Depletion Of Plasma Cells Research Articles

Proteasome inhibition induces p53 driven apoptosis in early activated B-cells

Abstract Proteasome inhibition is a useful therapeutic strategy against plasma cell disorders in autoimmunity, neoplasias, and transplant rejection. However, how bortezomib induces cell death and the transcription factors that are involved in its execution are not well characterized. In this study, we aim to address the mechanism of action of proteasome inhibitors in plasma cells and in early precursor activated B-cells. We immunized mice with the hapten-protein conjugate nitrophenyl chicken-gamma-globulin (NP-CGG) and validated depletion of plasma cells and germinal center B-cells in vivo. At steady-state, we utilized B220 expression as a surface marker for newly-formed plasma cells and determined that bortezomib primarily depletes newly-formed plasma cells. To gain more mechanistic insight on how bortezomib affects newly-formed plasma cells, we employed an in vitro culture system of murine-derived primary follicular B-cells that were stimulated with CPG, IL-4, and IL5, to promote differentiation into the plasma cell fate. We find that deletion of the ER-stress induced transcription factor CHOP rescued in vitro generated plasma cells from low-dose bortezomib treatment. In addition, we identify the transcription factor p53 as a key inducer of apoptosis in in vitro generated early activated B-cells. Deletion of p53 rescued cells from apoptosis and reduced the number of cells expressing cleaved caspase-3 in response to bortezomib treatment. In conclusion, we have identified two transcription factors that are involved in bortezomib-induced cell death in B-lineage cells. Supported by NIAID Diversity Supplement: R01AI139123

Inflammation depletes humoral immunity by limiting plasma cell access to the bone marrow survival niche

Abstract The survival of plasma cells (PCs) is directly correlated to the longevity of prophylactic titers against pathogens. The bone marrow contains hematopoietic and non-hematopoietic cells that contribute to the maintenance of PCs. Studies have shown that pathogens contain a variety of mechanisms that result in the depletion of bone marrow PCs and antibody titers. Most, if not all, forms of infection induce inflammation, however, the role of inflammation in bone marrow PC depletion is unclear. Here, we show that acute Tumor Necrosis Factor Alpha (TNFa) treatment can deplete pre-existing antibody titers in a variety of models. We also found that recombinant TNFa treatment limits PC retention in the bone marrow via adoptive transfer experiments. To determine if PC retention in the bone marrow was mediated in a cell-intrinsic or − extrinsic manner, we generated bone marrow chimeras with wild-type and TNFa receptor knockout mice. Results showed that TNFa signaling through TNFa receptor 1 in non-hematopoietic cells regulates PC retention in the bone marrow, indicating that this mechanism is cell-extrinsic. Another cell-extrinsic mechanism that we identified is TNFa regulation of syndecan-1, a cell surface proteoglycan found to regulate PC survival and motility. These findings demonstrate that inflammation limits PC access to the bone marrow survival niche, ultimately leading to the reduction of antibody titers and long-term humoral protection. Supported by grants from the NIH (R01 HLI141491) and the Eric Heyer M.D. Ph.D Translational Research Grant

Daratumumab for treatment-refractory antibody-mediated diseases in neurology.

A fraction of patients with antibody-mediated autoimmune diseases remain unresponsive to first-/second-line and sometimes even to escalation immunotherapies. Because these patients are still affected by poor outcome and increased mortality, we investigated the safety and efficacy of the plasma cell-depleting anti-CD38 antibody daratumumab in life-threatening, antibody-mediated autoimmune diseases. In this retrospective, single-center case series, seven patients with autoantibody-driven neurological autoimmune diseases (autoimmune encephalitis, n=5; neurofascin antibody-associated chronic inflammatory demyelinating polyneuropathy associated with sporadic late onset nemaline myopathy, n=1; seronegative myasthenia gravis, n=1) unresponsive to a median of four (range = 4-9) immunotherapies were treated with four to 20 cycles of 16mg/kg daratumumab. Daratumumab allowed a substantial clinical improvement in all patients, as measured by modified Rankin Scale (mRS; before treatment: mRS=5, n=7; after treatment: median mRS=4, range = 0-5), Clinical Assessment Scale in Autoimmune Encephalitis (from median 21 to 3 points, n=5), Inflammatory Neuropathy Cause and Treatment disability score (from 7 to 0 points, n=1), and Quantitative Myasthenia Gravis score (from 16 to 8 points, n=1). Daratumumab induced a substantial reduction of disease-specific autoreactive antibodies, total IgG (serum, 66%, n=7; cerebrospinal fluid, 58%, n=5), and vaccine-induced titers for rubella (50%) and tetanus toxoid (74%). Treatment-related toxicities Grade 3 or higher occurred in five patients, including one death. Our findings suggest that daratumumab provided a clinically relevant depletion of autoreactive long-lived plasma cells, identifying plasma cell-targeted therapies as promising escalation therapy for highly active, otherwise treatment-refractory autoantibody-mediated neurological diseases.

Quick preparation of ABO-incompatible living donor liver transplantation for acute liver failure.

Acute liver failure is life-threatening and has to be treated by liver transplantation urgently. When deceased donors or ABO-compatible living donors are not available, ABO-incompatible (ABO-I) living donor liver transplantation (LDLT) becomes the only choice. How to prepare ABO-I LDLT urgently is an unsolved issue. A quick preparation regimen was designed, which was consisted of bortezomib (3.5mg) injection to deplete plasma cells and plasma exchange to achieve isoagglutinin titer ≤ 1: 64 just prior to liver transplantation and followed by rituximab (375mg/m2 ) on post-operative day 1 to deplete B-cells. Eight patients received this quick preparation regimen to undergo ABO-I LDLT for acute liver failure from 2012 to 2019. They aged between 50 and 60years. The median MELD score was 39 with a range from 35 to 48. It took 4.75 ± 1.58 days to prepare such an urgent ABO-I LDLT. All the patients had successful liver transplantations, but one patient died of antibody-mediated rejection at post-operative month 6. The 3-month, 6-month, and 1-year graft/patient survival were 100%, 87.5%, and 75%, respectively. In conclusion, this quick preparation regimen can reduce isoagglutinin titers quickly and make timely ABO-I LDLT feasible for acute liver failure.

Clinical Relevance of Isoagglutinin Rebound in Adult ABO-Incompatible Living Donor Liver Transplantation.

ABO-incompatible (ABO-I) living donor liver transplantation (LDLT) can be performed successfully. However, anti-ABO isoagglutinin rebound may cause antibody-mediated rejection (AMR) and graft loss. The risk threshold of isoagglutinin rebound is still not defined. 76 ABO-I LDLT recipients were divided into group A (n = 56) with low isoagglutinin titers (<1:256), and group B (n = 20) with high isoagglutinin titers (≥1:256), at initial assessment for liver transplantation. The last 12 patients in group B received a modified desensitization regimen by adding bortezomib to deplete plasma cells. Six (10.7%) patients in group A and 10 (50.0%) patients in group B had postoperative isoagglutinin rebound (p < 0.001). Three patients (5.54%) in group A and two patients (10%) in group B developed clinical AMR (p = 0.602). The cutoff value of postoperative isoagglutinin rebound to cause clinical AMR was ≥1:1024. Among the 12 patients in group B with bortezomib administration, isoagglutinin rebounded up to 1:128 only, and no clinical AMR occurred. In conclusion, the patients with high isoagglutinin titers had a higher rate of postoperative isoagglutinin rebound. Isoagglutinin rebound ≥1:1024 is risky for developing clinical AMR. Adding bortezomib into the desensitization regimen may mitigate isoagglutinin rebound, and avoid clinical AMR.

HDAC11 Is a Candidate Therapeutic Target in Multiple Myeloma

Background: Histone deacetylase (HDAC) inhibitors (HDI), although only marginally active as single agent therapy in multiple myeloma (MM), demonstrate an ability to salvage proteasome inhibitors (PIs) and immunomodulatory drugs (IMiDs) responsiveness in refractory patients, thus raising interest in this class of targeted therapeutics. Selective inhibition of particular HDAC isoforms may further improve therapeutic efficacy. HDAC11, the newest member of the HDAC family, is expressed in a progressive manner during B cell development with greatest expression in mature plasma cells (PC).Methods: B cell lymphopoiesis was evaluated using Tg-HDAC11-eGFP mice expressing eGFP regulated by the HDAC11 promoter and congenic mouse strains deficient in HDAC11 expression globally (B6.HDAC11-/-) or targeted to the B cell lineage (CD19Cre.HDAC11-/-). In vitro assays were completed using established human myeloma cell lines that include RPMI-8226, RPMI-8226-B25, OPM2, H929, KMS11, KMS28, KAS6, KAS6R10R, MM1.S, and MM1R10R (kind gift from Dr. Orlowski). Inhibition of HDAC11 in MM cell lines was accomplished by both molecular and pharmacologic approaches. Viability was measured according to activated caspase-3 and Annexin/PI staining by flow cytometry, and by CCK-8 viability assay. Subcellular localization changes induced by HDI exposure were assessed by Western Blot of fractionated cell lysates, while immunoprecipitation and confocal microscopy, using both immunofluorescence and proximity ligation assay techniques, were used to identify IRF4 as a novel nuclear binding partner for HDAC11.Results: Profound eGFP increases in PC of Tg-HDAC11-eGFP mice suggest HDAC11 influences late stage B cell development. Consistent with this, HDAC11 deficiency results in dramatically reduced PC in the bone marrow and periphery. PC depletion in CD19Cre.HDAC11-/- mice, where HDAC11 ablation is restricted to the B cell lineage, suggests activity inherent in B cells rather than via externally derived signals. Initial studies evaluating the effects of quisinostat, a second-generation HDI with increased selectivity that includes HDAC11, showed dose-dependent cytotoxicity versus 10 myeloma cell lines with EC50 measurements in the 1-10nM range. This activity was synergistic with BTZ and carfilzomib (CFZ) in RPMI-8226 cells and degree of synergism was amplified in the BTZ-resistant RPMI-8226-B25 cell line. Subsequent experiments using HDTK-010 (FORMA Therapeutics), an HDAC11-selective HDI, showed dose-dependent cytotoxicity in 21 MM cell lines (EC50 1-10mM). Targeted siRNA-mediated silencing of HDAC11 in RPMI-8226 cells yielded a reduction in cell viability, as measured by Annexin/PI staining and detection of activated caspase-3. An important interaction between HDAC11 and IRF4, an essential regulator of PC differentiation and MM survival, was first identified by immunoprecipitation assay in 8226 cells. This interaction has been confirmed by confocal microscopy using immunofluorescent co-localization and proximity ligation techniques in 8226, MM1.S, OPM2 and H929 cell lines as well as in CD138-enriched MM cells from patient marrow aspirates. Furthermore, this interaction is disrupted by exposure to quisinostat, panobinostat, and HDTK-010. The identification of IRF4 as a putative binding partner for HDAC11 unveils a potential mechanism by which HDAC11 may regulate MM cell survival.Conclusions:We show that MM cell survival can be impaired by targeted inhibition of HDAC11. Furthermore, we identify IRF4 as a nuclear binding partner for HDAC11 and propose this interaction as a candidate mechanism regulating PC maturation and MM cell survival. DisclosuresBaz:Sanofi: Research Funding; BMS: Research Funding; merck: Research Funding; takeda: Research Funding; celgene: Honoraria, Research Funding; karyopharm: Research Funding. Pinilla-Ibarz:ARIAD: Consultancy, Honoraria; BMS: Honoraria, Speakers Bureau; Pfizer: Honoraria, Speakers Bureau.

HLA Desensitization in Solid Organ Transplantation: Anti-CD38 to Across the Immunological Barriers.

The presence of anti-human leucocyte antigen (HLA) antibodies in the potential solid organ transplant recipient’s blood is one of the main barriers to access to a transplantation. The HLA sensitization is associated with longer waitlist time, antibody mediated rejection and transplant lost leading to increased recipient’s morbidity and mortality. However, solid organ transplantation across the HLA immunological barriers have been reported in recipients who were highly sensitized to HLA using desensitization protocols. These desensitization regimens are focused on the reduction of circulating HLA antibodies. Despite those strategies improve rates of transplantation, it remains several limitations including persistent high rejection rate and worse long-term outcomes when compare with non-sensitized recipient population. Currently, interest is growing in the development of new desensitization approaches which, beyond targeting antibodies, would be based on the modulation of alloimmune pathways. Plasma cells appears as an interesting target given their critical role in antibody production. In the last decade, CD38-targeting immunotherapies, such as daratumumab, have been recognized as a key component in the treatment of myeloma by inducing an important plasma cell depletion. This review focuses on an emerging concept based on targeting CD38 to desensitize in the field of transplantation.

The Immunomodulatory Effect and Clinical Efficacy of Daratumumab in a Patient With Cold Agglutinin Disease

Daratumumab is a monoclonal antibody directed against the transmembrane glycoprotein CD38 expressed on plasma cells and lymphoplasmocytes, with a proven efficacy in multiple myeloma. Here we show its clinical efficacy in a patient with cold agglutinin disease (CAD) relapsed after multiple lines of therapy. CAD is caused by cold reactive autoantibodies that induce complement mediated hemolysis and peripheral circulatory symptoms. The disease is also characterized by the presence of monoclonal IgM gammopathy and of a lymphoid bone marrow infiltration that benefits from B-cell targeting therapies (i.e., rituximab) but also from plasma cell directed therapies, such as proteasome inhibitors. In the patient described, we also show that daratumumab therapy influenced the dynamics of several immunoregulatory cytokine levels (IL-6, IL-10, IL-17, IFN-γ, TNF-α, TGF-β) indicating an immunomodulatory effect of the drug beyond plasma cell depletion. In addition, we provide a literature review on the use of daratumumab in autoimmune conditions, including multi-treated and refractory patients with autoimmune hemolytic anemia (both CAD and warm forms), Evans syndrome (association of autoimmune hemolytic anemia and immune thrombocytopenia) and non-hematologic autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis.

Early Experience of ABO-incompatible Living Donor Liver Transplantation in Haeundae Paik Hospital

Introduction: ABO-incompatible LDLT (ABOi-LDLT) could be a useful option for expanding pool of available organs. Since the introduction of rituximab in ABOi-LDLT, the incidence of AMR dropped dramatically and the paradigm of ABOi-LDLT in adult patients has changed. Methods: We would like to present our initial experience of three cases of ABOi-LDLT. The protocol includes a single dose of rituximab (300 mg/m2) 3 weeks before transplantation, several sessions of plasmapheresis to decrease the isoagglutinin (IA) titer to ≤ 1:32, and a triple immunosuppressive regimen consisting of tacrolimus, mycophenolate mofetil, and steroid. Results: All three patients performed a relatively large number of plasmapheresis to reach the target IA titers (16, 19, and 7 sessions, respectively). The IA titers immediately before transplantation were 32, 1024 and 128, respectively, while the peak titers during post-transplant period were 32, 128, and 32, respectively. In particular, case 2 patient has severe rebound elevation of IA titer even after administration of Bortezomib, a proteasome inhibitor that depletes plasma cells. As for this patient, we should perform LDLT at an IA titer 1:1024 with splenectomy and prophylactic intravenous immunoglobulin. Two patients (case 1, 2) are alive with no evidence of AMR until now, but one patient (case 3) died at POD51 due to hepatic artery thrombosis and sepsis. Conclusions: Rituximab-based protocol is a cornerstone in the regimens of desensitization for ABOi-LDLT, but more study on pre-transplant target IA titer and effectiveness of pre-transplant plasmapheresis needs to be continued as seen in the present cases.

Shiga-Like Toxin-1 Receptor on Human Breast Cancer, Lymphoma, and Myeloma and Absence From CD34+ Hematopoietic Stem Cells: Implications for Ex Vivo Tumor Purging and Autologous Stem Cell Transplantation

The ribosome-inactivating protein, Shiga-like toxin-1 (SLT-1), targets cells that express the glycolipid globotriaosylceramide (CD77) on their surface. CD77 and/or SLT-1 binding was detected by flow cytometry and immunocytochemistry on lymphoma and breast cancer cells recovered from biopsies of primary human cancers as well as on B cells or plasma cells present in blood/bone marrow samples of multiple myeloma patients. Breast cancer cell lines also expressed receptors for the toxin and were sensitive to SLT-1. Treatment of primary B lymphoma, B-cell chronic lymphocytic leukemia, and myeloma B or plasma cells with SLT-1-depleted malignant B cells by 3- to 28-fold, as measured by flow cytometry. Depletion of myeloma plasma cells was confirmed using a cellular limiting dilution assay followed by reverse transcriptase-polymerase chain reaction analysis of clonotypic IgH transcripts, which showed a greater than 3 log reduction in clonotypic myeloma cells after SLT-1 treatment. Receptors for the toxin were not detected on human CD34(+) hematopoietic progenitor cells (HPC). HPC were pretreated with a concentration of SLT-1 known to purge primary malignant B cells and cultured for 6 days. The number of HPC was comparable in toxin-treated and untreated cultures. HPC were functionally intact as well. Colony-forming units (CFU) were present at an identical frequency in untreated and SLT-1 pretreated cultures, confirming that CFU escape SLT-1 toxicity. The results suggest the ex vivo use of SLT-1 in purging SLT-1 receptor-expressing malignant cells from autologous stem cell grafts of breast cancer, lymphoma, and myeloma patients.

COVID-19: B-Cell Depletion and Sepsis Related Changes in Bone Marrow and Spleen

COVID-19: B-Cell Depletion and Sepsis Related Changes in Bone Marrow and Spleen

Gut-educated IgA plasma cells defend the meningeal venous sinuses.

The central nervous system has historically been viewed as an immune-privileged site, but recent data have shown that the meninges-the membranes that surround the brain and spinal cord-contain a diverse population of immune cells1. So far, studies have focused on macrophages and T cells, but have not included a detailed analysis of meningeal humoral immunity. Here we show that, during homeostasis, the mouse and human meninges contain IgA-secreting plasma cells. These cells are positioned adjacent to dural venous sinuses: regions of slow blood flow with fenestrations that can potentially permit blood-borne pathogens to access the brain2. Peri-sinus IgA plasma cells increased with age and following a breach of the intestinal barrier. Conversely, they were scarce in germ-free mice, but their presence was restored by gut re-colonization. B cell receptor sequencing confirmed that meningeal IgA+ cells originated in the intestine. Specific depletion of meningeal plasma cells or IgAdeficiency resulted in reduced fungal entrapment in the peri-sinus region and increased spread into the brain following intravenous challenge, showing that meningeal IgA is essential for defending the central nervous system at this vulnerable venous barrier surface.

Targeting CD38 with Daratumumab in Refractory Systemic Lupus Erythematosus

SummaryDaratumumab, a human monoclonal antibody that targets CD38, depletes plasma cells and is approved for the treatment of multiple myeloma. Long-lived plasma cells are implicated in the pathogenesis of systemic lupus erythematosus because they secrete autoantibodies, but they are unresponsive to standard immunosuppression. We describe the use of daratumumab that induced substantial clinical responses in two patients with life-threatening lupus, with the clinical responses sustained by maintenance therapy with belimumab, an antibody to B-cell activating factor. Significant depletion of long-lived plasma cells, reduction of interferon type I activity, and down-regulation of T-cell transcripts associated with chronic inflammation were documented. (Supported by the Deutsche Forschungsgemeinschaft and others.)

AMG 701 induces cytotoxicity of multiple myeloma cells and depletes plasma cells in cynomolgus monkeys

AbstractMultiple myeloma (MM) is a hematologic malignancy that is characterized by the accumulation of abnormal plasma cells (PCs) in the bone marrow (BM). Patient outcome may be improved with BiTE (bispecific T-cell engager) molecules, which redirect T cells to lyse tumor cells. B-cell maturation antigen (BCMA) supports PC survival and is highly expressed on MM cells. A half-life extended anti-BCMA BiTE molecule (AMG 701) induced selective cytotoxicity against BCMA-expressing MM cells (average half-maximal effective concentration, 18.8 ± 14.8 pM), T-cell activation, and cytokine release in vitro. In a subcutaneous mouse xenograft model, at all doses tested, AMG 701 completely inhibited tumor formation (P < .001), as well as inhibited growth of established tumors (P ≤ .001) and extended survival in an orthotopic MM model (P ≤ .01). To evaluate AMG 701 bioactivity in cynomolgus monkeys, a PC surface phenotype and specific genes were defined to enable a quantitative digital droplet polymerase chain reaction assay (sensitivity, 0.1%). Dose-dependent pharmacokinetic and pharmacodynamic behavior was observed, with depletion of PC-specific genes reaching 93% in blood and 85% in BM. Combination with a programmed cell death protein 1 (PD-1)–blocking antibody significantly increased AMG 701 potency in vitro. A model of AMG 701 binding to BCMA and CD3 indicates that the distance between the T-cell and target cell membranes (ie, the immunological synapse) is similar to that of the major histocompatibility complex class I molecule binding to a T-cell receptor and suggests that the synapse would not be disrupted by the half-life extending Fc domain. These data support the clinical development of AMG 701.

Generate-Boost: study protocol for a prospective, multicenter, randomized controlled, double-blinded phase II trial to evaluate efficacy and safety of bortezomib in patients with severe autoimmune encephalitis

BackgroundAutoimmune encephalitis is a new spectrum of autoimmune disorders of the central nervous system (CNS), which are characterized by pathogenic autoantibodies against neuronal surface antigens. Clinical presentations range from acute to subacute encephalopathy with neurological and psychiatric symptoms, and life-threatening autonomic dysfunction in severe cases. There exist no approved therapies nor is data available from controlled clinical trials. Patients are usually treated with diverse combinations of immunotherapy. However, effect of immunotherapy on antibody-producing cells and thus on levels of pathogenic autoantibodies is insufficient. Therefore, therapeutic response is sometimes prolonged with necessity of long-time intensive care treatment and also irreversible deficits occur in severe cases. This trial will investigate the efficacy and safety of bortezomib, a proteasome inhibitor known to selectively deplete plasma cells, in patients with severe autoimmune encephalitis who have been treated with rituximab with insufficient response.MethodsGenerate-Boost is an investigator-initiated, multicenter, double-blinded, randomized controlled phase II trial which will be conducted in specialized neurological hospitals within the GENERATE (GErman NEtwork for Research on AuToimmune Encephalitis) network in Germany. Adult patients with severe autoimmune encephalitis (modified Rankin scale, mRS ≥ 3), autoantibodies against neuronal surface antigens, and pretreatment with rituximab are eligible for study participation. Fifty patients will be randomized 1:1 and undergo up to 3 cycles (each 21 days with 4 s. c. applications) of bortezomib or placebo. All patients will receive concomitant medication with dexamethasone, acyclovir and co-trimoxazole. The primary efficacy endpoint is the mRS score 17 weeks after first treatment application. Secondary endpoints are neurocognitive function, antibody titers, markers of neuronal cell damage, length of ICU/hospital stay, and mRS and Glasgow coma scale scores throughout the trial up to week 17. General and bortezomib-specific adverse events are monitored continuously.DiscussionThe expected outcome of the study is to obtain first reliable data on a hypothesis-driven therapeutic option in severe and difficult-to-treat autoimmune encephalitis. If treatment with bortezomib is beneficial in these cases, this will be the basis for implementation in the current guidelines.Trial registrationClinicaltrials.gov, NCT03993262. Registered June 20, 2019;German Clinical Trials Register, DRKS00017497.

GO39775: A multicenter phase I trial evaluating the safety, pharmacokinetics, and activity of BFCR4350A, a FcRH5/CD3 T-cell dependent bispecific antibody, in patients with relapsed or refractory multiple myeloma.

TPS8551 Background: Multiple myeloma (MM) remains an incurable disease, with estimated median survival of 8–9 months in patients with relapsed or refractory (R/R) disease (Kumar et al. 2014; Usmani et al. 2016). There is no uniform standard of care for R/R MM, and combinations used in later lines have diminishing responses, especially after re-exposure to previously received classes of therapy (Gandhi et al. 2019). New targets and treatment modalities are needed. Fragment crystallizable receptor-like 5 (FcRH5) is expressed on myeloma cells across lines of therapy, and is overexpressed by myeloma cells with 1q21 gain; expression in healthy tissue is restricted to the B-cell lineage, and is retained in plasma cells (Li et al. 2017). BFCR4350A is an IgG-based T-cell-dependent bispecific antibody that was specifically engineered to target the most membrane-proximal domain of FcRH5 on myeloma cells and cluster of differentiation 3 (CD3) on T cells, with dual binding resulting in efficient immune synapse formation and T-cell killing of myeloma cells. BFCR4350A demonstrates potent killing of plasma cells and patient-derived myeloma cells (including those with low levels of FcRH5 expression) in vitro, and complete depletion of bone marrow plasma cells in primates, without severe or prolonged cytokine release (Li et al. 2017). GO39775 (NCT03275103) is an open-label, multicenter Phase I dose-escalation and dose-expansion trial evaluating the safety, pharmacokinetics (PK), and activity of BFCR4350A monotherapy in patients with R/R MM. Methods: Patients must be aged ≥18 years and must have R/R MM for which no established therapies are available or appropriate, or be intolerant to those therapies. Patients with prior CAR-T therapy and/or prior BCMA-directed therapy are not excluded. BFCR4350A is administered by intravenous infusion, and q3w dosing with Cycle 1 single-step or multi-step dosing is being investigated in dose-escalation (Arms A and B, respectively). Enrolment into both arms is ongoing, with patients receiving up to 17 cycles of treatment until disease progression or unacceptable toxicity. Primary objectives are to evaluate safety (including the maximum tolerated dose and dose-limiting toxicities) and to identify a recommended Phase II dose. Secondary objectives include assessment of PK, activity, immunogenicity, and pharmacodynamic biomarkers. Clinical trial information: NCT03275103 .

CD38, a Receptor with Multifunctional Activities: From Modulatory Functions on Regulatory Cell Subsets and Extracellular Vesicles, to a Target for Therapeutic Strategies.

CD38 is a multifunctional cell surface protein endowed with receptor/enzymatic functions. The protein is generally expressed at low/intermediate levels on hematological tissues and some solid tumors, scoring the highest levels on plasma cells (PC) and PC-derived neoplasia. CD38 was originally described as a receptor expressed by activated cells, mainly T lymphocytes, wherein it also regulates cell adhesion and cooperates in signal transduction mediated by major receptor complexes. Furthermore, CD38 metabolizes extracellular NAD+, generating ADPR and cyclic ADPR. This ecto-enzyme controls extra-cellular nucleotide homeostasis and intra-cellular calcium fluxes, stressing its relevance in multiple physiopathological conditions (infection, tumorigenesis and aging). In clinics, CD38 was adopted as a cell activation marker and in the diagnostic/staging of leukemias. Quantitative surface CD38 expression by multiple myeloma (MM) cells was the basic criterion used for therapeutic application of anti-CD38 monoclonal antibodies (mAbs). Anti-CD38 mAbs-mediated PC depletion in autoimmunity and organ transplants is currently under investigation. This review analyzes different aspects of CD38’s role in regulatory cell populations and how these effects are obtained. Characterizing CD38 functional properties may widen the extension of therapeutic applications for anti-CD38 mAbs. The availability of therapeutic mAbs with different effects on CD38 enzymatic functions may be rapidly translated to immunotherapeutic strategies of cell immune defense.

Selective depletion of plasma cells in vivo based on the specificity of their secreted antibodies.

Antibody-mediated diseases affect more than 10% of the human population. For most, no cure is available, particularly when the pathogenic antibodies are secreted by long-lived plasma cells resistant to conventional immunosuppressive therapies. Current therapeutic approaches target not only the plasma cells that secrete pathogenic antibodies, but also those providing protective antibodies. Here, in a murine model bearing long-lived plasma cells secreting anti-OVA and -chicken gamma globulin (CGG) antibodies, we describe the first-time use of an antigen-antibody (OVA/anti-CD138 antibody) conjugate for in vivo labeling and selective ablation of plasma cells that secrete antibodies specific for the antigen OVA. The selective depletion also led to a stable reduction of the corresponding serum anti-OVA antibody levels. In contrast, CGG-specific plasma cells and circulating anti-CGG antibody levels remained unchanged. The method described here should enable the development of unique causative treatment strategies for established antibody-mediated diseases sparing humoral immunity.

Plasma Cells Are Obligate Effectors of Enhanced Myelopoiesis in Aging Bone Marrow

Aging results in increased myelopoiesis, which is linked to the increased incidence of myeloid leukemias and production of myeloid-derived suppressor cells. Here, we examined the contribution of plasma cells (PCs) to age-related increases in myelopoiesis, as PCs exhibit immune regulatory function and sequester in bone marrow (BM). PC number was increased in old BM, and they exhibited high expression of genes encoding inflammatory cytokines and pathogen sensors. Antibody-mediated depletion of PCs from old mice reduced the number of myeloid-biased hematopoietic stem cells and mature myeloid cells to levels in young animals, but lymphopoiesis was not rejuvenated, indicating that redundant mechanisms inhibit that process. PCs also regulated the production of inflammatory factors from BM stromal cells, and disruption of the PC-stromal cell circuitry with inhibitors of the cytokines IL-1 and TNF-α attenuated myelopoiesis in old mice. Thus, the age-related increase in myelopoiesis is driven by an inflammatory network orchestrated by PCs.

Emerging roles of adjunct therapies in acquired thrombotic thrombocytopenia purpura.

Acquired thrombotic thrombocytopenia purpura (aTTP) is caused by autoantibody-mediated severe deficiency of the von Willebrand factor (vWF) cleaving protease ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13), with subsequent accumulation of ultra-large vWF-multimers that spontaneously form platelet-VWF complexes and microthrombi within the microcirculation. Therapeutic plasma exchange (TPE), by removing autoantibodies and excess ultra-large vWF multimers and replenishing ADAMTS13 activity, remains the urgent primary initial treatment. Although heterogeneity in treatment exists, most centers add upfront immunosuppression with steroids, and many also add upfront rituximab. Refractoriness, exacerbation and relapse are commonly treated with adjunct rituximab. Despite adjunct steroids and rituximab, TTP refractoriness, exacerbation, relapse, morbidity, and mortality remain problematic. Newer adjunct therapies include suppression of ADAMTS13 autoantibody production via plasma cell depletion, inhibition of vWF-platelet interaction, and replenishment of ADAMTS13 function with recombinant ADAMTS13 protein.