Primary cells are cells taken directly from a pieces of tissue and established for growth in vitro.

These cells have undergone very few population doublings and are therefore more representative of the main functional component of the tissue.

Subsequently primary cells allow to use to highlight potential differences between humans and preclinical test species.

Before in vivo studies (Preclinical studies), human primary cultured cell can be used to refine doses and

reduce the number of animals required for preclinical toxicology.

Therefore human primary cultured cells can be used to determine accuracy of extrapolating human data from an animal model.