CLINICAL TRIALS PROFILE FOR VIAGRA

All Clinical Trials for VIAGRA

Trial ID	Title	Status	Sponsor	Phase	Start Date	Summary
NCT00056433 ↗	Evaluation of Hydroxyurea Plus L-arginine or Sildenafil to Treat Sickle Cell Anemia	Completed	National Institutes of Health Clinical Center (CC)	Phase 1	2003-03-10	Patients with sickle cell disease have abnormal hemoglobin (the protein in red blood cells that carries oxygen to the body). This abnormality causes red blood cells to take on a sickle shape, producing disease symptoms. Fetal hemoglobin, a type of hemoglobin present in fetuses and babies, can prevent red cells from sickling. The drug hydroxyurea increases fetal hemoglobin production in patients with sickle cell disease by making a molecule called nitric oxide. The drugs L-arginine and Sildenafil (Viagra) increase the amount or the effect of nitric oxide. This study will evaluate: - The safety of giving L-arginine or Sildenafil together with hydroxyurea in patients with sickle cell disease; - The effectiveness of L-arginine plus hydroxyurea or Sildenafil plus hydroxyurea in increasing fetal hemoglobin in patients with sickle cell disease; and - The effectiveness of L-arginine plus hydroxyurea or Sildenafil and hydroxyurea in lowering blood pressure in the lungs of patients with sickle cell disease. (Pulmonary blood pressure is elevated in about one-third of patients with sickle cell disease, and this condition increases the risk of dying from the disease.) Patients with hemoglobin S-only, S-beta-thalassemia, or other sickle cell disease genotype may be eligible for this study. Before starting treatment, patients will have a complete medical history and physical examination. All patients will take hydroxyurea once a day every day by mouth for at least 2 months. They will be admitted to the NIH Clinical Center to take their first dose of hydroxyurea, and will have blood drawn through a catheter (plastic tube placed in a vein) every hour for 6 hours for tests to determine nitric oxide levels. After discharge, they will return to the clinic once every 2 weeks to check for treatment side effects and for blood tests to monitor hemoglobin and fetal hemoglobin levels. After fetal hemoglobin levels have been stable for 2 months, patients will be admitted to the Clinical Center for their first dose of L-arginine (for men) or Sildenafil (for women). Again, blood samples will be collected through a catheter once an hour for 6 hours. If there are no complications, patients will be discharged and will continue taking hydroxyurea once a day and L-arginine or Sildenafil three times a day for at least 3 months until fetal hemoglobin levels have been stable for at least 2 months. Patients will return to the clinic for blood tests every week for 2 weeks and then every 2 weeks to monitor hemoglobin and fetal hemoglobin levels and to check for treatment side effects. Patients will have eye examinations before and during treatment. Some patients with sickle cell disease develop abnormalities in the blood vessels of the eye. Also, Sildenafil can cause temporary changes in color vision. Rarely, more serious eye problems can occur, such as bleeding from the eye blood vessels or damage to the retina a layer of tissue that lines the back of the eye. Patients will also have an echocardiogram (ultrasound of the heart) before beginning treatment, after hydroxyurea treatment, and after 1 and 3 months of combined treatment with hydroxyurea and L-arginine or Sildenafil to help measure blood pressure in the lungs. Patients who develop complications from L-arginine or Sildenafil may continue in the study on hydroxyurea alone. Patients whose fetal hemoglobin levels increase with the combination therapy of hydroxyurea and L-arginine or Sildenafil may continue to take them.
NCT00080808 ↗	Nerve-Sparing Radical Prostatectomy With or Without Nerve Grafting Followed by Standard Therapy for Erectile Dysfunction in Treating Patients With Localized Prostate Cancer	Completed	National Cancer Institute (NCI)	Phase 2	2001-08-01	RATIONALE: Nerve-sparing radical prostatectomy with nerve grafting followed by standard therapies for erectile dysfunction may be effective in helping patients with prostate cancer improve sexual satisfaction and quality of life. It is not yet known whether erectile dysfunction therapy and nerve-sparing prostatectomy are more effective with or without nerve grafting. PURPOSE: This randomized phase II trial is studying nerve grafting and standard therapy to see how well they work compared to standard therapy alone in treating erectile dysfunction in patients undergoing nerve-sparing radical prostatectomy for localized prostate cancer.
NCT00080808 ↗	Nerve-Sparing Radical Prostatectomy With or Without Nerve Grafting Followed by Standard Therapy for Erectile Dysfunction in Treating Patients With Localized Prostate Cancer	Completed	M.D. Anderson Cancer Center	Phase 2	2001-08-01	RATIONALE: Nerve-sparing radical prostatectomy with nerve grafting followed by standard therapies for erectile dysfunction may be effective in helping patients with prostate cancer improve sexual satisfaction and quality of life. It is not yet known whether erectile dysfunction therapy and nerve-sparing prostatectomy are more effective with or without nerve grafting. PURPOSE: This randomized phase II trial is studying nerve grafting and standard therapy to see how well they work compared to standard therapy alone in treating erectile dysfunction in patients undergoing nerve-sparing radical prostatectomy for localized prostate cancer.
NCT00090376 ↗	Evaluate the Effects of GPI 1485 on Erectile Function Following Bilateral Nerve-Sparing Prostatectomy	Completed	Symphony Neuro Development Company	Phase 2	2003-12-01	In this phase II study, an investigative (not approved by the FDA) drug called GPI 1485 is being assessed to see if it can help preserve erectile function after prostatectomy.

Clinical Trial Conditions for VIAGRA

Condition Name

Condition Name for VIAGRA
Intervention	Trials
Erectile Dysfunction	32
Impotence	17
Prostate Cancer	7
Pulmonary Hypertension	6

Condition MeSH

Condition MeSH for VIAGRA
Intervention	Trials
Erectile Dysfunction	51
Hypertension	27
Hypertension, Pulmonary	16
Prostatic Neoplasms	7

Clinical Trial Locations for VIAGRA

Trials by Country

Trials by Country for VIAGRA
Location	Trials
United States	206
Canada	17
United Kingdom	13
Australia	10
Denmark	9

Trials by US State

Trials by US State for VIAGRA
Location	Trials
California	17
Texas	17
New York	15
Ohio	10
Maryland	10

Clinical Trial Progress for VIAGRA

Clinical Trial Phase

Clinical Trial Phase for VIAGRA
Clinical Trial Phase	Trials
PHASE1	4
Phase 4	50
Phase 3	14

Clinical Trial Status

Clinical Trial Status for VIAGRA
Clinical Trial Phase	Trials
Completed	99
Unknown status	21
Terminated	18

Clinical Trial Sponsors for VIAGRA

Sponsor Name

Sponsor Name for VIAGRA
Sponsor	Trials
Pfizer	34
Pfizer's Upjohn has merged with Mylan to form Viatris Inc.	23
The University of Texas Medical Branch, Galveston	5

Sponsor Type

Sponsor Type for VIAGRA
Sponsor	Trials
Other	174
Industry	88
NIH	17

Viagra (sildenafil) Clinical Trials Update, Market Analysis, and Projection

Last updated: April 27, 2026

What is Viagra’s current clinical-development footprint?

Viagra is an approved, long-established product (sildenafil). Public-facing “clinical trials updates” for the brand today skew toward label maintenance, formulation work, real-world evidence, and lifecycle/next-generation programs rather than new pivotal Phase 3 efficacy studies for the core indication set.

Core regulatory positioning (approved uses)

Sildenafil is marketed for:

• Erectile dysfunction (ED) in men
• Pulmonary arterial hypertension (PAH) as Revatio (separate brand, same active ingredient at different dose forms/strengths and indication set) [1,2]

This split matters for market forecasting because ED demand is driven by broader population and off-target cardiometabolic comorbidity dynamics, while PAH demand is smaller and more competitive across specialty classes.

Clinical trial activity: what is typically still being run

For sildenafil products, ongoing study types that still appear in the literature and registries include:

• Bioavailability/biostudy and formulation comparisons (including new salt forms, tablet strengths, or manufacturing scale-up)
• Real-world and adherence studies in ED populations
• Subgroup analyses tied to cardiovascular comorbidity and concomitant medication use (especially nitrates and alpha-blocker interactions)
• Adolescent/rare subgroup studies are generally limited; sildenafil’s core ED indications are adult-focused in major markets

How does sildenafil’s patent landscape shape investment timing?

Sildenafil’s original compositions and early-use protection are long expired across major jurisdictions; today’s competitive edge rests on:

• Manufacturing cost and supply chain scale
• Formulation differentiation
• Branding and payer contracting for ED
• PAH-specific competition in Revatio positioning

That means “new clinical trials for the brand” are not the dominant market lever. The dominant lever is commercial execution in a heavily genericized environment.

What does the market look like today for Viagra-style ED therapy?

Market structure

The ED market is dominated by:

• PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil)
• Generic saturation that compresses pricing and shifts value to volume, rebates, and distribution
• Payer and channel mix that increasingly favors lower net cost

Sildenafil’s commercial performance typically reflects:

• Competitive pricing vs tadalafil and avanafil
• Margin discipline across generics
• Brand-market persistence in cash-pay segments and some reimbursed settings

Drivers (demand-side)

• Aging demographics and ED prevalence
• Continued physician familiarity and guideline inclusion for PDE5 inhibitors as first-line ED pharmacotherapy (guideline framing varies by region) [3]
• Improved access via generics and e-commerce distribution channels

Constraints (supply and compliance)

• Strict contraindication labeling around nitrates and urgent cardiovascular scenarios
• Drug interaction management with alpha-blockers and antihypertensives (clinical labeling is explicit) [1,2]
• Intensified compliance and pharmacovigilance monitoring in many markets

What is the competitive set and where does sildenafil typically win?

Within PDE5 inhibitors for ED, sildenafil competes primarily against:

• Tadalafil (longer duration positioning)
• Vardenafil and Avanafil (alternative onset/dosing profiles)
• Multiple generic sildenafil products

Sildenafil’s typical relative strengths:

• Competitive pricing as a mature generic
• Broad clinician familiarity and established efficacy dataset
• Flexible dosing schedules with multiple strengths (where available)

Sildenafil’s typical relative disadvantages:

• Shorter perceived duration than tadalafil (a key patient preference driver)
• Brand value erodes as generic volumes expand

How should you project sildenafil/Viagra revenues?

A credible projection framework for Viagra must treat the product as mature, generic-dominated, with growth driven by volume elasticity and share shifts rather than clinical breakthroughs.

Projection model (mechanics you can use)

Forecast annual revenue for “Viagra” as:

• Net price trend (declining or flat vs generic benchmarks)
• Volume trend (population growth + access expansion + channel shift)
• Share shifts within PDE5 class (tadalafil vs sildenafil)

Because public, brand-specific historical sales for “Viagra” are not provided in the supplied sources here, the most defensible projection is scenario-based by market mechanics rather than brand-only unit claims.

Scenario bands (directional, not brand-only claims)

• Base case: low-to-mid single digit volume growth with continued net price pressure yields flat to modest decline in mature brand economics, with potential stabilization where rebate contracting supports net margins.
• Downside: faster price erosion from aggressive generic competition plus share loss to longer-duration PDE5 inhibitors yields mid single digit revenue decline.
• Upside: stable payer position, sustained physician prescribing habits, and tighter channel competition vs peers yields low growth even with price pressure.

What are the key market KPI signals to watch?

Commercial KPI set

• Wholesale pricing indices for generic sildenafil (proxy for net pricing)
• Pharmacy channel penetration (mail order vs retail share)
• Rebate and payer formulary moves for PDE5 inhibitor tiers
• Script counts for PDE5 inhibitors in ED

Clinical and regulatory KPI set

• Labeling updates tied to safety warnings and interaction management (nitrates)
• Any new class safety communications that alter patient eligibility

What sources anchor the clinical and regulatory facts?

• Pfizer’s Viagra prescribing information provides contraindications, dosing guidance, and safety warnings including nitrate interactions and cardiovascular risk management [1].
• FDA label access for sildenafil products includes consistent warnings and use conditions [2].
• Guideline frameworks for ED pharmacotherapy often place PDE5 inhibitors as first-line options, with selection by patient risk profile and preference [3].

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Key Takeaways

• Viagra (sildenafil) is a mature, heavily genericized ED therapy where clinical trial “updates” are less likely to drive market growth than commercial execution and price-volume dynamics.
• The sildenafil market is structured around ED (Viagra) versus PAH (Revatio), which changes the addressable market size and competitive context.
• Near-term forecasting should emphasize net price erosion vs volume growth and share movement within PDE5 inhibitors, especially competition from longer-duration agents.
• The most investable levers are manufacturing economics, contracting strategy, and lifecycle/formulation tactics, not new pivotal ED efficacy trials.

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FAQs

1) Is Viagra still being studied in clinical trials?

Yes, but most public activity tends to be formulation/bioavailability studies and real-world evidence rather than new pivotal efficacy trials for established ED indications.

2) Why do nitrates matter for Viagra’s market and clinical use?

Viagra’s prescribing information includes nitrate contraindication due to risk of unsafe blood pressure reduction, which affects eligibility and prescribing patterns [1,2].

3) Does sildenafil’s PAH product change how investors should forecast?

Yes. Revatio (PAH) targets a smaller specialty market with different payer and competitive dynamics than Viagra (ED) [1,2].

4) What drives sildenafil revenue in a generic-dominated market?

Revenue is driven by script volumes, net pricing after rebates, and share shifts within PDE5 inhibitors, not by breakthrough new clinical efficacy.

5) Which competitor class dynamic most affects sildenafil?

Longer perceived duration competitors (notably tadalafil) often shift patient preference, impacting market share within the PDE5 class.

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References

[1] Pfizer. (n.d.). Viagra (sildenafil) prescribing information. Pfizer Inc.
[2] U.S. Food and Drug Administration. (n.d.). Viagra (sildenafil citrate) label and safety information. FDA.
[3] [Guideline source]. (n.d.). Erectile dysfunction pharmacotherapy recommendations emphasizing PDE5 inhibitors as first-line treatment.