Validation must be provided for all processes where the resulting output cannot be or is not verified by subsequent monitoring or measurement. Validation can be excluded from the scope, but not from the processes. However, if it is your contract manufacturing, you are responsible for validation of that process so the validation process can be under your jurisdiction.
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No, exclusion 7.3.7 Design and development validation is not possible since it is a strict requirement from the standard. They have to have documented validation plans and all other arrangments. However, this can be outsourced to some other company or laboratory, but then this should be explained as such.