Federal Circuit Clarifies the “Reasonable Expectation of Success” Required in Hatch-Waxman Obviousness Challenges

The U.S. Federal Circuit recently clarified the standard that patent challengers must satisfy when attempting to invalidate patented inventions directed to new uses for known drugs. Although designated as a nonprecedential opinion, Genzyme Corporation v. Dr. Reddy’s Laboratories, Nos. 2016-2206, 2016-2207 (Fed. Cir. Dec. 18, 2017) provides important guidance for evaluating whether, for purposes of alleged obviousness, a prior art reference’s isolated, prophetic statement about a possible new use for a drug can support a finding that a person of ordinary skill in the art (“POSITA”) would have had a “reasonable expectation of success” in combining prior art references to achieve the claimed invention. 

Obviousness and the Reasonable Expectation of Success 

A claimed invention is unpatentable if the differences between it and the prior art “are such that the claimed invention as a whole would have been obvious . . . to a person having ordinary skill in the art to which the claimed invention pertains.” 35 U.S.C. § 103. If a patent’s claim limitations can be found individually in separate prior art references, a party seeking to invalidate the patent on obviousness grounds must show by clear and convincing evidence that a POSITA: (1) would have been motivated to combine the teachings of those prior art references to achieve the claimed invention; and (2) would have had a “reasonable expectation of success” in doing so. See Insite Vision Inc. v. Sandoz, Inc., 783 F.3d 853, 859 (Fed. Cir. 2015). 

A Prior Art Reference’s Untested, Prophetic Hypothesis Does Not Provide a Reasonable Expectation of Success

In Genzyme, the patent-at-issue was directed to a method of sequentially administering two known drug products for a new use: mobilizing and harvesting stem cells. Under normal conditions, stem cells attach to bone marrow by forming a bond between a particular receptor on the stem cell (“CXCR-4”) and a protein produced in the bone marrow (“SDF-1”). The plaintiffs discovered, however, that administering the second drug product (plerixafor, a known drug) disrupts the bond between CXCR-4 and SDF-1, and releases stem cells into the bloodstream. The district court held that the defendants had failed to prove that the plaintiffs’ claimed invention was obvious. 

On appeal, the key dispute concerned one of the factual findings required to prove obviousness under § 103: whether a POSITA would have had a “reasonable expectation of success” in combining the asserted prior art references. The primary reference was an article that evaluated the use of plerixafor to disrupt the bond between CXCR-4 and SDF-1 so as to release white blood cells—“and/or stem cells”—into the bloodstream for the purpose of treating HIV. 

The district court had found that this article was not pertinent prior art because it focused on HIV treatment, not mobilizing and harvesting stem cells. The Federal Circuit, however, went one step further. It held that even if the article were pertinent prior art, a POSITA would not have had a reasonable expectation of success in applying the article’s teachings in the new and untested context of mobilizing and harvesting stem cells, notwithstanding the fact that it included the prophetic statement about the possible use of plerixafor for releasing stem cells into the bloodstream. The Federal Circuit characterized that statement as a mere “hypothesi[s] in an isolated sentence, without explanation,” and noted that the rest of the article’s seven pages focused on white blood cells, not stem cells. It found that, despite the mention of stem cells, a POSITA “would have recognized that [the article’s authors] never tested for the presence of stem cells[.]” And it concluded that the article’s hypothesis that plerixafor could be used to release stem cells into the bloodstream was not enough to provide a reasonable expectation of success in actually doing it. 

The Federal Circuit reached similar conclusions with respect to the teachings of the other asserted prior art references, noting again that “a gap exists between using plerixafor to enhance [white blood cell] counts and for stem cell mobilization.” 

Key Takeaway 

Genzyme provides new, important guidance for Hatch-Waxman litigants in evaluating the “reasonable expectation of success” prong of the Federal Circuit’s obviousness analysis. Under Genzyme, a prior art reference’s passing prophetic statement that a known drug could be used to achieve a particular result is likely to be viewed as a mere untested hypothesis that is insufficient, without more, to sustain the required finding that a POSITA would have had a reasonable expectation of success in combining the prior art to achieve that result.