Viral Vector–Based Immunotherapy in Metastatic Castration-Resistant Prostate Cancer
Posted: Monday, April 29, 2019
As reported in a phase III trial conducted by James L. Gulley, MD, PhD, of the National Institutes of Health, and international colleagues, a viral vector–based immunotherapy vaccine (PROSTVAC) appeared to be safe but did not impact overall survival in patients with metastatic castration-resistant prostate cancer. The study findings were published in the Journal of Clinical Oncology.
“In conclusion, we observed that vaccines induce T cells that are capable of infiltrating tumors, but that this immune response does not translate into clinical benefit poses a major challenge to the immunotherapy community,” the investigators concluded.
A total of 1,297 patients with metastatic castration-resistant prostate cancer were enrolled in the study and were randomly assigned to three groups: PROSTVAC, PROSTVAC plus granulocyte-macrophage colony-stimulating factor, or placebo. They were stratified by prostate-specific antigen and lactate dehydrogenase levels.
When futility criteria were met at the third interim analysis, the trial was stopped early. For the treatment and placebo groups, similar adverse events were experienced, and primarily injection-site reactions and fatigue were reported. Less than 1% of all patients experienced serious treatment-related events, and there were no reports of myocarditis or pericarditis. Although the treatment was considered to be safe, it did not impact overall survival.
Moving forward, the authors noted that the vaccine may prove to be of clinical benefit “in the right context.” For instance, it is being studied with different antigen targets, in other disease settings, and in combination with checkpoint inhibition.
Disclosure: The study authors’ disclosure information may be found at ascopubs.org.