HRAS and Alzheimer disease: Guided by a multi-omics-led and systems biology-driven principle, PI4AD addresses three objectives: (i) clinical target prioritisation—validating prioritisation efficacy by recovering clinical proof-of-concept targets; (ii) disease-specific targeting—employing ANNs to distinguish AD from neuropsychiatric disorders via self-organising maps; and (iii) pathway crosstalk analysis—identifying critical nodal genes (e. g., HRAS and MAPK1) and repurposable drugs through systems biology.