GLP stands for Good Laboratory Practice, a set of regulations that govern how nonclinical safety studies are planned, performed, monitored, recorded, and reported. In the pharmaceutical industry, GLP exists for one core reason: to ensure that the safety data submitted to regulatory agencies is reliable, reproducible, and trustworthy. Before any new drug reaches human clinical trials, it must first be tested in laboratory and animal studies, and GLP is the quality framework that makes those results credible.
What GLP Actually Regulates
GLP applies specifically to nonclinical laboratory studies, meaning the safety testing that happens before a drug candidate is given to people. These studies typically include toxicology tests (determining whether a substance causes harm at various doses), pharmacokinetics studies (tracking how a substance moves through a living system), and other safety assessments. The results of these studies form the backbone of applications submitted to agencies like the FDA when a company seeks permission to begin human trials or bring a product to market.
In the United States, GLP is codified in 21 CFR Part 58 of the Federal Food, Drug, and Cosmetic Act. It covers products regulated by the FDA, including human and animal drugs, biological products, medical devices, and food additives. Internationally, the Organisation for Economic Co-operation and Development (OECD) publishes its own Principles of Good Laboratory Practice, which serve as the basis for mutual acceptance of safety data between member countries. A study conducted under OECD GLP principles in Japan, for instance, can be accepted by regulators in the U.S. or Europe without repeating the work.
The 10 Core Principles
The OECD framework organizes GLP into ten areas that collectively cover every aspect of how a compliant laboratory operates:
- Test facility organization and personnel: Clear roles, qualified staff, and a designated study director responsible for each study.
- Quality assurance program: An independent unit that audits studies and inspects facilities to verify compliance.
- Facilities: Physical spaces designed to prevent cross-contamination and interference between studies.
- Apparatus, materials, and reagents: Properly maintained, calibrated, and labeled equipment.
- Test systems: The biological systems (animals, cell cultures) used in studies, with appropriate care and documentation.
- Test and reference items: Proper handling, storage, and characterization of the substances being tested.
- Standard operating procedures (SOPs): Written instructions for every routine process in the facility.
- Performance of the study: Following the approved study plan and documenting any deviations.
- Reporting of study results: Final reports that accurately reflect the raw data collected.
- Storage and retention of records and materials: Archiving everything so it can be reconstructed and verified later.
How a GLP Facility Is Set Up
GLP regulations are specific about physical infrastructure. A testing facility must be designed so that different functions and activities are separated enough to prevent one from affecting another. For studies involving animals, this means separate rooms for different species, isolation of individual projects, quarantine areas for newly arrived animals, and dedicated spaces for animals known or suspected to carry disease.
Studies involving biohazardous materials, volatile substances, radioactive materials, or infectious agents require their own isolated areas, entirely separate from general animal housing. Feed and bedding storage must be kept away from animal housing areas and protected from contamination. Test articles (the substances being studied) must be stored separately from the animals and under conditions that preserve their identity, strength, purity, and stability. Even waste disposal gets attention: facilities must minimize the risk of vermin, odors, disease, and environmental contamination.
Documentation and Record Keeping
If there is a single theme running through GLP, it is traceability. Every observation, measurement, and decision must be documented in a way that allows someone else to reconstruct the entire study. Raw data, specimens, protocols, and final reports all follow specific retention timelines under FDA rules.
Records must be kept for at least two years after the FDA approves an application that relied on the study’s results. If the study supported an investigational new drug application or an investigational device exemption, the minimum is five years from the date the results were submitted. For studies that never get submitted to the FDA at all, records must still be retained for at least two years after the study is completed or terminated. Wet specimens like tissue samples have a more flexible standard: they’re kept as long as their quality still allows meaningful evaluation, but never longer than the timelines that apply to other records.
What Inspectors Look For
The FDA conducts inspections of GLP facilities, and the documentation they request at the outset gives a clear picture of what matters most. Inspectors typically ask for the organizational chart, facility floor plan, a master schedule of all studies, the SOP index, equipment maintenance and calibration schedules, personnel training files, and pest control records. From there, they dig into specific areas: how test and control articles are characterized, stored, and labeled; how mixtures are prepared; how reagents are managed; whether the study director fulfilled their responsibilities; whether the quality assurance unit did its job; and whether the final report accurately reflects what actually happened during the study.
Common problems that trigger FDA warning letters include poor documentation practices, failures in the quality assurance program, inadequate standard operating procedures, and problems with how test articles are handled or characterized. These may sound administrative, but in a GLP context, a documentation gap can call an entire study’s results into question.
How GLP Differs From GCP and GMP
GLP is one of three major quality frameworks in the pharmaceutical industry, and each covers a different stage of a drug’s lifecycle.
GLP governs the preclinical stage: laboratory and animal studies that establish a drug’s safety profile before it’s ever given to humans. The focus is on study protocols, proper record keeping, facility conditions, and data integrity.
Good Clinical Practice (GCP) takes over once a drug enters human trials. GCP focuses on protecting the safety and rights of clinical trial participants while ensuring that the data collected during those trials is scientifically valid. It covers study design, informed consent, data collection, and adverse event reporting.
Good Manufacturing Practice (GMP) applies to the production of the drug itself. GMP regulates the design, control, and monitoring of manufacturing processes and facilities. Its goal is to guarantee that every batch of a finished product has the correct identity, strength, quality, and purity.
Think of it as a sequence: GLP ensures the safety data is trustworthy, GCP ensures the human trials are ethical and scientifically sound, and GMP ensures the final product is consistently made to specification. A pharmaceutical company developing a new drug will need to comply with all three at different points in the process.
Why GLP Matters for Drug Development
The practical consequence of GLP is straightforward. Without it, regulatory agencies have no way to trust the safety data a company submits. A toxicology study conducted outside of GLP conditions, no matter how well executed, will not be accepted by the FDA as evidence that a drug is safe enough to test in humans. This means that GLP compliance isn’t optional for any company serious about bringing a pharmaceutical product to market.
GLP also has a significant international dimension. Because OECD member countries accept each other’s GLP-compliant data, a pharmaceutical company can conduct a safety study in one country and use the results to support regulatory applications in dozens of others. Without this mutual acceptance framework, companies would face the enormous cost and ethical burden of repeating animal studies in every country where they seek approval.