With what Insmed calls an "outstanding" phase 2 win for its treprostinil palmitil inhalation powder (TPIP) in patients with pulmonary arterial hypertension (PAH), the company is racing to phase 3 as its share price skyrockets.
The company’s TPIP is a prodrug of United Therapeutics’ treprostinil (Tyvaso). A prodrug is an inactive compound that becomes active once metabolized in the body. Insmed’s candidate is designed to be administered in a capsule-based inhalation device, according to the company.
A 102-patient phase 2b study of the once-daily dry powder met its primary and secondary goals, Insmed said Monday. The drug showed a 35% placebo-adjusted reduction in pulmonary vascular resistance (PVR) from baseline and a 35.5-meter improvement in a six-minute walking distance.
The two measures are key to determining the benefits of a drug meant to treat PAH, a progressive rare disease that causes high blood pressure in the pulmonary arteries as blood vessels in the lungs narrow or become obstructed. Shortness of breath and fatigue are some of the most common symptoms of the disease, which can be debilitating and often fatal.
The results exceeded expectations. Insmed has suggested that a 20% PVR improvement and a 15-to-20-meter increase in the walking test could be seen as a clear win, which matches what experts believe could trigger a switch from Tyvaso to TPIP, according to Jefferies analyst Kelly Shi, Ph.D., in a Sunday note previewing the phase 2b readout.
With that, Insmed is set to “immediately engage” with the FDA on a phase 3 trial design and plans to initiate a phase 3 study in PAH patients in early 2026 and another in patients with pulmonary hypertension associated with interstitial lung disease (PH-ILD) before the end of 2025.
"The statistically significant and clinically meaningful results shown with TPIP in pulmonary arterial hypertension mark a potential breakthrough for patients and the future of prostanoid therapy," Insmed’s Chief Product Strategy Officer Gene Sullivan, M.D., said in the company’s release. “These unprecedented Phase 2b results unequivocally demonstrate TPIP's potential to be a highly effective and well-tolerated once-daily prostanoid therapy for the treatment of PAH across disease severities and background treatment regimens.”
With the data drop, Insmed’s shares rose more than 27% on Tuesday morning to around $89 compared to Monday’s $70 closing price.
If Insmed’s PAH and PH-ILD candidate reaches the market, United could have another rival on its hands. The Tyvaso maker, which also makes a dry powder inhalation version called Tyvaso DPI, tried for years to block Liquidia’s rivaling PAH and PH-ILD treprostinil inhalation powder from reaching the market. After suing both Liquidia and the FDA for its review of the Liquidia drug, United’s broad exclusivity on dry powder treprostinil ran out in May, allowing Liquidia’s Yutrepia to win its long-awaited approval.
United’s Tyvaso DPI hit $1 billion in 2024 sales after crossing the FDA finish line in 2022 following several regulatory hurdles. The drug marked the first inhaled therapy for PAH and PH-ILD, with 2009-approved Tyvaso being the only PH-ILD therapy when it gained its second indication in 2021.
Insmed, meanwhile, markets Arikayce, an inhaled antibiotic that treats a specific subset of patients with Mycobacterium avium complex lung disease in combination with other drugs. The med brought in $363 million in 2024.