AQP1 and xerostomia: In both preclinical animal models and Phase 1 clinical trials, viral vectors delivering the human aquaporin-1 gene (AQP1) have demonstrated both increased expression of aquaporin-1 protein by SG cells and improved saliva production.82 However, while increased salivary flow may alleviate some of the symptoms of xerostomia, it does not entirely restore normal SG function.