Preclinical in vivo longitudinal assessment of KG207-M as a disease-modifying Alzheimer’s disease therapeutic

Abstract

In vivo biomarker abnormalities provide measures to monitor therapeutic interventions targeting amyloid-β pathology as well as its effects on downstream processes associated with Alzheimer’s disease pathophysiology. Here, we applied an in vivo longitudinal study design combined with imaging and cerebrospinal fluid biomarkers, mirroring those used in human clinical trials to assess the efficacy of a novel brain-penetrating anti-amyloid fusion protein treatment in the McGill-R-Thy1-APP transgenic rat model. The bi-functional fusion protein consisted of a blood-brain barrier crossing single domain antibody (FC5) fused to an amyloid-β oligomer-binding peptide (ABP) via Fc fragment of mouse IgG (FC5-mFc2a-ABP). A five-week treatment with FC5-mFc2a-ABP (loading dose of 30 mg/Kg/iv followed by 15 mg/Kg/week/iv for four weeks) substantially reduced brain amyloid-β levels as measured by positron emission tomography and increased the cerebrospinal fluid amyloid-β42/40 ratio. In addition, the 5-week treatment rectified the cerebrospinal fluid neurofilament light chain concentrations, resting-state functional connectivity, and hippocampal atrophy measured using magnetic resonance imaging. Finally, FC5-mFc2a-ABP (referred to as KG207-M) treatment did not induce amyloid-related imaging abnormalities such as microhemorrhage. Together, this study demonstrates the translational values of the designed preclinical studies for the assessment of novel therapies based on the clinical biomarkers providing tangible metrics for designing early-stage clinical trials.

Pharmacokinetics and Pharmacodynamic Effect of a Blood-Brain Barrier-Crossing Fusion Protein Therapeutic for Alzheimer’s Disease in Rat and Dog

“…While the finding of lowered CSF Aβ in this study cannot be directly extrapolated to the brain, it is worth noting that reduced CSF Aβ observed in transgenic rats after KG207-M treatment was accompanied by significantly diminished brain amyloid (17). The relationship between the biomarker and drug concentration aligns with a typical indirect response model with stimulation of Aβ loss by drug concentration.…”

“…1). In the current and our previous studies with KG207 (17), the C max in the CSF was consistently delayed by approximately 24 h compared to C max in the serum. Direct measurements of FC5-fusion protein(s) in the rat brain (10,13) and KG207 in both total brain homogenates and vessel-depleted brain parenchyma in the mouse (Supplementary Figs.…”

“…5, there is an inverse relationship between the apparent CSF KG207-H exposure (CSF KG207-H AUC 0-168 ) and the Aβ level (CSF Aβ AUC 0-168 ) suggesting target engagement by KG207-H within CNS. The wildtype rat used here, with endogenous expression of Aβ and no Aβ pathology, showed a high level of variability in CSF Aβ levels in comparison to transgenic rats overexpressing mutant APP (17). Similarly, substantial inter-individual differences in CSF Aβ levels in Beagle dogs have been reported, even in young to middle-aged animals (41).…”

“…For absolute quantification, calibration curves were prepared by spiking KG207-H in the appropriate matrix from naïve animals (either dog or rat plasma at 0 -10 nmol/mL, or dog or rat CSF at 0 -20 nM) and similarly digested. All digests were analyzed on nanoAcquity UPLC (Waters, Milford, MA) coupled to ESI LTQ XL ETD mass spectrometer (ThermoFisher, Waltham, MA) in selected reaction monitoring (SRM) mode as previously described (17). The SRM method included multiplexed quantification of three peptides unique to KG207-H (FC5 ITWGGDNTFYSNSVK; hFc TTPPVLDSDGSFFLYSK; ABP + linker SLSLSPGTG GGG SGGGGSGTFGTGGASAQASLASK), one host Aβ peptide (LVFFAEDVGSNK), and one host albumin peptide (SLHTLFGDK).…”

“…In aged transgenic McGill-R-Thy1-APP rats expressing human APP 751 with familial AD mutations, 5 week treatment with KG207-M markedly reduced brain Aβ levels measured by positron emission tomography, reversed hippocampal atrophy, and improved resting state functional connectivity (17). CSF concentration of KG207-M over time was negatively correlated with levels of CSF Aβ quantified by Selected Reaction Monitoring (SRM) mass spectrometry.…”