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Bennet BM, Pardo ID, Assaf BT, Buza E, Cramer SD, Crawford LK, Engelhardt JA, Galbreath EJ, Grubor B, Morrison JP, Osborne TS, Sharma AK, Bolon B. Scientific and Regulatory Policy Committee Technical Review: Biology and Pathology of Ganglia in Animal Species Used for Nonclinical Safety Testing. Toxicol Pathol 2023; 51:278-305. [PMID: 38047294 DOI: 10.1177/01926233231213851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Dorsal root ganglia (DRG), trigeminal ganglia (TG), other sensory ganglia, and autonomic ganglia may be injured by some test article classes, including anti-neoplastic chemotherapeutics, adeno-associated virus-based gene therapies, antisense oligonucleotides, nerve growth factor inhibitors, and aminoglycoside antibiotics. This article reviews ganglion anatomy, cytology, and pathology (emphasizing sensory ganglia) among common nonclinical species used in assessing product safety for such test articles (TAs). Principal histopathologic findings associated with sensory ganglion injury include neuron degeneration, necrosis, and/or loss; increased satellite glial cell and/or Schwann cell numbers; and leukocyte infiltration and/or inflammation. Secondary nerve fiber degeneration and/or glial reactions may occur in nerves, dorsal spinal nerve roots, spinal cord (dorsal and occasionally lateral funiculi), and sometimes the brainstem. Ganglion findings related to TA administration may result from TA exposure and/or trauma related to direct TA delivery into the central nervous system or ganglia. In some cases, TA-related effects may need to be differentiated from a spectrum of artifactual and/or spontaneous background changes.
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Affiliation(s)
| | | | | | - Elizabeth Buza
- University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | | | | | | | | | - James P Morrison
- Charles River Laboratories, Inc., Shrewsbury, Massachusetts, USA
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Hu HL, Khatri L, Santacruz M, Church E, Moore C, Huang TT, Chao MV. Confronting the loss of trophic support. Front Mol Neurosci 2023; 16:1179209. [PMID: 37456526 PMCID: PMC10338843 DOI: 10.3389/fnmol.2023.1179209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 05/23/2023] [Indexed: 07/18/2023] Open
Abstract
Classic experiments with peripheral sympathetic neurons established an absolute dependence upon NGF for survival. A forgotten problem is how these neurons become resistant to deprivation of trophic factors. The question is whether and how neurons can survive in the absence of trophic support. However, the mechanism is not understood how neurons switch their phenotype to lose their dependence on trophic factors, such as NGF and BDNF. Here, we approach the problem by considering the requirements for trophic support of peripheral sympathetic neurons and hippocampal neurons from the central nervous system. We developed cellular assays to assess trophic factor dependency for sympathetic and hippocampal neurons and identified factors that rescue neurons in the absence of trophic support. They include enhanced expression of a subunit of the NGF receptor (Neurotrophin Receptor Homolog, NRH) in sympathetic neurons and an increase of the expression of the glucocorticoid receptor in hippocampal neurons. The results are significant since levels and activity of trophic factors are responsible for many neuropsychiatric conditions. Resistance of neurons to trophic factor deprivation may be relevant to the underlying basis of longevity, as well as an important element in preventing neurodegeneration.
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Affiliation(s)
- Hui-Lan Hu
- Department of Biochemistry and Molecular Pharmacology, New York University Langone School of Medicine, New York, NY, United States
| | - Latika Khatri
- Skirball Institute for Biomolecular Medicine, Neuroscience Institute, New York University Langone Medical Center, New York, NY, United States
| | - Marilyn Santacruz
- Department of Neuroscience, Pomona College, Claremont, CA, United States
| | - Emily Church
- Department of Neuroscience, Pomona College, Claremont, CA, United States
| | - Christopher Moore
- Skirball Institute for Biomolecular Medicine, Neuroscience Institute, New York University Langone Medical Center, New York, NY, United States
| | - Tony T. Huang
- Department of Biochemistry and Molecular Pharmacology, New York University Langone School of Medicine, New York, NY, United States
| | - Moses V. Chao
- Skirball Institute for Biomolecular Medicine, Neuroscience Institute, New York University Langone Medical Center, New York, NY, United States
- Department of Cell Biology, New York Langone Medical Center, New York, NY, United States
- Department of Psychiatry, New York Langone Medical Center, New York, NY, United States
- Department of Neuroscience and Physiology, New York Langone Medical Center, New York, NY, United States
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Efficacy, General Safety, and Joint Safety of Tanezumab in Japanese Patients with Osteoarthritis: Subgroup Analyses from Two Randomized, Phase 3 Studies. Pain Ther 2022; 11:827-844. [PMID: 35538185 PMCID: PMC9314481 DOI: 10.1007/s40122-022-00384-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 03/29/2022] [Indexed: 01/11/2023] Open
Abstract
INTRODUCTION Tanezumab is a monoclonal antibody against nerve growth factor that is under investigation for the treatment of osteoarthritis (OA) pain. We conducted subgroup analyses of two randomized phase 3 studies to summarize efficacy, general safety, and adjudicated joint safety of tanezumab in Japanese patients with moderate-to-severe OA. METHODS In Study 1 (NCT02528188), patients received subcutaneous tanezumab 2.5 mg or 5 mg every 8 weeks or daily oral nonsteroidal anti-inflammatory drugs (NSAID) for 56 weeks. The co-primary efficacy endpoints were change from baseline in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain subscale score and WOMAC Physical Function subscale score at Week 16 (overall study and Japan-specific endpoints) as well as Patient Global Assessment (PGA)-OA score at Week 16 (overall study endpoint only). In Study 2 (NCT02709486), patients received subcutaneous tanezumab 2.5 mg, 5 mg, or placebo every 8 weeks for 24 weeks. Safety monitoring included adjudicated composite joint safety endpoint (CJSE) including rapidly progressive osteoarthritis type 1 (RPOA1), RPOA2, primary osteonecrosis, pathological fracture, or subchondral insufficiency fracture. RESULTS For Study 1, Japanese patients (n = 200) treated with tanezumab 2.5 mg and 5 mg showed numerically greater improvements in WOMAC Pain, WOMAC Physical Function, and PGA-OA scores versus NSAID at Week 16. Incidences of treatment-emergent adverse events were generally similar between tanezumab 2.5 mg, 5 mg, and NSAID groups. In the integrated safety analysis (Studies 1 + 2; n = 306), ten patients were adjudicated to have a component of CJSE: RPOA1 [tanezumab 2.5 mg (n = 2), tanezumab 5 mg (n = 5)], RPOA2 [tanezumab 2.5 mg (n = 1), tanezumab 5 mg (n = 1)], or primary osteonecrosis [tanezumab 2.5 mg (n = 1)]. Time-adjusted adjudicated rates of RPOA1 and RPOA2 were higher with tanezumab than NSAID or placebo and increased with dose of tanezumab. CONCLUSION Observations from the Japanese subgroup were generally consistent with the overall study populations.
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Palazzi X, Pardo ID, Ritenour H, Rao DB, Bolon B, Garman RH. A Technical Guide to Sampling the Beagle Dog Nervous System for General Toxicity and Neurotoxicity Studies. Toxicol Pathol 2022; 50:432-465. [PMID: 35730663 DOI: 10.1177/01926233221099300] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Beagle dogs are a key nonrodent species in nonclinical safety evaluation of new biomedical products. The Society of Toxicologic Pathology (STP) has published "best practices" recommendations for nervous system sampling in nonrodents during general toxicity studies (Toxicol Pathol 41[7]: 1028-1048, 2013), but their adaptation to the Beagle dog has not been defined specifically. Here we provide 2 trimming schemes suitable for evaluating the unique neuroanatomic features of the dog brain in nonclinical toxicity studies. The first scheme is intended for general toxicity studies (Tier 1) to screen test articles with unknown or no anticipated neurotoxic potential; this plan using at least 7 coronal hemisections matches the STP "best practices" recommendations. The second trimming scheme for neurotoxicity studies (Tier 2) uses up to 14 coronal levels to investigate test articles where the brain is a suspected or known target organ. Collection of spinal cord, ganglia (somatic and autonomic), and nerves for dogs during nonclinical studies should follow published STP "best practices" recommendations for sampling the central (Toxicol Pathol 41[7]: 1028-1048, 2013) and peripheral (Toxicol Pathol 46[4]: 372-402, 2018) nervous systems. This technical guide also demonstrates the locations and approaches to collecting uncommonly sampled peripheral nervous system sites.
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Affiliation(s)
| | | | | | - Deepa B Rao
- Greenfield Pathology Services, Inc., Greenfield, Indiana, USA
| | | | - Robert H Garman
- Consultants in Veterinary Pathology, Inc., Murrysville, Pennsylvania, USA
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5
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Oo WM, Hunter DJ. Nerve Growth Factor (NGF) Inhibitors and Related Agents for Chronic Musculoskeletal Pain: A Comprehensive Review. BioDrugs 2021; 35:611-641. [PMID: 34807432 DOI: 10.1007/s40259-021-00504-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/18/2021] [Indexed: 11/28/2022]
Abstract
Musculoskeletal pain such as osteoarthritis (OA) and low back pain (LBP) are very common and contribute to enormous burden and societal costs, despite dramatic therapeutic advances over recent decades. Novel approaches and targeted therapies are required to satisfy the urgent unmet medical need of musculoskeletal pain relief in both conditions. Nerve growth factor (NGF) inhibitors have utilized novel mechanisms different from conventional drugs, which have a variety of gastrointestinal, cardiac, or renal adverse effects. Several phase 2/3 studies have been accomplished for these drugs, such as tanezumab, fasinumab, and tyrosine receptor kinase A (TrkA) inhibitors. We searched the literature using the PubMed database and clinical trials using ClinicalTrials.gov to identify original papers, meta-analyses as well as ongoing clinical trials assessing the efficacy and safety profile of these drugs. In this narrative review, we briefly overview the disease burden of musculoskeletal pain, the role of NGF signaling and its receptors in the genesis of pain, and the mechanisms of action of inhibitors of NGF signaling and downstream pathways, and then discuss the efficacy and safety of each investigational drug in OA and LBP. Finally, we briefly review two serious adverse effects of NGF inhibitors, namely rapidly progressive OA and sympathetic system effects, and conclude with possible barriers and potential research directions to overcome these.
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Affiliation(s)
- Win Min Oo
- Rheumatology Department, Royal North Shore Hospital, and Institute of Bone and Joint Research, Kolling Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, Australia.,Department of Physical Medicine and Rehabilitation, Mandalay General Hospital, University of Medicine, Mandalay, Mandalay, Myanmar
| | - David J Hunter
- Rheumatology Department, Royal North Shore Hospital, and Institute of Bone and Joint Research, Kolling Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, Australia.
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Pardo ID, Manno RA, Capobianco R, Sargeant AM, Morrison JP, Bolon B, Garman RH. Nervous System Sampling for General Toxicity and Neurotoxicity Studies in the Laboratory Minipig With Emphasis on the Göttingen Minipig. Toxicol Pathol 2021; 49:1140-1163. [PMID: 34423710 DOI: 10.1177/01926233211019941] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The use of minipigs as an alternative nonclinical species has increased in the last 20 years. The Society of Toxicologic Pathology (STP) has produced generic "best practice" recommendations for nervous system sampling in nonrodents during general toxicity studies (Toxicol Pathol 41[7]: 1028-1048, 2013), but their adaptation to the minipig has not been attempted. Here, we describe 2 trimming schemes suitable for evaluating the unique neuroanatomic features of the minipig brain in nonclinical toxicity studies. The first scheme is intended for general toxicity studies (Tier 1) to screen agents with unknown or no anticipated neurotoxic potential; this approach using 7 coronal hemisections accords with the published STP "best practice" recommendations. The second trimming scheme for neurotoxicity studies (Tier 2) uses 14 coronal hemisections and 2 full coronal sections to investigate toxicants where the nervous system is a suspected or known target organ. Collection of spinal cord, ganglia (somatic and autonomic), and nerves from minipigs during nonclinical studies should follow published STP "best practice" recommendations for sampling the central (CNS, Toxicol Pathol 41[7]: 1028-1048, 2013) and peripheral (PNS, Toxicol Pathol 46[4]: 372-402, 2018) nervous systems.
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Affiliation(s)
- Ingrid D Pardo
- Pfizer, Inc, Global Pathology and Investigative Toxicology, Groton, CT, USA
| | - Rosa A Manno
- Pathology Science, ERBC Group, Pomezia (RM), Italy
| | - Raffaella Capobianco
- 426218Janssen Pharmaceutical Companies of Johnson & Johnson, Janssen Research & Development, Nonclinical Safety, Beerse, Belgium
| | | | | | | | - Robert H Garman
- Consultants in Veterinary Pathology, Inc, Murrysville, PA, USA
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D'Arcy Y, Mantyh P, Yaksh T, Donevan S, Hall J, Sadrarhami M, Viktrup L. Treating osteoarthritis pain: mechanisms of action of acetaminophen, nonsteroidal anti-inflammatory drugs, opioids, and nerve growth factor antibodies. Postgrad Med 2021; 133:879-894. [PMID: 34252357 DOI: 10.1080/00325481.2021.1949199] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Osteoarthritis (OA) is a common difficult-to-treat condition where the goal, in the absence of disease-modifying treatments, is to alleviate symptoms such as pain and loss of function. Acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), and opioids are common pharmacologic treatments for OA. Antibodies directed against nerve growth factor (NGF-Abs) are a new class of agents under clinical investigation for the treatment of OA. This narrative review describes (and uses schematics to visualize) nociceptive signaling, chronification of pain, and the mechanisms of action (MOAs) of these different analgesics in the context of OA-related pain pathophysiology. Further, the varying levels of efficacy and safety of these agents observed in patients with OA is examined, based on an overview of published clinical data and/or treatment guidelines (when available), in the context of differences in their MOAs.
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Affiliation(s)
- Yvonne D'Arcy
- Independent Nurse Practitioner, Ponte Vedra Beach, FL, USA
| | - Patrick Mantyh
- Department of Pharmacology and Cancer Center, University of Arizona, Tucson, AZ, USA
| | - Tony Yaksh
- Department of Anesthesiology and Pharmacology, University of California at San Diego, San Diego, CA, USA
| | | | - Jerry Hall
- Lilly Biomedicines, US/Global Medical Affairs, Eli Lilly and Company, Indianapolis, IN, USA
| | | | - Lars Viktrup
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, USA
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Seah KTM, Rammanohar J, Sutton J, To K, Khan WS. The Effectiveness of Anti-Nerve Growth Factor Monoclonal Antibodies in the Management of Pain in Osteoarthritis of the Hip and Knee: A PRISMA Systematic Review and Meta-Analysis. PAIN MEDICINE 2021; 22:1185-1204. [PMID: 33616179 DOI: 10.1093/pm/pnaa441] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE To conduct a systematic review and meta-analysis of the efficacy of anti-nerve growth factor (NGF) monoclonal antibodies in osteoarthritis pain (hip and knee). DESIGN Grade the evidence for anti-NGF use. METHODS An interdisciplinary work group conducted a literature search for anti-NGF use in osteoarthritis. The systematic review was performed in accordance with methods described by the Cochrane collaboration. General inclusion criteria included all osteoarthritis trials studying any monoclonal anti-NGF antibody at any dose/phase. Excluded studies were those where participants received NSAIDs or analgesics other than anti-NGF antibodies. The Jadad Scale score was used to assess the quality of the included studies. RESULTS Thirteen studies were included in the analysis, involving 8145 participants with a diagnosis of hip and/or knee osteoarthritis. Anti-NGF antibody treatment was associated with a significant improvement in all Western Ontario and McMaster Universities Arthritis Index (WOMAC) indices when compared to placebo. These agents were not associated with a significantly increased incidence of serious adverse events but were associated with significant increases in therapy discontinuation due to adverse events or side effects (e.g., peripheral neuropathy). CONCLUSIONS Future randomized clinical trials are needed to characterize the overall risk-to-benefit ratio of anti-NGF antibodies in managing pain associated with OA, particularly with long-term use, in order to verify their efficacy and safety in clinical practice.
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Affiliation(s)
- K T Matthew Seah
- Division of Trauma and Orthopaedic Surgery, University of Cambridge, UK
| | | | - James Sutton
- School of Clinical Medicine, University of Cambridge, UK
| | - Kendrick To
- Division of Trauma and Orthopaedic Surgery, University of Cambridge, UK
| | - Wasim S Khan
- Division of Trauma and Orthopaedic Surgery, University of Cambridge, UK
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Berenbaum F, Schnitzer TJ, Kivitz AJ, Viktrup L, Hickman A, Pixton G, Brown MT, Davignon I, West CR. General Safety and Tolerability of Subcutaneous Tanezumab for Osteoarthritis: A Pooled Analysis of 3 Randomized, Placebo-Controlled Trials. Arthritis Care Res (Hoboken) 2021; 74:918-928. [PMID: 33973384 PMCID: PMC9310640 DOI: 10.1002/acr.24637] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 04/07/2021] [Accepted: 04/27/2021] [Indexed: 11/08/2022]
Abstract
Objective This pooled analysis of 3 randomized, placebo‐controlled trials (16–24 week treatment and 8–24 week follow‐up) assessed safety of subcutaneous tanezumab (2.5–10 mg every 8 weeks) in 1,840 patients with hip or knee osteoarthritis. Methods Overall treatment‐emergent adverse events (TEAEs) and TEAEs of abnormal peripheral sensation (APS) were prospectively assessed in 3 trials. Joint safety events (primary osteonecrosis, rapidly progressive osteoarthritis [RPOA], subchondral insufficiency fracture, and pathologic fracture; adjudicated by an independent expert committee) and TEAEs potentially associated with sympathetic neuropathy were prospectively assessed in 2 trials. Results During the treatment period, overall TEAE rates were 51.7% for placebo and 39.5–54.8% for tanezumab 2.5–10 mg; treatment discontinuation rates were 2.0% for placebo and 0–1.3% for tanezumab. Rates of composite joint safety events (predominantly RPOA type 1) over the treatment plus follow‐up period were 0% for placebo and 0.5–3.2% for tanezumab 2.5–5 mg (5 mg was statistically greater than placebo); total joint replacement rates with tanezumab (5.9–7.0%) were not significantly different from placebo (4.5%). Rates of TEAEs of APS (predominantly paresthesia and hypoesthesia) were 2.2% for placebo and 3.2–12.8% for tanezumab 2.5–10 mg. Rates of TEAEs potentially associated with sympathetic neuropathy (predominantly bradycardia and orthostatic hypotension) were 0.8% for placebo and 0.5–2.8% for tanezumab 2.5–5 mg (exposure‐adjusted rates were not significantly different from placebo). Conclusion Tanezumab was generally well tolerated. TEAEs of APS (mostly mild and transient) and joint safety events were infrequent but more common with tanezumab than placebo. A tanezumab dose of 2.5 mg demonstrated a more favorable safety profile than higher doses.
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Affiliation(s)
- Francis Berenbaum
- Sorbonne Université, INSERM, AP-HP Hospital Saint Antoine, Paris, France
| | - Thomas J Schnitzer
- Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Alan J Kivitz
- Altoona Center for Clinical Research, Duncansville, Pennsylvania, USA
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Targeting Nerve Growth Factor for Pain Management in Osteoarthritis-Clinical Efficacy and Safety. Rheum Dis Clin North Am 2021; 47:181-195. [PMID: 33781489 DOI: 10.1016/j.rdc.2020.12.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Nerve growth factor (NGF) is a neurotrophin that mediates pain sensitization in pathologic states, including osteoarthritis. In clinical trials, antibodies to NGF reduce pain and improve physical function due to osteoarthritis of the knee or hip and have a long duration of action. Rapidly progressive osteoarthritis is a dose-dependent adverse event with these agents, and additional joint safety signals, such as subchondral insufficiency fractures and increased rates of total joint replacement, are reported. The effects on pain and potential mechanisms behind these joint events both are of considerable importance in the consideration of future use of anti-NGF therapies for osteoarthritis.
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11
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Kigami D, Butt MT, Brown DL, Matsumoto M, Ito H. Neurotoxicity studies with a tropomyosin-related kinase A inhibitor, ASP7962, on the sympathetic and sensory nervous systems in rats. Toxicol Lett 2021; 344:34-45. [PMID: 33667609 DOI: 10.1016/j.toxlet.2021.02.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 01/21/2021] [Accepted: 02/28/2021] [Indexed: 11/30/2022]
Abstract
ASP7962 is a small molecule inhibitor for the nerve growth factor (NGF) receptor, tropomyosin-related kinase A (TrkA). NGF contributes to the survival of sensory and sympathetic neurons through TrkA receptor activation. Gross, microscopic, and quantitative effects to the nervous system were evaluated following oral ASP7962 administration to Sprague Dawley rats for 4 weeks and 13 weeks and after a recovery period. Histopathological findings included reversible neuronal atrophy but no neuronal death in the sympathetic ganglia (cervicothoracic ganglion, cranial mesenteric ganglion or superior [cranial] cervical ganglion). Stereological analysis showed reversible decreased ganglion volume and/or decreased neuron size in the superior (cranial) cervical ganglion in both the 4-week and the 13-week repeated dose studies. There were no test article related changes in the brain, dorsal root ganglia with spinal nerve roots or trigeminal ganglia and no functional deficits. ASP7962 did not cause any detectable dysfunction of the sympathetic and sensory nervous system in either study.
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Affiliation(s)
- Daisuke Kigami
- Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Ibaraki, Japan.
| | - Mark T Butt
- Tox Path Specialists, A StageBio Company, Frederick, MD, United States of America
| | - Danielle L Brown
- Charles River Laboratories, Inc., Durham, NC, United States of America
| | | | - Hiroyuki Ito
- Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Ibaraki, Japan
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Sapio MR, Vazquez FA, Loydpierson AJ, Maric D, Kim JJ, LaPaglia DM, Puhl HL, Lu VB, Ikeda SR, Mannes AJ, Iadarola MJ. Comparative Analysis of Dorsal Root, Nodose and Sympathetic Ganglia for the Development of New Analgesics. Front Neurosci 2021; 14:615362. [PMID: 33424545 PMCID: PMC7793666 DOI: 10.3389/fnins.2020.615362] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 11/25/2020] [Indexed: 12/18/2022] Open
Abstract
Interoceptive and exteroceptive signals, and the corresponding coordinated control of internal organs and sensory functions, including pain, are received and orchestrated by multiple neurons within the peripheral, central and autonomic nervous systems. A central aim of the present report is to obtain a molecularly informed basis for analgesic drug development aimed at peripheral rather than central targets. We compare three key peripheral ganglia: nodose, sympathetic (superior cervical), and dorsal root ganglia in the rat, and focus on their molecular composition using next-gen RNA-Seq, as well as their neuroanatomy using immunocytochemistry and in situ hybridization. We obtained quantitative and anatomical assessments of transmitters, receptors, enzymes and signaling pathways mediating ganglion-specific functions. Distinct ganglionic patterns of expression were observed spanning ion channels, neurotransmitters, neuropeptides, G-protein coupled receptors (GPCRs), transporters, and biosynthetic enzymes. The relationship between ganglionic transcript levels and the corresponding protein was examined using immunohistochemistry for select, highly expressed, ganglion-specific genes. Transcriptomic analyses of spinal dorsal horn and intermediolateral cell column (IML), which form the termination of primary afferent neurons and the origin of preganglionic innervation to the SCG, respectively, disclosed pre- and post-ganglionic molecular-level circuits. These multimodal investigations provide insight into autonomic regulation, nodose transcripts related to pain and satiety, and DRG-spinal cord and IML-SCG communication. Multiple neurobiological and pharmacological contexts can be addressed, such as discriminating drug targets and predicting potential side effects, in analgesic drug development efforts directed at the peripheral nervous system.
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Affiliation(s)
- Matthew R Sapio
- Anesthesia Section, Department of Perioperative Medicine, National Institutes of Health Clinical Center, Bethesda, MD, United States
| | - Fernando A Vazquez
- Anesthesia Section, Department of Perioperative Medicine, National Institutes of Health Clinical Center, Bethesda, MD, United States
| | - Amelia J Loydpierson
- Anesthesia Section, Department of Perioperative Medicine, National Institutes of Health Clinical Center, Bethesda, MD, United States
| | - Dragan Maric
- Flow and Imaging Cytometry Core Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States
| | - Jenny J Kim
- Anesthesia Section, Department of Perioperative Medicine, National Institutes of Health Clinical Center, Bethesda, MD, United States
| | - Danielle M LaPaglia
- Anesthesia Section, Department of Perioperative Medicine, National Institutes of Health Clinical Center, Bethesda, MD, United States
| | - Henry L Puhl
- Section on Neurotransmitter Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, United States
| | - Van B Lu
- Section on Neurotransmitter Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, United States
| | - Stephen R Ikeda
- Section on Neurotransmitter Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, United States
| | - Andrew J Mannes
- Anesthesia Section, Department of Perioperative Medicine, National Institutes of Health Clinical Center, Bethesda, MD, United States
| | - Michael J Iadarola
- Anesthesia Section, Department of Perioperative Medicine, National Institutes of Health Clinical Center, Bethesda, MD, United States
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Abstract
The prevalence of osteoarthritis (OA) and the burden associated with the disease are steadily increasing worldwide, representing a major public health challenge for the coming decades. The lack of specific treatments for OA has led to it being recognized as a serious disease that has an unmet medical need. Advances in the understanding of OA pathophysiology have enabled the identification of a variety of potential therapeutic targets involved in the structural progression of OA, some of which are promising and under clinical investigation in randomized controlled trials. Emerging therapies include those targeting matrix-degrading proteases or senescent chondrocytes, promoting cartilage repair or limiting bone remodelling, local low-grade inflammation or Wnt signalling. In addition to these potentially disease-modifying OA drugs (DMOADs), several targets are being explored for the treatment of OA-related pain, such as nerve growth factor inhibitors. The results of these studies are expected to considerably reshape the landscape of OA management over the next few years. This Review describes the pathophysiological processes targeted by emerging therapies for OA, along with relevant clinical data and discussion of the main challenges for the further development of these therapies, to provide context for the latest advances in the field of pharmaceutical therapies for OA.
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14
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Pardo ID, Rao DB, Morrison JP, Huddleston C, Bradley AE, Bolon B, Garman RH. Nervous System Sampling for General Toxicity and Neurotoxicity Studies in Rabbits. Toxicol Pathol 2020; 48:810-826. [PMID: 33094688 DOI: 10.1177/0192623320957637] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Although manuscripts for multiple species recommending nervous system sampling for histopathology evaluation in safety assessment have been published in the past 15 years, none have addressed the laboratory rabbit. Here, we describe 2 trimming schemes for evaluating the rabbit brain in nonclinical toxicity studies. In both schemes, the intact brain is cut in the coronal plane to permit bilateral assessment. The first scheme is recommended for general toxicity studies (tier 1) in screening agents where there is no anticipated neurotoxic potential; this 6-section approach is consistent with the Society of Toxicologic Pathology (STP) "best practice" recommendations for brain sampling in nonrodents (Toxicol Pathol 41: 1028-1048, 20131). The second trimming scheme is intended for dedicated neurotoxicity studies (tier 2) to characterize known or suspected neurotoxicants where the nervous system is a key target organ. This tier 2 strategy relies on coronal trimming of the whole brain into 3-mm-thick slices and then evaluating 12 sections. Collection of spinal cord, ganglia, and nerve specimens for rabbits during nonclinical studies should follow published STP "best practice" recommendations for sampling the central nervous system1 and peripheral nervous system (Toxicol Pathol 46: 372-402, 20182).
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Affiliation(s)
- Ingrid D Pardo
- 390190Pfizer, Inc, Global Pathology and Investigative Toxicology, Groton, CT, USA
| | - Deepa B Rao
- ToxPath Specialists, LLC (a StageBio Company), Frederick, MD, USA
| | | | - Colleen Huddleston
- 390190Pfizer, Inc, Global Pathology and Investigative Toxicology, Groton, CT, USA
| | - Alys E Bradley
- 57146Charles River Laboratories Edinburgh Ltd, Tranent, East Lothian, Scotland, United Kingdom
| | | | - Robert H Garman
- Consultants in Veterinary Pathology, Inc, Murrysville, Pennsylvania, PA, USA
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15
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Nerve growth factor antibody for the treatment of osteoarthritis pain and chronic low-back pain: mechanism of action in the context of efficacy and safety. Pain 2020; 160:2210-2220. [PMID: 31145219 PMCID: PMC6756297 DOI: 10.1097/j.pain.0000000000001625] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Chronic pain continues to be a significant global burden despite the availability of a variety of nonpharmacologic and pharmacologic treatment options. Thus, there is a need for new analgesics with novel mechanisms of action. In this regard, antibodies directed against nerve growth factor (NGF-Abs) are a new class of agents in development for the treatment of chronic pain conditions such as osteoarthritis and chronic low-back pain. This comprehensive narrative review summarizes evidence supporting pronociceptive functions for NGF that include contributing to peripheral and central sensitization through tropomyosin receptor kinase A activation and stimulation of local neuronal sprouting. The potential role of NGF in osteoarthritis and chronic low-back pain signaling is also examined to provide a mechanistic basis for the observed efficacy of NGF-Abs in clinical trials of these particular pain states. Finally, the safety profile of NGF-Abs in terms of common adverse events, joint safety, and nerve structure/function is discussed.
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16
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Abstract
Supplemental Digital Content is Available in the Text. A ligand-guided, light-activated photosensitizer tool targets TrkA-expressing nociceptors, reversing acute and chronic pain in mice. Nerve growth factor (NGF) and its receptors TrkA and p75 play a key role in the development and function of peripheral nociceptive neurons. Here, we describe novel technology to selectively photoablate TrkA-positive nociceptors through delivery of a phototoxic agent coupled to an engineered NGF ligand and subsequent near-infrared illumination. We demonstrate that this approach allows for on demand and localized reversal of pain behaviors in mouse models of acute, inflammatory, neuropathic, and joint pain. To target peripheral nociceptors, we generated a SNAP-tagged NGF derivative NGFR121W that binds to TrkA/p75 receptors but does not provoke signaling in TrkA-positive cells or elicit pain behaviors in mice. NGFR121W-SNAP was coupled to the photosensitizer IRDye700DX phthalocyanine (IR700) and injected subcutaneously. After near-infrared illumination of the injected area, behavioral responses to nociceptive mechanical and sustained thermal stimuli, but not innocuous stimuli, were substantially reduced. Similarly, in models of inflammatory, osteoarthritic, and neuropathic pain, mechanical hypersensitivity was abolished for 3 weeks after a single treatment regime. We demonstrate that this loss of pain behavior coincides with the retraction of neurons from the skin which then reinnervate the epidermis after 3 weeks corresponding with the return of mechanical hypersensitivity. Thus NGFR121W-SNAP-mediated photoablation is a minimally invasive approach to reversibly silence nociceptor input from the periphery, and control pain and hypersensitivity to mechanical stimuli.
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17
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Berenbaum F, Blanco FJ, Guermazi A, Miki K, Yamabe T, Viktrup L, Junor R, Carey W, Brown MT, West CR, Verburg KM. Subcutaneous tanezumab for osteoarthritis of the hip or knee: efficacy and safety results from a 24-week randomised phase III study with a 24-week follow-up period. Ann Rheum Dis 2020; 79:800-810. [PMID: 32234715 PMCID: PMC7286052 DOI: 10.1136/annrheumdis-2019-216296] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 01/28/2020] [Accepted: 01/29/2020] [Indexed: 11/21/2022]
Abstract
Objective Tanezumab, a nerve growth factor inhibitor, was investigated for osteoarthritis (OA) of the hip or knee in a study with 24-week treatment and 24-week safety follow-up. Methods This double-blind, randomised, phase III study enrolled adults in Europe and Japan with moderate-to-severe OA who had not responded to or could not tolerate standard-of-care analgesics. Patients were randomised to tanezumab 2.5 mg or 5 mg subcutaneously or matching placebo every 8 weeks (three doses). Co-primary end points were change from baseline to week 24 in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain and Physical Function, and Patient’s Global Assessment of OA (PGA-OA). Joint safety and neurological assessments continued throughout the 48-week study. Results From March 2016 to December 2017, 849 patients were randomised and evaluated (placebo n=282, tanezumab 2.5 mg n=283, tanezumab 5 mg n=284). At week 24, there was a statistically significant improvement from baseline for tanezumab 5 mg compared with placebo for WOMAC Pain (least squares mean difference±SE –0.62±0.18, p=0.0006), WOMAC Physical Function (–0.71±0.17, p<0.0001) and PGA-OA (–0.19±0.07, p=0.0051). For tanezumab 2.5 mg, there was a statistically significant improvement in WOMAC Pain and Physical Function, but not PGA-OA. Rapidly progressive osteoarthritis (RPOA) was observed in 1.4% (4/283) and 2.8% (8/284) of patients in the tanezumab 2.5 mg and tanezumab 5 mg groups, respectively and none receiving placebo. Total joint replacements (TJRs) were similarly distributed across all three treatment groups (6.7%–7.8%). Tanezumab-treated patients experienced more paraesthesia (5 mg) and hypoaesthesia (both doses) than placebo. Conclusion Tanezumab 5 mg statistically significantly improved pain, physical function and PGA-OA, but tanezumab 2.5 mg only achieved two co-primary end points. RPOA occurred more frequently with tanezumab 5 mg than tanezumab 2.5 mg. TJRs were similarly distributed across all three groups. Trial registration number NCT02709486.
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Affiliation(s)
- Francis Berenbaum
- Department of Rheumatology, Sorbonne Université, INSERM CRSA, AP-HP Hopital Saint Antoine, Paris, France
| | - Francisco J Blanco
- Servicio de Reumatología, INIBC-Complejo Hospitalario Universitario A Coruña, La Coruña, Spain
| | - Ali Guermazi
- Department of Radiology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Kenji Miki
- Faculty of Health Science, Osaka Yukioka College of Health Science, Hayaishi Hospital, Osaka, Japan
| | | | - Lars Viktrup
- Eli Lilly and Company, Indianapolis, Indiana, USA
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18
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Abstract
Many preclinical investigations limit the evaluation of the peripheral nervous system (PNS) to paraffin-embedded sections/hematoxylin and eosin–stained sections of the sciatic nerve. This limitation ignores several key mechanisms of toxicity and anatomic differences that may interfere with an accurate assessment of test article effects on the neurons/neurites peripheral to the brain and spinal cord. Ganglion neurons may be exposed to higher concentrations of the test article as compared to neurons in the brain or spinal cord due to differences in capillary permeability. Many peripheral neuropathies are length-dependent, meaning distal nerves may show morphological changes before they are evident in the mid-sciatic nerve. Paraffin-embedded nerves are not optimal to assess myelin changes, notably those leading to demyelination. Differentiating between axonal or myelin degeneration may not be possible from the examination of paraffin-embedded sections. A sampling strategy more consistent with known mechanisms of toxicity, atraumatic harvest of tissues, optimized fixation, and the use of resin and paraffin-embedded sections will greatly enhance the pathologist’s ability to observe and characterize effects in the PNS.
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19
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Evans M, Butt M, Belanger P, Cummings T, Gremminger JL, Zorbas M. Effects of tanezumab on satellite glial cells in the cervicothoracic ganglion of cynomolgus monkeys: A 26-week toxicity study followed by an 8-week recovery period. Auton Neurosci 2019; 218:51-53. [DOI: 10.1016/j.autneu.2019.02.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 01/25/2019] [Accepted: 02/17/2019] [Indexed: 01/04/2023]
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20
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Walters KM, Boucher M, Boucher GG, Opsahl AC, Mouton PR, Liu CN, Ritenour CR, Kawabe TT, Pryski HN, Somps CJ. No Evidence of Neurogenesis in Adult Rat Sympathetic Ganglia Following Guanethidine-Induced Neuronal Loss. Toxicol Pathol 2019; 48:228-237. [PMID: 30987556 DOI: 10.1177/0192623319843052] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The potential for neurogenesis in the cranial (superior) cervical ganglia (SCG) of the sympathetic nervous system was evaluated. Eleven consecutive daily doses of guanethidine (100 mg/kg/d) were administered intraperitoneally to rats in order to destroy postganglionic sympathetic neurons in SCG. Following the last dose, animals were allowed to recover 1, 3, or 6 months. Right and left SCG from guanethidine-treated and age-matched, vehicle-treated control rats were harvested for histopathologic, morphometric, and stereologic evaluations. Both morphometric and stereologic evaluations confirmed neuron loss following guanethidine treatment. Morphometric analysis revealed a 50% to 60% lower number of tyrosine hydroxylase (TH)-positive neurons per unit area of SCG at both 3 and 6 months of recovery, compared to ganglia of age-matched controls, with no evidence of restoration of neuron density between 3 and 6 months. Reductions in TH-positive neurons following guanethidine treatment were corroborated by unbiased stereology of total hematoxylin and eosin-stained neuron numbers in SCG. Stereologic analyses revealed that total neuron counts were lower by 37% at 3 months of recovery when compared to age-matched vehicle controls, again with no obvious restoration between 3 and 6 months. Thus, no evidence was found that postganglionic neurons of the sympathetic nervous system in the adult rat have a neurogenic capacity.
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Affiliation(s)
- Karen M Walters
- Pfizer Drug Safety Research and Development, Groton, CT, USA
| | - Magalie Boucher
- Pfizer Drug Safety Research and Development, Groton, CT, USA
| | | | - Alan C Opsahl
- Pfizer Drug Safety Research and Development, Groton, CT, USA
| | - Peter R Mouton
- SRC Biosciences, Stereology Resource Center, Inc, Tampa, FL, USA
| | - Chang-Ning Liu
- Pfizer Drug Safety Research and Development, Groton, CT, USA
| | | | - Thomas T Kawabe
- Pfizer Drug Safety Research and Development, Groton, CT, USA
| | - Hayley N Pryski
- Pfizer Drug Safety Research and Development, Groton, CT, USA
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21
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Rocca M, Han C, Butt M, Coogan TP. Evaluation of the Toxicity and Neurological Effects of Fulranumab in Adult Cynomolgus Monkeys. Int J Toxicol 2019; 38:173-182. [DOI: 10.1177/1091581819830980] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Fulranumab, an anti-human nerve growth factor antibody, was evaluated in a series of nonclinical toxicology studies. No treatment effects were observed in adolescent cynomolgus monkeys in standard design, repeat-dose toxicology studies of up to 6 months. Adverse effects on the developing nervous system were observed in offspring of pregnant cynomolgus monkeys treated with fulranumab. Subsequent studies including detailed morphologic investigations of the nervous system did reveal fulranumab-related changes in adult cynomolgus monkeys; this article is focused on those findings. A single dose of ≥1 mg/kg fulranumab administered subcutaneously (SC) caused a decrease in neuron and sympathetic ganglion size (superior cervical ganglion), observed morphologically and stereologically, with a resulting appearance of increased glial cell density. Similar results were observed in repeat-dose (15 to 52 weeks) toxicity studies at ≤50 mg/kg/wk fulranumab SC. These effects recovered after a 3-month treatment-free period. Fulranumab did not cause any neuronal death, necrosis, apoptosis, or any apparent decrease in function of sympathetic neurons/ganglia at any time point examined. A no observed effect level (NOEL) was established at 0.25 mg/kg fulranumab SC every 4 weeks for 28 weeks.
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Affiliation(s)
| | - Chao Han
- Janssen R&D, LLC, Spring House, PA, USA
| | - Mark Butt
- Tox Path Specialists, LLC, Walkersville, MD, USA
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22
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Enomoto M, Mantyh PW, Murrell J, Innes JF, Lascelles BDX. Anti-nerve growth factor monoclonal antibodies for the control of pain in dogs and cats. Vet Rec 2018; 184:23. [PMID: 30368458 PMCID: PMC6326241 DOI: 10.1136/vr.104590] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 07/10/2018] [Accepted: 09/19/2018] [Indexed: 12/13/2022]
Abstract
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.
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Affiliation(s)
- Masataka Enomoto
- Translational Research in Pain, Comparative Pain Research and Education Centre, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA
| | - Patrick W Mantyh
- Cancer Center's Cancer Biology Program, Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona, USA
| | - Joanna Murrell
- School of Veterinary Sciences, University of Bristol, Bristol, UK
| | | | - B Duncan X Lascelles
- Translational Research in Pain, Comparative Pain Research and Education Centre, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.,Comparative Medicine Institute, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.,Center for Pain Research and Innovation, UNC School of Dentistry, Chapel Hill, North Carolina, USA.,Center for Translational Pain Research, Department of Anesthesiology, Duke University, Durham, North Carolina, USA
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23
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Bélanger P, West CR, Brown MT. Development of pain therapies targeting nerve growth factor signal transduction and the strategies used to resolve safety issues. J Toxicol Sci 2018; 43:1-10. [PMID: 29415946 DOI: 10.2131/jts.43.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
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.
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24
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Drug Targets in Neurotrophin Signaling in the Central and Peripheral Nervous System. Mol Neurobiol 2018; 55:6939-6955. [PMID: 29372544 DOI: 10.1007/s12035-018-0885-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 01/08/2018] [Indexed: 12/12/2022]
Abstract
Neurotrophins are a family of proteins that play an important role in the regulation of the growth, survival, and differentiation of neurons in the central and peripheral nervous system. Neurotrophins were earlier characterized by their role in early development, growth, maintenance, and the plasticity of the nervous system during development, but recent findings also indicate their complex role during normal physiology in both neuronal and non-neuronal tissues. Therefore, it is important to recognize a deficiency in the expression of neurotrophins, a major factor driving the debilitating features of several neurologic and psychiatric diseases/disorders. On the other hand, overexpression of neurotrophins is well known to play a critical role in pathogenesis of chronic pain and afferent sensitization, underlying conditions such as lower urinary tract symptoms (LUTS)/disorders and osteoarthritis. The existence of a redundant receptor system of high-and low-affinity receptors accounts for the diverse, often antagonistic, effects of neurotrophins in neurons and non-neuronal tissues in a spatial and temporal manner. In addition, studies looking at bladder dysfunction because of conditions such as spinal cord injury and diabetes mellitus have found alterations in the levels of these neurotrophins in the bladder, as well as in sensory afferent neurons, which further opens a new avenue for therapeutic targets. In this review, we will discuss the characteristics and roles of key neurotrophins and their involvement in the central and periphery nervous system in both normal and diseased conditions.
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