FDA Approves a Drug That Cut the Need for Blood Draws in a Rare Blood Disorder

The Food and Drug Administration approved Mimrylo (rusfertide) on Aug. 28 for adults with polycythemia vera, a rare blood disorder in which the body produces too many red blood cells. The approval was granted to Takeda Pharmaceuticals America, the agency said.

The FDA describes Mimrylo as the first approved treatment for polycythemia vera that mimics hepcidin, a hormone that regulates iron in the body. By limiting the iron available for making new red blood cells, the agency said, the drug holds their production down.

A goal of treatment is keeping hematocrit, the share of blood made up of red cells, below 45%, which the FDA said reduces cardiovascular risk. That often requires phlebotomy, drawing blood from a vein to lower the red cell count. Some patients need frequent draws even while on therapy, according to the agency.

The approval rests on VERIFY, a multicenter, randomized, double-blind, placebo-controlled phase 3 trial in 293 adults who required frequent phlebotomies despite ongoing standard-of-care therapy, the FDA said. Patients were randomized 1-to-1 to Mimrylo or placebo over 32 weeks. Dosing started at 19 mg injected under the skin once weekly and was adjusted to hold hematocrit below 45%.

The trial measured the share of patients who did not meet the criteria for phlebotomy between weeks 20 and 32. The FDA reported 76.9% of patients on Mimrylo required no phlebotomies over the 32-week period, against 32.9% on placebo. The most common adverse reactions were injection-site reactions and anemia.

Tanya Wroblewski, director of the Division of Nonmalignant Hematology in the FDA's Center for Drug Evaluation and Research, said in the announcement that the approval "offers a new, first-in-class option that has the potential to meaningfully reduce patient burden."

Mimrylo received priority review, the FDA said.