By Barbara Greenwood Dufour

Treatments called biosimilars have been gradually entering the Canadian pharmaceutical market, adding treatment options for patients with chronic, difficult-to-treat diseases. But what are they and who should use them?

Unlike traditional drugs

Biosimilars, formerly called subsequent entry biologics, are highly similar versions of biologics, or biologic drugs. Biologics are a class of drugs that are used to treat chronic diseases such as diabetes, anemia, inflammatory bowel disease, psoriasis, rheumatoid arthritis, hormone deficiency, and some forms of cancer. They are designed to control specific immune system responses — for example, to block an inflammatory response in the treatment of Crohn’s disease or, to treat certain cancers, stimulate an inflammatory response to attack cancer cells. Some examples of biologics include insulin analogues, erythropoietin, interferons, and monoclonal antibodies such as infliximab or adalimumab. What distinguishes them from traditional drugs is that they are manufactured using human or animal tissue or micro-organisms instead of chemical reactions.

In Canada, biosimilars can be brought to market after the patent for the original product — the “reference biologic drug” — has expired. More and more biosimilar treatments, therefore, can be expected to become available as the patents on biologics expire.

Not an exact copy, but similar

Like generic drugs, biosimilars are post-patent copies of original, brand name products. But, unlike generic drugs, which contain exactly the same active ingredients as the brand name versions, biosimilars are not exact copies. Whereas generic drugs and their brand name versions are small molecules that can be precisely replicated, biologics are large molecules that are produced using complex and proprietary manufacturing procedures. This makes it difficult to exactly duplicate all of their characteristics. In fact, because biologics are derived through the metabolism of living organisms, there could also be variations between batches of the same biologic drug.

Are biosimilars effective?

Not identical doesn’t mean not as effective. There is a process in place to make sure that every biosimilar marketed in Canada is a good and safe therapeutic alternative. Prior to being authorized for sale, the drug manufacturer must prove to Health Canada that the product is highly similar to the reference biologic drug according to a detailed set of criteria — including, for example, its biochemical structure and its pharmacodynamic (how the drug affects the patient) and pharmacokinetic (how the patient’s body processes the drug) characteristics — as well as in terms of its effectiveness and safety profile. This ensures that there are no clinically meaningful differences in safety, quality, and efficacy between the biosimilar and the original biologic.

When to substitute a biosimilar

Because, unlike generic drugs, biosimilars aren’t exact copies of the reference biologic products, pharmacists can’t automatically substitute a biosimilar for a biologic. Instead, whether to initiate treatment on or switch to a biosimilar is a decision that rests with health care providers and their patients with consideration to each patient’s unique situation and based on the available clinical evidence.

What’s the benefit of biosimilars?

Biosimilars typically cost less than biologics. When biosimilars become available, the resulting market competition tends to lead to lower prices. Given that biologics are some of the most costly treatments available — because their complexity makes them expensive to develop and manufacture — the cost savings could be significant. As a result, biosimilars have the potential to expand and improve access to treatment for patients and to save money that can be redirected elsewhere within the health care system.

To help health care decision-makers better understand biosimilars and their use in clinical practice, CADTH — an independent agency that finds, assesses, and summarizes the research on drugs, medical devices, tests, and procedures — has produced useful, evidence-based tools for health care providers and their patients. These tools, which briefly describe what biosimilars are and explain the differences between interchangeability and switching, can be found at www.cadth.ca/biosimilars. Tools developed to explain generic drugs and bioequivalence are available at www.cadth.ca/generics. For the evidence on specific biosimilars or biologics, you can search the CADTH website at www.cadth.ca/reports.

If you would like to learn more about CADTH and the evidence we have to offer to help guide health care decisions in Canada, visit www.cadth.ca, follow us on Twitter @CADTH_ACMTS, or contact a CADTH Liaison Officer in your region.

Barbara Greenwood Dufour is a Knowledge Mobilization Officer at CADTH.