In contrast to the conventional drug approval pathway in which drugs are reviewed under a New Drug Application (NDA), approval of a biological product is done under a separate pathway known as the Biologics License Application (BLA). Examples of biologics include therapeutic proteins such as insulin, monoclonal antibodies, vaccines, and blood-derived products. While the NDA and BLA processes are similar, they are not identical. The typical generic drug provisions (e.g., same active ingredient, bioequivalence) do not apply to BLAs. Instead, the single biological product already approved by the United States (US) Food and Drug Administration (FDA) is referred to as the reference product; the new potential biosimilar is then compared to the reference product. For approval as a biosimilar, the manufacturer must demonstrate that the agent is highly similar with no clinically meaningful differences.
In July 2018, the FDA released their Biosimilar Action Plan, described by then FDA Commissioner Dr. Scott Gottlieb, as “aimed at promoting competition and affordability.” Then, in December 2018, the FDA announced the plan to transition biological products that were historically regulated as drugs and approved via NDAs to the biologics pathway, taking effect in March 2020. These products include insulin, human growth hormone, and glucagon, among others. This change was mandated by Congress in the 2009 Biologics Price Competition and Innovation Act, which allowed 10 years for the transition. When considered as drugs under the NDA pathway, it was virtually impossible to develop a generic equivalent due to the nature and the inherent variation in the manufacturing process of these products. On March 23, 2020, the FDA issued a statement noting that this change is now in effect.
However, in the US, even if an agent is determined to be biosimilar, it is not automatically interchangeable (a process by which a product can be substituted for another without the approval of the prescriber). For a biosimilar to be considered interchangeable by the FDA, it must meet even more rigorous requirements and be approved as interchangeable. For products that are biosimilar but not interchangeable, the prescriber still needs to write for the specific product. In addition, even if determined to be interchangeable by the FDA, state pharmacy laws may further regulate what substitutions may be made at the pharmacy level without the approval of the prescriber. Just as a listing of generic equivalents is available through the FDA in their Orange Book, the FDA lists biologics and any respective biosimilars in their Purple Book. Recently converted to an online database format, the Purple Book provides details on reference products, their corresponding approved biosimilars, and whether or not the biosimilar is interchangeable. To date, no biosimilar has been designated as interchangeable.
As described in a previous blog post, the cost of insulin has risen substantially, leading patients to take desperate measures. At a time of economic instability and health uncertainty, these access concerns are even larger. Now that these products have transitioned to the biologic approval pathway, once patent exclusivity has passed, biosimilars can be developed, evaluated, and approved. Moreover, biosimilars can be reviewed further and may be classified as interchangeable, which can further alleviate the burden by allowing substitution at the retail level depending on local laws. This landmark change can promote market competition, potentially driving increased availability and decreased cost. The FDA reports that even having one generic drug on the market can decrease prices to approximately two-thirds of the price without competition. Generally, initial list prices of launched biosimilars have been 15% to 35% lower than their reference products. Most importantly, in their announcement of this change on March 23, the FDA pledged that they are ready to review eligible applications to ensure efficient approval. Ultimately, this revised process will provide an opportunity for other manufacturers to introduce safe and effective product competition without clinically meaningful differences. While this may be challenging in light of the ongoing global pandemic, this change, 10 years in the making, offers hope for patients who use these medications.