Project description:Osteoporosis is characterized by reduced bone mass and disruption of bone architecture, resulting in increased risk of fragility fractures and significant long-term disability. Although both anti-resorptive treatments and osteoanabolic drugs, such as parathyroid hormone analogues, are effective in fracture prevention, limitations exist due to lack of compliance or contraindications to these drugs. Thus, there is a need for novel potent therapies, especially for patients at high fracture risk. Romosozumab is a monoclonal antibody against sclerostin with a dual mode of action. It enhances bone formation and simultaneously suppresses bone resorption, resulting in a large anabolic window. In this opinion-based narrative review, we highlight the role of sclerostin as a critical regulator of bone mass and present human diseases of sclerostin deficiency as well as preclinical models of genetically modified sclerostin expression, which led to the development of anti-sclerostin antibodies. We review clinical studies of romosozumab in terms of bone mass accrual and anti-fracture activity in the setting of postmenopausal and male osteoporosis, present sequential treatment regimens, and discuss its safety profile and possible limitations in its use. Moreover, an outlook comprising future translational applications of anti-sclerostin antibodies in diseases other than osteoporosis is given, highlighting the clinical significance and future scopes of Wnt signaling in these settings.
Project description:Sclerostin is an osteocyte-derived glycoprotein that inhibits Wnt/β-catenin signaling and activation of osteoblast function, thereby inhibiting bone formation. It plays a vital role in the regulation of skeletal growth. In adults, sclerostin secretion is modulated by skeletal loading (increased secretion with immobilization; less with weight bearing) and by hormonal/cytokine actions on the osteocyte. Sclerostin deficiency syndromes in humans and animals are characterized by high bone mass of normal quality. In animal models of osteoporosis, inhibition of sclerostin by monoclonal antibodies induces osteoblast activity and new bone formation, normalizing bone mass and improving bone architecture and strength. In recently completed clinical trials, anti-sclerostin antibody therapy results in marked increases in bone mineral density and rapid and substantial reduction in fracture risk. This review will focus on these recent studies and anticipate the role of anti-sclerostin therapy in the management of patients with osteoporosis.
Project description:Osteoporosis and osteoporosis-related fractures are growing problems with the aging population and are associated with significant morbidity and mortality. At this time, other than parathyroid hormone analogs, all therapies for osteoporosis are antiresorptive. Therefore, researchers have focused efforts on development of more anabolic therapies. Understanding of the Wnt signaling pathway, which is critical for skeletal development, and the role of sclerostin in inhibition of Wnt signaling has led to the discovery of a novel therapeutic approach in the treatment of osteoporosis - sclerostin inhibition. In this review, we discuss the biology of Wnt signaling and sclerostin inhibition. We then discuss human disorders of decreased sclerostin function and animal models of sclerostin inhibition. Both have served to elucidate the effects of decreased sclerostin levels and function - increased bone mass and strength and fewer fractures. In addition, we review data from Phase I and II studies of the two humanized sclerostin monoclonal antibodies, romosozumab and blosozumab, both of which have had positive effects on bone mineral density. We conclude with a discussion of the ongoing Phase III studies of romosozumab. The available data support the potential for neutralizing sclerostin monoclonal antibodies to serve as anabolic agents in the treatment of osteoporosis.
Project description:It is estimated that over 200 million adults worldwide have osteoporosis, a disease that has increasing socioeconomic impact reflected by unsustainable costs associated with disability, fracture management, hospital stays, and treatment. Existing therapeutic treatments for osteoporosis are associated with a variety of issues relating to use, clinical predictability, and health risks. Consequently, additional novel therapeutic targets are increasingly sought. A promising therapeutic candidate is sclerostin, a Wnt pathway antagonist and, as such, a negative regulator of bone formation. Sclerostin antibody treatment has demonstrated efficacy and superiority compared to other anabolic treatments for increasing bone formation in both preclinical and clinical settings. Accordingly, it has been suggested that sclerostin antibody treatment is set to achieve market approval by 2017 and aggressively compete as the gold standard for osteoporotic treatment by 2021. In anticipation of phase III trial results which may potentially signify a significant step in achieving market approval here, we review the preclinical and clinical emergence of sclerostin antibody therapies for both osteoporosis and alternative applications. Potential clinical challenges are also explored as well as ongoing developments that may impact on the eventual clinical application of sclerostin antibodies as an effective treatment of osteoporosis.
Project description:UnlabelledThis study was to determine if antibody against sclerostin (Scl-Ab) could prevent glucocorticoid (GC)-induced osteoporosis in mice. We found that Scl-Ab prevented GC-induced reduction in bone mass and bone strength and that the anabolic effects of Scl-Ab might be partially achieved through the preservation of osteoblast activity through autophagy.IntroductionGlucocorticoids (GCs) inhibit bone formation by altering osteoblast and osteocyte cell activity and lifespan. A monoclonal antibody against sclerostin, Scl-Ab, increased bone mass in both preclinical animal and clinical studies in subjects with low bone mass. The objectives of this study were to determine if treatment with the Scl-Ab could prevent loss of bone mass and strength in a mouse model of GC excess and to elucidate if Scl-Ab modulated bone cell activity through autophagy.MethodsWe generated reporter mice that globally expressed dsRed fused to LC3, a protein marker for autophagosomes, and evaluated the dose-dependent effects of GCs (0, 0.8, 2.8, and 4 mg/kg/day) and Scl-Ab on autophagic osteoblasts, bone mass, and bone strength.ResultsGC treatment at 2.8 and 4 mg/kg/day of methylprednisolone significantly lowered trabecular bone volume (Tb-BV/TV) at the lumbar vertebrae and distal femurs, cortical bone mass at the mid-shaft femur (FS), and cortical bone strength compared to placebo (PL). In mice treated with GC and Scl-Ab, Tb-BV/TV increased by 60-125 %, apparent bone strength of the lumbar vertebrae by 30-70 %, FS-BV by 10-18 %, and FS-apparent strength by 13-15 %, as compared to GC vehicle-treated mice. GC treatment at 4 mg/kg/day reduced the number of autophagic osteoblasts by 70 % on the vertebral trabecular bone surface compared to the placebo group (PL, GC 0 mg), and GC + Scl-Ab treatment.ConclusionsTreatment with Scl-Ab prevented GC-induced reduction in both trabecular and cortical bone mass and strength and appeared to maintain osteoblast activity through autophagy.
Project description:Sclerosteosis is a rare high bone mass disease that is caused by inactivating mutations in the SOST gene. Its gene product, Sclerostin, is a key negative regulator of bone formation and might therefore serve as a target for the anabolic treatment of osteoporosis. The exact molecular mechanism by which Sclerostin exerts its antagonistic effects on Wnt signaling in bone forming osteoblasts remains unclear. Here we show that Wnt3a-induced transcriptional responses and induction of alkaline phosphatase activity, an early marker of osteoblast differentiation, require the Wnt co-receptors LRP5 and LRP6. Unlike Dickkopf1 (DKK1), Sclerostin does not inhibit Wnt-3a-induced phosphorylation of LRP5 at serine 1503 or LRP6 at serine 1490. Affinity labeling of cell surface proteins with [(125)I]Sclerostin identified LRP6 as the main specific Sclerostin receptor in multiple mesenchymal cell lines. When cells were challenged with Sclerostin fused to recombinant green fluorescent protein (GFP) this was internalized, likely via a Clathrin-dependent process, and subsequently degraded in a temperature and proteasome-dependent manner. Ectopic expression of LRP6 greatly enhanced binding and cellular uptake of Sclerostin-GFP, which was reduced by the addition of an excess of non-GFP-fused Sclerostin. Finally, an anti-Sclerostin antibody inhibited the internalization of Sclerostin-GFP and binding of Sclerostin to LRP6. Moreover, this antibody attenuated the antagonistic activity of Sclerostin on canonical Wnt-induced responses.
Project description:UnlabelledAnti-osteoporosis medication (AOM) use in patients exposed to glucocorticoids is thought to reduce fractures. We found post-menopausal women using glucocorticoids for at least 90 days who also used an AOM within 90 days had 48 % fewer fractures by 1 year and 32 % fewer fractures by 3 years compared to non-AOM users.IntroductionThe purpose of this study is to explore the effectiveness of adherence to quality measures by estimating the effect of anti-osteoporosis medication (AOM) initiation within 90 days after chronic (≥90 days) glucocorticoid (GC) therapy on osteoporotic fracture.MethodsA new-user cohort was assembled using the MarketScan databases between 2000 and 2012. Included patients were female, age ≥50 at GC initiation, had a first GC fill daily dose ≥10 mg and persisted for at least 90 days. During a 365-day baseline period, patients were excluded for prior GC or AOM (bisphosphonate, denosumab, teriparatide) use, fracture, or cancer diagnosis. Initiators of an AOM in the 14 days pre- or 90 days post-GC fill were characterized as AOM users; those without, AOM non-users. Follow-up began 91 days after GC fill with patients followed until fracture, loss of continuous enrollment, initiation of AOM by AOM non-users, or end of study period. A propensity score was estimated for AOM receipt using all measured covariates and converted to a stabilized inverse probability of treatment weights (IPTW). Weighted hazard ratios (HR) and associated 95% confidence intervals (95% CI) were estimated using weighted Cox proportional hazard models.ResultsOf the 7885 women eligible for the study, 12.1% were AOM users. AOM use was associated with lower fracture incidence: weighted HR of 0.52 (95% CI 0.29, 0.94) at 1 year and weighted HR of 0.68 (95% CI 0.47, 0.99) at 3 years.ConclusionsAOM initiation within 90 days of chronic GC use was associated with a fracture reduction of 48% at 1 year and 32% at 3 years.
Project description:We developed and characterized monoclonal antibodies directed against the amino-terminal and carboxy-terminal regions of human and mouse sclerostin (scl). Amino-terminal and carboxy-terminal scl peptides with limited homology to scl domain-containing protein-1 were synthesized using f-moc chemistry. The peptides were conjugated to keyhole limpet hemocyanin and the conjugates were used for immunization of mice. Monoclonal antibodies were obtained and characterized using bacterially expressed and insect cell-expressed recombinant scl. The amino-terminal (IgG 2aK) and carboxy-terminal (IgG 2bK) antibodies bound bioactive sclerostin that was expressed in an insect-cell expression system with dissociation constants in the nanomolar range. The antibodies are potentially useful agents that can be used for modulating sclerostin bioactivity.
Project description:Tumor necrosis factor-? (TNF-?), a proinflammatory cytokine, plays a key role in the pathogenesis of many inflammatory diseases, including arthritis. Neutralization of this cytokine by anti-TNF-? antibodies has shown its efficacy in rheumatoid arthritis (RA) and is now widely used. Nevertheless, some patients currently treated with anti-TNF-? remain refractory or become nonresponder to these treatments. In this context, there is a need for new or complementary therapeutic strategies. In this study, we investigated in vitro and in vivo anti-inflammatory potentialities of an anti-TNF-? triplex-forming oligonucleotide (TFO), as judged from effects on two rat arthritis models. The inhibitory activity of this TFO on articular cells (synoviocytes and chondrocytes) was verified and compared to that of small interfering RNA (siRNA) in vitro. The use of the anti-TNF-? TFO as a preventive and local treatment in both acute and chronic arthritis models significantly reduced disease development. Furthermore, the TFO efficiently blocked synovitis and cartilage and bone destruction in the joints. The results presented here provide the first evidence that gene targeting by anti-TNF-? TFO modulates arthritis in vivo, thus providing proof-of-concept that it could be used as therapeutic tool for TNF-?-dependent inflammatory disorders.