First-in-Class Drug Wins FDA Approval for Polycythemia Vera

The FDA approved first-in-class rusfertide (Mimrylo) for treating erythrocytosis in adults with polycythemia vera (PV), a rare and slow-growing hematologic malignancy.

Rusfertide mimics hepcidin, the natural hormone involved in regulating iron homeostasis and the overproduction of red blood cells, as a key goal in treating PV is to keep hematocrit levels in check to reduce the risks for life-threatening cardiovascular events such as blood clots, stroke, or heart attack.

Approval was based on positive results of VERIFY, a phase III trial that showed rusfertide can reduce the need for phlebotomy in PV patients with uncontrolled hematocrit despite standard treatments.

“Current treatments, such as phlebotomy, leave a significant gap for too many patients and can pose challenges to daily life and routines,” investigator Andrew Kuykendall, MD, of the Moffitt Cancer Center in Tampa, Florida, said in a press release from drugmaker Takeda.

“The approval of Mimrylo offers clinicians and patients a novel, first-in-class therapy that targets erythrocytosis, which drives excess red blood cell production in PV,” added Kuykendall. “The strength and consistency of the VERIFY data give me real confidence in Mimrylo’s potential to advance how we treat PV in everyday practice and to maintain hematocrit control.”

VERIFY randomized participants to standard of care plus either subcutaneously delivered rusfertide — titrated to maintain hematocrit levels below 45% — or matching placebo.

On its primary endpoint, the trial showed that twice as many patients in the rusfertide arm required no phlebotomies during weeks 20 to 32 versus the placebo group (76.9% vs 32.9%, P<0.001). The rusfertide arm also averaged significantly fewer phlebotomies over 32 weeks (0.5 vs 1.8, respectively, P<0.0001).

The most common treatment-emergent adverse events in rusfertide-treated patients included injection-site reactions (56%) and anemia (16%). Warnings and precautions in the drug’s labeling include risks for new or worsening thrombocytosis, injection-site reactions, and embryo-fetal toxicity.