Targeting Cytotoxic T-lymphocyte Antigen-4 Research Articles

Antitumor activity of Z15-0-2, a bispecific nanobody targeting PD-1 and CTLA-4

The combination of programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA-4) antibodies has potential for enhancing clinical efficacy. We described the development and antitumor activity of Z15-0, a bispecific nanobody targeting both the PD-1 and CTLA-4 pathways simultaneously. We designed and optimized the mRNA sequence encoding Z15-0, referred to as Z15-0-2 and through a series of in vitro and in vivo experiments, we established that the optimized Z15-0-2 mRNA sequence significantly increased the expression of the bispecific nanobody. Administration of Z15-0-2 mRNA to tumor-bearing mice led to greater inhibition of tumor growth compared to controls. In aggregate, we introduced a novel bispecific nanobody and have re-engineered it to boost expression of mRNA, representing a new drug development paradigm.

Management Strategies of Juvenile Idiopathic Arthritis-Associated Chronic Anterior Uveitis: Current Perspectives.

Juvenile idiopathic arthritis (JIA) is the most common extraocular disease associated with pediatric uveitis. Despite the growing knowledge about the pathogenetic and clinical characteristics of the disease, it still remains a challenge for both the pediatric rheumatologist and ophthalmologist. Since uveitis is asymptomatic in most cases, it is generally detected by parents in a late phase of the disease when complications have occurred with consequent severe vision loss. Improvement in attentive screening and early treatment initiation to suppress inflammation has considerably reduced the sight-threatening outcomes of JIA-associated chronic anterior uveitis (JIA-CAU). Initial treatment with topical steroids is effective in most cases. However, more severe cases require the use of periocular or systemic corticosteroids, possibly leading to long-term complications. These include growth retardation, cataract and glaucoma. Systemic immunosuppressive agents are then employed in patients resistant to first-line therapy or to reduce steroid-associated complications. In this review, we will discuss the immunosuppressant agents currently employed for the treatment of the disease, including anti-tumor necrosis factor (TNF)α biologics approved or not by the regulatory agencies. We will also highlight how new therapeutic options like biologic targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4) co-stimulatory molecule, interleukin-6 receptor (IL-6R) or B lymphocytes might represent exciting new options for patients resistant to conventional therapy. Finally, the potential use of janus kinase (JAK) inhibitors recently approved for the treatment of several inflammatory rheumatic diseases in adults will be also discussed.

Simultaneously Combined Cancer Cell- and CTLA4-Targeted NIR-PIT Causes a Synergistic Treatment Effect in Syngeneic Mouse Models.

Near-infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that utilizes antibody-IRDye700DX (IR700) conjugates. The clinical use of NIR-PIT has recently been approved in Japan for patients with inoperable head and neck cancer targeting human epidermal growth factor receptor (hEGFR). Previously, cytotoxic T-lymphocyte antigen 4 (CTLA4)-targeted NIR-PIT has been shown to strongly inhibit tumor progression and prolonged survival was seen in different tumor models due to enhanced T-cell-mediated antitumor immunity. In this study, combined NIR-PIT targeting CTLA4 expressing cells and cancer cells was investigated in four tumor models including a newly established hEGFR-expressing murine oropharyngeal cancer cell (mEERL-hEGFR). While single molecule-targeted therapy (NIR-PIT targeting hEGFR or CTLA4) did not inhibit tumor progression in poorly immunogenic mEERL-hEGFR tumor, dual (CTLA4/hEGFR)-targeted NIR-PIT significantly suppressed tumor growth and prolonged survival resulting in a 38% complete response rate. After the dual-targeted NIR-PIT, depletion of CTLA4 expressing cells, which were mainly regulatory T cells (Tregs), and an increase in the CD8+/Treg ratio in the tumor bed were observed, suggesting enhanced host antitumor immunity. Furthermore, dual-targeted NIR-PIT showed antitumor immunity in distant untreated tumors of the same type. Thus, simultaneous cancer cell-targeted NIR-PIT and CTLA4-targeted NIR-PIT is a promising new cancer therapy strategy, especially in poorly immunogenic tumors where NIR-PIT monotherapy is suboptimal.

Comprehensive Evaluation of Immune-Checkpoint DNA Cancer Vaccines in a Rat Cholangiocarcinoma Model.

Cholangiocarcinoma (CCA) is a malignant tumor with aggressive biological behavior. Immune checkpoints such as cytotoxic T-lymphocyte antigen 4 (CTLA4) and antiprogrammed death 1 (PD-1) are critical immune-checkpoint molecules that repress T-cell activation. The DNA vaccine potential against CTLA4 and PD-1 in CCA is unknown. We used a thioacetamide (TAA)-induced intrahepatic cholangiocarcinoma (iCCA) rat model to investigate the DNA vaccine potential against CTLA4, PD-1, and PD-L1. We detected PD-L1 expression in CCA and CD8+ T-cell infiltration during CCA progression in rats. We validated antibody production, carcinogenesis, and CD8+ T-cell infiltration in rats receiving DNA vaccination against PD-1, PD-L1, or CTLA4. In our TAA-induced iCCA rat model, the expression of PD-L1 and the infiltration of CD8+ T cells increased as in rat CCA tumorigenesis. PD-1 antibodies in rats were not increased after receiving PD-1 DNA vaccination, and CCA tumor growth was not suppressed. However, in rats receiving PD-L1–CTLA4 DNA vaccination, CCA tumor growth was inhibited, and the antibodies of PD-L1 and CTLA4 were produced. Furthermore, the number of CD8+ T cells was enhanced after PD-L1–CTLA4 DNA vaccination. DNA vaccination targeting CTLA4–PD-L1 triggered the production of specific antibodies and suppressed tumor growth in TAA-induced iCCA rats.

Abstract 2220: Non-clinical tumor models reveal broad combination potential of ICOS agonist antibodies

Abstract Unprecedented rates of durable clinical responses have been observed for antibody-based therapeutics targeting immune checkpoint proteins such as cytotoxic T lymphocyte antigen-4 (CTLA-4) or programmed death receptor-1 (PD-1). Nonetheless, a significant number of patients fail to respond, highlighting the need for alternative and complementary immunotherapeutic interventions for cancer. Inducible T-cell costimulator (ICOS/CD278) is a CD28 superfamily receptor that is predominantly expressed on effector and cytotoxic T cells shortly after T cell receptor (TCR) activation. In addition to promotion of T cell and B cell collaboration, ICOS signaling (via ICOS ligand [ICOSL] or antibody-based crosslinking) has been shown to improve T cell antitumor activity, survival, durable tumor rejection. To support the clinical development of GSK3359609 (a hIgG4 ICOS agonist antibody) several in vivo combination studies were conducted using a tool anti-mouse ICOS agonist antibody (clone 7E.17G9). Analogous with the Fc-based characteristics of a human IgG4 antibody, the anti-mouse ICOS tool antibody exhibited significant antitumor activity when grafted on a murine IgG1 (or Fc-reduced) backbone. Using an in vivo models of breast cancer (EMT6, BALB/c), the murinized ICOS tool antibody demonstrated potent antitumor activity alone (tumor growth inhibition [TGI] of 40-60%) in combination with immune checkpoint inhibitors (ICI) targeting PD-1 and CTLA-4 (TGI of 100% and 90%, respectively). Antitumor activity was associated with increased total T cell infiltration into the tumor, a higher tumor CD8/Treg cell ratio, and broad increases in T cell activation markers (e.g. CD25, CD69, Granzyme B, perforin, and PD-1). The cancer immunity cycle posits that multiple points of intervention exist for cancer immunotherapy, many of which should be considered in order to identify complementary therapeutic strategies. With this in mind, and consistent with ICI, antitumor activity was observed in combination with innate immune modulators (e.g. TLR4 agonist) and chemo/cytotoxic (e.g. carboplatin and paclitaxel) therapies in different syngeneic tumor models. Altogether these data underscore the broad utility of ICOS agonist antibodies as a reliable combination partner for cancer immunotherapy. Citation Format: Jeremy D. Waight, Meixia Bi, David Kilian, Christopher Hopson, Shu-Yun Zhang, Sara Brett, Sapna Yadavilli, Tianqian Zhang, Hong Shi, Kenneth W. Hance, Marc Ballas, Axel Hoos. Non-clinical tumor models reveal broad combination potential of ICOS agonist antibodies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2220.

Isolation of Two Novel Human Anti-CTLA-4 mAbs with Intriguing Biological Properties on Tumor and NK Cells.

The cytotoxic T lymphocyte-antigen 4 (CTLA-4) has been considered an IC exclusively expressed on T cells, where it counteracts the co-stimulatory CD28 receptor, by competing for its binding to CD-80 and CD-86. We recently found that it is expressed also on tumor and NK cells, suggesting other possible unknown roles of CTLA-4. To shed light on these novel aspects of CTLA-4, we used Ipilimumab, the first FDA approved human antibody targeting CTLA-4, in parallel studies with two novel human mAbs we isolated by using an efficient phage display selection strategy on live activated lymphocytes and purified mouse and human CTLA-4. The selection for cross-reactive mAbs was guaranteed by a high throughput sequencing to identify the sequences commonly enriched by two parallel pannings on human and mouse CTLA-4. Two isolated antibodies were found to bind with high affinity to both human and mouse CTLA-4 and lymphocytes, showing nanomolar or sub-nanomolar Kd values. They were able to kill Treg cells by ADCC, and to activate both human and mouse PBMCs, by strongly increasing cytokines secretion. Interestingly, they activated NK cells, exhibited cytotoxicity against cancer cells by inducing ADCC and inhibited tumor cell growth by affecting CTLA-4 downstream pathways in a similar fashion to CD-80 and CD-86 ligands and differently from Ipilimumab. Moreover, the novel mAbs showed a reduced ability to interfere in the binding of CD-80 ligands to CTLA-4 on T cells with respect to Ipilimumab, suggesting that they could allow for anti-tumor effects without the irAEs associated with the potent antagonistic activity of Ipilimumab.

Cytotoxic T lymphocyte antigen-4 (CTLA-4) expression in chordoma and tumor-infiltrating lymphocytes (TILs) predicts prognosis of spinal chordoma.

Chordoma is a rare tumor of the skeletal system that is characterized by a high recurrence rate and treatment resistance. Given the common finding of immune dysregulation in chordoma, immunotherapy has emerged as potential treatment option. As an important immune checkpoint regulator, we evaluated cytotoxic T-lymphocyte antigen-4 (CTLA-4) expression and its prognostic significance for patients with chordoma of the spine. CTLA-4 expression was analyzed immunohistochemically in 32 chordoma tissues and 14 nucleus pulposus tissues to examine the specificity of CTLA-4 expression in chordoma. Univariate log-rank analysis was used to evaluate the association of CTLA-4 expression in tumor cells and tumor-infiltrating lymphocytes (TILs) with survival. Cox multivariate analysis was used to identify independent factors of survival. Positive CTLA-4 expression was observed in all of the TILs and tumor cell cytoplasm, and partial in the membrane or in both the membrane and nucleus, with a markedly higher positivity rate than that observed in normal nucleus tissues. Higher CTLA-4 expression in the tumor but not in TILs was significantly associated with shorter continuous disease-free survival (CDFS) and overall survival (OS). CTLA-4 expression in tumor cells and TILs were independent predictors for CDFS, whereas only tumor cell expression was a significant predictor of OS. Furthermore, the combination of CTLA-4 expression in the tumor and TILs had higher prognostic value. Targeting CTLA-4 may be a potential novel therapeutic strategy for chordoma patients.

SUN-923 Combination Immune Checkpoint Inhibitor Therapy for ACTH-Secreting Pituitary Carcinoma

IntroductionPituitary carcinoma is a rare yet serious entity with poor prognosis despite multimodal therapies. Cerebrospinal and/or systemic metastases are present by definition, making adjuvant systemic therapy necessary. Novel treatments are urgently needed for refractory cases. Immunotherapy with immune checkpoint inhibitors (ICI) targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4), programmed cell death 1 (PD-1) or its ligand (PD-L1) has been a revolution in multiple malignancies. The expression of CTLA-4 and PD-L1 has been elucidated in pituitary adenomas and could be implicated in pituitary carcinomas as well. Hypophysitis is also a frequent endocrine immune-related adverse event, especially during CTLA-4 blockade (with ipilimumab) or combination ICI. However, the efficacy of ICI in the treatment of refractory pituitary tumors has yet to be established. In 2018, Lin et al. successfully treated a first case of a hypermutated aggressive ACTH-secreting pituitary carcinoma with ipilimumab (anti-CTLA-4) and nivolumab (anti-PD-1) combination immunotherapy.Clinical CaseWe report a 40-year old male, diagnosed with an invasive ACTH-secreting pituitary macroadenoma in 2012, initially treated by transsphenoidal and transcranial surgery, followed by adjuvant stereotactic radiotherapy and several courses of ketoconazole. In 2017, he presented to our clinic for a recurrent Cushing’s phenotype despite maximal dosing of ketoconazole. Therapy both with pasireotide and cabergoline was unable to normalize cortisol levels and a bilateral (subtotal) adrenalectomy was performed. In June 2018, he presented to our emergency department with acute diplopia due to a left abducens nerve palsy. Imaging revealed recurrent invasion of the tumor into the sella turcica and cavernous sinus, together with cerebellar and drop metastases at the cervical spine. Temozolomide (TMZ) was initiated for a total of 9 cycles. Progressive disease was observed with development of new onset right oculomotor nerve palsy after the last TMZ cycle, and persistence of elevated serum ACTH-cortisol and urinary cortisol levels, despite the absence of radiological progression. Therefore, he was started in a compassionate use setting with a combination ICI therapy with ipilimumab 3 mg/kg and nivolumab 1 mg/kg (for 4 cycles), followed by maintenance nivolumab therapy (240 mg) every two weeks. He has stable disease (both radiographically and hormonally) five months after the initiation of the immunotherapy.Clinical Lesson(s) or Conclusion(s)We report the second case of ACTH-secreting pituitary carcinoma treated with combination ICI therapy. The disease status of the patient is stable up until now, suggesting at least disease control by the immunotherapy. Checkpoint blockade inhibitors are a promising novel treatment modality for refractory pituitary tumors and should be further studied.

Immune Checkpoint Inhibitor Therapy in Patients With Preexisting Inflammatory Bowel Disease.

PURPOSEThe risk of immune checkpoint inhibitor therapy–related GI adverse events in patients with cancer and inflammatory bowel disease (IBD) has not been well described. We characterized GI adverse events in patients with underlying IBD who received immune checkpoint inhibitors.PATIENTS AND METHODSWe performed a multicenter, retrospective study of patients with documented IBD who received immune checkpoint inhibitor therapy between January 2010 and February 2019. Backward selection and multivariate logistic regression were conducted to assess risk of GI adverse events.RESULTSOf the 102 included patients, 17 received therapy targeting cytotoxic T-lymphocyte antigen-4, and 85 received monotherapy targeting programmed cell death 1 or its ligand. Half of the patients had Crohn’s disease, and half had ulcerative colitis. The median time from last active IBD episode to immunotherapy initiation was 5 years (interquartile range, 3-12 years). Forty-three patients were not receiving treatment of IBD. GI adverse events occurred in 42 patients (41%) after a median of 62 days (interquartile range, 33-123 days), a rate higher than that among similar patients without underlying IBD who were treated at centers participating in the study (11%; P < .001). GI events among patients with IBD included grade 3 or 4 diarrhea in 21 patients (21%). Four patients experienced colonic perforation, 2 of whom required surgery. No GI adverse event–related deaths were recorded. Anti–cytotoxic T-lymphocyte antigen-4 therapy was associated with increased risk of GI adverse events on univariable but not multivariable analysis (odds ratio, 3.19; 95% CI, 1.8 to 9.48; P = .037; and odds ratio, 4.72; 95% CI, 0.95 to 23.53; P = .058, respectively).CONCLUSIONPreexisting IBD increases the risk of severe GI adverse events in patients treated with immune checkpoint inhibitors.

775 Immune Checkpoint Inhibitor Therapy in Patients With Preexisting Inflammatory Bowel Disease

INTRODUCTION: We characterized gastrointestinal adverse events in patients with underlying inflammatory bowel disease (IBD) who received immune checkpoint inhibitors. METHODS: We performed a fourteen-center, retrospective study of patients with documented IBD who received immune checkpoint inhibitor therapy between January 2010 and February 2019. Backward selection and multivariate logistic regression were conducted to assess risk of gastrointestinal adverse events. RESULTS: Of the 102 included patients, 17 received therapy targeting cytotoxic T-lymphocyte antigen-4 and 85 received monotherapy targeting programmed death-1 or its ligand. Half the patients had Crohn's disease and half had ulcerative colitis. The median time from last active IBD episode to immunotherapy initiation was 5 years (interquartile range, 3-12). Forty-three patients were not receiving treatment for IBD (Table 1). Gastrointestinal adverse events occurred in 42 patients (41%) after a median of 62 days (interquartile range, 33-123), a rate higher than that among similar patients without underlying IBD who were treated at centers participating in the study (11%; P &lt; 0.001). Gastrointestinal events among patients with IBD included grade 3 or 4 diarrhea in 21 patients. Four patients experienced colonic perforation, 2 of whom required surgery. No gastrointestinal adverse event-related deaths were recorded (Table 2). Anti-cytotoxic T-lymphocyte antign-4 therapy was associated with increased risk of gastrointestinal adverse events on univariate but not multivariate analysis (respectively, odds ratio, 3.19; 95%confidence interval, 1.8-9.48; P = 0.037 and odds ratio, 4.72; 95% confidence interval, 0.95-23.53; P = 0.058). CONCLUSION: Preexisting IBD increases the risk of severe gastrointestinal adverse events in patients treated with immune checkpoint inhibitors.

Bifunctional immune checkpoint-targeted antibody-ligand traps that simultaneously disable TGF\u03b2 enhance the efficacy of cancer immunotherapy

A majority of cancers fail to respond to immunotherapy with antibodies targeting immune checkpoints, such as cytotoxic T-lymphocyte antigen-4 (CTLA-4) or programmed death-1 (PD-1)/PD-1 ligand (PD-L1). Cancers frequently express transforming growth factor-β (TGFβ), which drives immune dysfunction in the tumor microenvironment by inducing regulatory T cells (Tregs) and inhibiting CD8+ and TH1 cells. To address this therapeutic challenge, we invent bifunctional antibody–ligand traps (Y-traps) comprising an antibody targeting CTLA-4 or PD-L1 fused to a TGFβ receptor II ectodomain sequence that simultaneously disables autocrine/paracrine TGFβ in the target cell microenvironment (a-CTLA4-TGFβRIIecd and a-PDL1-TGFβRIIecd). a-CTLA4-TGFβRIIecd is more effective in reducing tumor-infiltrating Tregs and inhibiting tumor progression compared with CTLA-4 antibody (Ipilimumab). Likewise, a-PDL1-TGFβRIIecd exhibits superior antitumor efficacy compared with PD-L1 antibodies (Atezolizumab or Avelumab). Our data demonstrate that Y-traps counteract TGFβ-mediated differentiation of Tregs and immune tolerance, thereby providing a potentially more effective immunotherapeutic strategy against cancers that are resistant to current immune checkpoint inhibitors.

Ipilimumab Lung Toxicity

SESSION TITLE: Lung Pathology 3 SESSION TYPE: Affiliate Case Report Poster PRESENTED ON: Tuesday, October 31, 2017 at 01:30 PM - 02:30 PM INTRODUCTION: A patient being treated with Ipilimumab developed granulomatous lung disease. CASE PRESENTATION: A 54 year old man was being treated for stage IIIc Melanoma with Ipilimumab. After his second infusion he developed a rash. Biopsy of a palmar lesion showed non-caseating granulomas. He developed dry cough and chest CT (Image 1) showed mediastinal lymphadenopathy and scattered sub centimeter lung nodules. The imaging findings were concerning for metastatic disease. A bronchoscopy with EBUS and fine needle aspiration of hilar and subcarinal lymph nodes was performed. Lymph node biopsy revealed non-caseating granulomas in both left hilar and subcarinal sites. Flow cytometry on lymph node FNA showed no clonal populations and a CD4/CD8 ratio of 4. The patient was treated with Prednisone for 2 months with resolution of his symptoms and improvement in CT findings (Image 2). He continues to receive Ipilimumab infusions for Melanoma therapy without any recurrence of his granulomatous disease. DISCUSSION: Novel immunotherapy agents have revolutionized the treatment of certain cancers in recent years. Some of these work by activating the immune system to aid in fighting tumor burden. Ipilimumab blocks CTLA-4, a T-cell activation checkpoint molecule, thereby promoting immunity against the tumor (1). It has been shown to improve survival in metastatic Melanoma and has become part of the standard treatment regimen (2). There have been case reports of a granulomatous sarcoid-like reaction to these medications (3). Lung manifestations can be mistaken for progression of the underlying malignancy. Clinicians should be aware of this important reaction and pursue tissue diagnosis to differentiate the two. CONCLUSIONS: Novel immunotherapy agents are being used to treat certain kinds of cancer. An important consideration of these treatments is the effect of activation of the immune system on other organs. A pulmonary sarcoid like reaction can resemble metastatic disease on imaging. Our case illustrates the importance of pursuing tissue diagnosis. A short course of steroids resulted in resolution of the pulmonary findings. Reference #1: O’Day SJ, et al. Targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4). Cancer, 110: 2614-2627. Reference #2: Hodi FS et al. Improved Survival with Ipilimumab in Patients with Metastatic Melanoma. N Engl J Med 2010; 363:711-23. Reference #3: Reule RB, North JP. Cutaneous and pulmonary sarcoidosis-like reaction associated with ipilimumab. J Am Acad Dermatol. 2013;69(5):e272-e273. DISCLOSURE: The following authors have nothing to disclose: Esha Oommen, Joanne Allam No Product/Research Disclosure Information

ASCO 2013—treatment of metastatic melanoma: is it still a story of success?

‘There is a light at the end of the tunnel in the treatment of metastatic melanoma’ was the slogan of enthusiastic dermatologists around the world in 2010, when two new substances were approved by the Food and Drug Association in the United States and later on, the European Medicines Agency in Europe. Ipilimumab (Yervoy®) is a fully human monoclonal antibody targeting cytotoxic T-lymphocyte antigen-4, which switches off the mechanism of immune suppression and enables continuous, unrestrained stimulation of T-cells by dendritic cells. The objective response rates are only 10–15 %, but most of them are long lasting. The second approved substance is vemurafenib (Zelboraf®), a selective BRAF inhibitor. BRAF is a member of the Raf family, which is part of the Ras/Raf/MEK/ERK mitogen-activated protein kinase (MAPK) signalling pathway. Approximately 40–60 % of cutaneous melanomas carry mutations in BRAF that lead to constitutive activation of downstream signalling through the MAPK pathway. However, the duration of response has been limited, as resistance to BRAF inhibitors develops within months after initiation of treatment. So in 2013 the question arises, whether the story of success in the treatment of metastatic melanoma is prolonged and whether there are some new promising substances in the treatment pipeline. At American Society of Clinical Oncology 2013, actual data of studies with other immune checkpoint molecules, such as programmed death-1 antibodies or antibodies against its ligand programmed death ligand 1, were presented, as well as data from downstream molecules of the MAPK pathway (e.g. MEK inhibitors). The most promising response rates, however, can be observed by combining these new substances.

Indoleamine 2,3-dioxygenase is a critical resistance mechanism in antitumor T cell immunotherapy targeting CTLA-4

The cytotoxic T lymphocyte antigen-4 (CTLA-4)-blocking antibody ipilimumab results in durable responses in metastatic melanoma, though therapeutic benefit has been limited to a fraction of patients. This calls for identification of resistance mechanisms and development of combinatorial strategies. Here, we examine the inhibitory role of indoleamine 2,3-dioxygenase (IDO) on the antitumor efficacy of CTLA-4 blockade. In IDO knockout mice treated with anti-CTLA-4 antibody, we demonstrate a striking delay in B16 melanoma tumor growth and increased overall survival when compared with wild-type mice. This was also observed with antibodies targeting PD-1-PD-L1 and GITR. To highlight the therapeutic relevance of these findings, we show that CTLA-4 blockade strongly synergizes with IDO inhibitors to mediate rejection of both IDO-expressing and nonexpressing poorly immunogenic tumors, emphasizing the importance of the inhibitory role of both tumor- and host-derived IDO. This effect was T cell dependent, leading to enhanced infiltration of tumor-specific effector T cells and a marked increase in the effector-to-regulatory T cell ratios in the tumors. Overall, these data demonstrate the immunosuppressive role of IDO in the context of immunotherapies targeting immune checkpoints and provide a strong incentive to clinically explore combination therapies using IDO inhibitors irrespective of IDO expression by the tumor cells.

Thrombocytopenia associated with ipilimumab therapy of advanced melanoma at a single institution.

9072 Background: Ipilimumab (IPi) is a monoclonal IgG1κ antibody targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4) that was approved for the treatment of metastatic melanoma (MM). IPi therapy is associated with immune-related adverse events (irAEs) (Weber et al. J Clin Oncol2012 Jul 20;30(21):2691-7). Hematologic toxicity has rarely been reported. Methods: We analyzed 172 pts with MM treated adjuvantly or for metastatic disease with IPi on 2 clinical studies and an expanded access program (protocols MCC15283, MCC15722 and MCC15977). Clinical characteristics and hematologic parameters related to therapy were recorded. Medications, infections, comorbidities, prior therapies, and pathology reports from bone marrow (BM) biopsies were reviewed. Results: Of 172 subjects, 10 (5.8%) pts with normal platelet counts prior to therapy, developed thrombocytopenia (TCP) following IPi. Median number of doses was 8.5 (range 1-19). Median age at development of TCP was 64 years (range 21-93). Median time to development of TCP was 16.5 months (range 0.25 – 39). Of ten pts, three developed grade (gr) 1 or 2 TCP, three developed gr 3 and four pts developed gr 4 thrombocytopenia. BM analysis in pts with gr 4 TCP showed normal hematopoiesis and no evidence of melanoma. Six of 10 (60%) pts required therapy and were initiated on prednisone, but were deemed steroid refractory. No sustained responses to subsequent treatments with IVIG, rituximab, danazol, and/or splenectomy were observed. Three pts with grade 4 TCP were treated with eltrombopag. One of them achieved a sustained complete response lasting &gt; 20 months. The other 2 pts who received eltrombopag discontinued treatment due to vascular events. Three out of 10 (30%) pts with any gr of TCP experienced mild bleeding episodes in the form of epistaxis. One pt with gr 4 thrombocytopenia experienced severe gastrointestinal bleeding requiring hospitalization. No deaths related to bleeding occurred. Conclusions: This is the first case series of hematologic irAEs in pts treated with IPi on clinical trials, suggesting that steroid refractory TCP may occur with IPi treatment . The timing and severity of IPi associated TCP is highly variable so careful hematologic monitoring should be considered.

Increase of regulatory T cells in metastatic stage and CTLA-4 over expression in lymphocytes of patients with non-small cell lung cancer (NSCLC)

We hypothesized that the increased percentages of Regulatory T (Treg) cells, as well as over expression of Cytotoxic T Lymphocyte Antigen-4 (CTLA-4) by lymphocyte subsets might be associated with lung cancer. Accordingly, peripheral blood of 23 new cases with non-small cell lung cancer (NSCLC) and 16 healthy volunteers were investigated, by follow cytometry, for the prevalence of CD4+CD25+FoxP3+ Treg cells as well as surface (sur-) and intracellular (In-) expression of CTLA-4 by the main lymphocyte subsets (CD4+, CD8+ and CD19+). Results indicated that NSCLC patients had an increased percentage of Treg cells than controls (7.9±4.1 versus 3.8±1.8, P=0.001). The proportion of Treg cells was observed to be increased by stage increase in patients (stage II=5.2±2.4, stage III=7.9±4.4, stage IV=12.0±2.2), and also significantly higher in metastatic than non-metastatic stages (12.0±2.2 versus 6.8±3.9, P=0.023). Increase of SurCTLA-4- as well as InCTLA-4-expressing lymphocytes in patients were observed in nearly all investigated subsets, but significant differences between patients and controls were observed about InCTLA-4+CD4+ lymphocytes (8.6±7.1 and 3.8±5.3 respectively, P=0.006) as well as SurCTLA-4+CD8+ lymphocytes (0.3±0.2 and 0.2±0.1 respectively, P=0.047). In conclusion, the results suggest that immunotherapy regimen targeting CTLA-4 and Treg cells might be beneficial in lung cancer patients.

Long-term survival of patients (pts) with advanced melanoma treated with ipilimumab with or without dacarbazine

9038 Background: Ipilimumab is a fully human monoclonal antibody targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4). Here, we report updated survival of pts with advanced melanoma treated with ipilimumab in 2 completed studies. Methods: Seventy-two chemotherapy-naïve pts were randomized to receive 3 mg/kg ipilimumab every 4 weeks (Q4W) × 4 alone or with ≤6 × 5-day courses of DTIC 250 mg/m2/day (ipilimumab, n = 37; ipilimumab + DTIC, n = 35) in the multicenter, open- label Phase II study MDX010–08 (Sep 2002-Aug 2004)(Hersh E et al. J Clin Oncol 26: 2008 (May 20 suppl; abstr 9022)). In the phase I/II dose-ranging study MDX010–15, 23 pts were treated with 10 mg/kg ipilimumab every 3 weeks (Q3W) × 4 (induction) (Jun 2004- Jul 2006) (Urba W et al. J Clin Oncol 26: 2008 (May 20 suppl; abstr 3018)). No maintenance ipilimumab was administered in either study. Long-term survival was determined under a follow-up protocol (MDX010–28) from May 2007-Jan 2008. Results: Long-term data are available for 62 pts for MDX010–08 and 22 pts for MDX010–15. For MDX010–08, the median follow-up was 4.3 years (range, 4.0–4.7 years); it was 2.2 years (range, 2.0–2.4 years) for MDX010–15. Survival rates are reported in the Table . Conclusions: Ipilimumab monotherapy, administered at 3 mg/kg and without maintenance dosing, resulted in survival rates better than those observed with historical controls (Korn EJ et al. J Clin Oncol 26:527–34; 2008). Adding DTIC to ipilimumab did not suppress the effect of ipilimumab (as might have been predicted), but enhanced it still further. Consistent with previously reported response data showing that 10 mg/kg is the recommended dose (study CA184022) (Hamid O et al. J Clin Oncol 26: 2008 (May 20 suppl; abstr 9025)), there was a trend toward better survival with the higher dose (eg, a 2-year survival rate of 36% vs. 22% for 10 mg/kg vs. 3 mg/kg). [Table: see text] [Table: see text]

Anti–Cytotoxic T-Lymphocyte Antigen-4 Antibody: The First in an Emerging Class of Immunomodulatory Antibodies for Cancer Treatment

To evaluate the emerging role of immunomodulatory antibodies in cancer treatment. Antibodies (ipilimumab and tremelimumab) targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4), an inhibitory molecule on T cells, represent the vanguard of these new drugs. We performed a systematic review of the clinical studies examining the clinical activity of anti-CTLA-4 antibodies. We also review the potential mechanisms and toxicities associated with these treatments. Clinical activity with anti-CTLA-4 monoclonal antibodies (mAbs) has paved the way for additional T-cell immunomodulatory monoclonal antibody (mAb) approaches for the treatment of cancer to be investigated. Because anti-CTLA-4 mAbs target the immune system and not the tumor, they may provide significant potential advantages over traditional antitumor mAbs, chemotherapies, and immunotherapies (ie, vaccines and cytokines). Other antibodies, such as CD137 agonists, CD40 agonists, and PD-1 antagonists, are currently in various stages of preclinical and clinical development. Available clinical data suggest that anti-CTLA-4 mAbs are very different from traditional mAbs, chemotherapies, and immunotherapies in terms of patterns of response, duration of response, and adverse event profile. Ongoing clinical studies aim to establish the efficacy and safety of anti-CTLA-4 mAbs as monotherapy or in combination with other drugs for the treatment of metastatic melanoma and a variety of other cancer types.

Disease control and long-term survival in chemotherapy-naive patients with advanced melanoma treated with ipilimumab (MDX- 010) with or without dacarbazine

9022 Background: Ipilimumab is a fully human monoclonal antibody targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4) that gave durable complete/partial responses [CR/PR] and stable disease [SD]) in previously treated patients with advanced melanoma. The current study evaluated the safety and efficacy of ipilimumab and whether adding dacarbazine (DTIC) would improve outcome. In addition to being cytotoxic, DTIC may also increase the release of tumor neo-antigen, ie, act as an immunosupportive (Peggs et al. Cancer Cell.12:192, 2007) agent. Methods: Chemotherapy-naive patients with advanced melanoma were treated in the randomized, phase II, comparative, multicenter, open-label study MDX-010–08 (first patient, first visit September 2002; last patient, last visit August 2004). Patients received 3 mg/kg ipilimumab every 4 weeks (Q4W) X 4 alone or with up to six 5-day courses of DTIC 250 mg/m2 per day. Efficacy was determined using Response Evaluation Criteria for Solid Tumors. Overall survival data was collected. Results: Seventy-two patients were randomized, treated per protocol, and eligible for analysis (ipilimumab, n = 37; ipilimumab + DTIC, n = 35). The disease control rate (best response of CR + PR + SD) was 21.6% (n = 8) and 31.4% (n = 11) in the monotherapy and combination arms, respectively. In 6 of these 19 patients, disease control lasted ≥24 weeks, including 2 ongoing CRs in the combination arm lasting 40+ and 92+ weeks. Long-term data are available for 54/72 patients: 5/54 patients (9.3%) are still alive (ipilimumab, n = 2/19 [10.5%]; ipilimumab + DTIC, n = 3/27 [11.1%]). The median OS for all patients was 368.5 days [95% CI, 276 - 472]; for the monotherapy and combination groups, respectively, the median OS was 351 [95% CI, 208 - 596] and 386 [95% CI, 253 - 571] days. Updated data will be presented. Conclusions: At least ∼10% of chemotherapy-naive patients with advanced melanoma treated with ipilimumab ± DTIC were alive after 2 to >4 years of follow up. DTIC appeared to augment ipilimumab efficacy. A study is ongoing to determine if ipilimumab administered at 10 mg/kg Q3W X 4 followed by maintenance therapy with DTIC will further improve the efficacy of this combination. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Medarex Amgen, Bristol-Myers Squibb, Medarex, Pfizer, Schering-Plough Medarex Bristol-Myers Squibb Bristol-Myers Squibb, Medarex

Targeting cytotoxic T‐lymphocyte antigen‐4 (CTLA‐4)

Cancer immunotherapy centers on modulating the host's tumor-directed immune response. One promising approach involves augmentation of cell-mediated immunity by interrupting T-cell pathways responsible for immune down-regulation or tolerance. The discovery of cytotoxic T-lymphocyte antigen-4 (CTLA-4) and its role as a key negative regulator for T cells has prompted efforts to target this signaling molecule to improve cancer therapy. Activation, or 'priming', of naive T cells in response to tumor-cell invasion comprises a dual-signaling mechanism. Signal 1 requires tumor-associated antigen recognition by the T-cell receptor, while signal 2 occurs through binding of CD80 or CD86 (B7.1 of 2) on the antigen presenting cell (APC) with CD28 on the T cell. Importantly, there is a final step responsible for naturally occurring immune regulation; this occurs in response to competitive binding of CD80/CD86 on the APC by CTLA-4 on the T cell. This 'immune checkpoint' interrupts signal 2 and inhibits the activated T cell. Targeting CTLA-4 as an anticancer strategy: Following proof-of-concept studies in animals, fully human anti-CTLA-4 antibodies were developed and 2 are undergoing clinical evaluation. Ipilimumab and tremelimumab have shown promising antitumor activity, initially in patients with advanced melanoma. Class-specific immune-related adverse events (irAEs) were common and mostly transient and/or manageable. These events are thought to be mechanism-of-action-related, indicating immune tolerance is broken; this relation may also explain the association between irAEs and response seen in several trials. Interruption of immune inhibitory pathways via CTLA-4 blockade appears to be a promising strategy for cancer immunotherapy.