Pfizer Takes Aim at Herceptin® Patent at the PTAB

By: Jenny Shmuel and Casey Kraning, Ph.D.

Pfizer has shown its muscle in the biosimilars field, purchasing Hospira in 2015 and launching the second biosimilar on the U.S. market, Inflectra® (infliximab), a biosimilar of Johnson & Johnson's Remicade®. Pfizer is now eying Genentech's Herceptin (trastuzumab), which was first FDA approved for metastatic breast cancer in 1998. Pfizer filed two IPRs on June 30th challenging a Herceptin® patent, U.S. Patent No. 8,591,897. The '897 patent is directed to methods of treating patients with non-metastatic HER2-positive breast cancer by administering anthracycline/cyclophosphamide (AC) based chemotherapy, followed by sequential administration of a taxoid and trastuzumab. The earliest priority date on the face of the '897 patent is May 2005.

Both of Pfizer's petitions focus on clinical trial N9831, which started in May of 2000 and was titled "Phase III randomized study of doxorubicin plus cyclophosphamide followed by paclitaxel with or without trastuzumab (Herceptin®) in women with her-2-overexpressing node-positive or high-risk node-negative breast cancer." As discussed below, Pfizer alleges that disclosures regarding this trial anticipate or render obvious all of the '897 patent claims. Yet, according to Pfizer, Genentech "obfuscated" critical facts during prosecution to obtain the '897 patent claims, for example, intentionally pointing the Examiner to portions of prior art "that discussed other, less relevant clinical trials."

Pfizer's first petition (IPR2017-01726) contains grounds very similar to those raised in an earlier petition by Celltrion (IPR2017-0959 filed in February 2017). Pfizer has announced its intention to seek joinder of its first petition and Celltrion's petition. Both Celltrion and Pfizer allege that the purportedly novel aspect of the '897 claims is the sequential (rather than concurrent) administration of taxoid and trastuzumab. They also allege that the patent owner did not alert the Examiner to descriptions of the N9831 clinical trial that disclosed the claimed treatment regime. Specifically, Celltrion and Pfizer argue that the patent owner relied on a description of the N9831 study for written description support, but failed to tell the Examiner that descriptions of that same study were widely publicized in the prior art, specifically Piccart-Gebhart (2001) and Perez (2004). The petitioners acknowledge that final results for the N9831 study were not reported until after the '897 patent priority date, but contend that the final results are not necessary for anticipation. Thus, according to the petitioners, Piccart-Gebhart and Perez, alone or in combination with Thomas (2003) (a review article on adjuvant therapies for breast cancer) anticipate or render obvious all of the claims.

Pfizer's second IPR petition (IPR2017-01727) raises new grounds. Pfizer alleges that claims 1-3 and 5-13 are obvious in light of an archived clinicaltrials.gov webpage from March 2004 containing a "detailed description" of the N9831 study, and claim 4 is obvious in light of that webpage in combination with Tan (2003) (an article about ongoing breast cancer adjuvant trials with trastuzumab that provided further details regarding dosing in the N9831 study). This petition is therefore heavily based on a historical webpage accessed through the Wayback Machine, a digital archive of the World Wide Web, which is sometimes difficult to satisfactorily authenticate and prove was publicly available. In an attempt to meet this challenge, Pfizer attached an affidavit from the Office Manager at the Internet Archive, which created the Wayback Machine, purporting to authenticate the webpage printout.

Genentech has not yet responded to any of these challenges. Because Genentech did not file a preliminary response to Celltrion's petition (which would have been due in May 2017), the board's decision on institution is expected by August 21, 2017. With respect to Pfizer's challenges, the Patent Owner responses are due September 30, 2017.

We will continue to monitor these matters and provide updates.