Understand ICH Q7 S13

Would additional process validation studies be needed to support a change in the source of an API starting material?

Any change in the API starting material should be assessed for impact on the API manufacturing process and the resulting API quality [ICH Q7, 7.14]. Additional validation studies of the API process may be warranted if the change in the API starting material is deemed significant. In most cases, validation would be expected for a different source of the starting material unless otherwise justified [ICH Q7, 12.1, 13.13]. 

Is a retrospective approach to validation still acceptable?

Prospective validation is normally expected for processes introduced since the publication of ICH Q7. The concept of retrospective validation remains acceptable as an exception for existing, well established products prior to the implementation of ICH Q7 [ICH Q7, 12.44]. If regulatory discussions redefine a step as critical, which had previously been considered non-critical, a protocol describing retrospective analysis of data together with the commitment for concurrent or prospective validation may be an option. Regardless of the type of validation, the quality system should confirm the ongoing robustness of the process (e.g., product quality review). 

Who is responsible for notifying the drug product manufacturer about relevant changes in API manufacturing?

Each party in the supply chain is responsible for transferring information related to quality or regulatory changes to the next customer in the supply chain. The intention is that the information is transferred along the supply chain to the drug product manufacturer in a timely manner [ICH Q7, 13.17, 17.60].