Conference Coverage

Multicenter trial backs pirfenidone for unclassifiable interstitial lung disease


 

REPORTING FROM ERS 2019

Pirfenidone was shown to be effective for slowing decline in lung function among patients with unclassifiable interstitial lung diseases (uILD), according to results of a late breaker, placebo-controlled, multinational trial presented at the annual congress of the European Respiratory Society.

Dr. Toby M. Maher, head of the Fibrosis Research Group for the National Heart and Lung Institute, Imperial College, London Ted Bosworth/MDedge News

Dr. Toby M. Maher

For preservation of lung function as monitored with forced vital capacity (FVC), pirfenidone provided a large and highly statistically significant advantage over placebo in a phase 2 trial that randomized 253 uILD patients to 2,403 mg pirfenidone or placebo, according to Toby M. Maher, MD, head of the Fibrosis Research Group for the National Heart and Lung Institute, Imperial College, London.

At 24 weeks, FVC lung function declined by just 17.8 mL in the pirfenidone group vs. 113 mL in the placebo group (P = .002). The results, published simultaneously with Dr. Maher’s ERS presentation in The Lancet Respiratory Medicine, are particularly encouraging because there are no currently approved treatments for uILD, according to Dr. Maher.

However, the data from this study, even though it was double blind and involved 70 participating centers in 14 countries, come with an asterisk. The significant FVC advantage was documented with in-hospital measurements, but this was a secondary, not the primary, endpoint. Measurements with hand-held spirometry, which was the primary endpoint, proved to be uninterpretable due to intra-individual variability.

“We had hoped that daily home spirometry would give us more information of the patient’s trajectory over time,” said Dr. Maher, who blames himself for selecting hand-held device measurements as the primary endpoint. In the end, the variability in the home hand-held spirometry data prevented the planned statistical testing.

“There were issues with the hand-held devices we had not anticipated,” Dr. Maher reported. However, hospital-based measurement, which has long been the “regulatory standard” in ILD trials “supports the conclusion that pirfenidone was effective.”

The conclusion is also supported by other secondary outcomes and analyses. For example, the categorical declines in FVC of greater than 5% (37.0% vs. 58.7%; P = .001) and greater than 10% (14.2% vs. 27.9%; P = .011) both favored pirfenidone. There were no between-group differences in progression-free survival at 24 weeks, but events were low in both study arms over this time period.

There was evidence of functional benefit for pirfenidone relative to placebo, such as a smaller decline in the 6-minute walk test (–2 vs. –26.7 M, P = .04). Treatment favoring pirfenidone over placebo was observed across subgroups defined by age, gender, baseline lung function, and presence or absence of interstitial pneumonia with autoimmune features.

Pirfenidone was generally well tolerated with side effects similar to those reported in other studies. The rate of treatment-related discontinuation was 12.6% on pirfenidone versus 0.8% on placebo. The most frequent adverse events, all of which were more common in the pirfenidone group, were gastrointestinal complaints (47.2% vs. 25.8%), rash (10.2% vs. 7.3%), and dizziness (7.9% vs. 0.8%). Rates of photosensitivity were higher in the experimental arm (7.9% vs. 1.8%), but low relative to previous studies, potentially because of greater emphasis on sun protection, Dr. Maher reported.

About 10%-15% of patients with ILD have an unclassifiable type, he noted. Although it is possible for uILD to be a missed diagnosis of an established ILD type, Dr. Maher reported that participating centers for this study were specifically selected for their expertise in ILD. He noted that more than 45% of patients were deemed uILD on the basis of biopsy.

The ERS-invited discussant of this trial, Martin Kolb, MD, professor of respirology, McMaster University, Hamilton, Ont., called the data “strong.” He suggested the data are particularly encouraging in the context of the lack of approved therapies for uILD.

Despite the fact that benefit of pirfenidone was not established on the primary endpoint, Dr. Maher contended that this is a positive study that can be used to design future investigations. “When we use the normal standard endpoint for the study, we see a clear benefit of pirfenidone over placebo.”

Dr. Maher reported no potential conflicts of interest.

SOURCE: Maher TM et al. Lancet Respir Med. 2019 Sep 29. doi: 10.1016/S2213-2600(19)30341-8.

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