This is a double-blind, randomised, placebo-controlled study investigating the efficacy of a full-spectrum medicinal cannabis plant extract on core and associated ASD symptoms over placebo. Participants will be randomly allocated to either NTI164 or placebo at a 1:1 ratio and blood samples will be collected and surveys completed at baseline and Week 16. This study will expand efficacy and safety data of NTI164 and provide additional mechanism of action data of NTI164 in this patient cohort.