FDA Drug Approval Process Explained

Three researchers in white lab coats talk around a bare steel bench in a bright laboratory — Researchers discuss work in a laboratory.

According to FDA, a new drug goes through five steps: discovery and development, preclinical research in the lab and in animals, clinical research in people, FDA review, and post-market safety monitoring.[1] FDA does not test the drug itself; FDA reviewers evaluate the results of the company's laboratory, animal and human testing.[2][3]

Five Steps at a Glance

Step	What happens
Discovery and development	Research for a new drug begins in the laboratory.
Preclinical research	Laboratory and animal testing for serious harm (toxicity).
Clinical research	Trials in people, usually Phases 1 to 3.
FDA review	FDA reviews the NDA and decides whether to approve.
FDA post-market safety monitoring	FDA reviews problem reports and can add cautions.

Sources: [1][4][5][6][7]

What Approval Means

With rare exceptions, a new drug must be FDA-approved before it can be sold, and the company must show FDA that the drug is safe and effective for its intended use.[2][8]

According to FDA, approval means the agency has determined that a drug's benefits outweigh its risks for the intended use.[2]

FDA's approval decision is made for a drug's intended use and population; for other uses, FDA says it has not determined that the drug is safe and effective.[3][8]

FDA says "safe" does not mean a drug has no side effects; it means FDA has determined that the benefits of using the drug for a particular use outweigh the potential risks.[8]

Before Testing in People

Before a drug is tested in people, researchers run laboratory and animal studies to find out whether it could cause serious harm, which FDA calls toxicity.[4][1]

FDA requires preclinical laboratory studies to follow Good Laboratory Practice rules, which are set out in 21 CFR Part 58.[4]

Before clinical trials in people can begin, the drug's sponsor must submit an Investigational New Drug (IND) application to FDA.[5]

An IND application includes animal and toxicity data, manufacturing information, the plans for the clinical studies, any earlier human research data, and information about the investigator.[5]

Under federal regulations, an IND goes into effect 30 days after FDA receives it, unless FDA places the studies on clinical hold, or sooner if FDA tells the sponsor the studies may begin.[9]

FDA says a clinical hold is rare and that the agency often gives comments to improve the quality of a clinical trial instead.[5]

Clinical Trial Phases

FDA describes Phase 1 trials as studies of 20 to 100 healthy volunteers or people with the condition, lasting several months, that look at safety and dosage.[5]

FDA describes Phase 2 trials as studies of up to several hundred people with the condition, lasting several months to 2 years, that look at effectiveness and side effects.[5]

According to FDA, Phase 2 studies are not large enough to show whether a drug will be beneficial.[5]

FDA describes Phase 3 trials as studies of 300 to 3,000 people with the condition, lasting 1 to 4 years, that test effectiveness and watch for adverse reactions.[5]

Because Phase 3 studies are larger and longer, FDA says they are more likely to show long-term or rare side effects.[5]

FDA describes Phase 4 trials as studies of several thousand people with the condition, carried out after FDA approval, that look at safety and effectiveness.[5]

Stage	Who takes part	How long	Main purpose	Share that moves on (estimate)
Phase 1	20 to 100 healthy volunteers or people with the condition	Several months	Safety and dosage	About 70% (FDA estimate)
Phase 2	Up to several hundred people with the condition	Several months to 2 years	Effectiveness and side effects	About 33% (FDA estimate)
Phase 3	300 to 3,000 people with the condition	1 to 4 years	Effectiveness and monitoring of adverse reactions	About 25% to 30% (FDA estimate)
Phase 4 (after approval)	Several thousand people with the condition	Not reported	Safety and effectiveness, after FDA approval	Not reported

FDA's patient page on clinical research estimates that about 70% of drugs move on after Phase 1, about 33% move on after Phase 2, and about 25% to 30% move on after Phase 3.[5] We found no overall drug approval rate in the FDA sources reviewed for this page; FDA's patient page gives an estimate for each phase separately.

Sources: [5]

We found no FDA figure for the total time it takes to develop and approve a new drug in the FDA sources reviewed for this page.[5]

FDA generally expects a drug maker to submit results from two well-designed clinical trials, so that the first trial's findings are not the result of chance or bias.[3]

In some cases, especially for rare diseases where several trials may not be feasible, FDA says convincing evidence from one clinical trial may be enough.[3]

The FDA Review

To ask for approval, the drug maker files a New Drug Application (NDA), which FDA says "tells the full story of a drug."[6]

An NDA includes reports on all studies, data and analyses, along with proposed labeling, safety updates, drug abuse information, patent information and directions for use.[6]

If an NDA is incomplete, FDA's review team can refuse to file it.[6]

If an NDA is complete, FDA's patient page says the review team has 6 to 10 months to decide whether to approve the drug.[6]

Under Priority Review, FDA aims to act on an application within 6 months, compared with 10 months under standard review.[3]

A team of FDA physicians, statisticians, chemists, pharmacologists and other scientists reviews the company's data and proposed labeling.[3]

During an NDA review, FDA inspectors visit clinical study sites and look for evidence that data were fabricated, manipulated or withheld.[6]

FDA's review team issues a recommendation, and a senior FDA official makes the decision.[6]

When questions need more consideration, FDA may hold an Advisory Committee meeting to get independent expert advice and to allow the public to comment.[6]

FDA weighs a drug's risks against how serious the condition is and what other treatments exist, so risks that are acceptable for a life-threatening disease with no other therapy may be unacceptable for a condition that is not life-threatening.[3]

Before approval, FDA sometimes requires the developer to answer questions using existing data, and in other cases requires additional studies.[6]

A developer that disagrees with an FDA decision has formal ways to appeal.[6]

When FDA finds that a drug has been shown to be safe and effective for its intended use, FDA works with the company on the prescribing information, called labeling, which describes the basis for approval and how best to use the drug.[6]

FDA says the drug label describes the drug's benefits and risks, and how the risks can be detected and managed.[3]

Faster Pathways

Accelerated Approval lets FDA approve a drug for a serious or life-threatening condition based on its effect on a surrogate endpoint, a measure that is reasonably likely to predict real clinical benefit.[3] After an Accelerated Approval, the drug maker must run further trials to verify the drug's benefit, and FDA may withdraw approval if those trials fail to verify it.[3]

Here is a real example. Wegovy (semaglutide) injection, given under the skin, is FDA-approved, with a reduced-calorie diet and more physical activity, for noncirrhotic MASH with moderate to advanced liver fibrosis (stages F2 to F3) in adults under FDA's accelerated approval program, based on improvement of MASH and fibrosis. Continued approval may depend on a confirmatory trial.

Regulatory status checked September 27, 2026. Sources: www.accessdata.fda.gov/…/209637s038lbl.pdf; www.accessdata.fda.gov/…/213051Orig1s030lbl.pdf; www.accessdata.fda.gov/…/215256s025lbl.pdf; www.fda.gov/…/fda-clarifies-policies-compounders-national-glp-1-supply-begins-stabilize; public-inspection.federalregister.gov/…/2026-12937.pdf; www.fda.gov/…/fda-proposes-exclude-semaglutide-tirzepatide-and-liraglutide-503b-bulks-list; www.fda.gov/…/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss; www.fda.gov/…/compounding-and-fda-questions-and-answers; www.accessdata.fda.gov/…/218316Orig1s000ltr.pdf; www.accessdata.fda.gov/…/218316s007lbl.pdf

Fast Track is an FDA process meant to speed the development and review of drugs that treat serious conditions and fill an unmet medical need, and the drug company must request it.[3]

Breakthrough Therapy designation speeds the development and review of drugs for serious conditions when early clinical evidence shows the drug may offer substantial improvement over available therapy.[3]

Pathway	What it does
Priority Review	FDA aims to act within 6 months (priority) vs 10 months (standard).
Accelerated Approval	Approval based on a surrogate endpoint reasonably likely to predict benefit, for serious conditions. Follow-up trials required; FDA may withdraw approval if benefit is not verified.
Fast Track	Speeds development and review for serious conditions with an unmet need; company must request it.
Breakthrough Therapy	Speeds development and review when early evidence suggests substantial improvement.

Sources: [3]

After Approval

FDA says it is impossible to have complete information about a drug's safety at the time of approval, so the agency keeps reviewing reports of problems after the drug is on the market.[7]

After approval, FDA can add cautions to a drug's dosage or usage information, and can take other measures for more serious safety issues.[7]

FDA says significant changes to an approved drug's formulation, labeling or dosage strength generally must be approved by FDA before the company can make them.[7]

A company that wants to study an approved drug for a new use, a new dosage strength or a new form does so under an Investigational New Drug application.[7]

By law, a drug developer may not advertise uses of its product that FDA has not approved.[7]

FDA inspects drug manufacturing facilities, sometimes without advance notice, and can shut down a facility that does not meet minimum standards.[7]

Generic drug makers do not have to repeat clinical trials; instead, they run bioequivalence studies and file an Abbreviated New Drug Application with FDA.[7]

FDA's MedWatch program is a gateway for reporting problems with drugs and medical devices.[7]

References

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Last updated September 28, 2026.

This page is for general education. It is not medical advice and does not replace a licensed clinician who knows your health history.