Abstract: Disclosed herein are methods and compositions for performing assays for determining efficacy of drugs using rat SCID models that exhibit excellent take rates, and excellent tumor growth rates. The methods and compositions offer dramatically improved efficiencies compared to corresponding mouse equivalents.

Abstract: Disclosed are non-human mammals having a modified liver and methods of making such non-human mammals having a modified liver. The modified liver may be characterized by a non-germline, stable integration of a non-endogenous gene targeted to the liver of the non-human mammal. In certain aspects, the modified liver may have greater than at least 30% ablation of the endogenous hepatocyte population of the non-human mammal. In certain aspects, the non-human mammal may comprise at least 30% non-endogenous hepatocytes. The disclosed non-human mammals may be useful for pharmacology, drug absorption, distribution, metabolism, and excretion studies, collectively ADME and toxicology studies (ADME-tox), and/or drug screening.