Enanta Pharmaceuticals, Inc. v. Pfizer Inc. (22-cv-10967).

Enanta asserted that Pfizer’s Plaxovid COVID drug infringed its U.S. 11,358,953 Patent, which claimed compounds that inhibit an enzyme critical in the replication of the COVID-19 virus.  In December, Judge Casper granted Pfizer’s motion for summary judgment of invalidity and denied Enanta’s motion for summary judgment of infringement as moot.

Phizer asserted that it had disclosed nirmatrelvir, the accused active ingredient in Plaxovid, prior to the filing date of the ‘953 application, and that the ‘953 application was not entitled to the priority date of the provisional application as asserted by Enanta.  Pfizer argued both that the ‘953 patent broadened the meaning of “substituted” (a term found in the claims) from the provisional application to the definition in the ‘953 patent specification, and that the disclosure of a broad genus in the provisional did not provide adequate written description of the narrowed genera of compounds claimed in the ‘953 patent.

Noting that to properly claim priority, the prior application must meet both the written description and enablement requirements of 35 U.S.C. § 112 and cannot contain matter not present in the earlier disclosure, Judge Casper determined that the priority claim failed on the first of those grounds, and did not reach the second.  She noted that the term “substituted” was defined in the provisional application as C₂-C₁₂ alkyls whereas the ‘953 Patent defines is as C₁-C₁₂ alkyls, and that the accused product contains a C₁ alkyl.  She rejected Enanta’s argument that the change was simply to correct an obvious typographical error, pointing out that while a court can interpret a patent to correct an obvious error, it cannot correct a mistake – that must be done through post-grant procedures (such as reissue) by the PTO.  She determined that the court, rather than the jury, was the appropriate entity to decide whether an “obvious” typographical error susceptible to court correction existed and found that the error here was not obvious.  Enanta asserted that the error was apparent because the provisional specification’s definition of “substituted” was internally inconsistent, but Judge Casper noted that this inconsistency was not corrected in the ‘953 specification, and that in any event while the error may have been obvious, the correction was not apparent.  Finally, the error was not a minor one in the context of the litigation, as absent the change the claim would not have covered the accused product.  Accordingly, Judge Casper refused to accord the provisional application’s filing date to the ‘953 patent.

Having so found, Judge Casper determined the patent to be invalid over Pfizer’s prior publication of the structural formula of nirmatrelvir at a 2021 American Chemical Society meeting and through a patent application that was filed before Enanta’s ‘953 application (but after Enanta’s provisional filing).  Judge Casper therefore has now entered final judgment to this effect.