Four-Letter Suffixes May Be FDA’s Own Brand of Misleading Information on Biosimilars

Its intent was to improve tracking and reportability, but the Food and Drug Administration’s decision to employ four-letter suffixes for biosimilars may have created its own misleading information. This would be truly ironic, considering FDA’s own efforts to restrict or eliminate misleading information that could deter biosimilar utilization.

New evidence has been published recently that suggests that the four-letter suffix will likely succeed—in confusing the public and misleading consumers.

Four-letter suffixes

Interestingly, the study appeared in Diabetes Spectrum, and involved biosimilar insulins (of which none have been officially approved by the FDA). It is easy, however, to see how these findings may apply to the biosimilars approved and available for prescription in the US.

Researchers from the Johns Hopkins School of Public Health, Clemson University, and Brigham Young conducted experiments in which more than 1,300 individuals volunteered to playact the role of patients with type 2 diabetes whose glycemic levels were well controlled with a reference insulin product. They were randomized to review one of two versions of advertisement for an imaginary biosimilar insulin. One version of the ad mentioned a four-letter suffix, the other did not. The advertisements also varied in one other way: They (1) stated that the biosimilar requires a new prescription (i.e., not interchangeable), (2) did not require a new prescription from the doctor (interchangeable), or (3) did not disclose any information about interchangeability.

Participants were then required to rate the following probabilities on a seven-point scale:

  • They would ask their doctor or health plan about the biosimilar
  • They would find out more information about the biosimilar on the Web
  • The clinical effectiveness of the biosimilar relative to the reference drug
  • The degree of similarity of the biosimilar compared with the reference insulin
  • They would switch to the biosimilar

Interchangeability, Four-Letter Suffixes, and Impressions

The researchers found that these hypothetical patients would be more open to asking about or using a biosimilar when they believed it was interchangeable with the reference insulin product. If they were informed that the product did not require a new prescription from their doctor, they considered the biosimilar “more similar” to the reference product. However, in the scenario in which a new prescription was needed, the patients were more likely to use the biosimilar if it was discussed without a four-letter suffix. When the four-letter suffix was included, participants’ likelihood of switching to the biosimilar dropped significantly.

The authors concluded, “Absent the mention of needing a new prescription, adding four-letter suffixes to biosimilars’ nonproprietary names decreased participants’ likelihood of using the biosimilars.”

Let us put aside the interchangeability question, because there are no interchangeable biosimilar insulins currently approved (or biosimilar insulins or interchangeable biosimilars of any type in the US).

Since its initial draft guidance, the FDA’s rules on biosimilar nomenclature—specifically the four-letter suffix—has raised my blood pressure and the ire of many payers. Although this study does not consider the most recent iteration of the rule, which includes four-letter suffixes on new reference biologics as well, there are no suffixes applied to the reference products for insulin glargine or aspart. The researchers give ample argument to those who believe the damage has already been done.

There is little reason to believe that these research results involving diabetes should not be applicable to other diseases for which patients receive chronic treatment. However, it is nearly impossible to calculate the effect the naming system has had on actual biosimilar uptake.

The authors do suggest that FDA may have taken a wrong turn on the path to biosimilar acceptance and uptake. They wrote that “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.”

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