Antibody Ipilimumab Research Articles

A reappraisal of CTLA-4 checkpoint blockade in cancer immunotherapy

It is assumed that anti-CTLA-4 antibodies cause tumor rejection by blocking negative signaling from B7-CTLA-4 interactions. Surprisingly, at concentrations considerably higher than plasma levels achieved by clinically effective dosing, the anti-CTLA-4 antibody Ipilimumab blocks neither B7 trans-endocytosis by CTLA-4 nor CTLA-4 binding to immobilized or cell-associated B7. Consequently, Ipilimumab does not increase B7 on dendritic cells (DCs) from either CTLA4 gene humanized (Ctla4h/h) or human CD34+ stem cell-reconstituted NSG™ mice. In Ctla4h/m mice expressing both human and mouse CTLA4 genes, anti-CTLA-4 antibodies that bind to human but not mouse CTLA-4 efficiently induce Treg depletion and Fc receptor-dependent tumor rejection. The blocking antibody L3D10 is comparable to the non-blocking Ipilimumab in causing tumor rejection. Remarkably, L3D10 progenies that lose blocking activity during humanization remain fully competent in inducing Treg depletion and tumor rejection. Anti-B7 antibodies that effectively block CD4 T cell activation and de novo CD8 T cell priming in lymphoid organs do not negatively affect the immunotherapeutic effect of Ipilimumab. Thus, clinically effective anti-CTLA-4 mAb causes tumor rejection by mechanisms that are independent of checkpoint blockade but dependent on the host Fc receptor. Our data call for a reappraisal of the CTLA-4 checkpoint blockade hypothesis and provide new insights for the next generation of safe and effective anti-CTLA-4 mAbs.

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.

Development of a Targeted Mass-Spectrometry Serum Assay To Quantify M-Protein in the Presence of Therapeutic Monoclonal Antibodies.

M-protein diagnostics can be compromised for patients receiving therapeutic monoclonal antibodies as treatment in multiple myeloma. Conventional techniques are often not able to distinguish between M-proteins and therapeutic monoclonal antibodies administered to the patient. This may prevent correct response assessment and can lead to overtreatment. We have developed a serum-based targeted mass-spectrometry assay to detect M-proteins, even in the presence of three therapeutic monoclonal antibodies (daratumumab, ipilimumab, and nivolumab). This assay can target proteotypic M-protein peptides as well as unique peptides derived from therapeutic monoclonal antibodies. We address the sensitivity in M-protein diagnostics and show that our mass-spectrometry assay is more than two orders of magnitude more sensitive than conventional M-protein diagnostics. The use of stable isotope-labeled peptides allows absolute quantification of the M-protein and increases the potential of assay standardization across multiple laboratories. Finally, we discuss the position of mass-spectrometry assays in monitoring minimal residual disease in multiple myeloma, which is currently dominated by molecular techniques based on plasma cell assessment that requires invasive bone marrow aspirations or biopsies.

Development of anti-drug antibodies is associated with shortened survival in patients with metastatic melanoma treated with ipilimumab

ABSTRACTIntroduction: Checkpoint inhibitors, including the CTLA-4 blocking antibody ipilimumab, have become the new standard therapy for many metastatic cancers. Development of anti-drug antibodies (ADAs) after treatment with other biopharmaceuticals has been thoroughly described, but the induction of ADAs after treatment with checkpoint inhibitors has been inadequately investigated. In this retrospective study, we relate ipilimumab serum levels and anti-ipilimumab antibody levels to clinical outcomes in patients with metastatic melanoma (MM).Method: Serum samples from 31 patients with MM were analyzed for serum levels of ipilimumab and ADAs to ipilimumab at baseline, and before the 2nd and 4th infusion using an in-house bead-based assay. The results were correlated with progression-free survival (PFS) and overall survival (OS).Results: Low serum levels of ipilimumab before the 2nd infusion correlated significantly with a shorter OS (p = 0.01) and PFS (p = 0.02). Eight patients (26%) were ADA-positive at either timepoint. ADA positivity correlated significantly with a shorter OS (p = 0.03) with a hazard ratio (HR) of 3.0 (95% CI: 1.2-7.8). Four of 8 ADA-positive patients (50%) discontinued therapy before the 4th infusion due to disease progression, compared to three of 23 (13%) ADA-negative patients.Conclusion: We confirm that low serum levels of ipilimumab are associated with a shortened OS, and we show for the first time that ADAs to ipilimumab are associated with shorter OS in patients with MM.

Checkpoint immunotherapy by nivolumab for treatment of metastatic melanoma.

Clinical management of metastatic melanoma suffered historically from a lack of effective targeted and immunotherapies due to short-lived clinical responses. Recent advances in our understanding of tumor-immune signaling pathways, discovery of immunosuppressive checkpoints, and subsequent development of antibodies that target these checkpoints reverses the situation to some extent. Two antibodies ipilimumab and nivolumab gained Food and Drug administration approval for the treatment of metastatic melanoma and target two major immunosuppressive checkpoints cytotoxic T lymphocyte antigen and programmed cell death protein 1 (PD-1), respectively. Nivolumab binds to PD-1, prevents PD-1 interaction with ligand Programmed death ligand 1 (PD-L1), and thus releases the T-cell exhaustion events (such as T cell apoptosis, decrease in T cell proliferation, etc.) leading to buildup of potent tumor-specific immune response. Successful Phase I-III results with remarkable antitumor activity and safety led to approval of nivolumab against ipilimumab refractory metastatic melanoma. Nivolumab therapy is exciting in that it not only provides substantial benefit but also provides durable responses. This review focuses on the evolution of immunotherapy leading to nivolumab approval and its potential in treating melanoma either alone or in combination with other therapies.

Immunotherapy of melanoma

The immunotherapy is currently changing the landscape of oncology. Nowadays the standard of care in metastatic or unresectable melanoma patients include immunomodulating modalities such as anti-PD-1 drugs (nivolumab, pembrolizumab) and anti-CTLA-4 antibody ipilimumab. The improvements of progression free survival and overall survival connected with those treatments were unprecedented and have been confirmed in stage III trials. The efficacy of immunotherapy in metastatic setting can be further upgraded in some groups of patients by combining both types of antibodies. Latest clinical data suggest that treatment with immunotherapy can be also favorable for patients in adjuvant setting. Other treatment approaches based on immunological response (e.g. oncolytic viruses or adoptive cell therapy) have been proven useful in specific clinical situations. The future of melanoma treatment is still evolving, new molecular targets are being invented and hopefully current endeavors will led to further improvement of patients’ survival. This review aims to summarize current state of immunotherapy in melanoma and identifying possible directions of development.

Clinical assessment of immune-related adverse events.

Immunotherapy through checkpoint inhibitors is now standard practice for a growing number of cancer types, supported by overall improvement of clinical outcomes and better tolerance. One anti-CTLA-4 antibody (ipilimumab), two anti-PD-1 antibodies (pembrolizumab and nivolumab) and three anti-PD-L1 antibodies (atezolizumab, avelumab and durvalumab) have been approved for clear benefits across diverse trials. Adverse events of an immune nature associated with these agents frequently affect the skin, colon, endocrine glands, lungs and liver. Most of these effects are mild and can be managed through transient immunosuppression with corticosteroids, but high-grade events often require hospitalization and specialized treatment. However, since immunotherapy is recent, physicians with clinical experience in the diagnosis and management of immune toxicities are frequently those who actively participated in trials, but many practicing oncologists are still not familiarized with the assessment of these events. This review focuses on the incidence, diagnostic assessment and recommended management of the most relevant immune-related adverse events.

Abstract B036: Synthetic DNA-encoded monoclonal antibody delivery (DMAbTM) of anti-CTLA4 antibodies induces tumor shrinkage in vivo

Abstract Antibody-based immune therapies targeting the T-cell checkpoint inhibitors CTLA4 and PD1 have made incredible advances in cancer therapy. In particular, the combination of CTLA4 and PD1 blockade (using ipilimumab and nivolumab, respectively) was recently shown to be the most effective immune therapy for improving progression-free survival in advanced melanoma patients. However, this immune therapy combination strategy is extraordinarily expensive due to high manufacturing costs of monoclonal antibodies, with an estimated annual cost of almost one million dollars per patient. In this study, we focused on the development of a DNA-encoded monoclonal antibody (DMAbTM) approach for delivery of anti-CTLA4 monoclonal antibodies in vivo. With this technology, formulated DMAbTM plasmids are injected into the muscle with electroporation, allowing for muscle cells to produce and secrete the DMAbTM for a prolonged period of time without the need for repeated administration. In proof-of-concept studies in mice, we show that delivery of a DMAbTM plasmid for a monoclonal antibody targeting mouse CTLA4 (clone 9D9) elicits high serum expression (peak expression of 7.9µg/mL in immune-competent C57Bl/6 mice with one injection of DNA). This anti-mouse CTLA4 DMAbTM is capable of inducing tumor regression in A/J mice that were implanted with the immunogenic Sa1N tumor cell line without repeated administration. Furthermore, this anti-mouse CTLA4 DMAbTM is capable of synergizing with a DNA vaccine targeting the tumor antigen TERT in slowing tumor growth for the nonimmunogenic TC-1 tumor cell line. We also examined DNA delivery of the anti-human CTLA4 antibodies ipilimumab and tremelimumab. For these anti-human CTLA4 DMAbsTM, we achieved steady-state levels of approximately 75µg/mL and 50ug/mL for ipilimumab and tremelimumab, respectively, in mice, which is greater than the mean trough levels of ipilimumab achieved in patients (21.8µg/mL serum concentration for 3mg/kg dose). These anti-human CTLA4 DMAbsTM produced in vivo bind to human CTLA4 protein and induce T-cell activation in a functional assay ex vivo. These results demonstrate the feasibility of delivering immune checkpoint blockade monoclonal antibodies using DNA for cancer immune therapy. Future studies will explore combination therapies with CTLA4 DMAbsTM and chemotherapy. Citation Format: Elizabeth Duperret, Aspen Trautz, Ami Patel, Joseph Kim, Kar Muthumani, David B. Weiner. Synthetic DNA-encoded monoclonal antibody delivery (DMAbTM) of anti-CTLA4 antibodies induces tumor shrinkage in vivo [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B036.

Urothelial Carcinoma of the Bladder and the Rise of Immunotherapy.

With the advent of platinum-based chemotherapy, survival rates for metastatic urothelial carcinoma have plateaued, giving way to the modern immunotherapy paradigm. Although immunotherapy as an effective treatment dates back to the live, attenuated bacillus Calmette-Guérin vaccine, the recent impact of immune checkpoint inhibitors targeting programmed death/programmed death-ligand 1 (PD-1/PD-L1) coupled with the promise of both anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibodies and indoleamine-2, 3-dioxygenase-1 (IDO-1) inhibitors have provided a resurgence. To date, pembrolizumab, a PD-1 inhibitor, has been granted full FDA approval based on its high antitumor activity, tolerability, and efficacy, with notable prolonged durable responses in the second-line setting. Nivolumab (a PD-1 inhibitor) and atezolizumab, durvalumab, and avelumab (PD-L1 inhibitors) have also gained accelerated drug approval in the second-line setting. In addition, atezolizumab and pembrolizumab have been approved for platinum-ineligible patients in the first-line setting. Effective 2-drug combinations reported include nivolumab plus the CTLA-4 antibody ipilimumab and pembrolizumab plus the IDO-1 inhibitor epacadostat. Further expansion of immunotherapy will hinge in part on the ability to define responders versus nonresponders through the use of biomarkers like PD-L1 or mutational load. Clinical trials with immunotherapy for metastatic disease as single agents or in combination are ongoing. This review explores the rise of immunotherapy and presents the current treatments and challenges posed with development of biomarkers, and provides a summary of ongoing phase III clinical trials.

Immune-related adverse events during anticancer immunotherapy: Pathogenesis and management.

Immunotherapy is one of the most recent systemic treatments to emerge for use in oncology, and is based on the blocking of inhibitory immune checkpoints to potentiate the immune response to cancer. The anti-cytotoxic T lymphocyte-associated antigen-4 antibody ipilimumab and anti-programmed cell death protein 1 antibodies, including nivolumab and pembrolizumab, are currently available and widely used, and other immune-inhibiting antibodies are now under intensive investigation. These antibodies have shown efficacy in a growing number of tumor types, following initial observations of their notable effects in melanoma treatment. Despite the efficacy of these antibodies, their novel mechanisms of action are also associated with a new class of side effects called immune-related adverse events (IRAEs). These side effects do not share a common pathophysiology with other anticancer treatments and, therefore, they often require specific therapies. When detected early and correctly treated, IRAEs are reversible; however, they can become severe and life-threatening if underestimated or inappropriately treated. This review aims to revisit the pathogenesis of IRAEs, with attention to gastrointestinal manifestations, since these are common and potentially dangerous complications of immunotherapy and represent a major cause of treatment discontinuation. Recommendations and guidelines for the management of IRAEs are also presented, in order to provide a clear and applicable algorithm for use by clinicians.

Immunotherapy in Non-Small Cell Lung Cancer Treatment: Current Status and the Role of Imaging.

Lung cancer remains the leading cause of cancer-related mortality and is responsible for more deaths than breast, prostate, and colon cancer combined. Most patients are diagnosed with advanced disease at the time of presentation, and treatment options have traditionally included surgery, chemotherapy, and/or radiation. However, significant advances in the molecular characterization of lung cancer have led to the creation of effective immunotherapies that assist in the recognition of cancer as foreign by the host immune system, stimulate the immune system, and relieve the inhibition that allows tumor growth and spread. Extensive experience with the immunomodulatory monoclonal antibody ipilimumab has demonstrated that unique responses may be seen with immunotherapies that are not adequately captured by traditional response criteria such as the World Health Organization criteria and Response Evaluation Criteria in Solid Tumors (RECIST). Consequently, several modified criteria have been developed to evaluate patients treated with immunotherapy, including immune-related response criteria, immune-related RECIST, and immune RECIST. Finally, patients undergoing immunotherapy may develop a wide variety of immune-related adverse events with which the radiologist must be familiar. In this article, we present the fundamental concepts behind immunotherapy, specific agents currently approved for the treatment of lung cancer, and immune-related adverse events. The role of imaging in the evaluation of these patients will also be discussed, including the general principles of treatment response evaluation, specific response criteria adopted with these agents, including immune-related response criteria, immune-related RECIST, and immune RECIST, and the imaging of immune-related adverse events.

Abstract 2618: Agonist antibodies targeting OX40 and GITR enhance the activity of the IDO1-selective inhibitor epacadostat in preclinical models

Abstract The majority of immunotherapeutic agents developed thus far either attempt to stimulate a more productive anti-tumor immune response or to inhibit key proteins in the immunosuppressive tumor milieu. PD-1/PD-L1 axis blockade, CTLA-4 blockade and IDO1 inhibition are examples of the latter approach and have been utilized to reverse the suppressive tumor microenvironment, resulting in clinical benefit for cancer patients. Recent clinical and preclinical data have also demonstrated that combining these approaches results in enhanced therapeutic benefit. Notably, the IDO1-selective inhibitor epacadostat has been shown to increase the efficacy of two checkpoint inhibitors, the anti-CTLA-4 antibody ipilimumab and the anti-PD-1 antibody pembrolizumab, in patients with melanoma. Because both checkpoint receptors and IDO1 serve as negative regulators of the immune response, we also explored the ability of IDO1 inhibition to combine with agents that directly activate T cells through costimulatory receptors of the tumor necrosis factor receptor (TNFR) superfamily. Rodent active surrogate agonist antibodies to 4-1BB, OX40 and GITR were tested with epacadostat in multiple preclinical models. In the B16-SIY melanoma model that does not express IDO1 in tumor cells, both epacadostat and anti-OX40 had little effect, but the combination resulted in enhanced efficacy. This was associated with increased infiltrates of CD8+ T cells and decreased numbers of FoxP3+ TILs. Increased numbers of SIY-reactive T cells were found in both the tumor and the TDLN post-therapy. In contrast, epacadostat did not provide any enhancement to the activity seen with 4-1BB. Clear combinatorial effects were seen with anti-GITR and epacadostat in the more inflamed, IDO1-expressing PAN02 pancreatic cancer model. These data suggest that IDO1 inhibition can be effective in combination with agents that agonize T cell costimulatory receptors as well as with agents that block coinhibitory receptors. Citation Format: Holly K. Koblish, Brendan Horton, Michael Hansbury, Sybil O'Connor, Kerri Lasky, Christina Stevens, Thomas Condamine, Leslie Hall, Liang-Chuan Wang, Yue Zhang, Horacio Nastri, Gregory Hollis, Reid Huber, Thomas Gajewski, Peggy Scherle. Agonist antibodies targeting OX40 and GITR enhance the activity of the IDO1-selective inhibitor epacadostat in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2618. doi:10.1158/1538-7445.AM2017-2618

Abstract NG04: Mechanisms of resistance to anti-PD-1 immunotherapy through interferon pathway mutations

Abstract NG04: Mechanisms of resistance to anti-PD-1 immunotherapy through interferon pathway mutations

Predictive value of PD-L1 based on mRNA level in the treatment of stage IV melanoma with ipilimumab.

PD-L1 is established as a predictive marker for therapy of non-small cell lung cancer with pembrolizumab. Furthermore, PD-L1 positive melanoma has shown more favorable outcomes when treated with anti-PD1 antibodies and dacarbazine compared to PD-L1 negative melanoma. However, the role of PD-L1 expression with regard to response to checkpoint inhibition with anti-CTLA-4 is not clear, yet. In addition, the lack of standardization in the immunohistochemical assessment of PD-L1 makes the comparison of results difficult. In this study, we investigated the PD-L1 gene expression with a new fully automated technique via RT-PCR and correlated the findings with the response to the anti-CTLA-4 antibody ipilimumab. Within a retrospective multi-center trial, PD-L1 gene expression was evaluated in 78 melanoma patients in a total of 111 pre-treatment tumor samples from 6 skin cancer centers and analyzed with regard to response to ipilimumab. For meaningful statistical analysis, the cohort was enriched for responders with 30 responders and 48 non-responders. Gene expression was assessed by quantitative RT-PCR after extracting mRNA from formalin-fixed paraffin embedded tumor tissue and correlated with results from immunohistochemical (IHC) stainings. The evaluation of PD-L1 expression based on mRNA level is feasible. Correlation between PD-L1 expression as assessed by IHC and RT-PCR showed varying levels of concordance depending on the antibody employed. RT-PCR should be further investigated to measure PD-L1 expression, since it is a semi-quantitative method with observer-independent evaluation. With this approach, there was no statistical significant difference in the PD-L1 expression between responders and non-responders to the therapy with ipilimumab. The evaluation of PD-L1 expression based on mRNA level is feasible. Correlation between PD-L1 expression as assessed by IHC and RT-PCR showed varying levels of concordance depending on the antibody employed. RT-PCR should be further investigated to measure PD-L1 expression, since it is a semi-quantitative method with observer-independent evaluation. With this approach, there was no statistical significant difference in the PD-L1 expression between responders and non-responders to the therapy with ipilimumab.

Efficacy and safety of anti-PD-1 and anti-PD-1 combined with anti-CTLA-4 immunotherapy to advanced melanoma: A systematic review and meta-analysis of randomized controlled trials.

Background:Anti-PD-1 monoclonal antibodies, nivolumab and pembrolizumab, and anti-CTLA-4 antibody ipilimumab are being in clinic trials to treat melanoma. Here, we performed a meta-analysis to evaluate the efficacy and toxicity of them against advanced melanoma.Methods:Eleven reports from 6 randomized control trials on treating metastatic melanoma, which were divided into 3 subgroups, nivolumab/pembrolizumab versus chemotherapy, nivolumab versus ipilimumab, and nivolumab-plus-ipilimumab versus ipilimumab, were included and the meta-analysis was performed for each subgroup. The outcome measures were objective response rates (ORR), median progression free survival (PFS), 1-year overall survival rates (OS), and toxicity estimated by grade 3 to 4 adverse events.Results:For nivolumab/pembrolizumab versus chemotherapy, nivolumab versus ipilimumab, and nivolumab-plus-ipilimumab versus ipilimumab, the pooled risk ratios (RR) of the ORR were 3.43 (95% CI: 2.57–4.58), 2.51 (95% CI: 2.03–3.09), and 3.28 (95% CI: 2.58–4.17), respectively. The pooled HR of PFS were 0.42 (95% CI: 0.36–0.49), 0.58 (95% CI: 0.50–0.66), and 0.41 (95% CI: 0.30–0.52), respectively. The pooled RR of 1-year OS was 1.37 (95% CI: 1.08–1.74) and 1.54 (95% CI: 0.90–2.63) for nivolumab versus ipilimumab and nivolumab-plus-ipilimumab versus ipilimumab. These results suggested that anti-PD-1 monotherapy and nivolumab-plus-ipilimumab therapy had ORR and PFS benefit compared with the control group. Anti-PD-1 treatment increased 1-year OS for patients compared with ipililumab treatment. But there is no significantly difference on 1-year OS between the nivolumab-plus-ipilimumab treatment and the ipilimumab treatment group. The toxicity analysis showed that there is less risk of adverse events in the anti-PD-1 treatment group compared with the chemotherapy and ipilimumab group. Combining nivolumab with ipilimumab increased the risk for high-grade adverse events compared with ipilimumab alone but the adverse events were generally manageable.Conclusions:Anti-PD-1 monotherapy and nivolumab-plus-ipilimumab therapy improved ORR and prolonged PFS of patients with advanced melanoma and the adverse events are generally manageable. The therapy is indeed a promising approach for treatment of advanced melanoma.

Immunotherapy in lymphoma.

Immunotherapy in lymphoma.

A dose escalation phase 1 study of radiotherapy (RT) in combination with anti-cytotoxic-T-lymphocyte-associated antigen 4 (CTLA-4) monoclonal antibody ipilimumab in patients (pts) with metastatic melanoma.

9549 Background: Preclinical findings have shown a synergy between RT and anti-CTLA-4 monoclonal antibody in several tumor animal models for both local tumor control and distant effects. Preliminary clinical data suggest that it could be due to an abscopal effect of RT. The Mel-Ipi-Rx phase 1 study aimed to determine the maximum tolerated dose (MTD) and safety profile of RT combined with ipilimumab in pts with metastatic melanoma. Methods: A 3+3 dose escalation design was used with 9, 15, 18 and 24 Gy dose of RT (in 3 fractions) at week 4 combined with 10 mg/kg ipilimumab (every 3 weeks for 4 doses). Pts with evidence of clinical benefit at week 12 were eligible for maintenance ipilimumab at 10 mg/kg every 12 weeks starting at week 24 until severe toxicity or disease progression based on immune-related response criteria (irRC). Results: 19 pts with advanced melanoma received ipilimumab between August 2011 and July 2015. Nine pts received the 4 doses of ipilimumab and 2 pts received maintenance ipilimumab (1 and 2 cycles respectively). All pts received the combined RT at week 4 in 3 fractions. All pts presented at least one AE of any grade. The most common AEs were asthenia, diarrhea, desease-related pain and fever. Grade 3 AEs occurred in 8 pts. They included colitis (n = 3), hepatitis (n = 2), anemia (n = 2), asthenia (n = 1), thyroid disorders (n = 1) and nausea/vomiting (n = 1). Nine pts discontinued the study owing to treatment-related adverse events including colitis (n = 6), hepatitis (n = 2) and DRESS (Drug Rash with Eosinophilia and systemic syndrome) (n = 1). DLT occurred in 2/6 pts in the cohort receiving 15 Gy. No drug-related death occurred. According to irRC, 4 partial responses (ORR: 21%) and 4 stable diseases were observed at week 24. The MTD was 9 Gy dose. One pt out of 12 treated in the 9 Gy cohort presented a DLT (grade 3 colitis). The median progression-free survival [95% CI] was 7.2 months [2.4 – 16.8]. The median overall survival [95% CI] was 14.4 months [7.2 – 20.4]. Conclusions: When combined with ipilimumab at 10 mg/kg, in the present design, the MTD of RT was 9 Gy. This combination appears to be associated with antitumor activity. Clinical trial information: 2010-020317-93.

Immune checkpoint inhibitor treatment of advanced age metastatic melanoma (MM) patients.

e14603 Background: Immune checkpoint inhibitor (ICI) treatment has become effective method of treating mm including in those over 65 years of age. Increasing number of advanced age mm patients (pts.) are eligible for ICI treatment but not much is known about its efficacy and safety in relation to senescent immune system. We are reporting our updated experience of ICI treatment of advanced age mm pts. from a single Institute. Methods: Between 2011 and 2016, 32 eligible pts. diagnosed with mm were treated at the University of Connecticut with ICI including anti CTLA-4 antibody Ipilimumab, anti PD-1 antibody Pembrolizumab or combination of Ipilimumab and Nivolumab at their FDA approved doses on a standard protocol. Pts. were monitored for immune related adverse events (irAE) that were graded and managed with standard immune suppressive regimens Results: 12 out of 32 mm pts. were over 70 years of age (median 82.5 years, range 73-88 years). Nine pts. were treatment naïve, two had previously failed Ipilimumab treatment and one anti-BRAF and anti- MEK targeted therapy. Clinical benefit occurred in 5 out of 12 pts. (Complete response (CR) 3, partial response 1 and stable disease 1). Nine out of 12 pts. developed irAE that included three grade II (fatigue, diarrhea, hypopituitarism each) and 6 grade IV events (skin rash-1, colitis-1, encephalopathy-1, myasthenia gravis-1, and pneumonitis in 2 pts. each respectively). Of note, an 87-year-old male developed polymyalgia rheumatica after second dose of anti PD-1 treatment that responded to steroids, but developed autoimmune diabetes mellitus and pneumonitis following third dose. Two pts. died from irAE that included an 87-year-old woman from treatment refractory myasthenia gravis and 77-year-old male who suffered sudden death during steroid treatment of pneumonitis. Six pts. died of progressive disease including sudden death in a 77-year old woman and a 87-year-old male following five and two anti PD-1 treatments respectively. One pt. died from pulmonary embolism and four pts. are alive, 2 in CR and two with disease. Conclusions: Our experience indicate advanced age mm pts. respond to ICI treatment but have heightened risk of developing serious irAEs.

ImmunoPET Imaging of CTLA-4 Expression in Mouse Models of Non-small Cell Lung Cancer.

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) is expressed on the surface of activated T cells and some tumor cells, and is the target of the clinically approved monoclonal antibody ipilimumab. In this study, we investigate specific binding of radiolabeled ipilimumab to CTLA-4 expressed by human non-small cell lung cancer cells in vivo using positron emission tomography (PET). Ipilimumab was radiolabeled with 64Cu (t1/2 = 12.7 h) through the use of the chelator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) to formulate 64Cu-DOTA-ipilimumab. CTLA-4 expression in three non-small cell lung cancer (NSCLC) cell lines (A549, H460, and H358) was verified and quantified by Western blot and enzyme-linked immunosorbent assays (ELISA). A receptor binding assay was utilized to monitor the binding and internalization of 64Cu-DOTA-ipilimumab in the NSCLC cell lines. Next, the biodistribution of 64Cu-DOTA-ipilimumab was mapped by longitudinal PET imaging up to 48 h after injection. Ex vivo biodistribution and histological studies were employed to verify PET results. By in vitro analysis, CTLA-4 was found to be expressed on all three NSCLC cell lines with A549 and H358 showing the highest and lowest level of expression, respectively. PET imaging and quantification verified these findings as the tracer accumulated highest in the A549 tumor model (9.80 ± 0.22%ID/g at 48 h after injection; n = 4), followed by H460 and H358 tumors with uptakes of 9.37 ± 0.26%ID/g and 7.43 ± 0.05%ID/g, respectively (n = 4). The specificity of the tracer was verified by injecting excess ipilimumab in A549 tumor-bearing mice, which decreased tracer uptake to 6.90 ± 0.51%ID/g at 48 after injection (n = 4). Ex vivo analysis following the last imaging session also corroborated these findings. 64Cu-DOTA-ipilimumab showed enhanced and persistent accumulation in CTLA-4-expressing tissues, which will enable researchers further insight into CTLA-4 targeted therapies in the future.

Abstract B33: Loss of transcriptional fidelity in cancers confers immunotherapy resistance

Abstract Most cancers are immunogenic, either due to neo-antigenic mutational load that makes them susceptible to rejection by the adaptive immune system, or due to oncogenic stress pathways that makes them vulnerable to innate anti-tumor responses. The therapeutic strategies to reactivate the host anti-tumor immunity have a great promise for cancer therapy. However, despite the unprecedented promise of a cure and durable disease management in select patients, the response rates are still low in advanced cases, most of which also relapse. These findings reflect the multitude of mechanisms of tumor cell evasion of anti-tumor immunity, and that mechanisms beyond inactivation of local lymphocyte infiltrates might also play a role. Through comprehensive computational and follow-up experimental validations, we have found that a subset of cancers (~15-20% of all cancers) is characterized by severe defects in almost the entire epigenetic and transcriptional apparatus, resulting in genome-wide deregulation of histone modifications, mRNA transcription elongation, splicing and processing (Loss of Transcriptional Fidelity: LTF). LTF impaired the transcription of long genes in the genome at both mRNA and protein levels; and the pathways that are primarily regulated by long genes, such as immune-related (FasL response, TNF/NF-kB signaling, interferon signaling), MAP kinase and tyrosine kinase signaling pathways, were significantly suppressed in LTF+ (i.e. those with LTF) tumors. We validated the LTF phenotype and associated epigenetic and transcriptional defects in some cancer cell lines, and showed that severe loss of transcriptional fidelity can confer resistance to pro-inflammatory anti-tumor mechanisms in vitro, and suppress immune-mediated tumor rejection in vivo. As such, we found that LTF predicted poor response to immunotherapeutic, but not to chemo- or targeted therapy, agents in the clinic, including immune checkpoint inhibitors, in 3 different cohorts. Therefore, LTF is a previously unknown global phenotype in cancer cells that confers cell-autonomous resistance to anti-tumor immune attacks. Tumor lymphocyte infiltration is one of the best markers of immunotherapy response in the clinic. However, LTF+ tumors were characterized by a higher rate of immune cell infiltration, but paradoxically, less immune-mediated local tumor cell lysis, further supporting the notion that LTF is a tumor cell-autonomous mechanism of immune resistance. As such, combining tumor lymphocyte infiltration with LTF had superior power in predicting the progression-free and overall survival of melanoma patients treated with the anti-CTLA4 antibody ipilimumab. This study uncovers a major phenotype in cancers that dictates global transcriptional and signaling state in the cell, and response to immunotherapeutic agents in the clinic. Further, this study warrants assessment of markers of LTF in immunotherapy-candidate patients, especially given that LTF+ kidney cancer patients had significantly better response to targeted therapy agents. Citation Format: Navneet Singh, Vishnu Modur, Vakul Mohanty, Kwangmin Choi, Edith M. Janssen, Lisa Privette-Vinnedge, Gang Huang, Kakajan Komurov. Loss of transcriptional fidelity in cancers confers immunotherapy resistance. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr B33.