One in four safety-related failures are due to central nervous system (CNS) toxicity. But because conventional models used in preclinical Good Laboratory Practice (GLP) safety testing fail to accurately predict neurotoxicity, almost 80% of issues remain undetected until clinical trials. The result is costly trial failures, wasted R&D spend, and risks to patient safety that could have been prevented earlier. Addressing this translational gap will require more predictive, standardized, and human-relevant approaches to CNS safety testing.
Why current neurotoxicity models fall short
Most CNS safety testing still relies on animal behavioral studies or 2D cell culture cytotoxicity assays, endpoints that poorly correlate to the functional network disruptions clinicians see in patients. For example, drug-induced seizures often result from species-specific mechanisms such as ion-channel modulation and excitation–inhibition imbalance. Because seizure susceptibility varies widely between species, animal models often generate both false positive and false negatives. Without human-relevant functional endpoints in preclinical testing, many seizure-relates CNS risks go undetected until late in development.
New Approach Methods gain regulatory momentum in 2025
U.S. policy is accelerating this shift. In April 2025, the U.S. FDA released its Roadmap to Reducing Animal Testing in Preclinical Safety Studies, outlining a phased strategy to integrate New Approach Methodologies (NAMs)—including organoids, Organ-Chips, and computational models—as more clinically predictive alternatives to animal testing. The roadmap frames a 3-5-year vision in which animal studies become the exception rather than the rule for preclinical safety assessment.
Soon after, the NIH reinforced that direction. In July 2025, it announced that new funding opportunities would no longer support projects relying solely on animal models of human disease and must include NAMs. Two months later, the agency launched the Standardized Organoid Modeling (SOM) Center, backed by an initial $87 million over three years, to develop reproducible organoid models and serve as a national hub for model validation and data sharing.
Together, these initiatives mark a clear policy and scientific realignment: major agencies are converging on the need for clinically predictive, reproducible, and standardized NAMs. This signals not just regulatory openness but an expectation that translational safety science needs to evolve toward models that better represent human outcomes.
How human organoid models fill the gap
This shift reflects growing recognition that human biology cannot be faithfully modeled in animals, particularly for the CNS. Human-derived brain organoids offer a more clinically predictive alternative. Generated from induced pluripotent stem cells, these engineered 3D tissue models reproduce cortical cellular diversity and functionality of the human, allowing neurotoxicity to be assessed through functional endpoints such as network activity.
However, reproducibility remains a major challenge. Many in-house organoid systems vary in size, cell composition, or functional response, all of which can obscure true drug effects and limit data comparability. Without standardization, even promising models risk falling short of regulatory expectations for consistency and validation. Overcoming that variability is critical to realizing the translational potential of organoid-based CNS safety testing.
28bio CNS-3D: Raising the Standard for Predictive CNS Safety
Among neurological NAMs (or complex in vitro models), 28bio CNS-3D stands out for its combination of human relevance, reproducibility, and functional readout fidelity. Built from iPSC-derived cortical organoids, CNS-3D organoids reflect key features of the human brain—a balanced mix of excitatory and inhibitory neurons supported by astrocytes, maintaining stable, synchronized network activity across studies.
The technology detects neuromodulatory and seizurogenic effects—the same disruptions clinicians track via EEG or electrophysiology—using high-throughput calcium-imaging assays. These functional signatures, including shifts in synchrony, frequency, and amplitude, provide early indicators of CNS risk long before overt toxicity occurs.
CNS-3D organoids also show remarkable consistency across batches and labs, maintaining uniform organoid size, cellular ratios, and pharmacological response profiles. This reproducibility ensures that experimental results reflect drug action rather than assay variability, enabling confident interpretation of study results throughout screening programs.
By integrating CNS-3D organoids early in drug discovery, developers can identify neurotoxic liabilities before animal or human testing, generate human-based functional evidence aligned with evolving FDA expectations, and advance safer, more predictive CNS pipelines.
The Time to Act
The convergence of regulatory reform and technological maturity has created a clear path forward for CNS safety testing. Human-derived organoids now enable clinically relevant and scalable neurotoxicity testing with mechanistic insight unattainable in animal models. Organizations that adopt these models now will identify liabilities earlier, prevent costly late-stage failures, and redirect R&D spend on candidates with the highest chance of clinical success.
For more information on 28bio CNS-3D Technology, visit: https://www.28bio.com/products-services/cns-3d-technology