-In case of variations to the manufacturing process of the active substance, the following approaches may be considered as acceptable:-If the quality characteristics (e.g. physical characteristics, impurity profile) of the active substance are changed in such a way that stability may be compromised, comparative stability data are required in accelerated and long term testing conditions, on the active substance before and after the change:- for active substances known to be stable: three months on one batch of at least pilot scale (see Annex I for the definition of stable active substance).- for active substances known to be unstable: six months on three batches of at least pilot scale.