By Mark Engstrom, J.D.
In a priority contest involving two inventors of a hepatitis C prodrug, the Patent Trial and Appeal Board correctly awarded priority to one inventor after withdrawing the provisional filing date of the other inventor due to a lack of enablement, the U.S. Court of Appeals for the Federal Circuit has ruled. Substantial evidence supported the Board’s finding that a high amount of experimentation was necessary to synthesize the target compound for the prodrug. Because the record showed a sufficient amount of variability and unpredictability to support the Board’s finding that the relevant application did not enable the interference subject matter, the decision of the Board was affirmed (Storer v. Clark, June 21, 2017, Newman, P.).
The PTO instituted an interference between U.S. Patent No. 7,608,600, which was issued to the plaintiffs Richard Storer, et al., and a pending patent application that was filed by the defendant Jeremy Clark. Both sides filed their applications before the effective date of the America Invents Act (AIA), the statute that abolished the "first to invent" interference rule in favor of a "first to file" rule. Under the AIA §3(n)(2), the first-to-invent rule applied to the interference.
The Board proceeding involved methods of treating hepatitis C by administering compounds with a particular chemical and stereochemical structure, based on a five-membered ring with a fluorine substituent in the 2-prime (down) position. The Patent Trial and Appeal Board held that Storer’s provisional application was not enabling, withdrew Clark’s provisional filing date, and awarded priority to Clark. According to the Board, Storer’s application (the "S1" application) failed to sufficiently disclose compounds with the 2-primeF (down) constituent. On appeal, the Federal Circuit had to decide whether the S1 application, together with the prior art, enabled compounds with a 2-primeF (down) substituent.
Storer argued—both before the Board and on appeal—that a person of ordinary skill in the art would have been able to make a class of compounds with the requisite stereochemistry based on information that was provided in the S1 provisional application and the prior art. In Storer’s view, the S1 provisional application performed the substantial step of disclosing the precise chemical structure of the "target compound" (the Boards term for the 2-primeF (down) compounds). Storer did not identify a specific structure with the 2-primeF (down) substituent, but he noted that the prior art contained a "well-known precursor compound" that was merely one step away from the target compound: "Matsuda Compound 17."
Because Matsuda Compound 17 contained a methyl group in the 2-prime (down) position, Storer argued that it was readily converted into the target compound—by known methods—to produce the desired stereochemistry. Matsuda Compound 17 was not mentioned in the S1 provisional, but Storer argued that the precursor to Matsuda Compound 17 was in the S1 provisional, as was that precursor’s conversion to the Matsuda compound.
According to Storer, the precursor was "only two steps away" from the desired 2-prime methyl "up" and 2-prime fluoro "down" configuration," and each scheme disclosed how to modify the 2-prime keto precursor (a compound with a doubly bonded oxygen at the 2-prime position) to obtain Matsuda Compound 17. Storer thus argued that the Matsuda reference, together with the information in the S1 provisional, enabled the synthesis of 2-primeF (down) compounds. According to Storer, three schemes in the S1 provisional described a 2-prime keto precursor, the path to the 2-primeF (down) molecule.
In Storer’s view, a skilled artisan would have recognized that: (1) Matsuda Compound 17 was a "viable precursor" and (2) with knowledge of those structures, the hypothetical artisan would have known to use a common, one-step synthesis to modify the precursor to obtain the target compound.
The Federal Circuit noted that Storer’s provisional specification did not describe the synthesis of the 2-primeF (down) target compounds. The issue thus became the adequacy of the disclosure, in the provisional application, of the general schemes for synthesizing the general classes of modified nucleosides, taken with the knowledge of the art.
The court concluded that substantial evidence supported the Board’s findings that the synthetic schemes in Storer’s provisional application did not teach or suggest conversion of any precursor into the 2-primeF (down) structure, and that the Matsuda synthesis of a corresponding 2-prime methyl (down) and 2-prime hydroxyl (up) structure did not enable a person of ordinary skill to produce the target compounds without undue experimentation. Storer argued that detailed specific examples were unnecessary because the chemistry was predictable, but the court disagreed. The Board’s findings accorded with the record.
Even allowing Storer’s position that a skilled artisan would have started with Matsuda Compound 17, Storer failed to show that the critical stereo-chemical result would predictably ensue. The Board received evidence of side reactions and the skepticism of experts, and it also received evidence that Storer and his team had difficulty and failures in synthesizing the target compound. Finally, the Board received evidence that Clark and his team were "more readily successful" using the same method. Therefore, the Board’s finding that the chemistry was unpredictable accorded with the evidence.
With respect to "undue experimentation," the Board had discussed the amount of experimentation that was needed to produce the claimed compounds. It found that a "high" amount of experimentation was necessary to synthesize a 2-prime fluoro and 2-prime methyl nucleoside with the fluoro moiety in the "down" position, requiring at least two years of a high priority experimentation by persons of skill in the art, including multiple consultations with experts at the top of their fields and additional formal training. In addition, the Board noted Storer’s continuing research after the S1 provisional was filed.
After it considered the entire record, the Board found that a person of ordinary skill—equipped with the disclosure in the provisional application and knowledge of the prior art—would not have been led to make the target compound, and could not do so without undue experimentation. The Federal Circuit agreed. The court concluded that substantial evidence supported the Board’s finding that a high amount of experimentation was necessary to synthesize the target compound. According to the court, the record showed sufficient amount of variability and unpredictability to support the Board’s conclusion that Storer’s provisional application did not enable the interference subject matter. The Board’s decision was therefore affirmed.
The case is No. 2015-1802.
Attorneys: Calvin Griffith (Jones Day) for Richard Storer. Jonathan Elliot Singer (Fish & Richardson, PC) for Jeremy Clark.
MainStory: TopStory Patent FedCirNews
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