`Declaration of Robert S. Kerbel, Ph.D.
`
`
`Filed on behalf of Patent Owner Genentech, Inc. by:
`
`David L. Cavanaugh (Reg. No. 36,476)
`Rebecca A. Whitfield (Reg. No. 73,756)
`Robert J. Gunther, Jr. (Pro Hac Vice)
`Lisa J. Pirozzolo (Pro Hac Vice)
`Kevin S. Prussia (Pro Hac Vice)
`Andrew J. Danford (Pro Hac Vice)
`WILMER CUTLER PICKERING
` HALE AND DORR LLP
`1875 Pennsylvania Ave., NW
`Washington, DC 20006
`
`
`Adam R. Brausa (Reg. No.
`60,287)
`Daralyn J. Durie (Pro Hac
`Vice)
`DURIE TANGRI LLP
`217 Leidesdorff Street
`San Francisco, CA 94111
`
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`
`____________________________________________
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`
`____________________________________________
`
`CELLTRION, INC.,
`Petitioner,
`
`v.
`
`GENENTECH, INC.,
`Patent Owner.
`____________________________________________
`
`Case IPR2017-01122
`Patent Nos. 7,892,549
`____________________________________________
`
`EXPERT DECLARATION OF ROBERT S. KERBEL, PH.D.
`
`
`
`Genentech 2061
`Celltrion v. Genentech
`IPR2017-01122
`
`
`
`
`
`
`
`I.
`
`Case No. IPR2017-01122
`Declaration of Robert S. Kerbel, Ph.D.
`
`TABLE OF CONTENTS
`
`Page
`
`INTRODUCTION AND BACKGROUND .................................................. 1
`
`A. Qualifications and Experience ............................................................ 3
`
`B.
`
`C.
`
`Compensation ................................................................................... 11
`
`Prior Expert Testimony ..................................................................... 11
`
`II.
`
`STATE OF THE ART OF PRECLINICAL CANCER RESEARCH AS OF
`1997 ............................................................................................................ 12
`
`A.
`
`In Vitro Testing ................................................................................ 12
`
`B.
`
`In Vivo Testing ................................................................................. 13
`
`1.
`
`2.
`
`Early Mouse Models ............................................................... 13
`
`Development of Human Xenografts ........................................ 15
`
`C.
`
`Xenograft Models in the 1990s ......................................................... 17
`
`III. THE PRECLINICAL DATA RELIED UPON BY PETITIONER AND DR.
`EARHART ................................................................................................. 20
`
`IV. SUMMARY AND BASES FOR OPINION ............................................... 22
`
`A.
`
`B.
`
`C.
`
`It was well known in the mid to late 1990s, and remains true
`today, that preclinical results are not a reliable predictor of
`human clinical results. ...................................................................... 24
`
`It was well-known that a single tumor line, as used in the
`Baselga references, could provide skewed results. ............................ 27
`
`It was well-known that preclinical data does not predict toxicity
`in human patients due to tissue differences. ...................................... 32
`
`i
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`Case No. IPR2017-01122
`Declaration of Robert S. Kerbel, Ph.D.
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`The preclinical studies in the Baselga references were further
`limited by the manner of creating the xenograft models. ................... 35
`
`The end point in the Baselga Abstracts of measuring tumor
`response rate does not provide information on time to disease
`progression. ...................................................................................... 37
`
`D.
`
`E.
`
`
`
`
`
`ii
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`
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`Case No. IPR2017-01122
`Declaration of Robert S. Kerbel, Ph.D.
`
`
`I.
`
`INTRODUCTION AND BACKGROUND
`
`1.
`
`I, Robert S. Kerbel, Ph.D., have been retained by counsel for
`
`Genentech, Inc. (“Patent Owner”) as an expert in Celltrion, Inc. v. Genentech, Inc.,
`
`IPR2017-01122, challenging claims 1-11 and 14-18 of U.S. Patent No. 7,892,549
`
`(the “’549 patent”). I understand that on October 4, 2017, the Patent Trial and
`
`Appeal Board (the “Board”) instituted inter partes review as to these claims of the
`
`’549 patent.
`
`2. As described in more detail below, I understand that the ’549 patent is
`
`directed to treatment of a certain type of breast cancer that overexpresses a human
`
`epidermal growth factor, Erb-B2 receptor tyrosine kinase (also called HER2). I
`
`further understand that the ’549 patent describes a treatment therapy that includes
`
`at least an anti-erbB2 antibody (specifically, rhuMAb HER2 and now known as
`
`Herceptin® or trastuzumab), a taxoid (specifically, paclitaxel), and a third agent in
`
`an amount effective to extend the time to disease progression in a human patient.
`
`3.
`
`I further understand that the Petitioner Celltrion, Inc. (“Petitioner”)
`
`makes certain arguments, and that its expert Dr. Robert Howard Earhart, Jr. asserts
`
`certain opinions, regarding the predictive value of preclinical studies in obtaining
`
`specific results in clinical studies. In particular, those preclinical studies are
`
`described in two one-paragraph abstracts, J. Baselga et al., Anti HER2 Humanized
`
`Monoclonal Antibody (MAb) Alone and in Combination with Chemotherapy
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`1
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`Against Human Breast Carcinoma Xenografts, 13 PROC. AM. SOC. CLINICAL
`
`ONCOLOGY 63 (Abstract 53) (1994) (Ex. 1019), and Baselga et al., Antitumor
`
`Activity of Paclitaxel in Combination with Anti-growth Factor Receptor
`
`Monoclonal Antibodies in Breast Cancer Xenografts, 35 PROC. AM. ASSOC.
`
`CLINICAL CANCER RESEARCH 380 (Abstract 2262) (Ex. 1021) (collectively, the
`
`“Baselga Abstracts”). These preclinical studies are also mentioned in J. Baselga et
`
`al., Phase II Study of Weekly Intravenous Recombinant Humanized Anti-p185HER2
`
`Monoclonal Antibody in Patients with HER2/neu-Overexpressing Metastatic
`
`Breast Cancer, 14(3) J. CLINICAL ONCOLOGY 737 (1996) (“Baselga ʼ96”) (Ex.
`
`1020).
`
`4.
`
`I have been asked to review these opinions and publications and to
`
`offer my own opinion as to whether, in the 1997 time frame, the preclinical data
`
`described in these references reporting on testing a combination of rhuMAb HER2
`
`and paclitaxel in a xenograft mouse model suggests that the same combination in
`
`humans would extend the time to disease progression without an increase in severe
`
`adverse effects. As explained in detail below, the preclinical study described in
`
`these references would not have supported any testing or suggested successful
`
`results in human patients given the known limitations of mouse models at that time
`
`and in light of the design of the experiments at issue in particular.
`
`2
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`
`
`
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`5. A list of materials I have reviewed in preparation of this Declaration is
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`Case No. IPR2017-01122
`Declaration of Robert S. Kerbel, Ph.D.
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`attached as Exhibit B. I have also relied upon my scientific knowledge as of
`
`December 1997, which I have been told is the relevant time period for viewing the
`
`state of the art.
`
`A. Qualifications and Experience
`
`6. My background is summarized below and in my curriculum vitae,
`
`which includes a list of my publications and is attached as Exhibit A.
`
`7.
`
`I am currently a Senior Scientist in the Biological Sciences Platform of
`
`the Sunnybrook Research Institute, which is affiliated with the Sunnybrook Health
`
`Sciences Centre, a University of Toronto-affiliated teaching hospital. I also hold a
`
`cross appointment as a full Professor in the Department of Medical Biophysics at
`
`the University of Toronto.
`
`8.
`
`I earned a Bachelor of Sciences (BSc) degree in general sciences in
`
`1967 at the University of Toronto. I received a Ph.D. in immunology from the
`
`Department of Microbiology and Immunology, Queen’s University in Kingston,
`
`Ontario in 1972. I then undertook a two-year period of postdoctoral training at the
`
`Chester Beatty Research Institute, Institute for Cancer Research in London
`
`England where I continued my studies in basic immunology. It was also here
`
`where I first became interested in tumor biology and tumor immunotherapy, and
`
`hence preclinical experimental therapeutics.
`
`3
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`
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`
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`9. After completing my postdoctoral training in 1975, I took a position as
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`an Assistant Professor in the Department of Pathology, Queen’s University in
`
`Kingston, Ontario, as a member of a dedicated cancer research group, supported
`
`primarily by the National Cancer Institute of Canada. I was also a recipient of a
`
`career award called Research Scholar of the National Cancer Institute of Canada
`
`which covered my salary. I remained there for the next decade, during which time
`
`I became interested in immunotherapy for treatment of cancer, including for
`
`metastatic disease, and in developing improved preclinical mouse cancer models
`
`for this purpose. I was appointed Director of the Cancer Research Group in 1981.
`
`At this time I became a Research Associate of the National Cancer Institute of
`
`Canada, a more senior career award.
`
`10.
`
`In 1985, I moved to Toronto to take up a position as Director of the
`
`Cancer and Cell Biology division in a new research institute at Mt. Sinai Hospital,
`
`a University of Toronto teaching hospital. I continued to serve in this capacity
`
`until 1991 at which time I moved to my present location at the Sunnybrook Health
`
`Sciences Centre, where I was recruited as Director of a cancer research division
`
`that was one of four major research components of a new research institute
`
`currently called the Sunnybrook Research Institute (SRI). I served in this
`
`leadership capacity until 2001. During this period, the Cancer Research Division
`
`was incorporated into a broader program called Biological Sciences. The cancer
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`4
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`research component of this program was affiliated with the Toronto-Sunnybrook
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`Regional Cancer Centre, one of the largest cancer treatment centres in Canada,
`
`which was (and still is) located adjacent to my laboratory, and with which I had a
`
`close affiliation.
`
`11. During my career, my major research interests have included studies in
`
`tumor immunology, metastasis, tumor angiogenesis, antiangiogenic therapy,
`
`chemotherapy, drug resistance, and molecular targeted therapies.
`
`12. Especially relevant to these proceedings, my research has included
`
`preclinical studies involving antibodies to the EGF receptor (C225/cetuximab or
`
`Erbitux®) as well as to HER2, using the anti-erbB2 antibody known as
`
`4D5/trastuzumab (Herceptin®), Ras inhibitors, and proteosome inhibitors. For
`
`example, from the 1990s through the present, my research has included learning
`
`the properties and mechanisms of action of rhuMAb HER2 (see, e.g., Ex. 2077,
`
`Alicia M. Viloria Petit, et al., Neutralizing Antibodies against Epidermal Growth
`
`Factor and ErbB-2/neu Receptor Tyrosine Kinases Down-Regulate Vascular
`
`Endothelial Growth Factor Production by Tumor Cells in Vitro and in Vivo,
`
`151(6) AM. J. OF PATHOLOGY 1523 (1997); Ex. 2078, Jeanne M. du Manoir, et al.,
`
`Strategies for Delaying or Treating In vivo Acquired Resistance to Trastuzumab in
`
`Human Breast Cancer Xenografts, 12(3) CLINICAL CANCER RESEARCH 904
`
`(2006)), as well as exploring therapies involving trastuzumab with chemotherapy.
`
`5
`
`
`
`
`(See, e.g., Ex. 2079, Giulio Francia, et al., Long-Term Progression and
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`Therapeutic Response of Visceral Metastatic Disease Non-Invasively Monitored in
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`Mouse Urine Using β-Human Choriogonadotropin Secreting Tumor Cell Lines,
`
`7(10) MOLECULAR CANCER THERAPY 3452 (2008); Ex. 2080, Giulio Francia, et al.,
`
`Comparative Impact of Trastuzumab and Cyclophosphamide on HER-2–Positive
`
`Human Breast Cancer Xenografts, 15(20) CLINICAL CANCER RESEARCH 6358
`
`(2009).)
`
`13.
`
`I have also worked with a number of different chemotherapy drugs
`
`over the years such as cyclophosphamide, cisplatin, vinblastine, topotecan, as well
`
`as paclitaxel and a nanomedicine formulation of paclitaxel called Nab-paclitaxel.
`
`For example, over the last twenty years, I have conducted research—and published
`
`a number of papers—involving the use of paclitaxel in human tumor xenografts of
`
`breast or ovarian cancer. (See, e.g., Ex. 2081, Eric Guerin, et al., A Model of
`
`Postsurgical Advanced Metastatic Breast Cancer More Accurately Replicates the
`
`Clinical Efficacy of Antiangiogenic Drugs, 73(9) CANCER RESEARCH 2743 (2013);
`
`Ex. 2082, Sylvia S.W. Ng, et al., Influence of Formulation Vehicle on Metronomic
`
`Taxane Chemotherapy: Albumin-Bound versus Cremophor EL-Based Paclitaxel
`
`12(14) CLINICAL CANCER RESEARCH 4331 (2006); Ex. 2083, Giannoula Klement,
`
`et al., Differences in Therapeutic Indexes of Combination Metronomic
`
`6
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`Chemotherapy and an Anti-VEGFR-2 Antibody in Multidrug-resistant Human
`
`Breast Cancer Xenografts, 8 CLINICAL CANCER RESEARCH 221 (2002).)
`
`14.
`
` All of the preclinical work I have done in the area of experimental
`
`therapeutics has involved assessment of response and resistance to most of the
`
`various types of aforementioned drugs, utilizing a variety of mouse models to
`
`assess the therapeutic impact on metastatic disease as well as on established
`
`primary tumors. Many of these models involve “orthotopic” transplantation of
`
`cells from established human tumor cell lines (i.e., transplantation of tumor cells
`
`into the organ from which the cancer under study was derived such as breast
`
`cancer cells injected into the mouse mammary fat pads), to create orthotopic
`
`human tumor xenografts.
`
`15. Some examples of the work I did and published in the early to mid-
`
`1990s on orthotopic transplantation of human tumor cell lines include injection of
`
`human malignant melanoma cells subdermally rather than subcutaneously (see,
`
`e.g., Ex. 2085, Maria Rosa Bani, et al., Multiple Features of Advanced Melanoma
`
`Recapitulated in Tumorigenic Variants of Early Stage (Radial Growth Phase)
`
`Human Melanoma Cell Lines: Evidence for a Dominant Phenotype, 56 CANCER
`
`RESEARCH 3075 (1996); Ex. 2086, Hiroaki Kobayashi, et al., Variant Sublines of
`
`Early-Stage Human Melanomas Selected for Tumorigenicity in Nude Mice Express
`
`a Multicytokine-Resistant Phenotype, 144(4) AM. J. OF PATHOLOGY 776 (1994)),
`
`7
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`
`
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`and human bladder cancer cells into the bladder. (See, e.g., Ex. 2087, Robert S.
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`Kerbel, et al., Importance of Orthotopic Transplantation Procedures in Assessing
`
`the Effects of Transfected Genes on Human Tumor Growth and Metastasis, 10
`
`CANCER AND METASTASIS REVIEWS 201 (1991); Ex. 2088, Theodorescu, D., et al.,
`
`Lack of Influence of c-Ha-ras Expression in the Drug Sensitivity of Human
`
`Bladder Cancer Histocultured in Three-Dimensions, 13 ANTICANCER RESEARCH
`
`941 (1993).)
`
`16. Throughout my career and in the course of this research, I have
`
`worked with medical oncologists in two broad complimentary ways. First, I have
`
`had medical (and surgical) oncologists train in my laboratory as Ph.D. students or
`
`postdoctoral fellows. Second, I have collaborated with many medical oncologists
`
`on clinical trials as well as on preclinical research in some cases to support those
`
`trials. Some examples of the former include clinical trials involving an
`
`investigational concept known as low-dose ‘metronomic’ chemotherapy, which
`
`resulted in co-authored publications (see, e.g., Ex. 2089, Nan Soon Wong, et al.,
`
`Phase I/II trial of Metronomic Chemotherapy with Daily Dalteparin and
`
`Cyclophosphamide, Twice-Weekly Methotrexate and Daily Prednisone as Therapy
`
`for Metastatic Breast Cancer Using Vascular Endothelial Growth Factor and
`
`Soluble Vascular Endothelial Growth Factor Receptor Levels as Markers of
`
`Response, 28 J. CLINICAL ONCOLOGY 723 (2010); Ex. 2090, Rena Buckstein, et al.,
`
`8
`
`
`
`
`Lenalidomide and Metronomic Melphalan for CMML and Higher Risk MDS: A
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`Phase 2 Clinical Study with Biomarkers of Angiogenesis, 38 LEUKEMIA RESEARCH
`
`756 (2014)), and the antiangiogenic drug bevacizumab (Avastin®). (See, e.g., Ex.
`
`2091, Julia L. Glade Bender, et al., Phase I Trial and Pharmacokinetic Study of
`
`Bevacizumab in Pediatric Patients with Refractory Solid Tumors: A Children’s
`
`Oncology Group Study, 26(3) J. CLINICAL ONCOLOGY 399 (2008).)
`
`17. Also, in my capacity as director of the cancer research division at
`
`Sunnybrook from 1991-2001, I had the opportunity to interact with medical,
`
`surgical and radiation oncologists in the Toronto-Sunnybrook Regional Cancer
`
`Centre located at Sunnybrook (and now called the Odette Cancer Centre). One of
`
`my responsibilities was to foster interactions between basic cancer and
`
`translational researchers such as myself and the clinical oncologists. To this end, I
`
`organized occasional evening research-in-progress meetings between the two
`
`groups. One of the collaborators was Dr. Joyce Slingerland, a breast cancer
`
`medical oncologist, whom I recruited into the cancer research division when I was
`
`Director, and who held a cross appointment at the Toronto-Sunnybrook Regional
`
`Cancer Centre.
`
`18. Since 1971, I have authored or co-authored 423 published papers. A
`
`number of these papers were peer reviewed invited reviews requested by the
`
`editors of journals such as Science, Nature, the New England Journal of Medicine,
`
`9
`
`
`
`
`Cancer Cell, and a number of review journals such as Nature Reviews Clinical
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`Case No. IPR2017-01122
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`Oncology, Nature Reviews Cancer, and Nature Reviews Drug Discovery. Many of
`
`these reviews or editorial commentaries dealt with experimental therapeutics,
`
`including commentaries on preclinical mouse tumor models for assessing cancer
`
`drugs. I also have been invited, over my career, to give almost 900 lectures around
`
`the world at scientific meetings, universities, research institutes, clinical cancer
`
`treatment centres, courses, and advisory boards of companies during my career.
`
`Many of these were Keynote or Plenary lectures, as noted in my c.v.
`
`19.
`
`I have been active in advisory activities, both in industry and
`
`academia. My numerous industry associated advisory roles as a member of
`
`scientific advisory boards (SABs) or as a consultant have dealt mainly with
`
`experimental therapeutics, and preclinical models to assess cancer drug activity in
`
`mice.
`
`20. Over the course of my career I have received competitive grant support
`
`from numerous agencies including the National Institute of Health, USA which I
`
`held as a foreign investigator for 27 continuous years, the Canadian Institute for
`
`Health Research (over 40 years, continuously), the Canadian Cancer Society
`
`Research Institute (35 years continuously), the Canadian Breast Cancer Foundation
`
`(6 years of support), the Ontario Institute for Cancer Research, and Worldwide
`
`Cancer Research.
`
`10
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`Case No. IPR2017-01122
`Declaration of Robert S. Kerbel, Ph.D.
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`
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`21. Awards I have received include The Robert L. Noble Prize for
`
`Excellence in Cancer Research by the Canadian Cancer Society and National
`
`Cancer Institute of Canada in 2004, the Breast Cancer Research Award from the
`
`European Institute of Oncology in 2008, a Man of Distinction award from the
`
`Israel Cancer Research Fund in 2011, and the Colin Thomson Memorial Medal for
`
`achievements in cancer research from Worldwide Cancer Research (formerly
`
`known as the Association for International Cancer Research) in 2013. Throughout
`
`my career I have also received a succession of career awards (two of which I have
`
`already noted) including a Terry Fox Career Scientist award from the National
`
`Cancer Institute of Canada (1986-1997), a Canada Research Chair in Tumor
`
`Biology, Angiogenesis, and Antiangiogenic Therapy from the Canadian
`
`government (2001-2015), and an endowed professorship, the John & Elizabeth
`
`Tory Family Chair in Experimental Oncology (1993-2001).
`
`B. Compensation
`
`22.
`
`I am being compensated at my normal consulting rate for my work,
`
`which is $600 per hour. My compensation is not dependent on and in no way
`
`affects the substance of my statements in this Declaration.
`
`C.
`
`23.
`
`Prior Expert Testimony
`
`I have not provided expert testimony within the last four years.
`
`Concurrently with this declaration, I am submitting declarations in Hospira, Inc. v.
`
`11
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`Case No. IPR2017-01122
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`Genentech, Inc., IPR2017-00731, Hospira, Inc. v. Genentech, Inc., IPR2017-
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`00737, and Celltrion, Inc. v. Genentech, Inc., IPR2017-01121.
`
`II.
`
`STATE OF THE ART OF PRECLINICAL CANCER RESEARCH AS
`OF 1997
`
`24. Preclinical cancer research provides the foundation for subsequent
`
`clinical trials by identifying drugs of interest that appear to act on human cancer
`
`cells. Generally, preclinical research provides information on (a) whether and how
`
`a particular drug acts on tumor cells to slow their growth and/or shrink the tumors,
`
`(2) the mechanism of action of the drug (i.e., how the drug interacts with cancer
`
`cells or other cells in the tumor microenvironment such as blood vessel or immune
`
`cells to slow growth and/or kill cells), and (3) whether and how the drug affects
`
`non-cancerous cells, especially with respect to causing host toxicities. Based on
`
`the results of preclinical research, academic clinicians, basic scientists, and
`
`clinicians working for drug companies decide whether to propose testing the drug
`
`in humans. This testing of a drug in humans is called clinical trials.
`
`25. There are two main or basic types of preclinical research models: in
`
`vitro (cell cultures), and in vivo (animal subjects). Typically, both in vitro and in
`
`vivo studies are performed before progressing to human clinical trials.
`
`A.
`
`26.
`
`In Vitro Testing
`
` In in vitro testing, established “cell lines” are often used, meaning that
`
`all of the cells derive from a single cancer. These established (also called
`
`12
`
`
`
`
`“permanent” or “continuous”) cell lines can be from a human patient and
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`Case No. IPR2017-01122
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`sometimes are also genetically modified in the laboratory. Even when the cell
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`lines are derived from a patient, the cells can differ substantially from cancer cells
`
`in humans as a result of the cell lines adapting to being cultured on plastic and
`
`being maintained for long periods in vitro. And although the individual cells in a
`
`cell line may have some variations due to genetic mutations or epigenetic changes,
`
`these variations differ in degree and content compared to cancer cells in human
`
`patients.
`
`27. Despite the differences between established cell lines and cancer cells
`
`in patients, in vitro testing was in 1997 and is still today useful because researchers
`
`can test, with relative efficiency, multiple different cell lines representing different
`
`types of cancers (e.g., colon cancer, lung cancer, etc.), as well as different lines of
`
`the same general type of cancer (e.g., different cell lines of HER2-positive breast
`
`cancer). In cancer research, common end points for testing potential cancer drugs
`
`include relative inhibition or proliferation of the cancer cells (i.e., how much does
`
`the drug prevent the cancer cells from spreading?), and cell death (i.e., does the
`
`drug kill the cancer cells?).
`
`B.
`
`In Vivo Testing
`
`1.
`
`Early Mouse Models
`
`13
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`
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`28.
`
` In contrast to in vitro testing, in vivo testing involves using animal
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`models, by far the most common of which is the tumor-bearing mouse.
`
`29. Up until about 1980, these models mostly involved the transplantation
`
`of mouse tumor cells or fragments of mouse tumor tissue into strains of
`
`immunocompetent mice that are genetically compatible with the donor tumor cell
`
`population or tissue.
`
`30. The tumor cells injected were almost always obtained from established
`
`cell lines grown in tissue culture (i.e., in vitro), and were most often injected
`
`subcutaneously in the hind leg or flank of the mouse. This is called ectopic
`
`transplantation for most types of tumors, i.e., those that do not normally arise in the
`
`skin – which is virtually all types of cancer. By injecting tumor cells into the
`
`flank, the resultant “primary” tumors would grow quickly and could be
`
`subsequently measured by using vernier calipers.
`
`31. Sometimes the cells were injected intravenously to generate
`
`experimental metastases, mainly in the lungs. Measuring the cancer metastases,
`
`however, required sacrificing the mouse to visually inspect the lungs.
`
`32.
`
` Sometimes the tumor cells were injected “orthotopically”, i.e., into the
`
`organ from which the cancer cell population was derived, e.g., breast cancer cells
`
`are injected into mammary fat pads of female mice, to generate “primary” tumors.
`
`14
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`
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`33. The impact of a cancer therapy on tumor growth in the primary tumor
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`models was assessed by measuring changes in tumor volume/size, and sometimes
`
`changes in survival times via comparison to various control groups.
`
`2.
`
`Development of Human Xenografts
`
`34. Starting in earnest in the 1970s, researchers started to develop and
`
`utilize human tumor xenografts as animal models to test cancer drugs. This was
`
`mainly made possible by the discovery of the “nude” athymic mouse which cannot
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`develop thymus-derived T lymphocytes – the main cell type responsible for
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`rejecting foreign tissue such as a human skin graft, or in this case injected human
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`tumor cell or tissue graft. Prior to that it was possible to create T cell deficient
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`mice using a combination of thymectomy plus radiation or chemotherapy, but they
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`were not used widely for human tumor xenograft studies.
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`35.
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`In a xenograft, dispersed human cancer cells or intact human tumor
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`tissue fragments are transplanted into immunocompromised mice (such as athymic
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`nude mice). The rationale behind using such xenografts is that they more closely
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`resemble the cancer in a human cancer patient than tumor cells from established
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`cell cultures or mouse tumors, and therefore the reactions and results caused by
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`drugs or therapies using such human tumor xenografts approximate somewhat
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`better what may occur in humans.
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`36.
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`Just as with the early mouse tumor models, with a human tumor
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`Case No. IPR2017-01122
`Declaration of Robert S. Kerbel, Ph.D.
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`xenograft model the cancer cells injected into the mouse will form tumors, which
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`researchers can measure and monitor when treating the mice with a drug. The
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`most common endpoint for testing drugs in these xenograft models is tumor
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`response (also called response rate), which measures whether the tumors continue
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`to progress normally or respond in some other way to treatment, whether by being
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`delayed in growth, shrinking in size, or becoming fully eradicated. In the 1990s,
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`and beforehand, xenograft model results rarely used or reported progression free
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`survival (PFS) or time to progression (TTP) as endpoints.
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`37. When xenograft models were first developed and through the mid-
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`1980s, there was excitement about the possibility that they could be used to help
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`select a particular drug therapy for an individual patient by using a sample of the
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`cancer taken directly from the human patient to create an ‘individualized’
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`xenograft. This individualized xenograft model, it was theorized, could be highly
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`accurate in predicting cancer drug activity in individual respective patients, and
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`thus it was hypothesized that this model could be used as a “predictive biomarker”
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`for selecting drug therapies tailored to the patient who donated the tumor sample.
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`Indeed, a number of studies reported strong correlations between the tumor
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`response in mice as compared to the human patient from which the tumor
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`specimen was obtained. (Ex. 1026, H.H. Fiebig, et al., Comparison of Tumor
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`Response in Nude Mice and in the Patients, 74 BEHRING INST. MITT. 343, 343,
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`349-350 (1984) (hereafter “Fiebig 1984”); Ex. 2092, Beppino C. Giovanella, et al.,
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`Correlation Between Response to Chemotherapy of Human Tumors in Patients and
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`in Nude Mice, 52 CANCER 1146, 1146 (1983).)
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`38. Yet it turned out that these “patient derived” tissue xenografts were not
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`predictive of treatment for other human patients having the same type of cancer.
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`Further, these patient-derived xenografts had many serious technical problems,
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`including the low percentages of tumor specimens for most tumor types that “took”
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`and grew progressively in the immune deficient mice, and the generally long
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`latency periods for some tumors to grow and become visible (e.g., 4-6 months)
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`before treatment could be started and the impact assessed. (Ex. 1026, Fiebig 1984,
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`346-347.) As a result of these problems, the human patients from which samples
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`were taken had often died before any of the results of the tests on the xenograft
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`models could be applied to the patients.
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`C. Xenograft Models in the 1990s
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`39. As a result of the problems with a patient-derived xenograft strategy,
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`researchers focused on the more practical method of using established tumor cell
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`lines from tissue culture for human tumor xenografts. These tumor cell lines often
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`had a take rate of 100% (meaning that tumors grew 100% of the time), and tumors
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`usually appeared within weeks of tumor cell transplantation. The reason for the
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`success in establishing tumors using cell lines instead of samples from human
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`Case No. IPR2017-01122
`Declaration of Robert S. Kerbel, Ph.D.
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`patients is that the cell lines contain a comparatively high fraction of dividing cells
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`by virtue of being held in culture – those cells that do not divide as quickly are out-
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`paced by those that do, and this out-pacing is compounded over time in cell
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`culture.
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`40. That these cell cultures include more rapidly dividing cells also means,
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`however, that they do not accurately reflect cancer as found in human patients.
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`Further, the rapid growth rate of cell cultures (and the resulting xenografts made
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`from them) means that they have greater sensitivity to virtually all chemotherapy
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`drugs, which are designed to preferentially target rapidly dividing cells. As a
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`preclinical model, however, the xenograft nonetheless provides information on
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`whether and how a cancer line will react to a particular drug, even if it is not
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`predictive of the particular reaction in a population of human patients with
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`heterogenous tumors of the same or different types.
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`41. As with the early mouse models, a xenograft can be formed either
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`through ectopic or orthotopic transplantation. For example, in the 1990s,
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`orthotopic xenograft models for breast cancer could be created by injecting breast
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`cancer cells into the mammary fat pad. (Ex. 2093, L. Bao, et al., Effects of
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`Inoculation Site and Matrigel on Growth and Metastasis of Human Breast Cancer
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`Cells, 70 BRITISH J. OF CANCER 228, 229 (1994).) Again, the rationale was that
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`such a model would more closely approximate how the cancer and therapy may act
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`Case No. IPR2017-01122
`Declaration of Robert S. Kerbel, Ph.D.
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`in humans.
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`42. Similar to the established cell lines for in vitro cancer research, there
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`were multiple cell lines available for human tumor xenograft models, allowing
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`researchers to test different types of cancers, as well as different lines of the same
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`type of cancer. For example, HER2-positive breast cancer refers to breast cancer
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`in which the cells have many more than the usual two copies of the gene encoding
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`for the epidermal growth factor receptor called ErbB2 (HER2), resulting in
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`elevated expression of the HER2 epidermal growth factor protein. In the 1990s,
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`there were several different cell lines of HER2-positive breast cancer, each with
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`different numbers of the ErbB2 gene in the cells. For example, one study in 1995
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`(Ex. 2064, János Szöllösi, et al., ERBB-2 (HER2/neu) Gene Copy Number,
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`p185HER-2 Overexpression, and Intratumor Heterogeneity in Human Breast Cancer,
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`55 CANCER RESEARCH 5400, 5402 (1995) (hereafter “Szöllösi 1995”)) estimated
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`that a specific cell line identified as BT-474 ha