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Enablement and Written Description of Unclaimed Variants

Posted by James Juo | Jul 26, 2023 | 0 Comments

In United Therapeutics Corp. v. Liquidia Technologies, Inc., No. 2022-2217, 2023-1021, — F.4th — (Fed. Cir. July 24, 2023), United Therapeutics sued Liquidia for infringing two patents. One covering the treatment of pulmonary hypertension using the drug treprostinil (US Pat. 10716793) and the other patent covering the composition of a purified form of the drug (US Pat. 9593066).

Enablement and Written Description of What is Specified in the Claims

For enablement and written description, the specification must reasonably convey to those skilled in the art that the inventor had possession of the claimed invention as of the filing date. Ariad Pharms., Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1351 (Fed. Cir. 2010) (en banc).

The patent's treatment claims were directed to “treating pulmonary hypertension.” Liquidia argued that the specification provides guidance only for certain types of pulmonary hypertension, and there was no disclosure for how to treat Group 2 Pulmonary Venous Hypertension.

The Federal Circuit disagreed:

Liquidia essentially asks us to treat Group 2 PH as a claimed species within a larger genus (i.e., all five groups of pulmonary hypertension). But analogizing a subset of patients having a variant of a particular disease to traditional genus and species claims is inapt. It would be incorrect to fractionate a disease or condition that a method of treatment claim is directed to, and to require a separate disclosure in the specification for each individual variant of the condition (here, an individual group of pulmonary hypertension patients) in order to satisfy the enablement and written description provisions of 35 U.S.C. § 112, unless these variants are specified in the claims.

Thus, the specification need not address every possible disease subtype or non-responsive patient population to satisfy 35 U.S.C. § 112, as long as those limitations are not captured in the claims.

According to Professor Crouch, it will be interesting though to see how this precedent sits alongside the recent focus on “full scope” disclosure.

Safety and Efficacy of Claim Construction

The method claims were directed to “[a] method of treating pulmonary hypertension comprising administering … a therapeutically effective single event dose …” Should this claim language be construed to require a showing of both safety and efficacy?

As a threshold matter, the Court construed “treating pulmonary hypertension” includes treating all five groups of pulmonary hypertension patients, but does not require a showing of safety and efficacy. In particular, the Court held that “therapeutically effective” had been particularly defined in the specification as improving hemodynamic values and the preamble language of treating PH “does not import any additional efficacy limitations or any safety limitations.”

Questions of safety and efficacy in patent law have long fallen under the purview of the FDA. In re Brana, 51 F.3d 1560, 1567 (Fed. Cir. 1995) (noting that “the requirements under the law for obtaining a patent” are different from “the requirements for obtaining government approval to market a particular drug for human consumption”); Scott v. Finney, 34 F.3d 1058, 1063 (Fed. Cir. 1994) (“Testing for the full safety and effectiveness . . . is more properly left to the [FDA]. Title 35 does not demand that such human testing occur within the confines of Patent and Trademark Office (PTO) proceedings.”); In re Anthony, 414 F.2d 1383, 1395 (CCPA 1969) (“Congress has given the responsibility to the FDA, not to the Patent Office, to determine in the first instance whether drugs are sufficiently safe for use that they can be introduced in the commercial market . . . .”). We decline to insert the FDA's responsibilities into claims by importing requirements where they do not recite such limitations.

Thus, absent incorporation of safety and efficacy requirements in the claims, the safety and efficacy of treating Group 2 PH patients is not part of the claims.

Anticipation of Product-by-Process Claims

Also, some of the composition claims were directed to a product (treprostinil) prepared by a particular process (alkylation and hydrolysis). This is referred to as product-by-process claims. But a product-by-process claim is a product claim, even if claimed by a process by which it can be made. So, for anticipation purposes, such claims “are anticipated by a disclosure of the same product irrespective of the processes by which they are made.”

Here, United Therapeutics did not provide any expert or fact witness rebutting Liquidia's expert's opinions or providing testimony identifying any structural or functional differences between the prior art treprostinil and the claimed Treprostinil.

Thus, the Court affirmed the product-by-process claims were anticipated.

Induced Infringement

“Whoever actively induces infringement of a patent shall be liable as an infringer.” 35 U.S.C. § 271(b).

The Court affirmed that, for inducement of infringement, Liquidia's product merely needs to instruct doctors and patients to administer a therapeutically effective single event dose, which it does.

Liquidia, however, argued that it cannot be held liable for induced infringement because the patent-in-suit (the `793 patent) was found to be unpatentable in an IPR, and an unpatentable or invalid patent cannot be infringed. See Commil USA, LLC v. Cisco Systems, Inc., 575 U.S. 632, 644 (2015) (stating that if “an act that would have been . . . an inducement to infringe pertains to a patent that is shown to be invalid, there is no patent to be infringed”).

          Liquidia's reliance on Commil, 575 U.S. at 632, requires the '793 patent to have been invalidated, but as United Therapeutics argues, the corresponding IPR proceeding of the '793 patent is pending on appeal in this court. A pending, non-final litigation does not negate an intent to infringe that is otherwise supported by evidence. And we have previously held that an IPR decision does not have collateral estoppel effect until that decision is affirmed or the parties waive their appeal rights. XY, LLC v. Trans Ova Genetics, L.C., 890 F.3d 1282, 1294 (Fed. Cir. 2018) (“[A]n affirmance of an invalidity finding, whether from a district court or the Board, has a collateral estoppel effect on all pending or co-pending actions.”). Further, as the court noted, the Board's final written decision does not cancel claims; the claims are cancelled when the Director issues a certificate confirming unpatentability, which occurs only after “the time for appeal has expired or any appeal has terminated.” 35 U.S.C. § 318(b). The '793 IPR decision thus has no impact here on a finding of induced infringement.

Thus, unpatentability is relevant to infringement liability only once a final adjudication of unpatentability or invalidity rules that there is no such patent to infringe.

The patent attorneys at Thomas P. Howard, LLC enforce patents and defend against infringement in litigation nationwide including in Colorado.

About the Author

James Juo

James Juo is an experienced intellectual property attorney. He has successfully litigated various intellectual property disputes involving patents, trademarks, copyrights, and trade secrets. He also has counseled clients on the scope and validity of patent and trademark rights.


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