Does the Amgen Case Raise the Bar for Enablement?

Does the Federal Circuit’s February 2021 Amgen v. Sanofi decision signal an evolving skepticism by the court of patent claims directed to antibodies and other complex molecules? In Amgen v. Sanofi, the Federal Circuit found in favor of Sanofi holding that Amgen’s patent did not fairly describe how to make and use the full scope of claims reciting antibodies described solely by their function and not their structure. In this episode of Choate’s Life Sciences Insights podcast series, Eric Marandett and Rolando Medina review Amgen v. Sanofi and discuss strategies for how to successfully describe, claim, and assert antibody patents in the evolving legal landscape.


Welcome to Choate’s Life Sciences Insights. A podcast series hosted by our intellectual property, litigation, and corporate attorneys covering trending topics at the intersection of science and law.

Rolando Medina: Hi, I am Rolando Medina, a partner in the Patent Group at Choate, Hall & Stewart.  I am here with my partner, Eric Marandett, co-chair of the IP Litigation Group.

Eric Marandett: Hi, everybody. 

RM: Today we are discussing Amgen v. Sanofi decided by the Federal Circuit on February 11, 2021.  Back in 2014, Amgen filed this lawsuit against Sanofi and Regeneron asserting an infringement of several patents by the product Praluent which is a therapeutic antibody product.  Amgen’s patents relate to antibodies that reduce low density lipoprotein cholesterol or LDL cholesterol or bad cholesterol which can lead to cardiovascular disease.  Biologically your liver cells have on their surface receptors that bind to LDL and help to clear LDL from the blood.  However, your body also produces a protein called PCSK9.  PCSK9 binds to these LDL receptors eventually leading to their destruction.  Amgen developed antibodies that bind to PCSK9, preventing it from binding to these receptors thus allowing the LDL receptors to effectively clear LDL from the blood.  Amgen’s patents claim such antibodies but solely by reciting their function.  Specifically, the claims recite antibodies that (1) bind to specific amino acid residues of PCSK9 and (2) block the binding of PCSK9 to LDL receptors.  Following a jury trial, the District Court found that Amgen’s patents were not invalid for lacking written description or enablement.  Sanofi appealed and the Federal Circuit issued a decision back on October 27, 2017.  There were a lot of issues in that appeal but the Federal Circuit reversed the District Court’s finding that the patents were not invalid for lacking written description or enablement.  Of note, the Federal Circuit also refuted the conventional newly characterized antigen test for antibodies which up until that point had allowed antibodies to be claimed functionally if the antigen were fully described.  The Federal Circuit remanded back to the District Court.  The jury again found that Sanofi did not prove the claims were invalid for written description or enablement.  The District Court granted judgment as a matter of law holding, however, that Amgen’s claims were invalid for lack of enablement.  Amgen then appealed and the Federal Circuit in this 2021 decision affirmed the finding and validity for lack of enablement.  The Court and the factors, being the proper standard for enablement but emphasized in this case -- cases like these -- were claims recite broad functional language.  There’s actually a pretty high hurdle to satisfy the enablement requirement and Amgen here did not meet that threshold.  So, Eric, turning to you.  Do you think that this case and the holding is an aberration or do you think it’s a trend in terms of restricting the scope of antibody claims?

EM: It is definitely not an aberration, it is a trend.  It is a trend though that I would say is not specific to antibodies.  It is broader than that.  There is actually a statement in the Federal Circuit’s opinion that I think is particularly instructive on where the law is going.  The Court said while functional claim limitations are not necessarily precluded in claims that meet the enablement requirement, such limitations pose high hurdles in fulfilling the enablement requirement for claims with broad functional language.  In this case, that was applied to antibodies, but the Court was relying on a series of prior cases.  First, the Wyeth case about rapamycin analogs that was back in 2013.  Then in 2019, the Enzo v. Roche case that dealt with polynucleotides with certain hybridization features and the Idenix Gilead case that was nucleoside compounds and in each of those cases there was a finding of lack of enablement where the claims were written in functional language.  So, functional language defines what was the structure of the particular compound that was at issue, only in this case it is antibodies but the others, it’s not.  So I think what you are seeing is the Federal Circuit moving away from and being highly skeptical of broad classes of compounds that are defined not by particular structural features but instead by functional language and that really cuts across different kinds of compounds and is definitely a trend in the law.  I think another interesting characteristic of this is these cases all, with the exception of the Gilead case which had a written description element as well, claims written validated on both grounds but the rest of these cases all are enablement cases where really the enablement and written description standard is being conflated somewhat.  It’s talking about whether you’ve enabled the full scope but yet often the issue is there is a small number of examples that fall within a subset of a genus.  That sounds a lot more like written descriptions.  So, there is sort of skepticism in both areas of the law and definitely, a trend that bears watching not just for antibody patents but really for any chemical or biologic compounds.  So, from a prosecution perspective turning it back to you, looking at this case and this line of cases, what kind of strategies would you advise?  How do you tell your clients what to do?

RM: So from a prosecution strategy or a prosecution standpoint, what’s definitely is clear is that claiming antibodies solely by function will not be allowable.  So, going forward the strategy will actually need to focus on describing and claiming the antibody itself.  This is borne from the 2007 decision where the Federal Circuit shot down the newly characterized antigen test stating that this test effectively allowed patentees to claim antibodies by describing something that is not the invention and that is the antigen.  And the Federal Circuit 2021 decision here also emphasized this broad functional language of the claims again focusing on claims that reference the antigen, namely antibodies binding to the antigen, and not defining the antibodies themselves.  So, from a prosecution strategy perspective, we should describe antibodies themselves as thoroughly as possible such as providing as many examples of antibodies as we can with the idea that describing a sufficient number may support a genus claim down the road.  We may, however, currently need to focus on CDR sequences, consensus sequences to the extent possible again to build out the representative numbers of those antibodies that we can.  This is not to say that we should dispense with functional characteristics entirely.  We should still include as many of those as possible such as epitope mapping or binding activity.  While it’s clear these functional limitations on their own won’t support a claim, they may in fact support claims reciting a combination of antibody structure and function limitations and describing as many as we can demonstrate this necessary correlation between structure and function.  As we know case law is always evolving and what’s patentable today may not be patentable tomorrow and vice versa, so we should always include as many backup strategies as possible.  With that Eric from a litigation perspective sitting here today what is your view on asserting antibody patents?

EM: So I am going to give a classic litigator’s answer to that and that is, it depends.  I certainly think that these claims are still worth asserting and to the point that you just made, the law is continuously evolving and candidly these cases don’t provide a sort of clear task that can be readily applied to a different set of facts because they always turn on what is too much experimentation and as a result, the answer often is idiosyncratic to the particular disclosure and field that issue.  I think we should always be pushing the envelope in litigation and to the extent that in prosecution some of the fixes that you just described have happened, I think the odds of being successful in asserting these patents goes up.  But that said, I think we should continue to test the waters and the real difference isn’t so much in whether you will assert them but how do we advise our clients on risk and I think it is a certainty that moving forward in the landscape of where we see the case law today, we’re all going to be advising our clients that there is definitely greater risk if you’ve got antibodies or any compound for that matter that’s defined not purely by structure but by some kind of functional limitation. Whether you can actually feel good about enforcing that is going to depend a little bit on how the evidence will shake out in terms of how much experimentation really is necessary to get to that class of compound and how uncertain is the art and that both depends on the particular set of facts and also evolves over time to a certain extent.  The state of the art today on antibodies is different than the state of the art will be in five years from now so there is a lot that is going to change and as a result, I think we are going to see much more development of this case law. 

RM: Great.  Thank you so much, Eric.  This has been very informative.  Thanks for joining today.

EM: My pleasure. Thanks very much!


The information presented in this recording is for informational purposes only.  It does not constitute legal advice for a specific situation.  If you wish to obtain legal advice, you should retain an attorney and explain the facts of your particular situation.