i. Pathologically confirmed grade 2 or 3 AIN demonstrated by high resolution anoscopy with grade on each occasion re-confirmed at screening by nominated study pathologist from Douglas Hanly Moir (DHM) (pathology case review to be conducted prior to enrolment) ii. Lesion must have been visualised on at least three sequential occasions over at least 12 months, including the pre enrolment screening high resolution anoscopy (HRA).