: 15 months
Secondary outcomes (2)
Vanderbilt Mini-PROM for Gender-Affirming Surgery(VMP-G)
This questionnaire measures psychosocial well-being and resolution of gender-dysphoria
Measured: 15 months
Sexual Functioning and Sensation Questionnaire
measures sexual function and subjective/erogenous sensation
Measured: 15 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted9 Jun 2023
- Study start1 Aug 2023
- Primary completion30 Dec 2028 (estimated)
- Study completion1 Dec 2029 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Gender DysphoriaStudies of the same condition, open and under way.
- More trials run by Vanderbilt University Medical CenterThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2/3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind
- Who is masked
- Participant, Outcomes assessor
- Enrolment
- 30 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Vanderbilt University Medical Center
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Wesley Thayer, Vanderbilt University Medical Center
- Investigators
- Wesley Thayer, MD, Principal investigator, Vanderbilt University Medical Center
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05897086
- Sponsor's protocol ID
- 221616
- Status last verified
- Oct 2025
- First submitted
- 1 Jun 2023
- Last updated
- 20 Oct 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 20 Oct 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Nerve Repair Using Hydrophilic Polymers to Improve Tactile and Erogenous Neophallus Sensation
- ClinicalTrials.gov ID
- NCT05897086
- Acronym / sponsor ID
- 221616
- Conditions
- Gender Dysphoria
- Keywords
- Phalloplasty
- Phase
- Phase 2/3
- Study type
- Interventional
- Recruitment status
- Enrolling by invitation
- Enrolment
- 30 participants (estimated)
- Lead sponsor
- Vanderbilt University Medical CenterUniversity, hospital or other
- Study start
- 1 Aug 2023 (actual)
- Primary completion
- 30 Dec 2028 (estimated)
- Study completion
- 1 Dec 2029 (estimated)
- First posted
- 9 Jun 2023 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Phalloplasty, a genitourinary surgery for transmasculine patients, reconstructs a neophallus using tissue transferred from other parts of the body to the groin. However, this technique fails to provide adequate sensation, causing regret and persistent dysphoria. Peripheral nerve regeneration is the greatest barrier to sensory recovery, given the slow rate of regrowth coupled with the negative effects of axonal degeneration. Topical application of polyethylene glycol (PEG) fuses severed axonal membranes, restoring the nerve's immediate ability to conduct electrical signals across the repair site. The investigators hypothesize that utilizing PEG in phalloplasties will significantly improve neophallus sensation and postoperative quality of life.
Detailed description
With more than 1.6 million transgender and nonbinary (TGNB) individuals in the United States, the investigators have witnessed an exponential increase in the number of gender-affirming surgeries performed in the last 2 decades. Of the affirming surgical spectrum, "bottom" genitourinary surgeries remain the most challenging. Specifically, phalloplasty is a masculinizing surgery for neophallus creation using free tissue transfer from other parts of the body and microvascular techniques for nerve and vessel reattachment. In radial forearm free flap (RFFF) phalloplasty, nerves from the forearm are harvested with the flap and sutured to nerves in the groin to provide postoperative sensation in the neophallus. Despite transmasculine patients ranking sensation as one of their top priorities, standard nerve coaptations performed in phalloplasty fail to provide consistent sensation with scarce dedicated research aimed at enhancing neophallus sensory outcomes. Without scientific advances, phalloplasty will remain far from perfect, negatively affecting patients' sexual health, causing dissatisfaction, and increasing the risk of surgical regret and persistent dysphoria.
Peripheral nerve regeneration remains the limiting factor for ideal sensory recovery due to the slow and inconsistent rates of regeneration, and the negative effects of axonal degeneration that occurs post-injury. The investigators advocate for using polyethylene glycol as a "fusogen" to achieve nerve fusion in peripheral nerve coaptations. Polyethylene glycol (PEG) is a hydrophilic compound that enhances the fusion of the lipid bilayer membrane of severed axons, restoring the nerve's immediate ability to conduct electrical signals across the repair site. The investigators have conducted extensive mammalian and preliminary human studies using our novel PEG-fusion protocol for nerve coaptations. In both ex-vivo and in-vivo studies in rats with severed sciatic nerves, PEG-assisted nerve coaptation restored morphological continuity and led to a remarkable early improvement in functional outcomes. In the first human PEG fusion of injured digital nerves performed by our team, the investigators saw rapid nerve recovery and early functional outcomes as early as one week. Based on the investigator's experience with PEG fusion, the investigators will be conducting a randomized clinical trial to test the efficacy of PEG-assisted nerve coaptation in achieving superior neophallus sensory function following phalloplasty.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind (participant, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Control (No Intervention) | No intervention | –For the control groups, epineural repair will be undertaken in the standard end-to-end fashion using interrupted nylon suture after irrigation of the wound with normal saline as deemed necessary by the operating surgeon. |
| Experimental | Experimental | Drug: Polyethylene Glycol 3350For the experimental group, after obtaining hemostasis, prior to neurorrhaphy, the operative field will be irrigated with calcium-free Plasmalyte A® (Baxter: Deerfield, IL) throughout the neurorrhaphy. At this point, the nerves will be repaired using standard suture neurorrhaphy techniques. Subsequently, approximately 1 or 2 drops of 5mg/ml (0.5%) methylene blue in sterile water solution are applied to the trimmed nerve endings. Then, approximately 2 ccs of a 190 mM solution of 50% PEG 3.35 kD in sterile water will be irrigated onto the neurorrhaphy site and the surgeon will wait one minute prior to continuing. Following this, the repaired nerve will be irrigated with calcium-containing Lactated Ringers (Hospira; Lake Forest, IL). |
Who may qualify
- Ages
- 18 years and older
- Sex
- Female only
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- over the age of 18
- preoperative diagnosis of gender dysphoria and present for planned radial forearm free flap phalloplasty
- willing to comply with all aspects of treatment as well as the study evaluation schedule
Key exclusion criteria (3 listed)
- a known allergy to the study drug
- a hematocrit of 54% or higher
- a history of venous thromboembolism (VTE), peripheral phlebitis, stroke, or myocardial infarction within the last 6 months.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Polyethylene Glycol 3350Topical irrigation with approximately 2 ccs of a 190 mM solution of 50% PEG 3.35 kD in sterile water | Drug | Experimental |
Primary outcome
Medical Research Council Classification (MRCC)
Time frame: 15 months
measures sensory recovery
2 secondary outcomes
Vanderbilt Mini-PROM for Gender-Affirming Surgery(VMP-G)
Time frame: 15 months
Sexual Functioning and Sensation Questionnaire
Time frame: 15 months
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 20 Oct 2025.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Wesley Thayer, MD principal investigator
Vanderbilt University Medical Center
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2/3 study testing Polyethylene Glycol 3350 in people with Gender Dysphoria, run by Vanderbilt University Medical Center at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: enrolling by invitation, as of the sponsor's last update on 20 Oct 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this combined phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Medical Research Council Classification (MRCC) (time frame: 15 months). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 20 Oct 2025.