Biosimilars are copies of FDA-approved biologic drugs (those generally derived from a living organism) that cannot be identical to the reference drug but demonstrate a high similarity to it. As patents on the reference drugs expire, biosimilars are being developed to increase competition in the marketplace to reduce costs and improve patient access to therapy. Although the US Food and Drug Administration (FDA) has no regulatory power over drug prices, it recently announced efforts to streamline the biosimilar approval process to facilitate access to therapies and curb the associated skyrocketing costs.
Several biosimilars have been approved by the agency in recent years, and earlier this year they were joined by 2 more: the approval in May of epoetin alfa-epbx (Retacrit; Hospira, a Pfizer company) for all indications of the reference product (epoetin alfa; Epogen/Procrit, Amgen), including the treatment of anemia caused by myelosuppressive chemotherapy, when there is a minimum of 2 additional months of planned chemotherapy;1 and the June approval of pegfilgrastim-jmdb (Fulphila, Mylan and Biocon) for the treatment of patients undergoing myelosuppressive chemotherapy to help reduce the chance of infection as suggested by febrile neutropenia (fever, often with other signs of infection, associated with an abnormally low number of infection-fighting white blood cells).2 The reference product for pegfilgrastim-jmdb is pegfilgrastim (Neulasta, Amgen).
The approval of both biosimilars was based on a review of a body of evidence that included structural and functional characterization, animal study data, human pharmacokinetic (PK) and pharmacodynamic (PD) data, clinical immunogenicity data, and other clinical safety and efficacy data. This evidence established that the biosimilars were highly similar to the already FDA-approved reference products, with no clinically relevant differences.
Biocon and Mylan-GmBH, which jointly developed pegfilgrastim-jmdb, originally filed for approval in 2017; and Hospira Inc, a Pfizer company that developed epoetin alfa-epbx, filed for the first time in 2015. They subsequently received complete response letters from the FDA, twice in the case of the epoetin alfa biosimilar, rejecting their approval. For pegfilgrastim-jmdb, the complete response letter was related to a pending update of the Biologic License Application as the result of requalification activities taken because of modifications at their manufacturing plant. For epoetin alfa-epbx, the FDA expressed concerns relating to a manufacturing facility. The companies addressed the concerns in the complete response letters and submitted corrective and preventive action plans.3,4
The results from a phase 3, multicenter, randomized, double-blind parallel-group trial of pegfilgrastim-jmdb compared with European Union-approved pegfilgrastim were published in 2016. Chemotherapy and radiation-naïve patients with newly diagnosed breast cancer (n = 194) received the biosimilar or reference product every 3 weeks for 6 cycles. The primary endpoint was duration of severe neutropenia in cycle 1, defined as days with absolute neutrophil count <0.5 x 109/L. The mean standard deviation was 1.2 [0.93] in the pegfilgrastim-jmdb arm and 1.2 [1.10] in the EU-pegfilgrastim arm, and the 95% confidence interval of least squares means differences was within the -1 day, +1 day range, indicating equivalency.5
A characterization and similarity assessment of pegfilgrastim-jmdb compared with US- and EU-approved pegfilgrastim was presented at the 2018 Annual Meeting of the American Society of Clinical Oncology. G-CSF receptor (G-CSFR) binding was assessed by surface plasmon resonance and potency was measured by in vitro stimulated proliferation in a mouse myelogenous leukemia cell line. In vivo rodent studies were also performed and included a PD study with a single dose of up to 3 mg/kg.6
There was high similarity in the structure, molecular mass, impurities and functional activity of the biosimilar and reference products, as well as similar G-CSFR binding and equivalent relative potency. Neutrophil and leukocyte counts were increased to a similar degree, and toxicology and drug kinetics were also comparable.
The recommended dose of pegfilgrastim-jmdb is a 6 mg/0.6 ml injection in a single-dose prefilled syringe for manual use only, administered subcutaneously once per chemotherapy cycle. The prescribing information also has dosing guidelines for administration in pediatric patients who weigh less than 45 kg. Pegfilgrastim-jmdb should not be administered between 14 days before and 24 hours after administration of chemotherapy.
The prescribing information details warnings and precautions relating to splenic rupture, acute respiratory distress syndrome (ARDS), serious allergic reactions, potential for severe/fatal sickle cell crises in patients with sickle cell disorders, glomerulonephritis, leukocytosis, capillary leak syndrome, and the potential for tumor growth or recurrence.7
Patients should be evaluated for an enlarged spleen or splenic rupture if they report upper left abdominal or shoulder pain. Patients who develop fever and lung infiltrates or respiratory distress should be evaluated for ARDS and treatment discontinued if a diagnosis is confirmed. Pegfilgrastim-jmdb should be permanently discontinued in patients who develop serious allergic reactions and should not be used in patients with a history of serious allergic reactions to pegfilgrastim or filgrastim products.
Dose-reduction or interruption should be considered in patients who develop glomerulonephritis. Complete blood counts should be monitored throughout treatment. Patients should be monitored closely for capillary leak syndrome and treated with standard therapy. Pegfilgrastim-jmdb is marketed as Fulphila.
Epoetin alfa-epbx was evaluated in 2 clinical trials in healthy individuals. The EPOE-12-02 trial established the PK and PD following a single subcutaneous dose of 100 U/kg in 81 participants. The EPOE-14-1 study was designed to determine the PK and PD of multiple doses of subcutaneous 100 U/kg 3 times weekly for 3 weeks in 129 participants. Both studies met prespecified criteria for PK and PD similarity to US-approved epoetin alfa, including geometric mean of area under the curve (AUC)0-120h, AUC0-inf, Cmax (maximum serum concentration achieved by a drug in a specified area of the body) and Emax (maximum response achievable for a drug dose).
Evidence of efficacy and safety were also evaluated using pooled data from EPOE-10-13 and EPOE-10-01, conducted in patients with chronic kidney disease, which was considered the most sensitive population in which to evaluate clinically meaningful differences between the biosimilar and reference product.8,9
There were no clinically meaningful differences in efficacy and a similar adverse event profile. The most common side effects include high blood pressure, joint pain, muscle spasm, fever, dizziness, respiratory infection, and cough, among others.
The recommended dose of epoetin alfa-epbx, which is marketed as Retacrit, is 40,000 Units weekly or 150 U/kg 3 times weekly in adults and 600 U/kg intravenously weekly in pediatric patients aged 5 years or younger. Epoetin alfa-epbx comes with a boxed warning to alert health care providers to the increased risks of death, heart problems, stroke, and tumor growth, or recurrence. The prescribing information also details warnings and precautions relating to these risks, as well as hypertension, seizures, lack or loss of hemoglobin response, pure red cell aplasia, serious allergic reactions, and severe cutaneous reactions.9
Blood pressure should be appropriately controlled before treatment initiation, treatment should be reduced or withheld if it becomes uncontrollable, and patients should be advised of the importance of compliance with anti-hypertensive medication and dietary restrictions. Patients should be monitored closely for premonitory neurologic symptoms and advised to contact their provider in the event of new-onset seizures, premonitory symptoms, or change in seizure frequency.
The prescribing information has dosing recommendations for lack or loss of hemoglobin response to epoetin alfa-epbx. If severe anemia or low reticulocyte count occur, treatment should be withheld and patients evaluated for neutralizing antibodies to erythropoietin and, in the event that PRCA is confirmed, treatment should be permanently discontinued. Treatment should be immediately and permanently discontinued for serious allergic reactions or severe cutaneous reactions.