Phytocannabinoid cannabidiol (CBD) in neurodegenerative diseases: From polypharmacology to drug development.

Cannabidiol (CBD) is a non-intoxicating phytocannabinoid that has attracted interest as a multi-target neurotherapeutic candidate for neurodegenerative diseases. CBD is a lipophilic terpenophenolic chemotype whose phenolic redox chemistry, membrane partitioning, cytochrome P450-mediated metabolism, and formulation-dependent exposure are central to its biological activity and translational limitations. In addition, CBD engages a broad target network relevant to neurodegeneration. Major components include cannabinoid receptors, transient receptor potential channels, peroxisome proliferator-activated receptor-γ, adenosine and serotonin signaling systems, voltage-gated calcium channels, and redox-regulatory pathways. These mechanisms converge on neuroinflammation, excitotoxicity, mitochondrial dysfunction, impaired proteostasis, and synaptic injury. Preclinical studies across models of Alzheimer's disease, Parkinson's disease, multiple sclerosis, Huntington's disease, and amyotrophic lateral sclerosis consistently support CBD's anti-inflammatory, antioxidant, mitochondria-protective, and neuroprotective pharmacology. The magnitude of these effects depends on dose, treatment timing, model system, and route of administration. Clinical evidence remains preliminary and is mainly symptomatic, with signals in agitation, sleep disturbance, spasticity, quality of life, and neuropsychiatric symptoms rather than proven disease modification. Key barriers to development include low and variable oral bioavailability, incomplete brain exposure data, uncertain active metabolite contributions, limited target-engagement biomarkers, and insufficient exposure-response definition. Future development of CBD and optimized cannabinoid-derived analogues will require medicinal chemistry strategies to improve potency, selectivity, metabolic stability, CNS exposure, and formulation performance. Parallel biomarker-driven clinical trials are needed to define pharmacokinetic-pharmacodynamic relationships and evaluate disease-modifying potential.