Human brain organoids have evolved from early neurodevelopmental models into platforms for therapeutic discovery. Here, we highlight two cases in which organoid-derived findings enabled FDA-approved clinical trials. Patient-derived organoids modeling Pitt-Hopkins syndrome revealed human-specific, TCF4-dependent abnormalities and supported the development of a regulated AAV gene therapy. In parallel, Rett syndrome organoids cultured aboard the International Space Station uncovered space-induced neural senescence, characterized by retroelement-associated neuroinflammation, prompting evaluation of antiretroviral therapy. These examples illustrate how organoids can reveal disease mechanisms that are inaccessible or incompletely reproduced in animal models, while animal studies remain essential for validation and safety assessment. As the field advances, matching model complexity to experimental purpose—and ensuring reproducibility, scalability, and accessibility—will be critical. Human brain organoids are crossing a translational threshold, emerging as engines of therapeutic discovery and gateways to clinical intervention.