A Mid-Stage Result in a Disease with Almost No Options
An experimental inhaled drug reduced a key measure of strain on the heart and lungs by more than half in patients with a condition that currently has a single approved treatment.
Roivant and its subsidiary Pulmovant reported on September 8 that the Phase 2 PHocus trial of mosliciguat met its primary endpoint in pulmonary hypertension associated with interstitial lung disease. The results were presented at the European Respiratory Society International Congress in Barcelona by Professor Marc Humbert of Université Paris-Saclay, who directs the French national reference center for pulmonary hypertension.
The trial enrolled 135 patients across 87 sites in 20 countries. At week 16, patients taking mosliciguat showed a placebo-adjusted reduction in pulmonary vascular resistance of 56.3 percent, according to Pulmovant's release on the results.
That measure describes how hard the right side of the heart must work to push blood through the lungs. When scarred lung tissue narrows and stiffens those vessels, resistance climbs, and the heart eventually fails under the load.
Walking Distance Is the Number Patients Feel
Vascular resistance is measured with a catheter threaded into the heart. Patients do not experience it directly. What they experience is breathlessness, and the trial measured that too.
At week 16, patients on mosliciguat walked a placebo-adjusted 35.2 meters farther in a standard six-minute walk test. A blood marker of cardiac strain called NT-proBNP showed a placebo-adjusted reduction of 53.2 percent, or 357.7 picograms per milliliter.
A prespecified exploratory analysis at week 24 showed a larger walking improvement of 52.7 meters and a 75.9 percent reduction in the cardiac strain marker.
The word exploratory matters and should not be skipped. The week 24 walking figure is the more impressive number and the one most likely to appear in coverage, but it comes from an analysis designed to generate rather than confirm findings, and its p-values are nominal. The confirmed primary and secondary results are the week 16 figures. Both are worth reporting; they carry different evidentiary weight.
For context, roughly 30 meters is often treated as the smallest change in six-minute walk distance that patients notice in daily function, though that threshold varies by population and remains debated. The week 16 result sits modestly above it.
The Reason This Condition Has So Little Available
Interstitial lung disease scars lung tissue. In a subset of patients, that scarring damages the pulmonary blood vessels, producing pulmonary hypertension on top of the underlying lung disease. Up to 200,000 people across the United States and Europe live with this combination, and the company describes treatment options as limited or absent for most of them.
Only one drug, the inhaled prostacyclin Tyvaso, is specifically approved for this condition, following an expanded indication in 2021. Drugs that work well in other forms of pulmonary hypertension have historically performed poorly here, because widening blood vessels throughout the lung can send blood to scarred regions that cannot oxygenate it, sometimes worsening oxygen levels.
Mosliciguat is inhaled once daily rather than taken orally, which is intended to concentrate its effect in better-ventilated parts of the lung. It belongs to a class called soluble guanylate cyclase activators, which the company says work independently of the conditions that limit a related class of drugs. Cough, a common reason patients stop inhaled prostacyclins, was reported in 12.1 percent of patients on mosliciguat and 18.2 percent on placebo.
Roivant acquired the compound from Bayer in a 2024 deal worth $14 million upfront and up to $294 million in milestones. Roivant's president and chief investment officer, Dr. Mayukh Sukhatme, called the result "the largest PVR reported in any controlled pulmonary hypertension trial." That characterization comes from the company and has not been independently verified.
The company also disclosed that a Phase 3 trial called PHrontier has already begun enrolling and is designed to include roughly 375 patients worldwide.
Between a Trial Result and a Prescription
Nothing here is available to patients outside a clinical trial. Mosliciguat is not approved by the FDA or any other regulator, and a positive Phase 2 result is a reason to run a Phase 3 trial rather than evidence that a treatment works.
The limitations deserve to be stated together. This was a mid-stage trial of 135 patients. The company has released results through a press announcement and a conference presentation, and the full data have not yet appeared in a peer-reviewed journal where independent reviewers can examine the methods, as reflected in coverage of the company's announcement. No survival benefit has been demonstrated, and none was measured.
For patients and caregivers living with this diagnosis, the reasonable step is a conversation rather than a decision. Patients can ask a pulmonologist whether they have been evaluated for pulmonary hypertension at all, since it is frequently underdiagnosed in interstitial lung disease and often requires a right heart catheterization to confirm. They can ask whether a referral to a pulmonary hypertension center is appropriate, and whether they might qualify for the Phase 3 trial.
Nobody should stop or alter an existing therapy based on trial results for an unapproved drug. Worsening breathlessness, new swelling in the legs, fainting, or chest pain warrant prompt medical evaluation regardless of what any pipeline drug may eventually offer.
Access questions are also unresolved. Specialized pulmonary hypertension care is concentrated in academic medical centers, which means patients in rural areas often travel considerable distances for the diagnostic testing that would establish eligibility for any new treatment. Existing inhaled therapies for this condition are expensive and typically require prior authorization, and there is no reason to expect a different pattern if this drug is eventually approved.
MedicalDaily has reported on other lung-directed drug candidates in development, including an AI-designed lung drug measured against aging clocks in a small fibrosis trial. The next milestone for mosliciguat is Phase 3 enrollment and eventual results, which will take years rather than months.
Key Questions Answered
What condition does this drug target? Pulmonary hypertension associated with interstitial lung disease, in which lung scarring damages blood vessels and forces the right side of the heart to work harder.
What did the trial find? In 135 patients, mosliciguat produced a placebo-adjusted 56.3 percent reduction in pulmonary vascular resistance at week 16, along with a 35.2-meter improvement in six-minute walk distance.
What about the 52.7 meter walking figure? That comes from a prespecified exploratory analysis at week 24. Exploratory results are hypothesis-generating and carry less weight than the confirmed week 16 endpoints.
Is the drug available? No. It is not approved anywhere and is available only through clinical trials. A Phase 3 study is now enrolling.
How many people have this condition? Up to 200,000 across the United States and Europe, according to the company, with limited or no approved treatment options for most.
What are the main limitations? A mid-stage trial of 135 patients, results released by the developer and not yet peer-reviewed, and no measured survival benefit.
What should patients do now? Ask a pulmonologist whether pulmonary hypertension has been evaluated, whether a referral to a specialized center is appropriate, and whether trial participation is an option. Do not change existing therapy.
