Cannabinoids: novel medicines for the treatment of Huntington's disease

Cannabinoid pharmacology has experienced a notable increase in the last 3 decades which is allowing the development of novel cannabinoid-based medicines for the treatment of different human pathologies, for example, Cesamet® (nabilone) or Marinol® (synthetic Δ9-tetrahydrocannabinol for oral administration) that were approved in 80s for the treatment of nausea and vomiting associated with chemotherapy treatment in cancer patients and in 90s for anorexiacachexia associated with AIDS therapy. Recently, the british company GW Pharmaceuticals plc has developed an oromucosal spray called Sativex®, which is constituted by an equimolecular combination of Δ9-tetrahydrocannabinol- and cannabidiol- enriched botanical extracts. Sativex® has been approved for the treatment of specific symptoms (i.e. spasticity and pain) of multiple sclerosis patients in various countries (i.e. Canada, UK, Spain, New Zealand). However, this cannabis- based medicine has been also proposed to be useful in other neurological disorders given the analgesic, antitumoral, anti-inflammatory, and neuroprotective properties of their components demonstrated in preclinical models. Numerous clinical trials are presently being conducted to confirm this potential in patients. We are particularly interested in the case of Huntington's disease (HD), an autosomal-dominant inherited disorder caused by an excess of CAG repeats in the genomic allele resulting in a polyQ expansion in the encoded protein called huntingtin, and that affects primarily striatal and cortical neurons thus producing motor abnormalities (i.e. chorea) and dementia. Cannabinoids have been studied for alleviation of hyperkinetic symptoms, given their inhibitory effects on movement, and, in particular, as disease-modifying agents due to their anti-inflammatory, neuroprotective and neuroregenerative properties. This potential has been corroborated in different experimental models of HD and using different types of cannabinoid agonists, including the phytocannabinoids present in Sativex®, and we are close to initiate a clinical trial with this cannabis-based medicine to evaluate its capability as a disease-modifying agent in a population of HD patients. The present review will address all preclinical evidence supporting the potential of Sativex® for the treatment of disease progression in HD patients. The article presents some promising patents on the cannabinoids.