Immunogen Cancer Patent Still Valid After Phigenix's Dispute

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By John T. Aquino

Oct. 29 — Atlanta-based Phigenix Inc. couldn't sink the validity of Immunogen's patent covering Genentech's breast cancer drug Kadcyla, the PTO's patent board ruled in an Oct. 27 decision.

Phigenix had petitioned the Patent Trial and Appeal Board to invalidate the Kadcyla patent in an inter partes review, and the board approved the challenge for trial. The IPR process was created by the America Invents Act to allow third-party challenges of patents at the Patent and Trademark Office.

Phigenix argued that U.S. Patent 8,337,856 would have been obvious to someone working in the field because of prior research studies described in three journal articles.

But the PTAB held that Immunogen offered persuasive evidence that, based on these prior publications combined with others issued before the patent was filed, the “ordinarily skilled artisan” wouldn't have known to perform what is described in the '856 patent.

Kadcyla Big Moneymaker

Genentech, a division of Roche, licenses the '856 patent from Immunogen.

Roche's third-quarter financial report shows Kadcyla with global sales of $574 million in the first nine months of the year, a 57 percent increase over the same period of 2014, with particularly strong growth in Europe after recent launches in France, Italy and Spain. The Food and Drug Administration approved Kadcyla for use in the U.S. in February 2013.

Phigenix sued Immunogen in the U.S. District Court for the Northern District of Georgia in 2014, alleging that Kadcyla infringes Phigenix's U.S. Patent No. 8,080,534. The case was transferred to the U.S. District Court for the Northern District of California in March 2015 and is ongoing, Phigenix, Inc. v. Genentech, Inc., Docket No. 5:15-cv-01238 (N.D. Cal., 3/17/15).

Phigenix Argued Claims ‘Obvious.'

The '856 patent concerns methods of treatment using anti-ErbB receptor antibody-maytansinoid conjugates and articles of manufacture suitable for use in such methods. In particular, the invention concerns ErbB receptor-directed cancer therapies, using anti-ErbB receptor antibody-maytansinoid conjugates. Overexpression of ErbB2 on cell surfaces can lead to cancer in humans, such as certain breast and ovarian cancers.

Phigenix argued that three prior journal articles had rendered the claims at issue of the '856 patent obvious and therefore unpatentable.

Specifically, Phigenix contended that a 1992 article by R.V. Chari and others in the journal Cancer Research anticipated all the “limitations” in the claims at issue that make the claims different from what came before them with one exception: The Chari article doesn't disclose the humanized anti-ErbB2 antibody known as herceptin (huMAb4D5-8).

Phigenix also noted that the herceptin label describes its use for treating patients with metastatic breast cancer and its combination with a pharmaceutically acceptable carrier. The company cited a declaration it had obtained from the co-author of one of the other journal articles it had referenced. He said that based on the Chari article, the herceptin label and the general knowledge of the art at the time, it would have been obvious to the ordinarily skilled artisan when the '856 patent was filed to substitute the mouse monoclonal TA.1 antibody in the immunoconjugate of the Chari article with the humanized mAb huMAB4D5-8 to produce the immunoconjugates recited in the claim.

Not Obvious With Available Knowledge

In an opinion authored by Administrative Patent Judge Jacqueline Wright Bonilla, the board said that Immunogen had provided persuasive evidence that the prior art indicated that Herceptin-maytansinoid immunoconjugates would have been expected to exhibit unacceptable levels of antigen-dependent toxicity in normal human liver tissue in patients.

Immunogen pointed to a 1999 article by Lee H. Pai-Scherf and others in the journal Clinical Cancer Research that describes a phase I clinical study of humans receiving an immunoconjugate (erb-38) comprising a portion of the anti-HER2 monoclonal antibody e23 fused to a truncated form of Pseudomonas exotoxin that observed unacceptable hepatotoxicity in all patients in the treatment group.

Pai-Scherf also said that nothing in herceptin had been found to produce objective responses in breast cancer and when combined with chemotherapy results in an increased response rate.

The board said that Immunogen persuaded it that the ordinarily skilled artisan would have considered the teachings of Pai-Scherf when reading Chari and the other prior art referenced by Phigenix.

“Petitioner does not establish by a preponderance of the evidence that those general statements in Chari 1992, in view of teachings years later in the Herceptin, Pai-Scherf 1999, and other references regarding liver toxicities, would have motivated an ordinary artisan to substitute the mouse TA.1 antibody in the immunoconjugate of Chari 1992 with Herceptin on the basis that one would have expected that modified immunoconjugate to work to treat human tumors.”

Claims Held Not Unpatentable

The PTAB consequently issued an order saying that the claims at issue aren't held to be unpatentable.

Phigenix didn't immediately respond to Bloomberg BNA's e-mail and phone requests for comment. One of Immunogen's attorneys, Eldora Lynn Ellison of Sterne, Kessler, Goldstein & Fox P.L.L.C., Washington, told Bloomberg BNA in an Oct. 28 e-mail, “Our team was very pleased that the PTAB upheld this patent covering Kadcyla, which is an innovative drug that has changed the lives of breast cancer patients.”

The trial was heard before administrative patent judges Bonilla, Francisco C. Prats and Zhenyu Yang.

Phigenix was represented by Andrews Kurth LLP, Washington.

To contact the reporter on this story: John T. Aquino in Washington at

To contact the editor responsible for this story: Lee Barnes at

The decision is at