What are these lists?
These lists are designed to help enable a user to see whether a particular biological product has been determined by the Food and Drug Administration (FDA) to be biosimilar to or interchangeable with a reference biological product. The lists cross-reference the names of biological products licensed under section 351(a) of the Public Health Service Act (PHS Act) with the names of biosimilar or interchangeable biological products licensed under section 351(k) of the PHS Act by the FDA (see below for an explanation of the sections 351(a) and 351(k) of the PHS Act). There will be separate lists for those biological products regulated by the Center for Drug Evaluation and Research (CDER) and the Center for Biologics Evaluation and Research (CBER).
For products licensed under section 351(a) of the PHS Act, the lists identify the date the biological product was licensed and whether FDA evaluated the biological product for reference product exclusivity under section 351(k)(7) of the PHS Act (see below for an explanation of reference product exclusivity). If FDA has determined that a biological product is protected by a period of reference product exclusivity, the list will identify the date of first licensure and the date that reference product exclusivity (including any attached pediatric exclusivity) will expire. The list will not identify periods of orphan exclusivity and their expiration dates for biological products as those dates are available at the searchable database for Orphan Designated and/or Approved Products.
Biosimilar and interchangeable biological products licensed under section 351(k) of the PHS Act will be listed under the reference product to which biosimilarity or interchangeability was demonstrated.
What is a reference product, biosimilar, and interchangeable product?
Under section 351(i)(4), a “reference product” is the single biological product licensed by FDA under section 351(a) of the PHS Act against which a proposed biological product is evaluated in an application submitted under section 351(k).
Under section 351(i)(2), “biosimilar” or “biosimilarity” means that the biological product is highly similar to the reference product notwithstanding minor differences in clinically inactive components, and there are no clinically meaningful differences between the biological product and the reference product in terms of safety, purity and potency of the product.
Under 351(k)(4), an “interchangeable” biological product is a product that has been shown to be biosimilar to the reference product, and can be expected to produce the same clinical result as the reference product in any given patient. In addition, to be determined to be an interchangeable biological product, it must be shown that 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 use of the biological product and the reference product is not greater than the risk of using the reference product without such alternation or switch.
What is reference product exclusivity?
Section 351(k)(7) of the PHS Act describes reference product exclusivity as the period of time from the date of first licensure of a reference product, the single biological product licensed under section 351(a) of the PHS Act against which a biological product is evaluated in a 351(k) application, during which a 351(k) sponsor is not permitted to submit and FDA is not permitted to license a 351(k) application that references the reference product. Specifically, if the reference product has reference product exclusivity under this section, approval of a 351(k) application may not be made effective until the date that is 12 years after the date of first licensure of the reference product, and a 351(k) application may not be submitted for review to FDA until the date that is 4 years after the date of first licensure. See 351(k)(7). For additional information on how FDA determines the date of first licensure and reference product exclusivity, please see the draft guidance for industry, “Reference Product Exclusivity for Biological Products Filed Under Section 351(a) of the PHS Act (PDF - 99KB).”
What does the reference product exclusivity expiry date indicate?
The reference product exclusivity expiry date indicates (1) the date that is 12 years from the date of first licensure as described in 351(k)(7); plus (2) any pediatric exclusivity granted pursuant to section 505(A) of the FD&C Act, if applicable. The reference product exclusivity expiry date is the date on which a 351(k) application referencing the reference product may be licensed, assuming it is not blocked by orphan exclusivity and otherwise meets the requirements for licensure under 351(k). To determine whether there is unexpired orphan exclusivity for an indication for which the reference product is licensed, please refer to the searchable database for Orphan Designated and/or Approved Products.
For additional information on determining the date of first licensure for purposes of determining reference product exclusivity, please see the draft guidance for industry, “Reference Product Exclusivity for Biological Products Filed Under Section 351(a) of the PHS Act (PDF - 99KB).”
Why is a determination of the date of first licensure not made for every 351(a) biological product licensed and currently marketed?
Although FDA has not made a determination of the date of first licensure for all 351(a) biological products included on the lists, it does not mean that the biological products on the list are not, or were not, eligible for exclusivity. A determination of the date of first licensure and of when any remaining reference product exclusivity will expire for a biological product submitted under section 351(a) of the PHS Act will generally be made for reasons of regulatory necessity and/or at the request of the 351(a) application license holder.
How often will these lists be updated?
As resources permit, these lists will be updated periodically when FDA licenses a biological product under section 351(a) or section 351(k) of the PHS Act and/or makes a determination regarding date of first licensure for a biological product licensed under section 351(a) of the PHS Act.
What should a healthcare practitioner keep in mind while using these lists?
Professional care and judgment should be exercised in using these lists. Evaluations of biosimilarity and interchangeability for biological products are based on scientific and medical evaluations by FDA under section 351(k) of the PHS Act. FDA’s determination that a product is biosimilar to a reference product or interchangeable with a reference product means that FDA has determined that the biological product meets the requirements for such products (see definitions above).
How do I obtain information not found on these lists?
Requests for more specific information may be obtained via the Freedom of Information Act. Requests should be submitted in writing or directed to the FDA's Division of Freedom of Information at:
Food and Drug Administration
Division of Freedom of Information
Office of the Executive Secretariat, OC
12420 Parklawn Drive
Rockville, MD 20857
Telephone: (301) 796-3900
The CDER Freedom of Information Office Electronic Reading Room and the CBER Freedom of Information Office Electronic Reading Room also have additional information available.
The “Purple Book” is an easy-to-remember nickname for the “Lists of Licensed Biological Products with Reference Product Exclusivity and Biosimilarity or Interchangeability Evaluations.” Using a color for the nickname of the list draws upon FDA’s long-held practice of using “The Orange Book” to refer to “Approved Drug Products with Therapeutic Equivalence Evaluations,” the Agency’s reference listing of all drugs approved under the Federal Food, Drug and Cosmetic Act. Over the years, health care professionals and other stakeholders have come to use the term “Orange Book” in place of this longer, official title. FDA wanted a similarly user-friendly term for a reference listing biologics, biosimilars, and interchangeable products. During a meeting, a staff member said, “how about purple?” Ever since, we’ve called it the “Purple Book.”
What if I have questions regarding these lists or believe they need to be changed?
For questions on CDER biological products or suggested changes to the lists, please contact the Division of Drug Information (CDER):
- By phone: (855) 543-3784 or (301) 796-3400
- By email at email@example.com
For questions on CBER biological products or suggested changes to the lists, please contact the Consumer Affairs Branch (CBER):
- By phone: (800) 835-4709 or (240) 402-8010
- By email: firstname.lastname@example.org