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Melanoma and Cutaneous Malignancies

Tremelimumab (CP-675,206), a Cytotoxic T Lymphocyte–Associated Antigen 4 Blocking Monoclonal Antibody in Clinical Development for Patients with Cancer

^aDepartment of Medicine, Division of Hematology/Oncology, ^bDepartment of Surgery, Division of Surgical Oncology, and ^cJonsson Comprehensive Cancer Center, University of California at Los Angeles, Los Angeles, California, USA; Departments of ^dImmunology, ^eClinical PK/PD, ^gDrug Safety R&D, and ^fClinical Oncology, Pfizer Global Research & Development, Groton-New London, Connecticut, USA; ^hUniversity of Rochester School of Medicine and Dentistry, Rochester, New York, USA

Key Words. CTLA-4 • Melanoma • T cell • Antitumor

Correspondence: Jesus Gomez-Navarro, M.D., Pfizer Global Research & Development, Groton-New London, Connecticut 06340, USA. Telephone: 860-732-2079; Fax: 860-732-7127; e-mail: jesus.gomez-navarro{at}pfizer.com

Received December 8, 2006; accepted for publication April 29, 2007.

	Learning Objectives

Top Learning Objectives Abstract Introduction Preclinical Development of... Early Clinical Development of... Testing the Expansion of... Modulation of Treg Cells... Conclusions Disclosure of Potential... Acknowledgments References

 
After completing the course, the reader will be able to:

1. Educate community oncologists about the promise of anti-CTLA-4 monoclonal antibodies for the treatment of advanced cancer.
   
2. Suggest that CTLA-4 blockade overcomes barriers to effective immunotherapy for cancer.
   
3. Describe the rational design and clinical development strategy taken with the CTLA-4 antagonist tremelimumab.
   

	ABSTRACT

Top Learning Objectives Abstract Introduction Preclinical Development of... Early Clinical Development of... Testing the Expansion of... Modulation of Treg Cells... Conclusions Disclosure of Potential... Acknowledgments References

 
Tremelimumab (CP-675,206) is a fully human monoclonal antibody specific for human cytotoxic T lymphocyte–associated antigen 4 (CTLA-4, CD152) in clinical development for patients with cancer. Blocking the CTLA-4 negative costimulatory receptor with the antagonistic antibody tremelimumab results in immune activation. Administration of tremelimumab to patients with locally advanced and metastatic melanoma has resulted in a subset of patients with durable objective tumor regressions. Its IgG₂ isotype minimizes the possibility of cytotoxic effects on activated T lymphocytes and cytokine release syndrome. Preclinical testing in vitro and in large animal models predicted the target concentrations of circulating antibody in humans necessary for a pharmacodynamic effect. Phase I clinical trials provided evidence of dose- or exposure-related effects consistent with the anticipated mechanism of action. Further clinical development has led to two ongoing registration trials in patients with metastatic melanoma: a phase III randomized trial of tremelimumab versus dacarbazine or temozolomide in previously untreated patients with advanced melanoma and a phase II trial of tremelimumab in previously treated patients with advanced melanoma.

Disclosure of potential conflicts of interest is found at the end of this article.

	INTRODUCTION

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Rationale for Cytotoxic T Lymphocyte– Associated Antigen 4 Blockade to Treat Cancer
In 1996, Leach et al. [1] demonstrated that systemic administration of antagonistic antibodies (Abs) to the negative costimulatory receptor cytotoxic T lymphocyte–associated antigen 4 (CTLA-4) induces tumor regressions in mice. Since then, preclinical models have confirmed that CTLA-4 blockade induces antitumor immune responses [2–8]. In mice bearing immunogenic tumors, administration of CTLA-4–blocking Abs alone induced rejection of established tumors [1, 9] and decreased relapses when given as adjuvant immunotherapy in a model of metastatic prostate cancer [3]. However, in poorly immunogenic tumor models, prior immunization with vaccines [2, 4, 5, 10–13] or prior depletion of CD25⁺ regulatory T (Treg) cells [7, 8] was required for CTLA-4 blockade to exert robust antitumor effects. In nonhuman primates, anti–CTLA-4 Abs enhanced T-cell and Ab responses to an infectious disease vaccine and a whole tumor cell vaccine [14]. After this experimental work, it became clear that the prior emphasis on activating immune system cells should be complemented with the modulation of immune system negative regulatory pathways. Other negative immune regulators amenable to pharmacologic modulation have been described, including programmed cell death 1, B and T lymphocyte attenuator, transforming growth factor beta ß, interleukin 10 (IL-10), and vascular endothelial growth factor [15–19]. CTLA-4 appears to be dominant in maintaining peripheral homeostasis to self, confirmed by the phenotype of CTLA-4 gene knockout mice that develop rapidly progressing, lethal, uncontrolled lymphoproliferation and autoimmunity [20, 21].

This laboratory and animal model research has been successfully translated into the clinic. Two fully human monoclonal antibodies (mAbs) with CTLA-4 antagonistic activity are in clinical development; ipilimumab (formerly MDX-010; developed by Medarex, Inc., Bloomsburg, NJ, and codeveloped with Bristol-Myers Squibb, Princeton, NJ) and tremelimumab (formerly CP-675,206; developed by Pfizer Pharmaceuticals, Inc., New York). This antibody was transiently named ticilimumab; the term was discontinued because the World Health Organization considered it too similar to the generic name tocilizumab, a humanized Ab against the IL-6 receptor. Several published studies attest to the biologic and clinical activity of ipilimumab and tremelimumab in patients with melanoma and other cancers [22–32], generating great enthusiasm for continued testing.

Potential Mechanisms of Antitumor Activity of CTLA-4–Blocking Abs
CTLA-4 is an activation-induced, type I transmembrane protein of the Ig superfamily, expressed by T lymphocytes as a covalent homodimer that functions as an inhibitory receptor for the costimulatory molecules B7.1 (CD80) and B7.2 (CD86) [9, 33–36]. Crosslinking of CTLA-4 by B7 in the context of T-cell antigen receptor (TCR) engagement inhibits T-cell activation, IL-2 gene transcription, and T-cell proliferation by directly inhibiting TCR signal transduction [1, 9]. CTLA-4 is also expressed by human monocytes [35], but its function is not clear in this cell type.

It has been hypothesized that CTLA-4 blockade using specific Abs may induce responses by sustaining the activation and proliferation of tumor-specific T cells [9]. Antigenic peptides from tumor debris can be crosspresented by host dendritic cells to activate tumor antigen-specific T cells [37]. However, these T cells are not efficient in preventing tumor growth, in part because of the dominant role of activation-induced CTLA-4 expression, which leads to T-cell anergy or tolerance. Blockade of the B7 costimulatory molecule–CTLA-4 interaction in the activated T cell prevents CTLA-4–mediated negative signaling, allowing for antitumor T-cell activation (Fig. 1) [9]. Consequently, CTLA-4 blockade with mAbs in murine models results in increased IL-2 and interferon-gamma production by lymphocytes, increased expression of major histocompatibility complex (MHC) class I molecules, and markedly increased tumor killing [38, 39].

View larger version (91K): [in this window] [in a new window]   Figure 1. T-cell activation by blockade of negative signaling from cytotoxic T lymphocyte–associated antigen 4 (CTLA-4). Tumor debris released from melanoma lesions can be crosspresented by host dendritic cells to activate tumor antigen-specific T cells. Blockade of the B7 costimulatory molecule–CTLA-4 interaction using tremelimumab (CP-675,206) would prevent CTLA-4–mediated negative signaling, allowing for adequate antitumor T cell activation. Abbreviations: MHC, major histocompatibility complex; TCR, T-cell receptor.

View larger version (73K): [in this window] [in a new window]   Figure 2. Potential mechanisms of antitumor responses mediated by cytotoxic T lymphocyte–associated antigen 4 (CTLA-4)-blocking antibodies (Abs). (A): Anti–CTLA-4 Abs can block the negative signaling derived from the activation-induced CTLA-4 molecule on the surface of activated T cells triggered by B7 costimulatory molecules on dendritic cells (DCs). (B): A subset of T regulatory cells that constitutively express CTLA-4 may provide reverse signaling by binding to B7 molecules on DCs, which can upregulate indoleamine 2,3-dioxygenase and thereby tolerize T cells in the microenvironment. (C): CTLA-4–expressing T cells may also bind directly to activated T cells, because B7 costimulatory molecules are expressed on the surface of activated human T cells. CTLA-4–blocking Abs would interfere with this negative signaling and result in the local expansion of tumor antigen-specific T cells. (D): CTLA-4 can be expressed on the surface of melanoma cells. CTLA-4–blocking Abs may induce direct killing of tumor cells by triggering apoptosis or Ab-dependent cellular cytotoxicity. (E): Tumor-expressed CTLA-4 may trigger increased indoleamine 2,3-dioxygenase in tumor-infiltrating DCs, and CTLA-4–specific monoclonal Abs would also block this effect. Abbreviations: MHC, major histocompatibility complex; TCR, T-cell receptor.

	PRECLINICAL DEVELOPMENT OF TREMELIMUMAB

Top Learning Objectives Abstract Introduction Preclinical Development of... Early Clinical Development of... Testing the Expansion of... Modulation of Treg Cells... Conclusions Disclosure of Potential... Acknowledgments References

 
Goals for the Development of CTLA-4–Blocking Abs
The human CTLA-4 gene was cloned in 1988 [33, 48]. Pfizer's preclinical immunology team focused on CTLA-4 as a potential target before it was clear whether it was a positive or negative costimulatory receptor [49]. Emerging data [1, 34, 50] provided strong evidence that blockade of CTLA-4 signaling enhanced T-cell activation in vitro and markedly enhanced antitumor responses in murine models. It was hypothesized that an enhanced T-cell immune response may result in tumor regression, leading to a focus on CTLA-4 as a potential drug target for cancer. Based on this rationale, a panel of CTLA-4–blocking Abs was developed. It was essential that the CTLA-4–blocking Abs not kill activated T cells by fixing complement or triggering Fc receptor–mediated Ab-dependent cell-mediated cytotoxicity. Therefore, CTLA-4–blocking Abs of the human IgG₂ subtype were chosen, because IgG₂ induces minimal complement activation and Ab-dependent cell-mediated cytotoxicity [51] and decreases the possibility of cytokine release syndrome with Ab infusion into humans. To minimize potential development of immune responses to the CTLA-4 Abs, fully human CTLA-4–blocking Abs were generated at Abgenix, Inc. (Fremont, CA) in engineered XenoMice^TM expressing transgenic human Ig genes.

Preclinical Tremelimumab Data
Extensive preclinical testing led to selection of tremelimumab for clinical development.

Tremelimumab is highly selective for CTLA-4, demonstrating over 500-fold greater selectivity than for CD28, a costimulatory TCR that binds B7 ligands with lower affinity than CTLA-4. Competition binding studies have shown that tremelimumab efficiently blocks binding of CTLA-4 to B7–1 and B7–2 with average 50% inhibition concentrations of 0.65 and 0.50 nM, respectively [52]. The lack of nonspecific cytokine release and binding to Fc receptors for the IgG₂ isotype was confirmed by in vitro studies in human whole blood [52]. Flow cytometry demonstrated a high affinity of tremelimumab for CTLA-4 expressed on the surface of activated human and cynomolgus monkey T cells, but not T cells from mouse, rat, hamster, or rabbit. The affinity for binding to human CTLA-4 was subnanomolar (0.28 nM), and approximately fourfold higher than for monkey CTLA-4 (0.98 nM) [52]. The cynomolgus monkey was selected for preclinical toxicologic evaluation of tremelimumab.

Toxicology Studies in Cynomolgus Monkeys
Toxicity of tremelimumab was assessed in cynomolgus monkeys in single-dose and 1- and 6-month weekly dosing studies. Treatment-related effects observed in the 6-month study included skin rash and persistent loose stools with decreased appetite and weight loss at 50 mg/kg per week. These findings resulted in cessation of dosing and/or euthanasia of some monkeys at 50 mg/kg. Microscopically there was mononuclear cell inflammation in the skin, cecum, and/or colon. In concert with lymphoid hyperplasia in the lymphoid organs, a dose-dependent increase in the incidence and severity of mononuclear cell infiltration or inflammation was observed in most tissues with a spontaneous background incidence of mononuclear cell aggregates. With the exception of moderate to marked thyroid follicular atrophy, observed in association with alterations in thyroid hormones in two animals at >15 mg/kg per week, these changes appeared reversible. These findings in monkeys were generally consistent with tremelimumab predicted pharmacology and suggested that clinical use may affect the gastrointestinal tract, the skin, lymphoid and thyroid tissues, and the hematological system. Preclinical findings correlated with the dose-limiting toxicities (DLTs) (diarrhea and skin rash), as well as non-dose–limiting thyroid abnormalities, observed in clinical trials of tremelimumab [29, 53].

An Ex Vivo Potency Assay for CTLA-4 Blockade
A potency assay was developed that detected enhanced cytokine production of superantigen-stimulated T cells. A plasma concentration 30 µg/ml was identified as the minimum effective in vitro concentration of tremelimumab that produced a significant increase in T-cell activation [52, 54]. Ex vivo studies using whole blood or peripheral blood mononuclear cells demonstrated that tremelimumab reproducibly enhanced superantigen-induced IL-2 production [54]. To assess the feasibility of the staphylococcal enterotoxin A assay for use in clinical trials, cynomolgus monkeys were given a single i.v. dose of 10 mg/kg tremelimumab and had blood samples collected for evaluation. Enhancement of IL-2 production was observed in ex vivo superantigen-stimulated blood samples from both animals, suggesting potential utility for the assay as a pharmacodynamic endpoint in clinical studies.

	EARLY CLINICAL DEVELOPMENT OF CTLA-4–BLOCKING ABS

Top Learning Objectives Abstract Introduction Preclinical Development of... Early Clinical Development of... Testing the Expansion of... Modulation of Treg Cells... Conclusions Disclosure of Potential... Acknowledgments References

 
A lead prototype anti–CTLA-4 compound CP-642,570 was identified, but its clinical development was discontinued because of the induction of transient thrombocytopenia in the first-in-human (FIH) study. Tremelimumab was the second anti–CTLA-4 from Pfizer brought to the clinic (Table 1). Its early clinical development plan followed three treatment strategies: (a) single-agent activity in cancer, (b) combination with established anticancer therapies hypothesized to enhance release of endogenous tumor antigens as well as induce other favorable effects within the tumor, and (c) combination with a cancer vaccine as a source of exogenous tumor antigen. The first scenario has been pursued through pivotal studies in melanoma.

Pharmacokinetic analysis demonstrated that tremelimumab behaves exactly like endogenous human IgG₂ [29]. At 10 and 15 mg/kg, plasma concentrations were >30 µg/ml in the majority of patients 4 and 8 weeks, respectively, after the initial dose [29]. Therefore, the minimal efficacious concentration of 10–30 µg/ml, defined by the preclinical studies, can be achieved in plasma for prolonged periods of time. These data cannot be taken as evidence of sustained CTLA-4 target saturation. Direct testing of target saturation is technically challenging, since the CTLA-4 target receptor is only transiently expressed on activated human T cells. However, it can be stated that these doses lead to toxicity and tumor response consistent with the anticipated pharmacodynamic effects of a CTLA-4–blocking mAb.

Phase I testing of multiple monthly doses (3–10 mg/kg) of tremelimumab (Study 1002) was initiated [53]. Fourteen patients with measurable metastatic melanoma were enrolled. Patients in the 3 and 6 mg/kg monthly cohorts experienced rapid tumor progression. One of eight patients entered at 10 mg/kg monthly had a pathologically defined partial response (PR) of in-transit metastasis [53]. The phase I monthly redosing study was followed by a phase II redosing trial (Study 1002 randomized phase II study) comparing two dose levels and schedules (10 mg/kg monthly and 15 mg/kg quarterly). Final results from this study are not yet available; accrual was completed in November of 2005. Interim analysis indicated similar antitumor activity between the two regimens; three (8%) patients treated with 10 mg/kg monthly (n = 40) had an objective response (1 complete response [CR] and 2 PRs) and three (7%) patients treated with 15 mg/kg (n = 42) quarterly had a response (1 CR and 2 PRs) [58]. Both regimens were well tolerated, but compared with 10 mg/kg monthly, 15 mg/kg quarterly was associated with a lower incidence of serious adverse events (AEs) (9% versus 14%, respectively) and grade 3 or 4 AEs (11% versus 18%, respectively) [58].

Collectively, these three studies support the notion that tremelimumab can break peripheral tolerance to self tissues, including cancer, based on the development of immune-related and autoimmune phenomena (e.g., colitis, vitiligo, thyroiditis with elevated antithyroid antibodies) and objective tumor regressions in patients with melanoma [29, 53]. Given this body of evidence, the single-agent strategy of tremelimumab was taken to registration trials in locally advanced and metastatic melanoma (Table 2).

Combination with a Cancer Vaccine
Preclinical studies suggest that a cancer vaccine may be needed for CTLA-4–blocking mAbs to induce regression in poorly immunogenic experimental tumor models ([2, 4–6, 9–13]. One of the best examples is the B16 murine melanoma model, where tumor response to CTLA-4 blockade is only evident if the anti-CTLA-4 Abs are given with a GM-CSF B16 tumor engineered vaccine [4], peptide pulsed dendritic cell vaccines [6], or depletion of Treg cells [7]. Because most human cancers are believed to be poorly immunogenic, combination with a cancer vaccine was pursued in the clinical setting. A small pilot trial was pursued combining tremelimumab with a vaccine that had demonstrated antitumor activity against metastatic melanoma and for which there was anecdotal evidence of enhanced activity with sequential CTLA-4 blockade [60, 61]. Study 0003 combines an autologous dendritic cell vaccine pulsed with the MART-1_26–36 immunodominant peptide within HLA-A*0201 with a dose escalation of tremelimumab administered at monthly intervals. This study completed accrual of 16 patients in February 2007. The accrual rate was limited because of the lengthy interval between patients and cohorts to detect potential delayed autoimmune phenomena. Analysis of immunologic and clinical endpoints is ongoing. A new phase I clinical trial combining tremelimumab with the oligodeoxynucleotide PF-3512676 (formerly known as CPG 7909, Table 1) is currently open to accrual.

Choice of Tremelimumab Dose and Schedule for Registration Trial Testing
Preclinical studies demonstrated a concentration-dependent effect of tremelimumab on activated human T cells [52, 54, 62], and the dose-escalation Phase I studies allowed verification of these findings. In both phase I tremelimumab clinical trials, increasing doses resulted in longer durations of exposure, with a greater frequency of responses and a higher incidence of clinical adverse effects (Table 3). In Study 1001 [29], grade I–II toxicities attributable to tremelimumab first developed at the 1 mg/kg dose, with occasional diarrhea. Grade III–IV diarrhea was noted in one patient at 10 mg/kg and two patients at 15 mg/kg after a single infusion [29]. The most commonly reported toxicities thought to be at least possibly related to tremelimumab administration were diarrhea, dermatitis, pruritus, and fatigue [58]. Antitumor activity also increased with higher doses and longer duration of systemic exposure [29, 53]. Most patients who experienced antitumor activity had plasma concentrations of tremelimumab above the target of 30 µg/ml for 4 weeks [29]. Therefore, the preclinical studies accurately predicted concentrations of tremelimumab needed to break tolerance to self and induce antitumor responses.

Clinical trials with anti–CTLA-4 Abs indicate a potential association with autoimmune phenomena, but there are limited long-term data. Autoimmune phenomena observed in Study 1001 included diarrhea, dermatitis, vitiligo, panhypopituitarism, and hyperthyroidism [29]. Among HLA-A*0201⁺ patients with stage IV melanoma (n = 56) treated with 3 mg/kg ipilimumab with or without gp100 peptide vaccine, 14 (25%) patients developed grade 3 or 4 autoimmune phenomena (e.g., colitis, dermatitis, uveitis, enterocolitis, hepatitis, and hypophysitis) [25]. At this time, it is not known whether the appearance of autoimmunity is associated with response or prolonged survival. Based on these data, pivotal clinical trials have been initiated with single-agent tremelimumab given at 15 mg/kg every 3 months to patients with metastatic melanoma (Table 2). A single-arm phase II clinical trial in patients with previously treated disease (Study 1008) completed accrual in October 2006. A phase III randomized clinical trial in previously untreated patients with metastatic melanoma is currently open to accrual. This dose and schedule are also being tested in phase II clinical trials in patients with metastatic colorectal carcinoma and non-small cell lung cancer (Table 1).

	TESTING THE EXPANSION OF ANTIGEN-SPECIFIC T CELLS AFTER ADMINISTRATION OF CTLA-4–BLOCKING MABS

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The hypothesis that CTLA-4 blockade will result in activation and expansion of antigen-specific T cells can be tested using single-cell immune monitoring assays, like the MHC tetramer, enzyme-linked immunospot, and intracellular cytokine staining assays [63]. Pilot studies indicated no generalized increases in the number of circulating tumor antigen-specific T cells after administration of tremelimumab. However, in an expansion cohort of HLA-A*0201⁺ patients within the Study 1002 phase I/II multidose trial receiving 10 mg/kg tremelimumab monthly, a heavy infiltrate by CD8⁺ CTLs was observed in regressing tumor lesions [64]. The ability of CTLA-4–blocking Abs to specifically expand tumor antigen-specific T cells circulating in peripheral blood has also been tested using ipilimumab in patients with metastatic melanoma [23–25, 65]. Investigators at the Surgery Branch, National Cancer Institute, concluded that ipilimumab does not expand gp100-specific T cells beyond levels observed in gp100-based peptide vaccine clinical trials [23, 25–27]. In contrast, Sanderson et al. [24] concluded that T-cell activation to immunodominant peptides from MART-1, gp100, and tyrosinase administered with ipilimumab in the adjuvant setting may be higher than that seen with other adjuvants (e.g., GM-CSF, IL-12). In addition, ipilimumab also induces nontumor antigen-specific T cell activation as detected by increased expression of the T cell activation marker HLA-DR on the surface of peripheral CD4⁺ and CD8⁺ T cells [23, 25].

	MODULATION OF TREG CELLS AFTER ADMINISTRATION OF CTLA-4–BLOCKING MABS

Top Learning Objectives Abstract Introduction Preclinical Development of... Early Clinical Development of... Testing the Expansion of... Modulation of Treg Cells... Conclusions Disclosure of Potential... Acknowledgments References

 
CTLA-4 blockade may induce antitumor immune responses by blocking negative signaling provided by CTLA-4 expressed on Treg cells, which may either stimulate IDO production in dendritic cells and have tolerizing rather than immunogenic effects on T cells [40, 42] or directly interact with B7 costimulatory molecules on T cells [43]. Studies were conducted in a subset of patients within the Study 1002 phase II study to determine the potential role of modulating Treg cells on antitumor activity [66]. It was reported that patients with objective response or disease stabilization had a decrease in CD4⁺/CD25⁺ Treg cells and in constitutive IL-10 secretion compared with patients with progressive disease. However, functional assays were not reported [66]. In contrast, CTLA-4 blockade with ipilimumab did not alter the number or function of circulating Treg cells when tested by functional assays of suppressor activity (the gold standard for Treg cell quantitation) [44], mRNA levels of the Treg-specific transcription factor Foxp3 [67], and flow cytometric analysis of surface markers on Treg cells [26].

	CONCLUSIONS

Top Learning Objectives Abstract Introduction Preclinical Development of... Early Clinical Development of... Testing the Expansion of... Modulation of Treg Cells... Conclusions Disclosure of Potential... Acknowledgments References

 
Fully human anti–CTLA-4 mAbs appear to break tolerance to self and tumor antigens, resulting in antitumor activity in some patients. The preclinical development of tremelimumab guided the early clinical development. In particular, ex vivo assays suggested that exposure to achievable concentrations of circulating anti–CTLA-4 Ab would result in immune activation. Clinical dose-escalation trials suggested that the clinical and biologic effects of anti–CTLA-4 Abs are dose dependent, the predicted target plasma concentrations providing a reasonable model of the anticipated clinical effects of CTLA-4 blockade in humans. Combined preclinical and clinical data have allowed the rational choice of dosing and schedule for ongoing clinical trials in patients with malignant melanoma.

	DISCLOSURE OF POTENTIAL CONFLICTS OF INTEREST

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J.G.-N., R.M., D.J.G., P.C.C., and D.C.H. own stock in and have received support from Pfizer. A.R. has acted as a consultant for and performed contract work for Pfizer. D.A.N. is an employee of Pfizer.

	ACKNOWLEDGMENTS

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We would like to acknowledge Viviana Bozon, M.D., Dmitri Pavlov, Ph.D., and Cecile A. Bulanhagui, M.S., Stephen Eck, M.D., Ph.D. and Karen Ferrante, M.D., from Oncology Clinical Development, PGRD, Jeannie Greene, Sandra Dombrovsky from Developmental Operations, PGRD, Kelly Page and John Cusmano, Global Project Management, PGRD, John A. Glaspy, M.D., M.P.H., Begonya Comin-Anduix, Ph.D., Rosalinda Rivera, Arturo Villanueva, and Elisabeth Seja from UCLA, and Luis H. Camacho, M.D., M.P.H., from the M.D. Anderson Cancer Center, for their significant contribution to the conduction of early clinical trials with tremelimumab; Laura Dill Morton, D.V.M., Ph.D., Research Fellow from Drug Safety R&D, PGRD, for contributions to the analysis of the preclinical toxicology studies; Hyam Levitsky, M.D., at Johns Hopkins University for providing blood samples from prostate cancer patients; investigators at Abgenix Inc. for Ab development; and the many Preclinical CTLA-4 Team members, including Carol B. Donovan, Michael J. Primiano, Joseph P. Gardner, Edward J. Natoli, Rodney W. Morgan, Robert J. Mather, Jeffrey J. Burkwit, Matthew J. Bruns, Timothy J. Paradis, Susan H. Cole, David H. Singleton, Paul A. Hermes, Mark J. Neveu, Glenn C. Andrews, Christopher D. Castro, Ronald P. Gladue, Eileen A. Elliott, and Vahe Bedian, for contributions to the discovery and preclinical development of tremelimumab. A.R. is supported in part by K23 CA93376, the Jonsson Comprehensive Cancer Center, and the Melanoma Research Foundation. The current affiliation of D.J.G. is Department of Pathology, Amgen Inc., Thousand Oaks, California.

	REFERENCES

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1. Leach DR, Krummel MF, Allison JP. Enhancement of antitumor immunity by CTLA-4 blockade. Science 1996;271:1734–1736.[Abstract]
2. Sotomayor EM, Borrello I, Tubb E et al. In vivo blockade of CTLA-4 enhances the priming of responsive T cells but fails to prevent the induction of tumor antigen-specific tolerance. Proc Natl Acad Sci U S A 1999;96:11476–11481.[Abstract/Free Full Text]
3. Kwon ED, Foster BA, Hurwitz AA et al. Elimination of residual metastatic prostate cancer after surgery and adjunctive cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) blockade immunotherapy. Proc Natl Acad Sci U S A 1999;96:15074–15079.[Abstract/Free Full Text]
4. van Elsas A, Hurwitz AA, Allison JP. Combination immunotherapy of B16 melanoma using anti-cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and granulocyte/macrophage colony-stimulating factor (GM-CSF)-producing vaccines induces rejection of subcutaneous and metastatic tumors accompanied by autoimmune depigmentation. J Exp Med 1999;190:355–366.[Abstract/Free Full Text]
5. Hurwitz AA, Foster BA, Kwon ED et al. Combination immunotherapy of primary prostate cancer in a transgenic mouse model using CTLA-4 blockade. Cancer Res 2000;60:2444–2448.[Abstract/Free Full Text]
6. van Elsas A, Sutmuller RP, Hurwitz AA et al. Elucidating the autoimmune and antitumor effector mechanisms of a treatment based on cytotoxic T lymphocyte antigen-4 blockade in combination with a B16 melanoma vaccine: Comparison of prophylaxis and therapy. J Exp Med 2001;194:481–489.[Abstract/Free Full Text]
7. Sutmuller RP, van Duivenvoorde LM, van Elsas A et al. Synergism of cytotoxic T lymphocyte-associated antigen 4 blockade and depletion of CD25(+) regulatory T cells in antitumor therapy reveals alternative pathways for suppression of autoreactive cytotoxic T lymphocyte responses. J Exp Med 2001;194:823–832.[Abstract/Free Full Text]
8. Ko K, Yamazaki S, Nakamura K et al. Treatment of advanced tumors with agonistic anti-GITR mAb and its effects on tumor-infiltrating Foxp3+CD25+CD4+ regulatory T cells. J Exp Med 2005;202:885–891.[Abstract/Free Full Text]
9. Chambers CA, Kuhns MS, Egen JG et al. CTLA-4-mediated inhibition in regulation of T cell responses: Mechanisms and manipulation in tumor immunotherapy. Annu Rev Immunol 2001;19:565–594.[CrossRef][Medline]
10. McCoy KD, Hermans IF, Fraser JH et al. Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) can regulate dendritic cell-induced activation and cytotoxicity of CD8(+) T cells independently of CD4(+) T cell help. J Exp Med 1999;189:1157–1162.[Abstract/Free Full Text]
11. Hernandez J, Ko A, Sherman LA. CTLA-4 blockade enhances the CTL responses to the p53 self-tumor antigen. J Immunol 2001;166:3908–3914.[Abstract/Free Full Text]
12. Hurwitz AA, Yu TF, Leach DR et al. CTLA-4 blockade synergizes with tumor-derived granulocyte-macrophage colony-stimulating factor for treatment of an experimental mammary carcinoma. Proc Natl Acad Sci U S A 1998;95:10067–10071.[Abstract/Free Full Text]
13. Hsu FJ, Komarovskaya M. CTLA4 blockade maximizes antitumor T-cell activation by dendritic cells presenting idiotype protein or opsonized anti-CD20 antibody-coated lymphoma cells. J Immunother 2002;25:455–468.[CrossRef][Medline]
14. Keler T, Halk E, Vitale L et al. Activity and safety of CTLA-4 blockade combined with vaccines in cynomolgus macaques. J Immunol 2003;171:6251–6259.[Abstract/Free Full Text]
15. Gorelik L, Flavell RA. Immune-mediated eradication of tumors through the blockade of transforming growth factor-beta signaling in T cells. Nat Med 2001;7:1118–1122.[CrossRef][Medline]
16. Greenwald RJ, Freeman GJ, Sharpe AH. The B7 family revisited. Annu Rev Immunol 2005;23:515–548.[CrossRef][Medline]
17. Mueller DL. E3 ubiquitin ligases as T cell anergy factors. Nat Immunol 2004;5:883–890.[CrossRef][Medline]
18. Gabrilovich DI, Chen HL, Girgis KR et al. Production of vascular endothelial growth factor by human tumors inhibits the functional maturation of dendritic cells. Nat Med 1996;2:1096–1103.[CrossRef][Medline]
19. Chen L. Co-inhibitory molecules of the B7-CD28 family in the control of T-cell immunity. Nat Rev Immunol 2004;4:336–347.[CrossRef][Medline]
20. Waterhouse P, Penninger JM, Timms E et al. Lymphoproliferative disorders with early lethality in mice deficient in CTLA-4. Science 1995;270:985–988.[Abstract/Free Full Text]
21. Tivol EA, Borriello F, Schweitzer AN et al. Loss of CTLA-4 leads to massive lymphoproliferation and fatal multiorgan tissue destruction, revealing a critical negative regulatory role of CTLA-4. Immunity 1995;3:541–547.[CrossRef][Medline]
22. Hodi FS, Mihm MC, Soiffer RJ et al. Biologic activity of cytotoxic T lymphocyte-associated antigen 4 antibody blockade in previously vaccinated metastatic melanoma and ovarian carcinoma patients. Proc Natl Acad Sci U S A 2003;100:4712–4717.[Abstract/Free Full Text]
23. Phan GQ, Yang JC, Sherry RM et al. Cancer regression and autoimmunity induced by cytotoxic T lymphocyte-associated antigen 4 blockade in patients with metastatic melanoma. Proc Natl Acad Sci U S A 2003;100:8372–8377.[Abstract/Free Full Text]
24. Sanderson K, Scotland R, Lee P et al. Autoimmunity in a phase I trial of a fully human anti-cytotoxic T-lymphocyte antigen-4 monoclonal antibody with multiple melanoma peptides and Montanide ISA 51 for patients with resected stages III and IV melanoma. J Clin Oncol 2005;23:741–750.[Abstract/Free Full Text]
25. Attia P, Phan GQ, Maker AV et al. Autoimmunity correlates with tumor regression in patients with metastatic melanoma treated with anti-cytotoxic T-lymphocyte antigen-4. J Clin Oncol 2005;23:6043–6053.[Abstract/Free Full Text]
26. Maker AV, Attia P, Rosenberg SA. Analysis of the cellular mechanism of antitumor responses and autoimmunity in patients treated with CTLA-4 blockade. J Immunol 2005;175:7746–7754.[Abstract/Free Full Text]
27. Maker AV, Phan GQ, Attia P et al. Tumor regression and autoimmunity in patients treated with cytotoxic T lymphocyte-associated antigen 4 blockade and interleukin 2: A phase I/II study. Ann Surg Oncol 2005;12:1005–1016.[CrossRef][Medline]
28. Blansfield JA, Beck KE, Tran K et al. Cytotoxic T-lymphocyte-associated antigen-4 blockage can induce autoimmune hypophysitis in patients with metastatic melanoma and renal cancer. J Immunother 2005;28:593–598.[CrossRef][Medline]
29. Ribas A, Camacho LH, Lopez-Berestein G et al. Antitumor activity in melanoma and anti-self responses in a phase I trial with the anti-cytotoxic T lymphocyte-associated antigen 4 monoclonal antibody CP-675,206. J Clin Oncol 2005;23:8968–8977.[Abstract/Free Full Text]
30. Beck KE, Blansfield JA, Tran KQ et al. Enterocolitis in patients with cancer after antibody blockade of cytotoxic T-lymphocyte-associated antigen 4. J Clin Oncol 2006;24:2283–2289.[Abstract/Free Full Text]
31. Jinushi M, Hodi FS, Dranoff G. Therapy-induced antibodies to MHC class I chain-related protein A antagonize immune suppression and stimulate antitumor cytotoxicity. Proc Natl Acad Sci U S A 2006;103:9190–9195.[Abstract/Free Full Text]
32. Maker AV, Yang JC, Sherry RM et al. Intrapatient dose escalation of anti-CTLA-4 antibody in patients with metastatic melanoma. J Immunother 2006;29:455–463.[CrossRef][Medline]
33. Brunet JF, Denizot F, Luciani MF et al. A new member of the immunoglobulin superfamily–CTLA-4. Nature 1987;328:267–270.[CrossRef][Medline]
34. Walunas TL, Lenschow DJ, Bakker CY et al. CTLA-4 can function as a negative regulator of T cell activation. Immunity 1994;1:405–413.[CrossRef][Medline]
35. Wang XB, Giscombe R, Yan Z et al. Expression of CTLA-4 by human monocytes. Scand J Immunol 2002;55:53–60.[CrossRef][Medline]
36. Teft WA, Kirchhof MG, Madrenas J. A molecular perspective of CTLA-4 function. Annu Rev Immunol 2006;24:65–97.[CrossRef][Medline]
37. Boon T, Coulie PG, Van den Eynde BJ et al. Human T cell responses against melanoma. Annu Rev Immunol 2006;24:175–208.[CrossRef][Medline]
38. Lee KM, Chuang E, Griffin M et al. Molecular basis of T cell inactivation by CTLA-4. Science 1998;282:2263–2266.[Abstract/Free Full Text]
39. Paradis TJ, Floyd E, Burkwit J et al. The anti-tumor activity of anti-CTLA-4 is mediated through its induction of IFN gamma. Cancer Immunol Immunother 2001;50:125–133.[CrossRef][Medline]
40. Grohmann U, Orabona C, Fallarino F et al. CTLA-4-Ig regulates tryptophan catabolism in vivo. Nat Immunol 2002;3:1097–1101.[CrossRef][Medline]
41. Fallarino F, Grohmann U, Hwang KW et al. Modulation of tryptophan catabolism by regulatory T cells. Nat Immunol 2003;4:1206–1212.[CrossRef][Medline]
42. Munn DH, Sharma MD, Hou D et al. Expression of indoleamine 2,3-dioxygenase by plasmacytoid dendritic cells in tumor-draining lymph nodes. J Clin Invest 2004;114:280–290.[CrossRef][Medline]
43. Paust S, Lu L, McCarty N et al. Engagement of B7 on effector T cells by regulatory T cells prevents autoimmune disease. Proc Natl Acad Sci U S A 2004;101:10398–10403.[Abstract/Free Full Text]
44. Shevach EM. CD4+ CD25+ suppressor T cells: More questions than answers. Nat Rev Immunol 2002;2:389–400.[Medline]
45. Mellor AL, Chandler P, Baban B et al. Specific subsets of murine dendritic cells acquire potent T cell regulatory functions following CTLA4-mediated induction of indoleamine 2,3 dioxygenase. Int Immunol 2004;16:1391–1401.[Abstract/Free Full Text]
46. Groh V, Wu J, Yee C et al. Tumour-derived soluble MIC ligands impair expression of NKG2D and T-cell activation. Nature 2002;419:734–738.[CrossRef][Medline]
47. Contardi E, Palmisano GL, Tazzari PL et al. CTLA-4 is constitutively expressed on tumor cells and can trigger apoptosis upon ligand interaction. Int J Cancer 2005;117:538–550.[CrossRef][Medline]
48. Dariavach P, Mattei MG, Golstein P et al. Human Ig superfamily CTLA-4 gene: Chromosomal localization and identity of protein sequence between murine and human CTLA-4 cytoplasmic domains. Eur J Immunol 1988;18:1901–1905.[Medline]
49. Chen L, Ashe S, Brady WA et al. Costimulation of antitumor immunity by the B7 counterreceptor for the T lymphocyte molecules CD28 and CTLA-4. Cell 1992;71:1093–1102.[CrossRef][Medline]
50. Krummel MF, Allison JP. CD28 and CTLA-4 have opposing effects on the response of T cells to stimulation. J Exp Med 1995;182:459–465.[Abstract/Free Full Text]
51. Bruggemann M, Williams GT, Bindon CI et al. Comparison of the effector functions of human immunoglobulins using a matched set of chimeric antibodies. J Exp Med 1987;166:1351–1361.[Abstract/Free Full Text]
52. Hanson DC, Canniff PC, Primiano MJ et al. Preclinical in vitro characterization of anti-CTLA4 therapeutic antibody CP-675,206. Am Assoc Cancer Res Meeting Abstracts 2004;2004:877-b-.
53. Ribas A, Bozon VA, Lopez-Berestein G et al. Phase 1 trial of monthly doses of the human anti-CTLA4 monoclonal antibody CP-675,206 in patients with advanced melanoma. J Clin Oncol 2005;23(suppl):716s.
54. Canniff PC, Donovan CB, Burkwit JJ et al. CP-675,206 anti-CTLA4 antibody clinical candidate enhances IL-2 production in cancer patient T cells in vitro regardless of tumor type or stage of disease. Am Assoc Cancer Res Meeting Abstracts 2004;2004:164-a-.
55. Rosenberg SA. Karnofsky Memorial Lecture. The immunotherapy and gene therapy of cancer. J Clin Oncol 1992;10:180–199.[Medline]
56. Tsao H, Atkins MB, Sober AJ. Management of cutaneous melanoma. N Engl J Med 2004;351:998–1012.[Free Full Text]
57. Atkins MB. Cytokine-based therapy and biochemotherapy for advanced melanoma. Clin Cancer Res 2006;12:2353s–2358s.[Abstract/Free Full Text]
58. Gomez-Navarro J, Sharma A, Bozon V et al. Dose and schedule selection for the anti-CTLA4 monoclonal antibody (mAb) CP-675,206 in patients (pts) with metastatic melanoma. J Clin Oncol 2006;24(suppl):460s.[CrossRef]
59. Eigentler TK, Caroli UM, Radny P et al. Palliative therapy of disseminated malignant melanoma: A systematic review of 41 randomised clinical trials. Lancet Oncol 2003;4:748–759.[CrossRef][Medline]
60. Ribas A, Glaspy JA, Lee Y et al. Role of dendritic cell phenotype, determinant spreading, and negative costimulatory blockade in dendritic cell-based melanoma immunotherapy. J Immunother 2004;27:354–367.[CrossRef][Medline]
61. Butterfield LH, Ribas A, Dissette VB et al. Determinant spreading associated with clinical response in dendritic cell-based immunotherapy for malignant melanoma. Clin Cancer Res 2003;9:998–1008.[Abstract/Free Full Text]
62. Millham R, Pavlov D, Canniff P et al. Ex vivo blood stimulation assay as a translational research tool in the development of the ticilimumab (CP-675,206). J Clin Oncol 2006;24(suppl):110s.
63. Keilholz U, Weber J, Finke JH et al. Immunologic monitoring of cancer vaccine therapy: Results of a workshop sponsored by the Society for Biological Therapy. J Immunother 2002;25:97–138.[Medline]
64. Ribas A, Comin-Anduix B, Bozon V et al. Antigen-specific T cell responses in patients with melanoma treated with the CLA4 blocking mAb ticilimumab. J Clin Oncol 2006;24(suppl):461s.
65. Korman A, Yellin M, Keler T. Tumor immunotherapy: Preclinical and clinical activity of anti-CTLA4 antibodies. Curr Opin Investig Drugs 2005;6:582–591.[Medline]
66. Reuben JM, Lee BN, Li C et al. Biologic and immunomodulatory events after CTLA-4 blockade with ticilimumab in patients with advanced malignant melanoma. Cancer 2006;106:2437–2444.[CrossRef][Medline]
67. Hori S, Nomura T, Sakaguchi S. Control of regulatory T cell development by the transcription factor Foxp3. Science 2003;299:1057–1061.[Abstract/Free Full Text]

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