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Study Suggests Biosimilar Suffixes Influence Patient Willingness to Switch


The random jumble of letters that the FDA attaches to new biologics and biosimilars plays a big role in patient acceptance of these drugs, investigators report.

A new study suggests the FDA’s naming convention for biosimilars and patients’ inability to switch to a biosimilar at the pharmacy limit biosimilar uptake by causing patients to perceive biosimilars as less similar to reference products.

Whereas generic drugs have the same nonproprietary name as their reference products, the FDA requires the addition of random 4-letter suffixes to the nonproprietary names of biosimilars. This practice differentiates biosimilars by name from their originators and from one another. Also, unlike generics, a prescription for a reference biologic is not interchangeable with one for the biosimilar at the pharmacy level; a new prescription is necessary for a patient to switch from the reference biologic to a biosimilar.

The investigators pointed out these policies are unique to the United States, saying “the United States is the only country in which a 4-letter suffix must be added to nonproprietary names of biosimilars and biologics and the only country in which biosimilarity and interchangeability have different regulatory requirements.”

Despite the potential of biosimilars to reduce costs, the authors wrote that patient interest in biosimilars is low, citing surveys suggesting “80% of patients taking biologics prefer not to switch to a biosimilar and are concerned about biosimilars’ efficacy and safety.”

Study Methodology

The investigators evaluated the effects of the naming convention and interchangeability on patient interest in biosimilars with 1306 participants standing in as hypothetical “patients.” Participants were asked to assume they had type 2 diabetes and that their disease was well-controlled with a fictitious reference biologic. They were then randomly assigned to view different versions of an advertisement for a fictitious biosimilar. The nonproprietary name of the biosimilar either had a 4-letter suffix or not. The advertisements either stated that the biosimilar requires or does not require a new prescription for patients currently taking the reference product, or did not mention interchangeability at all.

After viewing the advertisement, participants were asked to rate on a scale of 1 to 7 how likely they were to take the advertised biosimilar, to ask their doctor or payer about the biosimilar, or to research it online. They were also asked to rate how effective they thought the biosimilar was and how similar they thought it was to the reference biologic.

Based on average ratings, participants reported they would be more likely to talk to their doctor or payer, research the biosimilar, and use the biosimilar when they were told it would not require a new prescription. They also rated the biosimilar as more similar to the reference product under this scenario. When there was no mention of interchangeability, participants rated themselves more likely to use the biosimilar when the suffix was excluded from the nonproprietary name.

The authors say their findings suggest that 4-letter suffixes and the lack of interchangeability diminishes patients’ interest in biosimilars by lessening their perception of similarity between the reference product and biosimilar. Of the 2, interchangeability at the pharmacy appeared to be a stronger signal conveying similarity. “When given interchangeability information, patients rely on that signal alone, not on the biosimilar suffix, to infer drug similarity and form an opinion about the biosimilar,” they wrote.

The investigators acknowledged limitations of their study, in particular that it measured the attitudes of hypothetical patients, which may not necessarily reflect those of a real-world population with type 2 diabetes.

They added that the FDA’s policies on these matters have recently changed. Regarding the naming convention, as of March 2020, a 4-letter suffix will be added to the nonproprietary names of all newly approved biologics as well as biosimilars. For biosimilar insulins, current guidance from the FDA indicates that comparative clinical immunogenicity studies may still be needed to support immunogenicity, but not universally so, based on availability of convincing evidence supported by state-of-the-art technology that proposed biosimilar or interchangeable insulin products are “highly similar” to their reference products and there would be “little or no residual uncertainty.”

Based on their results and these policy changes, the investigators recommendedthat “future research could examine whether the new policy translates to reducing barriers to use biosimilar insulins and whether the naming convention adds more value than complexity for patients.”


Socal MP, Garrett JB, Tayler WB, Bai G, Anderson GF. Naming convention, interchangeability, and patient interest in biosimilars. Diabetes Spectr. 2020;33(3):273-279. doi:10.2337/ds19-0065

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