Phase I Study of U3-1287, a Fully Human Anti-HER3 Monoclonal …clincancerres.aacrjournals.org/content/clincanres/early/2013/04/16/... · Phase I Study of U3-1287, a Fully Human Anti-HER3

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Phase I Study of U3-1287, a Fully Human Anti-HER3 Monoclonal Antibody, in Patients

With Advanced Solid Tumors

Patricia LoRusso1, Pasi A. Jänne2, Moacyr Oliveira3, Naiyer Rizvi4, Lisa Malburg1, Vicki

Keedy5, Lorrin Yee6, Catherine Copigneaux7, Thore Hettmann8, Chi-Yuan Wu9, Agnes Ang9,

Abdel-Baset Halim7, Robert A. Beckman7, Darrin Beaupre9, and Jordan Berlin5

1 Karmanos Cancer Institute, Wayne State University, Detroit, Michigan; 2 Dana-Farber Cancer

Institute, Boston, Massachusetts; 3 Northwest Medical Specialties, Tacoma, Washington; 4

Memorial Sloan-Kettering Cancer Center, New York, New York; 5 Vanderbilt University

Medical Center, Nashville, Tennessee; 6Vista Oncology, Olympia, Washington; 7 Daiichi

Sankyo Pharma Development, Edison, New Jersey; 8 U3 Pharma GmbH, Munich, Germany; and

9 Amgen Inc., Thousand Oaks, California

Running head: Phase I Study of U3-1287 in Patients With Advanced Solid Tumors

Keywords: HER3, U3-1287

Acknowledgment of research support: The study was sponsored by Daiichi Sankyo

Pharmaceutical Development and Amgen, Inc.

Corresponding author: Patricia M. LoRusso, Karmanos Cancer Institute, 4100 John R St.,

Detroit, MI 48201; phone: 313-576-8716; fax: 313-576-8719; e-mail: [email protected].

Conflict of interest disclosure: Darren Beaupre, Chi-Yuan Wu, and Agnes Ang are employed by

and own stock in Amgen, Inc. Thore Hettmann is an employee of U3 Pharma. Abdel Halim,

Robert Beckman, and Catherine Copigneaux are employees of Daiichi Sankyo Pharmaceutical

Development, and Robert Beckman and Catherine Copigneaux own stock in Daiichi Sankyo

Pharmaceutical Development. Jordan Berlin has served as a consultant to Amgen and received

Research. on January 20, 2020. © 2013 American Association for Cancerclincancerres.aacrjournals.org Downloaded from

Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Author Manuscript Published OnlineFirst on April 16, 2013; DOI: 10.1158/1078-0432.CCR-12-3051

http://clincancerres.aacrjournals.org/

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research funding from Amgen, Inc. Vicki Keedy has received research funding from Daiichi

Sankyo Pharmaceutical Development and Amgen, Inc. Patricia LoRusso has received research

funding from U3 Pharma. Lisa Malburg, Naiyer Rizvi, Lorrin Yee, and Moacyr Oliveria have

no conflicts of interest to disclose.

Word count:

Abstract: 236

Text, excluding references: 3374

Figures: 3

Tables: 3

Previously published, in part, in:

LoRusso P, Keedy V, Yee L, et al: A phase 1, open-label, dose-finding study to assess the

safety and tolerability of U3 1287 (AMG 888), a human monoclonal antibody targeting HER3

in patients with advanced solid tumors. Presented as a poster at EORTC-NCI-AACR 2010 and

published as an abstract in Eur J Cancer 8:76, 2010 (suppl; abtr 234)

Berlin J, Keedy VL, Janne PA, et al: A first-in-human phase I study of U3-1287 (AMG 888), a

HER3 inhibitor, in patients (pts) with advanced solid tumors. Presented as a poster at ASCO

2011 and published as an abstract in J Clin Oncol 29:200s, 2011 (suppl; abstr 3026)




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Translational Relevance

Agents targeting human epidermal growth factor 1 (HER/EGFR) and 2 (HER2) have been of

intense interest, but their efficacy in the clinic has been confined to subsets of patients. Research

indicates that the related protein HER3 is important in tumorigenesis, as it activates oncogenic

signaling pathways, is upregulated in many solid tumors, and is associated with poor prognosis

in cancer patients. Although devoid of kinase activity itself, HER3 is recognized as a key

dimerization partner for other HER family members, and HER3:HER2 heterodimers

demonstrate particularly potent mitogenic signaling. However, therapeutic inhibition of HER3

has not previously been clinically evaluated. We present results from the first-in-human study of

U3-1287, a first-in-class HER3-targeting monoclonal antibody. Therapy with U3-1287 was well

tolerated and resulted in stable disease and tumor reductions in some patients. Our study lays

the foundation for further research into U3-1287 and HER3 inhibition for the treatment of solid

tumors.




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ABSTRACT

Purpose: Human epidermal growth factor receptor 3 (HER3) is a key dimerization partner for

other HER family members, and its expression is associated with poor prognosis. This first-in-

human study of U3-1287 (NCT00730470), a fully human anti-HER3 monoclonal antibody,

evaluated its safety, tolerability, and pharmacokinetics (PKs) in advanced solid tumor patients.

Experimental Design: The study was conducted in 2 parts: part 1—sequential cohorts received

escalating doses (0.3–20 mg/kg) of U3-1287 every 2 weeks (q2w), starting 3 weeks after the

first dose; part 2—additional patients received 9, 14, or 20 mg/kg U3-1287 q2w, based on

observed tolerability and PKs from part 1. Recommended phase II dose, adverse event (AE)

rates, PKs, and tumor response were determined.

Results: Fifty-seven patients (part 1: 26; part 2: 31) received U3-1287. As no dose-limiting

toxicities were reported, the maximum tolerated dose was not reached. The maximum

administered dose was 20 mg/kg q2w. The most frequent AEs related to U3-1287 were fatigue

(21.1%), diarrhea (12.3%), nausea (10.5%), decreased appetite (7.0%), and dysgeusia (5.3%).

No patient developed anti–U3-1287 antibodies. In these heavily pretreated patients, stable

disease was maintained ≥ 9 weeks in 19.2% in part 1 and ≥ 10 weeks in 25.8% in part 2.

Conclusion: U3-1287 treatment was well tolerated, and some evidence of disease stabilization

was observed. PK data support U3-1287 dosing of 9 to 20 mg/kg every 2 to 3 weeks.

Combination studies of U3-1287 are ongoing.




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INTRODUCTION

The human epidermal growth factor receptor (EGFR/HER) family of receptor tyrosine kinases,

consisting of HER1 (EGFR), HER2, HER3, and HER4, plays an important role in oncogenesis.

By homodimerizing and heterodimerizing, HER family members activate signaling pathways

that are involved in cellular processes, including morphogenesis, proliferation, angiogenesis,

and survival.(1–4) A number of tumor types require EGFR or HER2 signaling for growth and

survival,(5–7) prompting the development of various therapeutic agents that target the EGFR

and HER2 receptors. Current anti-EGFR and anti-HER2 agents, however, have proven to be

effective only in a subset of patients, and initial response is frequently followed by relapse and

the development of therapeutic resistance. Recent studies suggest that HER3 upregulation or

reactivation is important to the development of resistance to EGFR- and HER2-targeted

treatments.(8–11)

Elevated HER3 expression has been detected in many tumor types and is associated with

negative clinical prognosis, including shorter relapse-free survival time in breast cancer (12) and

shorter overall survival times in lung, ovarian, and colon cancers.(13–16) HER3 is also

overexpressed and occasionally amplified in non–small cell lung cancer (NSCLC), and

autocrine loops with its ligands have been documented.(13,17–20) While lacking intrinsic

kinase activity itself,(21,22) HER3 activates signaling pathways through heterodimerization

with other HER family members. HER2:HER3 heterodimers demonstrate particularly potent

mitogenic signaling compared with other HER family heterodimers.(23) Targeting HER3,

therefore, may negatively affect tumors and improve the efficacy of current anti-HER agents.

U3-1287 (NCT00730470) is a first-in-class, fully human monoclonal antibody directed against

HER3. In vitro, U3-1287 binds to the extracellular domain of HER3 and promotes receptor

internalization, inhibiting both basal and ligand-induced receptor signaling.(24–26) Tumor cells




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treated with U3-1287 demonstrate reduced cellular migration, proliferation, and anchorage-

independent growth. In addition, U3-1287 and anti-EGFR antibody treatment of EGFR- and

HER3-expressing xenografts significantly reduced tumor growth compared with anti-EGFR

antibodies alone or with an isotype immunoglobulin (IgG) control in both EGFR wild-type

models and resistant models with the T790M EGFR mutation.(27)

A phase I, open-label, first-in-human study of single-agent U3-1287 was initiated to assess its

safety, tolerability, and pharmacokinetic (PK) profile in patients with advanced solid tumors.

The study was conducted in 2 parts. Part 1 was a dose-escalation, dose-finding study designed

to identify the maximum tolerated dose (MTD) by treating successive cohorts with escalating

doses and evaluating the incidence of dose-limiting toxicities (DLTs). Part 2 was a dose-

expansion phase conducted in patients with advanced malignancies along with an exploratory

NSCLC cohort that further evaluated the safety, tolerability, and efficacy of the possible dose

levels identified from part 1 PK in the intended phase II population. This report describes results

from both parts of this study.

MATERIALS AND METHODS

Patients

For parts 1 and 2, eligible patients had a confirmed diagnosis of an advanced solid tumor that

was refractory to standard treatment or for which no standard therapy existed and that was of a

type known to express HER3. For part 2, the same eligibility criteria were used, but an

exploratory cohort was included in which ≥ 15 of 30 patients enrolled had to have NSCLC.

Patients were not preselected on the basis of RAS or EGFR status. All patients were ≥ 18 years

of age, had an Eastern Cooperative Oncology Group performance status of 0 to 2, and a life

expectancy of > 3 months. Additional inclusion criteria included controlled hypertension

(diastolic ≤ 100 mm Hg; systolic ≤ 140 mm Hg), left ventricular ejection fraction ≥ 50%,




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cumulative anthracycline exposure ≤ 360 mg/m2, and adequate neutrophil count (≥ 1,500/µL),

hemoglobin count (≥ 9 g/dL), platelet count (≥ 100,000/µL), calculated creatinine clearance

level (modified Cockcroft-Gault equation; ≥ 60 mL/min), bilirubin level (≤ 2 × upper limit of

normal [ULN]), prothrombin time or partial prothrombin time (≤ 1.5 × ULN), alkaline

phosphatase level (≤ 2 × ULN with no liver or bone involvement or < 5 × ULN with liver or

bone involvement), and alanine aminotransferase (ALT) and aspartate aminotransferase (AST)

levels (≤ 2.5 × ULN with no liver involvement or < 5 × ULN with liver involvement). Patients

were ineligible if they had previously received an anti-HER3–targeted antibody or if they had

received small molecule tyrosine kinase inhibitors within 2 weeks; major surgery, antibody

therapy, retinoid therapy, hormonal therapy, or therapeutic or palliative radiotherapy within 4

weeks; or nitrosoureas or mitomycin C chemotherapies within 6 weeks of the first dose of U3-

1287. Patients with hematopoietic malignancies, untreated or symptomatic brain metastases, or

known HIV or active hepatitis B or C virus infection were ineligible. The study protocol was

approved by participating institutions' research ethics boards, and each patient signed a consent

form.

Study design and dosing

This was a multicenter study conducted in 2 parts. In part 1, dose escalation followed a

modified 3 + 3 study design: 3 or 4 patients were enrolled initially in sequential cohorts of 0.3,

1, 3, 6, 9, 14, and 20 mg/kg. U3-1287 was administered as an intravenous (IV) infusion over 60

minutes. After the first IV administration of U3-1287 on day 1, a 21-day observation period

occurred for each patient. If no DLTs were observed during the first 21 days, U3-1287

administration began on day 22 and was administered every 14 days. In part 2, the initial dose

for dose expansion was determined on the basis of preliminary safety and PK through cohort 5

(9 mg/kg) from the dose-escalation phase of the study. The dose of 9 mg/kg was the first dose




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that produced a trough drug level 10-fold greater than the trough level that corresponded to

maximal preclinical efficacy. Escalating doses administered in part 2 of the study were 9, 14,

and 20 mg/kg, administered IV on days 1 and 15 of a 28-day cycle.

DLT was defined as drug-related grade 3 or higher hematologic or nonhematologic toxicity

(except alopecia); for fatigue, only grade 3 fatigue that persisted for > 7 days or grade 4 fatigue

of any length were included. For patients with bone or liver metastases and baseline levels ≥ 2.5

× ULN (for alkaline phosphatase > 2 × ULN), DLTs did not include elevations in AST, ALT, or

alkaline phosphatase unless the following criteria were met: AST or ALT > 8 × ULN (if

baseline was 2.5–5 × ULN in patients with liver metastases); alkaline phosphatase > 8 × ULN

(if baseline level was 2–5 × ULN in patients with bone or liver metastases). DLT assessment

followed the guidelines provided in the Common Terminology Criteria for Adverse Events

(CTCAE), v.3.0. MTD was defined as the highest dose with an observed incidence of DLT in

fewer than 33% of the patients in the cohort.

Tumor response and safety

In part 1 of the study, disease response assessment using modified Response Evaluation Criteria

in Solid Tumors (RECIST; 28) was performed at screening, days 35 and 64, and every 8 weeks

thereafter. In part 2 of the study, disease response assessment occurred at screening, days 42 and

70, and every 8 weeks thereafter. 2-deoxy-2-(18F)fluoro-D-glucose positron emission

tomography/computed tomography scans were performed after eligibility was determined and

within 14 days prior to the first dose of study drug (baseline) and on day 42 in part 1 (cohorts 3

through 7) and part 2 (all cohorts), once dose levels that might be pharmacodynamically active

had been achieved. Metabolic response was assessed as described by Young et al.(29)

All adverse events (AEs) were recorded from the time of informed consent until 30 days after

the last dose of U3-1287 and were graded according to CTCAE v.3.0. Scheduled 12-lead




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electrocardiograms were performed during screening at days 1, 15, 29, 57, and every 4 weeks

thereafter. QTc interval was evaluated centrally and corrected for heart rate by the Fridericia’s

formula (QTcF).

PK evaluation

During part 1, PK evaluation was conducted on all patients on day 1 of treatment (blood

samples taken at end of infusion [EOI], and at 3, 6, 24, and 72 hours after EOI), and on days 7,

14, and 21. Samples were also obtained immediately before the third dose (day 36), at EOI, at 3

and 6 hours after EOI, and on days 37, 39, and 42. Preinfusion and EOI PK samples were also

taken on days 22, 50, and 64, and every 8 weeks thereafter. The PK parameters (area under the

plasma concentration-time curve [AUC], maximum observed serum concentration [Cmax], and

half-life [t1/2]) were derived from serum concentration–time data following doses 1 and 3 during

part 1 and then calculated by noncompartmental analysis using WinNonlin® Enterprise v5.1.1

(Pharsight Corp., Mountain View, CA).

Immunogenicity

Blood samples for determining anti–U3-1287 antibodies in serum were collected in part 1

before dosing on day 1 and on day 21, day 64, and every 8 weeks thereafter, as well as during

an end-of-study visit. In part 2, blood samples were collected before dosing on days 1, 29, and

57, and then every 8 weeks and at the end-of-study visit.

HER3 assays

HER3 gene amplification status and protein expression were assessed by fluorescence in situ

hybridization (FISH) and immunohistochemistry (IHC), respectively, in archived, formalin-

fixed, paraffin-embedded (FFPE) tumor tissues. For FISH, tissue sections were evaluated

through incubation with the dual color probe set ZytoLight® SPEC HER3/CEN 12 (Zytovision,




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Bremerhaven, Germany) and scored both by absolute copy number and amplification ratio. For

IHC, tissue sections were incubated with mouse IgG antihuman HER3 (sc81455, Santa Cruz

Biotechnology) and scored as a percentage of positive cells and on a semiquantitative scale

using H-scores for total HER3 in the cytoplasm and membrane. Samples were analyzed by a

single pathologist who was blinded to clinical outcomes.

RESULTS

Patients

Twenty-six patients were enrolled in part 1, and 31 patients were enrolled in part 2.

Demographics and clinical characteristics are summarized in Table 1. The most common

primary tumor sites were colorectal (50.9%) and NSCLC (35.1%); 17 of the 20 patients with

NSCLC were specifically enrolled into the dose-expansion cohorts.

All patients had received chemotherapy, with a median of 5 previous regimens. Forty-one

patients (71.9%) received prior EGFR-targeted therapy, of which 3 patients (7.3%) had partial

response (PR) as a best response to prior EGFR-targeted treatment, 14 patients (34.1%) had a

best response of stable disease (SD), and 16 patients (39.0%) had progressive disease (PD). The

best response on prior EGFR-targeted therapy was unknown for 8 patients (19.5%).

All patients received at least 1 dose of U3-1287. Fifty-two patients (91.2%) withdrew from

study because of disease progression, 2 patients (3.5%) because of full withdrawal of consent

(unrelated to any study-related event), 2 patients (3.5%) because of nonfatal AEs (grade 2

prolonged QTc interval [20 mg/kg] and grade 3 pulmonary embolism [20 mg/kg]), and 1 patient

because of a fatal AE (grade 5 respiratory insufficiency [14 mg/kg]); all were considered

unrelated to U3-1287.




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Safety

Most patients (55 [96.5%]) had at least 1 AE. Approximately half of the patients (47.3%) had

AEs with a highest grade of 1 or 2. The most common AEs overall (≥ 20% of patients) included

fatigue (42.1%), diarrhea (24.6%), nausea (22.8%), and dyspnea (21.1%; Table 2). Based on

this limited sample set, it did not appear that any AEs were dose-dependent. U3-1287–related

AEs were reported in 26 patients (45.6%) and included fatigue (21.1%), diarrhea (12.3%),

nausea (10.5%), decreased appetite (7.0%), and dysgeusia (5.3%). Nearly all drug-related events

were grade 1 or 2; only 1 patient (3 mg/kg) had a drug-related AE that was grade ≥ 3 (a

nonserious grade 3 event of hyponatremia on day 20 and a nonserious grade 3 event of

hypophosphatemia on day 23). Both events were possibly related to study medication. There

were no grade 4 or 5 U3-1287–related AEs.

Overall, 6 patients experienced 7 grade ≥ 4 events; none were related to U3-1287. Nineteen

patients (33.3%) had a serious AE; none were deemed related to U3-1287. Eight patients

discontinued study treatment due to 10 AEs, none of which were judged to be related to

treatment with the study drug.

One patient had asymptomatic grade 2 QTcF prolongation, and 3 female patients had

asymptomatic QTcF between 450 and 470 ms (normal for females). Analysis of QTcF

prolongation as a function of U3-1287 serum concentration showed no concentration

dependence (see Supplementary Fig. S1).

No DLTs were reported for any of the cohorts during the DLT observation window. Thus, the

MTD was not reached and is therefore not lower than the maximum dose administered in this

study (20 mg/kg).




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Pharmacokinetics

PK parameters for dosing cohorts in part 1 are summarized in Table 3. The Cmax and AUC of

U3-1287 increased more than dose-proportionally across the tested range (0.3–20 mg/kg). PK

approached linearity at the higher doses studied (6–20 mg/kg), indicating that saturation of

clearance pathways occurs at doses greater than 6 mg/kg. Mean serum t1/2 was approximately 8

days at doses > 6 mg/kg. Data from PK analysis of part 2 indicate that in patients treated with 9,

14, or 20 mg/kg every 2 weeks (q2w), steady state was achieved after approximately 3 doses. At

dose levels ≥ 9 mg/kg, the mean minimum observed serum concentration (Cmin) beyond the

second dose was at least 10-fold greater than the Cmin associated with maximal efficacy in

mouse xenograft models (90% inhibitory concentration [IC90] ≈ 3 µg/mL; Fig. 1; ref. 30).

Owing to this, as well as the simulation of the q2w and every 3 week (q3w) dosing data, the PK

profile of U3-1287 supports IV administration at or above 9 mg/kg q2w or q3w.

Immunogenicity

No patient developed human antihuman antibodies (HAHAs) after dosing with U3-1287. One

of 26 patients tested during part 1 and 1 of 31 patients tested during part 2 had positive HAHA

results before and after exposure to U3-1287, as detected by immunoassay. No neutralizing

antibodies were detected at any visit for either patient; therefore, the HAHAs detected were

present before dosing and were nonneutralizing.

Efficacy

In the 51 patients evaluable for tumor response, SD at the earliest observation time point was

the best single-evaluation response in 50.9% of patients. In part 1, SD was recorded in 1 or

more evaluations in 53.8% of patients and maintained for at least 16 weeks in 7.7% of patients.

In part 2, SD was recorded in at least 1 evaluation in 48.4% of patients and maintained for at




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least 16 weeks in 16.1% of patients (Fig. 2). Twenty-two patients (38.6%) had PD. No patient

had complete response or PR per modified RECIST. One patient with NSCLC (20 mg/kg) had

tumor shrinkage (26.3% decrease) that approached but did not reach the 30% reduction

threshold for PR (Fig. 3).

The overall metabolic response rate was 3.5%: the previously mentioned NSCLC patient and 1

patient in part 1 (14 mg/kg) had partial metabolic responses. Both patients were nonsmokers

who had received prior EGFR-targeted therapy. The first patient previously had a best response

of SD while receiving erlotinib-based therapy and, in this study, had SD for 42 weeks. The

second patient previously had PD while receiving cetuximab-based therapy and, in this study,

was removed for PD after the first tumor assessment post-therapy; however this patient had SD

per central review that lasted 32 days. No clear dose response could be discerned given the

limited number of responders. Overall in this study, 24.6% of patients had SD, 40.4% had PD,

and 31.6% were not evaluable for metabolic tumor response.

Pharmacodynamic and predictive biomarker evaluations

Expression of HER3 was investigated at the gene copy number level by FISH and at the protein

expression level by IHC in FFPE tissue sections. Patient subgroups defined using varying cutoff

values for gene copy number or amplification ratios, or by protein expression levels, were

evaluated for clinical outcome (PD or SD) to identify possible correlations. Results show a

trend toward higher proportions of SD patients than PD patients belonging to the subgroups

defined by the highest cutoff values for gene copy number or protein expression levels, but this

exploratory result requires independent confirmation.

Phospho-HER3 was examined as a potential pharmacodynamic and tissue biomarker; however,

research using tissue microarrays indicated that the phospho-HER3 epitope is not stable in

archived tissue, and fresh tissue could not be examined because patients were not prospectively




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biopsied. Attempts to assay the HER3 ligand heregulin by either IHC or quantitative

polymerase chain reaction are still ongoing.

DISCUSSION

This first-in-human study of U3-1287, a first-in-class HER3-targeted fully human monoclonal

antibody, supports dosing regimens at a range of 9 to 20 mg/kg U3-1287 q2w or q3w. U3-1287

exhibited a favorable safety profile and preliminary evidence of antitumor activity.

The most frequently reported AEs included fatigue, diarrhea, nausea, and dyspnea. This small

patient cohort did not provide clear evidence of a dose-dependent relationship for toxicity. Most

incidences of U3-1287–related events were mild to moderate (grades 1 or 2). There were no

grade 4 or 5 AEs related to U3-1287, and no treatment discontinuations were attributed to a U3-

1287–related AE.

The development of neutralizing antibodies against therapeutic monoclonal antibodies in a

patient can lead to the loss of efficacy or to more serious clinical effects. As U3-1287 is a fully

human antibody, immunogenicity was not expected to be a concern, and, consistent with this,

no neutralizing anti–U3-1287 antibodies were detected in this patient population following

exposure to U3-1287. PK results and simulations from q2w dosing suggest that doses 9 mg/kg

q3w and above achieve steady state trough levels 10-fold in excess of those corresponding to

maximal efficacy in mice. Preclinical experiments showed a correlation between trough

concentrations and pharmacodynamics, as assessed by reductions in phospho-HER3 levels (see

Supplementary Fig. S2). Variation of treatment schedule around a constant dose suggested that

trough levels are more important to pharmacodynamics than peak levels in the murine system.

However, a number of factors affecting the ability of an antibody to penetrate solid tumors (e.g.,

variable intervessel distances and high interstitial pressure [31]) may be less prominent in the

smaller tumors of mice. Therefore, the results from murine studies cannot be directly translated




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into recommended dose levels for humans, and, thus, 9 mg/kg q3w may be viewed as the

minimal dose level needed to achieve a significantly higher concentration in humans than is

required in murine systems. U3-1287 has demonstrated an acceptable safety profile in doses up

to 20 mg/kg q2w; therefore, it is recommended that doses of 9 to 20 mg/kg q2w or q3w be used

for collecting further safety, efficacy, and biodistribution data. Ongoing clinical studies are

utilizing U3-1287 q3w dosing regimens for enhanced patient convenience. While

pharmacodynamic activity could not be effectively assessed in this study to confirm dose

selection, 2 independent studies are in progress to refine dose selection: a radiolabeled

biodistribution study and a dose-ranging phase I/II study in combination with erlotinib, another

HER family inhibitor.

HER3 has been shown to be a major activator of phosphatidylinositol 3-kinase/Akt signaling in

EGFR-addicted and HER2-amplified cancers.(11,32,33) Previous studies have correlated

elevated HER3 expression with poor prognosis in a number of tumor types.(12–16) There was a

trend in this patient population toward the association of clinical benefit with high levels of

HER3 amplification or expression. However, due to the large number of exploratory

comparisons, independent confirmation is required. This association was not sufficient to allow

patient stratification and needs further examination in additional studies, including in more

homogeneous populations and in the context of combination therapy. Total HER3 expression

might also be considered for incorporation into a multicomponent classifier for patient selection

in the future. Assays to look at pathway activation and presence of ligand, rather than simple

receptor expression, are under development but remain a challenge in archived tissues.

Early evidence of clinical activity for U3-1287 in a selected population was suggested by

several patients with prolonged SD and/or metabolic responses. It has been suggested that

activated HER3 plays a role in the development of resistance to HER2 and EGFR inhibitors and




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that the use of a HER3 inhibitor, such as U3-1287, may prevent or overcome such resistance if

used in combination with these agents. The safety and PK profile of U3-1287 monotherapy in

this population favors future studies of this agent in combination regimens, particularly with

anti-EGFR– and anti-HER2–based therapies used in colorectal, head and neck, and breast

cancers.(18,34,35) A phase I/II trial is ongoing to examine U3-1287 (9 or 18 mg/kg q3w) in

combination with erlotinib in NSCLC patients.

Acknowledgments

We would like to thank Xiaoping Jin and Erik Rasmussen for statistical support, Emily Liu for

clinical operational support, Alin Chen for pharmacokinetic calculations, Daniel Freeman and

Jeanne Mendell-Harary for advice on pharmacokinetic and pharmacodynamic issues, and

Cheryl Chun (BlueMomentum) for medical writing assistance. Funding for medical writing

support was provided by Daiichi Sankyo.




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22

Table 1. Patient demographics and characteristics

Characteristic Dose-escalation

study (n = 26)

Dose-expansion

study (n = 31)

Total (N = 57)

Sex, n (%)

Male 19 (73.1) 13 (41.9) 32 (56.1)

Female 7 (26.9) 18 (58.1) 25 (43.9)

Age, y

Median (range) 56.5 (39–75) 62.0 (39–80) 60.0 (39–80)

ECOG score, n (%)

0 5 (19.2) 13 (41.9) 18 (31.6)

1 19 (73.1) 17 (54.8) 36 (63.2)

2 2 (7.7) 1 (3.2) 3 (5.3)

Prior chemotherapy, n (%) 26 (100) 31 (100) 57 (100)

Median number (range) 5.5 (2–13) 5.0 (2–10) 5.0 (2–13)

Prior EGFR-baseda, n (%) 16 (61.5) 25 (80.6) 41 (71.9)

Prior HER2-baseda, n (%) 1 (3.8) 1 (3.2) 2 (3.5)

Prior radiotherapy, n (%) 13 (50) 15 (48.4) 28 (49.1)

Tumor type, n (%)

Head and neck 0 1 (3.2) 1 (1.8)

Breast 3 (11.5) 1 (3.2) 4 (7.0)

Ovary 1 (3.8) 1 (3.2) 2 (3.5)

Lung

NSCLC 3 (11.5) 17 (54.8) 20 (35.1)

SCLC 1 (3.8) 0 1 (1.8)

Colorectal 18 (69.2) 11 (35.5) 29 (50.9)




23

Years since metastatic diagnosis,

median (range)

2.61 (0.2–7.3) 3.50 (0.5–7.4) 2.69 (0.2–7.4)

Abbreviations: ECOG, Eastern Cooperative Oncology Group; EGFR, epidermal growth factor

receptor; HER2, human epidermal growth factor receptor 2; NSCLC, non–small cell lung

cancer; SCLC, small cell lung cancer.

a Prior lapatinib therapy (2 patients) is represented in both prior EGFR- and prior HER2-based

categories.




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Table 2. Treatment-emergent adverse events (AEs) in > 5% of patients

AE, n (%) All AEs U3-1287-related AEs

All grades, n

(%)

Grade ≥ 3, n

(%)

All grades, n

(%)

Grade ≥ 3, n

(%)

All AEs 55 (96.5) 28 (49.1) 26 (45.6) 1 (1.8)a

Fatigue 24 (42.1) 0 12 (21.1) 0

Diarrhea 14 (24.6) 0 7 (12.3) 0

Nausea 13 (22.8) 1 (1.8) 6 (10.5) 0

Dyspnea 12 (21.1) 2 (3.5) 0 0

Back pain 10 (17.5) 1 (1.8) 0 0

Decreased appetite 10 (17.5) 0 4 (7.0) 0

Cough 9 (15.8) 0 0 0

Constipation 8 (14.0) 1 (1.8) 2 (3.5) 0

Anemia 7 (12.3) 2 (3.5) 0

Hypokalemia 7 (12.3) 3 (5.3) 1 (1.8) 0

Vomiting 7 (12.3) 0 2 (3.5) 0

Anxiety 6 (10.5) 0 0 0

Alanine aminotransferase

increased

5 (8.8) 0 1 (1.8) 0

Aspartate aminotransferase

increased

5 (8.8) 0 1 (1.8) 0

Blood alkaline phosphatase

increased

5 (8.8) 2 (3.5) 2 (3.5) 0

Dizziness 5 (8.8) 1 (1.8) 0 0

Dysgeusia 5 (8.8) 0 3 (5.3) 0




25

Dyspepsia 5 (8.8) 0 0 0

Edema peripheral 5 (8.8) 0 0 0

Musculoskeletal chest pain 5 (8.8) 1 (1.8) 0 0

Pleural effusion 5 (8.8) 2 (3.5) 0 0

Abdominal pain 4 (7.0) 0 0 0

Activated partial

thromboplastin time

4 (7.0) 2 (3.5) 2 (3.5) 0

Cancer pain 4 (7.0) 1 (1.8) 0 0

Epistaxis 4 (7.0) 0 0 0

Hematuria 4 (7.0) 0 1 (1.8) 0

Hyperhidrosis 4 (7.0) 0 1 (1.8) 0

Hyponatremia 4 (7.0) 2 (3.5) 1 (1.8) 1 (1.8)

Insomnia 4 (7.0) 0 0 0

Musculoskeletal pain 4 (7.0) 2 (3.5) 0 0

Oropharyngeal pain 4 (7.0) 0 0 0

Pruritus 4 (7.0) 0 1 (1.8) 0

Abdominal pain upper 3 (5.3) 0 0 0

Arthralgia 3 (5.3) 1 (1.8) 0 0

Dehydration 3 (5.3) 0 0 0

Depression 3 (5.3) 0 0 0

Dyspnea exertional 3 (5.3) 0 0 0

Headache 3 (5.3) 0 0 0

Hyperglycemia 3 (5.3) 0 0 0

Hypertension 3 (5.3) 0 0 0

Hypomagnesemia 3 (5.3) 0 0 0




26

Lymphopenia 3 (5.3) 1 (1.8) 1 (1.8) 0

Oral candidiasis 3 (5.3) 0 1 (1.8) 0

Pain in extremity 3 (5.3) 0 0 0

Peripheral sensory

neuropathy

3 (5.3) 0 2 (3.5) 0

Pyrexia 3 (5.3) 0 0 0

Rash 3 (5.3) 1 (1.8) 1 (1.8) 0

Stomatitis 3 (5.3) 0 2 (3.5) 0

Urinary tract infection 3 (5.3) 0 0 0

Weight decreased 3 (5.3) 0 0 0

aOne patient experienced a nonserious grade 3 event of hyponatremia and a nonserious grade 3

event of hypophosphatemia.




27

Table 3. PK parameters after IV infusion of U3-1287

Cohort

1

(0.3 mg/kg)

2

(1 mg/kg)

3

(3 mg/kg)

4

(6 mg/kg)

5

(9 mg/kg)

6

(14 mg/kg)

7

(20 mg/kg)

N 3 3 5 4 4 4 3

AUC, µg·day/mL

N 3 3 4 4 4 3a 3

Mean 11.56 59.65 380.36 784.34 1255.89 1433.95d 2512.68

SD 5.64 4.97 148.36 93.14 151.55 692.60 402.8

Median 9.27 62.17 364.43 748.65 1261.74 1534.52 2682.09

tmax, h

N 3 3 5 4 4 4 3

Median 1.08 1.08 4.32 1.13 2.79 1.00 3.83

Range 1.05–6.83 0.92–7.00 1.10–7.00 1.00–4.07 1.08–24.92 1.00–1.02 1.07–6.63

Cmax, µg/mL

N 3 3 5 4 4 4 3

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Mean 6.11 20.90 66.44 162.75 243.50 302.25 422.00

SD 1.30 3.30 15.43 52.22 33.31 37.70 19.00

Median 5.92 22.50 61.90 164.00 251.00 312.50 427.00

Cmin, µg/mL

N 3 2 4 4 4 2b,c 2

Mean 0 0 3.99 8.37 5.14 20.81 36.00

SD 0 0 2.64 5.99 8.60 19.78 3.82

Median 0 0 4.08 9.64 1.32 20.81 36.00

t1/2, d

N NR NR 5 4 4 3c 2e

Mean NR NR 5.51 8.36 7.67 7.95 8.90

SD NR NR 1.62 1.10 3.21 2.91 1.30

Median NR NR 6.52 8.35 7.82 6.74 8.90

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Abbreviations: AUC, area under the serum concentration time curve; Cmax, maximum observed serum concentration; Cmin, minimum observed

serum concentration after the end of infusion; IV, intravenous; NR, not relevant; PK, pharmacokinetic; SD, standard deviation; t1/2, serum

terminal half-life; tmax, time to maximum concentration.

aAUC excluded 1 subject as at least 2 PK samples at terminal phase were excluded or not collected.

bCmin excluded for 1 subject for sampling-related deviations.

cNo data for 1 subject.

dOne patient from cohort 6 had a higher clearance (AUC = 696.559 µg·day/mL) than the median clearance from all dose cohorts receiving 6

mg/kg or more.

et1/2 excluded for 1 subject as R2 was < 0.8.

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FIGURE LEGENDS

Fig 1. U3-1287 pharmacokinetics of 9–20 mg/kg cohorts from part 2. Peak (closed symbols) and trough (open symbols) concentrations at 9

mg/kg (red symbols), 14 mg/kg (orange symbols), and 20 mg/kg (green symbols). Lower horizontal red line is the trough corresponding to

maximal efficacy (IC90) in mice; upper horizontal red line is 10-times this value, the minimal target trough concentration for humans. All 3 doses

achieve trough above the human target; higher doses achieve this in all patients sooner, averaging even higher levels.

Fig 2. SD duration for all subjects with SD per modified RECIST at the earliest observation time point. If a subject discontinued, died, or was

lost to follow-up with no documentation of progressive disease, duration of SD was censored at the date of last tumor assessment.

Fig 3. Computed tomography scan in a patient with non–small cell lung cancer, treated with 20 mg/kg U3-1287. (A) Screening (SCR). (B) Week

18. (C) Changes in sum of longest diameters (SLD) while on treatment with U3-1287.

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Figure 2




Figure 3




Published OnlineFirst April 16, 2013.Clin Cancer Res Patricia M. LoRusso, Pasi A. Janne, Moacyr Ribeiro de Oliveira, et al. Antibody, in Patients With Advanced Solid TumorsPhase I Study of U3-1287, a Fully Human Anti-HER3 Monoclonal

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