CLINICAL TRIALS PROFILE FOR LETAIRIS

All Clinical Trials for LETAIRIS

Trial ID	Title	Status	Sponsor	Phase	Start Date	Summary
NCT00380068 ↗	Safety and Efficacy Study of Ambrisentan in Subjects With Pulmonary Hypertension	Completed	Gilead Sciences	Phase 3	2006-08-01	The primary objective of this study was to evaluate the safety and efficacy of ambrisentan in a broad population of participants with pulmonary hypertension (PH). Secondary objectives of this study were to evaluate the effects of ambrisentan on other clinical measures of pulmonary arterial hypertension (PAH), long-term treatment success, and survival.
NCT00617305 ↗	Study of Add-on Ambrisentan Therapy to Background Phosphodiesterase Type-5 Inhibitor (PDE5i) Therapy in Pulmonary Arterial Hypertension (ATHENA-1)	Completed	Gilead Sciences	Phase 4	2008-04-01	To evaluate the change from baseline in pulmonary vascular resistance (PVR), and other hemodynamic parameters, following the addition of ambrisentan to background phosphodiesterase type-5 inhibitor (PDE-5i) therapy in subjects with pulmonary arterial hypertension (PAH) who have demonstrated a sub-optimal response to PDE-5i monotherapy. The study was originally designed as a 2-arm, double-blind, randomized study in which patients received ambrisentan or placebo for 24 weeks, and then received ambrisentan blinded to dose for 24 weeks. With Protocol Amendment 2 (12 June, 2009), the study was switched to single-arm, open-label treatment, and all patients remaining in the placebo arm were switched to open-label ambrisentan treatment. Patients who enrolled after Amendment 2 all received open-label ambrisentan.
NCT00725361 ↗	A Study to Evaluate the Efficacy of an Oral Medication in the Treatment and Prevention of Digital Ulcers in Patients With Systemic Sclerosis (Scleroderma).	Completed	Stanford University	N/A	2008-06-01	This is a research study of an investigational drug called ambrisentan (Letairis) in the treatment and prevention of digital ulcers in patients with systemic sclerosis.
NCT00777920 ↗	Study of Ambrisentan in Participants With Pulmonary Hypertension	Completed	Gilead Sciences	Phase 3	2008-11-17	The primary objective of this study is to monitor the long-term safety of ambrisentan in adult participants with pulmonary hypertension. The available ambrisentan doses for this study are 2.5, 5, or 10 mg administered orally once daily. Investigators will be able to adjust ambrisentan dose as clinically indicated. A minimum of 4 weeks between dose adjustments is required. Participants receiving other therapies for pulmonary hypertension that are not contraindicated for concomitant use with ambrisentan are permitted to enroll in this study and continue to receive such therapies. Participants enrolled in this study will receive treatment with ambrisentan until such time as the investigator or participant chooses to stop ambrisentan treatment, ambrisentan becomes commercially available, or the sponsor stops the study.
NCT00840463 ↗	Safety and Efficacy Trial to Treat Diastolic Heart Failure Using Ambrisentan	Terminated	Gilead Sciences	Phase 4	2009-01-01	This is a randomized study of ambrisentan that will last 16 weeks. The study will include patients with diastolic heart failure and pulmonary hypertension. Patients will be randomized (1:1) to ambrisentan or placebo. The ambrisentan or matching placebo will be started at 2.5 mg by mouth daily and increased to 5mg and then 10mg daily, if tolerated. Patients will be seen at least monthly for 16 weeks. Adverse reactions will be reviewed and the required monthly laboratory tests (liver function testing and pregnancy testing, if applicable), will be performed. Patients will also complete an exercise test (six minute walk distance) and a quality of life survey at the baseline, week 4 and week 16 visit. An echocardiogram and a right heart catheterization and left ventricular end diastolic pressure measurement will be performed at the 16 week visit. The primary end-point is safety, and secondary end-points include the catheterization results, echocardiogram results, the walk distance and the quality of life survey. The expected completion of the study is 18 months from initiation. Ambrisentan is an FDA approved drug for PAH, but not for CHF.
NCT00840463 ↗	Safety and Efficacy Trial to Treat Diastolic Heart Failure Using Ambrisentan	Terminated	University of Texas Southwestern Medical Center	Phase 4	2009-01-01	This is a randomized study of ambrisentan that will last 16 weeks. The study will include patients with diastolic heart failure and pulmonary hypertension. Patients will be randomized (1:1) to ambrisentan or placebo. The ambrisentan or matching placebo will be started at 2.5 mg by mouth daily and increased to 5mg and then 10mg daily, if tolerated. Patients will be seen at least monthly for 16 weeks. Adverse reactions will be reviewed and the required monthly laboratory tests (liver function testing and pregnancy testing, if applicable), will be performed. Patients will also complete an exercise test (six minute walk distance) and a quality of life survey at the baseline, week 4 and week 16 visit. An echocardiogram and a right heart catheterization and left ventricular end diastolic pressure measurement will be performed at the 16 week visit. The primary end-point is safety, and secondary end-points include the catheterization results, echocardiogram results, the walk distance and the quality of life survey. The expected completion of the study is 18 months from initiation. Ambrisentan is an FDA approved drug for PAH, but not for CHF.
NCT00851929 ↗	Ambrisentan (Letairis) for Sarcoidosis Associated Pulmonary Hypertension	Completed	Gilead Sciences	Phase 2/Phase 3	2008-11-01	Hypothesis: Ambrisentan (Letairis ®) is safe and effective in treating pulmonary hypertension in patients with Sarcoidosis

Clinical Trial Conditions for LETAIRIS

Condition Name

Condition Name for LETAIRIS
Intervention	Trials
Pulmonary Hypertension	8
Pulmonary Arterial Hypertension	6
Systemic Sclerosis	2
Portopulmonary Hypertension	2

Condition MeSH

Condition MeSH for LETAIRIS
Intervention	Trials
Hypertension	19
Hypertension, Pulmonary	13
Pulmonary Arterial Hypertension	10
Familial Primary Pulmonary Hypertension	8

Clinical Trial Locations for LETAIRIS

Trials by Country

Trials by Country for LETAIRIS
Location	Trials
United States	115
Canada	9
Italy	8
Germany	7
Australia	7

Trials by US State

Trials by US State for LETAIRIS
Location	Trials
California	9
Massachusetts	9
North Carolina	7
Colorado	6
Ohio	6

Clinical Trial Progress for LETAIRIS

Clinical Trial Phase

Clinical Trial Phase for LETAIRIS
Clinical Trial Phase	Trials
Phase 4	9
Phase 3	4
Phase 2/Phase 3	1

Clinical Trial Status

Clinical Trial Status for LETAIRIS
Clinical Trial Phase	Trials
Completed	15
Terminated	6
Active, not recruiting	1

Clinical Trial Sponsors for LETAIRIS

Sponsor Name

Sponsor Name for LETAIRIS
Sponsor	Trials
Gilead Sciences	13
United Therapeutics	2
Stanford University	2

Sponsor Type

Sponsor Type for LETAIRIS
Sponsor	Trials
Other	23
Industry	19
NIH	3

Last updated: April 28, 2026

Letairis (ambrisentan): clinical-trial update, market analysis, and projections

What is Letairis and how is it positioned commercially?

Letairis is the brand name for ambrisentan, an endothelin receptor antagonist (ERA) used to treat pulmonary arterial hypertension (PAH). In practice, it is used across the PAH treatment paradigm that includes background therapy (commonly PDE5 inhibitors) and risk-stratified add-on escalation.

Commercially, the product sits in a mature PAH category where growth is driven by:

• PAH population access and diagnosis (referral flow into specialty care)
• Treatment persistence (treatment continuity and refill patterns)
• Dose optimization and guideline-concordant sequencing
• Competitive penetration by other ERAs and combination regimens

What clinical trial activity matters for Letairis now?

No trial program with ambrisentan that is required to characterize near-term label-changing trajectory can be confirmed from the information provided in this chat. A complete, accurate “clinical trials update” needs a defined set of current and recent studies (phase, design endpoints, primary completion dates, and any regulatory submissions). That set is not included here, so a complete update cannot be produced to the standard required for investment or R&D decisions.

What is the current market structure for ERA-based PAH therapy?

The PAH ERA segment has a competitive structure defined by:

• Mechanism class: endothelin receptor antagonism
• Reference drug set: macitentan (Opsumit), bosentan (Tracleer), and ambrisentan (Letairis)
• Combination practice: background vasodilator therapy with ERA add-on, based on risk profile

Letairis competes on:

• Clinical familiarity and prescriber adherence in PAH specialty centers
• Formulary inclusion and payer placement (step edits, prior authorization, and quantity limits)
• Tolerability and discontinuation rates in routine care, which shape persistence

How is Letairis likely to perform in a base-case market projection?

A defensible market projection requires at minimum a time-series of:

• historical net sales (by geography or total),
• total addressable PAH treated population,
• growth by line-of-therapy and switching,
• and competitive dynamics (launches, exclusivity cliffs, and pricing actions).

Those inputs are not present here. A complete and accurate forecast cannot be produced from the current message alone.

What KPIs should be used to forecast Letairis specifically?

Even without numeric forecasts, the following KPIs define whether Letairis outgrows or underperforms the PAH market:

1. PAH diagnosed and treated patient growth (specialty center referral and diagnosis rate)
2. Share of ERA prescriptions within PAH (mechanism-specific share)
3. Persistence and discontinuation (dose-related tolerability and switching behavior)
4. Net price and rebate trajectory (payer contracting and utilization management)
5. Combination uptake rate with background PAH therapies (guideline compliance drives mix)

These are the drivers that translate macro PAH growth into Letairis outcomes.

What are the regulatory and exclusivity considerations to model?

A full exclusivity and lifecycle model must incorporate:

• patent expiries,
• data exclusivity and any pediatric extensions,
• marketing authorization jurisdictions,
• and generic or biosimilar launch risk.

No patent or exclusivity dossier data is included in the prompt, so a structured exclusivity table and calendar view cannot be generated.

What does a decision-grade market projection framework look like?

For Letairis, a projection model should be built as a driver tree:

Letairis Revenue = Treated PAH patients × ERA usage rate × Ambrisentan share × Net revenue per patient-month

Where each factor is segmented by:

• NYHA/functional class distribution (severity mix)
• background therapy adoption (PDE5i/other)
• payer channel (commercial vs Medicaid vs Medicare vs hospital contract mix)

A decision-grade forecast also includes:

• scenario levers (share gains or losses from competitors, pricing actions, persistence shifts)
• risk calendar (exclusivity cliffs, generic entry timing, and likely price erosion magnitude)

At present, none of the parameter values needed to quantify these levers are provided.

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Key Takeaways

• Letairis (ambrisentan) is an ERA in PAH treatment and competes within a mature ERAs class where mix, persistence, and formulary dynamics determine performance.
• A true “clinical trials update” and a quantified “market analysis and projection” require a defined dataset of current trials and historical sales/exclusivity facts; those are not included in this prompt.
• The correct forecasting approach for Letairis is a driver-tree model based on PAH treated population growth, ERA utilization, ambrisentan share, net price, and persistence.

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FAQs

1) Is Letairis used alone or in combination for PAH?
It is used within guideline-based PAH treatment strategies that commonly include combination therapy, depending on risk profile and existing treatment.

2) Who are Letairis’s closest competitors in ERAs for PAH?
Within the ERA class, the key competitive set is macitentan, bosentan, and ambrisentan.

3) What drives Letairis net sales more: patient growth or market share?
In mature PAH markets, net sales are typically driven by both treated patient growth and ambrisentan share, with persistence and payer pricing often determining net realized revenue.

4) What endpoints matter most in PAH trials that affect market outcomes?
PAH programs commonly hinge on clinically meaningful outcomes (functional class, exercise capacity, hemodynamics, and clinical worsening events), and on safety/tolerability that influences persistence.

5) What is the biggest risk to an ambrisentan sales forecast?
Loss of formulary share, price erosion from contracting, or exclusivity-related generic entry timing.

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References

[1] FDA. Letairis (ambrisentan) prescribing information. (latest available version).
[2] EMA. Letairis (ambrisentan) product information. (latest available version).
[3] ClinicalTrials.gov. Ambrisentan (Letairis) search results for interventional studies.