FDA Purple Book: Biologics and Biosimilar Reference Guide
The FDA Purple Book, officially titled "Lists of Licensed Biological Products with Reference Product Exclusivity and Biosimilarity or Interchangeability Evaluations," is FDA's database of all biological products licensed under Section 351 of the Public Health Service (PHS) Act. It lists reference products, biosimilars, interchangeable biologics, and exclusivity information. The Purple Book serves the biologics market in a similar role to what the Orange Book serves for small molecule drugs: it is the definitive reference for identifying reference products, understanding competitive landscapes, and determining regulatory pathways for follow-on biological products under the 351(k) biosimilar pathway.
Key Takeaways
Key Takeaways
- The Purple Book lists all biological products licensed under PHS Act Section 351, including biosimilarity and interchangeability evaluations, replacing the Orange Book's role for biologics
- Reference product exclusivity under BPCIA provides 12 years of data protection (4-year submission block + 12-year approval block) from the date of first licensure
- Interchangeable biosimilars are flagged in the Purple Book, serving as the authoritative source for state pharmacy substitution authority
- The Purple Book is searchable at purplebooksearch.fda.gov and updated on an ongoing basis as new BLAs and biosimilar applications are approved
- The FDA Purple Book is an essential regulatory resource for any organization developing, manufacturing, or commercializing biological products. Since the passage of the Biologics Price Competition and Innovation Act (BPCIA) in 2010, the Purple Book has grown from a simple list to a comprehensive database that tracks reference product exclusivity, biosimilarity determinations, and interchangeability designations.
- For biosimilar developers, the Purple Book identifies reference products, exclusivity expiration dates, and existing biosimilar competition. For reference product sponsors, it tracks the competitive landscape. For healthcare providers and pharmacists, it identifies which biosimilars have been deemed interchangeable and eligible for substitution.
- In this guide, you'll learn:
- What the Purple Book is and its legal authority
- How to search the Purple Book database effectively
- Reference product exclusivity under the BPCIA
- Biosimilar and interchangeable product designations explained
- How the Purple Book differs from the Orange Book
- Using Purple Book data in 351(k) biosimilar development
- The impact of the BPCIA "patent dance" on Purple Book listings
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What Is the FDA Purple Book?
The FDA Purple Book is a publicly accessible database maintained by FDA's Center for Drug Evaluation and Research (CDER) and Center for Biologics Evaluation and Research (CBER) that lists all biological products licensed under Section 351 of the Public Health Service Act. It includes information about reference product exclusivity, biosimilarity evaluations, and interchangeability determinations. Its formal title is "Lists of Licensed Biological Products with Reference Product Exclusivity and Biosimilarity or Interchangeability Evaluations."
Legal Authority
The Purple Book's existence and content derive from several legislative and regulatory provisions:
| Authority | Provision |
|---|---|
| Biologics licensing | Section 351(a) of the PHS Act (42 USC 262(a)) |
| Biosimilar pathway | Section 351(k) of the PHS Act (enacted by BPCIA, 2010) |
| Reference product exclusivity | Section 351(k)(7) of the PHS Act |
| Interchangeability standard | Section 351(k)(4) of the PHS Act |
| Publication requirement | BPCIA provisions for public listing of licensed biologics |
What the Purple Book Contains
| Data Element | Description |
|---|---|
| Licensed biological products | All products approved under BLA (351(a)) pathway |
| Reference product designation | Which product serves as the reference for 351(k) applications |
| Biosimilar products | Products determined to be biosimilar to a reference product |
| Interchangeable products | Products determined to be interchangeable with a reference product |
| Exclusivity dates | Reference product exclusivity (12-year and 4-year provisions) |
| Orphan exclusivity | Orphan drug exclusivity for biological products |
| BLA holder | Organization holding the biologics license |
| Approval dates | Date of original licensure |
As of early 2026, the Purple Book lists over 300 licensed biological products and more than 50 approved biosimilars, reflecting the rapid growth of the biosimilar market since the first U.S. biosimilar approval in 2015.
How to Search the FDA Purple Book Database
The Purple Book is available as a searchable online database at FDA.gov (purplebooksearch.fda.gov). It replaced the earlier PDF-format publication in 2020.
Search Methods
Search by Proper Name (Non-Proprietary Name)
- Navigate to purplebooksearch.fda.gov
- Enter the established biological name (e.g., "adalimumab," "trastuzumab," "insulin glargine")
- Results display all licensed products containing that biologic, including reference products, biosimilars, and interchangeable products
Search by Proprietary (Brand) Name
- Enter the brand name (e.g., "Humira," "Herceptin," "Lantus")
- Results show the specific licensed product and any associated biosimilars
Search by BLA Number
- Enter the BLA application number
- Results show the specific licensed product
Browse All Products
- Use the "All Products" view to browse the complete list
- Filter by product type (reference, biosimilar, interchangeable)
- Sort by approval date, proper name, or applicant
Interpreting Search Results
Each Purple Book listing displays:
| Field | Meaning |
|---|---|
| BLA Number | Biologics License Application number |
| Proper Name | Non-proprietary (established) name with suffix |
| Proprietary Name | Brand/trade name |
| Applicant | BLA holder organization |
| Strength | Amount of active ingredient per unit |
| Dosage Form/Route | Product form and administration route |
| Product Presentation | Specific presentations (vials, syringes, pens) |
| Status | Licensed (active), withdrawn, or revoked |
| Licensure Date | Date of original approval |
| Reference Product | "Yes" if designated as reference product for 351(k) applications |
| Reference Product Exclusivity Expiry | End date of 12-year exclusivity period |
| Biosimilar | "Yes" if approved as biosimilar |
| Interchangeable | "Yes" if approved as interchangeable |
| Reference Product BLA | BLA number of the reference product (for biosimilars) |
When searching for a biologic product, use the established (proper) name rather than the brand name to capture all related products. Biosimilars use the same core proper name as the reference product but with a unique four-letter suffix (e.g., adalimumab-atto, adalimumab-adbm, adalimumab-bwwd). Searching by the core name captures all variants.
Biological Product Naming: The Suffix System
Since FDA's 2017 guidance on nonproprietary naming of biological products, all biological products (both reference and biosimilar) receive a unique four-letter suffix appended to the core proper name.
Naming Convention
| Product Type | Naming Format | Example |
|---|---|---|
| Reference product | [proper name]-[suffix] | adalimumab-adaz (not yet established for some older products) |
| Biosimilar | [proper name]-[suffix] | adalimumab-atto |
| Interchangeable | [proper name]-[suffix] | adalimumab-afzb (example) |
Purpose of the Suffix System
- Safety: Distinguishes between different manufacturers' products in prescribing and pharmacovigilance
- Tracking: Enables accurate adverse event reporting by specific product
- Substitution clarity: Identifies which products are interchangeable
- No clinical significance: The suffix does not indicate any clinical difference between biosimilar and reference products
Reference Product Exclusivity Under BPCIA
The BPCIA establishes exclusivity periods that protect reference biological products from biosimilar competition.
Exclusivity Framework
| Exclusivity Type | Duration | Effect |
|---|---|---|
| 4-year data exclusivity | 4 years from reference product licensure | No 351(k) application may be submitted for 4 years |
| 12-year market exclusivity | 12 years from reference product licensure | No 351(k) application may be approved for 12 years |
| First interchangeable exclusivity | 1 year (or 18 months in some circumstances) | No subsequent 351(k) product may be deemed interchangeable |
| Orphan exclusivity | 7 years | No approval for same biological product, same indication |
| Pediatric exclusivity | 6 months added | Extends existing exclusivity periods |
How Exclusivity Periods Work
4-Year Submission Block:
- Beginning on the date the reference product was first licensed, no 351(k) application referencing that product may be submitted for 4 years
- After 4 years, 351(k) applications may be submitted but not approved until the 12-year period expires
12-Year Approval Block:
- No 351(k) application may be approved until 12 years after the reference product's first licensure date
- This is the primary market protection for innovator biologics
- The 12-year period is substantially longer than the 5-year NCE exclusivity for small molecule drugs under the Hatch-Waxman Act
First Interchangeable Exclusivity:
- The first biosimilar product to receive an interchangeability determination receives a period of exclusivity
- During this period, no subsequent biosimilar can be deemed interchangeable
- The exclusivity period is the later of: (1) 1 year after the first commercial marketing of the first interchangeable product, or (2) 18 months after a final court decision in patent litigation, or (3) 42 months after approval if litigation is ongoing
The first reference product exclusivity expirations began occurring in 2023-2024, triggering a wave of biosimilar approvals. By 2026, biosimilars are available for multiple blockbuster biologics including adalimumab, bevacizumab, trastuzumab, rituximab, and insulin glargine.
Biosimilar vs. Interchangeable Designations
The Purple Book distinguishes between two types of follow-on biological products:
Biosimilar
| Attribute | Definition |
|---|---|
| Legal standard | "Highly similar" to reference product notwithstanding minor differences in clinically inactive components, with no clinically meaningful differences in safety, purity, or potency (Section 351(k)(2)) |
| Substitution | Not automatically substitutable; requires prescriber authorization in most states |
| Purple Book designation | Listed as "Biosimilar: Yes" |
| Data requirements | Analytical similarity, animal studies (if needed), clinical PK/PD study, at least one clinical immunogenicity study |
Interchangeable
| Attribute | Definition |
|---|---|
| Legal standard | Biosimilar that can be expected to produce the same clinical result in any given patient AND, for products administered more than once, the risk of alternating or switching between the interchangeable and reference product is not greater than using the reference alone (Section 351(k)(4)) |
| Substitution | May be substituted at the pharmacy without prescriber intervention (state laws apply) |
| Purple Book designation | Listed as "Interchangeable: Yes" |
| Data requirements | All biosimilar requirements PLUS switching study data demonstrating no increased risk from alternating |
Practical Implications
| Feature | Biosimilar | Interchangeable |
|---|---|---|
| Pharmacy substitution | No (in most states) | Yes (in most states) |
| Formulary positioning | May require separate formulary listing | Can be positioned as automatic alternative |
| Market access | Requires active prescriber selection | Benefits from automatic substitution |
| Pricing pressure | Moderate | Higher (due to automatic substitution) |
| Development cost | Lower | Higher (requires switching study) |
Purple Book vs. Orange Book: Key Differences
| Feature | Purple Book | Orange Book |
|---|---|---|
| Products covered | Biological products (BLAs) | Drug products (NDAs, ANDAs) |
| Regulatory statute | Section 351 PHS Act | Section 505 FD&C Act |
| Follow-on pathway | 351(k) biosimilar | 505(j) ANDA |
| Equivalence standard | Biosimilarity / Interchangeability | Therapeutic equivalence (TE codes) |
| Patent listings | Not listed in Purple Book | Mandatory listing by NDA holder |
| Exclusivity periods | 12-year market, 4-year data | 5-year NCE, 3-year NCI |
| Substitution mechanism | Interchangeability determination | A-rating (AB, AP, AT) |
| Database format | Online searchable database | Online database + annual print edition |
| Patent dispute mechanism | BPCIA "patent dance" (separate from database) | Paragraph IV certification (linked to database) |
Why Patents Are Not in the Purple Book
Unlike the Orange Book, the Purple Book does not contain patent listings. Patent disputes for biologics are handled through the BPCIA's "patent dance" provisions (Section 351(l) of the PHS Act), which is a separate negotiation process between the reference product sponsor and the biosimilar applicant. This process occurs outside the FDA regulatory framework, in contrast to the Orange Book patent certification system for small molecule drugs.
The BPCIA patent dance involves:
- Information exchange: Biosimilar applicant shares its application and manufacturing information with the reference product sponsor
- Patent identification: Reference product sponsor identifies relevant patents
- Negotiation: Parties negotiate which patents will be litigated immediately vs. later
- Litigation: Patent disputes are resolved through federal court proceedings
Using Purple Book Data in 351(k) Development
For companies developing biosimilar products, the Purple Book is the starting point for regulatory strategy.
Step 1: Identify the Reference Product
Search the Purple Book by established name or brand name to identify:
- The reference product's BLA number
- The reference product sponsor
- All approved strengths and presentations
- Exclusivity expiration dates
Step 2: Assess the Competitive Landscape
Review the Purple Book for:
| Data Point | Strategic Insight |
|---|---|
| Number of approved biosimilars | Market saturation level |
| Interchangeable products | Competitive advantage of existing products |
| Exclusivity expiration | When 351(k) approval is possible |
| Pending applications | Pipeline of biosimilars (not directly in Purple Book; check FDA announcements) |
Step 3: Determine Regulatory Timeline
| Exclusivity Status | Impact on 351(k) Timeline |
|---|---|
| Reference product licensed <4 years ago | Cannot submit 351(k) application yet |
| Reference product licensed 4-12 years ago | Can submit; cannot be approved until Year 12 |
| Reference product licensed >12 years ago | Can submit and be approved (subject to review timeline) |
| First interchangeable exclusivity active | Can be approved as biosimilar but not as interchangeable |
Step 4: Plan for Interchangeability
If pursuing interchangeability:
- Review existing interchangeable designations for the reference product
- Assess whether first interchangeable exclusivity is available
- Plan switching study design (additional cost and time vs. biosimilar-only strategy)
- Evaluate state substitution laws to determine commercial value of interchangeability
Biologics Transitioning from NDA to BLA
The Biologics Price Competition and Innovation Act included provisions (implemented March 23, 2020) that transitioned certain biological products previously regulated as drugs under the FD&C Act to regulation as biological products under the PHS Act. This transition affected products such as insulin, human growth hormone, and certain other protein products.
Impact on the Purple Book
Products that transitioned from NDA to BLA:
- Now appear in the Purple Book instead of the Orange Book
- Are eligible as reference products for 351(k) biosimilar applications
- The March 23, 2020 transition date is treated as the date of licensure for purposes of 351(k)(7) exclusivity calculations; however, the practical exclusivity impact varies by product depending on prior NDA approval history and existing exclusivity
- Previous ANDAs for these products were "deemed" as 351(k) applications
Notable Transitioned Products
| Product Class | Examples | Purple Book Impact |
|---|---|---|
| Insulin | Insulin glargine, insulin lispro, insulin aspart | Now listed as reference biological products |
| Human growth hormone | Somatropin | Now listed as reference biological product |
| Glucagon | Glucagon | Now listed as reference biological product |
The March 2020 biologics transition moved approximately 100 product applications from NDA to BLA status, significantly expanding the Purple Book and the landscape of products eligible for the 351(k) biosimilar pathway.
Limitations of the Purple Book
While the Purple Book is essential, it has limitations that users should understand:
| Limitation | Implication |
|---|---|
| No patent information | Must conduct separate patent analysis using USPTO and BPCIA patent dance |
| No pricing information | Must use separate sources for commercial/pricing analysis |
| No clinical data | Must review BLA approval packages and published literature for clinical details |
| No pending applications | Does not show 351(k) applications under review |
| Limited international data | Covers U.S. licensed products only; EMA's biosimilar list is separate |
| Exclusivity calculations | Verify exclusivity dates independently; complex interactions with pediatric exclusivity |
References
The online Purple Book database (purplebooksearch.fda.gov) is updated on a rolling basis as FDA licenses new biological products, approves biosimilars, or makes interchangeability determinations. New approvals typically appear within days of the licensing date. For the most current information, always use the online database rather than any downloaded snapshots.