2017 Winter Newsletter- Biosimilar Interchangeability

FDA Draft Guidance on Demonstrating Interchangeability

This January the FDA published draft guidance entitled, “Considerations in Demonstrating Interchangeability with a Reference Product”.  This long-awaited guidance provides biosimilar manufacturers with information on proving and supporting their claims of interchangeability status when submitting a 351(k) application.  The draft guidance indicates that biosimilars will require physician approval before pharmacy substitution, unless they gain interchangeability status.  Interchangeable products may be substituted at the pharmacy without prescriber approval or notification.  Just as small molecules must prove both pharmaceutical equivalence and bioequivalence to be considered therapeutically equivalent and substitutable (i.e.: FDA Orange Book A-rated), 351(k) products must show biosimilarity, clinical equivalence, and switchability to be considered interchangeable.

In order to be considered interchangeable to the reference product, the applicant must show that:

  1. Their biological product is biosimilar to the reference product
  2. Their product can be expected to produce the same clinical result as the reference product in any given patient for all indications
  3. For a biological product that is administered more than once to an individual, the risk in terms of safety or diminished efficacy of alternating or switching between the biological product and reference product is not greater than the risk of using the reference product without an alternation or switch

To prove that the product can produce equivalent clinical results, manufacturers must provide data on critical quality attributes, mechanisms of action (target receptors, receptor binding, dose response, etc.), pharmacokinetics, biodistribution, immunogenicity, toxicities, and many other factors.  With scientific justification, manufacturers can extrapolate clinical data to support interchangeability status for additional drug indications.  Although products may be approved as biosimilars if only applying for approval for one reference product indication, interchangeable products must be clinically equivalent and switchable for all indications of the reference product.

In addition to clinical studies, manufacturers must demonstrate the ability of their biosimilar to be switched back-and-forth with the reference product.  The FDA states that they expect applicants to include information from switching studies that mimic appropriate conditions of use.  The newly published draft guidance provides conditions for manufacturers to consider when designing a switching study, including study endpoints, analysis, population, routes of administration, and conditions of use.  The guidance notes that in general, post-marketing data would be insufficient to prove the impact of product switching and would not be enough to gain interchangeability status.  The FDA did state that post-marketing surveillance may be needed along with switching studies to demonstrate interchangeability if there is “residual uncertainty”.  If this draft guidance is finalized as is, it would mean that some biological products must be initially approved as biosimilars and can only gain interchangeability status after a time period significant enough to allow for post-marketing surveillance (likely several months to years).

Throughout the draft guidance, it is recommended that manufacturers work closely with the FDA to discuss their proposed switching studies and proposed presentation, i.e. product packaging, (vial, pre-filled syringe, auto-injector, etc.).  The FDA recommends that manufacturers only seek interchangeability status for products with the same presentation.  They also suggest that manufacturers discuss any proposed presentation changes with the FDA, as the presentation and its design will be thoroughly analyzed prior to granting interchangeability status.

The clinical data and additional study requirements necessary to prove interchangeability for 351(k) applicants will prove more burdensome and expensive than proving substitutability for traditional generic ANDA approvals.  With the amount of data needed to substantiate interchangeability status, there will be a much larger investment to bring an interchangeable product to market compared to a small molecule.  It is not surprising that biosimilars are expected to only provide 30% savings over their reference product.  As expected, the FDA places emphasis on the importance of post-marketing safety monitoring for biosimilar and interchangeable products.  The full 30-page draft guidance document can be found here.  PHSI recommends that all stakeholders monitor this guidance closely, as finalized guidance will have a tremendous impact on the future of biosimilars.

 

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