On 17 November, the U.S. Food and Drug Administration approved Besremi (ropeginterferon alfa-2b-njft) injection to treat adults with polycythemia vera, a blood disease that causes the overproduction of red blood cells. The excess cells thicken the blood, slowing blood flow and increasing the chance of blood clots.

“Over 7,000 rare diseases affect more than 30 million people in the United States. Polycythemia vera affects approximately 6,200 Americans each year,” said Ann Farrell, MD, director of the Division of Non-Malignant Hematology in the FDA’s Center for Drug Evaluation and Research. “This action highlights the FDA’s commitment to helping make new treatments available to patients with rare diseases.”

Besremi is the first FDA-approved medication for polycythemia vera that patients can take regardless of their treatment history, and the first interferon therapy specifically approved for polycythemia vera.

Treatment for polycythemia vera includes phlebotomies (a procedure that removes excess blood cells though a needle in a vein) as well as medicines to reduce the number of blood cells; Besremi is one of these medicines.

Besremi is believed to work by attaching to certain receptors in the body, setting off a chain reaction that makes the bone marrow reduce blood cell production. Besremi is a long-acting drug that patients take by injection under the skin once every two weeks. If Besremi can reduce excess blood cells and maintain normal levels for at least one year, then dosing frequency may be reduced to once every four weeks.

The effectiveness and safety of Besremi were evaluated in a multicenter, single-arm trial that lasted 7.5 years. In this trial, 51 adults with polycythemia vera received Besremi for an average of about five years. Besremi’s effectiveness was assessed by looking at how many patients achieved complete hematological response, which meant that patients had a red blood cell volume of less than 45% without a recent phlebotomy, normal white cell counts and platelet counts, a normal spleen size, and no blood clots. Overall, 61% of patients had a complete hematological response.

Besremi can cause liver enzyme elevations, low levels of white blood cells, low levels of platelets, joint pain, fatigue, itching, upper airway infection, muscle pain and flu-like illness. Side effects may also include urinary tract infection, depression and transient ischemic attacks (stroke-like attacks).

Interferon alfa products like Besremi may cause or worsen neuropsychiatric, autoimmune, ischemic (not enough blood flow to a part of the body) and infectious diseases, which could lead to life-threatening or fatal complications. Patients who must not take Besremi include those who are allergic to the drug, those with a severe psychiatric disorder or a history of a severe psychiatric disorder, immunosuppressed transplant recipients, certain patients with autoimmune disease or a history of autoimmune disease, and patients with liver disease.

People who could be pregnant should be tested for pregnancy before using Besremi due to the risk of fetal harm. Besremi received orphan drug designation for this indication. Orphan drug designation provides incentives to assist and encourage drug development for rare diseases. The FDA granted the approval of Besremi to PharmaEssentia Corporation.