The US Food and Drug Administration (FDA) has approved the first biosimilar erythropoiesis-stimulating agent. The reference product is epoetin alfa (Epogen/Procrit, Amgen). The new biosimilar is epoetin alfa-epbx, marketed as Retacrit and manufactured by Hospira/Pfizer.
The biosimilar has been approved for the following indications: the treatment of anemia caused by chronic kidney disease, chemotherapy, or use of zidovudine (multiple brands) in patients with HIV infection; and use in the pre- and postoperative setting to reduce the need for red blood cell transfusions due to blood loss.
Biosimilars contain an active drug substance that is derived from or composed of a living organism that is highly similar to an existing FDA-approved biologic (the “reference product”). Alhough there may be minor differences between the biosimilar and the reference product in clinically inactive components, there must be no clinically meaningful differences between the biosimilar and the reference product with respect to quality, safety, or efficacy.
Importantly, as with generic drugs, biosimilars provide more options and are generally less expensive than the patented agent.
“Retacrit may provide patients and their physicians with increased access to a high-quality, lower-cost alternative treatment option for anemia and the reduction of allogeneic red blood cell transfusions in certain patients,” said Berk Gurdogan, US institutions president, Pfizer Essential Health, in a statement.
According to Pfizer, Retacrit is expected to be available in the United States at a significant discount as compared to the current wholesaler acquisition cost (WAC) of Epogen and Procrit. WAC is not inclusive of discounts that may be made to payers, providers, distributors, and other purchasing organizations.
Comparison Study Meet Endpoints
The FDA based its approval on an extensive review of evidence that included structural and functional characterization, animal study data, human pharmacokinetic and pharmacodynamic data, clinical immunogenicity data, and other clinical safety and effectiveness data.
Last year, the FDA’s Oncologic Drugs Advisory Committee voted 14-1 in favor of epoetin alfa-epbx on the basis of an extensive review of the data. Part of this review included two multicenter, double-blind, randomized, parallel-arm, active control studies that compared the biosimilar with the reference product. Both studies (EPOE-10-01 and EPOE-10-13) enrolled patients with chronic kidney disease. Such patients were considered the most sensitive population in which to evaluate clinically meaningful differences between the two agents.
Both studies met their coprimary endpoints for efficacy by demonstrating equivalence between the biosimilar and Epogen, the reference product, when administered either subcutaneously or intravenously, by maintaining mean weekly hemoglobin (Hb) levels at mean weekly dose administered to maintain Hb within the target range of 9.0 to11.0 g/dL. With respect to immunogenicity, the studies showed similar rates and titers of antidrug antibodies for both drugs.
“It is important for patients to have access to safe, effective, and affordable biological products, and we are committed to facilitating the development and approval of biosimilar and interchangeable products,” said Leah Christl, PhD, director of the therapeutic biologics and biosimilars staff in the FDA’s Center for Drug Evaluation and Research, in a statement. “Biosimilars can provide greater access to treatment options for patients, increasing competition and potentially lowering costs.”
The most common adverse events reported in clinical studies of the reference product include high blood pressure, joint pain, muscle spasm, fever, dizziness, medical device malfunction, blood vessel blockage, respiratory infection, cough, rash, injection site irritation, nausea, vomiting, muscle pain, inflammation of the mouth and lips, weight decrease, reduction in white blood cells, bone pain, high blood sugar, insomnia, headache, depression, difficulty swallowing, low blood potassium levels, blood clots, itching, headache, injection site pain, and chills.
As with Epogen/Procrit, Retacrit contains a boxed warning to alert healthcare professionals and patients about increased risks for death, heart problems, stroke, and tumor growth or recurrence. There are additional warnings about high blood pressure; seizures; a condition in which the bone marrow stops making red blood cells, thus causing anemia; serious allergic reactions; and severe skin reactions.