CATALYST is an ARPA-H program focused on improving predictions of drug safety and efficacy before clinical trials. It supports development of human physiology-based computational models and related methods, with attention to pharmacokinetics—including absorption, distribution, metabolism, and excretion—and pharmacodynamics. Its technical areas include data discovery and deep-learning methods for drug-safety models, living-systems tools for model development, and in silico models of human physiology. The program aims to make preclinical assessments more representative of human biology and to support evaluation of investigational drug candidates.