In 2025, three U.S. agencies within the Department of Health and Human Services (FDA, NIH, CDC) alongside EPA and the Departments of the Navy and Veterans Affairs, began substituting animal testing applications with reliable, human-relevant methods. The impact of this shift in public policy taking place at agencies historically bullish on animal testing is still reverberating in the United States and around the world. Here, we examine the circumstances that enabled such momentous reforms, including the role of the FDA Modernization Act 2.0 in advancing new alternative methods, collectively referred to as NAMs. We explain how animal testing, despite its poor value in predicting the safety and efficacy of drugs in humans, came to dominate drug discovery, basic sciences, and environmental toxicity assessments since the inception of the Federal Food, Drug, and Cosmetic Act (Federal FD&C Act) in 1938. Specifically, we identify critical junctures, including catastrophic government decisions, that made the overall research enterprise acutely dependent on animals, leading to the existing predicament-an indefensible 92% failure rate in translating drugs from preclinical studies to actual therapies. Notably, our analysis chronicles events through the lens of "path dependency," a social sciences phenomenon that occurs when faulty past decisions lock-in future action. Finally, we recognize that our narrative is a departure from the medical establishment account or the talking points of powerful interest groups, including some in the academic elite who continue to shore up animal-centric paradigms in drug development for reasons we also outline.

In the modern immune oncology field, currently there are challenges for allowing for effective immunotherapeutic drug screening systems for immune cell populations in a biologically relevant design for process development and analytical development experimental systems. This challenge has yet to be effectively overcome without using animal models prior to moving towards clinical studies. Without successfully recapitulating in-vivo like settings ex-vivo, data collection and analysis for immunologic behaviors such as T-cell migration, B-cell germinal center formations and isotype class-switching are unable to be demonstrated, and thus limit the research and development procedures and results by preventing thorough characterization of immunotherapies prior to use in human patients within clinical trials. The problem causes increased costs prior to release of immune oncology drug pipelines, as well as extended time delays and use of resources for pharmaceutical, medical device and clinical companies within the industry and the field. One key solution that has been emphasized to resolve the challenge of 2D culture evaluation systems vs. biologically relevant settings of experimentation and data production such as that within in-vivo models has been to utilize bioprinting which allows for the generation of multi-dimensional structures within cell culture environments allowing for more accurate and efficient recapitulation of organic systems within the biology of the body. Historica