Treprostinil Improves Walk Distance in Pulmonary Hypertension

Neil Osterweil

July 09, 2020

Patients with interstitial lung disease–associated pulmonary hypertension who were treated with inhaled treprostinil (Tyvaso) had significantly greater improvement in exercise capacity over 16 weeks, compared with patients who used a placebo inhaler, results of a phase 3 trial showed.

Among 326 patients with pulmonary hypertension (PH) associated with interstitial lung disease (ILD), those who were randomly assigned to treatment with treprostinil had a placebo-corrected median difference from baseline in 6-minute walk distance of 21 m (P = .004), reported Steven D. Nathan, MD, from Inova Fairfax Hospital in Falls Church, Va., on behalf of coinvestigators in the INCREASE study (NCT02630316).

"These results support an additional treatment avenue, and might herald a shift in the clinical management of patients with interstitial lung disease," he said in the American Thoracic Society's virtual clinical trial session.

"This was an outstanding presentation and outstanding results. I personally am very excited, because this is a field where I work," commented Martin Kolb, MD, PhD, from McMaster University, Hamilton, Ont., the facilitator for the online presentation.

The INCREASE trial compared inhaled treprostinil dose four times daily with placebo in patients with a CT scan–confirmed diagnosis of World Health Organization group 3 PH within 6 months before randomization who had evidence of diffuse parenchymal lung disease. Eligible patients could have any form of ILD or combined pulmonary fibrosis and emphysema.

Key inclusion criteria included right-heart catheterization within the previous year with documented pulmonary vascular resistance greater than 3 Wood units, pulmonary capillary wedge pressure 15 mm Hg or less, and mean pulmonary arterial pressure 25 mm Hg or higher.

Patients also had to have a 6-minute walk distance of at least 100 m and have stable disease while on an optimized dose of medications for underlying lung disease. Patients with group 3 connective tissue disease had to have baseline forced vital capacity of less than 70%.

The final study cohorts included patients with idiopathic interstitial pneumonias, chronic hypersensitivity pneumonitis, connective tissue disease, combined pulmonary fibrosis and emphysema, and occupational lung disease.

The patients were randomized to receive either inhaled treprostinil at a starting dose of 6 mcg/breath four times daily or to placebo (163 patients in each arm). All patients started the study drug at a dose of three breaths four times daily during waking hours. Dose escalations — adding 1 additional breath four times daily — were allowed every 3 days, up to a target dose of 9 breaths (54 mcg) four times daily, and a maximum of 12 breaths (72 mcg) four times daily as clinically tolerated.

A total of 130 patients assigned to treprostinil and 128 assigned to placebo completed 16 weeks of therapy and assessment.

As noted before, patients assigned to treprostinil had a placebo-corrected median difference from baseline in peak 6-minute walk distance, as measured by Hodges-Lehmann estimation, of 21 m (P = .004). An analysis of the same parameter using mixed model repeated measurement showed a placebo-corrected difference from baseline in peak 6-minute walk distance of 31.12 m (P < .001).

Secondary endpoints that were significantly better with treprostinil, compared with placebo, included improvements in N-terminal of the prohormone brain natriuretic peptide, a longer time to clinical worsening, and improvements in peak 6-minute walk distance week 12, and trough 6-minute walk distance at week 15.

Treprostinil was associated with a 39% reduction in risk of clinical worsening (P = .04). In all, 37 patients on treprostinil (22.7%) and 54 on placebo (33.1%) experienced clinical worsening.

For the exploratory endpoints of change in patient reported quality of life as measured by the St. George's Respiratory Questionnaire, or in peak distance saturation product, however, there were no significant differences between the groups.

In addition, treprostinil was associated with a 34% reduction the risk of exacerbation of underlying lung disease, compared with placebo (P = .03).

The safety profile of treprostinil was similar to that seen in other studies of the drug, and most treatment-related adverse events were mild or moderate in severity. Adverse events led to discontinuation in 10% of patients on treprostinil and 8% on placebo.

Serious adverse events were seen in 23.3% and 25.8%, respectively. The most frequently occurring adverse events of any grade included cough, headache, dyspnea, dizziness, nausea, fatigue, diarrhea, throat irritation, and oropharyngeal pain.

There was no evidence of worsened oxygenation or lung function "allaying V/Q mismatch concerns," Dr. Nathan said, and there was evidence for an improvement in forced vital capacity with treprostinil.

In the question-and-answer portion of the presentation, Dr. Kolb commented that many clinicians, particularly those who treated patients with ILD, question whether a 21-m difference in walk distance makes much of a difference in patient lives. He relayed a question from a viewer asking how Dr. Nathan and associates reconciled their primary endpoint with the finding that there was no difference in patient-reported quality of life.

"I think that the difference in the 6-minute walk test was both statistically significant and clinically meaningful," Dr. Nathan replied.

He noted that the primary endpoint used a stringent measure, and that less conservative methods of analysis showed a larger difference in benefit favoring treprostinil. He also pointed out that the original study of inhaled treprostinil added to oral therapy for pulmonary arterial hypertension showed a 20-m improvement in walk distance, and that these results were sufficient to get the inhaled formulation approved in the United States (J Am Coll Cardiol. 2010 May. doi: 10.1016/j.jacc.2010.01.027).

Regarding the failure to detect a difference in quality of life, he said that the study was only 16 weeks in length, and that the St. George's Respiratory Questionnaire was developed for evaluation of patients with chronic obstructive pulmonary disease, "perhaps not the best instrument to use in an ILD PH study."

The study was funded by United Therapeutics. Dr. Nathan disclosed advisory committee activity/consulting, research support, and speaker fees from the company. Dr. Kolb has previously disclosed financial relationships with various companies, not including United Therapeutics.

American Thoracic Society (ATS) 2020 International Conference.

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