Scientific Glossary

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Preclinical research is divided into in vitro (cell culture) and in vivo (animal model) studies. In vitro is fastest and cheapest but least representative of human physiology. Rodent models (mice, rats) are most common, with larger animal models (dogs, pigs, primates) for later-stage work. Critically, many preclinical findings do not translate to humans — an estimated 95% of cancer drugs that pass preclinical testing fail in human trials. Most research peptides outside the GLP-1 class are primarily at the preclinical stage. This is why evidence hierarchy assessment matters.