In Vivo
Experiments conducted in living organisms, encompassing both animal studies and human clinical trials. In vivo evidence is considered stronger than in vitro evidence because it accounts for the complexity of a whole biological system. The distinction between in vitro and in vivo data is fundamental to evaluating peptide compound evidence.
Technical Context
In vivo peptide research uses various animal species: mice (most common — short gestation, genetic manipulation tools, disease models including ob/ob and db/db diabetic mice, DIO diet-induced obesity), rats (larger size for PK sampling, well-characterised models), rabbits (ophthalmology, immunogenicity), dogs (cardiovascular safety, oral absorption), pigs (skin wound healing — similar to human skin), and non-human primates (closest to human physiology — used when other species lack relevant receptors). Regulatory requirements: IND-enabling toxicology studies typically require one rodent and one non-rodent species. For peptide drugs targeting human-specific receptors, transgenic animals expressing the human receptor may be needed. In vivo PK studies establish bioavailability, half-life, and clearance; PD studies establish dose-response relationships and duration of effect; safety studies identify target organs of toxicity and NOAEL.