A large number of mouse models have been engineered, characterized and used to advance biomedical research in Alzheimer disease (AD). Early models simply damaged the rodent brain through toxins or ...lesions. Later, the spread of genetic engineering technology enabled investigators to develop models of familial AD by overexpressing human genes such as those encoding amyloid precursor protein (APP) or presenilins (PSEN1 or PSEN2) carrying mutations linked to early-onset AD. Recently, more complex models have sought to explore the impact of multiple genetic risk factors in the context of different biological challenges. Although none of these models has proven to be a fully faithful reproduction of the human disease, models remain essential as tools to improve our understanding of AD biology, conduct thorough pharmacokinetic and pharmacodynamic analyses, discover translatable biomarkers and evaluate specific therapeutic approaches. To realize the full potential of animal models as new technologies and knowledge become available, it is critical to define an optimal strategy for their use. Here, we review progress and challenges in the use of AD mouse models, highlight emerging scientific innovations in model development, and introduce a conceptual framework for use of preclinical models for therapeutic development.
After traumatic brain injury (TBI), neurons surviving the initial insult can undergo chronic (secondary) degeneration via poorly understood mechanisms, resulting in long-term cognitive impairment. ...Although a neuroinflammatory response is promptly activated after TBI, it is unknown whether it has a significant role in chronic phases of TBI (>1 year after injury). Using a closed-head injury model of TBI in mice, we showed by MRI scans that TBI caused substantial degeneration at the lesion site within a few weeks and these did not expand significantly thereafter. However, chronic alterations in neurons were observed, with reduced dendritic spine density lasting >1 year after injury. In parallel, we found a long-lasting inflammatory response throughout the entire brain. Deletion of one allele of CX3CR1, a chemokine receptor, limited infiltration of peripheral immune cells and largely prevented the chronic degeneration of the injured brain and provided a better functional recovery in female, but not male, mice. Therefore, targeting persistent neuroinflammation presents a new therapeutic option to reduce chronic neurodegeneration.
Traumatic brain injury (TBI) often causes chronic neurological problems including epilepsy, neuropsychiatric disorders, and dementia through unknown mechanisms. Our study demonstrates that inflammatory cells invading the brain lead to secondary brain damage. Sex-specific amelioration of chronic neuroinflammation rescues the brain degeneration and results in improved motor functions. Therefore, this study pinpoints an effective therapeutic approach to preventing secondary complications after TBI.
Receptor‐interacting serine/threonine‐protein kinase 1 (RIPK1) regulates inflammation, cytokine release, and necroptotic cell death and is implicated in pathogenic cellular pathways in amyotrophic ...lateral sclerosis (ALS), Alzheimer's disease (AD), and multiple sclerosis. Inhibition of RIPK1 activity protects against inflammation and cell death in multiple animal models. DNL104 is a selective, brain‐penetrant inhibitor of RIPK1 phosphorylation in clinical development for AD and ALS. DNL104 was tested in 68 healthy volunteers to investigate safety and tolerability, pharmacokinetic profile in plasma and cerebrospinal fluid, and pharmacodynamic effects of RIPK1 inhibition in peripheral blood mononuclear cells in a first‐in‐human, placebo‐controlled, double‐blind, randomized single‐ascending dose (SAD) and multiple‐ascending dose (MAD) study. DNL104 was well‐tolerated in the SAD group and during the dosing period of the MAD group. However, postdose liver toxicity in 37.5% of subjects was observed in the MAD, and assessed to be drug related. We demonstrate that DNL104 leads to RIP1 kinase inhibition, and this is not associated with central nervous system (CNS) toxicities, supporting future development of CNS penetrant RIPK1 inhibitors.
RIPK1 is a master regulator of inflammatory signaling and cell death and increased RIPK1 activity is observed in human diseases, including Alzheimer’s disease (AD) and amyotrophic lateral sclerosis ...(ALS). RIPK1 inhibition has been shown to protect against cell death in a range of preclinical cellular and animal models of diseases. SAR443060 (previously DNL747) is a selective, orally bioavailable, central nervous system (CNS)–penetrant, small‐molecule, reversible inhibitor of RIPK1. In three early‐stage clinical trials in healthy subjects and patients with AD or ALS (NCT03757325 and NCT03757351), SAR443060 distributed into the cerebrospinal fluid (CSF) after oral administration and demonstrated robust peripheral target engagement as measured by a reduction in phosphorylation of RIPK1 at serine 166 (pRIPK1) in human peripheral blood mononuclear cells compared to baseline. RIPK1 inhibition was generally safe and well‐tolerated in healthy volunteers and patients with AD or ALS. Taken together, the distribution into the CSF after oral administration, the peripheral proof‐of‐mechanism, and the safety profile of RIPK1 inhibition to date, suggest that therapeutic modulation of RIPK1 in the CNS is possible, conferring potential therapeutic promise for AD and ALS, as well as other neurodegenerative conditions. However, SAR443060 development was discontinued due to long‐term nonclinical toxicology findings, although these nonclinical toxicology signals were not observed in the short duration dosing in any of the three early‐stage clinical trials. The dose‐limiting toxicities observed for SAR443060 preclinically have not been reported for other RIPK1‐inhibitors, suggesting that these toxicities are compound‐specific (related to SAR443060) rather than RIPK1 pathway‐specific.
Objective
To investigate neurodegenerative and inflammatory biomarkers in people with amyotrophic lateral sclerosis (PALS), evaluate their predictive value for ALS progression rates, and assess their ...utility as pharmacodynamic biomarkers for monitoring treatment effects.
Methods
De‐identified, longitudinal plasma, and cerebrospinal fluid (CSF) samples from PALS (n = 108; 85 with samples from ≥2 visits) and controls without neurological disease (n = 41) were obtained from the Northeast ALS Consortium (NEALS) Biofluid Repository. Seventeen of 108 PALS had familial ALS, of whom 10 had C9orf72 mutations. Additional healthy control CSF samples (n = 35) were obtained from multiple sources. We stratified PALS into fast‐ and slow‐progression subgroups using the ALS Functional Rating Scale‐Revised change rate. We compared cytokines/chemokines and neurofilament (NF) levels between PALS and controls, among progression subgroups, and in those with C9orf72 mutations.
Results
We found significant elevations of cytokines, including MCP‐1, IL‐18, and neurofilaments (NFs), indicators of neurodegeneration, in PALS versus controls. Among PALS, these cytokines and NFs were significantly higher in fast‐progression and C9orf72 mutation subgroups versus slow progressors. Analyte levels were generally stable over time, a key feature for monitoring treatment effects. We demonstrated that CSF/plasma neurofilament light chain (NFL) levels may predict disease progression, and stratification by NFL levels can enrich for more homogeneous patient groups.
Interpretation
Longitudinal stability of cytokines and NFs in PALS support their use for monitoring responses to immunomodulatory and neuroprotective treatments. NFs also have prognostic value for fast‐progression patients and may be used to select similar patient subsets in clinical trials.
Using therapeutic antibodies that need to cross the blood-brain barrier (BBB) to treat neurological disease is a difficult challenge. We have shown that bispecific antibodies with optimized binding ...to the transferrin receptor (TfR) that target β-secretase (BACE1) can cross the BBB and reduce brain amyloid-β (Aβ) in mice. Can TfR enhance antibody uptake in the primate brain? We describe two humanized TfR/BACE1 bispecific antibody variants. Using a human TfR knock-in mouse, we observed that anti-TfR/BACE1 antibodies could cross the BBB and reduce brain Aβ in a TfR affinity-dependent fashion. Intravenous dosing of monkeys with anti-TfR/BACE1 antibodies also reduced Aβ both in cerebral spinal fluid and in brain tissue, and the degree of reduction correlated with the brain concentration of anti-TfR/BACE1 antibody. These results demonstrate that the TfR bispecific antibody platform can robustly and safely deliver therapeutic antibody across the BBB in the primate brain.
Impaired social interaction is a defining feature of autism spectrum disorder, a neurodevelopmental disorder that shows a strong male preponderance in prevalence. Studies have identified neural ...circuits, neuromodulators and genetic factors involved in social behaviors, but mechanistic understanding of gender-specific social deficits is lacking. We report that deletion of the caspase-3 gene, encoding a protease with functions in apoptosis and neural plasticity, alters specific social behaviors in male mice, while leaving females unaffected. Casp3(-/-) mice showed normal behavioral responses to olfactory cues from food, neutral chemical and biological sources. Both Casp3(-/-) males and females displayed robust social exploration, sociability, recognition and preference for an enclosed novel mouse in the three-chamber test. However, Casp3(-/-) males showed significantly reduced social interaction behaviors when exposed to a freely moving novel mouse, including decreased interaction time and diminished mounting. Thus caspase-3 is essential for a subset of social behaviors, but despite similar hyper-locomotion in both sexes, only male Casp3(-/-) mice exhibited social interaction deficits, which is interesting given the male bias of autism.
Background and Purpose
The potential for therapeutic antibody treatment of neurological diseases is limited by poor penetration across the blood–brain barrier. I.c.v. delivery is a promising route to ...the brain; however, it is unclear how efficiently antibodies delivered i.c.v. penetrate the cerebrospinal spinal fluid (CSF)‐brain barrier and distribute throughout the brain parenchyma.
Experimental Approach
We evaluated the pharmacokinetics and pharmacodynamics of an inhibitory monoclonal antibody against β‐secretase 1 (anti‐BACE1) following continuous infusion into the left lateral ventricle of healthy adult cynomolgus monkeys.
Key Results
Animals infused with anti‐BACE1 i.c.v. showed a robust and sustained reduction (~70%) of CSF amyloid‐β (Aβ) peptides. Antibody distribution was near uniform across the brain parenchyma, ranging from 20 to 40 nM, resulting in a ~50% reduction of Aβ in the cortical parenchyma. In contrast, animals administered anti‐BACE1 i.v. showed no significant change in CSF or cortical Aβ levels and had a low (~0.6 nM) antibody concentration in the brain.
Conclusion and Implications
I.c.v. administration of anti‐BACE1 resulted in enhanced BACE1 target engagement and inhibition, with a corresponding dramatic reduction in CNS Aβ concentrations, due to enhanced brain exposure to antibody.
Microglia and other tissue-resident macrophages within the central nervous system (CNS) have essential roles in neural development, inflammation and homeostasis. However, the molecular pathways ...underlying their development and function remain poorly understood. Here we report that mice deficient in NRROS, a myeloid-expressed transmembrane protein in the endoplasmic reticulum, develop spontaneous neurological disorders. NRROS-deficient (Nrros
) mice show defects in motor functions and die before 6 months of age. Nrros
mice display astrogliosis and lack normal CD11b
CD45
microglia, but they show no detectable demyelination or neuronal loss. Instead, perivascular macrophage-like myeloid cells populate the Nrros
CNS. Cx3cr1-driven deletion of Nrros shows its crucial role in microglial establishment during early embryonic stages. NRROS is required for normal expression of Sall1 and other microglial genes that are important for microglial development and function. Our study reveals a NRROS-mediated pathway that controls CNS-resident macrophage development and affects neurological function.
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