The FDA’s regulatory pathways sort products into three families, with a distinct route for each. Drugs move through a New Drug Application, an Abbreviated New Drug Application for generics, or a hybrid 505(b)(2) filing. Biologics use a Biologics License Application or the abbreviated 351(k) biosimilar route. Medical devices follow 510(k) premarket notification, Premarket Approval, or the De Novo classification request. Which route fits depends on what the product is, how novel it is, and how much risk it carries. Layered on top are expedited designations for serious conditions and, in a declared emergency, the Emergency Use Authorization.
Pathways for Drugs
Drug applications live in 21 CFR Part 314.1eCFR. 21 CFR Part 314 – Applications for FDA Approval to Market a New Drug The three options differ in how much of the safety and effectiveness case the applicant has to build from scratch.
New Drug Application
A New Drug Application (NDA) is the full submission for a novel chemical entity. It carries the complete results of Phase 1 through Phase 3 trials, detailed pharmacology data, and a full description of the manufacturing process. The applicant bears the entire burden of proving safety and effectiveness. It is the most expensive and time-consuming route, and the only option when no comparable product has been approved.
Abbreviated New Drug Application
Generic versions of approved drugs use the Abbreviated New Drug Application (ANDA). Rather than repeat clinical trials, the generic sponsor proves bioequivalence: the same amount of active ingredient delivered at the same rate as the brand-name product. The original drug’s safety and efficacy record does the heavy lifting.
The 505(b)(2) Application
The 505(b)(2) route sits between the two. It is still technically an NDA, but the applicant can rely on data it did not generate and does not own, such as published literature or the FDA’s prior findings for a related product.2Food and Drug Administration. Applications Covered by Section 505(b)(2) It is a common fit when a manufacturer modifies an existing drug’s dosage form, strength, or route of administration. New data is still required for the specific change, but the full clinical development program does not have to be reproduced.
Pathways for Biological Products
Biologics come from living organisms rather than chemical synthesis. Vaccines, blood products, gene therapies, and monoclonal antibodies all fall in this category, and manufacturing consistency matters as much as clinical performance.
Biologics License Application
A Biologics License Application (BLA) under Section 351(a) of the Public Health Service Act is the primary route for a novel biologic. The statute bars introducing a biological product into interstate commerce unless a biologics license is in effect.3Office of the Law Revision Counsel. 42 USC 262 – Regulation of Biological Products Because small changes in temperature, contamination, or cell culture conditions can shift a biologic’s potency, the FDA inspects manufacturing facilities as part of BLA review. Proving that a production site can turn out batch after batch with identical characteristics is often the hardest part of the process.
The 351(k) Biosimilar Route
Section 351(k) created an abbreviated pathway for biosimilars: biological products shown to be highly similar to an already-licensed reference product with no clinically meaningful differences. The sponsor submits analytical studies demonstrating high similarity, a toxicity assessment, and clinical studies covering immunogenicity, pharmacokinetics, and pharmacodynamics. The biosimilar must use the same route of administration, dosage form, and strength as the reference product.4Office of the Law Revision Counsel. 42 USC 262 – Regulation of Biological Products
A biosimilar sponsor can go further and seek an interchangeability designation. That requires showing the biosimilar produces the same clinical result as the reference product in any given patient and that switching between the two carries no added risk. Interchangeability matters at the pharmacy counter, because it determines whether a pharmacist can substitute the biosimilar without calling the prescriber.
Pathways for Medical Devices
Device expectations scale with risk. Three pathways handle almost every submission.
510(k) Premarket Notification
The 510(k) is the workhorse for moderate-risk devices. The manufacturer demonstrates that its device is substantially equivalent to a legally marketed predicate device in both intended use and technological characteristics.5Food and Drug Administration. Premarket Notification 510(k) If the FDA agrees, the device is cleared for sale. Independent clinical trial data is not required in most cases; the predicate comparison carries the argument. The pathway is faster and cheaper, but only available when a sufficiently similar product already exists.
Premarket Approval
High-risk devices, typically Class III products such as pacemakers and replacement heart valves, must go through Premarket Approval (PMA). PMA demands independent evidence of safety and effectiveness: clinical data from human studies, adverse reaction data, statistical analyses, a benefit-risk showing, and a full description of the manufacturing process.6eCFR. 21 CFR Part 814 – Premarket Approval of Medical Devices There is no predicate comparison. The device stands on its own clinical record.
De Novo Classification
Some novel devices pose low-to-moderate risk but have no predicate, which shuts them out of the 510(k) route. The De Novo pathway lets the manufacturer ask the FDA to classify the device as Class I or Class II rather than defaulting to Class III. The submission has to explain why general controls, or general and special controls together, give reasonable assurance of safety and effectiveness. A sponsor can file a De Novo request directly when no suitable predicate exists, or after receiving a “not substantially equivalent” decision on a 510(k).7Food and Drug Administration. De Novo Classification Request Once granted, the device itself becomes a predicate future 510(k) applicants can reference.
What Has to Happen Before You File
Every drug and biologic pathway assumes clinical data already exists. Building that data starts with pre-clinical work in the lab and in animals, then moves to an Investigational New Drug (IND) application under 21 CFR Part 312 before any human dosing.8eCFR. 21 CFR Part 312 – Investigational New Drug Application The IND covers animal pharmacology and toxicology, manufacturing information, and clinical protocols for the human trials.9Food and Drug Administration. Investigational New Drug (IND) Application
Devices take a parallel step. An approved Investigational Device Exemption (IDE) under 21 CFR Part 812 lets a sponsor ship an unapproved device for clinical investigation. Significant-risk device studies need both FDA and institutional review board approval before enrollment.10Food and Drug Administration. Investigational Device Exemption (IDE)
Once the IND takes effect, human testing runs in three phases. Phase 1 typically enrolls 20 to 80 healthy volunteers (or patients, for cancer drugs), aims at safe dosage ranges and acute side effects, and runs several months. Phase 2 expands to as many as several hundred patients who have the target condition, gathering preliminary effectiveness data along with more safety information, over several months to two years. Phase 3 enrolls 300 to 3,000 patients over one to four years and produces the bulk of the safety and efficacy evidence the marketing application relies on.11Food and Drug Administration. Step 3: Clinical Research The FDA can place a clinical hold at any phase if safety concerns emerge, and some expedited programs compress or overlap phases.
Faster Routes for Serious Conditions
Four programs can shorten development and review for drugs treating serious or life-threatening conditions. These are designations that modify how a standard NDA or BLA proceeds, not separate pathways.
- Fast Track applies to drugs treating a serious condition and filling an unmet medical need. It enables more frequent FDA meetings and the possibility of rolling review, where sections of the application are submitted and reviewed as completed.12Food and Drug Administration. Fast Track, Breakthrough Therapy, Accelerated Approval, Priority Review
- Breakthrough Therapy is for drugs that may offer substantial improvement over existing treatments. It provides everything Fast Track offers, plus intensive FDA guidance on efficient trial design starting as early as Phase 1.
- Accelerated Approval allows approval based on a surrogate endpoint reasonably likely to predict a real clinical benefit, rather than waiting for the final outcome. The sponsor must run confirmatory trials after approval; if those fail to verify the benefit, the FDA can withdraw the product.13Food and Drug Administration. Table of Surrogate Endpoints That Were the Basis of Drug Approval or Licensure
- Priority Review sets the FDA’s review goal at six months from filing instead of the standard ten. It does not change the evidentiary requirements; it compresses the agency’s internal timeline.14Food and Drug Administration. Priority Review
These designations can stack. A drug can hold both Fast Track and Breakthrough Therapy designations during development, then get Priority Review when the application is filed.
Emergency Use Authorization
When a public health emergency is declared and no adequate approved alternatives exist, the FDA can issue an Emergency Use Authorization (EUA) under Section 564 of the FD&C Act. A EUA permits use of unapproved products, or unapproved uses of approved products, to diagnose, treat, or prevent serious or life-threatening conditions caused by chemical, biological, radiological, or nuclear threats.15Food and Drug Administration. Emergency Use Authorization The evidence bar is lower than full approval: the FDA must conclude that known and potential benefits outweigh known and potential risks based on the best available evidence. A EUA is temporary. When the emergency declaration ends, the authorization expires unless the product has secured full approval through the standard pathway.
User Fees and Review Timelines
Every marketing application carries a user fee. For drugs, the Prescription Drug User Fee Act sets the rates. In FY 2026, an NDA requiring clinical data carries a fee of $4,682,003.16Food and Drug Administration. Prescription Drug User Fee Amendments Device fees under MDUFA are lower but still substantial: a standard 510(k) costs $26,067, a De Novo request costs $173,782, and a PMA runs $579,272.17U.S. Food and Drug Administration. Medical Device User Fee Amendments (MDUFA) Fees
Small businesses can qualify for reductions. Companies with gross receipts of $100 million or less are eligible for reduced device fees across most submission types. Businesses with gross receipts of $30 million or less may receive a full waiver of the fee on their first PMA or BLA.
The FDA’s target review period for a standard NDA is ten months from the filing date. Priority Review applications get a six-month goal. During review, the agency may request additional information. If the application is not ready for approval at the end of the cycle, the FDA issues a Complete Response Letter identifying the deficiencies the applicant must address before resubmitting.18Food and Drug Administration. Complete Response Letter Final Rule
Approval Is Not the End
Every pathway comes with obligations that follow the product into the market. Drug and biologic sponsors must report serious and unexpected adverse events within 15 calendar days, with routine reporting quarterly for the first three years after approval and annually after that.19eCFR. 21 CFR 314.80 – Postmarketing Reporting of Adverse Drug Experiences Device manufacturers have parallel obligations under 21 CFR Part 803. The FDA can require a Risk Evaluation and Mitigation Strategy for drugs with serious safety concerns, and it can require Phase 4 studies to gather long-term data, especially when approval came under the accelerated pathway on a surrogate endpoint.20Food and Drug Administration. Risk Evaluation and Mitigation Strategies | REMS Picking a pathway means accepting its post-market shape as well as its route to approval.