Clinical trial phases, New Drug Applications, and Biologics License Applications all get discussed on this site, but there's an earlier, easily overlooked regulatory step that has to happen before any of them: the Investigational New Drug application, or IND.

What an IND Application Is

An IND is the application a drug sponsor, usually a pharmaceutical or biotech company, files with the FDA to get permission to begin testing an experimental drug in human subjects. Before an IND is in effect, a drug can only be studied in laboratory and animal (preclinical) settings. The IND is what legally allows Phase 1 human trials to begin.

What Goes Into One

An IND application includes the preclinical data gathered so far, covering pharmacology and toxicology findings from laboratory and animal studies, information about how the drug is manufactured and its chemical composition, and the detailed protocol for the proposed clinical trial, including how patient safety will be monitored. For a peptide drug, this typically includes additional detail on the synthesis or manufacturing process, since peptides can be produced either through chemical synthesis or through recombinant biological methods, each carrying its own manufacturing and purity considerations.

The 30-Day Review Clock

Once an IND is submitted, the FDA has 30 days to review it before the sponsor can begin the proposed trial. If the agency has significant safety concerns, it can place the trial on clinical hold, requiring the sponsor to address those concerns before proceeding. If no hold is issued within that window, the sponsor may begin the trial.

How This Differs From an NDA

A New Drug Application (NDA) is filed years later, after a drug has completed Phase 1, 2, and 3 trials, and is the formal request for FDA marketing approval. Where an IND is a request for permission to study a drug, an NDA is a request for permission to sell it, built on the complete body of evidence the IND-authorized trials generated.

How This Differs From a BLA

A Biologics License Application (BLA), covered in more detail in this site's dedicated BLA explainer, serves the same ultimate purpose as an NDA, seeking marketing approval, but is used for products regulated as biologics under the Public Health Service Act rather than as drugs under the Food, Drug, and Cosmetic Act. Historically, this distinction mattered for peptides in a specific way: smaller, chemically synthesized peptides were typically regulated as drugs and filed NDAs, while larger, more complex peptides and proteins produced through biological processes were typically regulated as biologics and filed BLAs. That line has shifted somewhat; as of March 2020, insulin and several other previously NDA-approved peptide and protein products were formally transitioned to being regulated as biologics, now governed by BLAs instead. Which pathway applies to any specific drug today depends on its particular regulatory history and classification, not simply its size.

The Bottom Line

An IND is the application that starts the clock on human testing, while an NDA or BLA is the application that, years and often billions of dollars later, asks the FDA to let a drug reach patients. Every FDA-approved peptide drug discussed on this site, from older ones like octreotide to newer ones like orforglipron, passed through an IND long before anyone outside its trials ever heard its name.