Another layer of complexity has been added to patent prosecution under the District Court of Michigan’s expanded interpretation of the obviousness type double patenting (“ODP”) doctrine[1].The district court held that a continuation application can, in certain circumstances, invalidate its earlier filed and earlier issued parent under ODP. If upheld, patent prosecutors must carefully consider the scope of the claims in a continuation application especially when the parent application/patent receives patent term adjustment (“PTA”) extending its expiration date.

Citing the Federal Circuit’s Gilead[2] decision, the district court stated “a court should look to the expiration dates not issuance dates to determine whether a patent can be used as the prior art patent under the [ODP] doctrine.”[3] The patent at issue (U.S. 7,339,149) is the parent of the reference patent (U.S. 7,402,786), i.e., the patent asserted against the ‘149 patent. Absent patent term extension (“PTA”), the ‘149 patent would be expected to expire at the same time as the continuation application, and the doctrine of ODP would not necessarily be implicated. The ‘149 patent, however, had 418 days of PTA, and thus, expired after its continuation application:

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The diagram above implies that the ‘149 patent and the ‘786 patent only have a common parent application, but in fact the ‘786 patent is a continuation of the ‘149 patent.

In explaining its holding, the district court quoted heavily from Gilead, which stated that “looking to the earliest expiration date [as opposed to the issuance date] of all the patents an inventor has on his invention and its obvious variants best fits and serves the purpose of the doctrine of double patenting.”[5] But the facts in Gilead were different from the fact pattern in this case because, inGilead, the target patent was filed later than the reference patent. However, in this case, the target patent, i.e., the ‘149 patent, was filed earlier than the reference patent. The Federal Circuit did not discuss the possibility of using filing dates for the purposes of determining whether a reference patent is properly used against a target patent in its Gilead decision.

The district court’s decision, if upheld, will mean patent prosecutors must think twice before filing a continuation application that could be used to later invalidate the parent application that contains PTA. Interestingly, during prosecution of the parent application, the continuation application will likely not be cited in an ODP rejection by the USPTO. Indeed, if the continuation application is filed after the parent application is allowed (but not issued), an information disclosure statement citing the continuation application may be necessary. But even then, the ODP rejection will necessarily be provisional because the continuation would not have been allowed at that point. In some scenarios, the continuation application may be filed after issuance of the parent application, in which case not even a provisional rejection will be made against the parent application. Thus, although the district court’s decision may be overruled, in the meantime, patent prosecutors must carefully consider claim scope in any continuation applications, particularly when the parent application contains PTA.