Efficacy and Safety of a Brain-Penetrant Biologic TNF-α Inhibitor in Aged APP/PS1 Mice

Tumor necrosis factor alpha (TNF-α) plays a vital role in Alzheimer’s disease (AD) pathology, and TNF-α inhibitors (TNFIs) modulate AD pathology. We fused the TNF-α receptor (TNFR), a biologic TNFI that sequesters TNF-α, to a transferrin receptor antibody (TfRMAb) to deliver the TNFI into the brain across the blood–brain barrier (BBB). TfRMAb-TNFR was protective in 6-month-old transgenic APP/PS1 mice in our previous work. However, the effects and safety following delayed chronic TfRMAb-TNFR treatment are unknown. Herein, we initiated the treatment when the male APP/PS1 mice were 10.7 months old (delayed treatment). Mice were injected intraperitoneally with saline, TfRMAb-TNFR, etanercept (non-BBB-penetrating TNFI), or TfRMAb for ten weeks. Biologic TNFIs did not alter hematology indices or tissue iron homeostasis; however, TfRMAb altered hematology indices, increased splenic iron transporter expression, and increased spleen and liver iron. TfRMAb-TNFR and etanercept reduced brain insoluble-amyloid beta (Aβ) 1-42, soluble-oligomeric Aβ, and microgliosis; however, only TfRMAb-TNFR reduced Aβ peptides, Thioflavin-S-positive Aβ plaques, and insoluble-oligomeric Aβ and increased plaque-associated phagocytic microglia. Accordingly, TfRMAb-TNFR improved spatial reference memory and increased BBB-tight junction protein expression, whereas etanercept did not. Overall, despite delayed treatment, TfRMAb-TNFR resulted in a better therapeutic response than etanercept without any TfRMAb-related hematology- or iron-dysregulation in aged APP/PS1 mice

Biologic TNF-α Inhibitors Reduce Microgliosis, Neuronal Loss, and Tau Phosphorylation in a Transgenic Mouse Model of Tauopathy

Background Tumor necrosis factor-α (TNF-α) plays a central role in Alzheimer’s disease (AD) pathology, making biologic TNF-α inhibitors (TNFIs), including etanercept, viable therapeutics for AD. The protective effects of biologic TNFIs on AD hallmark pathology (Aβ deposition and tau pathology) have been demonstrated. However, the effects of biologic TNFIs on Aβ-independent tau pathology have not been reported. Existing biologic TNFIs do not cross the blood–brain barrier (BBB), therefore we engineered a BBB-penetrating biologic TNFI by fusing the extracellular domain of the type-II human TNF-α receptor (TNFR) to a transferrin receptor antibody (TfRMAb) that ferries the TNFR into the brain via receptor-mediated transcytosis. The present study aimed to investigate the effects of TfRMAb-TNFR (BBB-penetrating TNFI) and etanercept (non-BBB-penetrating TNFI) in the PS19 transgenic mouse model of tauopathy. Methods Six-month-old male and female PS19 mice were injected intraperitoneally with saline (n = 12), TfRMAb-TNFR (1.75 mg/kg, n = 10) or etanercept (0.875 mg/kg, equimolar dose of TNFR, n = 10) 3 days/week for 8 weeks. Age-matched littermate wild-type mice served as additional controls. Blood was collected at baseline and 8 weeks for a complete blood count. Locomotion hyperactivity was assessed by the open-field paradigm. Brains were examined for phosphorylated tau lesions (Ser202, Thr205), microgliosis, and neuronal health. The plasma pharmacokinetics were evaluated following a single intraperitoneal injection of 0.875 mg/kg etanercept or 1.75 mg/kg TfRMAb-TNFR or 1.75 mg/kg chronic TfRMAb-TNFR dosing for 4 weeks. Results Etanercept significantly reduced phosphorylated tau and microgliosis in the PS19 mouse brains of both sexes, while TfRMAb-TNFR significantly reduced these parameters in the female PS19 mice. Both TfRMAb-TNFR and etanercept treatment improved neuronal health by significantly increasing PSD95 expression and attenuating hippocampal neuron loss in the PS19 mice. The locomotion hyperactivity in the male PS19 mice was suppressed by chronic etanercept treatment. Equimolar dosing resulted in eightfold lower plasma exposure of the TfRMAb-TNFR compared with etanercept. The hematological profiles remained largely stable following chronic biologic TNFI dosing except for a significant increase in platelets with etanercept. Conclusion Both TfRMAb-TNFR (BBB-penetrating) and non-BBB-penetrating (etanercept) biologic TNFIs showed therapeutic effects in the PS19 mouse model of tauopathy

The Effects of a Blood–Brain Barrier Penetrating Erythropoietin in a Mouse Model of Tauopathy

Erythropoietin (EPO), a hematopoietic neurotrophin, is a potential therapeutic for Alzheimer’s disease (AD) but has limited blood–brain barrier (BBB) permeability. EPO fused to a chimeric transferrin receptor monoclonal antibody (cTfRMAb) enters the brain via TfR-mediated transcytosis across the BBB. We previously showed that cTfRMAb-EPO is protective in a mouse model of amyloidosis, but its effects on tauopathy are not known. Given that amyloid and tau pathology are characteristics of AD, the effects of cTfRMAb-EPO were studied in a tauopathy mouse model (PS19). Six-month-old PS19 mice were injected intraperitoneally with either saline (PS19-Saline; n = 9) or cTfRMAb-EPO (PS19-cTfRMAb-EPO, 10 mg/kg; n = 10); every two or three days on alternate weeks for 8 weeks. Age-matched, saline-treated, wildtype littermates (WT-Saline; n = 12) were injected using the same protocol. After 8 weeks, locomotion, hyperactivity, and anxiety were assessed via the open-field test, and brains were harvested and sectioned. Cerebral cortex, hippocampus, amygdala, and entorhinal cortex sections were analyzed for phospho-tau (AT8) and microgliosis (Iba1). Hippocampal cellular density (H&E) was also assessed. PS19-Saline mice were hyperactive and less anxious compared to WT-Saline mice, and these behavioral phenotypes were significantly reduced in the PS19-cTfRMAb-EPO mice compared to the PS19-Saline mice. cTfRMAb-EPO significantly reduced AT8 load by ≥50% in all of the brain regions analyzed and microgliosis in the entorhinal cortex and amygdala compared to the PS19-Saline mice. Hippocampal pyramidal and granule cell layer density did not differ significantly between the PS19-cTfRMAb-EPO and PS19-Saline mice. This proof-of-concept study demonstrates the therapeutic effects of the BBB-penetrating cTfRMAb-EPO in PS19 mice

Efficacy and Safety of a Brain-Penetrant Biologic TNF-α Inhibitor in Aged APP/PS1 Mice

Tumor necrosis factor alpha (TNF-α) plays a vital role in Alzheimer’s disease (AD) pathology, and TNF-α inhibitors (TNFIs) modulate AD pathology. We fused the TNF-α receptor (TNFR), a biologic TNFI that sequesters TNF-α, to a transferrin receptor antibody (TfRMAb) to deliver the TNFI into the brain across the blood–brain barrier (BBB). TfRMAb-TNFR was protective in 6-month-old transgenic APP/PS1 mice in our previous work. However, the effects and safety following delayed chronic TfRMAb-TNFR treatment are unknown. Herein, we initiated the treatment when the male APP/PS1 mice were 10.7 months old (delayed treatment). Mice were injected intraperitoneally with saline, TfRMAb-TNFR, etanercept (non-BBB-penetrating TNFI), or TfRMAb for ten weeks. Biologic TNFIs did not alter hematology indices or tissue iron homeostasis; however, TfRMAb altered hematology indices, increased splenic iron transporter expression, and increased spleen and liver iron. TfRMAb-TNFR and etanercept reduced brain insoluble-amyloid beta (Aβ) 1-42, soluble-oligomeric Aβ, and microgliosis; however, only TfRMAb-TNFR reduced Aβ peptides, Thioflavin-S-positive Aβ plaques, and insoluble-oligomeric Aβ and increased plaque-associated phagocytic microglia. Accordingly, TfRMAb-TNFR improved spatial reference memory and increased BBB-tight junction protein expression, whereas etanercept did not. Overall, despite delayed treatment, TfRMAb-TNFR resulted in a better therapeutic response than etanercept without any TfRMAb-related hematology- or iron-dysregulation in aged APP/PS1 mice