Protecting pharmaceutical exclusivity: Avoiding the hidden dangers of double patenting

Time is often money in the pharmaceutical industry, and this is particularly true regarding patents that protect the exclusivity of FDA-approved products. US patents have a term of 20 years. But because the FDA approval process for pharmaceuticals can take several years, federal law, specifically 35 U.S.C. § 156, allows restoration of time lost to regulatory approval by allowing patentees to apply for up to five years of patent term extension (PTE), which is added to the end of a patent term. Those additional years often coincide with peak sales of the approved drug, making the PTE period the most profitable—and meaning that properly protecting that PTE period can be worth billions of dollars. Because there is only one opportunity to obtain PTE, it is critical to not only select the right patent to extend, but also to make sure that the extension is securely protected.

Building an effective patent portfolio requires much more than just obtaining multiple issued patents. Careful planning is imperative. Typical patent strategy includes obtaining claims layered in scope and directed to various inventive aspects of a drug (composition, methods of use, formulation, etc.) in multiple patents filed at different R&D stages.

Multiple patents contribute to a robust portfolio; however, each patent that issues can potentially become a landmine to another, destroying the validity of claims under the legal doctrine known as “double patenting.”  Given the potential value of the extended patent term, particular care must be taken to avoid invalidation of the PTE patent.

Avoiding double patenting landmines

Double patenting is a statutorily created and judicially interpreted doctrine that seeks to prevent the granting of two patents for a single invention to the same proprietor. Thus, under 35 U.S.C. § 101, a patentee is precluded from obtaining more than one patent on the same invention. In the US, courts have furthered this “to preclude a second patent on an invention which would have been obvious from the subject matter of the claims in the first patent, in light of the prior art.” The judicially created doctrine of double patenting is known as non-statutory double patenting, or obviousness-type double patenting (ODP). ODP can put any patent in jeopardy, whether in the same or different family. But, when the patents are in the same family (continuations, for example), the danger of an ODP invalidation is easily overlooked.

For example, it is not uncommon for a patentee to pursue and obtain broad claims in the first-filed patent in the family, and then after a particular candidate is identified, pursue more specific claims to the candidate in a continuing application. For example, an applicant might pursue claims that recite a genus of small molecules having similar structure in a first patent, then pursue claims directed to a particular compound in a continuing application. Or an applicant might pursue claims reciting one or more complementary determining regions of an antibody in a first patent, then pursue claims to a full antibody construct in a continuing application.

The first-filed patent in a family often takes the longest amount of time for prosecution and is the most likely to receive patent term adjustment (PTA). PTA is separate from PTE, and is a means by which the United States Patent and Trademark Office (USPTO) seeks to compensate the patentee for patent term (the 20-year term) that was lost due to USPTO delays that occurred during prosecution. After a first-filed patent is allowed by the USPTO, a continuing application with narrower claims typically progresses more swiftly through prosecution and does not receive PTA. The result is that the first patent has a later expiration date than the subsequently filed patent with narrower claims. Importantly, while the first patent application was prosecuted, no second patent application existed to form the basis of an ODP rejection by the USPTO.  Thus, it is easy for patentees to overlook the danger to the first application that is subsequently created by the second patent.

Sometimes a first issued patent is an attractive choice for PTE because it is eligible for the greatest amount of PTE term. PTE begins to accrue after an investigational new drug (IND) application is filed, but only for patents that have issued; thus a subsequent patent that issued only after the regulatory review period began will be eligible for fewer days of PTE. Moreover, applying PTE to a first patent that has PTA may be further attractive because stacking PTE on a patent with PTA would push the loss of exclusivity date further into the future.

However, that first patent may be particularly vulnerable to ODP. Narrower claims in the continuing patent would likely anticipate or render obvious broader claims in the parent patent. This danger is typically not uncovered during patent prosecution when no double patenting rejection is raised by the USPTO during prosecution of either patent application (not in the parent because it was the only patent in prosecution at the time, and not in the continuing application because the claims are narrower than the parent).

It’s not too late: Double patenting remedies

Careful planning of a patent portfolio and PTE strategy to avoid double patenting issues is highly recommended at the outset, before any patent applications are filed. However, in certain circumstances, remedial actions may be available to alleviate or eliminate double patenting issues that have arisen. An ODP rejection by the USPTO or an ODP challenge to validity by a third party may be overcome by a timely filed terminal disclaimer  A terminal disclaimer is a legal document that disclaims the term of a first patent that extends beyond the term of a second patent, i.e., the reference patent upon which the ODP challenge is based. Importantly, a terminal disclaimer in a patent over a reference patent immunizes the first patent against ODP based on that reference patent (but not vice versa).

It is important to note that there is a limited time for filing a terminal disclaimer to obtain such immunity. A terminal disclaimer that is filed after a reference patent expires is ineffective. Thus, a PTE patent facing an ODP challenge based on an expired reference patent may be defenseless. However, if a terminal disclaimer is filed in the PTE patent just one day before expiration of the reference patent, then the PTE patent would effectively be immunized against that reference patent.

Filing a terminal disclaimer is sometimes a difficult decision to make because it can result in a reduction of patent term. However, filing a terminal disclaimer may be necessary to save the validity of PTE patent claims. Consideration of the potential need for a terminal disclaimer and resulting change in patent term should be performed as part of the PTE patent selection process. Although a terminal disclaimer may shorten term, it would be worse to waste PTE on a patent whose claims are vulnerable to ODP and is without a remedy. Moreover, in some circumstances, such as when available PTE is shortened by the statutory 14-year cap, the filing of a terminal disclaimer would result in no net loss of patent term because the lost PTA would be entirely replaced by PTE. Importantly, in order to fully swap PTE for PTA, a terminal disclaimer must be filed before a PTE certificate issues. It could be tragic to miss such opportunities.

In conclusion, strategy for an entire patent portfolio, including the patent for which to apply for PTE, should be developed before a first application is filed. It is best to plan for the PTE patent to avoid ODP issues. All prosecution decisions should be made while mindful of potential consequences to the PTE patent. In any event, should ODP issues arise, mitigation strategies are available, but there may be limited windows to take remedial action.

About the authors

Robert N. Sahr, Shareholder, Wolf Greenfield. He develops strategies for life science companies to maximize exclusivity for therapeutic and diagnostic products.

Kady S. Bruce, PhD, Associate, Wolf Greenfield. She counsels clients in biotechnology patent prosecution and has extensive knowledge in the areas of neuroscience, biology, sensory systems, optical physics and biomechanical engineering.