On November 12, 2021, the FDA approved Besremi® (ropeginterferon alfa-2b-njft) injection for the treatment of adults with polycythemia vera, a rare blood disease that affects approximately 6,200 patients each year in the United States. Individuals with polycythemia vera have a mutation that causes the bone marrow to overproduce red blood cells. This increased number of circulating red blood cells causes a “thickening” of blood which impairs the ability of blood to freely flow through blood vessels. This slowed blood flow can cause a variety of symptoms including headache, fatigue, weakness, itchy skin and enlargement of the spleen. Polycythemia vera may also put patients at increased risk of blood clots and related complications such as heart attack and stroke. Common treatments for polycythemia vera include medications as well as procedures that work to reduce the number of circulating red blood cells in the body. Basemri®, an injectable drug administered every two weeks, is a new treatment option for patients that is thought to work by inhibiting the ability of bone marrow to produce red blood cells. The efficacy and safety of Basemri® was evaluated in a clinical trial which showed that 61% patients receiving Basemri® achieved a “complete hematological response,” maintaining normal levels of red and white blood cells and platelets. Once a patient has been stable on Basemri® for at least one year, they may reduce the frequency of administration to once every four weeks. Basemri® may cause side effects such as elevations in liver enzymes, reductions in white blood cells and platelets, joint pain, fatigue, itching, upper airway infection, and muscle pain, flu-like symptoms, and in some cases transient ischemic attacks (stroke-like attacks). Medications categorized as interferon products (manmade proteins that mimic those naturally produced by the body) such as Basemri® have the potential to worsen certain neurologic and autoimmune conditions, which can lead to life-threatening complications. With this, patients should be thoroughly evaluated by a rare disease specialist to determine if they are a candidate for Basemri®.