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Telitacicept (Tai'ai ® ) is fusion protein comprising a recombinant transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) receptor fused to the fragment crystallizable (Fc) domain of human immunoglobulin G (IgG). Telitacicept is being developed by Yantai Rongchang Pharmaceutical through its subsidiary RemeGen for the treatment of B cell-mediated autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and multiple sclerosis (MS). Telitacicept binds to and neutralizes the activity of two cell-signalling molecules, B-lymphocyte stimulator (BLyS) and a proliferation-inducing ligand (APRIL), thereby suppressing the development and survival of plasma cells and mature B cells. In March 2021, telitacicept received its first approval in China for the treatment of patients with active SLE. Clinical studies of telitacicept in several other indications, including IgA nephropathy, MS, myasthenia gravis, neuromyelitis optica spectrum disorders, RA and Sjögren's syndrome are underway in China. This article summarizes the milestones in the development of telitacicept leading to this first approval for SLE.

Objective To evaluate the effects of belimumab versus placebo, plus standard systemic lupus erythematosus (SLE) therapy, on organ domain-specific SLE disease activity. Methods Data obtained after 52 weeks of treatment from two phase III trials (BLISS-52 and BLISS-76) comparing belimumab 1 and 10 mg/kg versus placebo, plus standard therapy, in 1684 autoantibody-positive patients were analysed post hoc for changes in British Isles Lupus Assessment Group (BILAG) and Safety of Estrogens in Lupus National Assessment–Systemic Lupus Erythematosus Disease Activity Index (SELENA–SLEDAI) organ domain scores. Results At baseline, the domains involved in the majority of patients were musculoskeletal and mucocutaneous by both BILAG and SELENA–SLEDAI, and immunological by SELENA–SLEDAI. At 52 weeks, significantly more patients treated with belimumab versus placebo had improvement in BILAG musculoskeletal and mucocutaneous domains (1 and 10 mg/kg), and in SELENA–SLEDAI mucocutaneous (10 mg/kg), musculoskeletal (1 mg/kg) and immunological (1 and 10 mg/kg) domains. Improvement was also observed in other organ systems with a low prevalence (≤16%) at baseline, including the SELENA–SLEDAI vasculitis and central nervous system domains. Significantly fewer patients treated with belimumab versus placebo had worsening in the BILAG haematological domain (1 mg/kg) and in the SELENA–SLEDAI immunological (10 mg/kg), haematological (10 mg/kg) and renal (1 mg/kg) domains. Conclusions Belimumab treatment improved overall SLE disease activity in the most common musculoskeletal and mucocutaneous organ domains. Less worsening occurred in the haematological, immunological and renal domains.

ObjectivesTNF inhibitors (TNFi) can induce anti-drug antibodies (ADA) in patients with autoimmune diseases (AID) leading to clinical resistance. We explored a new way of using methotrexate (MTX) to decrease this risk of immunisation.MethodsWe treated BAFF transgenic (BAFFtg) mice, a model of AID in which immunisation against biologic drugs is high, with different TNFi. We investigated the effect of a single course of MTX during the first exposure to TNFi. Wild-type (WT) and BAFFtg mice were compared for B-Cell surface markers involved in MTX-related purinergic metabolism, adenosine production and regulatory B-cells (Bregs).We translated the study to macaques and patients with rheumatoid arthritis from the ABIRISK cohort to determine if there was an interaction between serum BAFF levels and MTX that prevented immuniation.ResultsIn BAFFtg but not in WT mice or macaques, a single course of MTX prevented immunisation against TNFi and maintained drug concentration for over 52 weeks. BAFFtg mice B-cells expressed more CD73 and CD39 compared to WT mice. MTX induced adenosine release from B cells and increased Bregs and precursors. Use of CD73 blocking antibodies reversed MTX-induced tolerance. In patients from the ABIRISK cohort treated with TNFi for chronic inflammatory diseases, high BAFF serum level correlated with absence of ADA to TNFi only in patients cotreated with MTX but not in patients on TNFi monotherapy.ConclusionMTX and BAFF interact in mice where CD73, adenosine and regulatory B cells were identified as key actors in this phenomenon. MTX and BAFF also interact in patients to prevent ADA formation.

Of note, this is also true for lupus nephritis studies, where outcome measures may seem easier to define. [...]it was recently demonstrated that the use of different renal outcome measures, performed on the same data set, leads to different conclusions regarding study drug efficacy. 11 The purpose of this editorial is obviously not to suggest that trials which missed their primary and key secondary outcomes are success stories!

The recent understanding of plasma cell (PC) biology has been obtained mainly from murine models. The current concept is that plasmablasts home to the BM and further differentiate into long-lived PCs (LLPCs). These LLPCs survive for months in contact with a complex niche comprising stromal cells (SCs) and hematopoietic cells, both producing recruitment and survival factors. Using a multi-step culture system, we show here the possibility to differentiate human memory B cells into LLPCs surviving for at least 4 months in vitro and producing immunoglobulins continuously. A remarkable feature is that IL-6 is mandatory to generate LLPCs in vitro together with either APRIL or soluble factors produced by SCs, unrelated to APRIL/BAFF, SDF-1, or IGF-1. These LLPCs are out of the cell cycle, express highly PC transcription factors and surface markers. This model shows a remarkable robustness of human LLPCs, which can survive and produce highly immunoglobulins for months in vitro without the contact with niche cells, providing the presence of a minimal cocktail of growth factors and nutrients. This model should be useful to understand further normal PC biology and its deregulation in premalignant or malignant PC disorders.

Background B cell activating factor belonging to the TNF family (BAFF) is vital for B cell survival, proliferation and activation. Evidence indicates that BAFF is systemically or locally increased in glomerulonephritis (e.g. lupus nephritis, IgA nephropathy). However, the effect of BAFF on human mesangial cells is not known. Methods The impact of BAFF on the proliferation of a human mesangial cell line in vitro was investigated. The expression of BAFF receptor (BAFF-R) and downstream signal transduction were explored. The influence of BAFF on the expression of related genes was also studied. Results Our data indicated that BAFF had a proliferative effect on human mesangial cells, as supported by the results of cell proliferation assays and the inhibited expression of the pro-apoptotic gene Bim. BAFF-R was expressed on the cell membrane of human mesangial cells and blockade of BAFF/BAFF-R binding abrogated the proliferative effect of BAFF on human mesangial cells. BAFF stimulation led to rapid phosphorylation of NF-κBp65, Akt and MAPK p38 kinase in human mesangial cells, whereas it had no effect on the expression of NF-κB p100 and phosphorylation of Erk. The phosphorylation of Akt was very sensitive to blockade of BAFF/BAFF-R ligation, although activation of MAPK p38 and NF-κBp65 was not. BAFF treatment resulted in decreased expression of BAFF-R, which implied negative feedback regulation after its binding. Conclusions BAFF promoted proliferation of human mesangial cells, which was mediated via BAFF-R. The BAFF/BAFF-R interaction triggered Akt, p65 and p38 activation, with Akt phosphorylation being tightly dependent on BAFF/BAFF-R interaction.

Testosterone deficiency in men is associated with increased risk for autoimmunity and increased B cell numbers through unknown mechanisms. Here we show that testosterone regulates the cytokine BAFF, an essential survival factor for B cells. Male mice lacking the androgen receptor have increased splenic B cell numbers, serum BAFF levels and splenic Baff mRNA. Testosterone deficiency by castration causes expansion of BAFF-producing fibroblastic reticular cells (FRCs) in spleen, which may be coupled to lower splenic noradrenaline levels in castrated males, as an α-adrenergic agonist decreases splenic FRC number in vitro. Antibody-mediated blockade of the BAFF receptor or treatment with the neurotoxin 6-hydroxydopamine revert the increased splenic B cell numbers induced by castration. Among healthy men, serum BAFF levels are higher in men with low testosterone. Our study uncovers a previously unrecognized regulation of BAFF by testosterone and raises important questions about BAFF in testosterone-mediated protection against autoimmunity. Testosterone deficiency is associated with autoimmunity and increased B cell numbers, but the underlying mechanism is unclear. Here the authors show that testosterone may modulate the production of B cell survival factor BAFF by fibroblastic reticular cells via regulation of splenic neurotransmitter levels.

Introduction Treatment with alemtuzumab is highly effective in relapsing–remitting multiple sclerosis; however, 30% of patients develop autoimmunity. Alemtuzumab (previously called Campath 1-H) induces a prolonged T-cell lymphopenia with memory cells dominating the reconstituting T-cell pool for at least 3 months. Results Here we show that B-cell recovery is rapid, returning to baseline by 3 months and rising to 165% of baseline by 12 months after treatment. Immature transitional 1 B cells are the predominant cell type 1 month after treatment. This coincides with a surge in serum B-cell activating factor (BAFF), which remains elevated by 33% for at least 12 months after alemtuzumab. BAFF is critical for transition to the mature naive B-cell phenotype, which dominates from 3 months after alemtuzumab. Differentiation to memory B cells is slow so there are radical and prolonged alterations to the B-cell pool after alemtuzumab.

ObjectivesTo evaluate the efficacy and safety of ianalumab (VAY736), a B cell-depleting, B cell activating factor receptor-blocking, monoclonal antibody, in patients with active primary Sjögren’s syndrome (pSS) in a double-blind, placebo-controlled, phase II, single-centre study.MethodsPatients with pSS, EULAR Sjögren’s Syndrome Disease Activity Index (ESSDAI) ≥6, were randomised to ianalumab single infusion at either 3 mg/kg (n=6), 10 mg/kg (n=12) or placebo (n=9). Outcomes were measured blinded at baseline and weeks 6, 12, 24, and unblinded at end of study (EoS) when B cell numbers had recovered. Clinical outcomes included ESSDAI, EULAR Sjögren’s Syndrome Patient Reported Index (ESSPRI), salivary flow rate, ocular staining score, physician global assessment and patient assessments of fatigue and general quality of life. Laboratory-based measures included circulating leucocyte subsets and markers of B cell activity.ResultsA similar trend showing positive therapeutic effect by ianalumab was observed across the primary clinical outcome (ESSDAI) and all secondary clinical outcomes (ESSPRI, Multidimensional Fatigue Inventory, Short Form-36, global assessments by physician and patient) versus the placebo-treated group. Rapid and profound B cell depletion of long-lasting duration occurred after a single infusion of ianalumab at either dose. Serum Ig light chains decreased, with return to baseline levels at EoS. Changes in some clinical outcomes persisted through to EoS in the higher dose group. Adverse effects were largely limited to mild to moderate infusion reactions within 24 hours of ianalumab administration.ConclusionsOverall results in this single-dose study suggest potent and sustained B cell depletion by ianalumab could provide therapeutic benefits in patients with pSS without major side effects.