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A phase I multicenter study of enadenotucirev in combination with nivolumab in tumors of epithelial origin: an analysis of the metastatic colorectal cancer patients in the dose escalation phase Marwan Fakih 1 , Ding Wang 2 , Wael Harb 3 , Lee Rosen 4 , Daruka Mahadevan 5 , Jordan Berlin 6 , Paul Basciano 7 , Olajumoke Arogundade 8 , Chris Cox 8 , David Krige 8 , Hilary McElwaine-Johnn 8 , Richard Brown 8 . 1 City of Hope Comprehensive Cancer Center, Duarte, California, USA; 2 Henry Ford Hospital, Detroit, USA; 3 Horizon Oncology Research Inc., Lafayette, Indiana, USA; 4 UCLA Medical Center, Los Angeles, California, USA; 5 University of Arizona Cancer Center, Tucson, Arizona, USA; 6 Vanderbilt-Ingram Cancer Center, Nashville, USA; 7 Bristol Myers Squibb, Lawrenceville, New Jersey, USA; 8 PsiOxus Therapeutics Ltd, Abingdon, Oxford, United Kingdom. Copies of this poster obtained through Quick Response Code are for personal use only and may not be reproduced without permission from the author of this poster. Abstract 612P Enadenotucirev (EnAd) is a tumor-selective chimeric Ad11/Ad3 group B oncolytic adenovirus that does not express any transgenes (a so called “unarmed virus”) [Khun et al, 2008]. Following intravenous (IV) dosing of EnAd to patients with primary colon cancer in a phase I study, effective viral delivery has been demonstrated together with intra- tumoral CD8+ T-cell infiltrates [Garcia-Carbonero et al, 2017]. A further phase I clinical study identified a well-tolerated dose and regimen for EnAd monotherapy, including in patients with metastatic colorectal cancer (mCRC) [Machiels et al, 2019]. Immune checkpoint inhibitors (ICIs) have shown impressive clinical activity in several tumor types, including microsatellite instability (MSI) high mCRC [Le et al, 2015]. However, there is still a significant proportion of tumors which appear to have a primary resistance to ICI therapy, including MSI low and microsatellite stable (MSS) mCRC. Combination treatment strategies using ICIs together with immune stimulatory EnAd may help to overcome ICI resistance in MSI low / MSS mCRC and other ICI resistant tumor types. The SPICE study is a phase I study to examine the safety and potential efficacy of the combination of EnAd and nivolumab in a range of epithelially derived solid tumor types previously shown to have primary or to have developed secondary ICI resistance (squamous cell head and neck (SCCHN), non-small cell lung (NSCLC), urothelial carcinoma (UCC) and MSI low / MSS mCRC). The study design is divided into a dose escalation phase and a dose expansion phase. Here we present an analysis of the 34 mCRC patients dosed to date with EnAd and ICI therapy in the escalation phase of the SPICE study. 1. Background EnAd was escalated in combination with ICI therapy in patients with metastatic epithelial tumors in a 3 +3 design. Subjects received increasing dose levels and/or cycles of EnAd followed by up to 8 cycles of ICI as shown in Figure 1. In the first cohort the ICI used was pembrolizumab, but from cohort 2 onwards this was switched to nivolumab. Cohort 7 is designed to examine an initial low dose of EnAd followed by higher doses. It is hypothesized that the initial low priming dose in this low:high:high (L:H:H) regimen may desensitize for subsequent doses and thus reduce post-infusional cytokine release and the associated adverse events. Key Inclusion Criteria include: • Patients 18 years or older • Diagnosis of metastatic or advanced CRC, UCC, SCCHN or NSCLC • Not responding to standard therapy or no standard treatment exists • Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1 • No proteinuria and adequate renal, hepatic, bone marrow and coagulation tests (each as defined per protocol) Key Exclusion Criteria include: • Prior treatment with PD-1 and/or PD-L1 inhibitors • Investigational drug administration in the prior 28 days • Symptomatic brain metastases The primary objective of the dose escalation phase was to evaluate safety of the combination and to identify a recommended dose and regimen for expansion. Secondary endpoints included overall response rate (ORR), median progression free survival (mPFS) and median overall survival (mOS). Pharmacodynamic (PD) biomarkers included the longitudinal measurement of systemic cytokines and anti-viral antibodies in all patients. Wherever possible pre- and post-treatment tumor biopsies were collected and analyzed for signs of enadenotucirev infection and changes in inflammatory biomarkers. The tumor biomarker analytical methodologies included immunohistochemistry (IHC), automated image analysis and mRNA analysis by Nanostring®. 2. Methods Of the 40 patients enrolled in the study, 34 patients had a diagnosis of mCRC with the characteristics as summarized in Table 1. The EnAd dose ranged between 1x10 12 and 3x10 12 virus particles infused IV for one or two cycles, followed by 360mg of nivolumab every 3 weeks, as shown in Figure 2. 3. Patient characteristics and disposition Figure 1: Study design The SPICE study is conducted at 6 clinical sites in the United States of America. The dose escalation phase of the study uses a 3+3 design to escalate the dose and regimen of enadenotucirev in combination with nivolumab. The progression through the 7 cohorts investigated to date are shown below: Treatment in each cohort consists of up to 8 x 21-day cycles. Enadenotucriev is administered on • Days 1, 3 & 5 of cycle 1 (cohorts 2, 3 & 7), or • Days 1 ,3 & 5 of cycle 1 & 2 (in cohorts 1, 4, & 5) • Days 1, 3, 5, 8, 10 & 12 of cycle 1 (cohort 6) Nivolumab is administered on • Day 8 of each cycle (cohorts 4 & 5), or • Day 15 of each cycle (all other cohorts) Table 1: Patient characteristics A summary of the key characteristics of the 34 mCRC patients recruited to date in the dose escalation phase of the SPICE study is summarized in the table below. Figure 2: Patient disposition and follow-up The disposition and follow-up of the 34 mCRC patients across the 7 dose escalation cohorts are shown in the swim lane plot below. The cut-off date for this data is 6th September 2019 and follow-up is ongoing. RECIST v1.1 assessments shown are from the central reader where available. Table 2: Adverse event summary The common treatment-emergent adverse event incidence for all 40 SPICE patients dosed to date (including the 34 mCRC patients) is summarized in the table below: Note: The prolonged aPTT is believed to be due to Lupus Anticoagulant. Five patients with prolonged aPTT experienced a total of 4 bleeding events (one post study due to progressive appendix cancer) and 1 clotting event (pulmonary embolism during study). Two patients with normal or near-normal aPTT experienced 2 bleeding events and 1 clotting event (1 DVT post study). The incidence is not considered to be excessive considering the population treated, but patients will continue to be monitored. * * Occurring in ≥20% patients overall Table 3: Serious Adverse Event summary The serious adverse event incidence for all 40 SPICE patients dosed to date (including the 34 mCRC patients) is summarized in the table below Figure 3: Patient case study The patient with a confirmed PR shown in Figure 2, is a 46yo female with stage IVb, MSI-Low mCRC (MSI status confirmed by both sequencing and immunohistochemistry) with a BRAF V600E mutation, KRAS wild type and low mutational burden (5 mutations per megabase) phenotype. This patient had received three prior lines of treatment: (1) FOLFOX (Best response: stable disease); (2) FOLFIRI + bevacizumab (Best response: unknown); (3) Cetuximab + encorafenib + binimetinib (Best response: unknown). The start of nivolumab treatment was delayed in this patient compared to the rest of the mCRC patients. Panel 3a Revised nivolumab dosing schedule for this patient Panel 3b Investigator assessment of tumor response by RECIST v1.1 Panel 3c Example target lesion at screening Panel 3d Example target lesion at week 18 3a 3b 3c 3d The adverse event profile is summarized in Tables 2 and 3. Flu-like symptoms were reported in the majority of patients following EnAd administration. Adverse events of infusion reaction and hypoxia meeting DLT criteria were reported on C2D1 administration of EnAd requiring increased prophylaxis. Cases of severe acute renal injury (including membrano-glomerulonephritis indicative of immune complex deposition) and severe acute lung injury have been reported. Measures to prevent and mitigate against these adverse events have been added to the ongoing protocols. Additional urinalysis monitoring revealed changes suggestive of post-infectious GN in ~25% of patients after 3-4 weeks of EnAd dosing. These were largely asymptomatic and resolved without treatment. Prolonged aPTT has been observed in 6 patients but the laboratory evidence and incidence of thrombotic and hemorrhagic events suggest that this is an in vitro artefact associated with Lupus Anticoagulant, as previously described with other adenoviral vectors [Malaeb 2005]. 4. Safety Figure 4: Overall survival Figure 5: Progression free survival Figure 6: Immune cell infiltrates 8 patients with a diagnosis of mCRC had matching pre- and post-treatment tumor biopsy samples with sufficient tumor and stromal tissue for IHC staining and automated image analysis. Cell counting by automated image analysis demonstrates evidence of increased inflammation in 6 out of 8 of these patients. Post- treatment biopsies were taken ~5 weeks after first viral dosing. Panel 6a IHC staining for intratumoral CD8+ cells: example pre- versus post treatment Panel 6b IHC staining for PD-L1 + immune cells: example pre- versus post treatment Panel 6c Intratumoral CD8+ cell infiltrates: Median 4.7 fold increase from baseline (mean 34 fold increase) Panel 6d Stromal CD8+ cell infiltrates. Median 2 fold increase from baseline (mean 1.3 fold increase) Panel 6e Percentage infiltrating PD-L1+ immune cells. Median 2 fold increase from baseline (mean 2.2 fold increase) 6c 6d 6e 6a 6b Pre-treatment Post-treatment Pre-treatment Post-treatment There was one confirmed partial response (ORR = 2.9%) and stable disease of 4 or more months was seen in 7/34 (21%) patients. The patient with a confirmed PR shown in Figure 3, is a 46yo female with stage IVb, MSI-Low mCRC (MSI status confirmed by both sequencing and immunohistochemistry) with a BRAF V600 mutant, KRAS wild type and low mutational burden (5 mutations per megabase) phenotype. As of 6th September 2019, with a median follow-up of 11 months, mOS is 14.0 months (95% CI = 11.0m, 16.5m) and mPFS is 1.6 months (95% CI = 1.5m, 2.8m). The Kaplan Meier estimates are shown in Figures 4 and 5 respectively. For the subset of 26 patients with confirmed MSS/MSI low status, the mOS was 15.4 months (95% CI 11.8m, 16.5m). 5. Efficacy PD biomarkers show evidence of inflammation in 6 out of the 8 patients with matched pre- and post-treatment tumor biopsy samples [Figure 6]. Intratumoral CD8+ T cell infiltration showed a median 4.7 fold increase from pre-treatment levels whilst the stromal levels increased by a median of 2 fold. There was also evidence in some patients of increases in CD8+ T cell proliferation (Ki67) and cytolytic activity (Granzyme B) as well as increases in the number of PD-L1+ immune cells. Kinetics, cytokines and anti-drug antibody responses were consistent with known profiles for both agents. Initial data from cohort 7 suggests that a L:H:H dosing regimen may reduce the levels of acute cytokines released following administration and may be associated with an improved tolerability profile. 6. Biomarkers The combination of enadenotucirev and nivolumab in patients with heavily pre-treated MSI low or MSS mCRC has a manageable tolerability profile and is associated with preliminary but encouraging signals of efficacy, including a median overall survival estimate of 14 months. These data support further investigation of this combination in epithelial tumors with primary or secondary resistance to checkpoint inhibitors. These data with the genetically unmodified oncolytic enadenotucirev virus are also supportive of a range of follow-on genetically modified or “armed” viruses using enadenotucirev as a cancer gene therapy vector. These gene therapy products are expected to have the oncolytic and pro-inflammatory activity of enadenotucirev but with the enhancement of the added co-delivery of therapeutic transgenes. Several such Tumor Specific Immuno-gene Therapy (T-SIGn) products are currently in phase I clinical trials. 7. Discussion Khun I et al, 2008: Directed Evolution Generates a Novel Oncolytic Virus for the Treatment of Colon Cancer. PLoS ONE 3(6): e2409. Garcia-Carbonero R et al, 2017: Phase 1 study of intravenous administration of the chimeric adenovirus enadenotucirev in patients undergoing primary tumor resection. Journal for Immuno Therapy of Cancer Vol 5, Article 71 Machiels JP et al, 2019: A phase 1 dose escalation study of the oncolytic adenovirus enadenotucirev, administered intravenously to patients with epithelial solid tumors (EVOLVE). Journal for Immuno Therapy of Cancer Vol 7, Article 20 Le DT et al, 2015. PD-1 Blockade in Tumors with Mismatch-Repair Deficiency. N Engl J Med. 372(26):2509-20 Malaeb BS et al. 2005: Elevated activated partial thromboplastin time during administration of first-generation adenoviral vectors for gene therapy for prostate cancer: identification of lupus anticoagulants. Urology. 66(4):830-4 References Clinical trial information: EUDRACT Number 2017-001231-39
