In Silico Research Is Rewriting the Rules of Drug Development: Is It the End of Human Trials?

Recent advances in computational biology, artificial intelligence (AI), and regulatory science are rapidly displacing the traditional reliance on animal and early-phase human trials in drug development. In April 2025, the U.S. Food and Drug Administration announced a landmark decision to phase out mandatory animal testing for many drug types, signaling a paradigm shift toward in silico methodologies. This editorial explores how computer-based models, especially digital twins, are emerging as the fourth pillar of biomedical science, capable of simulating complex human systems with remarkable accuracy. Drawing on real-world examples from oncology, neurology, and regulatory submissions, the editorial argues that in silico tools are no longer ancillary but central to modern research. These technologies enable rapid, ethical, and cost-effective drug discovery while offering personalized therapeutic insights. As machine learning, multi-omics integration, and predictive simulations mature, their regulatory credibility grows, particularly in initiatives such as model-informed drug development and digital therapeutics. The editorial concludes by urging the adoption of standardized frameworks, explainable AI, and infrastructure investment to ensure in silico research fulfills its transformative potential. Within a decade, failure to employ these methods may no longer be merely outdated, it may be indefensible.