Parkinson’s disease as a multi-axis systems disorder: integrating molecular pathology and circuit-level therapeutics

Parkinson’s disease (PD) has generated extensive mechanistic insight, yet nearly all candidate disease-modifying therapies have failed in clinical trials. Antibodies targeting α-synuclein, mitochondrial antioxidants, lysosomal interventions, and anti-inflammatory agents frequently achieve target engagement without slowing clinical progression, creating a central paradox in PD therapeutics. Here we propose that this discrepancy arises because PD is not primarily a single-pathway neurodegenerative disorder but a multi-scale systems disease. Molecular pathology, organellar dysfunction, immune activation, and large-scale network instability form a self-reinforcing cascade in which interventions acting at a single biological level cannot substantially modify disease once degeneration is embedded within distributed neural circuits. This framework generates testable predictions: pathway-targeted therapies may show benefit primarily in prodromal or biomarker-defined populations, whereas established clinical PD will likely require combination strategies coupling circuit restoration with axis-matched molecular interventions. Therapeutic responsiveness should therefore correlate more strongly with network integrity than with target engagement alone. Viewing PD as a multi-scale systems disorder provides a unifying explanation for repeated therapeutic failures and offers a framework for biomarker-guided, stage-matched disease-modifying trials. • Parkinson’s disease reflects a multi-axis systems failure involving α-synuclein proteostasis, lysosomal–mitochondrial dysfunction, metabolic stress, immune activation, and connectome instability. • Single-target therapies have shown limited disease-modifying effects, suggesting that interventions aimed at individual molecular pathways may be insufficient to disrupt the self-reinforcing pathological loops that sustain PD progression. • Cell-replacement strategies demonstrate that restoration of dopaminergic circuitry can produce functional improvement, indicating that therapeutic interventions operating at different biological levels may address complementary aspects of disease biology. • A unified mechanistic model reveals coordinated collapse across organellar, metabolic, and immune pathways, explaining selective neuronal vulnerability and broad clinical heterogeneity. • A precision-medicine framework may be necessary, integrating circuit reconstruction with axis-matched molecular interventions and biomarker-based patient stratification to improve the likelihood of disease modification.