Brain Cancer Vaccine Inches Closer to Reality
A new article published in the journal Nature touts promising results from a landmark phase 1 trial testing a novel vaccine designed to help a patient’s immune system better target brain tumors. Data from the German study suggest the experimental vaccine is safe and stimulates a significant immune response that slows tumor progression, so much so that a phase 2 trial is being planned.
While the news is positive, it may be too soon to get excited, according to Dr. Michael Vogelbaum, chief of neurosurgery and program leader of the Neuro Oncology Program at Moffitt Cancer Center.
“This is an early stage trial that focused on safety and also looked at biological evidence of an immune response to the vaccine,” Vogelbaum said.
He added that the results did not show any meaningful safety issues, which is an important first step, and that there was some evidence of an immune response when trial participants’ blood was examined. However, Vogelbaum believes the study wasn’t large enough to show whether these safety and immune response data will translate into longer patient survival.
Thirty-three newly diagnosed glioma patients with a gene mutation affecting an enzyme called isocitrate dehydrogenase 1 (IDH1) were recruited for this study. Looking at immune responses, the researchers found 93% of patients displayed an effective response to the vaccine. Immune T cells specifically targeting the IDH1 mutation were detected in those responsive patients.
“This study provides the rationale for doing the next study, which will begin to evaluate whether the vaccine could be effective at controlling or shrinking these types of low grade gliomas,” he said.
Diffuse gliomas are a particularly difficult kind of brain cancer to treat since they can spread across the brain, making it difficult to easily eliminate them through traditional surgery. These tumors do share a common feature, however; over 70% of low-grade gliomas have the gene mutation affecting the IDH1 enzyme.
The German Cancer Research Center, which conducted this study, has worked for years to create a vaccine that helps a patient’s immune system target these IDH1 mutated cells.
“Low grade gliomas that have the IDH1 mutation that is being targeted by this vaccine are known to be much less aggressive than most other tumors that arise from the brain,” Vogelbaum said. “There are multiple studies that have suggested that the median survival of these patients may exceed 15 years with conventional treatments. So, the five-year survival of 84% observed in this study is well within what would be expected based upon current treatment approaches.”
The challenge, he added, is that in order to demonstrate that the vaccine is effective for improving overall survival, scientists will have to follow patients for longer than a decade to determine whether their results are better than current approaches.
This trial, which shows some promise, will take many years to complete.
Vaccines have been in the headlines a lot lately, and Vogelbaum is quick to point out that only one approved vaccine specifically targets cancer: Provenge, which is for prostate cancer. Other vaccines produced for hepatitis B and human papillomavirus have shown effectiveness in preventing types of cancer caused by those viruses. Provenge targets a protein that is made at a very high level by prostate cancer cells.
The brain cancer vaccine developed by the German researchers follows Provenge’s example. The IDH1 mutant protein is made only by the tumor cells in low grade glioma that has that specific mutation. In patients who have tumors presenting with other IDH1 mutations, it won’t work.
“It remains to be seen whether the immune system is capable of mounting enough of a response to these tumors to be able to prevent them from growing, as there are multiple mechanisms that act to suppress the action of immune effector cells within the brain,” Vogelbaum said. “It is encouraging to see that the immune system can be activated against the IDH1 mutant protein. But only efficacy oriented clinical trials will give us the opportunity to determine whether it is enough of an effect to allow patients with these low-grade gliomas to live longer or be cured.”
