505(b)(2) Pathway
The 505(b)(2) pathway is a new drug application that leans on data the applicant did not generate, allowing a modified version of a known drug to be approved without repeating the full programme.
Section 505(b)(2) of the Federal Food, Drug, and Cosmetic Act allows a full new drug application in which part of the required safety and effectiveness evidence comes from work the applicant neither performed nor owns: published literature, or FDA's own prior finding for an already approved drug. The applicant supplies only the studies that bridge the difference, typically a new route, strength, salt, dosage form or indication.
It remains a full NDA and carries an NDA's obligations. Patent certifications against the referenced product are required, a paragraph IV certification can trigger the same thirty-month stay a generic filing does, and the product can earn exclusivity of its own: three years for the new clinical investigations, and the longer new chemical entity term where a new active moiety is involved. Peptide products reformulated as autoinjectors, ready-to-use solutions or alternative routes are routine 505(b)(2) territory.
The pathway explains why two products containing the same peptide are not automatically substitutable. A 505(b)(2) product is approved on its own merits and is not necessarily rated therapeutically equivalent to the drug it referenced, so a pharmacist cannot swap them the way a generic is swapped. The therapeutic equivalence code in the Orange Book, not the ingredient name, settles that question.
The common confusion is with the abbreviated pathway. A 505(b)(2) product is not a generic, does not gain approval merely by showing bioequivalence, and its sponsor ran clinical work. Marketing that calls such a product a generic, and criticism that dismisses it as a mere copy, misstate the evidence behind it in opposite directions.