In a new study, researchers found that an antidepressant in use for decades, repurposed to fight prostate cancer, shows promise in helping patients whose disease has returned following surgery or radiation.
The drug—an MAO inhibitor called phenelzine—represents a possible new treatment with fewer side effects for men with recurrent prostate cancer.
This study is the first clinical trial of an MAO inhibitor in cancer patients. If the findings are confirmed, this could be part of a new avenue for patients that could avoid undesirable side effects of standard therapies.
The research was conducted by a team at USC.
Prostate cancer is the second most common cancer—behind skin cancer—diagnosed in men in the United States, with about 174,000 cases diagnosed each year.
For most patients, prostate cancer is treated with surgery or radiation or a combination of the two.
After surgery, a patient’s PSA should be close to zero. However, in about one-third of patients, the PSA level rises again, indicating cancer has returned.
Hormone therapy is a standard treatment for recurrent prostate cancer, but it comes with serious side effects that impact the quality of life.
That’s where MAO inhibitors may be able to help.
In this study, 11 of 20 participants had a decline in their PSA levels after 12 weeks of twice-a-day treatment, with the greatest decline in PSA being a 74% drop.
PSA stands for prostate-specific antigen; it’s a biomarker for prostate cancer circulating in the blood.
MAO inhibitors treat depression by readjusting levels of neurotransmitters such as serotonin and dopamine in the brain.
The downside is that the medication requires dietary changes and careful avoidance of drug interactions to prevent serious side effects.
In prostate cancer, MAO inhibitors disrupt androgen receptor signaling—the main growth pathway for prostate cancer.
Previous studies with animals and human prostate cancer cell lines showed that MAO inhibitors decreased the growth and spread of prostate cancer.
Because the MAO inhibitor phenelzine is already FDA-approved, the researchers were able to rapidly design and implement a pilot study to test the drug’s ability to fight cancer.
Additional studies are planned, and the team has patented a second-generation MAO inhibitor tagged with a substance that could help doctors see where cancer has spread.
The lead author of the study is Jean Shih, a University Professor at USC’s School of Pharmacy.
The study is published in Prostate Cancer and Prostatic Diseases.
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