Investigational anabolic agents for the treatment of osteoporosis: an update on recent developments

Effect of weekly teriparatide injections on osteoporotic fracture healing: protocol for a double-blind, randomised controlled trial

INTRODUCTION

Both animal studies and clinical trials have shown that daily parathyroid hormone administration promotes bone fracture healing. We previously found that weekly injections of the recombinant human parathyroid hormone teriparatide at a dosage of 20 μg/kg promoted tibial fracture healing to the same extent as daily injections of teriparatide at a dosage of 10 μg/kg in a rodent model. However, the effect of weekly teriparatide administration on human fracture healing is unreported. This protocol describes a randomised controlled clinical trial designed to evaluate whether weekly administration of teriparatide accelerates fracture repair in humans.

METHODS AND ANALYSIS

This single-centre, double-blind, randomised controlled trial will be conducted in Peking University Third Hospital. Eligible patients with Colles' fracture incurred within 48 hours will be randomly divided into two groups (n=40 per group) that will receive 14 weekly subcutaneous injections of either saline or teriparatide (40 μg/week). The primary outcome will be the time taken to achieve radiographic healing, as assessed using the modified radiographic union scale for tibial fractures. The secondary outcomes will be functional assessments, including the self-administered Patient-Rated Wrist Evaluation questionnaire, grip strength and rate of fracture non-union.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the Peking University Third Hospital Medical Science Research Ethics Committee (M2020207). The findings will be disseminated in peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT04473989: protocol version: 1.

Safety of Romosozumab in Osteoporotic Men and Postmenopausal Women: A Meta-Analysis and Systematic Review

Sclerostin is a protein synthesized mainly by osteocytes whose function is to inhibit bone formation. A recent monoclonal antibody, Romosozumab, is able to block sclerostin. The aim of this meta-analysis is to compare the safety of Romosozumab with placebo and alendronate. Five randomized controlled trials that described the safety of Romosozumab in healthy men and postmenopausal women were analyzed. The measures to be compared were the number of adverse events and the number of serious adverse events. Specific results included injection site reaction, arthralgia, nasopharyngitis, and back pain. A total of 11,741 patients were included in this meta-analysis, in three different groups: Romosozumab, alendronate, and placebo. Significant differences were seen between the groups with regard to injection site reaction: 5.88% in the Romosozumab group versus 3.62% in the placebo group (Mantel-Haenszel [M-H] 1.54, confidence interval [95% CI] 1.22-1.96; p < 0.001) and 2.62% in the alendronate group (M-H 1.8, 95% CI 1.32-2.60; p < 0.001). In addition, patients treated with Romosozumab had significantly fewer total adverse events than the alendronate group (M-H 0.85, 95% CI 0.74-0.98; p < 0.05). In conclusion, Romosozumab may have lower adverse effects compared to alendronate and comparable to a placebo, except injection site reactions. Injection site reactions were more with romosozumab compared to alendronate and compared to the placebo as well. Romosozumab appears to have a similar safety profile to bisphosphonates.

[Osteoporosis-specific treatment when and how?]

Over 6 million people in Germany suffer from osteoporosis; approximately half of all women over 70 years old and approximately 1 in 5 men over 70 years old are affected. The most relevant clinical consequences of the disease are fractures leading to a clear impairment in the quality of life. Furthermore, following an osteoporotic fracture especially of the hip or vertebra there is increased mortality. Despite higher individual and socioeconomic relevance, too few patients with osteoporosis still receive adequate treatment. Based on the current guidelines of the governing body for osteology (DVO) the indications for specific medicinal treatment can be determined. Furthermore, the selection of the suitable osteoporosis medication can be carried out by considering several factors, including individual ones.

Treatment of osteoporosis: whom, how and for how long?

Identification of patients at risk for fragility fractures is the first important step in the management of osteoporosis. Bisphosphonates have been the mainstay of treatment for decades, whereas denosumab and selective oestrogen receptor modulators are other available licensed antiresorptive drugs. Currently teriparatide is the only approved anabolic agent in Europe, while abaloparatide and romosozumab are awaiting approval and might be available in the near future. For bisphosphonates, current guidance suggests an initial treatment course of 3-5 years and more prolonged treatment should be pursued in patients with higher fracture risk. For patients with lower risk, a period off treatment might be considered after this initial course to minimize the risks associated with more prolonged treatment, but this only applies to bisphosphonates and not denosumab or teriparatide. This review discusses strategies for case finding of patients at risk, currently available treatment options, recent developments in pharmacological management and duration of treatment.

Loss of Nmp4 optimizes osteogenic metabolism and secretion to enhance bone quality

A goal of osteoporosis therapy is to restore lost bone with structurally sound tissue. Mice lacking the transcription factor nuclear matrix protein 4 (Nmp4, Zfp384, Ciz, ZNF384) respond to several classes of osteoporosis drugs with enhanced bone formation compared with wild-type (WT) animals. Nmp4-/- mesenchymal stem/progenitor cells (MSPCs) exhibit an accelerated and enhanced mineralization during osteoblast differentiation. To address the mechanisms underlying this hyperanabolic phenotype, we carried out RNA-sequencing and molecular and cellular analyses of WT and Nmp4-/- MSPCs during osteogenesis to define pathways and mechanisms associated with elevated matrix production. We determined that Nmp4 has a broad impact on the transcriptome during osteogenic differentiation, contributing to the expression of over 5,000 genes. Phenotypic anchoring of transcriptional data was performed for the hypothesis-testing arm through analysis of cell metabolism, protein synthesis and secretion, and bone material properties. Mechanistic studies confirmed that Nmp4-/- MSPCs exhibited an enhanced capacity for glycolytic conversion: a key step in bone anabolism. Nmp4-/- cells showed elevated collagen translation and secretion. The expression of matrix genes that contribute to bone material-level mechanical properties was elevated in Nmp4-/- cells, an observation that was supported by biomechanical testing of bone samples from Nmp4-/- and WT mice. We conclude that loss of Nmp4 increases the magnitude of glycolysis upon the metabolic switch, which fuels the conversion of the osteoblast into a super-secretor of matrix resulting in more bone with improvements in intrinsic quality.

Role of Bisphosphonate Therapy in Patients with Osteopenia: A Systemic Review

By contrast to clinical trials exploring osteoporosis, clinical trials specifically designed for the osteopenic population are limited. Thus, less clinical data are available regarding treatment benefits and cost-effectiveness of treating a patient population with a bone mass density in the osteopenic range (T-score between -1 and -2.5). In this article, we aimed to highlight this high-risk population with a low bone mass density (BMD) susceptible to high fracture risk by reviewing different national and international guidelines for treating osteopenia. The cost-effectiveness of the therapy for the above-mentioned patient population is also discussed. By reviewing different clinical trials, we have specifically highlighted the role of bisphosphonate therapy for fracture risk reduction and increment in bone mineral density (BMD) in patients with osteopenia.

Raman spectroscopy as a predictive tool for monitoring osteoporosis therapy in a rat model of postmenopausal osteoporosis

Pharmacological therapy of osteoporosis reduces bone loss and risk of fracture in patients. Modulation of bone mineral density cannot explain all effects. Other aspects of bone quality affecting fragility and ways to monitor them need to be better understood. Keratinous tissue acts as surrogate marker for bone protein deterioration caused by oestrogen deficiency in rats. Ovariectomised rats were treated with alendronate (ALN), parathyroid hormone (PTH) or estrogen (E2). MicroCT assessed macro structural changes. Raman spectroscopy assessed biochemical changes. Micro CT confirmed that all treatments prevented ovariectomy-induced macro structural bone loss in rats. PTH induced macro structural changes unrelated to ovariectomy. Raman analysis revealed ALN and PTH partially protect against molecular level changes to bone collagen (80% protection) and mineral (50% protection) phases. E2 failed to prevent biochemical change. The treatments induced alterations unassociated with the ovariectomy; increased beta sheet with E2, globular alpha helices with PTH and fibrous alpha helices with both ALN and PTH. ALN is closest to maintaining physiological status of the animals, while PTH (comparable protective effect) induces side effects. E2 is unable to prevent molecular level changes associated with ovariectomy. Raman spectroscopy can act as predictive tool for monitoring pharmacological therapy of osteoporosis in rodents. Keratinous tissue is a useful surrogate marker for the protein related impact of these therapies.The results demonstrate utility of surrogates where a clear systemic causation connects the surrogate to the target tissue. It demonstrates the need to assess broader biomolecular impact of interventions to examine side effects.

The Bromodomain Inhibitor N-Methyl pyrrolidone Prevents Osteoporosis and BMP-Triggered Sclerostin Expression in Osteocytes

(1) Background: In an adult skeleton, bone is constantly renewed in a cycle of bone resorption, followed by bone formation. This coupling process, called bone remodeling, adjusts the quality and quantity of bone to the local needs. It is generally accepted that osteoporosis develops when bone resorption surpasses bone formation. Osteoclasts and osteoblasts, bone resorbing and bone forming cells respectively, are the major target in osteoporosis treatment. Inside bone and forming a complex network, the third and most abundant cells, the osteocytes, have long remained a mystery. Osteocytes are responsible for mechano-sensation and -transduction. Increased expression of the osteocyte-derived bone inhibitor sclerostin has been linked to estrogen deficiency-induced osteoporosis and is therefore a promising target for osteoporosis management. (2) Methods: Recently we showed in vitro and in vivo that NMP (N-Methyl-2-pyrrolidone) is a bioactive drug enhancing the BMP-2 (Bone Morphogenetic Protein 2) induced effect on bone formation while blocking bone resorption. Here we tested the effect of NMP on the expression of osteocyte-derived sclerostin. (3) Results: We found that NMP significantly decreased sclerostin mRNA and protein levels. In an animal model of osteoporosis, NMP prevented the estrogen deficiency-induced increased expression of sclerostin. (4) Conclusions: These results support the potential of NMP as a novel therapeutic compound for osteoporosis management, since it preserves bone by a direct interference with osteoblasts and osteoclasts and an indirect one via a decrease in sclerostin expression by osteocytes.

Romosozumab treatment in postmenopausal women with osteoporosis: a meta-analysis of randomized controlled trials

AIM

To conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the safety and efficacy of romosozumab in the treatment of postmenopausal osteoporosis.

METHOD

A comprehensive literature review was performed of PubMed, EMBASE, Cochrane Controlled Trials Registry, and Web of Science for RCTs. Outcome measures were changes in lumbar spine, total hip and femoral neck bone mineral density (BMD), incidence of fractures and adverse events. Six trials were finally included.

RESULTS

Romosozumab resulted in a significantly lower risk of new vertebral fracture (relative risk (RR) 0.37, 95% confidence interval (CI) 0.18-0.77, p = 0.005, n = 5371), non-vertebral fracture (RR 0.78, 95% CI 0.66-0.92, p < 0.0001, n = 5635) and hip fracture (RR 0.59, 95% CI 0.44-0.79, p = 0.0004, n = 5635) compared with other therapies. The BMD was significantly increased at the lumbar spine (weighted mean difference (WMD) 13.33, 95% CI 11.41-15.25, p < 0.00001, n = 198), total hip (WMD 5.09, 95% CI 3.81-6.38, p < 0.00001, n = 184) and femoral neck (WMD 4.70, 95% CI 3.50-5.90, p < 0.00001, n = 175) compared with placebo. There was no significant difference in the incidence of adverse events in patients with romosozumab compared to other therapies (RR 1.00, 95% CI 0.98-1.02).

CONCLUSION

In postmenopausal women with osteoporosis who were at high risk for fracture, romosozumab treatment resulted in a significantly lower risk of fracture. Romosozumab 210 mg monthly showed the largest gains in BMD, and was generally well tolerated.

Autophagy controls mesenchymal stem cell properties and senescence during bone aging

Bone marrow‐derived mesenchymal stem cells (BMMSCs) exhibit degenerative changes, including imbalanced differentiation and reduced proliferation during aging, that contribute to age‐related bone loss. We demonstrate here that autophagy is significantly reduced in aged BMMSCs compared with young BMMSCs. The autophagy inhibitor 3‐methyladenine (3‐MA) could turn young BMMSCs into a relatively aged state by reducing their osteogenic differentiation and proliferation capacity and enhancing their adipogenic differentiation capacity. Accordingly, the autophagy activator rapamycin could restore the biological properties of aged BMMSCs by increasing osteogenic differentiation and proliferation capacity and decreasing adipogenic differentiation capacity. Possible underlying mechanisms were explored, and the analysis revealed that autophagy could affect reactive oxygen species and p53 levels, thus regulating biological properties of BMMSCs. In an in vivo study, we found that activation of autophagy restored bone loss in aged mice. In conclusion, our results suggest that autophagy plays a pivotal role in the aging of BMMSCs, and activation of autophagy could partially reverse this aging and may represent a potential therapeutic avenue to clinically treat age‐related bone loss.