Insmed said its phase 3b Encore study of Arikayce in mac lung disease met its main goal and all multiplicity-controlled secondary culture-conversion endpoints, with the clearest gains showing up in culture conversion rates and respiratory symptom scores.
At month 13, the respiratory symptom score improved by 17.77 points in the Arikayce arm versus 14.66 points in the placebo arm, a 3.11-point advantage with a p-value of 0.0299.
The culture conversion results were much larger:
- By month 6: 87.8% with Arikayce versus 57.0% with placebo, a 30.8-point difference
- By month 12: 84.7% versus 61.3%, a 23.3-point difference
- By month 13: 82.4% versus 55.6%, a 26.8-point difference
- Durable culture conversion at month 15: 76.2% versus 47.6%, a 28.6-point difference
A fatigue measure did not separate meaningfully between groups. The PROMIS fatigue T-score changed by -5.07 in the Arikayce group and -4.27 in the placebo group, a 0.81-point difference with a p-value of 0.2900.
The study enrolled 425 patients, split nearly evenly between the two arms: 213 received Arikayce plus multidrug therapy and 212 received placebo plus multidrug therapy. Insmed said 82.4% of enrolled patients were experiencing their first MAC infection, while 17.6% were on their second or third infection.
Safety data showed higher discontinuation and more respiratory adverse events in the Arikayce group. Treatment discontinuation was 14.6% with Arikayce versus 8.5% with placebo. Study completion was 90.6% versus 93.4%.
Among all patients, any treatment-emergent adverse event was reported in 98.1% of the Arikayce arm and 97.2% of the placebo arm. Severe events occurred in 15.0% versus 10.4%, and serious events in 14.1% versus 11.3%.
The most common adverse events that were higher with Arikayce were:
- Dysphonia: 58.7% versus 8.5%
- Cough: 32.9% versus 14.6%
- Fatigue: 17.4% versus 11.3%
- Dyspnea: 16.4% versus 5.7%
- Nausea: 15.5% versus 12.7%
- Headache: 12.7% versus 11.8%
Among adverse events of special interest, bronchospasm was reported in 23.0% of Arikayce patients versus 11.8% of placebo patients, and hypersensitivity pneumonitis in 2.3% versus 0%. Ototoxicity was reported in 25.8% versus 22.6%, hemoptysis in 10.3% versus 10.4%, neuromuscular disorders in 2.3% versus 2.8%, and nephrotoxicity in 0.5% versus 0%.
Insmed said it plans to file a supplemental NDA in the second half of 2026 and to submit the data to Japan’s PMDA in the same period. Following these announcements, the company's shares moved 1.35%, and are now trading at a price of $161.42. Check out the company's full 8-K submission here.
