A novel immune-based, gene therapy approach is entering phase 2 trials (ClinicalTrials.gov Identifier: NCT04006119) for glioblastoma multiforme (GBM) after promising preliminary safety and efficacy data. Despite encouraging results in several tumor types such as melanoma, colorectal, and lung, immunotherapies have yet to show any significant benefit in patients with brain tumors. The new technique by Ziopharm hopes to reverse that trend.