Uptake of biosimilars
While acquisition-cost benefits are the primary factor driving the uptake of biosimilars, quality, safety, and clinical efficacy considerations are vital in the decision to select a biosimilar over the originator biological, or another biosimilar of the same originator. For physicians, patients and payers, additional considerations include manufacturer reliability, reimbursement rates set by commercial payers or Medicare, and support services for physicians and patients.

Totality of evidence for biosimilars
For biosimilars, the regulatory review process is based on the totality of evidence generated in support of the biosimilarity claim.

The biosimilar clinical programme aims to demonstrate that the proposed biosimilar is similar to the originator biological based on analytical assessments, and that it does not have clinically meaningful differences from the originator biological, based on comparative clinical studies.

Extrapolation is a unique component of the biosimilar development programme, and involves using a biosimilar in indications that the originator biological is approved for, but in which the biosimilar was not clinically evaluated. The justification for extrapolation addresses whether the same mechanism of action applies in each indication, and in the similarity of the products’ immunogenicity, pharmacokinetic and biodistribution profiles in different patient populations.

Interchangeability
Interchangeability is a Food and Drug Administration (FDA) designation unique to the US which provides the basis for autonomous substitution, a practice whereby a pharmacist may dispense a biosimilar product instead of the prescribed biological without notification of, or permission from, the prescriber [2]. Substitution may lead to alternation between originator biologicals and biosimilars, in particular for treatments with a long course of therapy. The potential risks associated with multiple switching, such as immunogenicity and diminished efficacy, are evaluated in biosimilar clinical switching studies, and manufacturers who decide to pursue the optional designation of interchangeability are required to generate evidence through such studies.

While FDA has not yet granted an interchangeable designation to any biosimilar, most US states and Puerto Rico have passed legislation regulating substitution.

Naming
The FDA’s 2017 guidance assigns licensed biologicals a distinguishable, non-proprietary name consisting of the core name and an FDA designated, four-letter suffix, which is devoid of meaning [3]. The distinguishable suffix assists with pharmacovigilance and helps minimize the inadvertent substitution of products that are not interchangeable.

Experience in the US
There are a number of potential challenges limiting the uptake of biosimilars. Major considerations include a lack of understanding of the regulatory approval process, limited provider and patient education, concerns over the documentation of adverse events and cost or insurance coverage barriers. In addition, laws, regulations and guidance for biosimilar adoption and substitution vary between state and regional levels and are influenced by state-level factors including board of pharmacy requirements, insurance options and legislative and regulatory structures. These factors together impact pricing and reimbursement strategies. For biosimilars to be adopted into healthcare practice, prices need to be sufficiently low.

Conflict of interest
Mr Smeeding is at JeSTARx Group Texas; Dr Malone is at the College of Pharmacy at the University of Arizona in Tucson; Drs Ramchandani, Stolshek and Green are at Amgen Inc USA; and Mr Schneider is at MediHealthInsight in Arizona. For full details of the authors’ conflict of interest, see the research paper [1].

Related article
Clinician biosimilar prescribing habits and need for education

Barriers and facilitators to biosimilar prescribing in the UK

References
1. Smeeding J, Malone DC, Ramchandani M, Stolshek B, Green L, Schneider P. Biosimilars: considerations for payers. P T. 2019;44(2):54-63.
2. Derbyshire M. USA and Europe differ in interchangeability of biosimilars. Generics and Biosimilars Initiative Journal (GaBI Journal). 2017;6(4):183-4. doi:10.5639/gabij.2017.0604.039
3. GaBI Online - Generics and Biosimilars Initiative. FDA issues final guidance on naming biologicals [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2019 Apr 12]. Available from:
www.gabionline.net/Guidelines/FDA-issues-final-guidance-on-naming-biologicals 

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