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B-cell maturation antigen (BCMA) is a promising therapeutic target for multiple myeloma (MM), but expression is variable, and early reports of BCMA targeting chimeric antigen receptors (CARs) suggest antigen downregulation at relapse. Dual-antigen targeting increases targetable tumor antigens and reduces the risk of antigen-negative disease escape. “A proliferation-inducing ligand” (APRIL) is a natural high-affinity ligand for BCMA and transmembrane activator and calcium-modulator and cyclophilin ligand (TACI). We quantified surface tumor expression of BCMA and TACI on primary MM cells (n = 50). All cases tested expressed BCMA, and 39 (78%) of them also expressed TACI. We engineered a third-generation APRIL-based CAR (ACAR), which killed targets expressing either BCMA or TACI (P < .01 and P < .05, respectively, cf. control, effector-to-target [E:T] ratio 16:1). We confirmed cytolysis at antigen levels similar to those on primary MM, at low E:T ratios (56.2% ± 3.9% killing of MM.1s at 48 h, E:T ratio 1:32; P < .01) and of primary MM cells (72.9% ± 12.2% killing at 3 days, E:T ratio 1:1; P < .05, n = 5). Demonstrating tumor control in the absence of BCMA, we maintained cytolysis of primary tumor expressing both BCMA and TACI in the presence of a BCMA-targeting antibody. Furthermore, using an intramedullary myeloma model, ACAR T cells caused regression of an established tumor within 2 days. Finally, in an in vivo model of tumor escape, there was complete ACAR-mediated tumor clearance of BCMA+TACI− and BCMA−TACI+ cells, and a single-chain variable fragment CAR targeting BCMA alone resulted in outgrowth of a BCMA-negative tumor. These results support the clinical potential of this approach.

B-cell maturation antigen (BCMA) is a promising therapeutic target for multiple myeloma (MM), but expression is variable, and early reports of BCMA targeting chimeric antigen receptors (CARs) suggest antigen downregulation at relapse. Dual-antigen targeting increases targetable tumor antigens and reduces the risk of antigen-negative disease escape. “A proliferation-inducing ligand” (APRIL) is a natural high-affinity ligand for BCMA and transmembrane activator and calcium-modulator and cyclophilin ligand (TACI). We quantified surface tumor expression of BCMA and TACI on primary MM cells (n = 50). All cases tested expressed BCMA, and 39 (78%) of them also expressed TACI. We engineered a third-generation APRIL-based CAR (ACAR), which killed targets expressing either BCMA or TACI (P< .01 and P< .05, respectively, cf. control, effector-to-target [E:T] ratio 16:1). We confirmed cytolysis at antigen levels similar to those on primary MM, at low E:T ratios (56.2% ± 3.9% killing of MM.1s at 48 h, E:T ratio 1:32; P< .01) and of primary MM cells (72.9% ± 12.2% killing at 3 days, E:T ratio 1:1; P< .05, n = 5). Demonstrating tumor control in the absence of BCMA, we maintained cytolysis of primary tumor expressing both BCMA and TACI in the presence of a BCMA-targeting antibody. Furthermore, using an intramedullary myeloma model, ACAR T cells caused regression of an established tumor within 2 days. Finally, in an in vivo model of tumor escape, there was complete ACAR-mediated tumor clearance of BCMA+TACI−and BCMA−TACI+cells, and a single-chain variable fragment CAR targeting BCMA alone resulted in outgrowth of a BCMA-negative tumor. These results support the clinical potential of this approach.

AimsMultiple myeloma is a genomically complex haematological malignancy with many genomic alterations recognised as important in diagnosis, prognosis and therapeutic decision making. Here, we provide a summary of genomic findings identified through routine diagnostic next-generation sequencing at our centre.MethodsA cohort of 86 patients with multiple myeloma underwent diagnostic sequencing using a custom hybridisation-based panel targeting 104 genes. Sequence variants, genome-wide copy number changes and structural rearrangements were detected using an inhouse-developed bioinformatics pipeline.ResultsAt least one mutation was found in 69 (80%) patients. Frequently mutated genes included TP53(36%), KRAS(22.1%), NRAS(15.1%), FAM46C/DIS3(8.1%) and TET2/FGFR3(5.8%), including multiple mutations not previously described in myeloma. Importantly we observed TP53mutations in the absence of a 17 p deletion in 8% of the cohort, highlighting the need for sequencing-based assessment in addition to cytogenetics to identify these high-risk patients. Multiple novel copy number changes and immunoglobulin heavy chain translocations are also discussed.ConclusionsOur results demonstrate that many clinically relevant genomic findings remain in multiple myeloma which have not yet been identified through large-scale sequencing efforts, and provide important mechanistic insights into plasma cell pathobiology.

NBEAL2encodes a multidomain scaffolding protein with a putative role in granule ontogeny in human platelets. Mutations in NBEAL2underlie gray platelet syndrome (GPS), a rare inherited bleeding disorder characterized by a lack of α-granules within blood platelets and progressive bone marrow fibrosis. We present here a novel Nbeal2−/−murine model of GPS and demonstrate that the lack of α-granules is due to their loss from platelets/mature megakaryocytes (MKs), and not by initial impaired formation. We show that the lack of Nbeal2 confers a proinflammatory phenotype to the bone marrow MKs, which in combination with the loss of proteins from α-granules drives the development of bone marrow fibrosis. In addition, we demonstrate that α-granule deficiency impairs platelet function beyond their purely hemostatic role and that Nbeal2 deficiency has a protective effect against cancer metastasis.

NBEAL2 encodes a multidomain scaffolding protein with a putative role in granule ontogeny in human platelets. Mutations in NBEAL2 underlie gray platelet syndrome (GPS), a rare inherited bleeding disorder characterized by a lack of α-granules within blood platelets and progressive bone marrow fibrosis. We present here a novel Nbeal2−/− murine model of GPS and demonstrate that the lack of α-granules is due to their loss from platelets/mature megakaryocytes (MKs), and not by initial impaired formation. We show that the lack of Nbeal2 confers a proinflammatory phenotype to the bone marrow MKs, which in combination with the loss of proteins from α-granules drives the development of bone marrow fibrosis. In addition, we demonstrate that α-granule deficiency impairs platelet function beyond their purely hemostatic role and that Nbeal2 deficiency has a protective effect against cancer metastasis.

Lee: Autolus Therapeutics: Equity Ownership, Research Funding. Yong:Takeda: Research Funding, Speakers Bureau; Autolus: Consultancy; Amgen: Research Funding, Speakers Bureau; Janssen: Speakers Bureau; Sanofi: Speakers Bureau.

Introduction: High dose therapy and autologous stem cell transplant (ASCT) remain standard first line therapy for young fit patients with multiple myeloma (MM). Beyond cytoreduction, ASCT may also alter the bone marrow (BM) immune environment to augment anti-tumour immune responses. A more precise understanding of the immune microenvironment post ASCT and its relationship with clinical outcomes may identify biomarkers to refine prognostication and provide opportunity for therapeutic intervention.

Yong: Autolus Ltd: Equity Ownership, Patents & Royalties: APRIL based chimeric antigen receptor; Janssen: Research Funding.

Lee: Bloodwise: Research Funding; Autolus Ltd: Patents & Royalties: APRIL based chimeric antigen receptor. Draper:Autolus Ltd: Equity Ownership, Patents & Royalties: APRIL based CAR. Chaplin:Autolus Ltd: Equity Ownership. Philip:Autolus: Equity Ownership. Thomas:Autolus Ltd: Employment. Kokalaki:Autolus Ltd: Employment. Francis:Autolus Ltd: Employment. Yong:Autolus Ltd: Equity Ownership, Patents & Royalties: APRIL based chimeric antigen receptor; Janssen: Research Funding. Pule:Autolus Ltd: Employment, Equity Ownership, Research Funding; UCL Business: Patents & Royalties; Amgen: Honoraria; Roche: Honoraria.

Background.The overall improvement in treatment outcomes and survival of multiple myeloma (MM) patients has highlighted the persistently poor outlook for patients with del(17p). Around a third of MM patients with del(17p) are also reported to have a TP53mutation, while this mutation is rare in the absence of del(17p). The prognostic impact of TP53mutations in the context of del(17p) is unresolved. We investigated the presence of TP53mutations in a cohort of del(17p) patients to correlate mutation status with clinical outcome. We assessed the types of TP53mutations, and the timing of mutations in relation to the acquisition of del(17p).

Immune based strategies have shown early promise in multiple myeloma (MM), and are likely to prove a valuable addition to the therapeutic platforms for these patients. B cell maturation antigen (BCMA) is a promising therapeutic target with selective expression on plasma cells, including MM cells. In the first report of BCMA targeting therapies, an anti-BCMA scFv-based chimeric antigen receptor (CAR) had clinical activity, albeit with short lived responses (Ali et al, 2016). Observed challenges included low expression level of BCMA, shedding of BCMA and potential loss of expression.