P222 Clinical trial in progress: A phase 1b trial of talimogene laherparepvec (T-VEC) in combination with dabrafenib and trametinib in advanced melanoma with an activating BRAF mutation
1University of Tennessee Health Science Center, Memphis, TN, USA, Memphis, TN, USA; 2West Cancer Center, Germantown, TN, USA, Germantown, TN, USA
Correspondence: Kenneth Byrd ([email protected])
Patients with BRAF-mutant advanced melanoma have been shown to respond at high rates to combination BRAF plus MEK inhibition. Response rates to single-agent immune therapies tend to be modest, but are often durable, while response rates to BRAF plus MEK inhibition tend to be high but transient. While early attempts at combining targeted and immune therapy resulted in dose-limiting hepatic toxicity, more recent attempts with newer agents have shown significant promise. T-VEC is an oncolytic viral immunotherapy which was designed to selectively replicate in tumors resulting in lytic cell death, antigen release, and production of GM-CSF to enhance systemic immune response. In a prior randomized, phase 3 study of T-VEC versus GM-CSF, durable response rate was statistically improved with T-VEC, with a strong trend towards improved overall survival. Dabrafenib and trametinib, inhibitors of BRAF and MEK, respectively, have been shown in combination to result in response rates of up to 75% and improvement in progression-free and overall survival compared to single-agent targeted therapy and chemotherapy. Combining T-VEC with dabrafenib and trametinib may further enhance antitumor immune responses in addition to preserving the targeted effect.
This is a Phase Ib, prospective, single arm study of T-VEC given in combination with standard doses of dabrafenib and trametinib in advanced melanoma with an activating BRAF mutation. The primary endpoint of the study is tolerability as measured by dose-limiting toxicities seen in the first 5 weeks of treatment. Key secondary endpoints include progression-free survival, objective response rate, change in tumor burden, time to response, and duration of response among responders. Tumor-level responses in injected and uninjected tumors, and characterization of immune markers in pre-study and on-study biopsies will be exploratory endpoints. Key eligibility criteria include unresectable stage IIIB-IV BRAF mutant melanoma, presence of measurable and injectable disease, no active cerebral metastases or autoimmune diseases, and any number of prior lines of therapy but no prior receipt of T-VEC. T-VEC (10 6 PFU/mL first dose, 10 8 PFU/mL subsequent doses) will be administered by intralesional injection into cutaneous, subcutaneous, or nodal lesions on week 1 day 1, week 4 day 1, and every 2 weeks thereafter until disappearance of injectable lesions, complete response, progressive disease, intolerance of study treatment, or 24 months after starting therapy, whichever occurs first. Dabrafenib and trametinib will be given until progression or intolerance. Twenty subjects are to be enrolled at a single U.S. institution.
P232 A pilot study to evaluate the clinical and immunological effects of incorporating a CD40-agonistic antibody into the multimodality treatment of resectable esophageal and GE junction cancers
Andrew H. Ko, Lawrence Fong
University of California San Francisco, San Francisco, CA, USA
Correspondence: Andrew H. Ko ([email protected]
Targeting CD40, a member of the TNF receptor superfamily found on antigen presenting cells (APCs), represents a promising cancer immunotherapeutic strategy. Activation of this costimulatory molecule results in improved antigen processing and presentation and cytokine release from activated APCs, enhancing T cell responses. Additionally, CD40 is expressed on many tumor cells that, when activated, results in tumor cell apoptosis and inhibition of tumor growth. APX005M (Apexigen, San Carlos, CA) is a humanized IgG1 anti-CD40 agonistic antibody that binds to CD40 with high affinity. In a FIH phase I clinical trial in patients with advanced solid tumors, APX005M was relatively well tolerated, with cytokine release syndrome (CRS) as the DLT at doses above the RP2D. Importantly, correlative studies show that APX005M produces dose-dependent activation of APCs, T cell activation, and increases in circulating cytokine levels.
This pilot trial represents the first to evaluate a CD40-agonistic antibody in esophageal/GE junction cancer, a disease in which IO agents (particularly PD-1 mAbs) have demonstrated promising activity. The study is also the first to explore combining IO with chemoradiation in the neoadjuvant setting, as this multimodality approach represents the standard of care for patients with resectable esophageal/GE junction cancer and is optimally conducive for serial tumor tissue acquisition. A total of 16 patients with resectable (uT1-3N0-1) squamous cell or adenocarcinoma of the esophagus or GE junction will be enrolled. Chemoradiation consists of radiation (5040cGy in 28 daily fractions) and low-dose carboplatin plus paclitaxel weekly x 5, as per standard of care. APX005M 0.3 mg/kg (1 dose level below single-agent MTD) is given every 3 weeks for a total of 4 doses, with the first dose administered two weeks prior to the initiation of concurrent chemoradiation. APX005M administration is offset by 2-3 days from chemotherapy to avoid the steroid premedication administered with paclitaxel. Tumor tissue is acquired via endoscopic biopsy at baseline and following the single-dose “run-in” of APX005M; and then again at esophagectomy, which occurs 1-2 months following completion of chemoradiation. Serial blood collections are also performed at multiple pre-defined timepoints. In addition to assessing the feasibility, safety, and preliminary efficacy (as measured by pathologic complete remission rate) of this novel combination, analyses of tumor tissue and blood will be performed, including Tissue Multiplex Immunohistochemistry and flow cytometry for both APC and T cell activation, as well as T cell receptor sequencing for T cell repertoire diversity.
P242 A phase 1 multicenter, dose escalation study of CBT-501, a novel anti-PD-1 inhibitor in subjects with select advanced or relapsed/recurrent solid tumors
Purvi Patel, Mamatha Reddy, Melissa Lopez, Neil Sankar, Sarath Kanekal, Mike Li, Sanjeev Redkar, Gavin Choy
CBT Pharmaceuticals, Inc., Pleasanton, CA, USA
Correspondence: Sanjeev Redkar ([email protected])
Programmed death-1 (PD-1, CD279) is an inhibitory co-receptor expressed on antigen-activated and exhausted T and B cells. PD-1/PD-L1 axis inhibition by targeted-antibodies, increases the T cell proliferation and cytotoxicity. This represents a promising mechanism to stimulate the anti-tumor activity of the immune system. CBT-501, genolimzumab (GB226) is a novel humanized IgG4 monoclonal antibody targeting the PD-1 membrane receptor on T lymphocytes and other cells of the immune system. CBT-501 demonstrated highly specific binding to PD-1 of human (Kd=505 pM) and cynomolgus (Kd=7.2 nM). CBT-501 efficiently inhibited the binding of PD-L1/L2 to PD-1 for both human and monkey and enhanced human T cell activation in the Mixed Lymphocyte Reaction (MLR) assay. CBT-501 has demonstrated anti-tumor activity in the in vivo animal model and no abnormal drug-related toxicity has been observed in the GLP toxicology studies. Data from all pre-clinical pharmacodynamics and toxicology studies of CBT-501 indicate pharmacological activity at effective doses with a wide margin of safety. Based on these findings, a Phase 1 study has been initiated with CBT-501 in Australia.
CBT-501-01 is a Phase 1, multicenter, dose escalation study of CBT-501 in subjects in select advanced or relapsed/recurrent solid tumors. The primary study objective is to identify the overall safety and tolerability, including any dose limiting toxicities (DLT), and determine the recommended Phase 2 dose (RP2D) in subjects with advanced solid tumors. Secondary objectives include assessing efficacy by overall response rate (ORR), best overall response rate (BOR) per RECIST v1.1 and irRECIST, time to response, duration of response (DOR), disease control rate (DCR) by RECIST v1.1 and irRECIST, progression free survival (PFS), and determining the pharmacokinetic (PK) parameters. Exploratory objectives involve the assessment of PD-1 and PD-L1 expression, receptor occupancy and the host immune response (immune modulation) in blood peripheral-blood mononuclear cells (PBMCs) or formalin-fixed paraffin-embedded (FFPE) samples. This is a 2-part study with a dose-escalation segment and dose and disease expansion cohorts of CBT-501. In Part 1, dose escalation (3+3 design) will occur among 3 cohorts to determine the RP2D. The tumor type(s) with the most robust clinical signal relative to response rate and safety/tolerability will be selected for further evaluation in the expansion cohort (Part 2). Approximately 32 subjects will be enrolled in the dose and disease expansion and treated at the RP2D, as determined in Part 1.
Clinical Trial Registry Number: NCT03053466.
P280 Combination lymphoma immunotherapy using intratumoral virus-like particles containing CpG TLR9 agonist combined with checkpoint blockade
P307 Expression and function of PD-1 and TIM-3 in non-small cell lung cancer (NSCLC)
Jonathan Travers, Krtisten McEachern, Srimoyee Ghosh, Sridhar Ramaswamy, David Jenkins
1TESARO Inc., Waltham, MA, USA
Correspondence: David Jenkins ([email protected])
The use of anti-programmed cell death protein 1 (PD-1) and PD-Ligand 1 agents in the treatment of non-small cell lung cancer (NSCLC) has been well established but many patients are either intrinsically resistant or become refractory during therapy. One potential resistance mechanism is the upregulated expression of additional checkpoint receptors such as T cell immunoglobulin and mucin domain 3 (TIM-3), a transmembrane receptor that binds multiple putative ligands, and that has been shown to negatively regulate the function of T cells that co-express PD-1 .
We showed that primary NSCLC samples display heterogeneity in both their baseline immune infiltrate and also PD-1 and TIM-3 checkpoint receptor expression. We examined mRNA expression of multiple immune genes on sorted PD-1+ and TIM-3+ CD8+ T cells, and found that PD-1/TIM-3 double positive cells express reduced interleukin-2 (IL-2) and tumor necrosis factor alpha (TNFα), but similar mRNA levels of interferon gamma (IFNγ) when compared to double negative cells. This phenotype is recapitulated in CD8+ T cells derived from patient samples stimulated with PMA and ionomycin, where we found PD-1 and TIM-3 double positive cells to be significantly deficient in IL-2, but not IFNγ production. Importantly, in addition to their expression being associated with T-cell dysfunction, we also found that blockade of PD-1 and TIM-3 was associated with increased T cell activation and anti-tumor activity in ex vivo and in vivo models, suggesting a potential functional role for the inhibition of TIM-3, in addition to PD-1, in the enhancement of anti-tumor immunity.
Taken together, these data provide further evidence that TIM-3 may play a role in intrinsic resistance to single agent anti-PD1 therapy in NSCLC and support evaluating the combination of anti-PD-1 and anti-TIM-3 agents in the clinic.
1. Koyama, et al. Adaptive resistance to therapeutic PD-1 blockade is associated with upregulation of alternative immune checkpoints. Nat Commun. 2016;7:10501.
P313 In vivo effect of albumin binding domains attached to immune modulators
Haomin Huang, Keneshia Haenssen, Anil Bhate, Supriya Sanglikar, John Baradei, Shan Liu, Senthil Kumar, Zihao Cui, Richard Hampton, Robert Kramer, John Cini
Sonnet BioTherapeutics, Cranbury, NJ, USA
Correspondence: Haomin Huang ([email protected]); Keneshia Haenssen; Anil Bhate; Supriya Sanglikar; John Baradei; Shan Liu; Senthil Kumar; Zihao Cui; Richard Hampton
Recombinant therapeutic proteins < 50Kd (eg., receptor ligands, cytokines) exhibit short circulation half-lives (mins/hour vs. days for IgGs) which limit their therapeutic utility. A specific way to increase the pharmacokinetic half-life of these agents is via conjugation to circulating albumin. Here we describe the creation of an albumin binding single chain fragment antibody (ScFv-ABD) that binds albumin in circulation, is recycled by binding to the FcRn (similar to IgG’s) and then recycled after cellular uptake resulting in increased half-life of the appended therapeutic protein. A second advantage to linking a therapeutic protein to an ScFv-ABD is improved tumor target delivery as numerous studies have shown that albumin accumulates in tumors and inflamed tissues.
Sonnet BioTherapeutics, using a XOMA phage library, has developed scFv ABD fusion constructs with several different small therapeutic proteins (recombinant interleukin proteins and scFvs targeting relevant immune-oncology receptors). These various ABD constructs have high binding affinity to mouse, human & cyno circulating serum albumin thereby preventing renal clearance and retaining benefits of FcRn mediated recycling of albumin for extended PK. Early studies to investigate improved tumor accumulation translates into anti-tumor efficacy in vivo and have shown that ScFv-ABD enhances tumor targeting.
Our characterized scFV-ABD constructs have demonstrated that;
biologic activity is retained when the therapeutic protein is attached via the N- or C-terminus suggesting utility for delivering more than one therapeutic protein/scFv;
half-life in mouse serum in vivo was extended from minutes to hours/days for three different recombinant proteins and scFv with MWs of 10-80Kd;
in an established B6F10 melanoma model these ABD constructs have demonstrated markedly superior reductions in tumor growth and improved overall survival compared to the same constructs without the ABD. Superior efficacy was observed with lower doses and with a single dose of the ScFv-ABD constructs vs free recombinant protein
We will describe several examples of improved half-life, tumor accumulation and efficacy using our albumin linkage approach that is leading to the selection of drug candidates for clinical development.
P321 Ibrutinib in combination with agonist αOX40 mAb and CTLA-4 blockade induces Eomeshi CD8 T cells and promotes tumor regression
1Oregon Health & Science University, Portland, OR, USA; 2Earle A. Chiles Research Institute, Portland, OR, USA
Correspondence: William Redmond ([email protected])
Antagonist monoclonal antibodies (mAb) targeting T cell checkpoints such as CTLA-4 or PD-1 have shown efficacy in treating a subset of patients with metastatic disease. In preclinical models, CTLA-4 blockade synergized with an agonist anti-OX40 mAb to enhance the expansion and effector function of tumor-specific T cells. Previous studies demonstrated that combined aOX40/aCTLA-4 therapy also induced the generation of CD8 T cells expressing high levels of Eomesodermin (Eomes), a transcription factor known to regulate CD8 T cell differentiation and memory. Eomes expression is negatively regulated in T cells by the T cell signaling kinase ITK (interleukin-2 inducible T cell kinase). Importantly, the FDA-approved Bruton’s tyrosine kinase inhibitor ibrutinib also blocks ITK, thus providing a potential means of modulating Eomes expression. We sought to characterize these Eomes hi CD8 T cells and investigate the mechanisms regulating the generation of this novel subset.
Wild-type C57BL/6 mice were challenged by 1×10 6 TRAMP-C1 tumor cells in the right flank. Wild-type BALB/C mice were challenged by 5×10 4 4T1 tumor cells orthotopically in the mammary fat pad. Mice were treated starting day 7 with 200ug aCTLA-4 (clone 9D9), 200ug aOX40 (Clone OX86), or 150ug Ibrutinib. All treatments were injected i.p. Tumor growth (area) was assessed with microcallipers every 2 to 3 days. Mice were killed when tumors exceeded 175mm 2 for experiments tracking tumor growth and survival. Lymph nodes and tumors were harvested on day 14 to assess and characterize T cell responses by flow cytometry.
Our data revealed that these Eomes hi CD8 T cells expressed significantly less PD-1 on their surface compared to Eomes lo CD8 T cells (97% vs. 57%, respectively), while maintaining high levels of IFN-g production within the tumor. Additionally, we confirmed that clinical concentrations of ibrutinib do not inhibit T cell receptor signaling in CD8 T cells. Next, demonstrated that the combination of ibrutinib/aOX40/aCTLA-4 therapy enhanced the frequency of Eomes hi CD8 T cells in 4T1 tumor-bearing mice, a model of triple negative breast cancer. Additionally, this triple therapy significantly enhanced IFN-g and TNF-a expression by CD4 and CD8 T cells in the tumor and draining lymph nodes, which was associated with tumor regression and enhanced survival in TRAMP-C1 and Myc-CaP models of prostate adenocarcinoma.
Taken together, these data demonstrate that combined ibrutinib/aOX40/aCTLA-4 therapy induced a robust population of Eomes hi CD8 T cells with enhanced effector function capable of mediating tumor regression in multiple pre-clinical tumor models.
P334 Inhibition of IDO activity by epacadostat (INCB024360) activates tumor infiltrating lymphocytes in a patient-derived 3D ex vivo system of lung cancer and alleviates stromal immunosuppression
1Nilogen Oncosystems, Tampa, FL, USA; 2Incyte Corporation, Wilmington, DE, USA
Correspondence: Soner Altiok ([email protected])
Immune evasion is one of the major hallmarks of cancer and identifying mechanisms by which cancer cells evade the immune system have become a major strategy against cancer. IDO (indoleamine 2,3-dioxygenase) is a tryptophan catabolizing enzyme expressed constitutively by tumor cells and different components of immune cells present within the tumor microenvironment. It has been shown that high expression of IDO increases the number of Tregs and blocks the proliferation of effector T cells. Thus, inhibiting the IDO pathway is a promising strategy to restore immune system responses to more easily identify and destroy cancer cells. This study evaluates the immunomodulatory effect of an IDO inhibitor epacadostat (INCB024360) on the immunosuppressive effect of cancer-associated fibroblasts and activation of tumor infiltrating lymphocytes in a 3D ex vivo assay utilizing fresh patient tumor samples
3D e x vivo studies were performed with fresh tumor tissue obtained from consented NSCLC patients. Tumor samples were treated with IDO inhibitor at 1μM for 48 hours. HPLC analysis on kynurenine and tryptophan was performed to verify target inhibition in the ex vivo model. A multiplex human cytokine assay was used to simultaneously analyze the differential release of cytokines in culture media. Additionally, NanoString PanCancer Immune Profiling platform containing probes to quantitate 770 immune function genes was used to determine positive and negative associations between expression of immune function genes and TIL activation by ex vivo treatment. Furthermore, autologous patient-derived cell lines (CAF and TILs) were utilized in an in vitro assay to determine the role of IDO inhibition on CAF-mediated immunosuppression.
3D ex vivo studies showed a significant decrease in kynurenine demonstrating that epacadostat effectively inhibited the enzymatic activity of IDO in the tumor microenvironment accompanied by increased release of pro-inflammatory cytokines such as IFNγ. Treatment with epacadostat demonstrated decreased expression of genes involved in tumor growth (CCL25) and increased expression of antitumor immune response genes (CXCL14, CCL19 and CCL21). These studies showed epacadostat at an effective concentration of 1μM induced specific changes in the microenvironment and increased immune response. Furthermore, the autologous patient derived cell line in vitro assay determined that epacadostat overcame CAF induced inhibition of TIL activity.
This patient-derived 3D ex vivo approach demonstrated the immunomodulatory activity of epacadostat in NSCLC and indicates that inhibition of IDO activity may overcome stroma-induced immunosuppression in lung cancer. Studies on the effects of epacadostat in combination with anti-PD1 in the same culture systems are currently ongoing.