Protagonist Therapeutics has announced that the US Food and Drug Administration (FDA) has granted Breakthrough Therapy designation to rusfertide for the treatment of erythrocytosis in patients with polycythemia vera (PV).

PV is a rare blood cancer in which the bone marrow produces too many red blood cells, leading to erythrocytosis (raised red cell levels). The condition increases the risk of blood clots, stroke, and other complications, and is typically managed through phlebotomy and medication to control hematocrit levels.

The hepcidin-mimetic peptide candidate had previously received Orphan Drug and Fast Track designations. Breakthrough Therapy designation is intended to expedite development of treatments that may show substantial improvement over existing therapies.

The FDA decision was supported by 32-week data from the Phase 3 VERIFY trial, which were presented during the plenary session at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting.

“We are very pleased with the FDA’s decision to grant Breakthrough Therapy designation to rusfertide, which underscores its potential to demonstrate substantial improvement over available PV therapies,” said Dinesh Patel, president and chief executive officer of Protagonist Therapeutics. “We remain on track for NDA submission of rusfertide in polycythemia vera by the end of this year.”

“In the VERIFY Phase 3 trial, rusfertide demonstrated positive results across all primary and key secondary endpoints including hematocrit control, decreased phlebotomy dependence, and patient reported outcomes including improvement in fatigue,” added Arturo Molina, chief medical officer at Protagonist.

Rusfertide is being co-developed with Takeda Pharmaceuticals under a worldwide collaboration and license agreement signed in 2024, with Protagonist leading development through NDA submission.