A phase i does-escalation and expansion study of epidiolex (cannabidiol) in patients with biochemically recurrent prostate cancer

ABSTRACT

Background: There is a need for a low toxicity option for men with prostate cancer with biochemical recurrence (BCR) following primary curative therapy. Cannabinoids (CBD) have antitumor activity in preclinical studies, but products may vary in activity without clear standardization. As epidiolex is a standardized FDA approved oral CBD solution for treatment of certain types of seizures, we studied epidiolex in patients with BCR of prostate cancer to determine safety and dosing of this therapy to support future studies. Methods: We present an open-label, single center, phase I dose escalation study followed by a dose expansion. Patients with BCR prostate cancer after primary definitive local therapy (prostatectomy +/- salvage radiotherapy or primary definitive radiotherapy) were eligible. Majority of our patients' prostate-specific antigen (PSA) doubling time was ≤ 12 months. All patients were screened for urine tetrahydrocannabinol (THC) prior to enrollment. With use of a Bayesian optimal interval design, patients received escalating doses of epidiolex starting at 600mg daily and up to 800mg daily. All patients were treated for 90 days followed by a 10 day taper. The Primary endpoints were safety and tolerability. Patients were monitored for both acute (30 days) and chronic (90 days) treatment-related toxicities. Secondary endpoints included change in PSA levels and testosterone levels from baseline throughout the treatment period. Results: A total of 21 patients were enrolled but four withdrew from the study (one patient was hospitalized with COVID-19 and three patients requested to stop due to grade 2 adverse events (AEs). There were seven patients included in the dose escalation phase. Four patients received 600mg daily;two of the four in this phase did not finish the first 30 days (one with COVID-19 and one withdrew). The other three patients received 800 mg daily. No dose-limiting toxicities were observed at any dose level so an additional 14 patients were enrolled at the 800mg dose. Treatment-related chronic AEs occurring in >10% of patients were grade 1 or 2 diarrhea (47.6%), grade 1 or 2 nausea (23.8%) and grade 1 or 2 fatigue (19%). The mean PSA at baseline was 2.9 ng/ml. One patient developed oligo-metastasis disease, two patients progressed after the study period, and one patient died from a non-treatment or disease-related cause. Conclusions: Epidiolex at a dose of 800mg daily appears to be safe and tolerable in patients with BCR of prostate cancer, supporting a safe dose for future studies to determine if there is clinical activity to delay development of hormone refractory metastatic disease.