EBV+ CNS LYMPHOMAS HAVE A DISTINCTIVE TUMOR MICROENVIRONMENT AND GENETIC PROFILE, WHICH IS AMENABLE TO COMBINATION 3RD PARTY EBV-SPECIFIC CTL AND IBRUTINIB THERAPY

Introduction: Primary CNS Lymphomas (PCNSL) with DLBCL histology in the immunosuppressed, e.g. after HIV (HIV+ PCNSL) or organ transplant (EBV+ PCNSL‐PTLD: where anti‐PD‐1 is contraindicated), are characterized by dismal outcome and almost universal EBV positivity. However, incidence is low, biopsy material limited and immunogenetic characterization minimal. We provide detailed data (308 patients) comparing the genetic landscape and tumor microenvironment (TME) of EBV+ PCNSL‐PTLD (22); HIV+ PCNSL (24); EBV‐ PCNSL (41); EBV‐ systemic (sy) DLBCL (199) and EBV+ syPTLD (22), which led to implementation of a rationally designed combination therapy.Methods: Targeted sequencing, CNV analysis, nanoString (for immune checkpoints and effectors, and macrophage gene expression) and in vitro assays were used. Based on the findings, a novel regimen was administered to patients’ refractory to or unsuitable for frontline therapy. Sequential imaging, pharmacokinetic (PK) and T cell assays were performed.Results: Mutational burden was much lower in EBV+ lymphomas than EBV‐ lymphomas (p<0.0001). Notably, genetic aberrations in BCR‐NFB were rarely observed in EBV+ PCNSL‐PTLD and HIV+ PCNSL, and (unlike EBV‐ PCNSL) in these patients, HLAI/II copy number loss was largely absent. Mutations in CARD11 (which confers ibrutinib resistance) were also rare in EBV+ PCNSL‐PTLD and HIV+ PCNSL. By nanoString analysis, EBV+ PCNSL‐PTLD expressed higher levels of the immunosuppressive ‘M2’ macrophage marker CD163 and LAG3 and PD‐L1/L2 (p<0.001), and high levels of EBV protein LMP1 (known to upregulate PD‐L1/L2 and NFB). In vitro co‐incubation experiments showed a PCNSL line upregulated CD163+ PD‐L1/L2+ M2 polarized monocyte/macrophages relative to a systemic DLBCL line (≥7‐fold, p<0.001), and EBV infection of a PCNSL line enhanced NFB activity (Fig 1A). Three immunosuppressed patients (2 frontline, 1 refractory, ages 30‐70yrs) with EBV+ lymphoma (2 PCNSL, 1 CNS + systemic) were treated with ibrutinib (starting dose 560mg) and 3rd party partially HLA matched EBV specific CTL. PK confirmed therapeutic CSF levels, including a patient on haemodialysis. CD8 T cells specific for EBV antigens present in PCNSL were detectable post infusion and had an effector memory phenotype (Fig 1B‐C). Microchimerism post infusion was confirmed by ultra‐sensitive ddPCR. Toxicity was manageable and all 3 are alive (2CR, 1PR).Conclusion: EBV+ CNSL in the immunosuppressed, have a tolerogenic TME with intact antigen presentation and expression of viral antigens, upregulated NFB signalling and absent CARD11 mutations. Results support combination strategies that cross the Blood Brain Barrier, to block NFB driven oncogenesis (ibrutinib), reconstitute EBV specific T cell immunity (3rd Party EBV specific CTL) and expand the TCR repertoire (ibrutinib). Findings led to an ALLG phase 1 clinical trial (ACTRN12618001541291).