Introduction to Biologics and Biosimilars

Biologics are a fast-growing class of therapeutic compounds. In the United States, patent litigation between biologic manufacturers and biosimilar applicants occurs under the Biologics Price Competition and Innovation Act (BPCIA) at both the federal district court and appellate levels. Since many of the top-selling pharmaceuticals in the United States are biologics, there can be high stakes in BPCIA litigation.

In this series, we will discuss the fundamentals of biosimilar regulation and patent litigation under the BPCIA, starting with an introduction to biologics and biosimilars.

1. What is a biologic and how is it different from a small molecule drug?

Biologics are a diverse category of pharmaceutical products that are often produced or isolated from living sources, such as cells. They are used to prevent or treat a variety of medical conditions. Examples of biologics include blood, blood components, vaccines, monoclonal antibodies, therapeutic proteins, and gene therapy products. (See, e.g., FDA resources: Biosimilar and Interchangeable Products and What Are 'Biologics' Questions and Answers.)

Biologics differ from small molecule drugs in many respects. Unlike small molecule drugs, which are typically chemically-synthesized and have well-defined structures, most biologics are large, complex molecules, and they may consist of heterogeneous mixtures that cannot be easily characterized. In addition, because biologics are often made using living organisms, they require complex manufacturing processes that can lead to differences between manufactured lots.

Typical Small Molecule vs. Biological Drugs

2. What is a biosimilar drug and how is it different from a generic drug?

According to the BPCIA, a biosimilar is defined as a biologic that is "highly similar" to an existing FDA-approved reference biological product ("notwithstanding minor differences in clinically inactive components") and has "no clinically meaningful differences ... [from] the reference product in terms of [its] safety, purity, and potency." 42 U.S.C. 262(i)(2). Like generic drugs, biosimilars are approved through an abbreviated regulatory pathway and typically cost less than their biosimilar counterparts.

But there are important differences between biosimilars and generics. For example, whereas generic drugs have the same active ingredients as brand-name drugs, biosimilars are not necessarily identical to their reference products. Instead, biosimilars must be "highly similar" to their reference products in terms of their characteristics, mechanisms of action, and functions. (See, e.g., FDA resource: Biosimilar and Interchangeable Products.) In addition, whereas generic drug applicants must show that their products are bioequivalent to brand-name drugs in terms of the rate and extent that the active ingredient is released at the treatment site, biosimilar applicants must show there are no "clinically meaningful" differences in the safety and effectiveness of their products as compared to reference products. Biosimilars and generic drugs are also approved through separate regulatory pathways, and the laws that govern them, including laws on market entry and patent dispute resolution, are different.

Typical Generics vs. Biosimilars

3. How does a biosimilar applicant obtain FDA approval?

The BPCIA provides an abbreviated pathway to expedite the biosimilar approval process, which entails "a rigorous evaluation to ensure [] patients [of the] efficacy, safety, and quality" of biosimilar products. (See FDA resource: Biosimilar Development, Review, and Approval.) FDA may rely on "existing scientific knowledge about the safety and effectiveness of [an approved] reference product to support approval" of a corresponding biosimilar. (Id.) To leverage the nonclinical and clinical data of the reference product, the biosimilar applicant must prove "its proposed biosimilar product is highly similar to and has no clinically meaningful differences from the FDA-approved reference product" based on comparative data. (Id.) This may lead to faster product approval and thus earlier access for patients.

There are currently 26 FDA-approved biosimilars. FDA has approved biosimilars for nine different reference products, including Remicade®, Humira®, Neulasta®, Rituxan®, Avastin®, Herceptin®, Enbrel®, Neupogen®, and Epogen®.

4. What is the difference between a biosimilar and an interchangeable?

An interchangeable is a biosimilar that meets additional requirements under the BPCIA. 42 U.S.C. 262(k)(4). An interchangeable is "expected to produce the same clinical result as [its] reference product in any given patient." Id. at 262(k)(4)(A)(ii). And, for an interchangeable that will be "administered more than once to an individual, the risk in terms of safety or diminished efficacy of alternating or switching between use of the [interchangeable] and the reference product is not greater than the risk of using the reference product without such alteration or switch." Id. at 262(k)(4)(B).

An approved interchangeable may be substituted for the reference product without first consulting the prescriber, depending on the pharmacy laws and practices in the state. See id. at 262(i)(3). In contrast, if a patient wants to receive a biosimilar that has not been approved by FDA as interchangeable, the patient may need a prescription from their healthcare provider written specifically for that biosimilar.

To obtain approval as an interchangeable an applicant may need to perform additional clinical testing. For example, the applicant might conduct "switching studies" that show the proposed interchangeable will not increase safety risks or decrease product effectiveness if it is switched with the FDA-approved reference product.

There are currently no FDA-approved interchangeable biosimilars.

Authors: Michael Anderson, Kayleigh McGlynn, Tracea Rice, Jenny Shmuel, Cheryl Wang