What u mean by API starting material ? Is CGMP guidelines applicable to API starting material ?
How it differs from intermediate ?
whose structure is close to API. cGMP Guidelines are applicable to this.
All intermediates can not be KSM. a KSM is an intermediate.
Starting Material of an API means,
a material by which we start to produced API, but by this same material we can also produced different API or product. moreover cGMP guideline says that the production or preparation of SM is not covered in GMP, but when we start to utilize this SM in our Route of synthesis, the GMP starts to work. Intermediate may called as KSM whose quality is deeply affect the quality of our API.
I agree with comments. You may find useful onformation in following site on the requirements for selection and justification of starting material.
www.ema.europa.eu › open_document