Baxalta v. Genentech: The Latest Case In Patenting Functionally Claimed Antibodies

By Jonathan B. (J.B.) Fitzgerald, Ph.D., Snell & Wilmer L.L.P.

On Sept. 20, 2023, in Baxalta v. Genentech (Baxalta),¹ the Federal Circuit invalidated patent claims directed to functionally claimed antibodies, finding that they failed to satisfy the enablement requirement. In particular, the Federal Circuit found that there was not enough description in the patent such that a person of skill in the art can make and use the claimed antibodies without undue experimentation.

The ruling in the Baxalta case follows the Supreme Court’s ruling in Amgen v. Sanofi (Amgen)² on May 18, 2023. Similar to Baxalta, in Amgen the Supreme Court also invalidated functionally claimed antibodies under the enablement requirement. The Baxalta case may reveal the potential ongoing vulnerability to invalidity findings under the enablement requirement of functionally claimed antibodies. This paper will explore this potential ongoing vulnerability to functionally claimed antibodies through:

1. describing the overlap between the claims at issue in the Baxalta and Amgen cases;
2. reviewing the Federal Circuit’s invalidity finding of the claims at issue in the Baxalta case;
3. exploring the overlapping reasoning with that of the Amgen court that the Baxalta court;
4. describing the Baxalta court’s application of the “full scope” enablement test; and
5. forecasting the potential vulnerability of functionally claimed antibodies to invalidity findings under the enablement requirement.

The Overlap Between Claims At Issue In The Baxalta And Amgen Cases

Baxalta is the owner of U.S. Patent No. 7,033,590 (the ‘590 patent), which was at issue in the Baxalta case. The ‘590 patent is directed to antibodies that can be used to treat clotting disorders to increase procoagulant activity by binding to the specific clotting factors IX and IXa. Claim 1 of the ’590 is representative of the antibodies that Baxalta was attempting to enforce.

Claim 1 of the '590 patent: An isolated antibody…that binds Factor IX or Factor IXa and increases procoagulant activity of Factor IXa.

Thus, claim 1 of the ‘590 patent attempted to protect the antibody according to its functional properties of binding to a specific clotting factor and carrying out the function of increasing procoagulant activity. Notably, claim 1 does not describe structural features of the claimed antibody.

Claim 1 of the ‘590 patent is similar to the antibody claims at issue in the Amgen case. In Amgen, the function of the antibodies was to reduce elevated levels in the bloodstream of low-density lipoprotein (LDL), a form of cholesterol that has been linked to heart disease. The antibodies carry out this function by inhibiting the enzyme PCSK9, an enzyme that functions to inhibit removal of LDL from the bloodstream through binding to the LDL receptor (LDLR). A representative claim was claim 1 of U.S. Patent No. 8,859,741 patent (the ‘741 patent).

Claim 1 of the '741 patent: An isolated…antibody that binds to PCSK9…wherein the…antibody blocks binding of PCSK9 to LDLR.

Thus, claim 1 of the ‘741 patent claimed the antibody according to its dual functional properties of binding to PCSK9 and blocking binding of PCSK9 to LDLR.

Comparing this claim to claim 1 of the ‘590 patent reveals significant overlap. In both claims, the antibodies are claimed according to their dual functional roles of the ability to (i) carry out a binding event, either binding to Factors IX/IXa (Baxalta) or binding to PCSK9 (Amgen), and (ii) effect a downstream event as a result of antibody binding, either increasing procoagulant activity (Baxalta) or blocking binding of PCSK9 to LDLR (Amgen).

The Federal Circuit’s Finding That Baxalta’s Dual Functional Antibody Claims Were Not Enabled

The standard for meeting the enablement requirement is that the patent must teach a person of skill in the art to make and use the claimed invention without engaging in undue experimentation. The Baxalta court concluded that the ‘590 patent failed to meet this standard because the recited functions of (i) binding to Factor IX/IXa and (ii) increasing the procoagulant activity of Factor IXa covered potentially millions of antibodies. As a result, according to the Federal Circuit, the disclosure in the patent of sequences of 11 antibodies capable of carrying out the dual functions of (i) and (ii) was insufficient to satisfy the enablement requirement.

The ‘590 patent did describe a method of identifying additional antibodies covered by the claims (a “road map”), which included immunizing mice to induce antibody production and testing the antibodies to determine if they bind Factor IX/IXa and increase procoagulant activity. However, the court concluded that this road map was insufficient to satisfy the enablement requirement because it was nothing more than an invitation to engage in a trial-and-error process to identify antibodies covered by the claims.

According to the Baxalta court, the ‘590 patent also failed to describe any structural features that are common to antibodies capable of carrying out the dual functions described in the claims. For example, the ‘590 patent did not describe any structural features that were common to the 11 disclosed antibodies. Moreover, the ‘590 patent did not provide any guidance as to why certain antibodies that are screened using its road map perform the functions described in the claims and why certain screened antibodies fail to perform these functions.

For these reasons, the Baxalta court found that the dual function antibody claims failed to meet the enablement requirement.

The Baxalta Court Applied Similar Reasoning As That Of The Amgen Court To Invalidate The Claims

The Baxalta court applied similar reasoning to that of the Amgen court to invalidate the functionally claimed antibodies at issue. In fact, the Baxalta court concluded that the “facts” in its case were “materially indistinguishable from those in Amgen.”

Notably, the Baxalta court equated the road map described in the ‘590 patent to disclosures in Amgen’s ‘741 patent, which described well-established screening methods that could be used to identify antibodies that carry out the dual functions described in Amgen’s claims. The Baxalta court followed the lead of the Amgen court, concluding that the road map, like the Amgen’s screening methods, was nothing more than an invitation to engage in experimentation, which is insufficient to satisfy the enablement requirement.

Additionally, the Baxalta court equated the failure of Baxalta’s ‘590 patent to provide guidance regarding structural features that are common to the functionally claimed antibodies with a similar failure in the Amgen case. Amgen’s ‘741 patent describes a method known as “conservative substitution.” In this method, amino acid sequences (the fundamental structural units that make up antibodies) on antibodies are substituted with other amino acids. After substitution, testing is performed to determine which amino acid sequences are important for carrying out the functional properties described in the claims. The Amgen court suggested that although such experimentation may identify common structural features of antibodies capable of carrying out the functions described in the claims, it was still nothing more than an invitation to experiment.

Similarly, the Baxalta court found that nothing in Baxalta’s ‘590 patent disclosed common structural features of antibodies capable of carrying the claimed functional roles. Rather, similarly to the ‘741 patent, the ‘590 patent only described potential experiments that would result in creating a wide range of candidate antibodies that could be tested. As such, consistent with the findings in Amgen, the Baxalta court concluded that the ‘590 patent failed to describe any common structural features on the class of antibodies that would fall within the scope of the dual function claims at issue in the case.

The Baxalta Court Applied The “Full Scope” Enablement Test

The Baxalta court reiterated that the enablement standard is the “full scope” test described in Amgen: the patent must “enable the ‘full scope’ of the invention as defined by the claims.”  Under this standard, the patent must teach a person of skill in the art to make and use the “full scope” of the claimed invention, without undue experimentation.

In applying this standard to the claims at issue in the Baxalta case, the court concluded that the guidance provided in Baxalta’s ‘741 patent fell short of enabling what it concluded would be millions of antibodies potentially capable of carrying out the dual functions described in the claims. In other words, there was nothing in the ‘741 patent that “enabled” all of the potentially millions of antibodies that might be capable of (i) binding to Factor IX/IXa and (ii) increasing the procoagulant activity of Factor IXa.

The Baxalta court ultimately concluded that the ‘741 patent described nothing more than a trial-and-error process, which gave the public with no superior guidance to make and use the claimed antibodies than the guidance the inventors had when they set out to discover the antibodies. As a result, Baxalta could not claim exclusive right to the claimed antibodies because their full scope was not enabled.

The Potential Ongoing Vulnerability To Invalidity Challenges For Functionally Claimed Antibodies Under The Enablement Requirement

In Amgen, the Supreme Court invalided functionally claimed antibodies for failing to meet the enablement requirement. In Baxalta, the Federal Circuit reviewed claims that were similar to those at issue in the Amgen case. Upon its review, the Baxalta court applied the same reasoning and came to the same invalidity finding under the enablement standard as that of the Amgen court.

Although, under precedent, the Baxalta ruling may have been expected, it is notable how closely the Baxalta court aligned its reasoning and findings to that of Amgen court. In particular, similarly to the Amgen court, the Baxalta court equated the disclosed experimental descriptions (i.e., the road map) used to identify antibodies that fall within the scope of the claims as insufficient, finding these descriptions to be nothing more than an invitation to experiment. Additionally, the Baxalta court held fast to the “full scope” enablement test applied by the Amgen court in its review and ultimate decision to invalidate the claims directed to functionally claimed antibodies. Together, this suggests that the Federal Circuit is likely interested in a rigorous application of the “full scope” enablement test, and that descriptions of screening methods, without more, will be insufficient to satisfy this test for functionally claimed antibodies.   

The Federal Circuit in Baxalta closely applied the Supreme Court’s precedent in Amgen. Assuming the Federal Circuit continues to do so, patents directed to functionally claimed antibodies will likely remain highly susceptible to invalidity findings under the “full scope” enablement test.

About The Author:

Jonathan B. (J.B.) Fitzgerald, Ph.D., is counsel at Snell & Wilmer. He is a registered patent attorney and has a Ph.D. in molecular physiology. His primary practice area involves preparing and prosecuting patent applications in the biotechnology and the life sciences.