The letter by Binghao Zhao and colleagues accurately describes the main findings of our phase 1 trial of the combined adenoviral therapy using HSV1-TK (Ad-hCMV-TK) and Flt3L (Ad-hCMV-Flt3L) in patients with newly diagnosed high-grade glioma.1 In our dose-finding, first-in-human clinical trial, we established the safety and biological activity of this treatment. The trial established the highest dose tested (ie, 1 × 1011 viral particles of each of the two vectors) as the dose that can be used in follow-up clinical trials, as the maximum tolerated dose was not reached.