Uwe Junker

Proton-sensing G-protein-coupled receptors

Blood pH is maintained in a narrow range around pH 7.4 mainly through regulation of respiration and renal acid extrusion. The molecular mechanisms involved in pH homeostasis are not completely understood. Here we show that ovarian cancer G-protein-coupled receptor 1 (OGR1), previously described as a receptor for sphingosylphosphorylcholine, acts as a proton-sensing receptor stimulating inositol phosphate formation. The receptor is inactive at pH 7.8, and fully activated at pH 6.8—site-directed mutagenesis shows that histidines at the extracellular surface are involved in pH sensing. We find that GPR4, a close relative of OGR1, also responds to pH changes, but elicits cyclic AMP formation. It is known that the skeleton participates in pH homeostasis as a buffering organ, and that osteoblasts respond to pH changes in the physiological range, but the pH-sensing mechanism operating in these cells was hitherto not known. We detect expression of OGR1 in osteosarcoma cells and primary human osteoblast precursors, and show that these cells exhibit strong pH-dependent inositol phosphate formation. Immunohistochemistry on rat tissue sections confirms the presence of OGR1 in osteoblasts and osteocytes. We propose that OGR1 and GPR4 are proton-sensing receptors involved in pH homeostasis.

Retroviral vectors designed for targeted expression of RNA polymerase III-driven transcripts: a comparative study.

Retroviral gene delivery systems for RNA polymerase II (RNA pol II)-based promoters have been developed and are widely used in gene transfer studies. In contrast, gene delivery systems with RNA pol III-based expression cassettes have not been studied comprehensively, although therapeutic applications (e.g., ribozymes, antisense, triplex RNA and RNA decoys) have been proposed. In this report, we describe retroviral vectors designed to optimize expression of short chimeric RNAs transcribed from a number of RNA pol III promoters. Our results show that all analysed RNA pol III expression cassettes (tRNA, U6, Ad VA1), regardless of orientation, do not transcribe efficiently when located between the retroviral long terminal repeats (LTRs). In contrast, high steady-state expression levels can be achieved by inserting the RNA pol III expression cassette into the U3 region of the LTR (double-copy design). Compared to human tRNA gene promoters (tRNA(Met), tRNA(Val)), the human small nuclear RNA U6 gene (U6) and the adenovirus virus-associated RNA 1 (Ad VA1) gene promoters yielded higher expression levels. The majority of the chimeric U6-derived transcripts were detected in the nuclear RNA fraction, and the VA1 and tRNA-driven transcripts were predominantly detected in the cytoplasmic compartments. This report is the first comparative study of RNA pol III-driven promoters expressing short chimeric transcripts leading to an optimized retroviral-vector design.

Comparison of Drug and Cell-Based Delivery: Engineered Adult Mesenchymal Stem Cells Expressing Soluble Tumor Necrosis Factor Receptor II Prevent Arthritis in Mouse and Rat Animal Models

Rheumatoid arthritis (RA) is a systemic autoimmune disease with unknown etiology where tumor necrosis factor‐α (TNFα) plays a critical role. Etanercept, a recombinant fusion protein of human soluble tumor necrosis factor receptor II (hsTNFR) linked to the Fc portion of human IgG1, is used to treat RA based on the rationale that sTNFR binds TNFα and blocks TNFα‐mediated inflammation. We compared hsTNFR protein delivery from genetically engineered human mesenchymal stem cells (hMSCs) with etanercept. Blocking TNFα‐dependent intercellular adhesion molecule‐1 expression on transduced hMSCs and inhibition of nitric oxide production from TNFα‐treated bovine chondrocytes by conditioned culture media from transduced hMSCs demonstrated the functionality of the hsTNFR construction. Implanted hsTNFR‐transduced mesenchymal stem cells (MSCs) reduced mouse serum circulating TNFα generated from either implanted TNFα‐expressing cells or lipopolysaccharide induction more effectively than etanercept (TNFα, 100%; interleukin [IL]‐1α, 90%; and IL‐6, 60% within 6 hours), suggesting faster clearance of the soluble tumor necrosis factor receptor (sTNFR)‐TNFα complex from the animals. In vivo efficacy of sTNFR‐transduced MSCs was illustrated in two (immune‐deficient and immune‐competent) arthritic rodent models. In the antibody‐induced arthritis BalbC/SCID mouse model, intramuscular injection of hsTNFR‐transduced hMSCs reduced joint inflammation by 90% compared with untransduced hMSCs; in the collagen‐induced arthritis Fischer rat model, both sTNFR‐transduced rat MSCs and etanercept inhibited joint inflammation by 30%. In vitro chondrogenesis assays showed the ability of TNFα and IL1α, but not interferon γ, to inhibit hMSC differentiation to chondrocytes, illustrating an additional negative role for inflammatory cytokines in joint repair. The data support the utility of hMSCs as therapeutic gene delivery vehicles and their potential to be used in alleviating inflammation within the arthritic joint.

BPS804 Anti‐sclerostin Antibody in Adults with Moderate Osteogenesis Imperfecta: Results of a Randomized Phase 2a Trial

This 21‐week, open‐label, phase 2a trial aimed to evaluate the pharmacodynamics and safety of multiple, escalating infusions of BPS804, a neutralizing, anti‐sclerostin antibody, in adults with moderate osteogenesis imperfecta (OI). Patients received BPS804 (three escalating doses each separated by 2 weeks [5, 10, and 20 mg/kg]) or no treatment (reference group). The primary efficacy endpoints were mean changes from baseline to day 43 in: procollagen type 1 N‐terminal propeptide (P1NP), procollagen type 1 C‐terminal propeptide (P1CP), bone‐specific alkaline phosphatase (BSAP), osteocalcin (OC), and type 1 collagen cross‐linked C‐telopeptide (CTX‐1). Mean change from baseline to day 141 in lumbar spine areal bone mineral density (aBMD) was also assessed. BPS804 safety and tolerability were assessed every 2 weeks. Overall, 14 adults were enrolled (BPS804 group: n = 9, mean age 30.7 years, mean aBMD Z‐score –2.6; reference group, n = 5, mean age 27.4 years, mean aBMD Z‐score –2.2). In the BPS804 group, P1NP, P1CP, BSAP, and OC were increased by 84% (p < 0.001), 53% (p = 0.003), 59% (p < 0.001), and 44% (p = 0.012), respectively, versus baseline (reference: P1NP, +6% [p = 0.651]; P1CP, +5% [p = 0.600]; BSAP, –13% [p = 0.582]; OC, –19% [p = 0.436]). BPS804 treatment downregulated CTX‐1 by 44% from baseline (reference: –7%; significance was not tested for this biomarker), and increased aBMD by 4% (p = 0.038; reference group: +1%; p = 0.138). BPS804 was generally well tolerated. There were 32 adverse events reported in nine patients; none was suspected to be treatment‐related. There were no treatment‐related fractures. BPS804 stimulates bone formation, reduces bone resorption, and increases lumbar spine aBMD in adults with moderate OI. This paves the way for a longer‐term, phase 3 trial into the efficacy, safety, and tolerability of BPS804 in patients with OI.

Gene therapy for arthritis 1996 - 1999

Gene therapy for rheumatoid arthritis (RA) is a relatively novel therapeutic concept. At present, two clinical trials are ongoing which evaluate the safety of ex vivo gene transfer into synoviocytes. However, it is anticipated that the number of clinical trials evaluating anti-inflammatory gene transfer strategies will increase significantly within the near future. This review summarises the pertinent patent situation for arthritis gene therapy from 1996 to 1999. A patent search with the keywords arthritis and gene therapy revealed 65 patent filings during this time period. In this report, we describe and discuss a selection of patent applications filed for novel therapeutic strategies, enabling gene delivery, and expression systems into relevant cell populations (e.g., synoviocytes, chondrocytes and mesenchymal stem cells). For the future, we envision that gene discovery efforts in connection with functional genomics will provide a wealth of novel patentable information hopefully leading to innovative ge...

Efficacy of anti-sclerostin monoclonal antibody BPS804 in adult patients with hypophosphatasia

BACKGROUND. Hypophosphatasia (HPP) is a rare genetic disorder resulting in variable alterations of bone formation and mineralization that are caused by mutations in the ALPL gene, encoding the tissue-nonspecific alkaline phosphatase (ALP) enzyme. METHODS. In this phase IIA open-label, single-center, intra-patient, dose-escalating study, adult patients with HPP received 3 ascending intravenous doses of 5, 10, and 20 mg/kg BPS804, a fully human anti-sclerostin monoclonal antibody, on days 1, 15, and 29, respectively. Patients were followed for 16 weeks after the last dose. We assessed the pharmacodynamics, pharmacokinetics, preliminary efficacy, and safety of BPS804 administrations at specified intervals during treatment and follow-up. RESULTS. Eight patients (mean age 47.8 years) were enrolled in the study (6 females, 2 males). BPS804 treatment increased mean ALP and bone-specific ALP enzymatic activity between days 2 and 29. Transient increases in the bone formation markers procollagen type-I N-terminal propeptide (PINP), osteocalcin, and parathyroid hormone as well as a transient decrease in the bone resorption marker C-telopeptide of type I collagen (CTX-1) were observed. Lumbar spine bone mineral density showed a mean increase by day 85 and at end of study. Treatment-associated adverse events were mild and transient. CONCLUSION. BPS804 treatment was well tolerated and resulted in increases in bone formation biomarkers and bone mineral density, suggesting that sclerostin inhibition could be applied to enhance bone mineral density, stability, and regeneration in non-life-threatening clinical situations in adults with HPP. TRIAL REGISTRATION. Clinicaltrials.gov NCT01406977. FUNDING. Novartis Institutes for BioMedical Research, Basel, Switzerland.