October 22, 2019

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When the PTO Shows Sound Basis for Believing Two Products Are the Same, It Is the Applicant’s Burden to Show They Are Not

In affirming a decision of the U.S. Patent and Trademark Office (PTO) Board of Patent Appeals and Interferences’ (Board) finding of inherent anticipation, the U.S. Court of Appeals for the Federal Circuit held that once the examiner establishes that the prior art teaches “the same or substantially the same compound,” the burden of proof shifts to applicants to prove that either the claimed structures are different or that the claimed properties are not inherent in the prior art. In re Mousa, Case No. 11-1294 (Fed. Cir., Apr. 19, 2012) (Reyna, J.).

The application discloses a super-sulfated, oxidized heparin fraction. Heparin can prevent angiogenesis by inhibiting the activities of fibroblast growth factor 2 (FGF2). However, its use is limited because heparin is also an anticoagulant and can cause bleeding complications. The application discloses that oxidized heparin fractions fully inhibit FGF2-induced angiogenesis. Additionally, the bleeding complications normally associated with heparin can be eliminated by using these super-sulfated, oxidized heparin fractions because they possess weaker anticoagulant properties.

During prosecution, the examiner rejected several claims of the application as being inherently anticipated by the Naggi patent. The Naggi patent discloses treating heparin with a mixture of sulfuric acid and chlorosulfonic acid (both of which are strong oxidizing agents) to produce a super-sulfated heparin fraction that has weak anticoagulant properties. Subsequently, Mousa amended the claims to recite that the heparin fraction “fully inhibits fibroblast growth factor (FGF2) induced angiogenesis.” Mousa argued that the amended claims did not encompass all super-sulfated, oxidized fractions, but only those fractions with the FGF2-related property, a functional characteristic that the Naggi patent failed to disclose. Nonetheless, the inherent anticipation rejection was maintained by the examiner and affirmed by the Board. Mousa appealed.

The Federal Circuit agreed with the Board. The Federal Circuit concluded that there was a sound basis for the examiner to believe that treating heparin with the strong oxidizing agents necessarily results in oxidized heparin, and that the burden of proof was properly shifted to Mousa to show that those oxidizing agents did not oxidize heparin, as well as that the Naggi heparin fractions did not possess the same FGF2-inhibiting characteristics as claimed by Mousa. Mousa failed to satisfy this burden. While Mousa argued that oxidizing agents do not oxidize every substance and that the examiner did not establish that these chemicals can oxidize heparin, Mousa provided no proof to support of this argument. Further, the Court also dismissed Mousa’s argument that a finding of inherency requires “virtual identity” of the two products. Instead, the correct standard is that once the claimed and prior art products are found to be “substantially identical,” an applicant needs to prove that the prior art product does not necessarily or inherently possess the recited characteristics.

Practice Note: Once the PTO meets the “substantially identity” standard, the applicant has the burden of providing actual evidence of structural or functional dissimilarity. Attorney argument alone is not sufficient. Interestingly, in a child application (now US Patent 8,071,569), Mousa was able to distinguish Naggi by adding a claim limitation that “the percentage of hydroxyl residues of the heparin fraction [that] are oxidized is in a range of 25 percent to 100 percent,” because Naggi teaches away from increasing the percentage of oxidized hydroxyl residues beyond the level that is detectable by nuclear magnetic resonance (NMR). 

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