TRANSPLANTATION
`
`CTLA4 blockade with ipilimumab to treat relapse of malignancy after allogeneic
`hematopoietic cell transplantation
`Asad Bashey,1,2 Bridget Medina,1 Sue Corringham,1 Mildred Pasek,2 Ewa Carrier,1 Linda Vrooman,2 Israel Lowy,3
`Scott R. Solomon,2 Lawrence E. Morris,2 H. Kent Holland,2 James R. Mason,4 Edwin P. Alyea,5 Robert J. Soiffer,5 and
`Edward D. Ball1
`
`1Division of Blood and Marrow Transplantation, University of California, San Diego Moores Cancer Center, La Jolla; 2Blood and Marrow Transplant Group of
`Georgia at Northside Hospital, Atlanta; 3Medarex, Bloomsbury, NJ; 4BMT, Scripps Clinic, La Jolla, CA; and 5Hematologic Malignancies, Dana-Farber Cancer
`Institute, Boston, MA
`
`Relapse of malignancy after allogeneic
`hematopoietic cell transplantation (allo-
`HCT) remains a therapeutic challenge.
`Blockade of the CTLA4 molecule can ef-
`fectively augment antitumor immunity me-
`diated by autologous effector T cells. We
`have assessed the safety and prelimi-
`nary efficacy of a neutralizing, human
`anti-CTLA4 monoclonal antibody, ipili-
`mumab, in stimulating the graft-versus-
`malignancy (GVM) effect after allo-HCT.
`Twenty-nine patients with malignancies
`that were recurrent or progressive after
`allo-HCT, received ipilimumab as a single
`Introduction
`
`infusion at dose cohorts between 0.1
`and 3.0 mg/kg. Dose-limiting toxicity
`was not encountered, and ipilimumab
`did not
`induce graft-versus-host dis-
`ease (GVHD) or graft rejection. Organ-
`specific immune adverse events (IAE)
`were seen in 4 patients (grade 3 arthri-
`tis, grade 2 hyperthyroidism, recurrent
`grade 4 pneumonitis). Three patients
`with lymphoid malignancy developed
`objective disease responses following
`ipilimumab: complete remission (CR) in
`2 patients with Hodgkin disease and
`partial remission (PR) in a patient with
`
`refractory mantle cell lymphoma. At the
`3.0 mg/kg dose, active serum concentra-
`tions of ipilimumab were maintained for
`more than 30 days after a single infu-
`sion.
`Ipilimumab, as administered in
`this clinical trial, does not induce or
`exacerbate clinical GVHD, but may cause
`organ-specific IAE and regression of
`malignancy. This study is registered at
`http://clinicaltrials.gov under NCI proto-
`col
`ID P6082.
`(Blood.
`2009;113:
`1581-1588)
`
`Adoptive immunotherapy in the form of allogeneic hematopoietic
`cell
`transplantation (allo-HCT) can cure several hematologic
`malignancies. However, relapse or progression of malignancy
`(RM) is an important cause of treatment failure and mortality after
`allo-HCT.1,2 RM may be a particularly challenging problem in
`patients with advanced malignancies who underwent transplanta-
`tion and in patients who underwent transplantation using reduced-
`intensity conditioning (RIC) regimens.2 Inadequate costimulation
`of T cells may be one mechanism underlying failure of adoptive
`immunotherapy after allo-HCT. Expression of CTLA4 is induced
`on T cells upon activation. It competes with costimulatory receptor
`CD28 for the B7 ligands CD80 and CD86 on antigen-presenting
`cells. Through this and other mechanisms, CTLA4 functions as an
`important negative regulator of the duration and intensity of
`antigen-specific T-cell responses.3,4 CTLA4 is an important media-
`tor of peripheral self-tolerance and tolerance to tumor antigens.
`Mice genetically devoid of CTLA4 develop fatal lymphoprolifera-
`tion and autoimmunity.5 Antibody-mediated blockade of CTLA4 in
`murine models can result
`in tumor regression and seems to
`augment the efficacy of antitumor vaccines.6,7
`Ipilimumab is a fully human immunoglobulin G1 (IgG1)
`monoclonal antibody that antagonizes CTLA4 (Medarex, Blooms-
`bury, NJ, and Bristol-Myers Squibb, Wallingford, CT). Human
`clinical trials of this antibody in several solid tumors, especially in
`advanced melanoma have demonstrated regression of malignancy
`
`that can be durable.8-20 These responses often occur in conjunction
`with organ-specific autoimmune phenomena (immune adverse
`events [IAE]). Tumor regressions seen can be very delayed and
`may even be preceded by initial disease progression, emphasizing
`the immune mechanism underlying the responses seen.
`T cell–replete allo-HCT relies predominantly upon antigen-
`specific T-cell responses to generate a graft-versus-malignancy
`(GVM) effect. CTLA4 blockade in this context could potentially
`augment the GVM effect and reverse or prevent RM. Further-
`more, the existence of differences in histocompatibility antigens
`between donor and recipient may result in greater efficacy for
`this strategy than in the autologous setting. However, immune
`complications unique to allo-HCT (eg, graft-versus-host disease
`[GVHD] and graft rejection) may potentially also be stimulated.
`In a murine model of major histocompatibility complex (MHC)
`disparate allogeneic transplantation, the use of an antagonistic
`anti-CTLA4 antibody early in the course of the transplantation
`led to increased GVHD or graft rejection depending upon the
`intensity of conditioning. However, the delayed administration
`of the same antibody produced only limited GVHD, while
`resulting in a powerful enhancement of
`the graft-versus-
`leukemia effect against host-derived acute myeloid leukemia
`(AML) cells.21
`To assess the efficacy of ipilimumab as a means of augmenting
`GVM reactions, it is first important to establish a safe dose of the
`
`Submitted July 18, 2008; accepted October 11, 2008. Prepublished online as Blood
`First Edition paper, October 30, 2008; DOI 10.1182/blood-2008-07-168468.
`
`payment. Therefore, and solely to indicate this fact, this article is hereby
`marked ‘‘advertisement’’ in accordance with 18 USC section 1734.
`
`The publication costs of this article were defrayed in part by page charge
`
`© 2009 by The American Society of Hematology
`
`BLOOD, 12 FEBRUARY 2009 䡠 VOLUME 113, NUMBER 7
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`et al
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`BLOOD, 12FEBRUARY2009-VOLUME113, NUMBER7
`
`antibody in the setting of allo-HCT. Here we report the results of a
`
`dose-escalation trial designed to assess the safety and preliminary
`Characteristic
`
`efficacy of ipilimumab in patients with RM after allo-HCT.
`
`
`
`
`
`Table 1. Patient characteristics
`
`Value
`
`43 (21-65)
`23/6 (79121)
`
`14(48)
`6 (21)
`2(6)
`2(6)
`2(6)
`1 (3)
`1 (3)
`1 (3)
`
`19(65)
`10(35)
`
`6 (21)
`23(79)
`
`Methods
`
`Eligibility criteria
`
`
`
`Study design and treatment plan
`
`
`
`Preparative regimen, n (%)
`
`Statistical considerations
`
`Patient characteristics
`
`Median age, y (range)
`Sex (M/F), n (%)
`Diagnosis, n (%)
`Hodgkin disease
`Myeloma
`AML
`CML
`All patients were older than 14 years of age and bad previously
`Cll
`
`undergone allo-HCT from a matched sibling or matched unrelated donor
`NHL
`
`
`for a malignant disease. Patients were eligible if they demonstrated RM
`
`Breast cancer
`
`more than 90 days after their last infusion of allogeneic cells (allo-HCT
`Renal cell cancer
`
`or donor lymphocyte infusion [DLI]) and less than 3 years after
`Donor,n (%)
`HlA-identical
`
`withdrawal of all propbylactic immunosuppression. Disease-specific
`
`criteria for RM were used. Patients were required to bave measurable or
`Matched unrelated
`evaluable disease, except patients wilb acute leukemia or aggressive
`
`non-Hodgkin lymphoma (NHL) wbo could be induced into a complete
`Myeloablative
`remission (CR) with conventional therapy before study entry. Patients
`Reduced intensity
`were required to have greater than 50% donor T-cell chimerism at tbe
`
`
`
`time of study entry and have no ongoing clinically significant GVHD.
`through 6 months and every 3 months through 12 months. Clinical response
`
`
`
`They were required to be off al I immunosuppressive medications for the
`
`evaluations were performed at baseline and I, 2, 3, 6, 9, and 12 months after
`
`treatment or prophylaxis of GVHD for more than 6 weeks before study
`infusion.
`entry (later amended to> 4 weeks) and have no prior history of severe
`Pharmacokinetics
`
`
`(grade 3 or 4) acute GVHD. Other eligibility criteria included absolute
`
`
`lymphocyte count greater than 250/mm3, Eastern Cooperative Oncology
`Blood samples were drawn immediately before tbe dose and at set time
`
`Group (ECOG) PS 0-2, life expectancy greater than 3 months, satisfac­
`
`
`points thereafter. Plasma concentrations of ipilimumab were determined
`
`tory vital organ function unless demonstrated to be secondary to
`
`by Medarex using a quantitative enzyme-linked inlmunosorbent assay
`
`
`malignancy (creatinine < 2.0 mg/dL, bilirubin < 2.0 mg/dL, aspartate
`(ELISA).
`
`transaminase [AST)/alanine transaminase [ALT] < 3X upper lintit of
`
`normal). Patients with serious active infections, HIV , any condition
`
`
`
`requiring inimunosuppressive therapy, any autoin1mune or second
`
`
`malignant condition within the last 5 years, and pregnant females were This trial was designed as a phase 1 dose escalation to determine the MTD
`excluded.
`
`of ipilimumab administered as a single dose to patients who had previously
`undergone allo-HCT. A total of 15 patients were also planned to accrue at
`
`either the MTD or at 3 .0 mg/kg if MTD was not a lower dose. The incidence
`of grade DLT after ipilirnumab infusion was the primary end point
`This trial (CTEP 6082) was an open-label dose-escalation study conducted
`
`
`analyzed. If no DLT was observed in the 15 patients treated at this dose
`at 4 centers. The study was approved by the institutional review boards of
`
`
`level, the possibility that the underlying rate of DLT was greater than 20%
`
`each participating center, and all patients were treated under written
`could be excluded with greater than 95% confidence.
`informed consent in accordance with the Declaration of Helsinki. Ipili­
`mumab was administered in a single dose over 90 minutes. Jpilimumab was
`
`supplied by Cancer Therapy Evaluation Progran1 (CTEP), National Cancer
`Results
`Institute (NCI; Bethesda, MD). A modified Fibonacci dose-escalation
`
`
`design was used. Ipilimumab dose was escalated using the following
`
`planned cohorts: 0.1, 0.33, 0.66, 1.0, and 3.0 mg/kg. At least 3 patients were
`A total of 29 patients treated were accrued between December 2003
`
`
`
`enrolled per dose cohort with additional patients enrolled in the case of
`
`dose-limiting toxicity (DLT) or to substitute for any patients within the
`
`and June 2007. Numbers of patients treated at each dose level were
`as follows: 4 patients at 0.1 mg/kg, 3 patients at 0.33 mg/kg,
`cohort who were removed from study within 8 weeks after dosing. An
`
`additional 12 patients were planned to enroll at the maximum tolerated dose
`
`
`4 patients at 0.66 mg/kg, 3 patients at 1.0 mg/kg, and 15 patients at
`(MID) or the maxinlum
`
`planned dose in the study (3.0 mg/kg) if MID was
`
`3.0 mg/kg. Their demographic information is shown in Table 1.
`
`not reached, to provide a total of 15 patients to further define toxicity and
`Hodgkin disease (HD) was the most common underlying malig­
`
`describe preliminary efficacy at this dose level. DLT was defined as the
`nancy. No patients had ex vivo T-cell depletion during allo-HCT.
`
`development of grade 3 or 4 acute GVHD, graft rejection, the development
`
`Eight patients had received antithymocyte globulin as part of their
`of any unexpected grade greater than 3 or 4 toxicity felt to be related to
`
`
`transplant preparative regimen. Median donor T �ell chimerism on
`
`ipilirnumab, or the development of greater than grade 3 dysfunction of a
`the day of ipilimumab infusion was 100% (range, 76%-100%).
`vital organ felt to be secondary to an JAE . All patients in cohorts below
`Eight patients had failed prior DLI. Median time between the
`
`3.0 mg/kg were observed for 60 days before enrolling patients at the next
`dose level. The protocol was modified to allow repeat dosing at the same
`
`patient's last allogeneic cell infusion and the treatment with
`
`ipilimumab was 366 days (range, 125-2368 days). Twenty-eight
`
`dose level for patients who demonstrated an objective response to the first
`
`dose and then showed evidence of disease progression. U there was no
`
`patients received a single infusion, and l patient received 2 infu­
`
`evidence of disease response and no immunologic adverse effect at 60 days
`
`sions (initial treatment followed by retreatment at disease
`
`
`after the i nitial ipilimumab infusion, donor leukocyte infusions (DU) could
`progression).
`
`be administered. Planned dosing for DLI (CD3+ cells X 106/kg) was 0.5,
`Toxicity
`
`or clinically 1.0, and 5.0 at 60-day intervals, as long as no disease response
`
`significant GVHD occurred. Patients were evaluated for GVHD and other
`The adverse events experienced by the patients treated at each dose
`
`
`
`toxicity by clinical assessment and laboratory testing at baseline and at I, 2,
`cohort are shown in Table 2. DLT as defined was not encountered,
`
`4, 6, 8, 10, and 12 weeks after ipilimumab infusion and then montbly
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`IPILIMUMAB FOR RELAPSE AFTER ALLOTRANSPLANTATION
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`Table 2. Adverse events by grade and dose level
`
`Toxicity grade
`
`Dose level, mg/kg
`
`1
`
`2
`
`3
`
`4
`
`Arthritis*, pneumonitis
`
`Anemia, thrombocytopenia, pneumonia,
`neutropenia/fever
`
`Infection, hip fracture
`
`Anemia
`
`Elevated AST/ALT
`
`Neutropenia (transient)*
`
`Leucocytosis, fever, neutropenic fever,
`dyspnea, mucositis
`
`Pneumonitis*
`
`0.1
`
`0.33
`
`0.66
`
`1.0
`
`3.0
`
`Leucocytosis, diarrhea, shoulder pain,
`bronchitis (2), vaginosis
`Blurring of vision, abdominal
`pain/constipation, hypercalcemia,
`hyperglycemia, knee swelling
`Hyperthyroidism*, cellulitis, bone pain,
`cough, pneumonia (2)
`Hypotension, urinary retention
`
`Fatigue (2), Fever (2 ⫹ 1)*, sweats*,
`insomnia, pruritis*,
`rash/desquamation*, abdominal
`pain, backache*, arthritis*,
`headache, sensory neuropathy,
`cough, dyspnea, pneumonia,
`anxiety
`
`Pharyngitis, eyelid blisters, tachycardia,
`dizziness, headache
`Palpitations, chest pain, diarrhea (2),
`nausea, cough
`
`Hypothyroidism, elevated AST,
`hyperglycemia, acute GVHD (skin)
`Anemia, thrombocytopenia, elevated
`ALT/AST, elevated alkaline
`phosphatase
`Chills, fatigue (2), fever (2)*, night
`sweats, anemia, thrombocytopenia,
`petichiae, skin dryness, rash,
`hypercalcemia, hypocalcemia,
`hypokalemia, hypernatremia,
`hyponatremia, muscle cramps*,
`dizziness (2)*, headache, insomnia,
`photophobia, colitis*, diarrhea*,
`elevated alk. phos., elevated
`AST/ALT*, nausea (2), vomiting*,
`increased creatinine, vaginosis,
`pharyngitis*, agitation
`
`*Events that the investigator felt were at least possibly related to ipilimumab.
`
`and an MTD was not reached with a single dose up to 3.0 mg/kg
`(one patient who developed a ⬎grade 3 IAE did so after retreat-
`ment with ipilimumab). Although multiple grade 1 and 2 toxicities
`were recorded, in almost all cases no clear relationship to the study
`agent was evident. Thus, 15 patients in all were treated at the
`originally planned highest dose (3.0 mg/kg).
`
`GVHD
`
`No patients developed grade 3 or 4 acute GVHD after ipilimumab
`alone. Three patients developed minor ocular dryness and erythema
`at 2, 6, and 8 months from a single ipilimumab infusion without
`subsequent DLI. They did not require systemic therapy. Two
`patients with preexisting minor active chronic GVHD not requiring
`immunosuppressive therapy at baseline (1 oral, 1 ocular) showed
`no exacerbation of symptoms after ipilimumab infusion. One
`patient developed no GVHD after ipilimumab, but developed grade
`1 skin GVHD after DLI given at 2 months after ipilimumab for
`progressive disease.
`
`Organ-specific IAE
`
`Four patients developed IAE distinct from GVHD that were
`potentially attributable to ipilimumab.
`Patient 0102 (age 52, Hispanic female, AML, dose level
`0.1 mg/kg) developed grade 3 polyarthropathy with nodules clini-
`cally consistent with rheumatoid arthritis 3 months after a single
`infusion of ipilimumab. The episode occurred approximately
`4 weeks after DLI given for RM (3 months after ipilimumab);
`therefore, the role of ipilimumab versus DLI in the etiology of this
`episode is difficult
`to distinguish. The patient responded to
`corticosteroid therapy with a complete regression of her symptoms.
`Pre-ipilimumab serum was retrospectively analyzed and found to
`be positive for rheumatoid factor at a titer of 1:640. The patient had
`no prior history of rheumatoid arthritis.
`
`Patient 0311 (age 48, white male, chronic lymphocytic leuke-
`mia [CLL], dose level 0.66 mg/kg) developed laboratory evidence
`of hyperthyroidism associated with the production of thyroid-
`stimulating hormone (TSH) receptor stimulating antibody within
`4 weeks of a single ipilimumab infusion. The patient was referred
`to endocrinology and was monitored without therapy for the next
`month. He demonstrated laboratory evidence of progressive hyper-
`thyroidism associated with rising titers of anti-TSH receptor
`antibodies at 2 months after infusion. The patient was then treated
`with methimazole, which resulted in improvement of his serum-
`free T4 and T3 levels by 4 months after ipilimumab infusion. He
`never developed clinical symptoms of hyperthyroidism. Assess-
`ment of baseline thyroid function on blood drawn immediately
`before ipilimumab infusion revealed normal T4, TSH, and
`a borderline level of TSH-receptor receptor antibody.
`Patient 2521 (white male, age 45, HD, dose level 3.0 mg/kg)
`complained of dyspnea on exertion 10 weeks after a single dose of
`ipilimumab. Computed tomography (CT) scan showed no new
`abnormalities, but pulmonary function resting revealed an obstruc-
`tive defect that responded to inhaled corticosteroids. No infectious
`etiology was identified.
`Patient 3520 (white male, age 35, HD, dose level 3.0) had
`demonstrated clinical and radiologic regression of malignancy
`followed later by disease progression after his first infusion of
`3.0 mg/kg ipilimumab. He was retreated with the same dose of
`ipilimumab 4 months after his first infusion. He was noted to have
`new bilateral ground glass opacification in bilateral upper lung
`fields on a routine reassessment CT scan at 4 weeks after the second
`infusion. Bronchoscopy revealed no infective etiology except
`␤-hemolytic Streptococcus from a single culture and transbronchial
`biopsy showed inflammatory changes. The infiltrates worsened
`despite antimicrobial therapy. He was commenced on methylpred-
`nisolone with marked radiologic improvement at 2- and 4-week
`reassessments (Figure 1). Complete tapering of the patient’s
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`Table 3. Objective disease responses
`Patient
`(dose level, mg/kg)
`
`Age
`
`Sex
`
`0414 (1.0)
`2517 (3.0)
`3520 (3.0)
`
`64
`21
`40
`
`M
`M
`M
`
`Diagnosis
`
`NHL (mantle cell)
`HD
`HD
`
`Prior
`DLI
`
`Yes (⫻2)
`Yes
`No
`
`Response to
`ipilimumab
`
`GVHD after
`ipilimumab
`
`PR
`CR
`CR*
`
`No
`No
`No
`
`Other toxicity
`
`Transient neutropenia
`No
`Grade 4 pneumonitis*
`
`*Negative effect observed after retreatment with ipilimumab.
`
`corticosteroid therapy over the next month was associated with
`significant exacerbation of pulmonary infiltrates and dyspnea
`leading to intubation while radiologic evidence of his HD resolved
`completely. Repeat transbronchial biopsy showed acute and chronic
`inflammatory changes only. Reinstitution of corticosteroids accom-
`panied by infliximab (single dose 10 mg/kg) resulted in rapid
`improvement and eventual complete resolution of dyspnea and
`pulmonary infiltrates. However, despite a much slower taper,
`discontinuation of corticosteroid therapy was associated with
`recurrence of grade 4 pneumonitis. The patient responded com-
`pletely to treatment with methylprednisone accompanied with a
`4-week course of infliximab (10 mg/kg per week) and mycopheny-
`late mofetil. Slow tapering of corticosteroid therapy followed by
`maintenance therapy with low-dose methylprednisolone and myco-
`phenylate mofetil has prevented subsequent recurrence of the
`patient’s pneumonitis.
`
`Regression of malignancy
`
`Three patients demonstrated objective disease responses after
`ipilimumab alone (summarized in Table 3).
`Patient 0414 had failed prior therapy for multiply relapsed
`mantle cell NHL before undergoing matched unrelated donor
`allo-HCT. Upon RM after allo-HCT, he received 2 DLI without
`evidence of disease response. He had rapidly growing left parotid
`and right axillary masses before enrollment on study. Administra-
`tion of ipilimumab was followed approximately 4 weeks later with
`a febrile illness that was associated with significant clinical and
`radiologic regression of his lymphoma resulting in a partial
`
`remission (PR) that was persistent at 2 months after ipilimumab
`(Figure 2). At 3 months after ipilimumab, the responses in the
`parotid and axillary masses were maintained, but
`the patient
`developed a new positron emission tomography (PET)–avid lesion
`within the abdomen. The patient was then taken off the study to
`pursue alternative therapeutic options.
`Patient 2517 had failed a prior autologous transplantation for
`primary refractory HD before undergoing a matched related donor
`allo-HCT. His disease relapsed within 6 months of the transplanta-
`tion. He was treated with gemcitabine monotherapy followed by
`DLI. However, there was evidence of disease progression within
`2 months of DLI. The patient had evidence of PET-avid right hilar
`adenopathy immediately before receiving ipilimumab at 3.0 mg/kg.
`CR was achieved on the 1-month reassessment after ipilimumab
`(Figure 3). The CR has been durable for 37 months at the time of
`this report.
`Patient 3520 had a history of relapsed HD and had previously
`failed autologous transplantation. Matched related donor allo-HCT
`did not achieve CR, and there was frank malignant progression
`6 months after transplantation. The patient was treated with
`ipilimumab at the 3.0 mg/kg dose and developed partial regression
`of PET-avid disease at 1- and 2-month evaluations following
`ipilimumab. However, disease progression was evident at
`the
`3-month evaluation following ipilimumab, and he was retreated
`with 3.0 mg/kg ipilimumab approximately 4 months after the first
`infusion. The second infusion was associated with a corticosteroid-
`responsive noninfectious pneumonitis, which progressed to grade 4
`severity when the corticosteroids were tapered and discontinued
`
`Figure 1. Pneumonitis after retreatment with ipilimumab. CT scans of the chest from patient 3520 (dose level 3.0 mg/kg). Scans show (A) an extensive inflammatory
`infiltrate that developed approximately 6 weeks after retreatment with ipilimumab and (B) complete resolution of changes after corticosteroid therapy.
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`IPILIMUMAB FOR RELAPSE AFTER ALLOTRANSPLANTATION
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`Figure 2. Regression of malignancy in a patient with
`mantle cell lymphoma. CT scans from patient 0414 (dose
`level 1.0 mg/kg) showing left parotid (A,B), and right axillary
`(C,D) nodal masses before (A,C) and 1 month after (B,D)
`ipilimumab infusion.
`
`(see section on IAE above). However, by 3 months after the second
`infusion, the patient achieved a CR that was durable for 9 months
`thereafter.
`Two additional patients with HD treated at the highest dose
`level (3.0 mg/kg) who had evidence of rapid disease progression
`before ipilimumab achieved disease stabilization for 3 and 6 months,
`respectively, after the infusion.
`
`DLI
`
`Nine patients received at least one DLI in the study after showing
`persistence or progression of malignancy after ipilimumab (first
`DLI, 0.5 ⫻ 107 CD3⫹ cells/kg; 2 at dose ipilimumab cohort
`0.1 mg/kg, 2 at 0.66 mg/kg, 2 at 1.0 mg/kg, and 3 at 3.0 mg/kg).
`The first DLI was administered at a median of 2 months after
`ipilimumab (range, 2-4 months). Three patients also received a
`second DLI (1.0 ⫻ 107 CD3⫹ cells/kg) at a median of 4 months
`(range, 4-9 months) after ipilimumab. No patient who received DLI
`after failing ipilimumab demonstrated an objective disease response.
`
`Survival
`
`A Kaplan-Meier plot of estimated overall survival of all 29 patients
`treated in the study is shown in Figure 4. Median overall survival
`from the time of ipilimumab therapy was 24.7 months.
`
`Pharmacokinetics
`
`The concentration of ipilimumab at various time points after single
`infusion at the dose levels assessed is shown in Figure 5. All doses
`used achieved a peak concentration of ipilimumab greater than
`1 ␮g/mL. At the highest dose studied (3.0 mg/kg), ipilimumab
`levels remained at concentrations above 10 ␮g/mL for at least
`30 days and above 1 ␮g/mL for 60 days.
`
`Discussion
`
`This report documents the results of the first clinical trial to use
`CTLA4 blockade as a means of augmenting the GVM effect after
`allo-HCT. We show that a single infusion of ipilimumab at doses up
`to 3 mg/kg can be administered safely to patients who have RM
`after allo-HCT. In particular, ipilimumab did not result in stimula-
`tion or exacerbation of acute or chronic GVHD in these patients.
`No patient developed typical clinical features of acute or chronic
`GVHD after ipilimumab alone. The eligibility criteria of the trial
`may have limited the risk of severe GVHD. Specifically, patients
`were required to have not experienced prior grade 3 or 4 acute
`GVHD and were required to have tolerated discontinuation of all
`immunosuppressive medications for a minimum of 4 to 6 weeks
`before study entry. It is unclear whether ipilimumab would also not
`induce or exacerbate GVHD in patients who had experienced prior
`severe acute GVHD or those patients who were still on immunosup-
`pressive therapy at the time of treatment. It is notable, however, that
`several patients treated in this study had experienced some prior
`acute and/or chronic GVHD before ipilimumab therapy, and all
`patients had at least 50% donor T-cell chimerism at the time of
`ipilimumab infusion (median, 100%). The lack of GVHD as a
`complication of ipilimumab therapy in this trial cannot be ex-
`plained by subtherapeutic dosing. Ipilimumab is a fully human
`monoclonal antibody and has a relatively prolonged half-life in
`vivo.8,11,15 Serial estimation of serum ipilimumab concentrations in
`our patients demonstrated that at doses greater than 1.0 mg/kg,
`serum ipilimumab levels remained above 10 ␮g/mL for several
`days (more than 30 days after a dose of 3.0 mg/kg). Small et al
`observed similar levels of ipilimumab were seen after a single dose
`of ipilimumab at 3.0 mg/kg.15 Serum ipilimumab levels greater
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`Figure 3. Regression of malignancy in a patient with HD. CT scans (A,B) and PET scans (C,D) from patient 2517 (dose level 3.0 mg/kg) showing right hilar adenopathy
`before (A,C) and 2 months after (B,D) ipilimumab infusion.
`
`than 0.1 ␮g/mL have been shown to saturate binding sites on
`recombinant CTLA4 in ELISA studies, and levels greater than
`2 ␮g/mL achieve binding saturation for CTLA4 expressed through
`transfection on a T-cell hybridoma.22 Maximal inhibition of the
`binding of CTLA4 expressed upon these cells to CD80 and CD86
`can be achieved by concentrations of ipilimumab as low as 6 and
`1 ␮g/mL, respectively.22 CTLA4 molecules are heavily overex-
`pressed on such transduced cell lines compared with that seen on
`T cells after activation in vivo. Thus it is likely that ipilimumab
`levels achieved in our patients at the higher dose cohorts would
`induce complete blockade of the CTLA4 expressed on their T cells
`in vivo after antigen-induced activation. Furthermore, clinical
`effects other than GVHD, namely clinical regression of malignancy
`and organ-specific IAEs were induced at these dose levels in our
`trial. It is possible that ipilimumab did not initiate or exacerbate
`GVHD in our study because of the required separation between the
`last infusion of donor cells and ipilimumab administration (mini-
`mum 90 days, median 366 days). The etiology of the clinical
`
`syndrome of GVHD is complex.23 Available data suggest that the
`presence of both recipient-derived antigen-presenting cells and
`possibly cytokine release associated with regimen-related toxicity
`may be components that participate in the generation of clinical
`acute GVHD.23 The lack of one or both of these components due to
`the relatively prolonged time between last donor-cell infusion and
`ipilimumab administration may have contributed to the lack of
`clinical acute GVHD seen after ipilimumab despite the other
`immune effects observed. Delayed administration of anti-CTLA4
`antibody was associated with augmentation of the GVM effect
`without exacerbation of lethal GVHD in a murine model of
`MHC-mismatched allo-HCT.21 In a recent study of a murine model
`of minor histocompatibility antigen-mismatched allo-HCT,24 early
`CTLA4 blockade induced acute GVHD. However, delayed CTLA4
`blockade did not result in GVHD, but resulted instead in potentially
`lethal host-derived autoimmune effects, as well as significant
`augmentation of resistance to challenge with syngeneic leukemia
`cells. Both autoimmune effects and antileukemia activity were
`mediated by host-derived T cells in this model. However, these
`effects were dependent upon the coexistence of donor-derived
`T cells, as neither effect was seen after syngeneic hematopoietic
`transplantation. These findings seen in experimental animal models
`of allo-HCT are consistent with the observations in our clinical
`
`Figure 4. Kaplan-Meier plot of overall survival from the time of ipilimumab
`therapy for all patients (n ⴝ 29).
`
`Figure 5. Serum ipilimumab levels after a single infusion of doses from 0.1 to
`3.0 mg/kg.
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`trial. However, it is unlikely that the organ-specific IAE or the
`objective responses seen in patients treated on our study were
`mediated exclusively by host-derived T cells. All patients demon-
`strating these effects had greater than 80% donor T-cell chimerism
`on the date of ipilimumab therapy, and in only 2 patients were any
`host-derived T cells detectable. Furthermore, only one of the
`patients demonstrating IAEs or objective responses had any
`increase in host-derived chimerism on serial assessment after
`ipilimumab upon development of the immune effect (patient 0102).
`These findings would argue against the possibility that the immune
`phenomena observed in our trial were effected solely by host-
`derived T cells, but
`the possibility cannot be excluded with
`certainty.
`Organ-specific IAEs were seen in 4 of 29 (14%) patients treated
`in our study. Such IAEs have been described in trials of use of
`ipilimumab and another anti-CTLA4 antibody in patients with
`cancer who had not undergone allo-HCT.8-17,19,20 As in those
`reports, the IAEs seen in our study were highly responsive to
`immunosuppressive therapy, although prolonged therapy and mul-
`tiple immunosuppressive agents were required in one patient. IAEs
`have been found to be more common in trials using repeated dosing
`of ipilimumab, and their occurrence is associated with regression of
`malignancy. Consistent with those findings, the most severe IAE in
`our study occurred in a patient after he was retreated with
`ipilimumab. He also experienced a durable CR in his malignancy
`after the second infusion. The frequency of the IAEs seen in
`patients in our study does not appear to differ significantly from
`other trials in which primarily a single dose of ipilimumab up to
`3 mg/kg has been studied. All patients treated in this study had
`greater than 50% donor T-cell chimerism at the time of ipilimumab
`infusion. Therefore, these data imply that despite the presence of
`disparity in minor histocompatibility antigens between donor and
`recipient, the frequency of and severity of IAE after ipilimumab
`may not be significantly greater in patients after allo-HCT than in
`patients who have not undergone allo-HCT.
`Objective responses were encountered in 3 patients treated on
`our protocol (17% of the 18 patients treated at ⬎1 mg/kg). The
`objective responses seen in our study occurred in patients with
`lymphoid malignancies and included 2 durable CRs in patients
`with HD. This finding may be attributable to chance, as HD was the
`most frequent malignancy treated on our study, and the total
`number of patients with each diagnosis in our study was small.
`
`References
`
`However, objective responses have been reported in patients with
`lymphoma18 in a trial where the antibody was used after failure of
`idiotype vaccination. Further investigation of ipilimumab in pa-
`tients receiving allo-HCT in HD and NHL is warranted. Once the
`safety of ipilimumab after allo-HCT is fully established, its efficacy
`in the prophylaxis of relapse in high-risk patients may be explored.
`Thus,
`in conclusion, our study suggests that
`the use of
`ipilimumab up to 3 mg/kg as administered in our study is safe and
`can produce antitumor responses. It forms a platform for the
`exploration of true efficacy when used after allo-HCT through
`formal phase 2 studies in specific malignancies