Research Study Links Skill Loss in Kleefstra Syndrome to Astrocytes and Investigates Response to Olanzapine Katerina Tzimourta, June 30, 2026August 21, 2026 An international study combined observations from 54 individuals with Kleefstra syndrome type 1 with experiments on human cells and mouse model brain tissue. In 16 individuals who had received olanzapine, indications of functional improvement were recorded in some cases, but no randomized clinical trial was conducted and the findings do not establish a treatment.