The central issue here is the proper calculation of patent term extensions (PTEs) for reissued patents under the Hatch-Waxman Act, specifically whether the extension should be based on the original patent's issue date or the reissued patent's issue date. The court affirms the district court's finding that for reissued patents retaining claims to a drug product that underwent regulatory review after the original patent's issuance, the PTE should be calculated from the original patent's issue date, supporting the purpose of compensating for lost market exclusivity during regulatory delays.