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Thrombin generation is pivotal to both physiological blood clot formation and pathological development of disseminated intravascular coagulation (DIC). In critical illness, extensive cell damage can release histones into the circulation, which can increase thrombin generation and cause DIC, but the molecular mechanism is not clear. Typically, thrombin is generated by the prothrombinase complex, comprising activated factor X (FXa), activated cofactor V (FVa), and phospholipids to cleave prothrombin in the presence of calcium. In this study, we found that in the presence of extracellular histones, an alternative prothrombinase could form without FVa and phospholipids. Histones directly bind to prothrombin fragment 1 (F1) and fragment 2 (F2) specifically to facilitate FXa cleavage of prothrombin to release active thrombin, unlike FVa, which requires phospholipid surfaces to anchor the classical prothrombinase complex. In vivo, histone infusion into mice induced DIC, which was significantly abrogated when prothrombin F1 + F2 were infused prior to histones, to act as decoy. In a cohort of intensive care unit patients with sepsis (n = 144), circulating histone levels were significantly elevated in patients with DIC. These data suggest that histone-induced alternative prothrombinase without phospholipid anchorage may disseminate intravascular coagulation and reveal a new molecular mechanism of thrombin generation and DIC development. In addition, histones significantly reduced the requirement for FXa in the coagulation cascade to enable clot formation in factor VIII (FVIII)– and FIX-deficient plasma, as well as in FVIII-deficient mice. In summary, this study highlights a novel mechanism in coagulation with therapeutic potential in both targeting systemic coagulation activation and correcting coagulation factor deficiency.

Thrombin generation is pivotal to both physiological blood clot formation and pathological development of disseminated intravascular coagulation (DIC). In critical illness, extensive cell damage can release histones into the circulation, which can increase thrombin generation and cause DIC, but the molecular mechanism is not clear. Typically, thrombin is generated by the prothrombinase complex, comprising activated factor X (FXa), activated cofactor V (FVa), and phospholipids to cleave prothrombin in the presence of calcium. In this study, we found that in the presence of extracellular histones, an alternative prothrombinase could form without FVa and phospholipids. Histones directly bind to prothrombin fragment 1 (F1) and fragment 2 (F2) specifically to facilitate FXa cleavage of prothrombin to release active thrombin, unlike FVa, which requires phospholipid surfaces to anchor the classical prothrombinase complex. In vivo, histone infusion into mice induced DIC, which was significantly abrogated when prothrombin F1 + F2 were infused prior to histones, to act as decoy. In a cohort of intensive care unit patients with sepsis (n = 144), circulating histone levels were significantly elevated in patients with DIC. These data suggest that histone-induced alternative prothrombinase without phospholipid anchorage may disseminate intravascular coagulation and reveal a new molecular mechanism of thrombin generation and DIC development. In addition, histones significantly reduced the requirement for FXa in the coagulation cascade to enable clot formation in factor VIII (FVIII)– and FIX-deficient plasma, as well as in FVIII-deficient mice. In summary, this study highlights a novel mechanism in coagulation with therapeutic potential in both targeting systemic coagulation activation and correcting coagulation factor deficiency.

ABSTRACTThe analysis of peripheral blood mononuclear cells (PBMCs) by flow cytometry holds promise as a platform for immune checkpoint inhibition (ICI) biomarker identification. Our aim was to characterize the systemic immune compartment in resectable esophageal adenocarcinoma patients treated with neoadjuvant ICI therapy. In total, 24 patients treated with neoadjuvant chemoradiotherapy (nCRT) and anti-PD-L1 (atezolizumab) from the PERFECT study (NCT03087864) were included and 26 patients from a previously published nCRT cohort. Blood samples were collected at baseline, on-treatment, before and after surgery. Response groups for comparison were defined as pathological complete responders (pCR) or patients with pathological residual disease (non-pCR). Based on multicolor flow cytometry of PBMCs, an immunosuppressive phenotype was observed in the non-pCR group of the PERFECT cohort, characterized by a higher percentage of regulatory T cells (Tregs), intermediate monocytes, and a lower percentage of type-2 conventional dendritic cells. A further increase in activated Tregs was observed in non-pCR patients on-treatment. These findings were not associated with a poor response in the nCRT cohort. At baseline, immunosuppressive cytokines were elevated in the non-pCR group of the PERFECT study. The suppressive subsets correlated at baseline with a Wnt/β-Catenin gene expression signature and on-treatment with epithelial–mesenchymal transition and angiogenesis signatures from tumor biopsies. After surgery monocyte activation (CD40), low CD8+Ki67+ T cell rates, and the enrichment of CD206+ monocytes were related to early recurrence. These findings highlight systemic barriers to effective ICI and the need for optimized treatment regimens.

ROR1 is expressed on a range of solid and haematological malignancies, including chronic lymphocytic leukaemia, mantle cell lymphoma and a subset of acute lymphoblastic lymphoma, making it an attractive therapeutic target. In keeping with this, ROR1 CAR T cells and a ROR1 antibody, are being investigated as novel treatments [NCT02222688, NCT02776917 & NCT02706392]. BiTEs are small, 55kDa antibody based therapeutics composed of two single chain variable fragments (scFv) linked in tandem by a flexible linker. One scFv binds to tumour antigens and the other to the CD3 complex, bringing target cells and T cells in close proximity, facilitating formation of cytotoxic synapses and resulting in target cell death. We have generated a fully humanised ROR1 BiTE which unlike conventional antibodies recruits and utilises the inherent cytotoxic potential of polyclonal resident T cells and does not require ex vivocell manipulation. We therefore investigated the potential of a ROR1 BiTE for the treatment of CLL.

ABSTRACTWe have developed a humanized bi-specific T-cell engager (BiTE) targeting receptor tyrosine kinase-like orphan receptor 1 (ROR1), a cell surface antigen present on a range of malignancies and cancer-initiating cells. Focusing initially on pancreatic cancer, we demonstrated that our ROR1 BiTE results in T cell mediated and antigen-specific cytotoxicity against ROR1-expressing pancreatic cancer cell lines in vitroat exceedingly low concentrations (0.1 ng/mL) and low effector to target ratios. Our BiTE prevented engraftment of pancreatic tumor xenografts in murine models and reduced the size of established subcutaneous tumors by at least 3-fold. To validate its wider therapeutic potential, we next demonstrated significant cytotoxicity against ovarian cancer in an in vitroand in vivosetting and T-cell-mediated killing of a range of histologically distinct solid tumor cell lines. Overall, our ROR1 BiTE represents a promising immunotherapy approach, because of its ability to target a broad range of malignancies, many with significant unmet therapeutic needs.

Immunotherapy with chimeric antigen receptor (CAR) T cells and bispecific T-cell engagers (BiTEs) has shown impressive efficacy against CD19+ malignancies, but translation to other tumour targets is not possible. In this regard, receptor tyrosine kinase like orphan receptor 1 (ROR1) is an attractive therapeutic target that is present on a range of haematological and solid malignancies, as well as cancer stem cells, but importantly with limited expression on normal adult tissues. Our aim, through iterative optimisation, was to generate novel humanised ROR1 single chain variable fragments (scFv) that enable efficient targeting of ROR1 on tumour cells without toxicity.

Paredes-Moscosso: UCL Business: Patents & Royalties: ROR1 based immunotherapies. Della Peruta:UCL Business: Patents & Royalties: ROR1 based immunotherapies. Gohil:UCL Business: Patents & Royalties: ROR1 based immunotherapies. Nathwani:UCL Business: Patents & Royalties: ROR1 based Immunotherapies.

Introduction:

Chronic Lymphocytic Leukaemia (CLL), the most common leukaemia of the elderly, remains largely incurable despite chemotherapy and small molecule inhibitors. Treatment targeting CD19 and CD20 has achieved important clinical benefits; however, these antigens are also present on normal B-cells rendering the patients immunodeficient and at a higher risk of infections. In view of this, our immunotherapy strategy is to produce therapeutic antibodies targeting the receptor-tyrosine-kinase-like orphan receptor 1 (ROR1), a protein present on the surface of malignant B-cells and cancer stem cell-like cells (CSC), but absent on most normal tissue.

Gohil: UCL Business: Patents & Royalties: ROR1 based immunotherapies. Paredes-Moscosso:UCL Business: Patents & Royalties: ROR1 based immunotherapies. Nathwani:UCL Business: Patents & Royalties: ROR1 based Immunotherapies. Della Peruta:UCL Business: Patents & Royalties: ROR1 based immunotherapies.

Gohil: UCL Business: Patents & Royalties: ROR1 based immunotherapies. Della Peruta:UCL Business: Patents & Royalties: ROR1 based immunotherapies. Paredes-Moscosso:UCL Business: Patents & Royalties: ROR1 based immunotherapies. Pule:Roche: Honoraria; UCL Business: Patents & Royalties; Autolus Ltd: Employment, Equity Ownership, Research Funding; Amgen: Honoraria. Nathwani:UCL Business: Patents & Royalties: ROR1 based Immunotherapies.

Bispecific T-cell Engagers (BiTEs) are a promising immunotherapeutic approach, usually consisting of two single chain variable fragments (scFv) linked in tandem. One arm binds to tumour-associated antigens, whilst the other binds CD3 on T-cells, facilitating the formation of cytotoxic synapses leading to killing of tumour targets in a MHC and co-stimulatory molecule independent manner. Blinatumomab, the most advanced BiTE in clinic targets CD19 and has shown impressive results in patients with relapsed/refractory B cell acute lymphoid leukaemia but results in elimination of normal and malignant B lymphocytes.