FDA Purple Book for peptide biologics: how to verify licenses, biosimilars, and product identity

01

The Purple Book answers a specific approval-database question

FDA’s Purple Book contains licensed biological products regulated by CDER and CBER. It includes original 351(a) products and products licensed through the 351(k) biosimilar pathway, including FDA interchangeability determinations. It is an approval database, not a directory of every molecule described as biologic or peptide.

For provider research, the database can confirm the proprietary and proper names, BLA number, sponsor, approval date, dosage form, route, strength, presentation, license type, and marketing status. Those fields help test whether a clinic is discussing the same finished product shown in FDA’s record.

Hepcludex offers a current example: its Purple Book page identifies bulevirtide-gmod, BLA 761468, a 351(a) license, a single-dose injection presentation, and a May 22, 2026 approval date. The entry does not license an unnamed bulevirtide vial from another source.

02

Purple Book, Orange Book, and Drugs@FDA have different scopes

FDA approval pathways do not divide neatly by the marketing word peptide. Some peptide products are approved under new drug applications and appear in Drugs@FDA and the Orange Book; other products are licensed as biologics and appear in the Purple Book. Product regulation and application history determine the right database.

The Orange Book focuses on approved drug products with therapeutic-equivalence evaluations and approved generics under ANDAs. The Purple Book focuses on licensed biologics and FDA’s reference-product, biosimilar, and interchangeability relationships. Drugs@FDA provides application histories, labels, letters, and review material for many drug and biologic products.

Search more than one database when the pathway is unclear. A missing result can reflect spelling, a proper-name suffix, an older transition product, a different application type, or an unapproved product. Do not turn one empty search into a regulatory conclusion without checking the exact name and alternate database.

03

How to read 351(a), biosimilar, and interchangeable

A 351(a) entry identifies a biological product licensed through a stand-alone BLA. A reference product is the single licensed product against which a proposed biosimilar is evaluated. FDA defines a biosimilar as highly similar to its reference product with no clinically meaningful differences in safety, purity, and potency.

An interchangeable product is a biosimilar that meets additional statutory criteria. FDA explains that interchangeability addresses expectations for the same clinical result and, for repeatedly administered products, the risk of alternating or switching. State pharmacy law and prescribing context can still affect substitution.

These terms are formal determinations. Similar peptide, same amino acids, compounded alternative, custom biologic, research grade, and bioidentical do not mean FDA-licensed biosimilar or interchangeable. If the Purple Book does not show the claimed relationship, ask the seller for the exact application and FDA record.

04

What a Purple Book result can—and cannot—prove

A matched entry is strong evidence that FDA licensed the named finished biological product. It can identify the sponsor, license type, presentation, and approval date and may link to labeling. It can also show whether FDA determined another listed product to be biosimilar or interchangeable.

The record does not establish that a product is suitable for an individual, covered by insurance, available from a clinic, free from recalls, or approved for a use outside its label. It also does not turn every package using the proper name into the licensed product.

The database cannot validate a compounded product, bulk ingredient, or research chemical. Compounded drugs do not become biosimilars through chemical comparison, a certificate of analysis, or a clinician’s statement. A biosimilar requires its own FDA-licensed 351(k) application.

05

A step-by-step verification workflow

Begin with the package or provider page and record the brand, proper name, four-letter suffix if present, manufacturer, route, strength, and presentation. Search the Purple Book using the brand and proper name. Open the individual product record instead of stopping at an autosuggest result.

Match each field. A correct active name paired with a different sponsor, strength, route, or presentation can signal that the provider is discussing another product. Open the current label and approval history, then confirm the indication and dates. If the product is absent, search Drugs@FDA and the Orange Book.

For a claimed biosimilar, find the linked reference product and confirm whether FDA labels it biosimilar or interchangeable. If a provider uses generic or biosimilar for a compounded drug, ask for the ANDA or BLA number. No application number is a warning sign that the classification may be marketing language.

• →Brand and proper name
• →Four-letter suffix where applicable
• →BLA or application number
• →Sponsor and marketing status
• →Route, strength, and presentation
• →Reference, biosimilar, or interchangeable status
• →Current label and approved indication

06

Use the result in provider research without overclaiming

A directory can record that the exact product appears in the Purple Book and link the record. It should not label a provider verified merely because the provider mentions a licensed biologic. The dispensing package and pharmacy must still match the approved product.

Separate product identity from prescribing. FDA licensure does not show that a clinic evaluated a patient appropriately, follows the current label, manages adverse effects, or has authority in the patient’s state. Verify the clinician, pharmacy, care pathway, and follow-up separately.

Finally, date the check. FDA can add products, supplements, labels, safety information, discontinuation status, and biosimilar determinations. A current product record should be paired with current labeling and professional advice for treatment decisions.