Two recent pharmacogenetic studies of commonly used medications in autism indicate that genetic profiles may hold promise in identifying those who would respond well and those likely to have side-effects. A study by a team in Portugal examined how variations in eight candidate genes may help estimate levels of improvement with the use of risperidone and those most at risk for increased weight gain – a problematic side effect of this treatment. Risperidone is an atypical anti-psychotic and one of two drugs with a specific indication to treat irritability and maladaptive behaviours associated with autism. These eight genes are key in the biological systems involved in drug metabolism (how the body uses the drug) and pharmacodynamics (what the drug does to the body). Four gene variations (called polymorphisms) were found to be predictive of clinical improvement. Two others were indicative of those at risk of increased weight gain. Another study, by a team at the University of Illinois, Chicago, examined genes applicable to the drug Escitalopram, which belongs to the class of drugs called selective serotonin reuptake inhibitors (SSRIs). SSRIs have been indicated in clinical practice and smaller clinical trials as effective treatments for repetitive behaviours; larger clinical trials, however, have not demonstrated positive effect, potentially due to individual differences within the study group. This study looked at genetic variations of a serotonin gene involved with the specific targets of the SSRI medications. The researchers found that one variation was associated with a smaller reduction in irritability scores.
These studies are among the few pharmacogenetic studies that have been conducted for autism, and additional larger scale studies are needed to confirm these findings. Nonetheless, these studies confirm the potential for pharmacogenetics to refine research approaches to treatment trials in ASD. This research is an important first step for developing more personalized treatments for individuals with autism.