This feature is part of a series focused exclusively on biosimilars. To view other posts in the series, check out the spotlight page.
Generic drugs are a common sight in medicine cabinets and pharmacies across the U.S. Yet consumers who take these cheaper copycat medicines might glance askance at their strange-sounding medical names. The generic copy of the well-known statin Crestor, for example, is labeled as rosuvastatin.
But for medical professionals, the practice of calling drugs by their medical, non-proprietary name is second nature. The generic copy of every so-called small molecule drug is chemically identical to its brand name counterpart. And with (potentially) multiple producers for the same generic, identifying a drug by its non-proprietary name is clearer and more precise.
Things might get more complicated, however, as biosimilars - copies of biologic drugs - begin to proliferate on the U.S. market. There are currently four such drug approved by the Food and Drug Administration, all of which were okayed for use within the last two years.
Unlike generics, biosimilars are not chemically identical to the drug they imitate. Rather, biosimilars are “highly similar," showing no clinically meaningful differences in safety and efficacy.
How to distinguish between a brand-name biologic and its highly similar biosimilar copy has been a major regulatory headache for the FDA, one it hopes it has finally solved with the release of new guidance last week.
Biosimilar brand names, also known as proprietary names, have so far followed the pharma industry’s well-worn tradition of incongruous consonant combinations and softly evoked homonyms. Zarxio. Inflectra. Erelzi. Amjevita.
But since each is slightly different from its branded counterpart, the FDA had attached a suffix of four consonants to the end of each non-proprietary name to distinguish between the two. Infliximab (Remicade) becomes infliximab-dyyb (Inflectra). Adalimumab (Humira) becomes adalimumab-atto (Amjevita).
Until last week, the FDA had no officially formalized approach for adding a suffix. On January 12, the agency released its long-awaited final guidance on how to name biologic and biosimilar drugs, giving clarity to the industry after lengthy deliberations.
The guidance cements the practice of attaching a meaningless four-letter suffix to the nonproprietary names of both biologics and biosimilars — an effort designed to help distinguish between the two types of drugs.
Despite the apparent dullness of a regulatory document on suffixes, the FDA’s action was an important step for the emerging biosimilar field.
Distinction without difference?
While the debate over suffixes may seem a case of splitting hairs, it is not an insignificant matter to the companies and providers who will be dealing with biosimilar entrants.
All four biosimilars currently approved are not considered "interchangeable" with their reference biologic, meaning pharmacists cannot choose to dole out the biosimilar in place of the biologic — a common practice with generics and small-molecule drugs.
A suffix would help differentiate the products to alert providers to the difference, hopefully preventing inadvertent substitution between drugs which have not been approved for interchangeable use.
Flagging which drugs are made by separate biosimilar drugmakers should also help facilitate the tracking of product-specific adverse events.
Notably, the FDA’s guidance applies to currently licensed biologic drugs as well, not just biosimilars. For now, the FDA plans to assign suffixes to a limited group of already approved biologics and is considering a process for implementing the new naming convention across all biologics.
While this will change the medical name for dozens of well-known drugs, the FDA hopes adding a suffix to all biologic products will help avoid the impression that biosimilars are somehow substandard.
Not without controversy
Whether or not the suffix would contain some meaning had been a point of contention between the FDA and industry. Trade associations PhRMA and BIO had both pushed for the suffixes to be meaningful, such as containing letters suggestive of the biosimilar drugmaker.
PhRMA, for example, recommended the suffix should be derived from the name of the license holder, much like the filgrastim-sndz used for Zarxio, approved several months before the FDA’s naming proposal. (The FDA has proposed to change filgrastim-sndz’s name.)
Novartis, on the other hand, believes biosimilars should follow in the tradition of generic drugs. "It is not necessary to modify the existing naming system that has worked well for over 60 years. Biosimilars and interchangeable biologics should share the same non-proprietary name as their respective reference products," the Swiss pharma wrote in a comment on the FDA’s draft proposal in the Federal Register.
The Swiss pharma also argued that if a suffix must be imposed, then each company should be given one suffix that is derived from the company’s name. "Evidence reveals that random letter suffixes will not be well remembered, defeating the stated FDA proposes of safety and enhanced pharmacovigilance."
Earlier this week - just days after the FDA finalized its thinking on biosimilar naming - the agency issued draft guidance on how the industry should approach proving interchangeability between biosimilars and biologic drugs.
This piece of guidance, while now open for comment from stakeholders, fills in one of the major remaining gaps in the regulatory framework surrounding the copycat biologics.
In addition to meeting all standards of biosimilarity, interchangeable drugs must produce "the same clinical result as the reference product in any given patient," the FDA wrote in its guidance. Furthermore, the regulator expects an interchangeable product will produce that result across all approved uses of the reference product.
Drugmakers who hope to secure an interchangeable classification for their proposed biosimilar will have to carry out switching studies that assess the risk of substituting a biosimilar for its reference product, the guidance said.
While the naming convention for biosimilars is now set, the FDA said it is still continuing to consider the appropriate suffix for interchangeable products.
The rapid acceleration of biosimilar development in the U.S. underpins the importance of the FDA’s regulatory framework.
The concept of generic drug names is widely accepted and understood by healthcare providers and patients. With biosimilars still suffering from a lack of awareness, nailing a consistent and understandable approach to biosimilar names may be more important than just four letters.