The US Food and Drug Administration (FDA) has approved Besremi (ropeginterferon alfa-2b-njft) injection for the treatment of adults with essential thrombocythemia.

The recommended starting dosage of Besremi is 250 mcg by subcutaneous (under the skin) injection. It should be increased to 350 mcg at 2 weeks and then to the maintenance dosage of 500 mcg at 4 weeks. The maintenance dose should be given every 2 weeks unless a dose modification is required due to tolerability.

Essential thrombocythemia is a rare blood disorder that causes the bone marrow to make too many platelets, which can increase the risk for blood clots and bleeding when the platelet count is very high. Platelets are small cell fragments in blood that help form clots to stop or prevent bleeding.

The effectiveness of Besremi was evaluated in the SURPASS ET study, an open-label, multicenter, randomised study that compared Besremi to anagrelide for the treatment of essential thrombocythemia. The study enrolled 174 adults with essential thrombocythemia who had an inadequate response or intolerance to hydroxyurea; 91 patients received Besremi and 83 patients received anagrelide (another medicine approved for treating essential thrombocythemia).

Besremi was administered subcutaneously every 2 weeks at the starting dose of 250 mcg (week 0), then 350 mcg (week 2), and 500 mcg (week 4), and then remained fixed at 500 mcg every 2 weeks for the remainder of the study. Anagrelide was administered orally according to its product label and treatment practices. Patients in both arms also received low-dose aspirin (75 to 150 mg/day per local practice), unless contraindicated.

Efficacy was evaluated in the SURPASS ET study by assessing durable Modified European Leukemia Net (ELN) response rates at months 9 and 12. Patients were considered responders if they met all of the following criteria: blood count remission, improvement or non-progression of splenomegaly (enlarged spleen), and absence of bleeding or clotting events. Treatment with Besremi demonstrated a higher response rate of 37.4 percent compared to a response rate of 3.6 percent for the anagrelide treatment group at both months 9 and 12.

The most common adverse reactions included transaminase elevations (high levels of liver enzymes), anemia, fever, bacterial infection, pruritus (itching), and weight loss.