Hi Sam,
ITT analysis set and safety analysis set should be defined in the documents of Statistical Analysis Plan(SAP) or Data Presentation Specifications(DPS).
The definition may varies from different protocols but mainly the same:
Safety: any subject who receive at least 1 dose of study medication.
ITT: be classified according to the assigned treatment group, regardless of the actual treatment received.
Also, Safety is used for safety analysis, like AEs
ITT is often used for efficacy analysis, which is conservative for superiority trial.