NDA, BLA, or ANDA: which application applies, and what changes between them

Every marketing application to FDA for a therapeutic product routes into one of three statutory buckets: a New Drug Application (NDA), a Biologics License Application (BLA), or an Abbreviated New Drug Application (ANDA). The choice is not a matter of preference. It is dictated by two questions: is the product a "drug" or a "biological product," and is the sponsor bringing its own full evidence package or relying on a product FDA has already approved. Get the routing wrong and the submission is built against the wrong evidence standard, the wrong review center, and the wrong exclusivity and intellectual-property framework.

This overview explains what each application is, how to tell which one applies to a given product, and the concrete differences a regulatory team should plan around.

The short version

Application	Statutory basis	Applies to	Core evidence
NDA (505(b)(1))	FD&C Act 505(b)	Brand-name small-molecule drug, applicant owns the data	Full reports of safety and effectiveness conducted by/for the applicant 757225
NDA (505(b)(2))	FD&C Act 505(b)	Small-molecule drug relying partly on data the applicant does not own	Full reports, but some information comes from studies not conducted by/for the applicant, plus bridging data 75632579
ANDA (505(j))	FD&C Act 505(j)	Generic copy of an approved drug	Sameness to the reference listed drug plus bioequivalence, not independent efficacy trials 27322528
BLA (351(a))	PHS Act 351(a)	Originator biological product	Full license application demonstrating safety, purity, and potency
BLA (351(k))	PHS Act 351(k)	Biosimilar or interchangeable biologic	Analytical, nonclinical, and clinical data showing biosimilarity to a licensed reference product 11520

Step one: is it a drug or a biological product?

The first fork is statutory classification, not chemistry convenience. FDA asks whether the product meets the definition of a "biological product" in section 351(i) of the Public Health Service (PHS) Act. The Biologics Price Competition and Innovation (BPCI) Act amended that definition to include "protein," and FDA interprets "protein" as any amino acid polymer with a specific, defined sequence greater than 40 amino acids. Amino acid polymers of 40 or fewer amino acids ("peptides") fall outside that term and continue to be regulated as drugs unless they otherwise meet the biological-product definition. A product that contains a protein only as an inactive ingredient is not treated as a "protein" for this purpose. ^103104105

Practically: vaccines, blood and blood components, and cell and gene therapies are biological products handled through a BLA; small synthetic molecules and most peptides at or below the 40-amino-acid threshold run through an NDA or ANDA.

A structural point that still trips up teams is the March 2020 transition. Under a BPCI Act transition provision, on March 23, 2020 approved NDAs for biological products (insulin among them) were "deemed to be" BLAs under section 351 of the PHS Act by operation of statute, with no affirmative action required from the sponsor. From that date, new submissions for those biological products must be filed under section 351 of the PHS Act, and the deemed BLAs became available as reference products for biosimilar and interchangeable applications under section 351(k). ^1041061099 A narrow carve-out applied to applications submitted under section 505, filed no later than March 23, 2019, and not yet approved by March 23, 2020: FDA could keep reviewing them, and if later approved under section 505 before October 1, 2022, they would be deemed a BLA upon approval. ¹⁰⁷¹¹⁰

Step two: original evidence, or reliance on an approved product?

Once you know the drug/biologic axis, the second fork is whether the sponsor is generating its own complete evidence package or leaning on a product FDA already cleared.

Question	Route
Biologic, original product	BLA 351(a)
Biologic, relies on a licensed reference product	BLA 351(k) biosimilar/interchangeable
Drug, novel, sponsor owns all pivotal data	NDA 505(b)(1)
Drug, relies partly on others' data or published literature	NDA 505(b)(2)
Drug, duplicate of an approved product	ANDA 505(j)

The NDA: 505(b)(1) versus 505(b)(2)

An NDA is the pathway for a brand-name drug, and it comes in two flavors that share a form but differ in data ownership.

A 505(b)(1) NDA is the stand-alone application. It contains full reports of investigations of safety and effectiveness that were conducted by or for the applicant, or for which the applicant has a right of reference or use. ⁷⁵⁷²²⁵ Beyond the study reports, an NDA also describes the drug's components, chemical composition, and manufacturing controls, and includes proposed labeling. ⁶¹

A 505(b)(2) NDA is still a full NDA, but at least some of the information required for approval comes from studies not conducted by or for the applicant and for which the applicant has not obtained a right of reference. ^7572257963 That reliance can rest on FDA's prior finding of safety and/or effectiveness for an approved drug, or on published literature. ⁷⁵⁶³⁷⁹ The trade-off is a bridging obligation: the applicant must show the proposed product is sufficiently similar to the relied-upon drug to justify the reliance, and must support any differences with adequate data showing they do not affect safety and effectiveness. ^63257377

Evidence standard. For effectiveness, an original NDA must meet the "substantial evidence" standard: adequate and well-controlled investigations, including clinical investigations, by qualified experts. ⁹⁴ FDA generally derives this from two adequate and well-controlled Phase 3 trials, though in some cases one adequate and well-controlled investigation plus confirmatory evidence can suffice. ^80829299 The content package spans nonclinical studies (nonclinical safety studies generally conducted under GLP), clinical development establishing effectiveness and safety, and CMC/quality information supporting identity, purity, strength, and manufacturing quality under CGMP. ^8480888593

The ANDA: copying an approved drug

An ANDA is an abbreviated application under section 505(j) of the FD&C Act to market a generic drug. It is "abbreviated" precisely because it does not require the same type and extent of information as an NDA. ²⁷³²

To be approved, a generic must show it has the same active ingredient(s), dosage form, route of administration, strength, conditions of use, and (with limited exceptions) labeling as the reference listed drug (RLD), and that it is bioequivalent to the RLD. ²⁵²⁸³² Bioequivalence is generally demonstrated through studies comparing the proposed generic to the RLD. ²⁵ The Reference Listed Drug is the listed drug FDA identifies as the product upon which the ANDA applicant relies, that is, the previously approved product the generic seeks to duplicate. ²⁹³²

The payoff of this framework is substitutability at the pharmacy counter, which FDA encodes in Orange Book therapeutic-equivalence (TE) codes. Approved generics of atorvastatin calcium, for example, are listed as ANDAs (application type "A") and carry an "AB" TE rating that marks them as therapeutically equivalent and substitutable for the brand. ^160161163164 Not every product line carries a rating in every configuration, so TE status should be checked per product rather than assumed. ¹⁶²

The BLA: 351(a) originators and 351(k) biosimilars

A BLA under section 351(a) of the PHS Act is the license for a single biological product. That licensed product becomes the "reference product" against which later applicants are measured. ¹²⁴

A 351(k) application is the abbreviated licensure pathway for a biological product shown to be biosimilar to, or interchangeable with, an FDA-licensed reference product. ¹²¹⁵ It must include data from analytical studies, an assessment of toxicity, and clinical study or studies (including immunogenicity and PK or PD), unless FDA determines a given element is unnecessary. ¹¹⁵²⁰ The substantive bar is that the product is highly similar to the reference product notwithstanding minor differences in clinically inactive components, and that there are no clinically meaningful differences in safety, purity, and potency. ^125152024

Interchangeability is a higher designation layered on top of biosimilarity. An interchangeable product can be expected to produce the same clinical result as the reference product in any given patient, and, for a product administered more than once, to carry no greater risk in terms of safety or diminished efficacy from alternating or switching than using the reference product without switching. ^23679101524 The regulatory consequence is that an interchangeable biosimilar may be substituted for the reference product without the intervention of the prescribing provider. ^{12367910151924}

The originator/biosimilar structure is visible in the Purple Book. Humira (adalimumab) is licensed as a 351(a) reference product under BLA 125057, and its biosimilars, such as Yusimry (adalimumab-aqvh, BLA 761216) and Idacio (adalimumab-aacf, BLA 761255), are listed as 351(k) biosimilars naming Humira as the reference product. ¹⁵⁹ Note the four-letter suffix appended to each biosimilar's proper name, the naming convention that distinguishes biologics from small-molecule generics.

What actually changes between the three

Beyond the evidence package, the choice of application cascades into four areas a regulatory strategy has to account for.

Review center. Drugs are generally reviewed by CDER and biologics by CBER, though the split is not clean along the drug/biologic line. Many therapeutic proteins, including monoclonal antibodies, cytokines, and enzymes, are reviewed by CDER, while CBER handles vaccines, blood and blood-related products, and cell and gene therapies. ^{113115128126129130131132}

Substitutability. An ANDA generic earns an Orange Book TE code (an "AB" rating, for instance) that supports automatic substitution for the brand. ¹⁶⁰¹⁶¹ A biosimilar is substitutable only if FDA has additionally designated it interchangeable, and that substitution turns on the interchangeability standard rather than a TE code. ¹²¹⁵

Intellectual property listing. Small-molecule NDA/ANDA patents and exclusivities live in the Orange Book; licensed biologics and their reference-product exclusivity live in the Purple Book. These are separate systems, and the litigation frameworks differ (Hatch-Waxman paragraph-IV practice for drugs versus the BPCIA "patent dance" for biosimilars).

Marketing exclusivity. The exclusivity clocks differ sharply by pathway:

• A 5-year new chemical entity (NCE) exclusivity attaches when an NDA is approved for a drug whose active moiety has not been previously approved; it runs from the first NDA approval for that active moiety and generally bars FDA from receiving an ANDA or filing a 505(b)(2) for the same active moiety, with an exception permitting submission after 4 years if the applicant certifies patent invalidity or noninfringement. ¹⁴⁶
• A 3-year exclusivity attaches when the active moiety was previously approved but a new clinical investigation (other than bioavailability/bioequivalence studies) was essential to approval. ¹⁴⁶
• 180-day generic exclusivity rewards the first applicant to file a substantially complete ANDA with a paragraph-IV certification, blocking subsequent ANDAs for 180 days, triggered at the earlier of first commercial marketing or a favorable court decision on the patent. ^{38404142444749}
• A 7-year orphan exclusivity can block approval of, or leave tentatively approved, competing applications for the same orphan-designated use. ⁵¹
• For biologics, the BPCI Act sets a 12-year reference-product exclusivity: a 351(k) product may not be licensed until 12 years after the reference product's first licensure, and a 351(k) application may not even be submitted until 4 years after first licensure. ^148150152158

Bottom line for routing

Classify the product first (biologic under PHS Act 351(i) versus drug under the FD&C Act), then decide whether you are generating original evidence or relying on an already-approved product. That two-step determination fixes the application type, and with it the evidence standard, the reviewing center, the substitutability regime, the IP-listing system, and the exclusivity runway. For borderline products (peptides near the 40-amino-acid line, deemed BLAs from the 2020 transition, or a 505(b)(2) versus ANDA decision for a modified formulation) the classification question is worth resolving with FDA early, because it governs everything built downstream.