Cannabidiol is a medicine that is being developed for the treatment of TSC patients who experience inadequately-controlled seizures. It is being developed as an oral medicine to be added to existing treatment options for TSC (‘add-on therapy’). Cannabidiol has a unique chemical structure that makes it prevent or stop seizures and is thought to have cumulative effect. If licensed, cannabidiol will offer an add-on treatment option for patients with TSC who experience inadequately-controlled seizures.