What are Biosimilars?

Biosimilars, or biosimilar medicines/drugs, are biological medicines that are designed to be near-exact versions of biological medicines already available on the market.

Biological medicines themselves are by definition drugs that are either made from or derived from a biological source. One of the more commonly known biological drugs is insulin.

Biosimilar drugs and generic drugs are not the same thing. A generic drug is a drug that is identical to its reference medicine (the medicine it copies). For instance, Walmart's Equate brand of Acetaminophen is a generic version of its reference medicine, Tylenol.

Biosimilar drugs are not identical to their reference medicines. They are biological drugs that are developed to be similar to an existing biological drug. As long as a generic is defined as being identical to a reference drug, the notion of a 'generic' biosimilar will not exist. That said, biosimilar drugs bear the same purpose as generic drugs in that they are supposed to be significantly cheaper versions of a brand name drug that is no longer under patent protection.

Because biological drugs are much more complex than non-biological drugs, they are therefore much harder to copy in biosimilar form, and in fact regulatory agencies accept that there will be some molecular variability between a biological drug and its biosimilar version or versions. However, when regulatory agencies approve a biosimilar drug, they do so having been shown to their satisfaction that this minor variability doesn't affect either the safety or efficacy of the biosimilar in question.

Evaluating Biosimilar Drugs

When evaluating a biosimilar drug to determine whether to authorize its sale or not, regulatory agencies do not require the amount of clinical studies that they might normally have required for the approval of the reference medicine. In fact, because biosimilars don't become available until its reference medicine is no longer under patent protection, agencies already know the clinical benefit of the reference drug; what they instead tend to seek are trials comparing a biosimilar with its reference drug that demonstrate no significant differences between the two.

Ultimately, the regulatory agency wants to see that the biosimilar is in every way equivalent to its reference medicine in terms of safety, efficacy, quality, biological activity, risk and benefit.

Biosimilar Drugs in the US

The United States trails much of the world when it comes to approving biosimilar drugs for the market. In fact, while several dozen other countries currently permit biosimilar drugs, the US Food and Drug Administration has not approved any biosimilar drug, for any indication … yet.

That is likely to change very soon, as the FDA has created an approval pathway for biosimilars and just accepted the first application to market a biosimilar drug, that of Novartis' Zarzio, whose reference medicine is the G-CSF injection Neupogen.