Insmed Incorporated (NASDAQ:INSM) shares jumped almost 8% in early trade on Monday after the company reported positive topline results from a Phase 3b study evaluating its lung disease therapy ARIKAYCE.
The ENCORE trial assessed ARIKAYCE (amikacin liposome inhalation suspension) in combination with standard multidrug therapy versus placebo plus multidrug therapy in patients with newly diagnosed Mycobacterium avium complex (MAC) lung infection who had not previously received antibiotics.
The study met its primary endpoint, showing a statistically significant improvement in respiratory symptom scores at Month 13 compared with the control group. Patients receiving ARIKAYCE saw a 17.77-point improvement from baseline, compared with 14.66 points in the placebo arm, a difference of 3.11 points.
All multiplicity-controlled secondary endpoints were also met, including culture conversion rates. By Month 6, 87.8% of patients in the ARIKAYCE group achieved culture conversion, compared with 57% in the placebo group.
The treatment benefit persisted through later timepoints, with conversion rates of 82.4% versus 55.6% at Month 13 and durable conversion at Month 15 of 76.2% versus 47.6%, all with p-values below 0.0001.
Changes in fatigue scores, another secondary measure, did not reach statistical significance.
These results are an exciting win for patients living with MAC lung disease and a powerful validation of ARIKAYCE's ability to deliver real clinical benefit as part of a multidrug treatment regimen," Insmed’s chief medical officer Dr Martina Flammer said.
"We are energized by the potential for patients with a new MAC infection to see benefit with ARIKAYCE earlier in their treatment journey and look forward to exploring the expansion of the ARIKAYCE indication in the US and Japan, with the ultimate goal of improving outcomes for an even greater number of patients fighting this difficult disease."
Insmed said it intends to file a supplemental new drug application with the US Food and Drug Administration (FDA) in the second half of 2026 to support potential label expansion and convert its existing indication to traditional approval. The company also plans to submit the data to Japan’s Pharmaceuticals and Medical Devices Agency over the same period.
Jefferies described the results as “a nice, clean win for Arikayce,” noting the combination of a statistically significant patient-reported outcome and strong culture conversion data.
The firm highlighted the 3.11-point improvement in respiratory symptom score and Month 13 culture conversion rates of 82% versus 56% as key takeaways.
They believe the readout helps address a key investor concern around the PRO endpoint, which had been viewed as a potential risk. Some investors had worried that the control arm could narrow the gap by Month 13 or that the endpoint might be underpowered, Jefferies noted, but the statistically significant result may alleviate those concerns.
The firm also pointed to the data as supportive of a broader market opportunity, with the study expected to expand ARIKAYCE’s use beyond its current refractory setting and support conversion to full approval in the US.
Safety findings were broadly consistent with prior data, with no new signals identified. Discontinuation rates were 18.3% in the ARIKAYCE arm versus 11.8% in the comparator arm, which Jefferies noted was lower than in the earlier CONVERT study. Common adverse events included dysphonia and cough.
Looking ahead, Jefferies said the results could act as a “clearing event” for the stock, allowing investors to focus more on Insmed’s pipeline, particularly its Brinsupri program, its FDA approved treatment for non-cystic fibrosis bronchiectasis.