A Three-Part, Randomised Study to Investigate the Safety, Tolerability, Pharmacokinetics and Mode of Action of BC 007, Neutraliser of Pathogenic Autoantibodies Against G-Protein Coupled Receptors in Healthy, Young and Elderly Subjects.

BACKGROUND AND OBJECTIVE: BC 007 is a substance with a novel and innovative mode of action for the first-time causal treatment of chronic heart failure, associated with the occurrence of autoantibodies against the ß1-adrenoceptor, and other diseases of mostly the heart and vascular system, being accompanied by the occurrence of functionally active agonistic autoantibodies against G-protein-coupled receptors (fGPCR-AAb). The proposed mechanism of action of BC 007 is the neutralisation of these pathogenic autoantibodies which stimulate the respective receptor. To evaluate the safety, tolerability, pharmacokinetics and mode of action of BC 007, single intravenous infusions of increasing concentration were given to healthy young males and healthy elderly autoantibody-negative and autoantibody-positive participants of both sexes. METHODS: This study was subdivided into three parts. Part A was a single-centre, randomised, double-blind, placebo-controlled safety and tolerability study including healthy young male autoantibody-negative Whites (N = 23) and Asians (N = 1), testing doses of 15, 50 and 150 mg BC 007 (Cohorts 1-3) and elderly male and female Whites (N = 8), testing a dose of 150 mg BC 007 (Cohort 4), randomly assigned in a 3:1 ratio to BC 007 or placebo. Open-label Part B included fGPCR-AAb-positive subjects (50 and 150 mg BC 007, Cohorts 1 and 2, respectively). Open-label Part C included fGPCR-AAb-positive subjects for testing doses of 300, 450, 750, 1350 mg and 1900 mg BC 007. Lower doses were either given as an infusion or divided into a bolus plus infusion up to a dose of 300 mg followed by a constant bolus of 150 mg up to a dose of 750 mg, while at doses of 1350 mg and 1900 mg it was a slow infusion with a constant infusion rate. Infusion times increased with increasing dose from 20 min (15, 50 or 150 mg) to 40 min (300, 450 or 750 mg), 75 min (1350 mg) and 105 min (1900 mg). RESULTS: The mean observed BC 007 area under the concentration-time curve (AUC0-24) increased with increasing dose in a dose proportional manner (slope estimate of 1.039). No serious adverse events were observed. Drug-related adverse events were predominantly the expected mild-to-moderate increase in bleeding time (aPTT), beginning with a dose of 50 mg, which paralleled the infusion and returned to normal shortly after infusion. fGPCR-AAb neutralisation efficiency increased with increasing dose and was achieved for all subjects in the last cohort. CONCLUSION: BC 007 is demonstrated to be safe and well tolerated. BC 007 neutralised fGPCR-AAb, showing a trend for a dose-response relationship in elderly healthy but fGPCR-AAb-positive subjects. CLINICALTRIALS. GOV REGISTRATION NUMBER: NCT02955420.

RNA interference: the molecular immune system.

Introduction of double-stranded RNA (dsRNA) into cells expressing a homologous gene triggers RNA interference (RNAi), or RNA-based gene silencing (RBGS). The dsRNA degrades corresponding host mRNA into small interfering RNAs (siRNAs) by a protein complex containing Dicer. siRNAs in turn are incorporated into the RNA-induced silencing complex (RISC) that includes helicase, RecA, and exo- and endo-nucleases as well as other proteins. Following its assembly, the RISC guides the RNA degradation machinery to the target RNAs and cleaves the cognate target RNA in a sequence-specific, siRNA-dependent manner. RNAi has now been documented in a wide variety of organisms, including plants, fungi, flies, worms, and more recently, higher mammals. In eukaryotes, dsRNA directed against a range of viruses (i.e., HIV-1, RSV, HPV, poliovirus and others) and endogenous genes can induce sequence-specific inhibition of gene expression. In invertebrates, RNAi can be efficiently triggered by either long dsRNAs or 21- to 23-nt-long siRNAs. However, in jawed vertebrates, dsRNA longer than 30 bp can induce interferon and thus trigger undesirable side effects instead of initiating RNAi. siRNAs have been shown to act as potent inducers of RNAi in cultured mammalian cells. Many investigators have suggested that siRNAs may have evolved as a normal defense against endogenous and exogenous transposons and retroelements. Through a combination of genetic and biochemical approaches, some of the mechanisms underlying RNAi have been described. Recent data in C. elegans shows that two homologs of siRNAs, microRNAs (miRNAs) and tiny noncoding RNAs (tncRNAs) are endogenously expressed. However, many aspects of RNAi-induced gene silencing, including its origins and the selective pressures which maintain it, remain undefined. Its evolutionary history may pass through the more primitive immune functions of prokaryotes involving restriction enzymes that degrade plasmid DNA molecules that enter bacterial cells. RNAi has evolved further among eukaryotes, in which its wide distribution suggests early origins. RNAi seems to be involved in a variety of regulatory and immune functions that may differ among various kingdoms and phyla. We present here proposed mechanisms by which RBGS protects the host against endogenous and exogenous transposons and retroelements. The potential for therapeutic application of RBGS technology in treating viral infections such as HIV is also discussed.

A subset of Toll-like receptor ligands induces cross-presentation by bone marrow-derived dendritic cells.

Dendritic cells (DCs) are capable of cross-presenting exogenous Ag to CD8(+) CTLs. Detection of microbial products by Toll-like receptors (TLRs) leads to activation of DCs and subsequent orchestration of an adaptive immune response. We hypothesized that microbial TLR ligands could activate DCs to cross-present Ag to CTLs. Using DCs and CTLs in an in vitro cross-presentation system, we show that a subset of microbial TLR ligands, namely ligands of TLR3 (poly(inosinic-cytidylic) acid) and TLR9 (immunostimulatory CpG DNA), induces cross-presentation. In contrast to presentation of Ag to CD4(+) T cells by immature DCs, TLR-induced cross-presentation is mediated by mature DCs, is independent of endosomal acidification, and relies on cytosolic Ag processing machinery.

Cutting edge: a crucial role for B7-CD28 in transmitting T help from APC to CTL.

Although APC activation via CD40-CD40L signaling plays a critical role in enabling CD4(+) T cells to provide the "help" necessary for cross-priming of naive CTL, it is unclear how this makes the APC competent for priming. We have investigated the roles of B7-1/B7-2 and their receptors [corrected] CD28/CTLA-4 in cross-priming of CD4-dependent CTL in vivo. We find that both CD28 and B7-1/B7-2 are required for CD40-activated APC to cross-prime CTL, and that priming by CD40-activated APC was prevented by blockade of CD28. Conversely, augmenting CD28 signals with an agonistic Ab bypassed the requirement for CD4(+) T help or CD40 activation. Interestingly, blockade of the negative regulatory B7 receptor CTLA-4 failed to prime CTL in the absence of T help. These results support a model in which activation-induced up-regulation of B7 molecules on APC leads to increased CD28 signaling and a commitment to cross-priming of CD4-dependent CTL.

HLA class I polymorphism has a dual impact on ligand binding and chaperone interaction.

This article will describe coordinated analyses of how amino acid substitutions in the HLA class I antigen binding groove modify chaperone interaction and peptide ligand presentation. By parallel testing of ligand presentation and chaperone interaction with a series of natural HLA-B subtypes, this study has discovered that position 116 of the HLA-B15 class I heavy chain is pivotal in both peptide selection and control of interaction between the assembly complex and the class I heavy chain. Correlated with these qualitative differences in peptide selection and chaperone association are quantitative differences in the expression levels of the HLA molecules at the cell surface. These parallel studies, therefore, demonstrate that particular HLA class I polymorphisms can simultaneously influence ligand presentation and interaction with intracellular chaperones.

CD40L blockade prevents autoimmune diabetes by induction of bitypic NK/DC regulatory cells.

Systemic treatment with antibody to CD40 ligand (aCD40L) can prevent autoimmunity and transplant rejection in several animal models and is currently under evaluation in clinical trials. While it is known that aCD40L administration inhibits expansion and effector functions of aggressive T cells, it is still unclear whether additional regulatory mechanisms are operative. Here we demonstrate that a single episode of CD40L blockade during development of the autoaggressive immune response completely prevented autoimmune disease in the RIP-LCMV mouse model for virally induced type 1 diabetes. Interestingly, protection could be transferred by a highly potent, bitypic cell population sharing phenotypic and functional properties of both natural killer (NK) and dendritic cells (DC). Furthermore, protection of prediabetic recipients was autoantigen specific and did not result in generalized immunosuppression. The origin, function, and therapeutic potential of these bitypic NK/DC regulatory cells is discussed.