The National Institutes of Health (NIH) today announced that its Investigational New Drug (IND) application for mitragynine, the primary psychoactive compound found in Mitragyna speciosa (kratom), has taken effect with the U.S. Food and Drug Administration (FDA). The IND paves the way for an NIH-led phase I clinical trial to evaluate mitragynine as a potential treatment for opioid use disorder.