The difference between GLP and non-GLP is that non-GLP studies do not require all of the rigor of GLP studies. Although GLP is written into the Official Register of the United States, compliance with GLP is not required for in vitro drug metabolism and drug interaction studies. Compliance to GLP requirements is not required for discovery, basic research, screening or other studies where the safety of a product is not being assessed. GLP is required for extrapolation to humans. Non-GLP studies can be of high quality for any other purpose.
In many studies where GLP compliance is not required and for which the intensive reporting requirements and facility requirements could be an impediment, non-GLP options can represent an advantage. Quality assurance does not have to inspect the conduct of non-GLP studies or records. Analysis of the concentration of test article dosing solutions is not required in non-GLP studies. Alternatives to a complete study reports, like data summaries, are acceptable in non-GLP studies. Methodological validation by quality control is not required for Non-GLP studies.