Bioequivalence and Bioavailability Forum

Dear Lázló!

❝ You had made a given formulation and it passed the biostudy. No problem till this point. :)

❝ However, the API supplier has changed and the new API is quite different from the previous one (impurity profile, residual solvents, etc.).

❝ The new API is also acceptable but DIFFERENT.

❝ Can I use the results of the biostudy conducted with the preceding API?

As an entry point I would suggest FDA's 'Scale-Up and Post-Approval Changes' (SUPAC) Guideline.
IMHO you are subject to a change in 'Manufacturing, Level 3' (section VI, page 21pp).

❝ Can I use the results of the biostudy conducted with the preceding API?

No.

❝ Do I have to prove that the differences between the API would not alter significantly the bioavailability (and the safety) of the API?

Such a change would call for a biostudy (the classical example of phenytoin fatalities in the late 70ies was a change in the manufacturing process of a supplier, which was not communicated to the company).

❝ If so, how?

If you are successful with an IVIVC, you may apply for a biowaiver…