Process Validation for Vendor Change

I have 2 new vendors for KSM of API to be qualified. In this case can I perform 3 validations with using new vendors materials in one study. How to cover two vendors in validation?

First of all you have to check the manufacturing procedure/ROS of the respective KSM with your existing approved vendors ROS.If both are same and there are no potential chances to change in impurity profile of the drug. Then no need to validate the new vendors. You have to compile the quality of the new vendor’s first 3 batches with existing vendor output batches.
If the ROS are differ from existing vendor then u have to qualify the vendors individually by the prospective process validation…
If the ROS of new vendors is same and differ from existing vendor, then you have to validate anyone and compile the quality of the second vendor output batches…

I suggest you (if you want to validate the two vendors in one study) to perform a risk analysis to help you to resolve the gap point that you will not do with unique study.
In this term you demostrate to have a rational to use just one study for 2 vendors . An example it could be if the vendors partecipate at the some material flow, in that case you can mitigate the risk by the analysis of check point.