We present the preliminary data in an ongoing open-label safety and tolerability proof of concept study exploring the potential role for 3,4-methylenedioxymethamphetamine (MDMA)-assisted psychotherapy in treating patients with alcohol use disorder. At this stage, seven participants have completed the full 8-week MDMA-assisted psychotherapy course, including two therapy sessions each with MDMA. This paper focuses on the safety and tolerability of the therapeutic course for the first four participants to complete treatment. Longer-term outcomes of drinking behaviour will be presented later when the full project data are published. Results show all four participants have successfully tolerated the treatment. There have been no serious adverse events related to MDMA, no unexpected physiological responses to the MDMA sessions or changes to blood results or electrocardiograms, measured before and after the 8-week course. We conclude that the treatment is well- tolerated and are making plans to expand the project into a randomised placebo-controlled study