Methods
Peripheral blood mononuclear cells (PBMCs) were isolated from 200 healthy donors of diverse age groups, sexes, and ethnic backgrounds. Cells were exposed to a panel of mechanistically diverse chemical compounds targeting key stress pathways, including DNA damage, ER stress, oxidative stress, and inflammation. Functional responses, including cell death and mitochondrial function, were measured using high-content imaging. For a subset of donors, transcriptomic profiling with TempO-Seq was performed to connect functional outcomes with pathway-specific gene expression changes. Inter-individual variability was analyzed across donor groups to assess the influence of sex, age, and ethnicity on cellular responses.

Results / Conclusions
Functional imaging revealed clear, concentration-dependent cellular responses. For DNA damage, cell death responses were highly consistent across donors, showing minimal inter-individual variation. In contrast, compounds targeting ER stress elicited pronounced differences between donors, highlighting pathways were variability is most evident. Preliminary transcriptomic analysis in a subset of donors confirmed that observed functional differences corresponded to differential pathway activation, providing mechanistic insight into inter-individual variability. Across the 200-donor cohort, no major differences were observed between sexes, while trends with age and ethnic background suggest potential sources of variability, although some groups remain underrepresented. These findings demonstrate the value of integrating functional and transcriptomic data to capture human variability, identify sensitive and resilient individuals, and support more quantitative, mechanism-based risk assessment. Ongoing recruitment and future transcriptomic profiling will further enhance understanding of population-level variability and strengthen the basis for human-relevant safety evaluation.