Antibody-Directed Inventions Require Robust Written Descriptions and Carefully Drafted Claims

In a recently unsealed opinion from the District of Delaware, Judge Dyk of the Federal Circuit sitting by designation, held a patent in the “inherently unpredictable” field of antibodies invalid on summary judgment for failing to satisfy the enablement requirement.  Baxalta Inc. v. Genentech Inc. Delaware Opinion, Case No. 17-cv-509-TBD (D. Del. Jan. 13, 2022).  The accused product was HEMLIBRA® directed to treating hemophilia A with antibody emicizumab-kxwh or ACE910.  Baxalta sued in 2017, asserting U.S. Patent No. 7,033,590 which is titled “Factor IX/Factor IXA Activating Antibodies and Antibody Derivatives.”  The patent claimed antibodies that promote coagulation factor IXa absent factor VIII.

Where patents are “directed to a genus that was claimed broadly in terms of functionality,” both in terms of what the antibodies bind to and what effect they have, but the effective antibodies are a small subset of a large group which may meet the binding functional language, enablement and written description issues are likely.  Here, the genus included millions of candidate antibodies, and the patent disclosed only eleven working examples, none of which were developed into a therapeutic product.  The court found it “significant that the patent does not remotely enable the accused antibody,” which is far more effective than any of the working examples.  The accused antibody’s structure as a bispecific humanized antibody was the key to its success, yet none of the working examples disclosed either a bispecific or humanized antibody.  Nor did the patent provide any guidance as to which features of the disclosed antibodies cause them to accomplish the claimed functions.  Importantly, Judge Dyk cited evidence that “if a person of ordinary skill in the art . . . started with the genus of antibodies and antibody fragments that bind to Factor IX or IXa, only a very tiny percentage of those will meet the claims’ functional limitation that the antibody or antibody fragment increase the procoagulant activity of Factor IXa.”

In other antibody patent cases in the past year, the Federal Circuit has stated that specific antibodies that do what the patent claims are important to written description and enablement, and merely describing what the antibody binds to may not be enough.  In Baxalta, and other similar cases, despite the fact that routine experimentation could disclose which antibodies were effective, the experimentation was undue as the need to screen 10,000s or more antibodies resulted in an invalidating “search for a needle in a haystack.”