anti-CTLA4 Antibody Research Articles

Abstract 3805: Expression of tryptophan -2, 3-dioxygense (TDO) in metastatic uveal melanoma

Abstract Uveal (eye) melanoma (UM) is the most common primary eye malignancy in adults. Despite effective treatments for primary UM, up to 50% of patients subsequently develop systemic metastasis, predominantly in the liver. Once hepatic metastasis develops, the survival of UM patients is generally short and currently available treatments fail to show meaningful improvement of their survival. Metastatic uveal melanoma (MUM) is highly resistant to traditional systemic therapies, including immunotherapy. Immune checkpoint blockades approved for metastatic cutaneous melanoma (MCM) such as anti-CTLA4 antibody and anti-PD-1 antibody have shown only marginal clinical benefit in MUM (response rates <5%). We have reported that, while PD-1 expression was seen in both MCM and MUM, there was a stark difference in PD-L1 expression between these two types of melanoma (MCM vs. MUM, 20.8% vs. 0%) (ASCO 2016, A Javed, et al). It is of note that, of 6 MCM specimens obtained from hepatic metastasis, none expressed PD-L1. These results indicate the presence of unique immune microenvironment in the liver, harboring melanoma metastasis. One of the factors dominant in the liver is tryptophan 2,3-dioxygenase (TDO). TDO and indoleamine 2,3-dioxygenase (IDO) catalyze tryptophan and produce kynurenine, a metabolite that reportedly inhibits anti-tumor T cell immune responses. Recent studies have revealed that TDO is constitutively expressed in a wide variety of cancer cells. Investigation on TCGA data indicates expression of TDO2 in 62% of primary UM. 42% of samples showed increased TDO2 expression (RPKM >= 1 RPKM), while TDO2 message is not present in 1/3 of the samples. Expression of TDO2 in primary UM correlated to poor survival (Cox regression hazard ratio 0.7, p=0.04). Moreover, TDO2 expression correlated to patients with BAP1 mutations (p=0.00071) and differences between patients with monosomy 3 and disomy 3 (p=0.00017). We further investigated whether MUM cell lines and MUM tumor specimens express TDO. We detected TDO protein in all of 4 MUM cell lines by Western blotting. Although inducible by exogenous IFN-gamma, IDO1 protein was not detected in any of these MUM cell lines without stimulation. TDO mRNA was increased 3.5 fold by stimulating MUM cells with recombinant human TNF-alpha. All MUM cell lines possess TNF-alpha receptors. We have also investigated TDO and IDO1 proteins in 10 MUM specimens obtained from hepatic metastasis by immuno-histochemical staining. TDO was positive in both normal hepatocytes as well as tumor themselves in all MUM specimens. Interestingly, the intensity of TDO staining is much stronger in MUM, compared to the surrounding liver tissues. On the other hand, IDO1 protein was not positive in any of MUM tissues obtained from liver metastasis. These results indicate that expression of TDO by MUM cells might be one of the key mechanisms for escape from T-cell immune surveillance in hepatic metastasis from primary UM. Citation Format: Mizue Terai, Emma Link, Eric Link, Bao Lam, Marlana Orloff, Takami Sato. Expression of tryptophan -2, 3-dioxygense (TDO) in metastatic uveal melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3805.

Abstract 48: Targeting HDAC6 to reduce the aggressiveness of metastatic breast cancer in immunotherapy

Abstract Histone modifiers are recognized to perform diverse functions above beyond their conventional roles in remodeling the chromatin landscape. These functionalities range from regulating the outcomes of cellular-health to systemic immune-diseases, e.g., autoimmunity and cancer, positioning the HDAC inhibitors at a crucial junction of immunotherapy. However, the toxicity from the broad-spectrum HDAC-inhibitors has deemed a better focus on inhibitors of individual HDAC-members associated with tumor progression. One such member is HDAC6 which was earlier reported to promote the pro-tumorigenic STAT3 pathway. By using pharmacological inhibitor of HDAC6, the downstream immune-modulatory pathways of STAT3 could be targeted, which directly link to T-cell mediated immunity through the co-stimulatory molecules PD-L1, PD-L2 and B7-H4. This relationship has been established in a wide variety of tumors, including melanoma and breast cancer. HDAC6 has been also involved in a number of structural functions related to cellular motility, shape and intracellular transport through the regulation of the acetylation of numerous targets, including tubulin and cortactin. This function is strongly suggestive of HDAC6 being a key player in metastatic cancer progression. In our initial studies, we observed that the selective HDAC6 inhibitor Nexturastat A (NextA) is capable of reducing the tumor growth in a highly aggressive murine mammary carcinoma that mimics certain features of the human triple negative breast cancer, under both orthotopic and subcutaneous conditions of implantation. NextA was also able to inhibit tumor cell invasion in presence of metastasis-promoting cytokine such as IL6, as investigated through in vitro invasion assays. Additionally, we observed that the size and number of secondary tumor nodules in lungs were significantly diminished after the HDAC6i treatment. In order to boost the anti-tumor T-cell response, we also tested check-point inhibitors, such as anti PD1 and CTLA4 antibodies against both metastatic breast cancer and melanoma. While both of the standalone treatments showed a certain degree of success in reducing tumor growth, we demonstrated that HDAC6i improves anti-tumor immune responses when combined with immune check-point blockade mediated by anti PD1 antibody. The enhancement in anti-tumor response was measured in terms of the composition of infiltrating immune cells as well as functionality of effector T cells in terms of intra-tumoral interferon gamma expression. In both respects we found that NextA alone and combined with check-point blockade improves the anti-tumor response. Citation Format: Debarati Banik, Melissa Hadley, Erica Palmer, Vincent Gallub, Eduardo Sotomayor, Alan Kozikowski, Alejandro Villagra. Targeting HDAC6 to reduce the aggressiveness of metastatic breast cancer in immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 48.

Abstract 4940: Nonredundant roles for immune checkpoint blockade and agonistic CD40 in mediating T-cell responses in pancreatic ductal adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDA) is a highly aggressive cancer that is resistant to most treatments, with a five-year survival rate of ~10%. Immune checkpoint blockade (ICB) has had dramatic effects in many tumor histologies, but is ineffective in PDA. CD40 lies upstream of the immune checkpoints in the T-cell activation pathway, presenting a unique opportunity to intercede with T-cell activation independently of ICB. We hypothesized that administering agonistic CD40 antibody would prime effector T-cell populations, synergizing with ICB to provide therapeutic benefit in PDA. We administered agonistic CD40 monoclonal antibody (clone FGK45, anti-CD40) combined with anti-PD1 and anti-CTLA4 monoclonal antibodies (ICB) to mice bearing subcutaneous PDA tumors established using syngeneic tumor cell lines derived from the KrasG12D+/-;Trp53R172H+/-;Pdx-1 Cre (KPC) genetically engineered mouse model of PDA. While tumor regressions were rare in mice treated with ICB or anti-CD40 alone (1/7 mice in each group), 100% of mice treated with ICB + anti-CD40 experienced tumor regressions (7/7 mice). Cell depletion experiments showed early tumor regressions depended primarily on CD4 T cells, although both CD4 and CD8 T cells were required for long-term remission. 50% of mice (4/8) treated with ICB + anti-CD40 remained tumor-free (median survival 112 days) and 3/4 mice resisted tumor rechallenge, indicative of a long-lived memory T-cell response against PDA. Treatment with ICB + anti-CD40, but neither alone, increased the total intratumoral CD3+ T-cell population 3.8-fold (p<0.01), with increases in both the CD4+ and CD8+ T-cell compartments (6.7-fold and 3.3-fold, respectively, p <0.016). CD40 stimulation, but not ICB, modulated the CD4 compartment in the TME, increasing the proportion of CD43+CD11a+ antigen-specific CD4 T helpers (41 - 43% v. 10%, +/-ICB v. control, p <0.03) and reducing FoxP3+ CD4+ T regulatory cells (Tregs) 2.7 to 3.7-fold (+/- ICB, p < 0.0001). This resulted in an increased ratio of CD8 T effector cells to Tregs (7.5 to 10.7 CD8/Treg, anti-CD40 +/-ICB, p<0.01) specifically after treatment with anti-CD40, regardless of ICB addition. ICB alone increased the proportion of proliferating CD8 T cells in the tumor draining lymph node that were ‘"reinvigorated" Eomes+Tbet-Ki67+ (17-19% +/- CD40 v. 8% control, p <0.01), but was unable to increase the same CD8 T-cell population in the tumor. However, the addition of CD40 to ICB reduced the frequency of PD1+ CD8 T effectors in the tumor (25% v. 52% control, p < 0.05), suggesting a tumor-specific benefit of ICB on the exhausted T-cell compartment. These studies reveal the nonredundant roles that agonistic CD40 and ICB play in generating a robust T-cell response against PDA, and highlight the clinical potential of combining CD40 activation with ICB as a novel therapeutic approach in ICB-resistant tumors. Citation Format: Alexander H. Morrison, Katelyn T. Byrne, Robert H. Vonderheide. Nonredundant roles for immune checkpoint blockade and agonistic CD40 in mediating T-cell responses in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4940.

Abstract 959: Extracellular matrix-binding immunotherapies show enhanced antitumor efficacy and reduced adverse events

Abstract Immune checkpoint inhibitors (CPI) and co-stimulatory agonist antibody therapies have exhibited considerable antitumor effects, but instances of severe side effects have been previously reported. We hypothesized that conjugation of an extracellular matrix (ECM)-binding peptide derived from placenta growth factor-2 (PlGF-2123-144) to CPI (combination of anti-CTLA4 antibody (αCTLA4) and αPD-L1) or agonistic αCD40 would accomplish local cancer immunotherapy, minimizing the antibodies' systemic exposure. Here, we show that enhanced tissue retention and lower antibody concentrations in blood plasma resulted from PlGF-2123-144 conjugation when the antibodies were administered peri-tumorally compared to unmodified antibodies administered by the same route at the same dose. This resulted in decreases in systemic cytokine release in the blood serum, and in liver tissue damage, as was assessed both biochemically and histologically, indicating lower systemic side effects after CPI and αCD40 therapies. Particularly, we show that PlGF-2123-144 conjugation reduces the risks of αPD-L1-induced autoimmune diabetes in the male nonobese diabetic mouse. Because PD-1/PD-L1-inhibition induced diabetes has been reported in the clinic, this supports the idea that PlGF-2123-144 conjugation to antibodies may reduce adverse events. This observation with localized PlGF-2123-144-antibodies could be an important breakthrough in treating patients who have discontinued immunotherapy due to the associated side effects. Regarding efficacy, we show that either PlGF-2123-144-CPI treatment or PlGF-2123-144-αCD40 treatment showed significantly higher antitumor activity compared to unmodified forms in multiple cancer models: B16F10 and Tyr:Cre-ER+/LSL-BrafV600E/Ptenfl/fl melanoma, CT26 colon carcinoma, and MMTV-PyMT breast cancer. Local injections of PlGF-2123-144-CPI increased the number of activated CD8+ and CD4+ T cells within the tumor, compared to normal CPI. PlGF-2123-144-αCD40 treatment increased the frequency of activated dendritic cells in the tumor-draining lymph node, activated CD8+ T cells within the tumor, and secretion of endogenous antibodies against tumor cells. This immune cell activation resulted in growth suppression of a distant tumor. These data suggest the feasibility of treating patients with oligometastatic tumors by administration of PlGF-2123-144- PlGF-2123-144-CPI or PlGF-2123-144-αCD40 into one accessible metastasis. Our data suggest that local injection of either PlGF-2123-144-CPI or PlGF-2123-144-αCD40 efficiently activates tumor antigen-specific T cells while maintaining systemic immune homeostasis by avoiding influencing nontumor antigen-specific T cells. This simple approach of engineered ECM-binding immunotherapy antibodies may be clinically useful. Citation Format: Jun Ishihara, Ako Ishihara, Kazuto Fukunaga, Lambert Potin, Peyman Hosseinchi, Melody A. Swartz, Jeffrey A. Hubbell. Extracellular matrix-binding immunotherapies show enhanced antitumor efficacy and reduced adverse events [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 959.

New developments in systemic therapy for advanced biliary tract cancer.

Biliary tract cancer, carcinoma of the extrahepatic bile ducts, carcinoma of the gall bladder, ampullary carcinoma and intrahepatic cholangiocarcinoma are often identified at an advanced stage and have poor prognoses. Although effective chemotherapy regimens are needed, their development remains unsatisfactory. From the results of a phase III clinical trial (ABC-02 trial), gemcitabine plus cisplatin is the standard first-line chemotherapeutic regimen for advanced biliary tract cancer. A phase III trial of gemcitabine plus cisplatin vs. gemcitabine plus S-1 therapy (FUGA-BT) demonstrated the non-inferiority of gemcitabine plus S-1 to gemcitabine plus cisplatin. A phase III trial of gemcitabine plus cisplatin vs. gemcitabine plus cisplatin plus S-1 (MITSUBA) was conducted, and the report on the results of the final analysis is being awaited. A standard second-line chemotherapeutic regimen has not yet been established. Fluoropyrimidines are frequently used in clinical practice. Despite many clinical trials being conducted with molecular targeted agents including erlotinib, cetuximab, panitumumab, bevacizumab, sorafenib, cediranib, trametinib and vandetanib, no agent has shown to be effective for advanced biliary tract cancer. Next-generation sequencing shows great promise by allowing rapid mutational analysis of multiple genes in human cancers, and attractive driver genetic alterations have been reported in biliary tract cancer. FGFR2 fusion gene, mutations of IDH1/2, BRAF, BRCA1/2, ATM, PIK3CA and overexpression of c-MET and HER2/neu are reported relatively frequently and are interesting targets. Therefore, future development in precision medicine utilizing next-generation sequencing is expected. Although the efficacy of immune checkpoint inhibitors, such as anti-PD-1, anti-PD-L1 and anti-CTLA4 antibodies, remains unknown at present, basic data and results of ongoing clinical trials are anticipated.

Cost of inpatient admissions for immune-related adverse effects from immune checkpoint inhibitor therapy: A single center experience.

3060Background: Immune checkpoint inhibitors such as anti-CTLA4 and anti-PD1 antibodies represent a paradigm shift in the treatment of many advanced malignancies. However, immune related adverse ef...

Metabolic therapy with PEG-arginase induces a sustained complete remission in immunotherapy-resistant melanoma

BackgroundMetastatic melanoma is an aggressive skin cancer with a poor prognosis. Current treatment strategies for high-stage melanoma are based around the use of immunotherapy with immune checkpoint inhibitors such as anti-PDL1 or anti-CTLA4 antibodies to stimulate anti-cancer T cell responses, yet a number of patients will relapse and die of disease. Here, we report the first sustained complete remission in a patient with metastatic melanoma who failed two immunotherapy strategies, by targeting tumour arginine metabolism.Case presentationA 65-year-old patient with metastatic melanoma who progressed through two immunotherapy strategies with immune checkpoint inhibitor antibodies was enrolled in a phase I study (NCT02285101) and treated with 2 mg/kg intravenously, weekly pegylated recombinant arginase (BCT-100). The patient experienced no toxicities > grade 2 and entered a complete remission which is sustained for over 30 months. RNA-sequencing identified a number of transcriptomic pathway alterations compared to control samples. The tumour had absent expression of the recycling enzymes argininosuccinate synthetase (ASS) and ornithine transcarbamylase (OTC) indicating a state of arginine auxotrophy, which was reconfirmed by immunohistochemistry, and validation in a larger cohort of melanoma tumour samples.ConclusionsTargeting arginine metabolism with therapeutic arginase in arginine auxotrophic melanoma can be an effective salvage for the treatment of patients who fail immunotherapy.

Tremelimumab combined with durvalumab in patients with mesothelioma (NIBIT-MESO-1): an open-label, non-randomised, phase 2 study

Tremelimumab, an anti-CTLA4 monoclonal antibody, initially showed good activity when used alone in patients with mesothelioma, but did not improve the overall survival of patients who failed on first-line or second-line chemotherapy compared with placebo in the DETERMINE study. We aimed to investigate the efficacy and safety of first-line or second-line tremelimumab combined with durvalumab, an anti-PD-L1 monoclonal antibody, in patients with malignant mesothelioma. In this open-label, non-randomised, phase 2 trial, patients with unresectable pleural or peritoneal mesothelioma received intravenous tremelimumab (1 mg/kg bodyweight) and durvalumab (20 mg/kg bodyweight) every 4 weeks for four doses, followed by maintenance intravenous durvalumab at the same dose and schedule for nine doses. The primary endpoint was the proportion of patients with an immune-related objective response according to the immune-related modified Response Evaluation Criteria in Solid Tumors (RECIST; for pleural mesothelioma) or immune-related RECIST version 1.1 (for peritoneal mesothelioma). The primary analysis was done by intention to treat, whereas the safety analysis included patients who received at least one dose of study drug. This trial is registered with the European Clinical Trials Database, number 2015-001995-23, and ClinicalTrials.gov, number NCT02588131, and is ongoing but no longer recruiting patients. From Oct 30, 2015, to Oct 12, 2016, 40 patients with mesothelioma were enrolled and received at least one dose each of tremelimumab and durvalumab. Patients were followed-up for a median of 19·2 months (IQR 13·8-20·5). 11 (28%) of 40 patients had an immune-related objective response (all partial responses; confirmed in ten patients), with a median response duration of 16·1 months (IQR 11·5-20·5). 26 (65%) patients had immune-related disease control and 25 (63%) had disease control. Median immune-related progression-free survival was 8·0 months (95% CI 6·7-9·3), median progression-free survival was 5·7 months (1·7-9·7), and median overall survival was 16·6 months (13·1-20·1). Baseline tumour PD-L1 expression did not correlate with the proportion of patients who had an immune-related objective response or immune-related disease control, with immune-related progression-free survival, or with overall survival. 30 (75%) patients experienced treatment-related adverse events of any grade, of whom seven (18%) had grade 3-4 treatment-related adverse events. Treatment-related toxicity was generally manageable and reversible with protocol guidelines. The combination of tremelimumab and durvalumab appeared active, with a good safety profile in patients with mesothelioma, warranting further exploration. Network Italiano per la Bioterapia dei Tumori Foundation, Associazione Italiana per la Ricerca sul Cancro, AstraZeneca, and Istituto Toscano Tumori.

Pharmacometric Applications and Challenges in the Development of Therapeutic Antibodies in Immuno-Oncology.

Monoclonal antibodies targeting key checkpoints in immune stimulatory pathways have over the last years become the mainstay of cancer immunotherapy. This article provides a brief review of the application and key impact of pharmacometrics and quantitative clinical pharmacology approaches in the development of these novel biologics. The clinical development and selection of optimal dosing regimens for monoclonal antibodies used in immune-oncology has been facilitated by an extensive application of pharmacometric approaches to characterize the exposure-response relationship for major efficacy and safety endpoints. These analysis techniques were applied for the anti CTLA-4 antibody ipilimumab, as well as the anti PD1/PD-L1 antibodies nivolumab, pembrolizumab, avelumab, atezolizumab and durvalumab. The utilization of quantitative clinical pharmacology, including model-based analyses, did not only support the identification of efficacious doses with acceptable safety limits, but was also able to address complicating challenges such as time- and response-dependent changes in antibody clearance as observed for most compounds. A widespread and systematic application of pharmacometric approaches has provided key aspects in elucidating, interpreting and integrating preclinical, biochemical and clinical data in support of the development of safe and efficacious dosing regimens of monoclonal antibodies used in immuno-oncology, thereby facilitating the clinical use of this promising new class of biologics in cancer patients with unmet medical needs.

Discovery and preclinical characterization of the antagonist anti-PD-L1 monoclonal antibody LY3300054

BackgroundModulation of the PD-1/PD-L1 axis through antagonist antibodies that block either receptor or ligand has been shown to reinvigorate the function of tumor-specific T cells and unleash potent anti-tumor immunity, leading to durable objective responses in a subset of patients across multiple tumor types.ResultsHere we describe the discovery and preclinical characterization of LY3300054, a fully human IgG1λ monoclonal antibody that binds to human PD-L1 with high affinity and inhibits interactions of PD-L1 with its two cognate receptors PD-1 and CD80. The functional activity of LY3300054 on primary human T cells is evaluated using a series of in vitro T cell functional assays and in vivo models using human-immune reconstituted mice. LY3300054 is shown to induce primary T cell activation in vitro, increase T cell activation in combination with anti-CTLA4 antibody, and to potently enhance anti-tumor alloreactivity in several xenograft mouse tumor models with reconstituted human immune cells. High-content molecular analysis of tumor and peripheral tissues from animals treated with LY3300054 reveals distinct adaptive immune activation signatures, and also previously not described modulation of innate immune pathways.ConclusionsLY3300054 is currently being evaluated in phase I clinical trials for oncology indications.

Structure-function analysis and therapeutic efficacy of antibodies to fungal melanin for melanoma radioimmunotherapy

Metastatic melanoma remains difficult to treat despite recent approvals of several new drugs. Recently we reported encouraging results of Phase I clinical trial of radiolabeled with 188Re murine monoclonal IgM 6D2 to melanin in patients with Stage III/IV melanoma. Subsequently we generated a novel murine IgG 8C3 to melanin. IgGs are more amenable to humanization and cGMP (current Good Manufacturing Practice) manufacturing than IgMs. We performed comparative structural analysis of melanin-binding IgM 6D2 and IgG 8C3. The therapeutic efficacy of 213Bi- and 188Re-labeled 8C3 and its comparison with anti-CTLA4 immunotherapy was performed in B16-F10 murine melanoma model. The primary structures of these antibodies revealed significant homology, with the CDRs containing a high percentage of positively charged amino acids. The 8C3 model has a negatively charged binding surface and significant number of aromatic residues in its H3 domain, suggesting that hydrophobic interactions contribute to the antibody-melanin interaction. Radiolabeled IgG 8C3 showed significant therapeutic efficacy in murine melanoma, safety towards healthy melanin-containing tissues and favorable comparison with the anti-CTLA4 antibody. We have demonstrated that antibody binding to melanin relies on both charge and hydrophobic interactions while the in vivo data supports further development of 8C3 IgG as radioimmunotherapy reagent for metastatic melanoma.

Tolerance and outcomes of stereotactic radiosurgery combined with anti-programmed cell death-1 (pembrolizumab) for melanoma brain metastases.

Anti-programmed cell death-1 (anti-PD1) antibodies are currently the first-line treatment for patients with metastatic BRAF wild-type melanoma, alone or combined with the anti-CTLA4 monoclonal antibody, ipilimumab. To date, data on safety and the outcomes of patients treated with the anti-PD1 monoclonal antibodies, pembrolizumab (PB), or nivolumab, combined with stereotactic radiosurgery (SRS), for melanoma brain metastases (MBM) are scarce. We retrospectively reviewed all patients with MBM treated with PB combined with SRS between 2012 and 2015. The primary endpoint was neurotoxicity. The secondary endpoints were local, distant intracranial controls and overall survival (OS). Among 74 patients with MBM treated with SRS, 25 patients with a total of 58 MBM treated with PB combined with SRS within 6 months were included. Radiation necrosis, occurring within a median time of 6.5 months, was observed for four MBM (6.8%) in four patients. No other significant SRS-related adverse event was observed. After a median follow-up of 8.4 months, local control was achieved in 46 (80%) metastases and 17 (68%) patients. Perilesional oedema and intratumour haemorrhage appearing or increasing after SRS were associated with local progression (P<0.001). The median OS was 15.3 months (95% confidence interval: 4.6-26). The timing between SRS and PB administration did not seem to influence the risk of radiation necrosis, intracranial control or OS. SRS combined with PB was well tolerated and achieved local control in 80% of the lesions. Prolonged OS was observed compared with that currently yielded in this population of patients. Prospective studies are required to explore further the optimal ways to combine immunotherapy and SRS.

Management of gastrointestinal adverse events induced by immune-checkpoint inhibitors

Immune-checkpoint inhibitors (ICIs) have been proven promising for advanced cancers, and they are characterized by a unique treatment-related adverse event (AE) spectrum. Toxicity of the gastrointestinal (GI) tract is one of the most common AEs and often results in discontinuation of ICIs. Since most of the current studies have focused on the incidence, characteristics, and management of colitis, very little is known about other types of GI AEs. Herein, we review the available relevant literature on upper and lower GI toxicities, and present an algorithm for GI AE management based on the existing evidence and our clinical experience. Nausea and decreased appetite are the most common upper GI AEs, and gastric bleeding has been observed. Glucocorticoids are not recommended for upper GI bleeding and should be carefully used for cases without bleeding. Diarrhea and colitis are the most common lower GI AEs characterized by inflammation of the mucosa, and high-dose glucocorticoids with other immunomodulators are recommended as salvage treatments. Constipation and paralytic bowel obstruction caused by dysfunction of the GI tract are less frequent and respond well to medications promoting bowel movements. Severe GI AEs should be managed by a multidisciplinary team based on a comprehensive assessment of disease severity. Further clinical trials are warranted to investigate the optimal management of GI AEs.

Systemic treatments for metastatic cutaneous melanoma.

Systemic treatments for metastatic cutaneous melanoma.

Autoimmune hypophysitis

A 82-year-old male patient with metastatic lung adenocarcinoma presented to the outpatient clinic at the University of Texas MD Anderson Cancer Center (Houston, TX, USA) in April, 2015 with worsening fatigue, headache, dizziness, blurry vision, and nausea. He had received treatment with an immune checkpoint inhibitor, ipilimumab (an anti CTLA-4 antibody) 4 weeks before presentation. A brain MRI showed a diffuse pituitary enlargement in the T1-weighted coronal section (figure, A) and sagittal section (figure, B), with increased thickening of the pituitary stalk and enhancement of adjacent dura, suggestive of hypophysitis. The endocrine workup was consistent with hypophysitis with a central adrenal insufficiency, central hypothyroidism and hypogonadism, but with intact posterior pituitary function. The patient's symptoms improved significantly with initial high-dose corticosteroids (prednisone 60 mg daily) and supplementation of the affected hormones, and the follow-up brain MRI after 1 month showed a normal-sized pituitary gland.

Toward Precision Radiotherapy for Use with Immune Checkpoint Blockers.

The first evidence that radiotherapy enhances the efficacy of immune checkpoint blockers (ICB) was obtained a dozen years ago in a mouse model of metastatic carcinoma refractory to anti-CTLA-4 treatment. At the time, ICBs had just entered clinical testing, an endeavor that culminated in 2011 with the approval of the first anti-CTLA-4 antibody for use in metastatic melanoma patients (ipilimumab). Thereafter, some patients progressing on ipilimumab showed systemic responses only upon receiving radiation to one lesion, confirming clinically the proimmunogenic effects of radiation. Preclinical data demonstrate that multiple immunomodulators synergize with radiotherapy to cause the regression of irradiated tumors and, less often, nonirradiated metastases. However, the impact of dose and fractionation on the immunostimulatory potential of radiotherapy has not been thoroughly investigated. This issue is extremely relevant given the growing number of clinical trials testing the ability of radiotherapy to increase the efficacy of ICBs. Recent data demonstrate that the recruitment of dendritic cells to neoplastic lesions (and hence the priming of tumor-specific CD8+ T cells) is highly dependent on radiotherapy dose and fractionation through a mechanism that involves the accumulation of double-stranded DNA in the cytoplasm of cancer cells and consequent type I IFN release. The molecular links between the cellular response to radiotherapy and type I IFN secretion are just being uncovered. Here, we discuss the rationale for an optimized use of radiotherapy as well as candidate biomarkers that may predict clinical responses to radiotherapy combined with ICBs. Clin Cancer Res; 24(2); 259-65. ©2017 AACR.

Abstract LB-B33: Nonclinical safety evaluation of two distinct second generation variants of anti-CTLA4 monoclonal antibody, ipilimumab, in monkeys

Abstract Ipilimumab is a fully human immunoglobulin G1 (IgG1) monoclonal antibody against cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), an inhibitory receptor expressed on activated effector T cells and regulatory T cells (Treg), that inhibits the binding of CTLA4 to B7 ligands. BMS-986218 and BMS-986249 are second generation molecules that share the same amino acid sequence and ligand blocking properties as ipilimumab, but are mechanistically distinct. BMS-986218 is non-fucosylated (NF) and has an increased affinity for the activating Fcγ receptor (FcγR, CD16) affording the possibility of increased anti-tumor activity via depletion of Treg in the tumor. In contrast, BMS-986249 is a Probody™ of ipilimumab that has a masking peptide covering the active antigen-binding site of the antibody which is clipped by specific proteases within tumors, exposing the fully active antibody, and potentially offering reduced systemic toxicity liabilities with comparable efficacy to ipilimumab. In 1-month toxicity studies in monkeys (n = 5/sex/group) at weekly doses of 3, 15, or 75 mg/kg IV of BMS-986218 or 10 or 50 mg/kg IV of BMS-986249 or ipilimumab, profound enhancement of peripheral T-cell activation occurred in a dose-dependent manner for all 3 compounds following neoantigen immunization (keyhole limpet hemocyanin [KLH], HIV necessary and enforcing factor [Nef], and HIV group specific antigen [Gag] peptides), consistent with target pharmacology. Consistent with the intended mechanistic differences, peripheral T cell activation was generally increased at corresponding doses of BMS-986218 compared to ipilimumab, and was delayed and reduced in monkeys given BMS-986249. BMS-986218, ipilimumab, and BMS-986249 were clinically tolerated by monkeys at doses up to 3, 10, and 50 mg/kg, respectively, with generally mild, loose feces in some monkeys and/or minimal body weight decrease. At higher doses, early euthanasia occurred for 1 and 6 monkeys at 15 and 75 mg/kg BMS-986218, respectively, from Days 22-53 and 1 monkey at 50 mg/kg ipilimumab on Day 55 due to profound clinical toxicity. The predominant microscopic finding was generally dose-related lymphohistiocytic inflammation within a variety of tissues at all doses for all compounds, with BMS-986218 resulting in the greatest incidence, severity, and distribution of tissues and BMS-986249 having the least effects. The GI tract (stomach, cecum, and colon) and the kidney were the most severely and consistently affected, whereas additional organs were affected at higher doses. Most changes were partially or fully reversible during an 8-week recovery period with the exceptions of one monkey at 75 mg/kg BMS-986218 and one monkey at 50 mg/kg ipilimumab that were euthanatized on Days 53 or 55 due to unresolved GI toxicity, persistent lymphohistocytic inflammation, and/or unchanged or progressive increases in AST and ALT. Based on the tolerability and generally mild severity of lymphohistiocytic tissue inflammation, the highest non-severely toxic doses (HNSTD) for BMS-986218, ipilimumab, and BMS-986249 in monkeys following 1 month of dosing were 3 mg/kg (mean AUC 0-168h = 11,300 μg•h/mL), 10 mg/kg (AUC[0-168h] =44,600 µg·h/mL), and 50 mg/kg (AUC[0-168h] =205,000 µg·h/mL), respectively. Overall, these results support the potential of these 2nd generation anti-CTLA4 antibodies to offer an improved risk /benefit profile with increased activity of the NF variant and improved safety of the Probody™ relative to ipilimumab. Citation Format: Karen D. Price, Frank Simutis, Anthony Fletcher, Lila Ramaiah, Rima Srour, John Kozlosky, Jean Sathish, John Engelhardt, Annette Capozzi, James Crona, Courtni Newsome, Jennifer Wheeler, Daniel Szatkowski, Austin Thekkumthala, Bojing Wang, Wendy Freebern, Helen Haggerty, Todd Bunch, Michael Graziano. Nonclinical safety evaluation of two distinct second generation variants of anti-CTLA4 monoclonal antibody, ipilimumab, in monkeys [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 LB-B33.

Abstract A199: Association of immune checkpoint inhibitor dose and survival in phase I clinical trials: is it time to redefine the recommended phase II dose

Abstract Background: Since the era of cytotoxic chemotherapy, the maximum tolerated dose (MTD) in a phase I trial has represented the recommended phase II dose and often the initial FDA-approved dose. This dosing recommendation stems from data that cytotoxic chemotherapy is most effective at the MTD. Unlike chemotherapy, immune checkpoint inhibitor therapy is not directly cytotoxic and harnesses the host immune system’s T cell to target tumor cell kill. Whether higher doses are associated with survival in immune checkpoint inhibitor phase I trials remains unknown. Purpose: To evaluate whether dose of immune checkpoint inhibitor administered in a phase I trial is associated with progression-free survival and overall survival. Methods: We analyzed clinical data from patients treated in phase I immune checkpoint inhibitor dose-escalation trials (anti-CTLA4 antibody and anti-PD1 trials) at the MD Anderson Center for Targeted Therapy. Patients were stratified into a low-dose (≤33% MTD), medium-dose (34-66% MTD), high-dose (67-100% MTD), or very-high-dose (≥101% MTD) group. Groups were compared for progression-free survival and overall survival. Results: Among 91 patients treated in a dose-escalation immune checkpoint inhibitor phase I trial (58 CTLA4- and 33 PD1-based) between January 2013 and November 2015, the median age was 59 years (range: 20-86 years) and 37 (41%) were females. The most common tumor types treated included renal cell carcinoma (n = 23; 25%), melanoma (n = 16; 18%), sarcoma (n = 10; 11%), gastrointestinal stromal tumors (n = 10; 11%), and non-small cell lung cancer (n = 4; 4%). Progression-free survival in the low-dose group (n=16) was 2.76 months (95% CI 1.48-NA), medium-dose group (n=21) was 2.76 months (95% CI 1.48-NA), high-dose group (n=36) was 2.46 months (95% CI 1.84-3.29), and very-high-dose group (n=17) was 3.68 months (95% CI 2.76-NA). Log rank p=0.22. Overall survival in the low-dose group was 6.18 months (95% CI 3.45-NA), medium-dose group was 17.05 months (95% CI 3.94-NA), high-dose group was 5.16 months (95% CI 4.24-7.62), and very-high-dose group was 7.49 months (95% CI 5.59-NA). Log rank p=0.0070. Conclusion: We identify that in this subset of patients treated in dose-escalation immune checkpoint inhibitor phase I trials, administration of higher dose is not associated with improved progression-free survival but is associated with improved overall survival. Evaluation of dose with immune-related adverse events and prospective examination in a larger subset of patients is ongoing. These data may have implications for optimizing the recommended phase II dose for immune checkpoint inhibitor therapy and may alleviate patient concerns when receiving lower doses in phase I dose-escalation studies. Citation Format: Shiraj Sen, David S. Hong, Kenneth Hess, Funda Meric-Bernstam, Vivek Subbiah. Association of immune checkpoint inhibitor dose and survival in phase I clinical trials: is it time to redefine the recommended phase II dose [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 A199.

Abstract A003: Developing an AML mouse syngeneic model for combinatory chemotherapy and immunotherapy

Abstract Little progress has been made in treatment of acute myeloid leukemia (AML) for years. Following the success of immune checkpoint inhibitors in solid tumors, immunotherapy also offers huge promise in many hematologic malignancies, including AML. Anti-PD1 antibody is currently being investigated in combination with azacitidine in patients with relapsed AML. Other emerging immuno-oncology (I/O) therapeutics are also at different stages of preclinical research. However, we are lacking relevant animal models with intact immune system for the preclinical in vivo pharmacologic studies and mechanism-of-action analysis of I/O agents. To meet this need, we set out to develop a series of transplantable mouse AML models carrying Nras mutations and/or a set of clinical relevant fusion proteins, like AML1/ETO. Using a similar approach reported by Scott Lowe and colleagues (1), we constructed retroviral vectors expressing human AML1/ETO9a IRES GFP and NrasG12D, generated retroviruses, co-transduced the fetal liver cells, and performed syngeneic intravenous injections in C57BL/6 mice. The mice developed AML in the following months as the GFP-positive cells enriched as high as around 90% in PBMC. Leukemia cells also dominatde the spleen and bone marrow in moribund mice. The splenocytes from moribund AML1/ETO9a mice were banked and transplanted into new C57BL/6 mice for several rounds. The later passages were more malignant than the early passages. To validate the immune profiling of this model, FACS analysis was applied using mouse PD-L1, Gr-1, CD45, Mac-1, c-kit, and sca-1 antibodies for GFP-positive cells. In PBMC of moribund AML1/ETO9a mice, PD-L1 and c-kit were highly expressed, while the expression levels of Gr-1, CD45, Mac-1, and sca-1 were low. For efficacy test, we performed standard-of-care (SOC) assay with cytarabine, doxorubicin, sorafenib, and anti-PD1 antibody. The dosing started around 10 days post inoculation of 1 x 106 leukemia cells, when GFP-positive cells were 2-10%. While doxorubicin showed good response, cytarabine and sorafenib resulted in modest tumor growth inhibition, and anti-PD1 antibody failed to show any meaningful efficacy. We are currently testing more combinatory treatments, including anti-TIM3 and anti-CTLA4 antibodies. Taken together, we have developed a mouse AML model with clinical relevant mutations for preclinical efficacy assessment of combinatory chemotherapies, target therapies, and immunotherapies. Reference: 1. Zuber J, Radtke I, Pardee TS, et al. Mouse models of human AML accurately predict chemotherapy response. Genes Dev 2009. Citation Format: Xin Tang, Lily Tong, Annie Xiaoyu An, Likun Zhang, Jie Cai, Qian Shi, Jean Pierre Wery, Davy Xuesong Ouyang. Developing an AML mouse syngeneic model for combinatory chemotherapy and immunotherapy [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 A003.

Abstract B202: Covalent irreversible usp7 inhibitors for cancer immunotherapy

Abstract Tumors employ diverse strategies to suppress and evade the immune system’s ability to recognize and destroy tumor cells. Immune-suppressive Foxp3+ regulatory T cells (Tregs) in the tumor microenvironment correlate with poor prognosis in solid tumors. Therefore, selective depletion of tumor-associated Tregs or impairment of Treg function is considered an attractive cancer immunotherapy approach. The pro-tumorigenic deubiquitylase (DUB) USP7 is also essential for Treg functions. USP7 controls Treg function largely by regulating post-translational modification of Foxp3 and TIP60. Deletion of USP7 in Tregs results in impairment of Treg functions and autoimmunity in mice. Progenra has developed potent, selective covalent irreversible USP7 inhibitors that impair Treg functions ex vivo and in vivo. Most importantly, USP7 inhibitors exhibit robust antitumor activity against several syngeneic solid tumor models in immunocompetent mice. In addition, Progenra’s USP7 inhibitors enhance the efficacy of anti-PD1 antibody, anti-CTLA4 antibody, and cancer vaccines. These studies strongly suggest that USP7 inhibitors alone or in combination regimens can improve the efficacy and expand the scope of cancer immunotherapy. Citation Format: Suresh Kumar, Jian Wu, Feng Wang, Liqing Wang, Lee Chen, Ivan Sokirniy, Hui Wang, David Sterner, Charles Grove, Brigid Cunnion, Joseph Weinstock, Michael Mattern, Wayne Hancock. Covalent irreversible usp7 inhibitors for cancer immunotherapy [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 B202.