The Federal Circuit has recently departed from long-established law on obviousness-type double patenting. The decision, in Sun Pharmaceutical Industries, Ltd. v. Eli Lilly and Company, creates risks for patent owners who obtain patents that are related to each other, especially where those patents are continuations-in-part of an earlier application.

Double-Patenting Basics

Under U.S. law, the Patent and Trademark Office is supposed to issue only one patent per invention. 35 U.S.C. § 101. Thus, the PTO should reject a claim in a pending patent application where that claim is identical to a claim in a previously issued patent—even when the application and the patent have the same owner and same inventors. Such a rejection is called a “statutory double-patenting” rejection.

When a later-pending claim is not identical to a claim previously issued to the same applicant but is obvious over that claim, the PTO is supposed to make an “obviousness-type double-patenting” rejection. Because the doctrine of obviousness-type double patenting was developed by the courts and is not based on the patent statute, it is sometimes called “non-statutory double patenting.”

If the PTO fails to make either a statutory or obviousness-type double-patenting rejection when it should have, a court can find the later-issued claim unenforceable if the later claim is the same as or obvious over the earlier-issued claim.

Deciding whether the later claims are obvious over the earlier claims requires an analysis similar to the standard obviousness analysis, where claims are determined to be obvious or non-obvious over the prior art.

In the standard obviousness analysis, you identify the differences between the claims in a patent application and the closest prior art reference—typically a prior product, a patent, a scholarly article or other writing—and then determine whether these differences would have been obvious to a person of ordinary skill in the field, in view of what else is taught and suggested by the rest of the prior art.

Obviousness-type double patenting calls for the same analysis, except that you isolate the differences between the later claim and the earlier claim of the same applicant. Then you determine whether these differences would have been obvious to a person of ordinary skill in the field in view of what is taught and suggested by the rest of the prior art.

It had long been established that, in determining whether the later claims would have been obvious over the earlier claims, “the patent disclosure may not be used as prior art.” See, e.g., Application of Vogel, 422 F.2d 438, 441 (CCPA 1970).

To overcome an obviousness-type double-patenting rejection, a patent applicant can, of course, argue that the later claims would not have been obvious over the earlier claims. Alternatively, a patent applicant—or, in some cases, a patentee—can file a terminal disclaimer for the later patent.

A terminal disclaimer is a binding statement that the later patent will expire no later than the earlier patent and that the later patent will be enforceable only as long as it and the earlier patent are commonly owned. (A terminal disclaimer cannot be used to overcome a statutory double-patenting rejection, as a later claim should never be allowed where it is identical to an earlier-issued claim.)

What happened in Sun Pharmaceuticals?

Eli Lilly filed an application that disclosed a new compound, gemcitabine, for use in treating viral infections. Lilly filed subsequent applications that claimed priority back to the first application and disclosed additional subject matter, namely the use of gemcitabine to treat cancer. Apparently, between the filing of the earlier application and the filing of the two later applications, Lilly discovered this additional use for the compound.

Although the two later applications had identical disclosures to each other, they had claims directed to different inventions. One of these two later applications claimed gemcitabine and the method of using it to treat viral infections; this application was the first to result in an issued patent.

The second of these two applications claimed the use of gemcitabine to treat cancer. The PTO did not make an obviousness-type double-patenting rejection, and thus no terminal disclaimer was filed for the second patent, and the second patent was set to expire 2½ years after the first patent.

In a suit between Lilly and Sun Pharmaceuticals arising from Sun’s Abbreviated New Drug Application, a federal court found the second patent invalid for obviousness-type double patenting in view of the first patent. Since Lilly’s first patent had expired by the time of the appeal, filing a terminal disclaimer for the second patent would have effectively ended the litigation.

On July 28, 2010, in affirming the lower court’s decision, a three-judge panel of the Federal Circuit ruled that it was proper to rely not only on the claims of the first patent but also on its disclosure, including its disclosure that gemcitabine may be used to treat cancer, even though the first patent had not claimed this use.

By ruling that it could combine the claims of the first patent with the disclosure of the first patent, the court made the finding of obviousness-type double patenting unavoidable. Thus, Lilly was penalized for including in the first patent the disclosure that gemcitabine could be used to treat not only viral infections but cancer.

If Lilly had left the disclosure of the cancer treatment out of the first patent, the court may not have been able to find that the later claims were obvious over the earlier claims. Lilly asked the full bench of the Federal Circuit to rehear its appeal.

The Dissent

On November 1, 2010, in a 5-4 decision, the Federal Circuit refused to grant a rehearing, but the dissent was biting: “Until recently the law of double patenting was clear, but it has become distorted by divergent statements, leading to this flawed ruling.”

The dissent charged that the panel’s ruling misunderstood or misapplied precedent that held that the disclosure of the earlier patent may only be used to interpret the claims of the earlier patent. The prior case law recognized only one exception to this rule: When the earlier patent discloses a single use for a compound, claims in the later patent directed to that use may be obvious over the claims in the earlier patent directed to the compound. See, e.g., Geneva Pharmaceuticals, Inc. v. GlaxoSmithKline PLC, 349 F.3d 1373 (Fed. Cir. 2003).

According to the dissent, the panel departed from this precedent, by using the earlier patent’s disclosure for more than just interpreting that patent’s claims. Instead, the panel used that disclosure for its teaching that gemcitabine could be used to treat cancer—a use that may not have been obvious for a drug developed to treat viral infections.

And the holding of Geneva Pharmaceuticals—where the later claim, directed to the only use described in the earlier patent, was found to be obvious over the claims of the earlier patent—did not support the panel’s decision, because Lilly’s earlier patent disclosed two different uses for gemcitabine.

The Impact

In general, obviousness-type double patenting should become less of a concern in the future. Whereas patents filed prior to 1995 generally lasted 17 years from their issue date, patents filed since 1995 last 20 years from their earliest effective filing date. Since patents in the latter category that claim priority back to the same application tend to expire at the same time, the effect of terminal disclaimers on such patents is much less than the effect on patents in the former category.

As more and more patents filed before 1995 expire, the instances of patents in the same patent family expiring years apart from each other should become increasingly rare.

Nevertheless, patents filed today can obtain patent term adjustments (which are granted for delays in the PTO in examining a patent application). As a consequence, patents claiming priority from the same application can sometimes have different expiration dates and accordingly can be affected by terminal disclaimers filed to overcome obviousness-type double-patenting rejections.

Thus, it is sometimes important for applicants to fight obviousness-type double-patenting rejections in order to avoid having to file terminal disclaimers.

Complications can arise where a patent is the target of obviousness-type double–patenting attacks not while it is pending in the PTO but only later, in a federal court. In such a situation, the patent owner may scramble to file a terminal disclaimer in order to ward off such a defense, but doing so after a patent has issued can be problematic. See, e.g., Boehringer Ingelheim International GmbH v. Barr Laboratories, Inc., 592 F.3d 1340 (Fed. Cir. 2010).

In view of such complications, it may be better for applicants to consider their vulnerability to obviousness-type double-patenting concerns while a patent is still pending in the PTO instead of waiting to see whether the defense is raised in litigation.

Also, in view of the holding in Sun Pharmaceuticals, patent applicants should be cautious if they discover a new use for a compound after filing a patent application disclosing the compound and an original use for the compound. If a continuation-in-part application is filed adding the new use to the disclosure, the patent applicant should consider refraining from claiming therein the compound and the original use.

The applicant may be better served by continuing to pursue the compound and the original use in the original application or in a straight continuation application. Otherwise, the applicant may find itself in a situation like Eli Lilly where the new disclosure may be used against it when trying to claim the new use.

The doctrine of obviousness-type double patenting was developed at a time when patents in the same family would often have expiration dates many years apart from each other, and the doctrine was developed to address potential abuses that could arise from such disparate expiration dates.

Today, when patents in the same patent family generally expire at the same time, such abuses should become uncommon. Nevertheless, obviousness-type double patenting is still a viable issue that can create subtle complications that can trip up patent owners and result in the invalidation of patents.