Redefining preclinical testing: human-relevant alternatives beyond animal models

Both ethical imperatives and scientific limitations increasingly challenge the traditional reliance on animal models for toxicity testing and drug evaluation, particularly in the era of precision medicine. In response, a paradigm shift is underway, marked by the development of advanced in vitro and in silico technologies that can offer human-relevant and mechanistically informed alternatives. This review examines well-established alternatives, such as receptor binding assays, the monocyte activation test, and enzyme-linked immunosorbent assays, highlighting their applications, mechanisms, and limitations. We further explore emerging human-relevant technologies that include organoids, organ-on-a-chip systems, microphysiological systems, and artificial intelligence-powered modeling platforms. Special emphasis is placed on immune-integrated microphysiological systems as next-generation platforms to evaluate immunotherapy, vaccine responses, and immune toxicities. These models recapitulate dynamic human physiological processes, such as hematopoiesis and germinal center reactions, beyond the capabilities of traditional animal systems. Collectively, these technologies represent scientifically superior and ethically progressive trajectories for preclinical testing. Their integration into regulatory and industrial workflows requires continued refinement, cross-sector collaboration, and standardization.