By William Elliott, MD, FACP, and James Chan, PharmD, PhD

Dr. Elliott is Medical Director, Pharmacy, Northern California Kaiser Permanente, and Assistant Clinical Professor of Medicine, University of California, San Francisco. Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA.

Drs. Elliott and Chan report no financial relationships relevant to this field of study.

The FDA has approved a biosimilar to the tumor necrosis factor (TNF-alpha) blocker etanercept (Enbrel). Biosimilars are biological products that are highly similar to the reference product, notwithstanding minor differences in clinically inactive components. There are no clinically meaningful differences between the biological product and the reference product in terms of the safety, purity, and potency of the product.1 Etanercept-szzs is the third biosimilar drug to be approved in the United States. It is marketed as Erelzi.


Etanercept-szzs is indicated for moderate to severe active rheumatoid arthritis (RA), moderate to severe active polyarticular juvenile idiopathic arthritis (JIA), psoriatic arthritis (PsA) , active ankylosing spondylitis (AS), and chronic moderate to severe plaque psoriasis (PsO).2


The recommended dose for RA and PsA is 50 mg once weekly with or without methotrexate; for AS, 50 mg once weekly; for PsO, 50 mg twice weekly for three months, then 50 mg once weekly; and JIA (> 63 kg), 0.8 mg/kg weekly, with a maximum of 50 mg per week.2 Etanercept-szzs is available as 25 mg/0.5 mL and 50 mg/mL single-dose prefilled syringe and 50 mg/mL single-dose prefilled Sensoready Pen.


Etanercept-szzs provides an alternative to etanercept (Enbrel).


Etanercept-szzs currently is not designated as interchangeable to Enbrel, which means it cannot be substituted without provider approval.


Etanercept-szzs was approved based on elements of biosimilarity. These include structural and functional characterization, animal study data, human pharmacokinetic and pharmacodynamic data, clinical immunogenicity, and other safety and effectiveness data.3 In vitro tests showed that etanercept-szzs and etanercept had comparable binding affinities to TNF-alpha, C1q complement, and complete panel of Fc receptors.4 There was sufficient data from the clinical studies section for the prescribing information to be the same for etanercept-szzs and etanercept. To be labeled as interchangeable, the biosimilar product is expected to produce the same clinical result as the reference product in any given patient. Additionally, if a product is to be administered to a patient more than once, the risk in terms of safety and effectiveness of alternating or switching between the interchangeable and the reference product is not greater than the risk of using the reference product without alternating or switching.5


Etanercept-szzs is the first biosimilar to Enbrel approved in the United States. It joins infliximab-dyyb, a biosimilar to Remicade, as commonly used biologics for chronic inflammatory diseases. Neither was approved as an interchangeable product, thus neither can be substituted for the reference drug without provider approval. Pricing for etanercept-szzs was not available at the time of this review.


  1. U.S. Department of Health and Human Services. Biosimilars: Questions and Answers Regarding Implementation of the Biologics Price Competition and Innovation Act of 2009. Available at: Accessed Sept. 9, 2016.
  2. Erelzi Prescribing Information. Sandoz Inc. August 2016.
  3. FDA News Release. FDA approves Erelzi, a biosimilar to Enbrel. Available at: Accessed Sept. 9, 2016.
  4. Hofmann HP, Kronthaler U, Fritsch C, et al. Characterization and non-clinical assessment of the proposed etanercept biosimilar GP2015 with originator etanercept (Enbrel). Expert Opin Biol Ther 2016;16:1185-1195.
  5. FDA. Information for Consumers (Biosimilars). Available at: Accessed Sept. 14, 2016.