A cannabis-based mouth spray is set to be tested as a potential treatment for an aggressive form of brain tumor called glioblastoma, marking the first-ever major human trial involving medical cannabis as a cancer therapy. Known as Sativex, the spray is already approved for use as a treatment for muscle spasms in patients with multiple sclerosis, and pre-clinical investigations have indicated that it is well tolerated by glioblastoma patients.
Much has been written about the possible anti-cancer properties of certain cannabinoids, with several studies on cultured cells and animals indicating that some of the compounds found in marijuana may prevent the development of tumors. However, without data from human trials, it is impossible to say whether or not medical cannabis really can help in the fight against cancer.
Led by Professor Susan Short from the University of Leeds, the new study will involve 232 glioblastoma patients from 15 hospitals in the UK, two-thirds of whom will receive Sativex in addition to a chemotherapy drug called temozolomide, while the remaining third will be given a placebo in place of the cannabis-based medication.
Glioblastoma is the most common form of brain tumor, and also the most aggressive. Such tumors tend to grow very quickly and spread to many parts of the brain, and frequently recur even after treatment. On average, patients live for less than 18 months following their initial diagnosis.
In a statement, Professor Short explained that “Glioblastoma brain tumors have been shown to have receptors to cannabinoids on their cell surfaces, and laboratory studies on glioblastoma cells have shown these drugs may slow tumor growth and work particularly well when used with temozolomide.”
Indeed, a 2011 study found that the cannabinoids tetrahydrocannabinol (THC) and cannabidiol (CBD) dramatically inhibit the growth of gliomas in petri dishes and in live mice, when administered in combination with temozolomide. Importantly, tumor cells that could not be treated by the chemotherapy drug alone were defeated when these two cannabinoids were added to the equation.
Given that Sativex contains both THC and CBD in equal concentrations, researchers are now keen to try out the product on human subjects. Earlier this year, Short and her colleagues published the results of a Phase I trial involving 27 patients, which tested the safety of this treatment combination in glioblastoma patients. While this small-scale study was not designed to assess the efficacy of these drugs, the authors noted that 83 percent of participants who received Sativex were still alive after one year, compared to 44 percent of those who were given a placebo.
Naturally, no firm conclusions can be drawn from such a small investigation, which is why the Phase II trial is needed. Recruitment of participants is due to begin in early 2022, subject to sufficient funds being raised. The Brain Tumour Charity, which is bankrolling the study, is currently seeking donations as it attempts to secure the £450,000 needed to ensure the project gets off the ground.
Once the trial begins, participants will be asked to self-administer up to 12 sprays of Sativex per day, with the study set to last for a total of three years.
“The treatment of glioblastomas remains extremely challenging,” said Short. “Having recently shown that a specific cannabinoid combination given by oral spray could be safely added to temozolomide chemotherapy, we’re really excited to build on these findings to assess whether this drug could help glioblastoma patients live longer in a major randomized trial.”