V O L U M E 3 1 䡠 N U M B E R 1 䡠 J A N U A R Y 1 2 0 1 3
`
`JOURNAL OF CLINICAL ONCOLOGY
`
`O R I G I N A L R E P O R T
`
`Ranjana H. Advani, Stanford University
`Medical Center, Stanford; Joseph J.
`Buggy, Sara Rodriguez, Betty Y. Chang,
`Juthamas Sukbuntherng, Raquel Izumi,
`Ahmed Hamdy, and Eric Hedrick, Phar-
`macyclics, Sunnyvale, CA; Jeff P. Shar-
`man, US Oncology, Willamette Valley
`Cancer Center, Springfield, OR; Sonali
`M. Smith, University of Chicago,
`Chicago, IL; Thomas E. Boyd, US
`Oncology, Yakima Valley Memorial
`Hospital, Yakima; Kathryn S. Kolibaba,
`US Oncology, Northwest Cancer
`Specialists, Vancouver, WA; Barbara
`Grant, University of Vermont, Burling-
`ton, VT; Richard R. Furman, Weill
`Cornell Medical College, New York, NY;
`and Nathan H. Fowler, MD Anderson
`Cancer Center, Houston, TX.
`
`Published online ahead of print at
`www.jco.org on October 8, 2012.
`
`Supported by Pharmacyclics.
`
`R.H.A. and N.H.F. contributed equally
`to this work.
`
`Authors’ disclosures of potential con-
`flicts of interest and author contribu-
`tions are found at the end of this
`article.
`
`Clinical trial information: NCT00849654.
`
`Corresponding author: Ranjana H.
`Advani, MD, Stanford University Medi-
`cal Center, 875 Blake Wilbur Dr, Suite
`CC-2338, Stanford, CA 94305-5821;
`e-mail: radvani@stanford.edu.
`
`© 2012 by American Society of Clinical
`Oncology
`
`0732-183X/13/3101-88/$20.00
`
`DOI: 10.1200/JCO.2012.42.7906
`
`Bruton Tyrosine Kinase Inhibitor Ibrutinib (PCI-32765)
`Has Significant Activity in Patients With
`Relapsed/Refractory B-Cell Malignancies
`
`Ranjana H. Advani, Joseph J. Buggy, Jeff P. Sharman, Sonali M. Smith, Thomas E. Boyd, Barbara Grant,
`Kathryn S. Kolibaba, Richard R. Furman, Sara Rodriguez, Betty Y. Chang, Juthamas Sukbuntherng,
`Raquel Izumi, Ahmed Hamdy, Eric Hedrick, and Nathan H. Fowler
`See accompanying article on page 128
`
`A
`
`B
`
`S
`
`T
`
`R
`
`A
`
`C
`
`T
`
`Purpose
`Survival and progression of mature B-cell malignancies depend on signals from the B-cell antigen
`receptor, and Bruton tyrosine kinase (BTK) is a critical signaling kinase in this pathway. We
`evaluated ibrutinib (PCI-32765), a small-molecule irreversible inhibitor of BTK, in patients with
`B-cell malignancies.
`Patients and Methods
`Patients with relapsed or refractory B-cell lymphoma and chronic lymphocytic leukemia received
`escalating oral doses of ibrutinib. Two schedules were evaluated: one, 28 days on, 7 days off; and
`two, once-daily continuous dosing. Occupancy of BTK by ibrutinib in peripheral blood was
`monitored using a fluorescent affinity probe. Dose escalation proceeded until either the maximum-
`tolerated dose (MTD) was achieved or, in the absence of MTD, until three dose levels above full
`BTK occupancy by ibrutinib. Response was evaluated every two cycles.
`Results
`Fifty-six patients with a variety of B-cell malignancies were treated over seven cohorts. Most
`adverse events were grade 1 and 2 in severity and self-limited. Dose-limiting events were not
`observed, even with prolonged dosing. Full occupancy of the BTK active site occurred at 2.5 mg/kg
`per day, and dose escalation continued to 12.5 mg/kg per day without reaching MTD. Pharmaco-
`kinetic data indicated rapid absorption and elimination, yet BTK occupancy was maintained for at
`least 24 hours, consistent with the irreversible mechanism. Objective response rate in 50
`evaluable patients was 60%, including complete response of 16%. Median progression-free
`survival in all patients was 13.6 months.
`Conclusion
`Ibrutinib, a novel BTK-targeting inhibitor,
`B-cell histologies.
`
`is well tolerated, with substantial activity across
`
`J Clin Oncol 31:88-94. © 2012 by American Society of Clinical Oncology
`
`INTRODUCTION
`
`Signaling from the B-cell antigen receptor (BCR)
`regulates multiple cellular processes, including pro-
`liferation, differentiation, apoptosis, and cell migra-
`tion, and is essential for normal B-cell development
`and survival.1,2 The BCR pathway is implicated in
`the pathogenesis of several B-cell malignancies, in-
`cluding diffuse large B-cell lymphoma (DLBCL),
`follicular lymphoma, mantle-cell lymphoma, and
`B-cell chronic lymphocytic leukemia (CLL).3-10
`Bruton tyrosine kinase (BTK), a member of the Tec
`kinase family, is a signaling molecule positioned
`early within the BCR signaling cascade, in close
`
`proximity to Syk and phosphoinositide 3-kinase
`delta.11-14 Functional null mutations of BTK in hu-
`mans lead to the inherited disease X-linked agam-
`maglobulinemia (XLA), which is characterized by a
`complete lack of mature peripheral B cells and low
`levels of serum immunoglobulin (Ig).15 Because the
`phenotype of human XLA is largely restricted to B
`lymphocytes, BTK is a uniquely attractive target for
`selective B-cell inhibition.
`Ibrutinib (PCI-32765) is a selective and irre-
`versible small-molecule BTK inhibitor (half maxi-
`mal
`inhibitory concentration, 0.5 nmol/L) that
`inhibits BCR signaling in human B cells via spe-
`cific active-site occupancy.16 In vitro, ibrutinib is
`
`88
`
`© 2012 by American Society of Clinical Oncology
`
`SAN EX 1016, Page 1
`
`

`

`BTK Inhibitor Ibrutinib for B-Cell Malignancies
`
`selectively cytotoxic to DLBCL cell lines driven by chronic active BCR
`signaling.17 Orally administered ibrutinib resulted in objective clinical
`responses in dogs that spontaneously developed non-Hodgkin lym-
`phoma (NHL).16 In this study, an active site–directed affinity probe
`assay was used to demonstrate that efficacy correlated well with the
`degree of active-site occupancy of BTK by ibrutinib.
`Because of the central role of BCR signaling, the restricted
`expression of BTK, and promising preclinical activity with this
`novel agent, we evaluated ibrutinib in a phase I open-label, dose-
`escalation trial to determine the dose, safety profile, pharmacoki-
`netics (PKs), pharmacodynamics, and tumor response in patients
`with relapsed or refractory B-cell NHL and B-cell CLL.
`
`PATIENTS AND METHODS
`
`Eligibility
`Patients with relapsed or refractory, histologically confirmed NHL, CLL, or
`Waldenstro¨m macroglobulinemia (WM) who had failed at least one previous
`therapy were eligible. Inclusion criteria included: Eastern Cooperative Oncology
`Group performance status ⱕ 1, age ⱖ 18 years, measureable disease (NHL: at least
`one lymph node 2 cm in any axis; CLL: ⱖ 5,000 leukemia cells/␮L; WM: IgM
`level ⱖ 1,000 mg/dL with bone marrow infiltration), absolute neutrophil count ⱖ
`1,500/␮L, platelet count ⱖ 75,000/␮L (unless CLL with cytopenia secondary to
`marrow involvement), and adequate renal and hepatic function.
`Major exclusion criteria included: more than four previous systemic
`therapies; previous allogeneic stem-cell transplantation; immunotherapy,
`chemotherapy, radiotherapy, or experimental therapy within 4 weeks of study;
`major surgery within 4 weeks of study; active infection within 4 weeks of cycle
`one, day 1; CNS involvement by lymphoma; history of previous cancer ⬍ 2
`years before study (except skin basal or squamous cell carcinomas, cervical
`cancer in situ, or other in situ carcinomas); and significant comorbidities.
`
`Study Design
`This phase I study was conducted at eight centers in the United States in
`accordance with Good Clinical Practice guidelines, as provided by the Inter-
`national Conference on Harmonisation and principles of the Declaration of
`Helsinki. The institutional review board at each participating site approved the
`study, and all patients provided written informed consent before enrollment.
`Patients received ibrutinib capsules orally once daily at 1.25, 2.5, 5, 8.3, or
`12.5 mg/kg per day on a 28 days on, 7 days off, schedule (35-day cycle), or
`received continuous daily dosing of 8.3 mg/kg or 560 mg until disease progres-
`sion (PD), unacceptable toxicity, or patient or investigator decision to end
`therapy. To better evaluate BTK occupancy, at least six patients were enrolled
`in each cohort. Dose escalation continued until MTD was achieved based on
`protocol-defined dose-limiting toxicities (DLTs), defined as the occurrence in
`cycle one of any of the following: grade ⱖ 3 nonhematologic adverse event
`(AE), grade ⱖ 3 prolongation of the QTc interval, grade ⱖ 3 neutropenia,
`febrile neutropenia, grade 4 thrombocytopenia, or dosing delay because of
`toxicity for more than 7 days. Dose escalation to next level proceeded after
`DLT assessment of patients at the end of cycle one. The MTD was defined
`as the highest dose level at which ⱖ 33% of patients in the cohort experi-
`enced a DLT or, in the absence of a DLT, until three dose levels above the
`dose level in which full BTK occupancy could be demonstrated. Patients
`with complete response (CR), partial response (PR), or stable disease (SD)
`who had received therapy for 6 months were allowed to continue therapy at
`a fixed dose of 560 or 420 mg per day on an extension trial until confirma-
`tion of PD or at physician’s discretion.
`
`Study Assessments
`AEs were monitored throughout treatment, and toxicities were assessed
`by the National Cancer Institute Common Toxicity Criteria for AEs (version
`3.0). Physical examination, blood samples for hematology and clinical chem-
`istry, urinalysis, T/B/natural killer cell counts, and serum Ig were assessed on
`day 1 of each cycle. Disease response assessments included computed tomog-
`
`raphy scans and physical examination. Review of clinical laboratory results
`assessments were conducted every two cycles until PD or use of alternative
`antineoplastic therapy. Computed tomography or positron emission tomog-
`raphy and bone marrow biopsy/aspirate were required to confirm CR. Best
`clinical response (CR, PR, SD, PD) was determined by investigators based on
`criteria defined by the International Working Group revised response criteria
`for malignant lymphoma,18 and the International Workshop on CLL guide-
`lines for diagnosis and treatment of CLL.19 Patients discontinuing therapy for
`reasons other than progression were observed every 2 to 3 months until PD for
`a maximum of 6 months after the last study dose.
`Blood samples for PKs or BTK occupancy were collected during cycle
`one on day 1 (predose and up to 6 hours after dosing), day 2 (predose), day 8
`(predose and up to 4 hours after dosing), and 24 hours after day-28 dosing.
`Plasma was analyzed for ibrutinib concentrations by high-performance liquid
`chromatography with tandem mass spectrometric detection. PK assessments
`were performed on the plasma concentration-time data obtained on day 1
`using noncompartmental analysis (WinNonlin Pro, version 5.3; Pharsight,
`Cambridge, MA). BTK occupancy in peripheral blood mononuclear cells
`(PBMCs) was measured using a fluorescent affinity probe (hereafter probe)
`assay, as described previously.16 Fluorescent probe protein bands were quan-
`tified using Molecular Dynamics ImageQuant 5.2 software (GE Healthcare,
`Waukesha, WI). The relative density of each band was quantified using vol-
`ume integration and local average background correction. The background
`for each quantified band was defined by volume integration of a nearby region
`within the same lane that did not contain a visible band. All background
`regions on the gel were also used to define a lower limit of quantitation equal to
`the average volume of background regions plus 3⫻ the standard deviation of
`the volumes of the background regions. BTK occupancy was compared using
`GraphPad Prism version 4.0 (GraphPad, San Diego, CA). Statistically signifi-
`cant differences were determined using one-way analysis of variance with
`Bonferroni’s post hoc comparison.
`
`Statistical Methods
`This was a dose-escalation trial designed to determine the MTD of
`ibrutinib and characterize the most frequent AEs and DLTs. The intent-to-
`treat (ITT) population included all patients receiving any amount of the study
`drug. The evaluable population included all patients who received at least two
`cycles of therapy. The best response recorded was used for response analyses.
`Overall response rate (CR plus PR) was calculated for the entire study popu-
`lation as well as for each treatment cohort and histology. Progression-free
`survival was measured from the first day of dosing until PD or relapse and
`determined using the Kaplan-Meier method.20
`
`RESULTS
`
`Patient Characteristics
`From March 2009 through September 2010, 56 patients were en-
`rolled and received one or more doses of ibrutinib. Baseline disease char-
`acteristics and previous therapies are listed in Table 1. Median age of the
`patients was 65 years (range, 41 to 82 years). Median number of previous
`therapies was three (range, one to 10), and all but four patients had
`previously received rituximab. Five cohorts were treated with the 28 days
`on, 7 days off, schedule at doses escalating from 1.25 to 12.5 mg/kg
`(cohorts I to V), and two cohorts were treated on the continuous dosing
`schedule at 8.3 mg/kg once daily or a fixed dose of 560 mg once daily
`(Table 2). Median number of cycles received was five.
`
`Safety Profile and Patient Disposition
`The MTD of ibrutinib was not reached. Only two DLTs occurred:
`one grade 3 allergic hypersensitivity (cohort IV) in a patient with a
`history of drug hypersensitivity, and one dose interruption for more
`than 7 days because of transient grade 2 neutropenia (cohort II). Table
`2 summarizes the most frequently (ⱖ 10% of patients) reported AEs
`
`www.jco.org
`
`© 2012 by American Society of Clinical Oncology
`
`89
`
`SAN EX 1016, Page 2
`
`

`

`Advani et al
`
`Table 1. Baseline Patient Characteristics (N ⫽ 56)
`
`Characteristic
`
`No.
`
`Age, years
`Median
`Range
`Sex
`Male
`Female
`Histologic subtype
`Follicular lymphoma
`CLL/SLL
`Mantle-cell lymphoma
`DLBCL
`Marginal zone/mucosal-associated
`lymphoid tissue lymphoma
`Waldenstro¨ m macroglobulinemia
`Prior therapy
`Median No.
`Range
`Rituximab
`Alkylator based
`Anthracycline based
`Radiotherapy
`Autologous stem-cell transplantation
`
`65
`41-82
`
`3
`1-10
`
`38
`18
`
`16
`16
`9
`7
`4
`
`4
`
`52
`47
`25
`15
`3
`
`%
`
`68
`32
`
`29
`29
`16
`13
`7
`
`7
`
`93
`84
`45
`27
`5
`
`Abbreviations: CLL, chronic lymphocytic leukemia; DLBCL, diffuse large
`B-cell lymphoma; SLL, small lymphocytic lymphoma.
`
`by dose cohort. The most common AEs observed in the study were
`typically grade 1 or 2 in severity; grade 3 or 4 events were infrequent
`and independent of dose. Grade 3 to 4 hematologic toxicities included
`neutropenia (12.5%), thrombocytopenia (7.2%), and anemia (7.1%).
`Additionally, no evidence of cumulative hematologic or nonhemato-
`logic toxicity was observed in patients with prolonged dosing. No
`consistent relationship between dose level and AEs was apparent. At
`the time of this writing, 20 patients remain on treatment in an exten-
`sion trial. Thirty-six patients discontinued study treatment: PD
`(n ⫽ 20), patient or physician decision (n ⫽ 8), AEs (n ⫽ 6), and DLTs
`(n ⫽ 2). The latter AEs included pain (grade 4), cerebrovascular
`accident (grade 4), small bowel obstruction (grade 3), flare of chronic
`obstructive pulmonary disease (grade 3), low hemoglobin and throm-
`bocytopenia (grade 2), and hypersensitivity pneumonitis (grade 1).
`
`PKs
`
`Ibrutinib is rapidly absorbed and eliminated after oral adminis-
`tration (Fig 1A). Mean peak plasma concentrations were observed
`between 1 and 2 hours after dosing, and drug exposure (derived from
`area under the concentration-time curve [AUC]) increased in a nearly
`dose-proportional manner (Fig 1B). Plasma concentrations declined
`biphasically, with an initial mean half-life (determined after time to
`maximum plasma concentration to 6 hours postdose) of approxi-
`mately 2 to 3 hours. Mean apparent terminal half-life ranged from 4 to
`8 hours. There was no evidence of accumulation of ibrutinib exposure
`after repeated daily oral dosing.
`
`BTK Occupancy and Pharmacodynamics
`Figures 1C and 1D show representative probe assay data from a
`patient with CLL in dose-level cohort IV (8.3 mg/kg per day). The
`PBMC sample collected from this patient consisted of 95.7% CD20⫹
`
`CLL cells, as determined by flow cytometry. At baseline, the probe
`labeled a robust band corresponding to BTK, and this band decreased
`significantly within 4 hours of treatment and throughout the entire
`treatment cycle, suggesting durable and complete inhibition of BTK.
`Figure 1E shows the dose dependency and durability of BTK occu-
`pancy in PBMCs across all patients dosed in the study. BTK occu-
`pancy ⱖ 95% was achieved 4 hours postdose in all patients in cohort II
`(2.5 mg/kg per day). Figure 1F plots the average BTK active-site occu-
`pancy in PBMCs as a function of ibrutinib exposure (day 1 AUC).
`Complete or nearly complete BTK occupancy was observed in pa-
`tients with AUCs exceeding 160 ng ⫻ h/mL. No decrease was observed
`in the level of serum Ig in patients treated over 12 cycles (Appendix Fig
`A1, online only). A decrease in anti–IgE-stimulated basophil degran-
`ulation was observed, consistent with the role of BTK downstream of
`the high-affinity IgE receptor (Appendix Fig A2, online only).
`
`Tumor Response
`Of 50 patients evaluable for tumor response, 60% achieved an
`objective response (CR or PR), with an overall response rate of 54% in
`the ITT population. Table 3 indicates the best response according to
`dose and schedule. Nine of 56 patients had PD at first assessment, of
`whom three were treated in cohort I, a dose that did not lead to full
`BTK occupancy. Additionally, responses were observed across all his-
`tologies, including seven of nine patients with mantle-cell lymphoma
`(three CRs), 11 of 16 patients with CLL/small lymphocytic lymphoma
`(two CRs), six of 16 patients with follicular lymphoma (three CRs),
`two of seven patients with DLBCL, three of four patients with WM,
`and one of four patients with marginal zone lymphoma (Appendix
`Table A1, online only). Of 11 patients with CLL, all experienced rapid
`reductions in lymphadenopathy during the first cycle of treatment
`accompanied by an increase in absolute lymphocyte count, suggesting
`an egress of malignant cells from lymph nodes into peripheral blood.
`Only one of these patients with CLL did not have an eventual reduc-
`tion in lymphocytosis sufficient to be categorized as PR. Responses
`were durable, with median progression-free survival of 13.6 months at
`the time of data cutoff. Twenty patients remain on study at the time of
`data cutoff because of continued clinical benefit (Fig 2). Change in
`aggregate tumor size (data available for 48 patients) and time on study
`(for all patients) are shown in Figures 2A and 2B, respectively.
`
`DISCUSSION
`
`This study demonstrates that orally administered ibrutinib is well
`tolerated and induces significant objective responses in patients with
`B-cell NHL or CLL who have relapsed or were refractory to standard
`therapy. A majority of AEs were mild (grade 1 or 2) in severity and
`easily managed or reversible. No significant myelosuppressions or
`renal or hepatic toxicities were observed. Additionally, no cumulative
`toxicity was noted with treatment duration over 6 months.
`Thirty patients achieved objective responses, with responses seen
`at each dose level and across all histologies. Responses were durable,
`with a majority maintaining their responses for at least 10 months;
`several patients had remained on study for more than 20 months at the
`time of data cutoff. The highest response rate was observed in patients
`with mantle-cell lymphoma (78%) and CLL/small lymphocytic lym-
`phoma (ITT, 69%; evaluable, 79%). The response rate in mantle-cell
`lymphoma is particularly noteworthy, because the outcome of pa-
`tients with relapsed disease has been modest (32%) with bortezomib,
`
`90
`
`© 2012 by American Society of Clinical Oncology
`
`JOURNAL OF CLINICAL ONCOLOGY
`
`SAN EX 1016, Page 3
`
`

`

`BTK Inhibitor Ibrutinib for B-Cell Malignancies
`
`Table 2. Common Adverse Events (regardless of attribution) According to Dosing Cohorts Reported in ⱖ 10% of Patients
`
`Cohort Characteristic and
`Adverse Event (grade)
`
`I
`
`II
`
`III
`
`Cohort
`
`IV
`
`CD-I
`
`V
`
`7
`1.25 mg/kg/d
`28/7 days
`
`9
`2.5 mg/kg/d
`28/7 days
`
`6
`5.0 mg/kg/d
`28/7 days
`
`8
`8.3 mg/kg/d
`28/7 days
`
`10
`8.3 mg/kg/d
`Once daily
`
`7
`12.5 mg/kg/d
`28/7 days
`
`CD-II
`
`9
`560 mg/d
`Once daily
`
`0
`0
`
`3
`0
`
`1
`0
`
`2
`0
`
`4
`0
`
`1
`0
`
`4
`1
`
`3
`0
`
`0
`0
`
`3
`0
`
`4
`0
`
`1
`0
`
`1
`1
`
`3
`0
`
`2
`0
`
`1
`0
`
`0
`0
`
`1
`0
`
`1
`0
`
`4
`0
`
`4
`1
`
`2
`0
`
`1
`0
`
`3
`0
`
`0
`0
`
`4
`0
`
`7
`0
`
`4
`0
`
`1
`0
`
`5
`2
`
`4
`2
`
`3
`0
`
`2
`0
`
`3
`0
`
`2
`0
`
`1
`0
`
`1
`0
`
`4
`0
`
`0
`0
`
`2
`0
`
`5
`0
`
`4
`0
`
`1
`0
`
`4
`0
`
`2
`0
`
`0
`0
`
`2
`0
`
`% of
`Total
`
`42.9
`3.6
`
`41.1
`1.8
`
`14.3
`0
`
`30.4
`3.6
`
`37.5
`3.6
`
`10.7
`0
`
`25
`0
`
`No. of patients
`Dose
`Scheduleⴱ
`Diarrhea
`1-2
`3-4
`Nausea/vomiting
`1-2
`3-4
`Constipation
`1-2
`3-4
`Decreased appetite/dyspepsia
`1-2
`3-4
`Fatigue
`1-2
`3-4
`Insomnia
`1-2
`3-4
`Headache
`1-2
`3-4
`Muscle spasms/myalgia
`1-2
`3-4
`Other pain
`1-2
`3-4
`Pyrexia
`1-2
`3-4
`Rash
`1-2
`3-4
`Cough
`1-2
`3-4
`Other respiratory
`1-2
`3-4
`Arthralgia
`1-2
`3-4
`Edema
`1-2
`3-4
`
`1
`0
`
`2
`0
`
`8
`0
`
`1
`0
`
`0
`0
`
`3
`0
`
`1
`1
`
`1
`0
`
`5
`0
`
`2
`0
`
`3
`0
`
`1
`0
`
`1
`0
`
`1
`0
`
`0
`0
`
`2
`0
`
`1
`0
`
`2
`0
`
`2
`0
`
`5
`0
`
`2
`0
`
`0
`0
`
`3
`0
`
`3
`1
`
`2
`0
`
`1
`0
`
`3
`0
`
`4
`0
`
`1
`1
`
`3
`0
`
`2
`0
`
`5
`0
`
`0
`0
`
`1
`0
`
`4
`0
`
`6
`1
`
`3
`0
`
`3
`0
`
`3
`0
`
`5
`2
`
`3
`0
`
`4
`0
`
`3
`0
`
`5
`0
`
`2
`0
`
`1
`0
`
`3
`0
`
`4
`0
`
`2
`0
`
`2
`0
`
`4
`0
`
`6
`0
`
`2
`0
`
`1
`0
`
`4
`0
`
`8
`0
`
`0
`0
`
`1
`0
`
`37.5
`0
`
`62.5
`1.8
`
`21.4
`1.8
`
`16.1
`0
`
`32.1
`0
`
`50
`7.1
`
`16.1
`0
`
`28.6
`0
`
`Abbreviation: CD, continuous dosing.
`ⴱ28/7 days ⫽ patients receiving drug for 28 continuous days followed by 7 days off of drug.
`
`currently the only approved agent.21 In patients with CLL, a charac-
`teristic pattern of response included a transient increase in lymphocyte
`count. This pattern has been reported with other agents affecting BCR
`signaling22-23 and reflects disruption of BCR-mediated stromal che-
`motaxis and adhesion, resulting in an egress of tissue-resident malig-
`nant lymphocytes.4,24-26
`
`B-cell malignancies are disorders that depend on an intact BCR
`signaling cascade, of which BTK is a critical mediator.5,13,27,28 BCR
`signaling, either constitutively or following antigen binding, leads to
`the activation of several downstream pathways that connect the BCR
`to proteins involved in cell survival, proliferation, and migration.29
`Most B-cell malignancies continue to express a surface BCR, and it has
`
`www.jco.org
`
`© 2012 by American Society of Clinical Oncology
`
`91
`
`SAN EX 1016, Page 4
`
`

`

`Advani et al
`
`(n = 7)
`
`2,000
`
`1,500
`
`1,000
`
`500
`
`560 mg/day
`
`(n = 18)
`
`(n = 9)
`
`(n = 6)
`
`(n = 9)
`
`(n = 7)
`
`0
`
`2
`
`4
`
`6
`8
`Dose (mg/kg/day)
`
`10
`
`12
`
`14
`
`Mean Ibrutinib AUC0-24h (ng(cid:127)h/mL)
`
`B
`
`D
`
`100
`
`75
`
`50
`
`25
`
`0
`
`Normalized Probe Intensity (%)
`
`(n = 9)
`
`4
`
`8
`
`12
`Time (hours)
`
`16
`
`20
`
`24
`
`Day 28, 24 hr
`
`Day 15, predose
`
`Day 8, 4 hr
`
`Day 8, predose
`
`Day 2, predose
`
`Day 1, 4 hr
`
`Day 1, predose
`
`200
`
`150
`
`100
`
`50
`
`0
`
`A
`
`Mean (SE) Concentration
`
`of Ibrutinib (ng/mL)
`
`C
`
`Probe
`Labeled
`
`Total BTK
`
`Actin
`
`E
`
`LLOD < 3.0%
`
`Day 1
`pre
`
`Day 1
`4 hr
`
`Day 2
`pre
`
`Day 8
`pre
`
`Day 8
`4 hr
`
`Day 15
`pre
`
`Day 28
`24 hr
`
`200
`
`400
`600
`800 1,000 1,200 1,400 1,600
`Ibrutinib AUC0-24h (ng(cid:127)h/mL)
`
`120
`
`100
`
`80
`
`60
`
`40
`
`20
`
`0
`
`F
`
`BTK Occupancy (%)
`
`***
`***
`
`***
`***
`
`***
`***
`
`***
`***
`
`***
`***
`
`***
`***
`
`***
`***
`
`Pre
`4 hr
`24 hr
`Cohort I
`1.25 mg/kg
`(n = 6)
`
`4 hr
`Pre
`24 hr
`Cohort II
`2.5 mg/kg
`(n = 8)
`
`Pre
`4 hr
`24 hr
`Cohort III
`5 mg/kg
`(n = 4)
`
`4 hr
`Pre
`24 hr
`Cohort IV
`8.3 mg/kg
`(n = 6)
`
`Pre
`
`4 hr
`24 hr
`CD-I
`8.3 mg/kg
`(n = 5)
`
`Pre
`4 hr
`24 hr
`Cohort V
`12.5 mg/kg
`(n = 5)
`
`Pre
`
`4 hr
`24 hr
`CD-II
`560 mg
`(n = 3)
`
`100
`
`80
`
`60
`
`40
`
`TK Occupancy (%)
`
`20
`0B
`
`Fig 1. Pharmacokinetic and pharmacodynamic studies of ibrutinib. (A) Mean plasma concentration of ibrutinib over time at the 560-mg per day dose and (B) relationship
`between plasma area under the concentration-time curve (AUC) and dose are shown. Error bars represent SEM; arrow indicates the 560-mg fixed dose, which corresponded
`to a mean dose of 7.22 mg/kg per day (range, 5.6 to 9.3 mg/kg per day) based on actual patient body weight. (C) Representative probe assay data from peripheral blood
`mononuclear cell (PBMC) samples collected from patient with chronic lymphocytic leukemia from dose-level cohort IV (8.3 mg/kg per day). The probe (fluorescently tagged
`derivative of ibrutinib) binds to Bruton tyrosine kinase (BTK; indicated by arrow) with remarkably little specific labeling of other proteins. Total BTK and actin protein levels in
`each sample are shown to normalize protein in each lane. The BTK-bound fluorescent probe is unable to bind BTK in the samples obtained after drug administration because
`of occupancy of the binding site by ibrutinib. (D) Normalized intensity of probe labeling is plotted, and the lower limit of detection (LLOD) for this gel is indicated. (E) Comparison
`of the degree of BTK occupancy by ibrutinib at each dose-level cohort in the study. Dots represent a single BTK occupancy measurement using the probe assay; line indicates
`median percentage occupancy; asterisks denote P ⬍ .001 (analysis of variance). These data suggest that full BTK occupancy was generally achieved in patients at doses ⱖ
`2.5 mg/kg. (F) Pharmacokinetic and pharmacodynamic relationship of BTK active-site occupancy and ibrutinib exposure. Samples of PBMCs were collected predose and at
`4 and 24 hours after administration of ibrutinib for each patient. Data represent the percentage of BTK occupancy before dosing and averaged between 4 and 24 hours
`postdose for each patient in each group. These values are plotted against the drug exposure (AUC0-24) achieved in the patient after administration of ibrutinib on day 1. Line
`represents the line of best fit of a simple maximum-effect model to the data. Analysis of pharmacokinetic and pharmacodynamic profiles on day 1 showed that BTK active-site
`occupancy was saturated or near saturated (⬎ 95%) at AUC values ⱖ 160 ng ⫻ h/mL.
`
`92
`
`© 2012 by American Society of Clinical Oncology
`
`JOURNAL OF CLINICAL ONCOLOGY
`
`SAN EX 1016, Page 5
`
`

`

`BTK Inhibitor Ibrutinib for B-Cell Malignancies
`
`Max % change in tumor burden
`(n = 48)
`
`CLL/SLL
`MCL
`DLBCL
`FL
`Other indolent
`NHL
`
`DLT
`Disease progression
`Off study, patient/
`investigator decision
`Intercurrent illness/
`adverse event
`On study
`
`0
`
`5
`
`10
`15
`20
`Time on Study (months)
`
`25
`
`30
`
`200
`
`150
`
`100
`
`50
`
`0
`
`-50
`
`-100
`
`A
`
`Change From Baseline SPD (%)
`
`B
`
`CLL/SLL
`
`DLBCL
`
`FL
`
`NHLMCL
`
`indolent
`
`Other
`
`Fig 2. Antitumor response in all evaluable patients. (A) Best responses in the 48
`patients evaluated by computed tomography scan for change from baseline in
`the sum of the largest diameter of each target lesion; negative values indicate
`tumor shrinkage. (B) Time on study for all 56 patients grouped by histology; bars
`describe the reason for patient discontinuation. CLL, chronic lymphocytic leuke-
`mia; DLBCL, diffuse large B-cell
`lymphoma; DLT, dose-limiting toxicity; FL,
`follicular lymphoma; NHL, non-Hodgkin lymphoma; MCL, mantle-cell lymphoma;
`SLL, small lymphocytic lymphoma; SPD, sum of product of greatest diameters.
`
`escalation proceeded to three levels above the level where full BTK
`occupancy was observed. Probe binding has been shown to tightly
`correlate with the blocking of BCR signaling and in vivo efficacy.16
`BTK occupancy ⬎ 95% was observed in dose level cohorts II to V (2.5
`to 12.5 mg/kg per day), and each of these cohorts had similar response
`rates, consistent with efficacy deriving from BTK inhibition. Both the
`intermittent and continuous dosing schedules had similar BTK occu-
`pancy and equivalent PKs and toxicity profiles. A fixed continuous
`dose of 560 mg was well tolerated and also led to full-target occupancy
`in a range of individual body weights. Interestingly, in patients with
`CLL, the intermittent dosing schedule was associated with transient
`reversal of treatment-related lymphocytosis during the 7-days-off
`drug period, suggesting a reversal of the biologic effect (Appendix Fig
`A3, online only). On this basis, and given the tolerability of continuous
`dosing, the latter was selected for phase II studies.
`In conclusion, the high level of objective responses observed with
`ibrutinib in patients with refractory B-cell lymphoma and CLL sup-
`ports the hypothesis that BTK is a crucial mediator of growth and
`survival in B-cell malignancies. The data strongly support continued
`clinical evaluation in various B-cell malignancies.
`
`Table 3. Best Clinical Response by Dose-Level Cohort (N ⫽ 56)
`
`Cohort
`
`Dose
`
`No. of
`Patients
`
`CR
`
`PR
`
`1.25 mg/kg/d
`2.5 mg/kg/d
`5.0 mg/kg/d
`8.3 mg/kg/d
`8.3 mg/kg/d
`12.5 mg/kg/d
`560 mg/d
`
`7
`9
`6
`8
`10
`7
`9
`56ⴱ
`
`I
`II
`III
`IV
`CD-I
`V
`CD-II
`Total
`No.
`%
`
`0
`1
`2
`3
`1
`0
`1
`
`8
`14
`
`2
`3
`1
`1
`5
`4
`6
`
`22
`39
`
`Abbreviations: CD, continuous dosing; CR, complete response; PR, par-
`tial response.
`ⴱSix of 56 patients were not evaluable. This includes three patients who
`withdrew consent after 7, 15, and 35 days in the study, respectively; one
`patient with a serious adverse event of failure to thrive after 14 days in the
`study; and two patients with dose-limiting toxicities.
`
`been hypothesized that functional BCR signaling is essential for the
`survival and proliferation of the malignant cell.5 BTK has been shown
`to be an essential component of chronic active BCR signaling, which is
`a key survival pathway in the activated B-cell subtype of DLBCL,
`because genetic knockdown of BTK results in cell death, presumably
`resulting from interruption of survival signals from the BCR to nu-
`clear factor-␬B.17 In CLL, the BCR is activated, with evidence of
`ongoing interaction with antigen in vivo.4 Direct evidence of the
`importance of BCR signaling in CLL comes from gene expression
`profiling data, where BCR signaling has been shown to be the most
`prominent activated pathway in CLL cells isolated from lymph
`nodes.30 The efficacy observed in our study lends further validity to the
`idea that BCR signaling is critical to the growth of B-cell tumors and
`suggests that BTK inhibition alone is sufficient to inhibit this
`growth signal.
`The promising safety profile of ibrutinib is likely related to the re-
`stricted expression of BTK in hematopoietic cells. Clinical features seen in
`patientswithXLAareprimarilyrestrictedtoBcells,suggestingthatBTKis
`particularly critical to B-cell development and function. Indeed, ibrutinib
`has previously been shown to inhibit antigen receptor signaling in B cells
`but not in T cells.16 Interestingly, in contrast to the complete absence of
`circulating Igs observed in patients with XLA, ibrutinib treatment did not
`reduceserumIglevels,eveninpatientstreatedfor12cycles(AppendixFig
`A1, online only). This suggests that daily BTK kinase inhibition is not
`sufficient to replicate XLA, perhaps because the early developmental role
`of BTK at the pro–pre–B-cell stage is different from its signaling role in
`mature B cells. The safety profile of ibrutinib is likely further enhanced by
`the once-daily administration and rapid absorption and elimination of
`the compound. Such intermittent exposure limits the duration of off-
`target effects and is made feasible by the irreversible covalent binding of
`the compound to BTK. Thus, BTK remained fully occupied by ibrutinib
`foratleast24hoursinpatientsincohortsIItoV,despiteitsrapidclearance
`from plasma.
`A unique aspect of this study is the use of a highly specific
`fluorescent affinity probe for BTK measuring active-site occupancy.
`The assay allows for dose escalation based not only on traditional DLT
`measures but also on an optimal biologic dose, where target binding
`could be demonstrated. To better define a margin of safety, dose
`
`www.jco.org
`
`© 2012 by American Society of Clinical Oncology
`
`93
`
`SAN EX 1016, Page 6
`
`

`

`Advani et al
`
`AUTHORS’ DISCLOSURES OF POTENTIAL CONFLICTS
`OF INTEREST
`
`Although all authors completed the disclosure declaration, the following
`author(s) and/or an author’s immediate family member(s) indicated a
`financial or other interest that is relevant to the subject matter under
`consideration in this article. Certain relationships marked with a “U” are
`those for which no compensation was received; those relationships marked
`with a “C” were compensated. For a detailed description of the disclosure
`categories, or for more information about ASCO’s conflict of interest policy,
`please refer to the Author Disclosure Declaration and the Disclosures of
`Potential Conflicts of Interest section in Information for Contributors.
`Employment or Leadership Position: Joseph J. Buggy, Pharmacyclics
`(C); Betty Y. Chang, Pharmacyclics (C); Juthamas Sukbuntherng,
`Pharmacyclics (C); Ahmed Hamdy, Pharmacyclics (C); Eric Hedrick,
`Pharmacyclics (C) Consultant or Advisory Role: Ranjana H.
`Advani, Pharmacyclics (C); Jeff P. Sharman, Gilead (C), Celgene (C),
`Seattle Genetics (C); Richard R. Furman, Pharmacyclics (C); Nathan H.
`Fowler, Pharmacyclics (C) Stock Ownership: Joseph J. Buggy,
`Pharmacyclics; Sara Rodriguez, Pharamacyclics; Betty Y. Chang,
`Pharmacyclics; Juthamas Sukbuntherng, Pharmacyclics; Ahmed Hamdy,
`Pharamcyclics; Eric Hedrick, Pharmacyclics Honoraria: None Research
`Funding: Ranjana H. Advani, Pharmacyclics, Abbott Laboratories,
`
`Seattle Genetics, GlaxoSmithKline, Genentech; Jeff P. Sharman,
`Genentech, Seattle Genetics, Celgene, Gilead, Pharmacyclics; Barbara
`Grant, Pharmacyclics, Millennium Pharmaceuticals, Novartis; Nathan H.
`Fowler, Pharmacyclics, Gilead, Ceph