Citations

TPS7586 Background: EO2463 is a therapeutic vaccine designed to activate existing commensal bacteria-specific memory T cells that cross-react with B cell markers in order to drive anti-tumor immune activity against B-cell malignancies. The four microbial-derived, synthetically produced peptides contained in EO2463 (OMP72, OMP64, OMP65, and OMP66), correspond to cytotoxic CD8 T cell HLA-A2 restricted epitopes, and exhibit molecular mimicry with the B cell markers CD20, CD22, CD37, and CD268 (BAFF-receptor), respectively. In pre-clinical models, these peptides can generate strong immune responses and specifically stimulate cross-reactive cytotoxic CD8 T cells to recognize the chosen B cell targets. EO2463 also contains a CD4 helper peptide referred to as universal cancer peptide 2, derived from the human telomerase reverse transcriptase catalytic subunit. The present study is a first-in-human clinical trial of this microbiome-derived peptide therapeutic cancer vaccine approach in patients with follicular lymphoma (FL) and marginal zone lymphoma (MZL). Methods: This four-cohort phase 1/2 trial will investigate EO2463 monotherapy, and combinations of EO2463/lenalidomide (EL), EO2463/rituximab (ER), and EO2463/lenalidomide/rituximab (ER2), for treatment of patients with FL and MZL. Cohort 1 is a safety lead-in dose-finding in patients with relapsed/refractory (RR) disease, with a 3-by-3 design to establish the recommended phase 2 dose (RP2D) for EO2463 monotherapy and to confirm the safety of the RP2D for combination schedules of EL, and ER2. After the recommended EO2463 monotherapy dose is established, cohorts 2, 3, and 4 will open to accrual. Cohort 2 will investigate EO2463 monotherapy in patients with newly diagnosed FL/MZL who are not in need of treatment; cohort 3 will investigate EO2463 monotherapy, followed by ER in patients with limited tumor burden who need treatment, and cohort 4 will further investigate EL, followed by ER2 in the RR setting. EO2463 will be administered SC 4 times at 2-week intervals, followed by continued booster administrations every 4 weeks for 9 (Cohorts 2 and 3) or 12 (Cohorts 1 and 4) months. Inclusion/exclusion criteria, and the design and schedule of the intense immune and safety monitoring will be presented. The safety lead-in dose-finding is currently ongoing, and no safety concerns have been observed thus far. Clinical trial information: NCT04669171.

Abstract BACKGROUND. The detection of minimal residual disease (MRD) at the level of 0.01%/10-4 or above is a strong independent predictor of reduced progression-free (PFS) and overall survival (OS) in patients with CLL treated with chemoimmunotherapy. Although newer agents such as B-cell receptor pathway inhibitors can result in prolonged survival without achieving complete response, there remains a important role for MRD analysis in assessing therapeutic strategies aimed at disease eradication and cure. This is particularly important in front-line trials for fit patients which now require at least five years of follow-up if PFS is used as an endpoint. The feasibility of using MRD as a surrogate or intermediate endpoint for accelerated approval of new treatments is under review by regulatory agencies but further prospective validation is required. At the same time technology is rapidly evolving and high-throughput sequencing (HTS) technologies now detect MRD at the 0.0001%/10-6 level. It is therefore important to determine the most effective approaches for quantifying MRD that are compatible with previous studies but sufficiently sensitive for current treatments. AIMS. This collaborative project had two objectives. First, to identify the simplest and most flexible flow cytometry panel capable of detecting MRD at the 0.01%/10-4 or lower, that is compatible with published data and independent of instrument/reagent manufacturer. Second, to compare the flow cytometry approach with HTS analysis using the ClonoSEQ assay (Adaptive Biotechnologies, Seattle, WA). METHODS AND RESULTS. A core panel of antibodies for MRD detection was identified by testing an 8-marker combination in 52 samples (27 post-treatment and 25 dilution study) and re-analysing data with serial exclusion of single markers to determine redundancy. A 1-tube core panel of CD19, CD20, CD5, CD43, CD79b, and CD81 was identified and validated against the previously published 2-tube 6-marker and 4-tube 4-marker ERIC panels in 76 samples (19 post-treatment and 57 dilution study). The results showed good concordance (for log-transformed data above the LoQ, linearity=0.977, Pearson correlation co-efficient=0.983, average difference=0.026 log, 95% limit of agreement 0.20log) and a limit of detection of 0.001%/10-5 for the 1-tube core panel. Inter-operator variation was similar to CML MRD monitoring with both experienced operators, or inexperienced cytometrists after ~1 hour of specific education, achieving a 95% limit of agreement less than 0.3log in samples with MRD levels ranging from 0.0001 – 100%. The flow cytometry approach was compared with the ClonoSEQ HTS assay in 109 samples (21 dilution study and 88 post-treatment samples, complete data currently available on 13/88). The assay was applicable to the vast majority CLL patients, often with two clonal markers. There was 94% concordance at the 0.01% (10-4) threshold (15 samples with ≥0.01% CLL by both methods, 14 samples with <0.01% by both methods, 1 sample with 0.03% CLL by HTS and <0.003% CLL by flow cytometry, and 1 sample with 0.005% CLL by HTS and 0.012% by flow cytometry. HTS detected CLL IGH sequences in 22% (7/31) samples with no detectable CLL cells by flow cytometry (i.e. CLL level 0.0001-0.001%, 3/13 patient samples and 4/18 dilution samples). HTS demonstrated a relatively high variability in quantification, as seen in previous studies, but with a clear superiority in the limit of detection and good linearity (linearity=0.905, Pearson correlation co-efficient=0.870, average difference=0.078 log, 95% limit of agreement 1.5 log). CONCLUSIONS. The 1-tube 6-marker flow cytometry core panel is compatible with published studies, manufacturer-independent and flexible, providing directly quantitative results to 0.001%/10-5 without requiring a pre-treatment sample. HTS requires further work to standardise the quantitative analysis and prospective validation but the ClonoSEQ assay is applicable to >95% of CLL patients, does not require viable cells and is extremely sensitive, detecting residual disease in a significant proportion of cases with <0.01% CLL. The results indicate that flow cytometry and HTS are complementary technologies with a combined approach offering the most reliable way of quantifying CLL at the 0.01%/10-4 threshold while allowing higher sensitivity in clinical trials aimed at disease eradication. Disclosures Rawstron: Roche: Honoraria; Biogen Idec: Consultancy; Gilead: Consultancy, Honoraria; Abbvie: Honoraria; BD Biosciences: Intrasure reagent Patents & Royalties; Celgene: Honoraria; GSK: Honoraria. Williamson:Adaptive Biotechnologies: Employment, Equity Ownership. Sanders:Adaptive Biotechnologies: Employment, Equity Ownership. Robins:Adaptive Biotechnologies: Consultancy, Equity Ownership, Patents & Royalties. Hallek:Celgene: Honoraria, Research Funding; Mundipharma: Honoraria, Research Funding; Roche: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; GSK: Honoraria; Gilead: Honoraria. Hillmen:Roche: Honoraria, Research Funding; GSK: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Pharmacyclics: Honoraria, Research Funding; Gilead: Honoraria, Research Funding.