Insmed’s inhalable candidate showed “impressive” long-term efficacy in pulmonary arterial hypertension, according to analysts at Guggenheim Partners, with functional and biomarker improvements through one year of follow-up.
Insmed’s investigational therapy sustained functional and biomarker improvements through 12 months in an open-label extension study of patients with pulmonary arterial hypertension.
These benefits “strengthen the case” for Insmed’s drug candidate, called treprostinil palmitil inhalation powder (TPIP), “as the best-in-class inhaled prostanoid,” analysts at Guggenheim Partners told investors in a Thursday note. The firm projects peak TPIP sales to top $6 billion across several planned indications, including pulmonary arterial hypertension (PAH).
The extension study includes more than 90 patients with PAH who were already on daily TPIP from lead-in studies, as well as those who were transitioning to the inhaled therapy from placebo. The study was designed to follow participants through 24 months.
Twelve-month data presented on Thursday demonstrated functional improvements as measured by the 6-minute walk distance (6MWD). Those who maintained ongoing TPIP treatment saw a 55.7-meter increase in 6MWD, while distance grew by 54.1 meters in those who crossed over from placebo.
NT-proBNP, a biomarker indicative of heart strain, dropped by roughly 60% in both groups, Insmed said.
Guggenheim called these findings “impressive,” adding that “we come away from this data release with incrementally higher confidence in the clinical profile of this product.” The firm nevertheless flagged some outstanding concerns, including the extension trial’s small sample size and the fact that “we are still multiple years away from any Phase 3 readout for TPIP.”
Another concern is what Truist Securities flagged as an “efficacy ceiling” associated with TPIP. “A key potential differentiator of TPIP is its ability to be titrated beyond the dosing limits of currently available inhaled prostacyclins,” the analysts said in a Thursday note. However, only around 21% of patients in the current study went above 640 µg, with just seven participants reaching the maximum allowable dose of 1,280 µg, according to Truist.
“It is unclear to us why physicians would not continue escalating in well-tolerating patients if meaningful incremental benefit existed,” the firm continued. “As such, the data leave open the question of whether TPIP reaches an efficacy ceiling around current dose levels” or if going beyond 640 µg still yields meaningful clinical benefit, Truist wrote.
Insmed has recently started the Phase 3 PALM-PAH study to assess once-daily TPIP in PAH patients over 24 weeks, the biotech said on Thursday, though it did not provide a specific timeline for a topline readout.
The TPIP data comes after Insmed in April axed the hidradenitis suppurative program for its recently approved DPP1 inhibitor Brinsupri following disappointing mid-stage data. Brinsupri was approved in August 2025 for non-cystic fibrosis bronchiectasis. In the first quarter, the drug made $207.9 million—an “impressive” figure that indicates the launch is “going very well,” Guggenheim wrote in a May 7 note.
