On top of the newly approved lung disorder pill Brinsupri, which Insmed expects will achieve blockbuster sales this year, the New Jersey company has revealed results from a trial of its older lung disease treatment, Arikayce, which could pave the way for a significant label expansion.
The phase 3b Encore study tested inhaled Arikayce plus the antibiotic combination of azithromycin and ethambutol versus placebo added to the antibiotic duo in newly diagnosed patients with Mycobacterium avium complex (MAC) lung infection.
The trial met its primary and multiplicity-controlled secondary culture conversion endpoints, the company said in a March 23 release.
The Arikayce regimen showed both statistically significant and clinically meaningful improvements in respiratory symptom score (RSS) and culture conversion rates.
With the results, Insmed plans to file for a label expansion in the second half of this year, which would allow its use in newly diagnosed patients who have not received antibiotics. Arikayce was initially approved by the FDA for refractory disease back in 2018.
An expansion would increase Arikayce’s addressable patient population from 30,000 to a major 200,000, Insmed CEO William Lewis said in a Monday conference call. He added that the company expects the results—which fulfill the FDA’s post-marketing requirement—will also convince the agency to convert Arikayce’s nod from accelerated to full.
“This is a particularly difficult disease to treat,” Lewis said. “Every other company that has come along trying to bring forward a medicine has failed to be able to produce clinical trial results in a double-blind study that are adequate for approval. I think that just highlights the desperate need for this patient population.”
The results triggered a 7% increase in Insmed’s share price on Monday morning.
As for the primary endpoint, patients in the Arikayce arm after 13 months gained an average of 17.8 points from baseline on the RSS scale, compared to a 14.7 average increase in the placebo group.
The key secondary endpoints were sputum culture conversion rates measured at a variety of timeframes. After 13 months, a statistically significant proportion of Arikayce patients achieved culture conversion, 82% versus 56%.
After 15 months, a statistically significant proportion of Arikayce patients achieved durable culture conversion, 76% compared to 48% in the control arm. Similar culture conversion rates were evident (PDF) at every measured time period from month one to month 15.
Lewis said the results are “striking” evidence of Arikayce's ability to improve outcomes for MAC patients earlier in their treatment journey. He compared results from Insmed’s previous trial of the treatment, which showed culture conversion in roughly a third of patients.
“What is important to note here is that the data from this study is unequivocally positive from the perspective of physicians who are seeking to eradicate evidence of the infection in their patient populations,” Lewis said. “There is a powerful motivation in the data to move to treat these patients earlier and the dropout rate going down suggests that the treatment burden for the patient is reduced.”
The active component of antibiotic Arikayce is amikacin, a two-decade-old antibiotic that was originally administered intravenously until Insmed created its inhaled formulation to treat MAC, which is a potentially fatal condition and has been diagnosed in more patients in Japan than in the U.S.
In 2025, sales of Arikayce were up 19%, reaching $434 million. Lewis said the company would reveal later how the potential expansion would impact its peak sales.