Definition
505(b)(2) Pathway
The 505(b)(2) pathway is a type of New Drug Application in which the applicant relies, at least in part, on safety and effectiveness data it did not generate and has no right to reference, such as published literature or the FDA's findings for an approved drug.
1 min readReviewed September 14, 2026
Also known as: 505(b)(2) NDA, 505b2, Section 505(b)(2) application, Hybrid NDA
Key facts
- Legal basis
- Section 505(b)(2) of the Federal Food, Drug, and Cosmetic Act
- Created by
- Hatch-Waxman Act of 1984
- Regulations
- 21 CFR 314.54 and 21 CFR Part 314
- Application type
- An NDA, not an ANDA
- Patent obligations
- Certifies to Orange Book patents of the listed drugs it relies on
What is the 505(b)(2) pathway?
Section 505(b) of the FD&C Act covers applications that contain full reports of investigations of safety and effectiveness. A 505(b)(1) application, often called a stand-alone NDA, relies on studies the sponsor conducted or has a right of reference to. A 505(b)(2) application fills part of that evidence from sources the sponsor does not own.
The pathway sits between a full NDA and an Abbreviated New Drug Application (ANDA). The product often differs from an approved drug in a way an ANDA cannot cover, so the sponsor runs bridging studies that connect its product to the existing evidence instead of repeating a full development program.
Common uses of 505(b)(2)
Typical 505(b)(2) products include:
- New dosage forms, such as an extended-release version or a ready-to-use injectable of an approved drug.
- New strengths, routes of administration or dosing regimens.
- New combinations of previously approved active ingredients.
- A different salt, ester or complex of an approved active moiety.
- New indications for an approved drug, supported partly by published literature.
Why the 505(b)(2) pathway matters
These products blur the brand vs generic split in pricing and competition data. A 505(b)(2) product is legally an NDA drug and is often branded and priced at a premium, even when its active ingredient is already sold as a low-cost generic. Market sizing that groups products by active ingredient alone can misread that competition.
The pathway also carries Hatch-Waxman obligations and rewards. The applicant must certify to patents listed in the Orange Book for the drugs it relies on, a Paragraph IV certification can trigger a 30-month stay, and an approval backed by new clinical investigations can earn 3-year exclusivity. Some 505(b)(2) products are rated therapeutically equivalent to other products and carry a TE code.