In a case it described as “‘a prime example’ of when ODP does not apply,” the Federal Circuit recently reversed a decision from the District of Delaware that invalidated a claim for obviousness-type double patenting (ODP), holding that a first-filed, first-issued, later-expiring claim cannot be invalidated for ODP based on a later-filed, later-issued, but earlier-expiring claim from the same family. In so doing, the court answered the question of whether a later-filed, later-issued patent in the same family can be an ODP reference against the first application in the family—it cannot. The court also clarified the scope of its prior ruling in In re Cellect, explaining that case answered a different question—the question of what expiration date should be used for an ODP analysis.