Tanezumab for the treatment of pain from osteoarthritis of the knee

LncRNA CASC2 is up-regulated in osteoarthritis and participates in the regulation of IL-17 expression and chondrocyte proliferation and apoptosis

Long non-coding RNAs (lncRNA) CASC2 is a key player in cancer biology. Our new findings showed that both lncRNA CASC2 and IL-17 were up-regulated in plasma of osteoarthritis patients. Plasma levels of lncRNA CASC2 and IL-17 were significantly and positive correlated only in osteoarthritis patients. Overexpression of lncRNA CASC2 led to up-regulated expression of IL-17 in cells of human chondrocyte cell line CHON-001 (ATCC^® CRL-2846™). In addition, overexpression of lncRNA CASC2 inhibited the proliferation, and promoted the apoptosis of chondrocyte. Therefore, lncRNA CASC2 is up-regulated in osteoarthritis and participates in the regulation of IL-17 expression and chondrocyte proliferation and apoptosis.

Novel Approaches to Persistent Pain Therapy

Persistent and neuropathic pain affects >15% of the global population. Apart from being an individual burden to the patient, persistent pain causes considerable subsequent costs in global healthcare systems. Despite the efforts of pharmaceutical companies to develop novel analgesics, pharmacological options for the therapy of persistent and/or neuropathic pain are limited. We discuss here novel approaches to persistent pain therapy that are independent of classical target-based drug discovery, focusing on individualized diagnostic technologies, improvement of existing therapies, and expansion of current pharmacological treatments and future techniques that may broaden pharmacological options for the individual treatment of persistent pain in patients.

Transforming growth factor-β stimulates nerve growth factor production in osteoarthritic synovium

Background

Nerve growth factor (NGF) contributes to pain in knee osteoarthritis (KOA) patients. Transforming growth factor-beta (TGF-β) stimulates NGF expression in chondrocytes from KOA patients. However, the correlation between synovial TGF-β and NGF levels has not been sufficiently studied in human KOA patients. Further, the mechanism governing NGF regulation by TGF-β in synovial cells is unclear.

Methods

During total knee arthroplasty, we extracted the synovial tissue (SYT) of 107 subjects with unilateral Kellgren/Lawrence grade 3–4 KOA confirmed by radiography. We examined the distribution of TGF-β and NGF using immunohistochemistry, and analyzed the relationship between NGF and TGFB mRNA levels. Cultured synovial cells extracted from SYT were exposed to culture medium (control), human recombinant TGF-β (rhTGF-β), rhTGF-β + ALK5 inhibitor SB505124, rhTGF-β + transforming growth factor activating kinase 1 (TAK1) inhibitor (5Z)-7-oxozeaenol, or rhTGF-β + p38 inhibitor SB203580 for 30 min, 6 h and 24 h. NGF mRNA expressed by the cultured cells and NGF protein levels in the cell supernatant were detected by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Phosphorylation of p38 was evaluated by western blotting.

Results

NGF mRNA levels were positively correlated with those of TGFB. Cells expressing TGF-β and NGF protein were observed in the lining layer of SYT. TGF-β stimulated increased NGF mRNA expression and NGF protein production. The ALK5 inhibitor completely suppressed the TGF-β-mediated increase in NGF expression and NGF production in synovial cells. ALK5, TAK1 and p38 inhibitors inhibited the TGF-β-induced phosphorylation of p38, and TAK1 and p38 inhibitors partially inhibited the TGF-β-mediated increase in NGF expression and NGF production in synovial cells.

Conclusion

TGF-β regulates NGF production via the TGF-β/ALK5 signaling pathway in osteoarthritic synovium. This effect may partially occur through inhibition of the TAK1/p38 pathway in the SYT of KOA patients.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2595-z) contains supplementary material, which is available to authorized users.

Pharmacology of nerve growth factor and discovery of tanezumab, an anti-nerve growth factor antibody and pain therapeutic

The pharmacology of Nerve Growth Factor (NGF) and the discovery and development of tanezumab, a monoclonal anti-NGF antibody for the treatment of pain illustrate the complex and unpredictable nature of modern drug development. Initial efforts attempted to use NGF agonistically for Alzheimer's disease and neuropathies. Most unexpectedly, clinical studies unmasked hyperalgesic effects. These observations together with new data emerging from molecular and animal model studies stimulated the idea of using an NGF antagonist for chronic pain. These events also reflect the advances of neuropharmacology from classical small molecule efforts directed at neurotransmitter receptors to modern biotechnology with significant integration in molecular biology, biochemistry, and protein engineering.

Pooled analysis of tanezumab efficacy and safety with subgroup analyses of phase III clinical trials in patients with osteoarthritis pain of the knee or hip

Purpose

A pooled analysis was conducted to evaluate tanezumab efficacy and safety in patients with osteoarthritis (OA), including subgroup analyses of at-risk patients with diabetes, severe OA symptoms, and those aged ≥65 years.

Patients and methods

Data from phase III placebo-controlled clinical trials of patients with moderate-to-severe OA of the knee or hip were pooled to evaluate tanezumab efficacy (four trials) and safety (nine trials). Patients received intravenous tanezumab, tanezumab plus an oral NSAID (naproxen, celecoxib, or diclofenac), active comparator (naproxen, celecoxib, diclofenac, or oxycodone), or placebo. Efficacy assessments included change from baseline to week 16 in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and physical function scores, Patient’s Global Assessment (PGA) of OA, and percentage of patients with ≥30%, ≥50%, ≥70%, and ≥90% improvement in WOMAC pain. Safety assessments included adverse event (AE) documentation and physical and neurologic examinations.

Results

Tanezumab significantly improved all efficacy end points in the overall population. Efficacy in at-risk patient subgroups was similar to the overall population. Incidence of AEs was highest in the tanezumab plus NSAID group and lowest in the placebo group. Incidence of AEs in the tanezumab monotherapy and active comparator groups was similar. Overall incidence of AEs was similar across subgroups. AEs of abnormal peripheral sensation were more frequently reported in tanezumab-treated patients compared with placebo or active comparator. Patients receiving active comparator had a slightly higher incidence of AEs suggestive of postganglionic sympathetic dysfunction.

Conclusion

Tanezumab consistently provided significant improvement of pain, physical function, and PGA in individuals with OA, including patients with diabetes, severe OA symptoms, or aged ≥65 years. No increased safety risk was observed in at-risk patient subgroups.

Trial registration

NCT00733902, NCT00744471, NCT00830063, NCT00863304, NCT00809354, NCT00864097, NCT00863772, NCT01089725, NCT00985621.

Active immunisation targeting nerve growth factor attenuates chronic pain behaviour in murine osteoarthritis

OBJECTIVES

Nerve growth factor (NGF) has emerged as a key driver of pain in osteoarthritis (OA) and antibodies to NGF are potent analgesics in human disease. Here, we validate a novel vaccine strategy to generate anti-NGF antibodies for reversal of pain behaviour in a surgical model of OA.

METHODS

Virus-like particles were derived from the cucumber mosaic virus (CuMV) and coupled to expressed recombinant NGF to create the vaccine. 10-week-old male mice underwent partial meniscectomy to induce OA or sham-surgery. Spontaneous pain behaviour was measured by Linton incapacitance and OA severity was quantified using OARSI histological scoring. Mice (experimental and a sentinel cohort) were inoculated with CuMVtt^NGF (Vax) or CuMVtt^ctrl (Mock) either before surgery or once pain was established. Efficacy of anti-NGF from the plasma of sentinel vaccinated mice was measured in vitro using a neurite outgrowth assay in PC12 cells.

RESULTS

Anti-NGF titres were readily detectable in the vaccinated but not mock vaccinated mice. Regular boosting with fresh vaccine was required to maintain anti-NGF titres as measured in the sentinel cohort. Both prophylactic and therapeutic vaccination demonstrated a reversal of pain behaviour by incapacitance testing, and a meta-analysis of the two studies showing analgesia at peak anti-NGF titres was highly statistically significant. Serum anti-NGF was able to inhibit neurite outgrowth equivalent to around 150 ug/mL of recombinant monoclonal antibody.

CONCLUSIONS

This study demonstrates therapeutic efficacy of a novel NGF vaccine strategy that reversibly alleviates spontaneous pain behaviour in surgically induced murine OA.

Exploration of CRISPR/Cas9-based gene editing as therapy for osteoarthritis

OBJECTIVES

Osteoarthritis (OA) is a painful and debilitating disease and it is associated with aberrant upregulation of multiple factors, including matrix metalloproteinase 13 (MMP13), interleukin-1β (IL-1β) and nerve growth factor (NGF). In this study, we aimed to use the CRISPR/Cas9 technology, a highly efficient gene-editing tool, to study whether the ablation of OA-associated genes has OA-modifying effects.

METHODS

We performed intra-articular injection of adeno-associated virus, which expressed CRISPR/Cas9 components to target each of the genes encoding MMP13, IL-1β and NGF, in a surgically induced OA mouse model. We also tested triple ablations of NGF, MMP13 and IL-1β.

RESULTS

Loss-of-function of NGF palliates pain but worsens joint damage in the surgically induced OA model. Ablation of MMP13 or IL-1β reduces the expression of cartilage-degrading enzymes and attenuates structural deterioration. Targeting both MMP13 and IL-1β significantly mitigates the adverse effects of NGF blockade on the joints.

CONCLUSIONS

CRISPR-mediated ablation of NGF alleviates OA pain, and deletion of MMP13-1β or IL-1β attenuates structural damage in a post-traumatic OA model. Multiplex ablations of NGF, MMP13 and IL-1β provide benefits on both pain management and joint structure maintenance. Our results suggest that CRISPR-based gene editing is useful for the identification of promising drug targets and the development of feasible therapeutic strategies for OA treatment.

NGF increases FGF2 expression and promotes endothelial cell migration and tube formation through PI3K/Akt and ERK/MAPK pathways in human chondrocytes

OBJECTIVE

Vascular invasion is observed at the osteochondral junction in osteoarthritis (OA). Nerve growth factor (NGF) as an angiogenic factor is expressed in OA. This study is to investigate the effects of NGF on angiogenesis in vitro in human chondrocytes.

DESIGN

Articular cartilages of knee joints were harvested from healthy and OA patients. Expressions of NGF and tropomyosin-related kinase A (TrkA) were detected by western blot, Safranin-O and fast green staining and immunohistochemistry in cartilage. Expression of fibroblast growth factor 2 (FGF2) was detected by western blot in cultured chondrocytes. Chondrocytes were transfected by lentiviral vectors to knock down TrkA. Migration and tube formation of human microvascular endothelial cell (HMVEC) were assessed by using transwell co-culture with chondrocyte after treatment of NGF.

RESULTS

We confirmed expressions of NGF and TrkA were significantly up-regulated in OA. NGF induced expression of FGF2 in a time- and dose-dependent manner. Angiogenic activities of endothelial cells were greatly enhanced after co-cultured with NGF pre-treated chondrocytes, while knock-down of TrkA significantly abolished the above effects. We further found that NGF-induced expression of FGF2 promoted angiogenic activities of endothelial cells through PI3K/Akt and ERK/MAPK signaling pathways.

CONCLUSIONS

NGF promotes expression of FGF2 in vitro via PI3K/Akt and ERK/MAPK signaling pathways in human chondrocytes and it increases angiogenesis, which is mediated by TrkA. NGF could be responsible for vascular up-growth from subchondral bone in OA.

Potential biomarkers for persistent and neuropathic pain therapy

Persistent, in particular neuropathic pain affects millions of people worldwide. However, the response rate of patients to existing analgesic drugs is less than 50%. There are several possibilities to increase this response rate, such as optimization of the pharmacokinetic and pharmacodynamic properties of analgesics. Another promising approach is to use prognostic biomarkers in patients to determine the optimal pharmacological therapy for each individual. Here, we discuss recent efforts to identify plasma and CSF biomarkers, as well as genetic biomarkers and sensory testing, and how these readouts could be exploited for the prediction of a suitable pharmacological treatment. Collectively, the information on single biomarkers may be stored in knowledge bases and processed by machine-learning and related artificial intelligence techniques, resulting in the optimal pharmacological treatment for individual pain patients. We highlight the potential for biomarker-based individualized pain therapies and discuss biomarker reliability and their utility in clinical practice, as well as limitations of this approach.

Subchondral bone osteoclasts induce sensory innervation and osteoarthritis pain

Joint pain is the defining symptom of osteoarthritis (OA) but its origin and mechanisms remain unclear. Here, we investigated an unprecedented role of osteoclast-initiated subchondral bone remodeling in sensory innervation for OA pain. We show that osteoclasts secrete netrin-1 to induce sensory nerve axonal growth in subchondral bone. Reduction of osteoclast formation by knockout of receptor activator of nuclear factor kappa-B ligand (Rankl) in osteocytes inhibited the growth of sensory nerves into subchondral bone, dorsal root ganglion neuron hyperexcitability, and behavioral measures of pain hypersensitivity in OA mice. Moreover, we demonstrated a possible role for netrin-1 secreted by osteoclasts during aberrant subchondral bone remodeling in inducing sensory innervation and OA pain through its receptor DCC (deleted in colorectal cancer). Importantly, knockout of Netrin1 in tartrate-resistant acid phosphatase-positive (TRAP-positive) osteoclasts or knockdown of Dcc reduces OA pain behavior. In particular, inhibition of osteoclast activity by alendronate modifies aberrant subchondral bone remodeling and reduces innervation and pain behavior at the early stage of OA. These results suggest that intervention of the axonal guidance molecules (e.g., netrin-1) derived from aberrant subchondral bone remodeling may have therapeutic potential for OA pain.

Follistatin-like protein 1 (FSTL1) promotes chondrocyte expression of matrix metalloproteinase and inflammatory factors via the NF-κB pathway

Background

The expression of follistatin‐like protein 1 (FSTL1) is closely associated with diseases of the musculoskeletal system. However, despite being a well characterized inflammatory mediator, the effects of FSTL1 on chondrocytes are not completely understood. In this study, we investigated the effects of FSTL1 on the expression of inflammatory and catabolic factors in rat chondrocytes.

Methods

Rat chondrocytes were treated directly with various concentrations of FSTL1 in vitro. The levels of matrix metalloproteinases (MMPs), inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)‐2, interleukin (IL)‐1β, tumour necrosis factor (TNF)‐α and IL‐6 were measured by polymerase chain reaction, ELISA and Western blotting. In addition, activation of the nuclear factor kappa B (NF‐κB) pathway was explored to identify potential regulatory mechanisms.

Results

Follistatin‐like protein 1 directly increased the expression of MMP‐1, MMP‐13, iNOS, COX‐2, IL‐1β, TNF‐α and IL‐6 at both gene and protein level in a dose‐dependent manner. Activation of NF‐ κB and phosphorylation of p65 were also promoted by FSTL1 stimulation.

Conclusions

Follistatin‐like protein 1 exerts pro‐inflammatory and catabolic effects on cultured chondrocytes via activation of the NF‐κB signalling pathway. FSTL1 may therefore be a target in the treatment of OA.

Emerging Trend in the Pharmacotherapy of Osteoarthritis

Osteoarthritis (OA) is a degenerative joint disorder and one of the most prevalent diseases among the elderly population. Due to the limited spontaneous healing capacity of articular cartilage, it still remains challenging to find satisfactory treatment for OA. This review covers the emerging trends of pharmacologic therapies for OA such as traditional OA drugs (acetaminophen, non-steroidal anti-inflammatory drugs (NSAIDs), opioids, serotonin-norepinephrine reuptake inhibitors (SNRIs), intra-articular injections of corticosteroids, and dietary supplements), which are effective in pain relief but not in reversing damage, and are frequently associated with adverse events. Alternatively, disease-modifying drugs provide promising alternatives for the management of OA. The development of these emerging OA therapeutic agents requires a comprehensive understanding of the pathophysiology of OA progression. The process of cartilage anabolism/catabolism, subchondral bone remodeling and synovial inflammation are identified as potential targets. These emerging OA drugs such as bone morphogenetic protein-7 (BMP-7), fibroblast growth factor-18 (FGF-18), human serum albumin (HSA), interleukin-1 (IL-1) inhibitor, β-Nerve growth factor (β-NGF) antibody, matrix extracellular phosphoglycoprotein (MEPE) and inverse agonist of retinoic acid-related orphan receptor alpha (RORα) etc. have shown potential to modify progression of OA with minimal adverse effects. However, large-scale randomized controlled trials (RCTs) are needed to investigate the safety and efficacy before translation from bench to bedside.

CGRP and Painful Pathologies Other than Headache

CGRP has long been suspected as a mediator of arthritis pain, although evidence that CGRP directly mediates human musculoskeletal pain remains circumstantial. This chapter describes in depth the evidence surrounding CGRP's association with pain in musculoskeletal disorders and also summarises evidence for CGRP being a direct cause of pain in other conditions. CGRP-immunoreactive nerves are present in musculoskeletal tissues, and CGRP expression is altered in musculoskeletal pain. CGRP modulates musculoskeletal pain through actions both in the periphery and central nervous system. Human observational studies, research on animal arthritis models and the few reported randomised controlled trials in humans of treatments that target CGRP provide the context of CGRP as a possible pain biomarker or mediator in conditions other than migraine.

Partners in Crime: NGF and BDNF in Visceral Dysfunction

Neurotrophins (NTs), particularly Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF), have attracted increasing attention in the context of visceral function for some years. Here, we examined the current literature and presented a thorough review of the subject. After initial studies linking of NGF to cystitis, it is now well-established that this neurotrophin (NT) is a key modulator of bladder pathologies, including Bladder Pain Syndrome/Interstitial Cystitis (BPS/IC) and Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS. NGF is upregulated in bladder tissue and its blockade results in major improvements on urodynamic parameters and pain. Further studies expanded showed that NGF is also an intervenient in other visceral dysfunctions such as endometriosis and Irritable Bowel Syndrome (IBS). More recently, BDNF was also shown to play an important role in the same visceral dysfunctions, suggesting that both NTs are determinant factors in visceral pathophysiological mechanisms. Manipulation of NGF and BDNF improves visceral function and reduce pain, suggesting that clinical modulation of these NTs may be important; however, much is still to be investigated before this step is taken. Another active area of research is centered on urinary NGF and BDNF. Several studies show that both NTs can be found in the urine of patients with visceral dysfunction in much higher concentration than in healthy individuals, suggesting that they could be used as potential biomarkers. However, there are still technical difficulties to be overcome, including the lack of a large multicentre placebo-controlled studies to prove the relevance of urinary NTs as clinical biomarkers.

Nerve growth factor continuously elevates in a rat rotator cuff tear model

BACKGROUND

Nerve growth factor (NGF) plays a key role in osteoarthritic pain and low back pain. Rotator cuff tear (RCT) is often associated with severe shoulder pain. However, the role of NGF in RCT remains to be fully understood.

METHODS

Rats were divided into sham and RCT groups. The rotator cuff was harvested from the sham and RCT groups on various days for reverse transcription-polymerase chain reaction analysis of Tnfa, Ngf, Il1b, and Cox2 expression. Rotator cuffs from the sham and RCT groups were also harvested at 1 and 14 days for enzyme-linked immunosorbent assay and immunohistochemistry to assess NGF protein levels and localization. Rotator cuff-derived cells were stimulated with rat recombinant tumor necrosis factor (TNF)-α to investigate the involvement of TNF-α in the regulation of NGF expression.

RESULTS

Tnfa and Ngf messenger RNA levels increased within 1 day in the RCT group. Notably, Tnfa and Ngf upregulation persisted for up to 56 days after the RCT surgery, while Il1b and Cox2 expression was significantly reduced. NGF levels in the RCT group were significantly higher than those in the sham operation group on days 1 and 14. Certain inflammatory cells and synovial-like cells lining the surface of the laminated tears were NGF-positive on days 1 and 14, respectively. Ngf messenger RNA levels increased significantly in rotator cuff-derived cells after TNF-α stimulation.

CONCLUSION

NGF levels are continuously elevated in RCT, which is mainly regulated by TNF-α. NGF may thus represent a potential target for therapies that modulate RCT pain.

Growth factor signalling in osteoarthritis

Osteoarthritis (OA) is one of the most common diseases, affecting more than 10% of populations and thus creating immense socioeconomic burden. The pathological changes of OA involve the entire joint, which is composed of multiple types of tissues and cells, exemplified by cartilage degradation, subchondral bone thickening, osteophyte formation, synovium inflammation and hypertrophy, and ligament degeneration. As joint homeostasis requires a complex network of growth factors to regulate anabolic and catabolic events, the dysregulation of growth factor signalling would have negative impacts on structure and function of multiple joint tissues and eventually lead to the onset and progression of OA. In this review, we will discuss TGF-β, NGF, Hedgehog and Wnt, the four growth factors which have received extensive attention in the field of OA and clinical/translational interrogation about their application in OA therapies.

Mechanisms that drive bone pain across the lifespan

Disorders of the skeleton are frequently accompanied by bone pain and a decline in the functional status of the patient. Bone pain occurs following a variety of injuries and diseases including bone fracture, osteoarthritis, low back pain, orthopedic surgery, fibrous dysplasia, rare bone diseases, sickle cell disease and bone cancer. In the past 2 decades, significant progress has been made in understanding the unique population of sensory and sympathetic nerves that innervate bone and the mechanisms that drive bone pain. Following physical injury of bone, mechanotranducers expressed by sensory nerve fibres that innervate bone are activated and sensitized so that even normally non-noxious loading or movement of bone is now being perceived as noxious. Injury of the bone also causes release of factors that; directly excite and sensitize sensory nerve fibres, upregulate proalgesic neurotransmitters, receptors and ion channels expressed by sensory neurons, induce ectopic sprouting of sensory and sympathetic nerve fibres resulting in a hyper-innervation of bone, and central sensitization in the brain that amplifies pain. Many of these mechanisms appear to be involved in driving both nonmalignant and malignant bone pain. Results from human clinical trials suggest that mechanism-based therapies that attenuate one type of bone pain are often effective in attenuating pain in other seemingly unrelated bone diseases. Understanding the specific mechanisms that drive bone pain in different diseases and developing mechanism-based therapies to control this pain has the potential to fundamentally change the quality of life and functional status of patients suffering from bone pain.

Anti-nerve growth factor does not change physical activity in normal young or aging mice but does increase activity in mice with skeletal pain

Anti-nerve growth factor (anti-NGF) therapy has shown significant promise in attenuating several types of skeletal pain. However, whether anti-NGF therapy changes the level of physical activity in individuals with or without skeletal pain is largely unknown. Here, automated day/night activity boxes monitored the effects of anti-NGF treatment on physical activity in normal young (3 months old) and aging (18-23 months old) mice and mice with bone fracture pain. Although aging mice were clearly less active and showed loss of bone mass compared with young mice, anti-NGF treatment had no effect on any measure of day/night activity in either the young or aging mice. By contrast, in mice with femoral fracture pain, anti-NGF treatment produced a clear increase (10%-27%) in horizontal activity, vertical rearing, and velocity of travel compared with the Fracture + Vehicle group. These results suggest, just as in humans, mice titrate their level of physical activity to their level of skeletal pain. The level of skeletal pain may in part be determined by the level of free NGF that seems to rise after injury but not normal aging of the skeleton. In terms of bone healing, animals that received anti-NGF showed an increase in the size of calcified callus but no increase in the number of displaced fractures or time to cortical union. As physical activity is the best nondrug treatment for many patients with skeletal pain, anti-NGF may be useful in reducing pain and promoting activity in these patients.

Anti-nerve growth factor monoclonal antibodies for the control of pain in dogs and cats

Nerve growth factor (NGF) is essential for the survival of sensory and sympathetic neurons during development. However, in the adult, NGF and its interaction with tropomyosin receptor kinase A receptor (TrkA) has been found to play a critical role in nociception and nervous system plasticity in pain conditions. Thus, various monoclonal antibody (mAb) therapies targeting this pathway have been investigated in the development of new pharmacotherapies for chronic pain. Although none of the mAbs against NGF are yet approved for use in humans, they look very promising for the effective control of pain. Recently, species-specific anti-NGF mAbs for the management of osteoarthritis (OA)-associated pain in dogs and cats has been developed, and early clinical trials have been conducted. Anti-NGF therapy looks to be both very effective and very promising as a novel therapy against chronic pain in dogs and cats. This review outlines the mechanism of action of NGF, the role of NGF in osteoarthritis, research in rodent OA models and the current status of the development of anti-NGF mAbs in humans. Furthermore, we describe and discuss the recent development of species-specific anti-NGF mAbs for the treatment of OA-associated pain in veterinary medicine.

Fulranumab as Adjunctive Therapy for Cancer-Related Pain: A Phase 2, Randomized, Double-Blind, Placebo-Controlled, Multicenter Study

This randomized, double-blind (DB), placebo-controlled, phase 2 study assessed the efficacy and safety of fulranumab as a pain therapy adjunctive to opioids in terminally ill cancer patients. Ninety-eight patients were randomized (2:1) to receive one subcutaneous injection of fulranumab (9 mg) or placebo in the 4-week DB phase. Seventy-one (72%) patients entered the 48-week open-label extension phase and were administered 9 mg of fulranumab every 4 weeks. The study failed to demonstrated efficacy at the end of the DB phase (primary endpoint, mean [SD] change in average cancer-related pain intensity was -.8 (1.26) for fulranumab and -.7 (1.56) for placebo; P = .592). However, potential benefit is suggested based on secondary endpoints (30% responder rate [P = .020], Brief Pain Inventory-Short Form [BPI-SF] pain intensity subscale [P = .003], and pain interference subscale [P = .006]). The most commonly reported treatment-emergent adverse events were (fulranumab vs placebo): asthenia (16% vs 10%), decreased appetite (12% vs 6%), fatigue (10% vs 0%), and malignant neoplasm progression (10% vs 0%). Although no differences were seen between fulranumab and placebo groups on the primary endpoint, improvements in BPI-SF pain subscale scores and responder rates support further research of anti-nerve growth factor therapy in cancer-related pain. PERSPECTIVE: Efficacy and safety of fulranumab as adjunctive pain therapy in terminally ill cancer patients were assessed. Results suggest that anti-NGF agents may prove to be novel additions in helping to optimize pain relief in cancer patients who fail to respond adequately to opioids and other common co-analgesics.

Investigational drugs for the treatment of osteoarthritis, an update on recent developments

INTRODUCTION

Osteoarthritis (OA) is the leading cause of pain, loss of function, and disability among elderly, with the knee the most affected joint. It is a heterogeneous condition characterized by complex and multifactorial etiologies which contribute to the broad variation in symptoms presentation and treatment responses that OA patients present. This poses a challenge for the development of effective treatment on OA.

AREAS COVERED

This review will discuss recent development of agents for the treatment of OA, updating our previous narrative review published in 2015. They include drugs for controlling local and systemic inflammation, regulating articular cartilage, targeting subchondral bone, and relieving pain.

EXPERT OPINION

Although new OA drugs such as monoclonal antibodies have shown marked effects and favorable tolerance, current treatment options for OA remain limited. The authors believe there is no miracle drug that can be used for all OA patients'; treatment and disease stage is crucial for the effectiveness of drugs. Therefore, early diagnosis, phenotyping OA patients and precise therapy would expedite the development of investigational drugs targeting at symptoms and disease progression of OA.

Novel treatments for osteoarthritis: an update

Osteoarthritis is the most prevalent chronic joint condition worldwide. The principles of osteoarthritis treatment are to alleviate pain and stiffness as well as maintain function, with current consensus guidelines recommending the use of a combination of conservative measures including physical therapy, analgesia, and surgical interventions such as arthroplasty. In recent years, several pharmacological therapies have emerged as potential alternatives. Although a disease-modifying osteoarthritis drug has yet to be identified, promising results have been reported in recent trials especially with serotonin-norepinephrine reuptake inhibitors, IL-1 antagonists, and antibodies to nerve growth factor. The present review aims to summarize and discuss the latest results of novel treatments for osteoarthritis and potential targets for future research.

Synovial nerve fiber density decreases with naturally-occurring osteoarthritis in horses

OBJECTIVE

To measure the nerve fiber density in synovial membranes from healthy and OA equine joints and to investigate the relationship between synovial innervation and OA severity, synovial vascularity and synovitis.

DESIGN

Twenty-five equine metacarpophalangeal joints were collected post-mortem. The joints were dissected and the macroscopic lesions of the articular cartilage were scored. Synovial membrane specimens (n = 50) were harvested, fixed, sectioned and scored histologically. Immunohistochemical staining and immunofluorescence with S-100 protein, that identifies nerve fibers, and ⍺-actin, that stains vascular smooth muscle, were also performed on site-matched specimens and the relationships between these tissues was interrogated.

RESULTS

The nerve fiber density was higher in the superficial layer (≤200 μm) of the synovium when compared to the deeper layer in control equine joints (mean difference (95% C.I.): 0.054% (0.018%, 0.11%)). In osteoarthritic joints, synovial innervation decreased in the superficial layer with increasing macroscopic OA score (β (SEM), 95% C.I.: -0.0061 (0.00021), -0.0011, -0.00017). The blood vessel density was also higher in the superficial layer of the synovium compared to the deep layer in the control (mean difference (95% C.I.): 1.1% (0.36%, 2.3%)) and OA (mean difference (95% C.I.): 0.60% (0.22%, 1.2%)) equine joints. Moreover, considering all synovial specimens, higher nerve fiber density in the deep layer positively correlated with blood vessel density (β (SEM), 95% C.I.: 0.11 (0.036), 0.035, 0.18).

CONCLUSION

The reduction in nerve fiber density with advanced cartilage degeneration suggests that peripheral neuropathy is associated with equine OA. Whether this link is associated with neuropathic pain, requires further investigation.

Mechanisms of Osteoarthritis (OA) Pain

PURPOSE OF REVIEW

Osteoarthritis (OA) is a major cause of pain and disability worldwide. There is, however, a relatively poor correlation between the severity of OA based on plain radiograph changes and symptoms. In this review, we consider the mechanisms of pain in OA.

RECENT FINDINGS

It is now widely recognised that OA is a disease of the whole joint. Data from large observational studies which have used magnetic resonance imaging (MRI) suggest that pain in OA is associated with a number of structural factors including the presence of bone marrow lesions (BMLs) and also synovitis. There is evidence also of alterations in nerve processing and that both peripheral and central nerve sensitisation may contribute to pain in OA. Identification of the causes of pain in an individual patient may be of benefit in helping to better target with appropriate therapy to help reduce their symptoms and improve function.

Effects of carrageenan induced synovitis on joint damage and pain in a rat model of knee osteoarthritis

OBJECTIVE

Knee osteoarthritis (OA) is associated with ongoing pain and joint damage that can be punctuated by acute flares of pain and inflammation. Synovitis in normal knees might resolve without long-term detriment to joint function. We hypothesised that osteoarthritis is associated with impaired resilience to inflammatory flares.

DESIGN

We induced synovitis by injecting carrageenan into rat knees with or without meniscal transection (MNX)-induced OA, and measured synovitis, weightbearing asymmetry (pain behaviour), and joint damage up to 35 days after OA induction (23 days after carrageenan-injection).

RESULTS

Carrageenan injection induced weightbearing asymmetry for 1 week, transient increase in knee diameter for 2 days, and a sustained increase in synovial macrophages, endothelial cell proliferation and vascular density compared with naive vehicle-injected controls. MNX surgery induced weightbearing asymmetry and histological evidence of OA. Carrageenan-injection in MNX-operated knees was followed for 2 days by increased weightbearing asymmetry compared either to MNX+vehicle or to sham+carrageenan groups. OA structural damage and synovitis at day 35 were greater in MNX+carrageenan compared to MNX+vehicle and sham+carrageenan groups. Carrageenan injection did not induce OA in Sham-operated knees.

CONCLUSION

Intra-articular injection of the pro-inflammatory compound carrageenan in OA and sham-operated control knees induced a short term increase in joint pain. Even though pain flares resolved in both groups and damage was not induced in sham-operated knees, carrageen injection exacerbated long-term joint damage in OA knees. OA knees display less resilience to inflammatory episodes. Preventing inflammatory flares may be particularly important in preventing symptoms and long term joint damage in OA.

Topical thermal therapy with hot packs suppresses physical inactivity-induced mechanical hyperalgesia and up-regulation of NGF

We focused on the analgesic effect of hot packs for mechanical hyperalgesia in physically inactive rats. Male Wistar rats were randomly divided into four groups: control, physical inactivity (PI), PI + sham treatment (PI + sham), and PI + hot pack treatment (PI + hot pack) groups. Physical inactivity rats wore casts on both hind limbs in full plantar flexed position for 4 weeks. Hot pack treatment was performed for 20 min a day, 5 days a week. Although mechanical hyperalgesia and the up-regulation of NGF in the plantar skin and gastrocnemius muscle were observed in the PI and the PI + sham groups, these changes were significantly suppressed in the PI + hot pack group. The present results clearly demonstrated that hot pack treatment was effective in reducing physical inactivity-induced mechanical hyperalgesia and up-regulation of NGF in plantar skin and gastrocnemius muscle.

IL4-10 fusion protein has chondroprotective, anti-inflammatory and potentially analgesic effects in the treatment of osteoarthritis

OBJECTIVE

Effective disease-modifying drugs for osteoarthritis (DMOAD) should preferably have chondroprotective, anti-inflammatory, and analgesic activity combined in a single molecule. We developed a fusion protein of IL4 and IL10 (IL4-10 FP), in which the biological activity of both cytokines is preserved. The present study evaluates the chondroprotective, anti-inflammatory, and analgesic activity of IL4-10 FP in in vitro and in vivo models of osteoarthritis.

METHODS

Human osteoarthritic cartilage tissue and synovial tissue were cultured with IL4-10 FP. Cartilage proteoglycan turnover and release of pro-inflammatory, catabolic, and pain mediators by cartilage and synovial tissue were measured. The analgesic effect of intra-articularly injected IL4-10 FP was evaluated in a canine model of osteoarthritis by force-plate analysis.

RESULTS

IL4-10 FP increased synthesis (P = 0.018) and decreased release (P = 0.018) of proteoglycans by osteoarthritic cartilage. Release of pro-inflammatory IL6 and IL8 by cartilage and synovial tissue was reduced in the presence of IL4-10 FP (all P < 0.05). The release of MMP3 by osteoarthritic cartilage and synovial tissue was decreased (P = 0.018 and 0.028) whereas TIMP1 production was not significantly changed. Furthermore, IL4-10 FP protected cartilage against destructive properties of synovial tissue mediators shown by the increased cartilage proteoglycan synthesis (P = 0.0235) and reduced proteoglycan release (P = 0.0163). Finally, intra-articular injection of IL4-10 FP improved the deficient joint loading in dogs with experimentally induced osteoarthritis.

CONCLUSION

The results of current preliminary study suggest that IL4-10 FP has DMOAD potentials since it shows chondroprotective and anti-inflammatory effects in vitro, as well as potentially analgesic effect in a canine in vivo model of osteoarthritis.

New Insights in Understanding and Treating Bone Fracture Pain

PURPOSE OF REVIEW

This paper describes recent advances in understanding the mechanisms that drive fracture pain and how these findings are helping develop new therapies to treat fracture pain.

RECENT FINDINGS

Immediately following fracture, mechanosensitive nerve fibers that innervate bone are mechanically distorted. This results in these nerve fibers rapidly discharging and signaling the initial sharp fracture pain to the brain. Within minutes to hours, a host of neurotransmitters, cytokines, and nerve growth factor are released by cells at the fracture site. These factors stimulate, sensitize, and induce ectopic nerve sprouting of the sensory and sympathetic nerve fibers which drive the sharp pain upon movement and the dull aching pain at rest. If rapid and effective healing of the fracture occurs, these factors return to baseline and the pain subsides, but if not, these factors can drive chronic bone pain. New mechanism-based therapies have the potential to fundamentally change the way acute and chronic fracture pain is managed.

Systemic Depletion of Nerve Growth Factor Inhibits Disease Progression in a Genetically Engineered Model of Pancreatic Ductal Adenocarcinoma

OBJECTIVES

In patients with pancreatic ductal adenocarcinoma (PDAC), increased expression of proinflammatory neurotrophic growth factors (eg, nerve growth factor [NGF]) correlates with a poorer prognosis, perineural invasion, and, with regard to NGF, pain severity. We hypothesized that NGF sequestration would reduce inflammation and disease in the KPC mouse model of PDAC.

METHODS

Following biweekly injections of NGF antibody or control immunoglobulin G, beginning at 4 or 8 weeks of age, inflammation and disease stage were assessed using histological, protein expression, and quantitative polymerase chain reaction analyses.

RESULTS

In the 8-week anti-NGF group, indicators of neurogenic inflammation in the dorsal root ganglia (substance P and calcitonin gene-related peptide) and spinal cord (glial fibrillary acidic protein) were significantly reduced. In the 4-week anti-NGF group, TRPA1 mRNA in dorsal root ganglia and spinal phosphorylated ERK protein were elevated, but glial fibrillary acidic protein expression was unaffected. In the 8-week anti-NGF group, there was a 40% reduction in the proportion of mice with microscopic perineural invasion, and no macrometastases were observed.

CONCLUSIONS

Anti-NGF treatment beginning at 4 weeks may increase inflammation and negatively impact disease. Treatment starting at 8 weeks (after disease onset), however, reduces neural inflammation, neural invasion, and metastasis. These data indicate that NGF impacts PDAC progression and metastasis in a temporally dependent manner.

Discovery of Potent, Selective, and Peripherally Restricted Pan-Trk Kinase Inhibitors for the Treatment of Pain

Hormones of the neurotrophin family, nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), and neurotrophin 4 (NT4), are known to activate the family of Tropomyosin receptor kinases (TrkA, TrkB, and TrkC). Moreover, inhibition of the TrkA kinase pathway in pain has been clinically validated by the NGF antibody tanezumab, leading to significant interest in the development of small molecule inhibitors of TrkA. Furthermore, Trk inhibitors having an acceptable safety profile will require minimal brain availability. Herein, we discuss the discovery of two potent, selective, peripherally restricted, efficacious, and well-tolerated series of pan-Trk inhibitors which successfully delivered three candidate quality compounds 10b, 13b, and 19. All three compounds are predicted to possess low metabolic clearance in human that does not proceed via aldehyde oxidase-catalyzed reactions, thus addressing the potential clearance prediction liability associated with our current pan-Trk development candidate PF-06273340.

Emerging Treatment Models in Rheumatology: Challenges for Osteoarthritis Trials

At a time when advancing understanding of osteoarthritis (OA) has created opportunities for new treatments, development of treatments has remained considerably behind advances in other rheumatic diseases. We describe elements of trial design and measurements that have inhibited success and offer suggestions that may help break the log jam. Among the problems with trials that include pain as an outcome measure are reliance on a single, non-optimal pain outcome, overestimation of likely effects of treatments on pain, and failure to identify patient subgroups most likely to respond to specific treatments. With regard to the use of structure modification as an outcome measure, demonstrating structure modification is often highly challenging, even with the use of magnetic resonance imaging. Many OA patients have advanced disease that is unlikely to respond to treatments that prevent cartilage loss. Further, prevention of cartilage loss and reduction of pain correlate weakly at best, and in at least some patients, reduction in pain may actually increase joint damage, making it impossible to demonstrate dual treatment effects on structure and pain in such scenarios. For structure outcomes, treatment effects on pain-sensitive structures such as bone and synovium may be more achievable than preventing cartilage loss. We suggest that changes in trial design related to some of these issues may increase the chances that new exciting and effective OA treatments will become available.

Japanese GWAS identifies variants for bust-size, dysmenorrhea, and menstrual fever that are eQTLs for relevant protein-coding or long non-coding RNAs

Traits related to primary and secondary sexual characteristics greatly impact females during puberty and day-to-day adult life. Therefore, we performed a GWAS analysis of 11,348 Japanese female volunteers and 22 gynecology-related phenotypic variables, and identified significant associations for bust-size, menstrual pain (dysmenorrhea) severity, and menstrual fever. Bust-size analysis identified significant association signals in CCDC170-ESR1 (rs6557160; P = 1.7 × 10-16) and KCNU1-ZNF703 (rs146992477; P = 6.2 × 10-9) and found that one-third of known European-ancestry associations were also present in Japanese. eQTL data points to CCDC170 and ZNF703 as those signals' functional targets. For menstrual fever, we identified a novel association in OPRM1 (rs17181171; P = 2.0 × 10-8), for which top variants were eQTLs in multiple tissues. A known dysmenorrhea signal near NGF replicated in our data (rs12030576; P = 1.1 × 10-19) and was associated with RP4-663N10.1 expression, a putative lncRNA enhancer of NGF, while a novel dysmenorrhea signal in the IL1 locus (rs80111889; P = 1.9 × 10-16) contained SNPs previously associated with endometriosis, and GWAS SNPs were most significantly associated with IL1A expression. By combining regional imputation with colocalization analysis of GWAS/eQTL signals along with integrated annotation with epigenomic data, this study further refines the sets of candidate causal variants and target genes for these known and novel gynecology-related trait loci.

Effects of Monoclonal Antibodies against Nerve Growth Factor on Healthy Bone and Joint Tissues in Mice, Rats, and Monkeys: Histopathologic, Biomarker, and Microcomputed Tomographic Assessments

Tanezumab, an anti-nerve growth factor (NGF) antibody, is in development for management of chronic pain. During clinical trials of anti-NGF antibodies, some patients reported unexpected adverse events requiring total joint replacements, resulting in a partial clinical hold on all NGF inhibitors. Three nonclinical toxicology studies were conducted to evaluate the effects of tanezumab or the murine precursor muMab911 on selected bone and joint endpoints and biomarkers in cynomolgus monkeys, Sprague-Dawley rats, and C57BL/6 mice. Joint and bone endpoints included histology, immunohistochemistry, microcomputed tomography (mCT) imaging, and serum biomarkers of bone physiology. Responses of bone endpoints to tanezumab were evaluated in monkeys at 4 to 30 mg/kg/week for 26 weeks and in rats at 0.2 to 10 mg/kg twice weekly for 28 days. The effects of muMab911 at 10 mg/kg/week for 12 weeks on selected bone endpoints were determined in mice. Tanezumab and muMab911 had no adverse effects on any bone or joint parameter. There were no test article–related effects on bone or joint histology, immunohistochemistry, or structure. Reversible, higher osteocalcin concentrations occurred only in the rat study. No deleterious effects were observed in joints or bones in monkeys, rats, or mice administered high doses of tanezumab or muMab911.

Development of pain therapies targeting nerve growth factor signal transduction and the strategies used to resolve safety issues

Therapeutic agents commonly used in the management of chronic pain have limited effectiveness and may be associated with issues of dependence and tolerability. Thus, a large unmet medical need exists for the development of safe and effective therapeutics for treatment of chronic pain. A novel approach includes identification of intracellular signals involved in the pain transduction pathway, such as nerve growth factor (NGF). Monoclonal antibodies targeting NGF, such as tanezumab, fulranumab and fasinumab, have been investigated for the treatment of chronic pain conditions. Due to unexpected joint adverse events in clinical studies and concerns about sympathetic nervous system toxicity in animals, these agents were placed on 2 separate partial clinical holds, which were subsequently lifted after rigorous evaluations were conducted to understand how inhibition of NGF impacts safety. To share learnings regarding the rigorous evaluation of clinical and nonclinical safety data which contributed to the removal of these partial clinical holds, this article reviews the rationale for developing agents that target NGF as potential treatments for chronic pain, describes nonclinical and clinical studies of these agents, and describes strategies used to evaluate whether inhibition of NGF has negative effects on joint or sympathetic nervous system safety.

Role of the Bone Microenvironment in the Development of Painful Complications of Skeletal Metastases

Cancer-induced bone pain (CIBP) is the most common and painful complication in patients with bone metastases. It causes a significant reduction in patient quality of life. Available analgesic treatments for CIBP, such as opioids that target the central nervous system, come with severe side effects as well as the risk of abuse and addiction. Therefore, alternative treatments for CIBP are desperately needed. Although the exact mechanisms of CIBP have not been fully elucidated, recent studies using preclinical models have demonstrated the role of the bone marrow microenvironment (e.g., osteoclasts, osteoblasts, macrophages, mast cells, mesenchymal stem cells, and fibroblasts) in CIBP development. Several clinical trials have been performed based on these findings. CIBP is a complex and challenging condition that currently has no standard effective treatments other than opioids. Further studies are clearly warranted to better understand this painful condition and develop more effective and safer targeted therapies.

First-in-human randomized clinical trials of the safety and efficacy of tanezumab for treatment of chronic knee osteoarthritis pain or acute bunionectomy pain

Supplemental Digital Content is Available in the Text.

Introduction:

The neurotrophin nerve growth factor has a demonstrated role in pain transduction and pathophysiology.

Objectives:

Two randomized, double-blind, placebo-controlled, phase 1 studies were conducted to evaluate safety, tolerability, and analgesic efficacy of single doses of tanezumab, a humanized anti–nerve growth factor monoclonal antibody, in chronic or acute pain.

Methods:

In the first study (CL001), patients with moderate to severe pain from osteoarthritis (OA) of the knee received a single intravenous infusion of tanezumab (3–1000 μg/kg) or placebo in a dose-escalation (part 1; N = 42) or parallel-arm (part 2; N = 79) study design. The second study (CL002) was a placebo-controlled dose-escalation (tanezumab 10–1000 μg/kg; N = 50) study in patients undergoing bunionectomy surgery.

Results:

Adverse event rates were generally similar across treatments. Most adverse events were generally mild to moderate in severity and no patients discontinued as a result of adverse events. Adverse events of abnormal peripheral sensation were more common with higher doses of tanezumab (≥100 μg/kg) than with placebo. These were generally mild to moderate in severity. Tanezumab provided up to 12 weeks of effective analgesia for OA knee pain, with statistically significant improvements at doses ≥100 μg/kg (P < 0.05). By contrast, no trend for analgesic activity was found when tanezumab was administered 8 to 16 hours before bunionectomy.

Conclusions:

The demonstration of a favorable safety profile and clinical efficacy in OA pain supports clinical development of tanezumab as a potential treatment for chronic pain conditions.

Discovery of Allosteric, Potent, Subtype Selective, and Peripherally Restricted TrkA Kinase Inhibitors

Tropomyosin receptor kinases (TrkA, TrkB, TrkC) are activated by hormones of the neurotrophin family: nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), and neurotrophin 4 (NT4). Moreover, the NGF antibody tanezumab has provided clinical proof of concept for inhibition of the TrkA kinase pathway in pain leading to significant interest in the development of small molecule inhibitors of TrkA. However, achieving TrkA subtype selectivity over TrkB and TrkC via a Type I and Type II inhibitor binding mode has proven challenging and Type III or Type IV allosteric inhibitors may present a more promising selectivity design approach. Furthermore, TrkA inhibitors with minimal brain availability are required to deliver an appropriate safety profile. Herein, we describe the discovery of a highly potent, subtype selective, peripherally restricted, efficacious, and well-tolerated series of allosteric TrkA inhibitors that culminated in the delivery of candidate quality compound 23.

What is new in pain modification in osteoarthritis?

There is a big need for the development of novel therapies for the safe management of chronic pain associated with OA. Here we reviewed PubMed (2015 onward) and ClinicalTrials.gov for ongoing and recently completed trials where pain in OA is the primary outcome measure. Three broad categories were identified: biological therapies, small molecules and cryoneurolysis. The most promising new strategy is blockade of nerve growth factor with antibodies. Two anti-nerve growth factor antibodies, tanuzemab and fasinumab, are in active development after the 2010 hold on trials was lifted in 2015. In addition, several active clinical trials are testing distinct mechanism-based interventions, including cytokine inhibition, selective μ, δ or κ opioid receptor agonists, zoledronate and intra-articular capsaicin. In addition to pharmacological approaches, cryoneurolytic strategies that directly target peripheral nerves may play a role in OA pain management, but efficacy profiles and long-term effects of such treatments need more study. Clearly, the therapeutic landscape for OA pain is rapidly expanding. Since symptomatic OA is a heterogeneous disease, the challenge will be to identify patients that will benefit the most from specific approaches.

Positive-Feedback Regulation of Subchondral H-Type Vessel Formation by Chondrocyte Promotes Osteoarthritis Development in Mice

Vascular-invasion-mediated interactions between activated articular chondrocytes and subchondral bone are essential for osteoarthritis (OA) development. Here, we determined the role of nutrient sensing mechanistic target of rapamycin complex 1 (mTORC1) signaling in the crosstalk across the bone cartilage interface and its regulatory mechanisms. Then mice with chondrocyte-specific mTORC1 activation (Tsc1 CKO and Tsc1 CKO^ER ) or inhibition (Raptor CKO^ER ) and their littermate controls were subjected to OA induced by destabilization of the medial meniscus (DMM) or not. DMM or Tsc1 CKO mice were treated with bevacizumab, a vascular endothelial growth factor (VEGF)-A antibody that blocks angiogenesis. Articular cartilage degeneration was evaluated using the Osteoarthritis Research Society International score. Immunostaining and Western blotting were conducted to detect H-type vessels and protein levels in mice. Primary chondrocytes from mutant mice and ADTC5 cells were treated with interleukin-1β to investigate the role of chondrocyte mTORC1 in VEGF-A secretion and in vitro vascular formation. Clearly, H-type vessels were increased in subchondral bone in DMM-induced OA and aged mice. Cartilage mTORC1 activation stimulated VEGF-A production in articular chondrocyte and H-type vessel formation in subchondral bone. Chondrocyte mTORC1 promoted OA partially through formation of VEGF-A-stimulated subchondral H-type vessels. In particular, vascular-derived nutrients activated chondrocyte mTORC1, and stimulated chondrocyte activation and production of VEGF, resulting in further angiogenesis in subchondral bone. Thus a positive-feedback regulation of H-type vessel formation in subchondral bone by articular chondrocyte nutrient-sensing mTORC1 signaling is essential for the pathogenesis and progression of OA. © 2018 American Society for Bone and Mineral Research.

Responsiveness of Single versus Composite Measures of Pain in Knee Osteoarthritis

OBJECTIVE

In rheumatoid arthritis, composite outcomes constructed from a combination of outcome measures are widely used to enhance responsiveness (sensitivity to change) and comprehensively summarize response. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain is the primary outcome measure in many osteoarthritis (OA) trials. Information from other outcomes, such as rescue medication use and other WOMAC subscales, could be added to create composite outcomes, but the sensitivity of such a composite has not been tested.

METHODS

We used data from a completed trial of tanezumab for knee OA (NCT00733902). The WOMAC questionnaire and rescue medication use were measured at several timepoints, up to 16 weeks. Pain and rescue medication outcomes were standardized and combined into 3 composite outcomes through principal components analysis to produce 1 score (composite outcome) and their responsiveness was compared to WOMAC pain, the standard. We pooled all treatment doses of tanezumab into 1 treatment group, for simplicity, and compared this to the control group (placebo).

RESULTS

The composite outcomes showed modestly, but not statistically significantly greater responsiveness when compared to WOMAC pain alone. Adding information on rescue medication to the composite improved responsiveness. While improvements in sensitivity were modest, the required sample sizes for trials using composites was 20-40% less than trials using WOMAC pain alone.

CONCLUSION

Combining information from related but distinct outcomes considered relevant to a particular treatment improved responsiveness, could reduce sample size requirements in OA trials, and might offer a way to better detect treatment efficacy in OA trials.

Anti-nerve growth factor therapy attenuates cutaneous hypersensitivity and musculoskeletal discomfort in mice with osteoporosis

Introduction

The prevalence of osteoporosis is increasing with the aging population and is associated with increased risk of fracture and chronic pain. Osteoporosis is currently treated with bisphosphonate therapy to attenuate bone loss. We previously reported that improvement in bone mineral density is not sufficient to reduce osteoporosis-related pain in an ovariectomy (OVX)-induced mouse model of osteoporosis, highlighting the need for new treatments. Targeting of nerve growth factor (NGF) with sequestering antibodies is a promising new direction for the treatment of musculoskeletal pain including back pain and arthritis. Its efficacy is currently unknown for osteoporotic pain.

Objective

To investigate the efficacy of anti-NGF antibody therapy on osteoporotic pain in an OVX-induced mouse model.

Methods

Ovariectomy- and sham-operated mice were injected with an anti-NGF antibody (10 mg/kg, intraperitoneally, administered 2×, 14 days apart), and the effect on behavioural indices of osteoporosis-related pain and on sensory neuron plasticity was evaluated.

Results

Treatment with anti-NGF antibodies attenuated OVX-induced hypersensitivity to mechanical, cold, and heat stimuli on the plantar surface of the hind paw. The OVX-induced impairment in grip force strength, used here as a measure of axial discomfort, was partially reversed by anti-NGF therapy. No changes were observed in the rotarod or open-field tests for overall motor function and activity. Finally, anti-NGF treatment attenuated the increase in calcitonin gene-related peptide-immunoreactive dorsal root ganglia neurons observed in OVX mice.

Conclusion

Taken together, these data suggest that anti-NGF antibodies may be useful in the treatment of prefracture hypersensitivity that is reported in 10% of patients with osteoporosis.

Implantation of hyaluronic acid hydrogel prevents the pain phenotype in a rat model of intervertebral disc injury

Painful intervertebral disc degeneration is mediated by inflammation that modulates glycosylation and induces hyperinnervation and sensory sensitization, which result in discogenic pain. Hyaluronic acid (HA) used as a therapeutic biomaterial can reduce inflammation and pain, but the effects of HA therapy on glycosylation and pain associated with disc degeneration have not been previously determined. We describe a novel rat model of pain induced by intervertebral disc injury, with validation of the pain phenotype by morphine treatment. Using this model, we assessed the efficacy of HA hydrogel for the alleviation of pain, demonstrating that it reduced nociceptive behavior, an effect associated with down-regulation of nociception markers and inhibition of hyperinnervation. Furthermore, HA hydrogel altered glycosylation and modulated key inflammatory and regulatory signaling pathways, resulting in attenuation of inflammation and regulation of matrix components. Our results suggest that HA hydrogel is a promising clinical candidate for the treatment of back pain caused by degenerated discs.