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Bangari DS, Lanigan LG, Cramer SD, Grieves JL, Meisner R, Rogers AB, Galbreath EJ, Bolon B. Toxicologic Neuropathology of Novel Biotherapeutics. Toxicol Pathol 2023; 51:414-431. [PMID: 38380881 DOI: 10.1177/01926233241230542] [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: 02/22/2024]
Abstract
Biotherapeutic modalities such as cell therapies, gene therapies, nucleic acids, and proteins are increasingly investigated as disease-modifying treatments for severe and life-threatening neurodegenerative disorders. Such diverse bio-derived test articles are fraught with unique and often unpredictable biological consequences, while guidance regarding nonclinical experimental design, neuropathology evaluation, and interpretation is often limited. This paper summarizes key messages offered during a half-day continuing education course on toxicologic neuropathology of neuro-targeted biotherapeutics. Topics included fundamental neurobiology concepts, pharmacology, frequent toxicological findings, and their interpretation including adversity decisions. Covered biotherapeutic classes included cell therapies, gene editing and gene therapy vectors, nucleic acids, and proteins. If agents are administered directly into the central nervous system, initial screening using hematoxylin and eosin (H&E)-stained sections of currently recommended neural organs (brain [7 levels], spinal cord [3 levels], and sciatic nerve) may need to expand to include other components (e.g., more brain levels, ganglia, and/or additional nerves) and/or special neurohistological procedures to characterize possible neural effects (e.g., cell type-specific markers for reactive glial cells). Scientists who evaluate the safety of novel biologics will find this paper to be a practical reference for preclinical safety testing and risk assessment.
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Affiliation(s)
| | | | | | | | - René Meisner
- Denali Therapeutics, South San Francisco, California, USA
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Bolon B. Toxicologic Pathology Forum Opinion: Rational Approaches to Expanded Neurohistopathology Evaluation for Nonclinical General Toxicity Studies and Juvenile Animal Studies. Toxicol Pathol 2023; 51:363-374. [PMID: 38288942 DOI: 10.1177/01926233231225239] [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: 02/10/2024]
Abstract
Existing nervous system sampling and processing "best practices" for nonclinical general toxicity studies (GTS) were designed to assess test articles with unknown, no known, or well-known neurotoxic potential. Similar practices are applicable to juvenile animal studies (JAS). In GTS and JAS, the recommended baseline sampling for all species includes brain (7 sections), spinal cord (cervical and lumbar divisions [cross and longitudinal sections for each]), and 1 nerve (sciatic or tibial [cross and longitudinal sections]) in hematoxylin and eosin-stained sections. Extra sampling and processing (ie, an "expanded neurohistopathology evaluation" [ENHP]) are used for agents with anticipated neuroactivity (toxic ± therapeutic) of incompletely characterized location and degree. Expanded sampling incorporates additional brain (usually 8-15 sections total), spinal cord (thoracic ± sacral divisions), ganglia (somatic ± autonomic, often 2-8 total), and/or nerves (2-6 total) depending on the species and study objectives. Expanded processing typically adds special neurohistological procedures (usually 1-4 for selected samples) to characterize glial reactions, myelin integrity, and/or neuroaxonal damage. In my view, GTS and JAS designs should sample neural tissues at necropsy as if ENHP will be needed eventually, and when warranted ENHP may incorporate expanded sampling and/or expanded processing depending on the study objective(s).
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Berman-Booty LD, Klein SK, Mazur C, Schroeder J, Korte S, Ludwig FT, Romeike A, Bolon B, Grieves JL. Toxicologic Pathology Forum: Opinion on Interpretive Challenges for Procedure-Related Effects Associated With Direct Central Nervous System Delivery of Oligonucleotides to Rodents, Dogs, and Nonhuman Primates. Toxicol Pathol 2023; 51:375-389. [PMID: 38179962 DOI: 10.1177/01926233231218953] [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: 01/06/2024]
Abstract
Direct delivery of therapeutics to the central nervous system (CNS) greatly expands opportunities to treat neurological diseases but is technically challenging. This opinion outlines principal technical aspects of direct CNS delivery via intracerebroventricular (ICV) or intrathecal (IT) injection to common nonclinical test species (rodents, dogs, and nonhuman primates) and describes procedure-related clinical and histopathological effects that confound interpretation of test article-related effects. Direct dosing is by ICV injection in mice due to their small body size, while other species are dosed IT in the lumbar cistern. The most frequent procedure-related functional effects are transient absence of lower spinal reflexes after IT injection or death soon after ICV dosing. Common procedure-related microscopic findings in all species include leukocyte infiltrates in CNS meninges or perivascular (Virchow-Robin) spaces; nerve fiber degeneration in the spinal cord white matter (especially dorsal and lateral tracts compressed by dosing needles or indwelling catheters), spinal nerve roots, and sciatic nerve; meningeal fibrosis at or near IT injection sites; hemorrhage; and gliosis. Findings typically are minimal to occasionally mild. Findings tend to be more severe and/or have a higher incidence in the spinal cord segments and spinal nerve roots at or close to the site of administration.
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Affiliation(s)
| | | | - Curt Mazur
- Ionis Pharmaceuticals, Carlsbad, California, USA
- Creyon Bio, Carlsbad, California, USA
| | | | - Sven Korte
- Labcorp Early Development Services GmbH, Münster, Germany
- Virscio, Inc., New Haven, Connecticut, USA
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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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