The definition of an Investigational Medicinal product (IMP) is provided in Directive 2001/20/EC, Article 2 (d) (2), as “a pharmaceutical form of an active substance or placebo being tested or used as areference in a clinical trial, including products already with a marketing authorization but odofied (change to dosage form, or its primary or secondary packaging) in a way different from the authorized form, or when used for an unauthorized indication, or when used to gainfurther information about the authorized form”.Medicinal products with a marketing authorization (MA) are classified as IMPs when they are to be used as the test drug or reference drug in a clinical trial, provided they are used or assembled (formulated or packaged) in a way different from the authorized form, or used for an unauthorized indication, or used to gain further information about the authorized form. On this basis, provided that the requirement(s) are met, reference products used as comparators should be considered as IMPs.