To date, clinical trials assessing the efficacy of AQP1 gene therapy in IR-induced xerostomia have employed subjects previously treated with radiation doses >15 Gy.83,84 Considering the damage caused by ionizing radiation exceeding 15 Gy to SG secretory cells, it is remarkable that AQP1 gene therapy has shown some degree of effectiveness in these patient cohorts. The gene discussed is AQP1; the disease is xerostomia.