Chapter §12.01 Introduction

• Jurisdiction: United States

§12.01 Introduction

"Double patenting" is a basis for rejecting application claims in the U.S. Patent and Trademark Office (USPTO) or for invalidating claims of an issued patent in the federal courts or (presumably) in a post-grant review at the USPTO. The essence of the double patenting doctrine is that the same entity (inventor or assignee) may not obtain two (or more) patents on a given claimed invention.¹ The policy concern underlying the double patenting doctrine is not that that entity is patenting something that another entity already invented. Rather, the traditional policy concern underlying the double patenting prohibition is that the entity is seeking to improperly extend the duration of its right to exclude others from practicing its invention by procuring more than one patent on it.²

Double patenting examines whether the claims of the entity's two patents (or of its patent and its pending application) are patentably distinct from one another. Patentability over the prior art is not at issue. The double patenting analysis is conceptually different from determining whether the claimed invention is anticipated or would have been obvious in view of the prior art.³ Thus double patenting merits a separate chapter in this treatise.

In the USPTO, double patenting is a prohibition applied against a patent applicant who attempts to obtain two (or more) patents on the same invention, or two (or more) patents that claim patentably indistinct variants of the same invention. For example, consider an inventor who applies for and is granted a patent by the USPTO. The patent claims invention X. The inventor has filed a second patent application (typically, but not always, while the inventor's first application was still pending).⁴ If the second application purports to claim the same invention X, or an obvious variant of invention X, the USPTO examiner should reject the claims of the second application as violating the prohibition on double patenting.⁵

Double patenting is also applied by the federal courts to invalidate patents when it is determined that the owner of an issued patent improperly obtained a second patent on the same invention or its obvious variant.⁶ In the litigation context, double patenting is often charged against pharmaceutical firms allegedly engaged in "evergreening;" that is, obtaining a series of patents on closely related drug inventions in an attempt to improperly prolong the patent life of the firm's products.⁷ For example, the...