Advanced Prostate Cancer Patients May Respond Well to Keytruda Immunotherapy, According to Study

Advanced Prostate Cancer Patients May Respond Well to Keytruda Immunotherapy, According to Study
Immunotherapy with Keytruda (pembrolizumab) may be an effective way to treat advanced-stage prostate cancer, according to a preliminary study conducted by researchers at Oregon Health and Science University (OSHU) Knight Cancer Institute. “It’s pretty remarkable, especially in light of the fact that many people doubted this approach could work at all,” said Dr. Julie Graff in a press release. Graff is the senior author of the study "Early evidence of anti-PD-1 activity in enzalutamide-resistant prostate cancer," published in the journal Oncotarget. Keytruda is a monoclonal antibody that blocks the PD-1 receptor on the surface of  immune T-cells, allowing them to recognize and destroy tumor cells. The FDA-approved drug has been shown to work well in melanoma and lung cancer but had so far not produced any evidence of anti-tumor activity in prostate cancer. Researchers administered Keytruda in 10 men with metastatic prostate cancer who had received androgen deprivation therapy or the androgen receptor antagonist Xtandi (enzalutamide) but failed to respond to it. Three of the 10 men who participated to the trial responded remarkably well to Keytruda treatment. Prostate specific antigens (PSA) in their blood, which is an early measure of treatment response, dropped rapidly and dramatically (from 46, 71, and 2,503 ng/ml respectively, to less than 0.1 ng/ml). In addition, two of the three men saw their tumors shrink and reported a reduction in cancer-related pain to the point of not needing their opiate pain medication. Finally, the three patients who responded to Keytruda remained free of cancer progression at 30, 55, and 16 weeks of follow-up, respectively. Drugs currently available to treat prostate cancer rarely result in PSA levels lowe
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