It is up to the company to decide if they want to submit an RPD designation before they request a priority review voucher within their drug application. Submitting and having an RPD designation is not required before submitting a voucher request, however, many sponsors receive their designation before requesting a voucher.
The RPD designation request is reviewed and processed under the Office of Orphan Products Development and the Priority Review Voucher program is under the review division CDER or CBER.