Burlington – October 29, 2026 -- The U.S. Food and Drug Administration has approved an expanded indication for Instylla's Embrace Hydrogel Embolic System (HES), covering embolization of peripheral arterial bleeds in vessels of 6 mm or less. Embrace HES is now the first and only liquid embolic approved for both peripheral arterial bleeds and hypervascular tumors, according to the privately held company. The product is commercially available in the U.S.
HALT trial met both primary endpoints in 130 patients
The approval rests on the HALT study, a prospective, multicenter, single-arm trial that enrolled 130 patients with peripheral arterial bleeds at 22 U.S. sites. Embrace HES delivered 100% freedom from major adverse events and 90.0% clinical success, defined as no rebleeding from the target lesion, through 30 days. Both were prespecified primary endpoints.
Second indication follows August 2025 tumor approval
The bleed indication follows Instylla's initial premarket approval (PMA) in August 2025 for hypervascular tumor embolization in peripheral arteries of 5 mm or less. CEO Sean Boyle said the company is "building a transformative platform for the many vascular conditions still ahead."
Hydrogel design targets limits of conventional embolics
Hemorrhage is the leading cause of potentially preventable death after trauma. Transcatheter arterial embolization is a mainstay of treatment, with reported success rates of 81% to 100% in unstable pelvic fractures. Coils, however, depend on the patient's own clotting and can be less effective in coagulopathy.
Embrace HES is a water-based polyethylene glycol hydrogel that forms in the vessel and is coagulation independent. It is non-adhesive, which eliminates the possibility of catheter entrapment. It contains no DMSO or components that obscure CT or MRI. The hydrogel casts out the vasculature to create rapid, sustained occlusion, then liquifies through hydrolysis over approximately 11 months.
Investigators cite distal and proximal control with preserved access
Suvranu Ganguli, Chief of Interventional Radiology at Boston Medical Center and HALT principal investigator, said a single agent can achieve either distal or proximal embolization. He added that the design preserves microcatheter access after embolization, unlike many currently available liquid embolics.
Susie Park of Harbor-UCLA Medical Center, a HALT investigator, said the design helps minimize non-target embolization and allows operators to adjust embolic placement.