Often when an examiner rejects claims of a patent application during examination, our first reaction is to argue against the examiner’s position. We then proceed to place substantial arguments (often every argument we can think of) on the record in an effort to obtain the broadest claims we can. Sometimes, we are successful and we obtain a patent with broad claims, at least on their face. However, what we put in writing in the US can substantially limit the scope of the claims (due to what is known as “file wrapper estoppel”). This was shown in the recent decision of the Federal Circuit in Biogen Idec, Inc. v. GlaxoSmithKline LLC (Fed. Cir. 2013).


Biogen and Genentech produced an antibody that bound to a loop of the CD20 protein that is displayed on the surface of cells, such as B cell lymphoma cells. This antibody, known as rituximab (Rituxan®/MabThera®), was approved for the treatment of the blood cancer, Non-Hodgkin’s Lymphoma. Subsequently, scientists found that rituximab could be used to treat another blood cancer, i.e., chronic lymphocytic leukemia (CLL), and Biogen filed a patent application based on this finding. This patent issued as US Patent No. 7,682,612, with claim 1 reciting:

A method of treating chronic lymphocytic leukemia in a human patient, comprising administering an anti-CD20 antibody to the patient in an amount effective to treat the chronic lymphocytic leukemia, wherein the method does not include treatment with a radiolabeled anti-CD20 antibody.

At the time rituximab was produced and for some time afterwards, it was thought that only the one loop of CD20 was displayed on the surface of cells. However, scientists subsequently found that there was another smaller loop of C20 displayed on cells, e.g., cancer cells. GenMab and GlaxoSmithKline (Glaxo) then developed ofatumumab (Arzerra®), which bound to this smaller loop. Ofatumumab was approved for treatment of CLL and immediately after this approval, Biogen sued Glaxo for infringement of US7,682,612.

The issue

US7,682,612 underwent extensive prosecution, with at least nine Office Actions issued and written responses to those Actions filed. One of the issues raised by the examiner during prosecution was that the while the specification enabled rituximab and antibodies having substantially the same structure (e.g., monoclonal antibody 2B8), it did not enable “any and all anti-CD20 antibodies, no matter the specificity or affinity for the specific epitope on the circulating tumor cells”. The examiner asserted that the application was silent concerning the specificity and affinity that would be necessary for other anti-CD20 antibodies. In response to the rejection, Biogen stated that:

“[E]ven though antibodies directed to the same antigen might have different affinities and functional characteristics, one of skill in the art could readily identify an antibody that binds to CD20 with similar affinity and specificity as does RITUXAN® using techniques that are well known in the art. With that knowledge in hand, the skilled artisan could readily produce anti-CD20 antibodies using similar techniques, and screen such antibodies for those having an affinity and functional activity similar to RITUXAN®”.

The examiner then withdrew the rejection and the application proceeded to allowance and grant.

After Biogen sued Glaxo, the District Court conducted a Markman hearing to construe several terms in the claims, including the term "anti-CD20 antibody”. Biogen argued that this term should be read broadly (as it appears to be quite broad on its face). However, the District Court held that prosecution history disclaimer applied because Biogen had limited the term to overcome the examiner's enablement rejection (i.e., their response to the examiner’s objection stated that antibodies with similar affinity and specificity to rituximab were enabled by the specification). On this basis, the Court construed the term to mean "rituximab and antibodies that bind to the same epitope of the CD20 antigen with similar affinity and specificity as rituximab”. Since ofatumumab does not bind to CD20 with a similar affinity and specificity as rituximab (e.g., it binds to a different epitope), Glaxo was held not to infringe any of the claims of US7,682,612.

On appeal, the Court held that “if an applicant chooses, she can challenge an examiner’s characterization in order to avoid any chance for disclaimer, but the applicants in this case did not directly challenge the examiner’s characterization”. The Court also held that "[r]ather than challenging the examiner’s understanding of the crucial terms, the applicants argued that the specification was enabling for anti-CD20 antibodies with similar affinity and specificity as Rituxan®”. Accordingly, the Federal Circuit affirmed the District Court’s claim construction and held that the patent was not infringed.

Lesson to be learned

By arguing for broader scope of their claims in the manner in which they did, Biogen essentially sacrificed the same scope as they would have if they had amended their claims in the manner the examiner wanted them to during prosecution. This means that they obtained claims that, while providing valuable protection against biosimilars and similar competitive products, does not actually capture a competitor’s product. Perhaps a different outcome may have been reached if Biogen had argued that they were the first to show that anti-CD20 antibodies could be used to treat CLL and that C20 antibodies other than rituximab were known at the priority date of the application, such as the 2H7 antibody and chimeric forms thereof (which form the basis for Genentech’s ocrelizumab), antibody 1F5 and antibody B1 (the antibody component of Bexxar®).

This case highlights several important issues:

  • The scope of claims granted in a US patent are not always as they seem, and what is said in writing can substantially change the scope of the claims. This can have dramatic effects on your freedom-to-operate and also on your ability to capture competitors.
  • While interviewing an examiner (perhaps several times) may seem like an expensive option at the time, it can substantially reduce the arguments placed on the written record and reduce the risk of file wrapper estoppel. Clearly, as in the present case, this may actually save you (or make you) substantial revenue in the future if you manage to capture a competitor with your patent.
  • We must always be careful about what we say in writing. We can end up inadvertently sacrificing valuable claim scope with what seems to be an innocuous comment or even what seems a strong argument for patentability. If we are arguing for broad claims, we must be careful to always couch our arguments in terms of the entire scope of the claims.
  • Fighting for claim scope that is of no commercial benefit to you may actually have an adverse effect on the scope that is important to you. While it did not happen in this case, by arguing for broad claims, it is possible to sacrifice scope required to protect your own invention. Accordingly, we (both the applicant and their attorneys) must always have a clear idea of the commercial embodiment and ensure that what we are arguing for does not jeopardise claim scope protecting that embodiment. Sometimes, it may even be worthwhile sacrificing some scope without argument, simply to ensure your commercial activities are protected.