Japanese pharmaceutical company Takeda (TSE:4502) (NYSE:TAK) and US biopharmaceutical company Protagonist Therapeutics Inc (NASDAQ:PTGX) announced on Monday that the US Food and Drug Administration (FDA) has accepted the New Drug Application (NDA) for rusfertide and granted Priority Review, with a PDUFA target date in the third quarter of 2026.

Rusfertide is an investigational, first-in-class hepcidin mimetic peptide for adults with polycythemia vera (PV), a condition characterised by red blood cell overproduction that can increase the risk of thrombotic events.

The NDA is primarily based on Phase 3 VERIFY study results, in which rusfertide plus standard of care more than doubled clinical response rates, improving haematocrit control, reducing phlebotomy requirements, and alleviating fatigue and symptom burden. Long-term safety and efficacy were also supported by four-year data from the Phase 2 REVIVE and THRIVE studies. Rusfertide was generally well-tolerated, with most adverse events mild to moderate, including injection site reactions, anaemia, and fatigue.

The drug has previously received Breakthrough Therapy, Orphan Drug, and Fast Track designations from the FDA.

Protagonist discovered rusfertide and led its development through Phase 3 studies under a 2024 global licence and collaboration agreement, with Takeda responsible for implementing the regulatory strategy for the US NDA filing and for leading any future global regulatory filings. Protagonist holds an option to co-commercialise in the US through a 50/50 profit and loss arrangement.