Oncologist. The. Melanoma and Cutaneous Malignancies

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1 The Oncologist Melanoma and Cutaneous Malignancies What Is the Role of Cytotoxic T Lymphocyte Associated Antigen 4 Blockade in Patients with Metastatic Melanoma? CAROLINE ROBERT, a FRANCOIS GHIRINGHELLI b a Institute Gustave Roussy, Villejuif, France; b Department of Oncology, Dijon Hospital, Dijon, France Disclosures: Caroline Robert: Consultant/advisory role: Bayer, Pfizer, Bristol-Myers Squibb; Honoraria: Bayer, Pfizer, Bristol- Myers Squibb; Francois Ghiringhelli: None. The article discusses unlabeled, investigational, or alternative use of a product, device or technique: tremelimumab (CP-675,206, Bristol-Myers Squibb) and ipilimumab (MDX-010, Pfizer) for metastatic melanoma. The content of this article has been reviewed by independent peer reviewers to ensure that it is balanced, objective, and free from commercial bias. No financial relationships relevant to the content of this article have been disclosed by the independent peer reviewers. Key Words. Cytotoxic T lymphocyte associated antigen 4 Melanoma Metastasis Biomarkers ABSTRACT With increasing knowledge of the molecular basis of the immune system and mechanisms of tumor tolerance, novel approaches to treating malignant diseases refractory to standard therapies are being investigated. Monoclonal antibodies (mabs) that bind cytotoxic T lymphocyte associated antigen (CTLA)-4 can block inhibitory signals normally generated through this receptor, thus prolonging and sustaining T-cell activation and proliferation. These antibodies are being developed and tested in patients with metastatic melanoma. This article reviews data published or presented at scientific congresses describing the clinical safety and antitumor activity of two different anti CTLA-4 mabs: tremelimumab (CP-675,206) and ipilimumab (MDX-010). Overall, although the response rate has not been consistently higher than the response rates associated with other treatments, the induction of durable responses and the favorable safety profile observed with anti CTLA-4 mabs are encouraging. However, the true advantage of these new drugs may depend largely on the characterization of predictive biomarkers of activity and subsequent targeting of responsive patients. The Oncologist 2009;14: INTRODUCTION Although the immune system can detect and destroy cancer cells, tumors develop when malignant cells actively evade the immune system or induce host tolerance [1]. One approach to cancer therapy is to increase the activity of a patient s own immune system and thus increase the possibility of tumor detection and destruction. However, tumor-induced tolerance can be a barrier to successful immunotherapy. The roles of several critical immunoregulatory elements have recently been elucidated, providing new insight and direction for overcoming tumor tolerance. One approach that has evolved from these insights is to promote T-cell activation by blocking inhibitory signals from receptors such as cytotoxic T lymphocyte associated antigen (CTLA)-4 [2]. T cells are activated when the T-cell receptor (TCR) complex binds antigen presented by major histocompatibil- Correspondence: Caroline Robert, M.D., Ph.D., Dermatology Unit, Institute Gustave Roussy, 39 Rue Camille Desmoulins, Villejuif Cedex, France. Telephone: ; Fax: ; caroline.robert@igr.fr Received February 20, 2009; accepted for publication June 23, 2009; first published online in The Oncologist Express on August 1, AlphaMed Press /2009/$30.00/0 doi: /theoncologist The Oncologist 2009;14:

2 Robert, Ghiringhelli 849 Figure 1. Two signals are required for full T-cell activation. T-cell activation involves binding of T-cell receptor (TCR) to antigen (Ag)-bound major histocompatibility complex (MHC) on the antigen-presenting cell (APC) (A). Full activation also requires binding of costimulatory receptors (e.g., B7 [CD80/ 86]) on the APC to receptors (e.g., CD28) on the T cell (B). ity complex (MHC) I and MHC II on antigen-presenting cells (APCs) (Fig. 1A). T cells also express cosignaling receptors that direct and modulate TCR signals. When the principal costimulatory receptor on the T cell (CD28) interacts with B7 (CD80/86) on the APCs, the costimulatory signal induces T-cell proliferation, cytokine secretion, and changes in gene expression and metabolism (Fig. 1B). CTLA-4 is a key element that induces immune tolerance and the main negative regulator of T-cell mediated antitumor immune responses [3, 4]. CTLA-4 is a homologue of CD28, with a higher affinity for B7. Binding of CTLA-4 and B7 sends an inhibitory signal that downregulates T-cell activation (Fig. 2A). CTLA-4 is upregulated on activated T cells, where it successfully competes with CD28 for binding to B7 [5, 6]. This sends an inhibitory signal that downregulates T-cell activation and serves as a natural brake on the immune system, altering both downstream cytokine production and the cell-cycle machinery required for proliferation [7 10]. One of the mechanisms by which CTLA-4 signaling induces T-cell inhibition may be through CTLA-4 back signaling via B7 into APCs by upregulating the indoleamine 2,3 deoxygenase (IDO) enzyme [11]. This enzyme is responsible for degradation of tryptophan, which is essential for T-cell proliferation. Therefore, stimulation of IDO activity exerts an immunosuppressive stimulus by reducing T-cell proliferation. CTLA-4 is also expressed constitutively on the surface of regulatory T cells (Tregs) and is detectable on approximately 50% of Tregs, compared with 1% on naive helper T cells [12]. It was demonstrated recently that, in a murine model, CTLA-4 ligation on Tregs results in a significant decrease in APC presentation capacity and effector T-cell downregulation [13] (Fig. 2B). Figure 2. CTLA-4 blockade prevents downregulation of T cells. After T-cell activation, CTLA-4 receptors upregulate from intracellular stores, compete for binding to B7 (CD80/ 86), and downregulate T-cell activation. Reverse signaling via CTLA-4 induces an increase in indoleamine 2,3 deoxygenase (IDO) in the antigen-presenting cell (APC) that decreases APC function (A). Ligation of CTLA-4 on regulatory T cells (Tregs) to an APC induces a decrease in APC function and in T-cell proliferation (B). Abbreviations: Ag, antigen; CTLA-4, cytotoxic T lymphocyte associated antigen 4; MHC, major histocompatibility complex; TCR, T cell receptor. The significance of the role of CTLA-4 was revealed with murine knockout models. Mice lacking CTLA-4 exhibit massive T-cell proliferation, have an enlarged spleen and lymph nodes, and develop lymphoproliferative disease [14 16]. Furthermore, blockade of CTLA-4 has been shown to enhance T-cell functions, such as cytokine production, both in vitro and in vivo. In a murine model of cancer, anti CTLA-4 monoclonal antibody (mab) treatment inhibited the growth of new or established tumors and resulted in greater immunity to secondary exposure with tumor cells [17]. Based on preclinical data, it was hypothesized that blocking the interaction of CTLA-4 and B7 in humans would sustain T-cell activation and proliferation, thereby preventing tumor tolerance and potentially increasing antitumor activity. CTLA-4 BLOCKADE mabs directed against CTLA-4 can have a higher affinity for CTLA-4 than B7 [6]. These mabs successfully compete

3 850 CTLA-4 Monoclonal Antibodies in Metastatic Melanoma Clinical Development of Anti CTLA-4 mabs in Patients with Metastatic Melanoma Both tremelimumab and ipilimumab have been investigated in clinical trials for patients with metastatic melanoma (Tables 1 [2, 20 27] and 2 [28 39]). These studies have evaluated a variety of doses and schedules of anti CTLA-4 mabs as single agents or in combination with other cancer therapies [25, 27, 28, 40]. Figure 3. Antitumor effects of CTLA-4 blockade. Anti CTLA4 monoclonal antibodies (mabs) inhibit interaction of B7 (CD80/86) and CTLA-4, thus prolonging T-cell activation (A). Inhibition of CTLA-4 on Tregs induces T-cell proliferation and has antitumor effects (B) [13]. Abbreviations: Ag, antigen; APC, antigen-presenting cell; CTLA-4, cytotoxic T lymphocyte associated antigen 4; MHC, major histocompatibility complex; TCR, T cell receptor; Treg, regulatory T cell. for binding to CTLA-4, blocking the inhibitory signal that would have arisen from binding to B7 [18]. With no inhibitory signal present, the brake on T-cell activation is released and T-cell proliferation is sustained, thereby potentially promoting an antitumor response (Fig. 3A, 3B) [19]. Two fully human anti CTLA-4 mabs are in clinical development for the treatment of patients with metastatic melanoma as well as other tumor types and have demonstrated antitumor activity as single agents and in combination with other agents: tremelimumab (CP-675,206; Pfizer, Inc., New London, CT), a fully human IgG 2 mab, and ipilimumab (MDX-010; Medarex, Princeton, NJ), a fully human IgG 1 mab. Safety of CTLA-4 Blockade in Patients with Metastatic Melanoma The most commonly reported adverse events (AEs) after anti CTLA-4 mab therapy in patients with advanced melanoma include diarrhea/colitis, dermatitis/rash, pruritus, nausea, vomiting, and fatigue [2, 30, 41 43] (Table 3 [23, 24, 35, 38]). Grade 3 or 4 AEs associated with treatment include diarrhea, dermatitis/rash, fatigue, fever, abdominal pain, nausea, hypophysitis, and hepatitis [2, 30, 34, 42, 44, 45]. When agents are used that enhance patient immunoreactivity, it is expected that some level of reactivity to selfantigens will occur, and most toxicities commonly observed with CTLA-4 blockade are considered immune related AEs (IRAEs) [22, 34, 40, 46, 47]. IRAEs appear to correlate with clinical benefit [30, 48]; however, at this time, it is not known whether the appearance of IRAEs in patients receiving anti CTLA-4 mabs is associated with longer survival. Most IRAEs experienced by patients treated with CTLA-4 blockade are reversible following cessation of treatment [19]. Gastrointestinal toxicities (e.g., diarrhea and colitis) are commonly associated with CTLA-4 blockade [2, 30, 43, 48, 49]. Evidence of neutrophilic and lymphocytic inflammation in gastrointestinal biopsies suggests that these toxicities are IRAEs [48]. In a phase II study (n 155) of patients treated with 10 mg/kg ipilimumab every 3 weeks for four cycles followed by maintenance dosing every 12 weeks, grade 3 or 4 AEs were reported by 21.9% of patients, and the majority of these were gastrointestinal AEs (8.4% of total patients) [36]. In addition, in an analysis of safety data from eight completed and ongoing trials of patients (n 786) who received tremelimumab (15 mg/kg), diarrhea was the most common treatment-related AE (occurring in 40% of patients), and 11% of patients had grade 3 diarrhea [43]. Although cases of colitis have developed into colon perforation in approximately 1% 2% of patients treated with CTLA-4 blockade [34, 48, 49], the majority of cases of diarrhea/colitis resolve fully. Most events are mild to moderate in severity. Severe enterocolitis is usually alleviated by systemic steroid treatment and resolves within approximately 1 2 weeks [19, 45, 49]. In cases refractory to steroids, tumor necrosis factor blockade with infliximab has been effective [48]. Although some studies have reported that systemic steroid administration does not affect the antitumor activity of CTLA-4 blockade [48, 49], a recent study indicated a

4 Robert, Ghiringhelli 851 Table 1. Clinical trials with tremelimumab in patients with metastatic melanoma Study Phase Dose trend toward a shorter median duration of response in responders receiving high-dose systemic steroids (19.3 months versus 30.6 months for all responders) [50]. Furthermore, in a phase II trial investigating prophylactic budesonide concurrent with ipilimumab in 115 patients with advanced melanoma, the rate of grade 2 diarrhea was not lower [38]. Analysis of ongoing trials with larger sample sizes will provide more definitive guidelines for the management of AEs. In studies of tremelimumab and ipilimumab, there have been deaths that appeared to be related to treatment. Two patients in a study of ipilimumab (n 198) in patients with melanoma or renal cell carcinoma developed enterocolitis that led to colonic perforation [48]. One of these patients died from sepsis, and the other chose comfort care because of cancer progression. In a phase II study of patients with melanoma who were treated with tremelimumab (n 246), there were two treatment-related deaths [23]. One was considered sudden death, and one was the result of diverticular perforation. The deaths resulting from colonic perforation emphasize the importance of careful management of gastrointestinal AEs. Patients treated with anti CTLA-4 mabs may experience rash with or without pruritus, and a small percentage of patients have reported grade 3 rash [30, 43, 44]. The cutaneous presentation is often a nonspecific, diffuse maculopapular rash in which pathologic examination may reveal infiltration of CD4 and CD8 T cells [30, 51]. Enrollment (n) Symptomatic treatment with hydroxyzine or diphenhydramine seems to provide relief for some patients [30], but the rash can also resolve spontaneously [2]. Infrequently occurring AEs such as uveitis and hypophysitis may require clinical intervention. Among 163 patients treated with ipilimumab in one study, 5% of patients developed autoimmune hypophysitis [52]. In the cross-study safety analysis of tremelimumab (n 786), the incidence of hypophysitis was 1% [43]. Autoimmune hypophysitis may require steroids and/or hormone therapy [52], and this may not be a reversible condition. Ocular AEs can be resolved with topical corticosteroids [30, 41, 51 53], whereas the symptoms of hypophysitis have resolved with discontinuation of therapy and physiologic hormone replacements [52]. CTLA-4 blockade has also occasionally caused autoimmune thyroiditis, and the outcome of these toxicities has varied. Some cases are manageable and selflimiting, whereas other cases have led to partial or total loss of function requiring long-term hormonal supplementation [2, 30]. Hepatitis [22, 24, 52, 54, 55], which may be an IRAE [47], and nephritis [48] have also been reported in some patients with melanoma treated with anti CTLA-4 mabs. Overall, these toxicities are usually manageable, treatment with anti CTLA-4 mabs is tolerated by patients with metastatic melanoma, and AEs associated with CTLA-4 blockade are generally less severe than those observed with interleukin (IL)-2 or interferon (IFN)-. Further- Objective (CR PR) a related AEs response Grade 3 or 4 treatment- Median survival (mos) Estimated 12-month survival b A [2, 20] I mg/kg 44 4/29 (14%) 6/44 (14%) 21.7 NR A [21, 22, 26] I 3, 6, or 10 mg/kg 29 2/28 (7%) 9/28 (32%) 15.9 b 58% II 10 mg/kg Q1M 44 4/41 (10%) 12/44 (27%) 10.0 b 32% II 15 mg/kg Q3M 46 4/43 (9%) 6/45 (13%) 11.5 b 46% A [23] II 15 mg/kg Q3M /242 (7%) 51/246 (21%) 10.1 b 41% A [24] III 15 mg/kg Q3M (tremelimumab arm) /328 (9%) 105/324 (32%) 11.8 b NR Tremelimumab and MART-1 dendritic cells [27] Tremelimumab and high-dose IFN [25] I II Tremelimumab dose escalation (3, 6, or 10 mg/kg Q1M; 10 or 15 mg/kg Q3M) MART-1 DC 16 4/16 (25%) NR NR NR 15 mg/kg Q3M IFN 16 3/16 (19%) NR NR NR (ongoing) a For the objective response rate, the denominator for A is all randomized patients, whereas the denominator for all other studies is response-evaluable patients. b Survival data calculations were based on number of enrolled patients. Abbreviations: AE, adverse event; CR, complete response; DC, dendritic cell; IFN, interferon; MART-1, melanoma antigen recognized by T cells 1; NR, not reported; PR, partial response; Q1M, every month; Q3M, every 3 months.

5 852 CTLA-4 Monoclonal Antibodies in Metastatic Melanoma Table 2. Clinical trials with ipilimumab in patients with metastatic melanoma Objective response Grade >3 treatmentrelated Median survival Study Phase Dose n (CR PR) AEs (mos) Study 1 [28, 29] I 3 mg/kg 17 2/17 (12%) NR NR Study 2 [28, 30] I/II (a) 3 mg/kg gp100 Q3W 29 4/29 (14%) 14/56 (25%) in NR both arms a (b) 3 mg/kg gp100, then 27 3/27 (11%) NR 1 mg/kg gp100 Q3W Study 3 [28, 31, 32] II (a) 3 mg/kg Q28D 37 2/37 (5%) 7/37 (19%) 11.7 (b) 3 mg/kg Q28D DTIC 35 5/35 (14%) 10/35 (29%) 15.0 Study 4 [28, 33] I/II mg/kg Q3W IL /36 (22%) 5/36 (14%) a NR Study 5 [28, 34] I/II (a) mg/kg on days 1, 34 1/34 (3%) 7/34 (21%) b NR 57, and 85 (b) mg/kg 30 1/30 (3%) 4/30 (13%) b NR (c) 10 mg/kg on days 1, 22, 24 2/23 (9%) 6/24 (25%) b , and 64 Study 6 [35] II (a) 0.3 mg/kg Q3W a 8.6 maintenance (b) 3.0 mg/kg Q3W 72 3/72 (4.2%) 5/72 (7.0%) a 8.6 maintenance (c) 10 mg/kg Q3W 72 8/72 (11.1%) 18/71 (25.4%) a maintenance Study 7 [36, 37] II 10 mg/kg Q3W 4, then 155 9/155 (5.8%) 34/155 (1.9%) 10.2 maintenance Q12W Study 8 [38, 39] II (a) 10 mg/kg Q3W /57 (15.8%) 22/57 (38.6%) a 11.5 c ( maintenance) (b) 10 mg/kg Q3W 4 ( maintenance) budesonide 58 7/58 (12.1%) 24/58 (41.4%) a 15.1 c a These trials only reported immune-related adverse events. b This trial reported grade 3 or 4 treatment-related AEs. c Numbers represent the median overall survival duration in treatment-refractory patients; the median overall survival time in treatment-naive patients was not reached. Abbreviations: AE, adverse event; CR, complete response; DTIC, dacarbazine; gp, glycoprotein; IL, interleukin; NR, not reported; Q12W, every 12 weeks; Q3W, every 3 weeks; Q28D, every 28 days. more, unlike administration of IL-2, which requires intensive hemodynamic monitoring of patients, administration of anti CTLA-4 mabs is possible in a community hospital setting. Efficacy of CTLA-4 Blockade in Patients with Metastatic Melanoma Standard therapy for melanoma with single-agent dacarbazine yields objective responses in approximately 7.5% of patients, and few patients have long-term benefit (durable response rate, 3.6%) [56]. High-dose immunotherapy with the cytokine IL-2 can induce long-term, durable, complete responses (CRs) in a small percentage (6%) of patients [57 59], but it is very poorly tolerated. High-dose IFN- 2a is no more effective than single-agent dacarbazine in patients with malignant melanoma [60]. In phase II trials, the objective response rates of patients with advanced melanoma to IFN- 2a were 8% 22%, but responses were rarely durable [60, 61]. Therefore, treatment options such as anti CTLA-4 mabs that have the potential for improving the prognosis of patients with metastatic melanoma are needed. CTLA-4 blockade is associated with objective responses in patients with metastatic melanoma (Tables 1 and 2). In a phase II trial of tremelimumab (15 mg/kg administered once every 3 months) in patients (n 251) with previously treated, stage III or IV melanoma (Study A ), 7% of patients had an objective response per independent review (16 partial responses [PRs]), and responses lasted days. The median overall survival time was 10.1 months, and the 1-year survival rate was 41% [23]. Several phase II studies of ipilimumab in patients with advanced melanoma have also dem-

6 Robert, Ghiringhelli 853 Table 3. Safety of tremelimumab and ipilimumab in large trials (n 100) Safety of tremelimumab in a phase II study in patients with advanced melanoma (n 246) a 15 mg/kg tremelimumab Q90D (n 246) Any grade Grade >3 Treatment-related AEs occurring in 5% of patients treated with tremelimumab Diarrhea, n (%) 99 (40) 28 (11) Pruritus, n (%) 56 (23) 0 Rash, n (%) 55 (22) 3 (1) Nausea, n (%) 53 (22) 3 (1) Fatigue, n (%) 41 (17) 6 (2) Vomiting, n (%) 36 (15) 3 (1) Anorexia, n (%) 28 (11) 2 (1) Abdominal pain, upper and lower, n (%) 17 (7) 1 ( 1) Headache, n (%) 17 (7) 0 Asthenia, n (%) 14 (6) 1 ( 1) Pyrexia, n (%) 14 (6) 1 ( 1) Weight loss, n (%) 14 (6) 3 (1) Treatment-related deaths, n (%) 2 (0.8) b Safety of tremelimumab in a phase III study in patients with advanced melanoma (interim results, patients evaluable for AEs, n 324) c 15 mg/kg tremelimumab Q90D (n 324) Chemotherapy (n 319) Common AEs, any grade Diarrhea/colitis, % Rash, % Pruritus, % Anorexia, % Fever/chills, % Endocrine AEs (thyroid/pituitary/adrenal), % Nausea, % Vomiting, % Hematologic toxicities, % Fatigue, % Headache, % Arthritis, % Myalgia, % Hepatobiliary disorders, % Hepatitis, % Patients with serious AEs 77 (23.8) 16 (5.0) Patients with grade 5 AEs 4 (1.2) 0 (continued)

7 854 CTLA-4 Monoclonal Antibodies in Metastatic Melanoma Table 3. (Continued) Safety of ipilimumab in a phase II study in patients with melanoma (safety population, n 214) d 10 mg/kg (n 71) 3 mg/kg (n 71) 0.3 mg/kg (n 72) Any grade Grade 3 or 4 Any grade Grade 3 or 4 Any grade Grade 3 or 4 Any IRAEs, % Gastrointestinal IRAEs, % Hepatobiliary IRAEs, % Endocrine IRAEs, % Dermatologic IRAEs, % Bowel perforations, % Treatment-related deaths, % e 0 Safety of ipilimumab with or without prophylactic budesonide in a phase II study in patients with melanoma f 10 mg/kg ipilimumab prophylactic budesonide (n 58) 10 mg/kg ipilimumab placebo (n 57) Any grade Grade 3 or 4 Any grade Grade 3 or 4 Any IRAEs, n (%) 47 (81.0) 24 (41.4) 48 (84.2) 22 (38.6) Skin and s.c. tissue IRAEs, n (%) 35 (60.3) 3 (5.2) 39 (68.4) 0 Rash 25 (43.1) 3 (5.2) 33 (57.9) 0 Pruritus 20 (34.5) 0 20 (35.1) 0 Exfoliative rash 3 (5.2) 0 1 (1.8) 0 Gastrointestinal IRAEs, n (%) 28 (48.3) 14 (24.1) 26 (45.6) 13 (22.8) Diarrhea 26 (44.8) 7 (12.1) 25 (43.9) 10 (17.5) Colitis 7 (12.1) 5 (8.6) 9 (15.8) 7 (12.3) Hepatobiliary IRAEs, n (%) 4 (6.9) 4 (6.9) 7 (12.3) 5 (8.8) Autoimmune hepatitis 4 (6.9) 4 (6.9) 3 (5.3) 3 (5.3) Hyperbilirubinemia (5.3) 1 (1.8) Endocrine IRAEs, n (%) 4 (6.9) 3 (5.2) 6 (10.5) 3 (5.3) Hypopituitarism 4 (6.9) 3 (5.2) 2 (3.5) 2 (3.5) Hypothyroidism (5.3) 1 (1.8) a Adapted from Kirkwood JM, Lorigan P, Hersey P et al. A phase II trial of tremelimumab (CP-675,206) in patients with advanced refractory or relapsed melanoma poster and discussion, abstract Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 3, b These included one sudden death and one diverticular perforation. c Adapted from Ribas A, Hauschild A, Kefford R et al. Phase III, open-label, randomized, comparative study of tremelimumab (CP-675,206) and chemotherapy (temozolomide TMZ or dacarbazine DTIC ) in patients with advanced melanoma oral presentation, abstract LBA9011. Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL. May 30 to June 3, d Adapted from Hamid O, Chin K, Li J et al. Dose effect of ipilimumab in patients with advanced melanoma: Results from a phase II, randomized, dose-ranging study poster and discussion, abstract Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 3, e Death caused by grade 3 respiratory infection possibly related to treatment; patient was a tobacco user with lung metastases. f Adapted from Weber JS, Berman D, Siegel J et al. Safety and efficacy of ipilimumab with or without prophylactic budesonide in treatment-naive and previously treated patients with advanced melanoma oral presentation, abstract Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 3, Abbreviations: AE, adverse event; IRAE, immune-related adverse event; Q90D, every 90 days. onstrated antitumor activity of anti CTLA-4 mabs. In a single-arm, phase II study of ipilimumab in patients (n 155) who had failed IL-2 or chemotherapy, the best overall objective response rate was 6% (9 PRs) [36]. The median overall survival time was months, and the estimated 1-year survival rate was 47% [23, 36].

8 Robert, Ghiringhelli 855 Anti CTLA-4 mabs are also being investigated in ongoing and completed phase III studies. The results of a phase III randomized study of 15 mg/kg tremelimumab every 3 months (n 328) and the physician s choice of chemotherapy (n 327) with either dacarbazine or temozolomide in treatment-naive patients with advanced melanoma were recently reported (A ) [24]. The primary endpoint was overall survival. At the second interim analysis, the trial was halted based on recommendation from the data safety monitoring board because the logrank test statistic (p.729) crossed the prespecified O Brien Fleming boundary for futility (p.473). Although the median survival time was longer (11.76 months) in patients treated with tremelimumab than in patients given chemotherapy (10.71 months), the difference was not statistically significant (hazard ratio for chemotherapy/tremelimumab, 1.04; p.729) [24]. Patients with clinical benefit from tremelimumab treatment are continuing on study, and more mature survival and response data are anticipated. Overall, 7% of patients achieve objective responses following single-agent treatment with anti CTLA-4 mabs, but the critical characteristic of this treatment is that objective responses and disease stabilization with anti CTLA-4 mabs seem to be durable ( 6 months in most patients) [2, 20, 22, 28, 50, 62]. Responses may take as many as 12 weeks or more to develop [63]. Indeed, late-onset objective responses are sometimes preceded by months of stable disease (SD) and have even occurred after disease progression [63]. Such delayed responses may relate to the time required for the immune system to mount an antitumor response. A number of different patterns of responses to CTLA-4 blockade have been observed, including SD with a slow decline in lesion burden, responses in some lesions with progression in others, response in baseline lesions, response after initial increase in tumor burden, and responses in index and new lesions after appearance of new lesions [23, 28, 37, 64]. It is possible that standard response criteria may not adequately capture clinical benefit, and caution must be taken to avoid premature treatment termination of patients who may benefit from continued therapy [37, 64]. Therefore, barring rapid disease progression, it has been proposed that patients should continue to receive anti CTLA-4 mab therapy for at least 12 weeks [28]. This modified response profile implies that the evaluation criteria for treatment efficacy should also be adapted to the quality and delay of responses observed. Nevertheless, it is encouraging that, as seen in Tables 1 and 2, the median survival duration in studies of patients with metastatic melanoma is often longer than expected (median, months in a recent meta-analysis) [65] and may exceed 12 months [34]. Combination Therapy with Anti CTLA-4 mabs Anti CTLA-4 mabs have also been investigated in combination with peptide vaccines [30, 41, 55], dacarbazine [31], or cytokines [25, 33] in patients with metastatic melanoma (Tables 1 and 2). In a phase II study, chemotherapy-naive patients with advanced melanoma were treated every 28 days with 3 mg/kg ipilimumab alone (n 37) or in combination with dacarbazine (n 35) [28, 31, 32]. The overall survival time was longer in patients treated with ipilimumab and dacarbazine than in those treated with ipilimumab alone (15.0 months versus 11.7 months, respectively) [32]. This combination is currently being tested in a large randomized phase III study. Ipilimumab has been tested in combination with immunotherapies such as IL-2 or glycoprotein (gp)100 peptide vaccines [28, 30]. In a phase II trial for patients with metastatic melanoma (n 56) receiving ipilimumab and vaccination with gp100 peptides, seven (13%) patients had an objective response [30]. There was no significant difference in the response rate or toxicity between the two regimens tested (3 mg/kg ipilimumab plus gp100 peptides administered once every 3 weeks compared with a single administration of the combination at these doses followed by maintenance dosing with 1 mg/kg ipilimumab plus gp100 peptides) [30]. Ipilimumab has also been tested in combination with IL-2 therapy [33]. That phase I/II study tested several dose levels of ipilimumab ( mg/kg) administered every 3 weeks in combination with 720,000 IU/kg IL-2 administered every 8 hours. Although eight (22%) patients had an objective response (three CRs, five PRs), this response rate suggested an additive, but not synergistic, antitumor effect of CTLA-4 blockade plus IL-2 [19, 33]. Tremelimumab has also been studied in combination with other immunotherapeutic agents. In a phase I trial, patients (n 16) with metastatic melanoma received 3 10 mg/kg tremelimumab monthly or mg/kg tremelimumab quarterly in combination with an intradermal administration of autologous cells pulsed with melanoma antigen recognized by T cells (MART) peptide. There were four objective responses (one CR, three PRs), and all responses were durable [27]. In a phase II trial in patients (n 16 to date) with recurrent, inoperable stage III or IV melanoma, tremelimumab (15 mg/kg quarterly) plus high-dose IFN- 2b was associated with a 19% objective response rate (three PRs lasting 5.0, 8.0, and 9.0 months), and six additional patients achieved SD (lasting months) [25]. Ongoing clinical trials are evaluat-

9 856 CTLA-4 Monoclonal Antibodies in Metastatic Melanoma ing the combination of other agents (e.g., Toll-like receptor 9 agonists) with anti CTLA-4 mabs. Mechanism of Action: T Cells One of the major issues that has hindered our understanding of CD28 CTLA-4 signaling is understanding the exact nature of its underlying mechanism of action. CTLA-4 may compete with CD28 for B7 ligation [12, 66]. Thus, in situations in which CTLA-4 is highly expressed, it is likely that B7.1 or B7.2 will bind preferentially to CTLA-4 and thereby deprive T cells of CD28 costimulatory signaling (Fig. 3A). CTLA-4 may also transduce an inhibitory signal in T cells by removing TCR signaling components, such as the chain of the TCR, from lipid rafts [67]. Recent studies have indicated that CTLA-4 blockade is associated with decreases in Treg-mediated immune suppression [12, 13], suggesting that the T-cell activation observed with anti CTLA-4 mabs may occur, in part, because Tregs no longer modulate dendritic cell (DC) inactivation and T-cell downregulation [13] (Fig. 3B). Tregs expressing CTLA-4 might inhibit T-cell activation by altering the physical interactions between T cells and DCs [68]. Moreover, CTLA-4 can be expressed on the surface of melanoma cells [69], and it is not yet known whether there is a direct effect of the antibodies on the melanoma cells or whether CTLA-4 expression on the target cells could alter drug effects. Most studies of immune responses after cancer immunotherapy have been performed on patient peripheral blood samples. Immunoassays allow quantitative assessment of the phenotype of immune effector cells in peripheral blood, their ability to bind to defined major histocompatibility complex-peptide determinants, and their functional responses on exposure to antigen [70 72]. The memory T- cell pool is increased after therapy with either ipilimumab [30, 55] or tremelimumab [73], as demonstrated by the increase in number of CD45RO T cells. Both antibodies were also shown to increase expression of the activation marker human leukocyte antigen (HLA)-DR on the surface of T cells, and an increase in the number of activated T cells has been observed [30, 55, 73]. However, in several studies of peripheral blood samples from patients treated with anti CTLA-4 mabs, expansion of tumor antigen-specific T cells was not observed [26, 33, 55, 74 76]. Tregs are more difficult to study at the cellular level because they have a surface phenotype that is indistinguishable from chronically activated helper T cells. Positive identification is possible by detection of intracellular expression of the Treg-specific transcription factor FoxP3 [77, 78]. No major modifications in the number or function of Tregs were noted [26, 75]. In a cohort of 10 patients treated with tremelimumab, there was no decrease in the number or function of Tregs, but T cells became resistant to the immunosuppressive effect of Tregs after treatment [73]. The mechanism underlying this acquired Treg unresponsiveness remains to be elucidated. However, studies performed on peripheral blood might not reflect the biologic effect of CTLA-4 blockade on the tumor-associated immune system, and analysis of tumor biopsies may provide a better indication of the role of CTLA-4 blockade on T cells and of their action on metastases. Analyses of tumor biopsies have been undertaken in a few patients treated with CTLA-4 blocking antibodies, and these studies have revealed marked intratumoral changes and the presence of inflammatory infiltrates [2, 51, 76, 79]. CD4 and CD8 T-cell infiltrates have been identified in tumor biopsies [2, 51, 76, 79]. In a study of peripheral blood and tumor tissues from patients with bladder cancer who were treated with CTLA-4 blockade, consistently higher IFN-secreting CD4 ICOS hi T cells and a greater ratio of effector T cells to Treg cells in treated patients than in untreated healthy volunteers were identified [80]. Although consistent association of infiltration of a particular immune cell type and clinical benefits from CTLA-4 blockade has been a challenging goal, a study in a subset of patients (n 7) with melanoma treated with tremelimumab in a phase I/II study found an association between antitumor effects and the presence of infiltrating CD8 T cells in tumor biopsies [22, 79]. Remaining Questions Biomarkers of Efficacy One concern for clinicians when treating their patients with an anti CTLA-4 mab is the lack of a commonly used biomarker, other than tumor size, to indicate potential efficacy. A number of cytokines and chemokines have been assessed in treated patient sera, but none has been found to be consistently correlated (from patient to patient and from trial to trial) with objective response. There have also been conflicting reports regarding the association of IRAEs and clinical responses [30, 81]. The small number of objective responses do not currently allow for definitive conclusions. Administration of CTLA-4 blocking antibodies to patients with melanoma does not result in sustained expansion of circulating melanoma antigen specific CD8 T cells [30, 55, 75, 76]. Markers of T-cell activation (HLA-DR) and memory phenotype (CD45RO) after dosing with tremelimumab have been shown to segregate patients with clinical benefit (n 3) from nonresponders (n 9) [26]. In that study, tremelimumab did not increase the number or function of antigen-specific CD8 T cells in peripheral blood nor decrease FoxP3 transcripts but appeared to gen-

10 Robert, Ghiringhelli 857 erally enhance T-cell activation and differentiation. In our experience, observed increases in HLA-DR and amplification of the T-cell memory pool did not correlate with clinical benefit [73].Therefore, it is unlikely that detection of T-cell activation and memory markers may be useful as a readout of efficacy. Further translational immunological studies on larger cohorts of patients are necessary to determine whether resistance to the immunosuppressive effects of T cells is associated with clinical response [73] and to identify other, more convenient biological markers of efficacy. In a recent report, immunologic monitoring was performed on patients with melanoma who had been treated with ipilimumab (n 15) [82]. Eight of those patients had evidence of clinical benefit, and seven did not respond. Five of the eight patients who responded to ipilimumab were seropositive for NY-ESO-1 (anti-cancer testis antigen 1B) and had CD4 and CD8 T-cell responses specific to NY- ESO-1 following treatment, whereas the nonresponders were seronegative (one nonresponder did have a CD4 T- cell response to NY-ESO-1) [82]. The authors suggested that these data might provide a rationale for combination therapy with CTLA-4 blockade and NY-ESO-1 vaccination; however, further confirmation in larger patient cohorts is needed. Side Effects: Association with Tumor Response, Prognostic Factors Several studies with CTLA-4 blockade have suggested a correlation between antitumor effects and autoimmune phenomena such as thyroiditis, hypophysitis, enteritis, hepatitis, diarrhea/colitis, and rash [30, 41, 55, 83]. The incidence of IRAEs has been associated with antitumor activity in several clinical trials. For example, Attia and colleagues found that five of 14 (36%) patients with metastatic melanoma who experienced grade 3 or 4 autoimmune toxicity experienced an objective response, compared with two (5%) responses among the 42 patients with no IRAE (p.008) after treatment with ipilimumab and gp100 peptides [30]. Beck and colleagues also reported a significant difference in the objective response rate between patients with enterocolitis and patients without enterocolitis among 137 melanoma patients treated with ipilimumab and gp100 peptides [48]. However, these reports may have introduced bias because responding patients may remain on treatment with a longer period of exposure and have a higher possibility of developing an IRAE than patients who progress or die early, and this association between side effects and antitumor efficacy needs to be confirmed in larger prospective studies. There is presently no known means to predict the incidence of an AE or to exclude a population at high risk of developing a serious AE; however, patients with inflammatory bowel disease are thought to be at a higher risk for gastrointestinal problems and should be excluded from treatment. Improving our knowledge of the mechanisms underlying these AEs may help to achieve this objective, and several ongoing clinical studies of tremelimumab and ipilimumab are further investigating mechanisms, prevention, and management of drug-induced toxicities. Dose Level and Administration Schedule Another aspect of clinical testing of anti CTLA-4 mabs is the determination of an optimized dose and administration schedule. Although the study was not powered for a direct comparison, single-agent tremelimumab at a dose of 15 mg/kg every 3 months was associated with a lower incidence of grade 3 or 4 treatment-related AEs than 10 mg/kg tremelimumab administered monthly (13% versus 27%) in the phase I/II trial; this difference was not statistically significant, but the 15-mg/kg dose administered every 3 months regimen was used in subsequent clinical studies [22 24]. Conserved efficacy with a longer interval between doses may be related to the relatively long plasma half-life of tremelimumab (22 days) [2]. Ipilimumab, which has a plasma half-life of days [34, 84], has been administered at concentrations of mg/kg with a variety of dosing schedules (Table 2). The presently accepted treatment regimen is 10 mg/kg administered once every 3 4 weeks. A recent report on a phase II study of ipilimumab confirmed that, among patients treated with 0.3, 3, and 10 mg/kg, there was a statistically significant trend indicating a higher best objective response rate with a higher dose (p.0015). Patients in the 10-mg/kg ipilimumab dose cohort also had a longer median overall survival time than patients in the other cohorts; however, the rates of IRAEs were also highest in the 10-mg/kg cohort [35]. Both anti CTLA-4 mabs are being tested in combination with other anticancer therapies, and these trials use roughly the same schedules and dose levels as the singleagent trials. As new combinations of agents with anti CTLA-4 mabs are tested, more consideration must be placed on the administered dose and schedule. For example, sequential combinations may be more appropriate with chemotherapy, which could reduce the tumor burden and increase the probability of antitumor activity with subsequent CTLA-4 blockade immunotherapy. However, the classical dose-escalation designs used for conventional chemotherapies may not be adaptable for anti CTLA-4 immunotherapy, and because we do not have reliable biologic markers of activity, we must admit that the choice of dose level and administration schedule remains

11 858 CTLA-4 Monoclonal Antibodies in Metastatic Melanoma Table 4. Proposed studies of anti CTLA-4 mabs in the adjuvant setting Trial overview Patients Treatment EORTC 18071: phase III double-blind, Patients with stage III, macroscopic N-positive Ipilimumab or placebo placebo-controlled, randomized trial (nodal involvement) disease following complete resection Intergroup E1607: phase III trial Following surgical resection, patients with T Tremelimumab or placebo (any) N2 postinterferon or any resectable M1a or M1b will be enrolled SWOG trial Patients with stage IIB III melanoma Patients treated with high-dose interferon will be assessed at 3 months; in patients without manifestations of autoimmunity, an anti CTLA-4 mab will be added to therapy Abbreviations: CTLA-4, cytotoxic T lymphocyte associated antigen 4; EORTC, European Organization for Research and Treatment of Cancer; mab, monoclonal antibody; SWOG, Southwest Oncology Group. somehow empirical. Until reliable biologic or clinical markers of activity are identified, our ongoing awareness of the most recent clinical experience and success of various therapies will aid in the selection of rational combinations with the highest likelihood of antitumor activity. CONCLUSIONS CTLA-4 blockade has been associated with rare, but impressive and durable, objective responses in patients with metastatic melanoma. Even if the immediate objective response rates obtained with anti CTLA-4 mabs do not seem to be significantly higher than those observed with conventional chemotherapy or high-dose IL-2, the high frequency of durable responses is promising. This novel immunotherapeutic approach may also generate a T-cell memory antitumor response, potentially increasing long-term survival. Furthermore, CTLA-4 blockade is associated with a more favorable toxicity profile than high-dose IL-2. Anti CTLA-4 mabs are also being investigated as adjuvant therapy for patients with melanoma (Table 4). These studies will determine if this early approach to overcome tumorinduced immune tolerance can improve clinical outcomes for patients with melanoma. Altogether, anti CTLA-4 mabs appear to be very promising new therapeutic agents for melanoma. The relatively low objective response rate should not be regarded as a failure, but rather as an encouragement to develop clinical and translational research to understand the exact mechanisms underlying both the biologic antitumor activity of anti CTLA-4 mabs and the IRAEs associated with these drugs, to identify reliable markers of activity, and to potentially allow selection of a population of patients with a high probability of response and a low risk for severe AEs. AUTHOR CONTRIBUTIONS Conception/Design: Caroline Robert Data analysis: Caroline Robert Manuscript writing: Caroline Robert, Francois Ghiringhelli Final approval of manuscript: Caroline Robert, Francois Ghiringhelli The authors take full responsibility for the content of the paper, but thank Tamara Fink, Ph.D., of ProEd Communications, Inc. for her assistance in collating the comments of the authors and organizing the published literature. REFERENCES 1 Dunn GP, Old LJ, Schreiber RD. The immunobiology of cancer immunosurveillance and immunoediting. Immunity 2004;21: 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: Alegre ML, Frauwirth KA, Thompson CB. T-cell regulation by CD28 and CTLA-4. Nat Rev Immunol 2001;1: Brunet JF, Denizot F, Luciani MF et al. A new member of the immunoglobulin superfamily CTLA-4. Nature 1987;328: 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: Chen L. Co-inhibitory molecules of the B7-CD28 family in the control of T-cell immunity. Nat Rev Immunol 2004;4: Alegre ML, Shiels H, Thompson CB et al. Expression and function of CTLA-4 in Th1 and Th2 cells. J Immunol 1998;161: Egen JG, Allison JP. Cytotoxic T lymphocyte antigen-4 accumulation in the immunological synapse is regulated by TCR signal strength. Immunity 2002;16: Egen JG, Kuhns MS, Allison JP. CTLA-4: New insights into its biological function and use in tumor immunotherapy. Nat Immunol 2002;3: 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:

12 Robert, Ghiringhelli Grohmann U, Orabona C, Fallarino F et al. CTLA-4-Ig regulates tryptophan catabolism in vivo. Nat Immunol 2002;3: Read S, Greenwald R, Izcue A et al. Blockade of CTLA-4 on CD4 CD25 regulatory T cells abrogates their function in vivo. J Immunol 2006;177: Wing K, Onishi Y, Prieto-Martin P et al. CTLA-4 control over Foxp3 regulatory T cell function. Science 2008;322: Khattri R, Auger JA, Griffin MD et al. Lymphoproliferative disorder in CTLA-4 knockout mice is characterized by CD28-regulated activation of Th2 responses. J Immunol 1999;162: 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: Waterhouse P, Penninger JM, Timms E et al. Lymphoproliferative disorders with early lethality in mice deficient in Ctla-4. Science 1995;270: Leach DR, Krummel MF, Allison JP. Enhancement of antitumor immunity by CTLA-4 blockade. Science 1996;271: Krummel MF, Allison JP. CD28 and CTLA-4 have opposing effects on the response of T cells to stimulation. J Exp Med 1995;182: Langer LF, Clay TM, Morse MA. Update on anti-ctla-4 antibodies in clinical trials. Expert Opin Biol Ther 2007;7: Bulanhagui C, Ribas A, Pavlov D et al. Phase 1 clinical trials of CP- 675,206: Tumor responses are sufficient but not necessary for prolonged survival [poster, abstract 8036]. J Clin Oncol 2006;24(18 suppl):461s. 21 Gomez-Navarro J, Antonia S, Sosman J et al. Survival of patients (pts) with metastatic melanoma treated with the anti-ctla4 monoclonal antibody (mab) CP-675,206 in a phase I/II study [poster, abstract 8524]. J Clin Oncol 2007;25(18 suppl):478s. 22 Camacho LH, Antonia S, Sosman J et al. Phase I/II trial of tremelimumab in patients with metastatic melanoma. J Clin Oncol 2009;27: Kirkwood JM, Lorigan P, Hersey P et al. A phase II trial of tremelimumab (CP-675,206) in patients with advanced refractory or relapsed melanoma [poster and discussion, abstract 9023]. Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 3, Ribas A, Hauschild A, Kefford R et al. Phase III, open-label, randomized, comparative study of tremelimumab (CP-675,206) and chemotherapy (temozolomide [TMZ] or dacarbazine [DTIC]) in patients with advanced melanoma [oral presentation, abstract LBA9011]. Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL. May 30 to June 3, Tarhini AA, Moschos SS, Schlesselman JJ et al. Phase II trial of combination biotherapy of high-dose interferon alfa-2b and tremelimumab for recurrent inoperable stage III or stage IV melanoma [oral presentation, abstract 9009]. Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 3, Comin-Anduix B, Lee Y, Jalil J et al. Detailed analysis of immunologic effects of the cytotoxic T lymphocyte-associated antigen 4-blocking monoclonal antibody tremelimumab in peripheral blood of patients with melanoma. J Transl Med 2008;6: Ribas A, Comin-Anduix B, Jalil J et al. Combination of dendritic cell (DC) vaccination with CTLA4 blockade in patients (pts) with metastatic melanoma: A phase 1 clinical trial [oral presentation, abstract 2537]. Presented at the American Association for Cancer Research Annual Meeting, San Diego, CA, April 12 16, Hamid O, Urba WJ, Yellin M et al. Kinetics of response to ipilimumab (MDX-010) in patients with stage III/IV melanoma [poster, abstract 8525]. J Clin Oncol 2007;25(18 suppl):478s. 29 Tchekmedyian S, Glasby J, Korman A et al. MDX-010 (human anti- CTLA4): A phase I trial in malignant melanoma [poster, abstract 56]. Proc Am Soc Clin Oncol 2002;21:15a. 30 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: Fishchkoff SA, Hersh E, Weber J et al. Durable responses and long-term progression-free survival observed in a phase II study of MDX-010 alone or in combination with dacarbazine (DTIC) in metastatic melanoma [poster and discussion, abstract 7525]. Presented at the 41st Annual Meeting of the American Society of Clinical Oncology, Orlando, FL, May 13 17, Hersh EM, Weber JS, Powderly JD et al. Disease control and long-term survival in chemotherapy-naive patients with advanced melanoma treated with ipilimumab (MDX- 010) with or without dacarbazine [poster and discussion, abstract 9022]. Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 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: Weber JS, O Day S, Urba W et al. Phase I/II study of ipilimumab for patients with metastatic melanoma. J Clin Oncol 2008;26: Hamid O, Chin K, Li J et al. Dose effect of ipilimumab in patients with advanced melanoma: Results from a phase II, randomized, dose-ranging study [poster and discussion, abstract 9025]. Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 3, O Day SJ, Ibrahim R, DePril V et al. Efficacy and safety of ipilimumab induction and maintenance dosing in patients with advanced melanoma who progressed on one or more prior therapies [poster and discussion, abstract 9021]. Presented at: 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 3, Wolchok JD, Ibrahim R, DePril V et al. Antitumor response and new lesions in advanced melanoma patients on ipilimumab treatment [poster, abstract 3020]. Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 3, Weber JS, Berman D, Siegel J et al. Safety and efficacy of ipilimumab with or without prophylactic budesonide in treatment-naive and previously treated patients with advanced melanoma [oral presentation, abstract 9010]. Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 3, Thompson JA, Berman D, Siegal J et al. Effect of prior treatment status on the efficacy and safety of ipilimumab monotherapy in treatment-naive and previously treated patients with advanced melanoma [poster, abstract 9055]. Presented at the 44th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 30 to June 3, Weber J. Review: Anti-CTLA-4 antibody ipilimumab: Case studies of clinical response and immune-related adverse events. The Oncologist 2007;12: 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: Chung KY, Gore I, Fong L et al. A phase II study of the anti-ctla4 monoclonal antibody (mab), CP-675,206, in patients with refractory metastatic adenocarcinoma of the colon or rectum [poster, abstract 3035]. J Clin Oncol 2007;25(18 suppl):118s.