Every prescription and over-the-counter drug your veterinary practice dispenses went through the same regulatory gateway: a New Animal Drug Application (NADA) reviewed and approved by the FDA's Center for Veterinary Medicine (CVM). The process is structurally parallel to the human drug approval pathway — same evidence standards, same manufacturing requirements, same dossier format — but scaled to the realities of animal health markets.

This article covers how that pathway works, how long it takes, what it costs, and why understanding it matters for the drugs you prescribe every day.

The short answer

A new animal drug cannot be legally sold in the United States unless it is the subject of an approved NADA (or an Abbreviated NADA for generics, or a conditionally approved NADA). The drug sponsor — typically a pharmaceutical company — must demonstrate three things to the CVM: that the drug is safe for the target animal (and for humans, if the animal enters the food supply), that it is effective for its labeled indication, and that it can be manufactured consistently. The process from initial development to market approval typically takes 5 to 10 years and can cost $5 to $10 million or more for a single new molecular entity in a major species.

Why this matters to practicing veterinarians

You do not need to understand the NADA process to prescribe a drug. But the regulatory pathway shapes what information ends up on the label — and what does not.

When Numelvi (atinvicitinib) was approved on February 25, 2026, its label specified dosing for dogs six months and older with allergic dermatitis. The field safety data extended to 28 days. That 28-day window was not arbitrary — it reflects the duration of the pivotal effectiveness and safety studies the sponsor was required to submit under the NADA. When a client asks why the label does not cover long-term use, the answer traces back to what the NADA contained at the time of approval.

Understanding the approval process also helps you evaluate off-label use, assess new drug launches, and explain to clients why a drug they read about online may not yet be available in the United States.

Which federal agency regulates what

Three agencies share oversight of animal health products in the United States:

• FDA CVM regulates animal drugs, medicated feeds, and animal medical devices. Most pharmaceutical products go through the NADA pathway.
• USDA Center for Veterinary Biologics (CVB) regulates veterinary biologics — vaccines, diagnostic test kits, and immunobiologics.
• EPA regulates topical pesticide products, including many flea and tick spot-on treatments and environmental parasiticides.

The distinction is based on mechanism of action. If the product works through chemical action in or on the body, FDA regulates it. If it works by stimulating the immune system, USDA regulates it. If it works by killing or repelling external parasites through a pesticidal mechanism, EPA regulates it.

The NADA pathway: step by step

1. Pre-INAD consultation (optional)

Before formal development begins, a sponsor may request informal discussions with CVM to explore the regulatory pathway for a novel product. For innovative technologies — such as stem cell therapies or gene-edited biologics — CVM may form a dedicated technical team to identify knowledge gaps and review strategies. This pre-submission phase can begin two or more years before a formal INAD file is opened.

2. Opening the INAD file

The Investigational New Animal Drug (INAD) file is the regulatory container under which all development studies are conducted. Regulations are in 21 CFR Part 511. Once the INAD is opened, the sponsor can ship the investigational drug across state lines for clinical trials — something that would otherwise be illegal under the Federal Food, Drug, and Cosmetic Act.

CVM recommends a phased review process, in which the sponsor submits data for each technical section as it is completed, rather than submitting the entire NADA at once. This allows CVM to review and approve individual components incrementally, with greater interaction between sponsor and reviewers.

3. Drug development: pilot and pivotal studies

The development phase is where the core evidence is generated. CVM does not use the Phase I / II / III terminology familiar from human drug development. Instead, veterinary drug development typically involves:

• Pilot studies — smaller-scale studies in the target species to establish dose, bioavailability, and preliminary safety and effectiveness data.
• Pivotal studies — larger, well-controlled clinical trials (often several hundred animals for a major species) that provide the "substantial evidence of effectiveness" required for NADA approval.

Unlike human drug development, where Phase III typically requires two large trials involving thousands of patients and carries a significant risk of failure, veterinary pivotal studies are generally smaller and have a higher probability of success once positive pilot data are in hand.

4. The four technical sections of a NADA

A complete NADA must address four core technical sections:

1. Target Animal Safety (TAS). The sponsor must demonstrate that the drug is safe when used as directed in the target species. This includes safety margin studies — typically administering the drug at one, three, and five times the labeled dose to characterize the dose-response relationship and identify adverse effects.

2. Effectiveness. The sponsor must provide substantial evidence that the drug does what the label claims. This comes from the pivotal field trials. The evidence must support each labeled indication, dose, and duration of use.

3. Chemistry, Manufacturing, and Controls (CMC). The manufacturing section must demonstrate that the drug can be produced consistently, with documented quality, purity, potency, and stability. These requirements are held to the same Good Manufacturing Practice (GMP) standards as human pharmaceutical products.

4. Environmental Assessment (EA). The sponsor must assess the environmental impact of the drug's manufacture, use, and disposal. In many cases, the sponsor can submit a claim of categorical exclusion if the drug is not expected to have a significant environmental effect.

For food-producing animals, two additional sections are required:

• Human Food Safety. Toxicology, residue chemistry, and microbial food safety data to ensure that edible tissues from treated animals are safe for human consumption. This section defines the acceptable daily intake (ADI), tolerance levels, and withdrawal periods.
• Regulatory Method. A validated analytical method for detecting drug residues in food products.

5. Phased review and presubmission conference

Under the phased review process, CVM reviews each technical section as the sponsor completes it. Once all sections have received "Technical Section Complete" letters, the sponsor requests a presubmission conference — a formal meeting to confirm that the NADA package is complete and ready for filing.

6. Administrative NADA filing and approval

If the phased review pathway was followed, the sponsor files an administrative NADA. CVM reviews the complete package within approximately 60 days. If the review team and the Director of CVM agree that the drug is safe and effective when used as labeled, the NADA is approved and a notice is published in the Federal Register.

If the traditional (non-phased) pathway was used, the review clock can be considerably longer — historically ranging from several months to over a year.

Three types of animal drug applications

CVM recognizes three application types:

Conditional approval (CNADA)

Conditional approval is a veterinary-specific pathway with no direct equivalent in human drug regulation. Under the Minor Use/Minor Species (MUMS) Act of 2004, a sponsor can receive conditional approval if the drug meets all safety and manufacturing requirements but has not yet demonstrated "substantial evidence of effectiveness." The sponsor must show a "reasonable expectation of effectiveness" and can market the drug for up to five years (with annual renewals) while collecting the effectiveness data needed for full approval.

This pathway is relevant to several products currently in development. Gallant's stem cell therapy for refractory feline chronic gingivostomatitis (FCGS) is on track for conditional approval in 2026, which would make it the first FDA-labeled allogeneic stem cell therapy in veterinary medicine. In May 2026, Gallant also announced that its canine osteoarthritis stem cell therapy program received expanded conditional approval pathway eligibility from CVM.

Timeline and cost

Industry estimates put the total development timeline for a new veterinary drug at 5 to 10 years from discovery to approval, with costs ranging from $5 million to over $10 million for a single product in a major species. The product development phase alone (pilot and pivotal studies) typically takes 2 to 4 years.

These numbers are modest compared to human drug development — where a single Phase III trial can cost hundreds of millions — but the veterinary market is also much smaller, which means the return-on-investment bar is higher per dollar spent. This economic reality is part of why conditional approval and the MUMS pathway exist: they reduce the upfront evidence burden for products targeting smaller patient populations.

Recent approvals illustrate the process

The FDA's recent animal drug approvals page shows the diversity of products moving through the NADA and ANADA pathways in 2026:

• Numelvi (atinvicitinib tablets) — approved February 25, 2026 for control of pruritus associated with allergic dermatitis in dogs. A new molecular entity (second-generation JAK1 inhibitor) from Intervet (Merck Animal Health).
• Bravecto Quantum (fluralaner injectable) — supplemental NADA approved March 16, 2026 adding Asian longhorned tick and Gulf Coast tick indications for 12-month duration in dogs.
• Gastrobim (omeprazole) — ANADA approved April 6, 2026; first generic omeprazole oral paste for treatment and prevention of gastric ulcers in horses and foals.
• Robenacoxib Injection — ANADA approved March 9, 2026; first generic robenacoxib for postoperative pain control in dogs and cats.
• ANIRANE (isoflurane) — ANADA approved February 23, 2026 for induction and maintenance of general anesthesia in horses and dogs.

Each of these approvals has a publicly available Freedom of Information (FOI) Summary — a document that summarizes FDA's basis for approval. FOI summaries are useful for veterinarians who want to understand the evidence behind a drug's labeled claims.

How the veterinary pathway parallels human drug approval

The veterinary NADA process is built on the same structural framework as the human New Drug Application (NDA) process overseen by FDA's Center for Drug Evaluation and Research (CDER). Both require:

• Preclinical safety testing
• Controlled clinical trials demonstrating safety and effectiveness
• Manufacturing under GMP conditions
• Submission in the Common Technical Document (CTD) format, organized into the same five modules (administrative, quality, nonclinical, clinical, and regional information)

The key differences are scale (veterinary trials involve hundreds of animals, not thousands of human patients), the conditional approval pathway unique to animal health, and the human food safety requirements for drugs used in food-producing species.

For professionals who work across both the human and animal health regulatory landscapes — for example, a pharmaceutical company expanding from human into veterinary markets, or a regulatory affairs consultant navigating both pathways — understanding the parallels and divergences is essential. The CTD and eCTD submission guidance at PharmaDossier covers the Common Technical Document framework that both human and veterinary drug applications use, including module structure, regional variations, and submission logistics that apply to either pathway.

What changes after approval

Post-approval, the drug sponsor must comply with ongoing requirements:

• Adverse event reporting. Sponsors must report adverse drug experiences to CVM. Increased frequency of known or unexpected serious adverse events triggers additional reporting obligations.
• Supplemental NADAs. Any change to the approved labeling, manufacturing process, or formulation requires a supplemental application. Changes that could affect safety or effectiveness require a "Prior Approval Supplement" — the sponsor cannot distribute the modified product until CVM approves the supplement.
• Periodic updates. Label updates may be required as new safety information emerges. The FDA's isoxazoline flea and tick product fact sheet, for example, was issued after post-market surveillance identified neurologic adverse events that were not fully characterized at the time of initial approval.

How to look up a drug's approval history

Two public resources are particularly useful:

1. Animal Drugs @ FDA (the "Green Book") — a searchable database of all approved animal drugs, including NADA numbers, sponsors, approval dates, and product listings.
2. FDA Recent Animal Drug Approvals — lists newly approved NADAs with links to FOI Summaries, which describe the safety and effectiveness data that supported approval.

For a drug you prescribe regularly, reading the FOI Summary can provide context the label does not — including the study design, number of animals treated, and the specific endpoints that were evaluated.

What this means for drug selection in practice

The NADA process is designed to ensure that every approved veterinary drug meets defined standards for safety, effectiveness, and manufacturing quality. But "approved" does not mean "completely characterized." The label reflects what the sponsor demonstrated in the pivotal studies submitted to CVM — not necessarily everything a clinician needs to know for every patient.

When evaluating a newly approved drug:

• Check the FOI Summary for the scope of the field trials (species, age, comorbidities, study duration).
• Note what was not studied — concurrent medications, specific populations, long-term use beyond the pivotal trial window.
• Monitor post-market adverse event data, which may expand or refine the safety profile over time.
• Compare the labeled indications and contraindications against your patient population, not just against competitor products.

The regulatory pathway tells you the floor — the minimum evidence standard a drug met to reach the market. Your clinical judgment determines whether it is the right fit for the patient in front of you.

Sources

• FDA. "New Animal Drug Applications." U.S. Food and Drug Administration. https://www.fda.gov/animal-veterinary/development-approval-process/new-animal-drug-applications
• FDA. "Recent Animal Drug Approvals." U.S. Food and Drug Administration. https://www.fda.gov/animal-veterinary/approved-animal-drug-products-green-book/recent-animal-drug-approvals
• FDA. "How to Get a New Animal Drug Approved and First Steps to Get Started." U.S. Food and Drug Administration. https://www.fda.gov/animal-veterinary/resources-you/how-get-new-animal-drug-approved-and-first-steps-get-started
• FDA. "Development & Approval Process." U.S. Food and Drug Administration. https://www.fda.gov/animal-veterinary/development-approval-process
• FDA. "FDA's Role in Veterinary Regenerative Medicine." U.S. Food and Drug Administration. https://www.fda.gov/animal-veterinary/cell-and-tissue-products-animals/fdas-role-veterinary-regenerative-medicine
• Anivive Lifesciences. "From Test Tube to Prescription: What Does It Take to Get a Drug Approved?" https://www.anivive.com/learn/article/from-test-tube-to-prescription-what-does-it-take-to-get-a-drug-approved
• DS Inpharmatics. "From INAD to NADA: Mapping the Veterinary Drug Approval Lifecycle." https://dsinpharmatics.com/from-inad-to-nada-mapping-the-veterinary-drug-approval-lifecycle
• Dawnbreaker MRR. "Animal Drug Approval Process." https://mrr.dawnbreaker.com/portals/medical/veterinary-products/animal-drug-approval-process
• eCFR. "21 CFR Part 514 — New Animal Drug Applications." https://www.ecfr.gov/current/title-21/chapter-I/subchapter-E/part-514
• Gallant. "Gallant Advances Canine Osteoarthritis IV-Delivered Stem Cell Therapy." PR Newswire, May 6, 2026. https://www.prnewswire.com/news-releases/gallant-advances-canine-osteoarthritis-iv-delivered-stem-cell-therapy-with-promising-pilot-data-and-expanded-fda-conditional-approval-pathway-eligibility-302763756.html