According to new research published in Frontiers in Pharmacology, cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC) were found to interfere with the growth and spread of ovarian cancer cells.
The findings come from a study led by Siyao Tong of Khon Kaen University, which examined how CBD and THC affect ovarian cancer at the cellular level. Ovarian cancer is often diagnosed at a late stage, has high recurrence rates, and remains difficult to treat with existing therapies.

In the study, researchers exposed two ovarian cancer cell lines, one sensitive to platinum-based chemotherapy and another resistant, to CBD, THC, and a combination of both. A healthy cell line was also tested to assess potential toxicity. The results showed that both cannabinoids reduced cancer cell reproduction, with the most pronounced effects seen when CBD and THC were used together.

“Both compounds exhibited promising anti-cancer effects,” Tong said, noting that while neither CBD nor THC alone eliminated a large number of cancer cells, their combination was significantly more effective. “It is possible that THC and CBD act on cancer cells through different mechanisms and, when used together, their effects are potentiated.”

The strongest inhibitory response was observed when CBD and THC were combined at a 1:1 ratio. Additional experiments showed that the compounds also reduced cell migration, suggesting a potential role in limiting metastasis, which is responsible for many ovarian cancer deaths.

Researchers found that both cancer cell lines responded similarly to treatment, indicating that the cannabinoids may be effective across different ovarian cancer subtypes. Importantly, the compounds had minimal impact on healthy cells, a finding that suggests cannabinoid-based therapies could be less toxic than many current treatments.

“Ovarian cancer remains one of the most deadly gynecological malignancies, characterized by late diagnosis, high recurrence rates and limited effective treatment options,” Tong said. “Our goal is to find alternative drugs that can improve efficacy and potentially reduce toxicity, ultimately bringing new hope to patients facing this challenging disease.”

The researchers cautioned that the work remains preliminary. All experiments were conducted in vitro, meaning they do not yet reflect how tumors behave in living organisms. “We have not included models in vivo and pharmacokinetic data, which are essential to determine whether CBD/THC can be used safely and effectively clinically,” Tong said.

While further preclinical and animal studies are needed before any patient applications are possible, the researchers said the findings provide a foundation for future work exploring cannabinoid-based strategies for ovarian cancer treatment.