Phase 11 Study of Weekly Intravenous Recombinant
`Humanized Anti-p185HER2 Monoclonal Antibody in
`Patients With HER2/neu-Overexpressing
`Metastatic Breast Cancer
`
`By José Baselga, Debasish Tripathy, John Mendelsohn, Sharon Baughmon, Christopher C. Benz, Lucy Dantis,
`Nancy T. Sklarin, Andrew D. Seidman, Clifford A. Huclis, Jackie Moore, Paul P. Rosen, Thomas Twaddell,
`l. Craig Henderson, and Larry Norton
`
`Purpose: Breast cancer frequently overexpresses the
`product of the HER2 proto-oncogene, a 185-kd growth
`factor receptor (plBSHE'u). The recombinant humanized
`monoclonal antibody (rhuMAb) HER2 has high affinity
`for p185HER2 and inhibits the growth of breast cancer
`cells that overexpress HER2. We evaluated the efficacy
`and toxicity of weekly intravenous administration of rhu-
`MAb HER2 in patients with HER2-overexpressing meta-
`static breast cancer.
`Patients and Methods: We treated 46 patients with
`metastatic breast carcinomas that overexpressed HER2.
`Patients received a loading dose of 250 mg of intrave-
`nous rhuMAb HER2, then 10 weekly doses of 100 mg
`each. Patients with no disease progression at the comple-
`tion of this treatment period were offered a maintenance
`phase of 100 mg/wk.
`
`Results: Study patients had extensive metastatic dis-
`ease, and most had received extensive prior anticancer
`therapy. Adequate pharmacokinetic levels of rhuMAb
`
`URING THE LAST DECADE, proto-oncogenes that
`encode growth factors and growth factor receptors
`have been found to play important roles in the pathogenesis
`of several human malignancies, including breast cancer.1 The
`HER2 gene (also known as neu and as c—erbB—2) encodes a
`185-kd transmembrane glycoprotein receptor (p185HER2) that
`has partial homology with the epidermal growth factor recep-
`tor, and that shares with that receptor intrinsic tyrosine kinase
`activity.“ HER2 is overexpressed in 25% to 30% of human
`breast cancerss’6 and predicts for a worse prognosis in patients
`with primary disease that involves axillary lymph nodes.5‘7‘8
`Several lines of evidence support a direct role for HER2
`in the pathogenesis and clinical aggressiveness of HER2-
`overexpressing tumors: The introduction of HER2 into non-
`neoplastic cells causes their malignant
`transformation.“10
`Transgenic mice that express HER2 develop mammary tu-
`mors.” HER2 overexpression is common in ductal carcino-
`mas in situ and in their associated invasive canoers.”’l3 Anti-
`
`bodies directed at p185HER2 can inhibit the growth of tumors
`and of lIansformed cells that express high levels of this recep-
`tonlti-ls
`
`The latter observation suggests that p185HER2 may be
`a potential target for the treatment of breast cancer or
`preinvasive breast lesions because these cells commonly
`overexpress HER2. The murine monoclonal antibody
`(MAb) 4D5, directed against the extracellular domain of
`
`HER2 were obtained in 90% of the patients. Toxicity was
`minimal and no antibodies against rhuMAb HER2 were
`detected in any patients. Obiective responses were seen
`in five of 43 assessable patients, and included one com-
`plete remission and four partial remissions (overall re-
`sponse rate, 11.6%; 95% confidence interval, 4.36 to
`25.9). Responses were observed in liver, mediastinum,
`lymph nodes, and chest wall lesions. Minor responses,
`seen in two patients, and stable disease, which occurred
`in 14 patients, lasted for a median of 5.1 months.
`Conclusion:
`rhuMAb HER2 is well tolerated and clini-
`
`cally active in patients with HER2-overexpressing meta-
`static breast cancers that had received extensive prior
`therapy. This is evidence that targeting growth factor
`receptors can cause regression of human cancer and ius-
`tifies further evaluation of this agent.
`J Clin Oncol 14:737-744. © I 996 by American So-
`ciety of Clinical Oncology.
`
`p185HER2 (ECDHERZ), is a potent inhibitor of growth, in
`vitro and in xenograft models, of human breast cancer
`cells that overexpress HER2.”21 However, murine anti-
`bodies are limited clinically because they are immuno—
`genic. To facilitate
`further
`clinical
`investigations,
`therefore, MAb 4D5 was humanized. The resulting re—
`combinant humanized anti-p185HERZ monoclonal antibody
`(rhuMAb HER2) was found to be safe and to have dose-
`dependent pharrnacokinetics in two prior phase I clinical
`trials.
`
`
`
`From the Department ofMedicine, Services ofBreast and Gyneco-
`logical Cancer Medicine and Clinical Immunology, Department of
`Pathology, Memorial Sloan-Kettering Cancer Center, New York,
`NY; Division of Oncology, University of California, San Francisco;
`and Pharmacokinetics and Metabolism and Clinical Research, Genv
`entech, Inc, South San Francisco, CA.
`Submitted August 8, 1995; accepted October 10, 1995.
`Supported in part by an American Society of Clinical Oncology
`Career Development Award (to J.B. and A.D.S.), a SPORE grant
`(p50-CA58207) from The National Cancer Institute, Bethesda, MD,
`and Genentech Inc, South San Francisco, CA.
`Address reprint requests to Jose’ Baselga, MD, Breast and Gyne—
`cological Cancer Medicine Service, Memorial Sloan-Kettering Can-
`cer Center, 1275 York Ave, New York, NY [0021-6007.
`© 1996 by American Society of Clinical Oncology.
`0732- 183X/96/1403-0008$3. 00/0
`
`Journal of Clinical Oncology, Vol 14, No 3 (March), 1996: pp 737-744
`
`737
`
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`Copyright © 2017 American Society of Clinical Oncology. All rights reserved.
`
`InnoPharma Exhibit 1083.0001
`
`

`

`738
`
`BASELGA ET AL
`
`We now report the results of a phase II study of multi-
`ple-dose intravenous administration of rhuMAb HER2 in
`patients with metastatic breast cancer. The objectives of
`this trial were to determine the antitumor activity of rhu-
`MAb HER2 in this patient population, as well as to define
`further the toxicity profile and pharmacokinetics of rhu—
`MAb HER2.
`
`had documented dose-dependent pharmacokinetics. In this current
`trial, rhuMAb HER2 was administered intravenously over a period
`of 90 minutes in the outpatient setting. Each patient received a
`loading dose of 250 mg of rhuMAb HER2 on day 0, and beginning
`on day 7,100 mg weekly for a total of 10 doses. At the completion
`of this treatment period, patients with stable disease or minor, partial,
`or complete responses were entered onto a maintenance phase of
`weekly rhuMAb HER2 administration until disease progression.
`
`PATIENTS AND METHODS
`
`Preparation and Humanization 0f rhuMAb HER2
`Antibody
`MAb 4D5 was initially derived by immunizing mice with cells
`that expressed high levels of the HER2 gene product, pISSHE‘“.19
`MAb 4D5, directed at
`the extracellular domain of p185HERZ
`(ECDHERZ), inhibits the in vitro growth of breast cancer cells that
`contain high levels of plSSHERZ.‘9'2° rhuMAb HER2 was engineered
`by inserting the complementarity determining regions of MAb 4D5
`into the framework of a consensus human immunoglobulin G.
`(IgG1 ).22 The resulting rhuMAb HER2 has high affinity for p185“lam
`(Dillohiation constant [Kd] = 0.1 nmol/L), markedly inhibits, in vitro
`and in human xenografts,
`the growth of breast cancer cells that
`contain high levels of pISSHERZ, and induces antibody-dependent
`cellular cytotoxicity (ADCC).22'23 rhuMAb HER2 is produced by a
`genetically engineered Chinese hamster ovary (CHO) cell
`line,
`grown in large scale, that secretes rhuMAb HER2 into the culture
`medium. Antibody is purified from the CHO culture media using
`standard chromatographic and filtration methods. Each lot of anti-
`body used in this study was assayed to verify identity, purity, and
`potency, as well as to meet Food and Drug Administration require-
`ments for sterility and safety.
`
`Selection of Patients
`Patients eligible for this study were adult women whose metastatic
`breast carcinomas overexpressed HER2 (see later). All patients had
`measurable disease, a Kamofsky’s performance status of at least
`60%, and preserved hematologic, liver, renal, and pulmonary func—
`tion. Patients with lymphangitic pulmonary metastasis, history of
`brain metastasis, or bone metastases as the only site of measurable
`disease were excluded. Chemotherapy or additive hormonal therapy
`within 3 weeks before study entry (6 weeks for mitomycin or ni-
`trosureas) was not permitted. Informed consent was obtained and
`documented in writing before study entry.
`Tumor expression of HER2 was determined by immunohisto—
`chemical analysis, as previously described}6 of a set of thin sections
`prepared from the patient’s paraffin—archived tumor blocks. The pri—
`mary detecting antibody used was murine MAb 4D5, which has
`the same complementarity determining regions as rhuMAb HER2.
`Tumors were considered to overexpress HER2 if at least 25% of
`tumor cells exhibited characteristic membrane staining for p185HER2
`
`Antibody Administration
`The pharmacokinetic goal was to achieve rhuMAb HER2 trough
`serum concentrations greater than 10 ag/mL, a level associated with
`optimal inhibition of cell growth in the preclinical model.22 The
`optimal dose and schedule of rhuMAb HER2 was based on two
`prior phase I clinical trials, conducted at University of California,
`Los Angeles, and Memorial Sloan-Kettering Cancer Center, which
`
`Evaluation of Toxicity
`Toxicity was scored based on a modified National Cancer Institute
`common toxicity criteria. Complete blood cell counts, urinalysis,
`coagulation profile, and hepatic enzyme, renal, and electrolyte stud-
`ies were performed weekly while on the study.
`
`Pharmacokinetics, Determination of Extracellular
`Domain of p] 85”“ Levels, and Antibodies Directed
`Against rhuMAb HER2
`Blood samples for pharrnacokinetic analysis were collected just
`before each treatment with rhuMAb HER2 and within the first hour
`following the end of each rhuMAb HER2 infusion. Serum concentra-
`tions of rhuMAb HER2 were determined in a receptor binding assay
`that detects binding with ECDHERZ. The nominal limit of detection
`for rhuMAb HER2 in serum samples was 156 ng/mL. The presence
`of antibodies to rhuMAb HER2 was determined with a bridging-
`type titer enzyme-linked imrnunosorbent assay (ELISA). Circulating
`concentrations of ECDHER2 shed by patients’ tumors were also deter-
`mined using an ELISA.24 The pair of antibodies used for the assay
`were 7C2 as coat and 2C4 as horseradish peroxidase~conjugated
`antibody; the lower limit of detection for this assay ranged from 2.8
`to 8.3 ng/mL (Baly D, Wong WL, unpublished data, November
`1994).
`Serum levels of rhuMAb HER2 as a function of time were ana—
`lyzed for each patient using a one-compartment model. Model pa-
`rameters (volume and the elimination rate constant [K]) were esti—
`mated for each patient using a maximum-likelihood estimation
`procedure.25 rhuMAb HER2 half-life (tm) was calculated by dividing
`ln2by Kc.
`
`Tumor Response
`Tumor response was determined at the completion of the initial
`11—week treatment period. All responses were confirmed by an inde-
`pendent extramural evaluation committee composed of an oncologist
`and a radiologist. Complete response was defined as the disappear-
`ance of all radiographically and/or visually apparent tumor, partial
`response as a 2 50% reduction in the sum of the products of the
`perpendicular diameters of all measurable lesions, minimal response
`as a 2 25% and less than 50% reduction in the diameters, stable
`disease as no change greater than 25% in the size of measurable
`lesions, and progressive disease as a 2 25% increase in any measur-
`able lesion or the appearance of any new lesion. Although bone
`metastases were considered not measurable for response, patients
`had to have at least stability of bone lesions to be considered re—
`sponders. Patients who had entered the maintenance phase of the
`study had tumor responses evaluated every 11 weeks, or earlier if
`clinically indicated. Time to tumor progression was calculated from
`the beginning of therapy to progression. Confidence limits for re-
`sponse rates were calculated using the exact method for a single
`proportion.26
`
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`Copyright © 2017 American Society of Clinical Oncology. All rights reserved.
`
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`
`

`

`ANTI-HER2 ANTIBODY THERAPY FOR BREAST CANCER
`
`739
`
`Table 1. Patient Characteristics
`
`Characteristic
`
`Age, years
`Median
`Range
`Karnoisky performance status
`Median
`Range
`Level of HER2 expression‘
`25%-50% cells
`> 50% cells
`Receptor status
`Estrogen receptor—positive (n = 40)
`Progesterone receptorspositive (n = 39)
`No. of metastatic sites
`1
`2
`2 3
`Dominant site of metastasis
`Viscera
`Skeleton
`Sol't tissues
`Prior therapy
`Chemotherapy
`Adiuvant chemotherapy
`Neoadiuvant chemotherapy
`Metastatic disease (no. of regimens)
`None
`1
`2
`> 2
`Median
`Range
`Hormonal therapy
`Adiuvant tamoxifen
`Metastatic disease
`
`Patients (N = 46)
`No.
`‘36
`
`50
`30-65
`
`90
`60-100
`
`7
`39
`
`17
`15
`
`16
`14
`16
`
`37
`1
`8
`
`45
`26
`4
`
`8
`9
`9
`20
`
`7
`21
`
`15.2
`84.8
`
`42.5
`38.5
`
`34.5
`30.4
`34.5
`
`80.4
`2.2
`17.4
`
`97.8
`56.5
`8.7
`
`17.4
`1 9.6
`1 9.6
`43.5
`
`15.2
`45.6
`
`2
`0-7
`
`‘In percent of tumor cells with cytoplasmic membrane staining.
`
`RESULTS
`
`Patients characteristics are listed in Table 1. A total of
`
`46 patients were enrolled onto the study. Their level of
`tumor overexpression of HER2 was relatively high, with
`more than 80% of the tumors having more than half of
`their cells exhibit positive membrane staining. Our patient
`population had extensive metastatic disease: 34.5% of
`patients had three or more metastatic sites. Dominant sites
`of metastases were visceral in 80% of cases (lung in 18,
`liver in 13, both liver and lung in five, and ovary in one).
`Only 17.4% of cases had dominant metastases in soft
`tissues (skin and lymph nodes) and only one patient had
`bone as the dominant site of disease. The total number
`
`of patients with bone disease was 18 (39%). All but one
`of the patients had received prior chemotherapy, with
`82.6% having received at least one regimen for metastatic
`
`disease and 63% having received two or more regimens.
`Of this latter group, four patients had previously received
`high-dose chemotherapy with hematopoietic stem-cell
`support.
`Data on rhuMAb HER2 pharmacokinetics are available
`from 45 patients (Table 2). More than 90% of the exam-
`ined population (41 patients) had rhuMAb HER2 trough
`levels above the targeted IO—yg/mL level. The mean se-
`rum tm of rhuMAb HER2 was 8.3 i 5.0 days. The rhu—
`MAb HER2 serum tm was found to be dependent on the
`presence of circulating ECDHERZ released from the tumor
`into the serum (Table 2). Representative examples of
`pharmacokinetics profiles are shown in Fig 1. Figure 1A
`shows the serum levels of rhuMAb HER2 in a patient
`with undetectable level of circulating ECDHERZ; stable,
`therapeutic serum levels of the drug were maintained in
`this patient for more than 1 year. Figure 1B shows the
`serum levels of rhuMAb HER2 in a patient with high
`levels of circulating ECDHEM; trough levels of rhuMAb
`HER2 were consistently below detectable levels through—
`out the treatment course and until disease progression.
`Antibodies against rhuMAb HER2 (human antihuman an—
`tibodies [HAHA]) were not detected in any patients.
`Treatment with rhuMAb HER2 was remarkably well
`tolerated. Of a total of 768 administrations of rhuMAb
`
`HER2, only 11 events occurred that were considered to
`be related to the use of the antibody (Table 3). Fever and
`chills occurred on five occasions after the first administra-
`tion of rhuMAb HER2. The fever lasted less than 8 hours
`
`in all cases and did not recur on subsequent administra-
`tions of the antibody. Three patients experienced chest
`pain in areas of tumor involvement shortly after the infu-
`sion of the first dose of rhuMAb HER2; in one case this
`
`required an overnight hospital admission for pain control.
`The pain did not recur on successive administrations of
`the antibody. None of the patients whose cancer regres—
`sion met the formal criteria for complete or partial re-
`sponse had pain at a tumor site after administration of
`rhuMAb HER2.
`
`The number of patients assessable for treatment re-
`sponse on evaluation day 77 was 43. Three patients were
`not assessable for response. One had a bacteremic infec—
`tion of an intravenous catheter that required prolonged
`administration of antibiotics, which precluded treatment
`
`Table 2. ECDHE'2-Dependent Pharmacokinetics of rhuMAb HER2
`rhuMAb HER2 t”;
`(days)
`
`Patient Group
`
`All patients
`Circulating ECDHERZ < 500 ng/mL
`Circulating ECDHERZ > 500 ng/mL
`
`8.3 i 5.0
`9.1 i 4.7
`1.8 i 1.0
`
`N
`
`45
`40
`5
`
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`
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`
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`

`rhuMAb HER2 (nglmL)
`
`rhuMAb HER2 (nglmL)
`
`BASELGA ET AL
`
`B 1000
`C
`.9
`E
`
`10
`
`
`
`10
`
`E 8 g
`
`o EE(
`
`Dw
`
`
`
`250300350
`
`'o
`
`50
`
`100
`
`200
`150
`Time (Days)
`
`ECD’E"2 (nglmL)
`
`100
`
`_. o
`
`SerumConcentration
`
`00000000000000000000000000000000000000 4*— LTS
`
`O
`
`50
`
`100
`
`200
`150
`Time (Days)
`
`250
`
`300
`
`350
`
`010 20 30 40 50 60 70 80 90
`
`Time (Days)
`
`ECDHER2 (nglmL)
`
`10000
`
`.5
`a
`15 1000
`
`A
`
`A
`
`A
`
`A A
`
`A
`
`‘
`
`A
`
`A A
`
`100
`
`10
`
`O
`
`
`
`010 20 30
`
`40 50 60 70 80 90
`
`C 8 g
`
`0 Ea
`
`a:
`
`Fig I. Effect of serum ECD"Em on rhuMAb HER2 pharmacokinetics. Stable serum levels of rhuMAb HER2 in a patient with absence of ECD"En
`(A) v suboptimal rhuMAb HER2 serum levels in a patient with high ECD"flu (B). Note that log scales on the Y-axis describing the serum ECD"Em
`differ among charts. LTS, less than lowest assay standard. (0) observed rhuMAb HER2 serum concentration; (0) LTS for rhuMAb HER2 serum
`serum concentration.
`DHER2
`DHERZ
`concentration; (A) EC
`serum concentration; (<>) US for EC
`
`Time (Days)
`
`with rhuMAb HER2. A second declined to continue on
`
`the study for personal reasons. The third died of conges-
`tive heart failure associated with prior doxorubicin treat—
`ment. Among 43 assessable patients, 5 had tumor re-
`sponses: one patient had a complete remission and four
`had partial remissions. Therefore,
`the overall response
`rate (complete plus partial responses) for assessable pa
`tients is 11.6% (95% confidence interval, 4.36 to 25.9).
`Details of responses are listed in Tables 4 and 5, and
`examples of the responses are shown in Fig 2.
`
`Table 3. rhuMAb HER2-Related Toxicity
`Moderate (grade 2)
`
`9
`Severe l rode 3)
`
`l)’
`Toxici
`Fever and chills
`Pain at tumor site
`Diarrhea
`Nausea and emesis
`
`dNNO‘I
`
`NOTE. In number of events of a total of 768 administrations.
`
`Two patients had minor responses and 14 patients had
`stable disease at day 77. These patients entered a mainte-
`nance phase of weekly antibody administration until pro—
`gression of disease. The median time to progression for
`the patients with either minor or stable disease was 5.1
`months. An additional patient had a greater than 50%
`reduction in the size of the metastatic disease on her
`mediastinum and chest wall after 2 weeks of treatment.
`
`While the duration of response was greater than 4 weeks,
`by evaluation day 77 the lesion had begun to regrow from
`the size of maximal response to therapy. Per protocol
`guidelines, this patient was therefore considered not to
`have had a response to therapy, but rather progression of
`disease.
`
`DISCUSSION
`
`During the last decade, overexpression of the HER2
`gene has been shown to play an important role in the
`pathogenesis and poor prognosis of breast cancer. As a
`
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`
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`

`ANTI-HER2 ANTIBODY THERAPY FOR BREAST CANCER
`
`741
`
`Table 4. Response Rate Obtained With rhuMAb HER2
`in 43 Assessable Patients
`
`Response
`
`Complete responsa
`Partial response
`Overall response
`
`Minor response
`Stable disease
`Progression of disease
`
`No. of Patients
`
`1
`4
`5
`
`2
`14
`22
`
`%
`
`2.3
`9.3
`11.6
`
`4.6
`32.6
`51 .2
`
`interference with
`consequence, strategies directed at
`HER2 expression or the function of its protein, pISSHERZ,
`have been anticipated to have therapeutic value. Exten-
`sive preclinical studies have shown that certain MAbs
`directed against p185HER2 can inhibit growth of HER2-
`overexpressing tumor cells.”19 This study provides the
`first clinical evidence of the antitumor activity of one of
`these agents, rhuMAb HER2.
`Of 43 patients with pISSHE’u-positive tumors assess—
`able for response after treatment with rhuMAb HER2,
`five experienced a complete or partial remission, for an
`overall response rate of 11.6%. One additional patient
`had a greater than 50% shrinking of her cancer that lasted
`more than 1 month, but was not considered a responder by
`our protocol definition. The objective antitumor responses
`observed were of clinical importance, since two patients
`had regression of cancers in the liver and one patient
`achieved a pathologically-proven complete response of
`chest wall disease, which has persisted for 24 months. Our
`patients were selected to have many sites of metastatic
`involvement, one of the most dire prognostic characteris-
`tics regarding response to therapy. This selection was
`the consequence of the rule that patients with disease
`involving only bone were ineligible for accrual, because
`
`bone is the solitary site of initial metastatic involvement
`in up to 60% of cases.27 It is reasonable to hypothesize
`that the percentage of patients who show objective tumor
`regression to rhuMAb HER2 will be higher when patients
`with less extensive breast cancer are treated, since labora-
`
`tory studies have shown that the response to antireceptor
`antibodies is greater with lower tumor burden.28 It would
`be also of interest to analyze the response rate to rhuMAb
`HER2 in a patient population with no prior chemotherapy
`for stage IV disease, since prior experience has shown
`that untreated patients usually respond better to new anti-
`cancer drugs.29
`Another important point about the probability of re-
`sponse to rhuMAb HER2 concerns the observation that
`37% of patients achieved minimal responses or stable
`disease. In the laboratory, rhuMAb HER2 or the parent
`antibody 4D5 has been noted to be cytostatic, which
`causes growth arrest, rather than cytocidal, which causes
`cell death. In clinical trials of many anticancer drugs,
`particularly chemotherapy, the achievement of stable dis—
`ease is not considered a reliable measure of anticancer
`
`activity. However, with rhuMAb HER2, stable disease
`may be an authentic reflection of the biologic action of
`the drug, which differs markedly from conventional anti-
`cancer agents. The unusually long durations of minimal
`responses and stable disease seen in our trial may relate
`to this distinction. These data are specially interesting in
`light of the absence of significant toxicity observed here,
`for in a setting in which palliation is a main objective,
`quality of life while on treatment should be a main end
`point.
`The dose and schedule of rhuMAb HER2 administra-
`
`tion used in this protocol provided adequate serum con-
`centrations in all patients, except in those with circulating
`levels of tumor-shed ECDHERZ at serum concentrations a
`
`Patient No.
`
`HER2‘
`
`Site of Metastatic Disease
`
`Prior Systemic Therapy
`
`Best Response
`
`Duration at Response (months)
`
`Table 5. Characteristics of Patients Who Achieved a Response to Treatment
`
`1
`2
`
`3
`
`4
`
`5
`
`3+
`3+
`
`2+
`
`3+
`
`2+
`
`Chest wall
`Liver
`
`Mediastinum
`
`Liver + retroperitoneal lymph
`nodes 4- bone
`Chest wall
`
`Doxorubicin
`Doxorubicin, mitoxantrone,
`paclitaxel
`CMFVP, doxorubicin,
`tamoxiten, paclitaxel
`CMF, docetaxel
`
`Paclitaxel
`
`Complete response‘l’
`Partial response
`
`Partial response
`
`Partial response
`
`Partial response
`
`> 24
`6.7
`
`7.7
`
`1
`
`3.4
`
`Abbreviations: CMFVP, cyclophosphamide, methotrexate, fluorouracil, vincristine, and prednisone; CMF, cyclophosphamide, methotrexate, and lluoro-
`uracil.
`
`‘By immunohistochemistry: 2+, 2.5% to 50% of tumor cells with cytoplasmic membrane staining; 3+, > 50% of tumor cells with cytoplasmic membrane
`staining.
`TPatient’s complete response was pathologically proven with several biopsies at tumor site. Patient bone scan, head, thoracic, abdominal, and pelvic
`computed tomographic scans are negative.
`
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`

`742
`
`BASELGA ET AL
`
`
`
` Fig 2. Patient with exten-
`
`sive liver disease before treat-
`ment with rhuMAb HER2 (A)
`and 8 months into treatment
`showing marked reduction in
`liver involvement (B). Patient
`with chest wall recurrence be-
`fore start treatment
`(C,
`left)
`and l year later showing com-
`plete resolution of disease (C,
`right). Visible scars are from
`multiple biopsies that con-
`firmed histologically the ab-
`sence of tumor.
`
`500 ng/mL. ECDHERZ is known to be released by some
`breast cancer cells that overexpress HER2,3°'32 and ele-
`vated ECDHERZ serum levels have been previously re-
`ported in patients with breast cancer.3“33'34 The most
`likely explanation for the short serum tm values and
`subtherapeutic trough levels of rhuMAb HER2 in this
`group of patients is that in the presence of ECDHERZ in the
`serum, antigen—antibody complexes form and are rapidly
`cleared from the circulation. Of interest, no anticancer
`responses were observed in the group of patients with
`serum concentrations of ECDHERz 2 500 ng/mL. Hence,
`the interpretation of results of future trials of agents that
`bind to or exert their function through p185HER2 should
`take ECDHERZ release from the tumors into account; at
`
`present, patients with high levels of ECDHERZ should con—
`tinue to participate in these studies.
`There are several possible mechanisms, not mutually
`exclusive, that could explain the clinical results observed.
`An important fact is that rhuMAb HERZ induces a marked
`
`downregulation of p185”ER2.lg Antibody—induced down—
`regulation of p185HER2 has been shown to induce rever-
`sion of the transformed phenotype in HERZ-transformed
`cells.14 By a similar mechanism, the continuous exposure
`to rhuMAb HER2 at adequate concentrations achieved in
`our trial could be reversing the malignant phenotype of
`the clinical cancers by downregulating their level of
`p185HER2. Another possibility is that the known partial
`agonistic effects of rhuMAb HERZ35 could result in the
`activation of a signal transduction pathway that leads to
`inhibition of tumor-cell proliferation. Both of these poten-
`tial antitumor mechanisms would require, in addition to
`receptor expression,
`intact receptor function. Little is
`known about the functional status of p18SHER2 in breast
`tumor specimens, but it is conceivable that not all overex—
`pressing tumors have functional receptors. In support of
`this View is the observation that HER2—overexpressing
`tumor-cell lines that are not growth—inhibited by anti-
`p18SHER2 antibodies have been described and well charac-
`
`Downloaded from ascopubs.org by Bodleian Health Care Library on January 29, 2017 from 129.067.118.107
`Copyright © 2017 American Society of Clinical Oncology. All rights reserved.
`
`InnoPharma Exhibit 1083.0006
`
`

`

`ANTI-HER2 ANTIBODY THERAPY FOR BREAST CANCER
`
`743
`
`terized“; it is noteworthy that some of these antibody-
`resistant tumor cells also overexpressed truncated forms
`of ECDHERZ. Furthermore, in vitro studies suggest that
`those breast cancer cell lines that have the highest basal
`level of p185HERZ phosphorylation are the most growth-
`inhibited by anti—p185HERz antibodies.20 If this were the
`case in the clinic, the recently produced antiserum that
`specifically recognizes only overexpressed tyrosine-phos—
`phorylated p185HER2 might prove useful in predicting the
`subset of p185HER2-positive tumors most likely to respond
`to rhuMAb HER2.8
`
`Another possible mechanism of action concerns the
`observation that rhuMAb HER2 is a potent inducer of
`ADCC.22 However, while this immune—mediated mecha-
`nism might play a role in the observed clinical responses,
`ADCC is obviously not
`involved in the pronounced
`growth-inhibitory effects of the antibody in vitro.
`The observed activity of rhuMAb HER2 against ad—
`vanced breast cancers that overexpress HER2 provides
`the first clinical evidence that anti— growth factor recep-
`tor-directed strategies may be useful in the treatment of
`human breast cancer. Therefore, continued research with
`
`this agent and other HER2-targeted treatment strategies
`appears warranted. The response to rhuMAb HER2 in a
`less heavily pretreated population and in those with less
`
`extensive metastatic disease would be of interest since
`
`both parameters have historically correlated with a higher
`response to drugs,29 and this same principle may apply
`to antibody-based therapy.37 In preclinical studies, both
`in vitro and in xenografts, rhuMAb HER2 markedly po-
`tentiated the antitumor effects of several chemotherapeu—
`tic agents,
`including cisplatin, doxorubicin, and pacli-
`taxel,”38 without
`increasing their toxicity. Laboratory
`studies of the mechanism of this effect and clinical trials
`
`of such combination therapy are currently in progress.
`
`ACKNOWLEDGMENT
`
`We are indebted to Drs Mary Ellen Moynahan, George Raptis,
`Violante E. Currie, David W. Fennelly, John P. Crown (Department
`of Medicine), and Patrick Borgen (Department of Surgery), Memo-
`rial Sloan—Kettering Cancer Center, for accrual and care of patients;
`Katherine Trainer for data management (Memorial Sloan-Kettering
`Cancer Center); Judy Tomsic and Anita Harrison for data manage-
`ment and Dr David Kim, Diane Craig, Diane Kennedy, and Becki
`Moore for care of patients (University of California, San Francisco);
`and Gracie Lieberman, Maureen Ash, and Annabel Vaghar (Genen-
`tech Inc) for data and statistical analysis; and Andrew Nuijens,
`Cheryl Schofield, Wai Lee Wong, and Deborah Baly (Genentech
`Inc) for their tremendous efforts in developing and interpreting data
`from the assays for rhuMAb HER2 serum concentrations, extracellu—
`lar domain of p185HER2 (ECDHERZ), and the presence of antibodies to
`rhuMAb HER2. We also acknowledge Mark Sliwkowski (Genentech
`Inc) for careful review of the manuscript and useful suggestions.
`
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