Abstract
Background
The most common dementia worldwide, Alzheimer’s disease is often diagnosed via biomarkers in cerebrospinal fluid, including reduced levels of Aβ1-42, and increases in total tau and phosphorylated tau-181. Here we describe results of a Phase 2a study of a promising new drug candidate that significantly reversed all measured biomarkers of Alzheimer’s disease, neurodegeneration and neuroinflammation. PTI-125 is an oral small molecule drug candidate that binds and reverses an altered conformation of the scaffolding protein filamin A found in Alzheimer’s disease brain. Altered filamin A links to the α7-nicotinic acetylcholine receptor to allow Aβ42’s toxic signaling through this receptor to hyperphosphorylate tau. Altered filamin A also links to toll-like receptor 4 to enable Aβ-induced persistent activation of this receptor and inflammatory cytokine release. Restoring the native shape of filamin A prevents or reverses filamin A’s linkages to the α7-nicotinic acetylcholine receptor and tolllike receptor 4, thereby blocking Aβ42’s activation of these receptors. The result is reduced tau hyperphosphorylation and neuroinflammation, with multiple functional improvements demonstrated in transgenic mice and postmortem Alzheimer’s disease brain.
Objectives
Safety, pharmacokinetics, and cerebrospinal fluid and plasma biomarkers were assessed following treatment with PTI-125 for 28 days. Target engagement and mechanism of action were assessed in patient lymphocytes by measuring 1) the reversal of filamin A’s altered conformation, 2) linkages of filamin A with α7-nicotinic acetylcholine receptor or tolllike receptor 4, and 3) levels of Aβ42 bound to α7-nicotinic acetylcholine receptor or CD14, the co-receptor for toll-like receptor 4.
Design
This was a first-in-patient, open-label Phase 2a safety, pharmacokinetics and biomarker study.
Setting
Five clinical trial sites in the U.S. under an Investigational New Drug application.
Participants
This study included 13 mild-to-moderate Alzheimer’s disease patients, age 50–85, Mini Mental State Exam ≥16 and ≤24 with a cerebrospinal fluid total tau/Aβ42 ratio ≥0.30.
Intervention
PTI-125 oral tablets (100 mg) were administered twice daily for 28 consecutive days.
Measurements
Safety was assessed by electrocardiograms, clinical laboratory analyses and adverse event monitoring. Plasma levels of PTI-125 were measured in blood samples taken over 12 h after the first and last doses; cerebrospinal fluid levels were measured after the last dose. Commercial enzyme linked immunosorbent assays assessed levels of biomarkers of Alzheimer’s disease in cerebrospinal fluid and plasma before and after treatment with PTI-125. The study measured biomarkers of pathology (pT181 tau, total tau and Aβ42), neurodegeneration (neurofilament light chain and neurogranin) and neuroinflammation (YKL-40, interleukin-6, interleukin-1β and tumor necrosis factor α). Plasma levels of phosphorylated and nitrated tau were assessed by immunoprecipitation of tau followed by immunoblotting of three different phosphoepitopes elevated in AD (pT181-tau, pS202-tau and pT231-tau) and nY29-tau. Changes in conformation of filamin A in lymphocytes were measured by isoelectric focusing point. Filamin A linkages to α7-nicotinic acetylcholine receptor and toll-like receptor 4 were assessed by immunoblot detection of α7-nicotinic acetylcholine receptor and toll-like receptor 4 in anti-filamin A immunoprecipitates from lymphocytes. Aβ42 complexed with α7-nicotinic acetylcholine receptor or CD14 in lymphocytes was also measured by co-immunoprecipitation. The trial did not measure cognition.
Results
Consistent with the drug’s mechanism of action and preclinical data, PTI-125 reduced cerebrospinal fluid biomarkers of Alzheimer’s disease pathology, neurodegeneration and neuroinflammation from baseline to Day 28. All patients showed a biomarker response to PTI-125. Total tau, neurogranin, and neurofilament light chain decreased by 20%, 32% and 22%, respectively. Phospho-tau (pT181) decreased 34%, evidence that PTI-125 suppresses tau hyperphosphorylation induced by Aβ42’s signaling through α7-nicotinic acetylcholine receptor. Cerebrospinal fluid biomarkers of neuroinflammation (YKL-40 and inflammatory cytokines) decreased by 5–14%. Biomarker effects were similar in plasma. Aβ42 increased slightly - a desirable result because low Aβ42 indicates Alzheimer’s disease. This increase is consistent with PTI-125’s 1,000-fold reduction of Aβ42’s femtomolar binding affinity to α7-nicotinic acetylcholine receptor. Biomarker reductions were at least p ≤ 0.001 by paired t test. Target engagement was shown in lymphocytes by a shift in filamin A’s conformation from aberrant to native: 93% was aberrant on Day 1 vs. 40% on Day 28. As a result, filamin A linkages with α7-nicotinic acetylcholine receptor and toll-like receptor 4, and Aβ42 complexes with α7-nicotinic acetylcholine receptor and CD14, were all significantly reduced by PTI-125. PTI-125 was safe and well-tolerated in all patients. Plasma half-life was 4.5 h and approximately 30% drug accumulation was observed on Day 28 vs. Day 1.
Conclusions
PTI-125 significantly reduced biomarkers of Alzheimer’s disease pathology, neurodegeneration, and neuroinflammation in both cerebrospinal fluid and plasma. All patients responded to treatment. The magnitude and consistency of reductions in established, objective biomarkers imply that PTI-125 treatment counteracted disease processes and reduced the rate of neurodegeneration. Based on encouraging biomarker data and safety profile, approximately 60 patients with mild-to-moderate AD are currently being enrolled in a Phase 2b randomized, placebo-controlled confirmatory study to assess the safety, tolerability and efficacy of PTI-125.
Similar content being viewed by others
References
World Alzheimer Report 2018. 2018: Alzheimer’s Disease International, London.
Burns, L.H. and H.-Y. Wang, Altered filamin A enables amyloid beta-induced tau hyperphosphorylation and neuroinflammation in Alzheimer’s disease. Neuroimmunol Neuroinflammation, 2017. 4: p. 263–71.
Wang, H.-Y., et al., PTI-125 binds and reverses an altered conformation of filamin A to reduce Alzheimer’s disease pathogenesis. Neurobiol Aging, 2017. 55: p. 99–114.
Wang, H.-Y., et al., Reducing amyloid-related Alzheimer’s disease pathogenesis by a small molecule targeting filamin A. J Neurosci, 2012. 32: p. 9773–84.
Nakamura, F., T. Stossel, and J. Hartwig, The filamins: organizers of cell structure and function. Cell Adh Migr, 2011. 5: p. 160–9.
Wang, H.-Y., M. Frankfurt, and L.H. Burns, High-affinity naloxone binding to filamin A prevents mu opioid receptor - Gs coupling underlying opioid tolerance and dependence. PLoS One, 2008. 3(2): p. e1554.
Wang, H.-Y., et al., β-Amyloid1-42 binds to α7 nicotinic acetylcholine receptor with high affinity:Implication for Alzheimer’s disease pathology. J Biol Chem, 2000. 275: p. 5626–5632.
Wang, H.-Y., et al., α7 nicotinic acetylcholine receptors mediate β-amyloid peptide-induced tau protein phosphorylation. J Biol Chem, 2003. 278: p. 31547–31553.
Dineley, K., et al., β-Amyloid peptide activates α7 nicotinic acetylcholine receptors expressed in xenopus oocytes. J Biol Chem, 2002. 227: p. 25056–61.
Nagele, R., et al., Accumulation of beta-amyloid1-42 in neurons is facilitated by the alpha7 nicotinic acetylcholine receptor in Alzheimer’s disease. Neuroscience 2002. 110: p. 199–211.
Wang, H.-Y., et al., Amyloid peptide Aβ1-42 binds selectively and with picomolar affinity to α7 nicotinic acetylcholine receptors. J Neurochem, 2000. 75: p. 1155–1161.
Gambuzza, M., et al., Toll-like receptors in Alzheimer’s disease: a therapeutic perspective. CNS Neurol Disord Drug Targets, 2014. 13: p. 1542–58.
Reed-Geaghan, E., et al., CD14 and Toll-like receptors 2 and 4 are required for fibrillar Aβ-stimulated microglial activation. J Neurosci, 2009. 29: p. 11982–11992.
Hansson, O., et al., CSF biomarkers of Alzheimer’s disease concord with amyloid-b PETand predict clinical progression: A study of fully automated immunoassays in BioFINDER and ADNI cohorts. Alzheimer’s Dement, 2018. 14: p. 1470–1481.
Olsson, B., et al., CSF and blood biomarkers for the diagnosis of Alzheimer’s disease: a systematic review and meta-analysis. Lancet Neurol, 2016. 15: p. 673–684.
Bacioglu, M., et al., Neurofilament light chain in blood and CSF as marker of disease progression in mouse models and in neurodegenerative diseases. Neuron, 2016. 91: p. 1–11.
Hampel, H., et al., Alzheimer’s disease biomarker-guided diagnostic workflow using the added value of six combined cerebrospinal fluid candidates: Aβ1-42, total-tau, phosphorylated-tau, NFL, neurogranin, and YKL-40. Alzheimer’s & Dementia, 2018. 14: p. 492–501.
Hellwig, K., et al., Neurogranin and YKL-40: Independent markers of synaptic degeneration and neuroinflammation in Alzheimer’s disease. Alzheimers Res Ther, 2015. 7: p. 74.
Lista, S. and H. Hampel, Synaptic degeneration and neurogranin in the pathophysiology of Alzheimer’s disease. Expert Rev Neurother 2017. 17: p. 47–57.
Llorens, F., et al., YKL-40 in the brain and cerebrospinal fluid of neurodegenerative dementias. Mol Neurodegener, 2017. 12: p. 83.
Nordengen, K., et al., Glial activation and inflammation along the Alzheimer’s disease continuum. J Neuroinflammation, 2019. 16: p. 46.
Wang, H., et al., Increased Aβ42-α7-like nicotinic acetylcholine receptor complex level in lymphocytes is associated with apolipoprotein E4-driven Alzheimer’s disease pathogenesis. Alzheimers Res Ther., 2017. 9: p. 54.
Wang, H.-Y., et al., S 24795 limits β-amyloid - α7 nicotinic receptor interaction and reduces Alzheimer’s disease-like pathologies. Biol Psychiatry 2010; 67: 522–530. Biol Psychiatry, 2010. 67: p. 522–530.
Hayashi, K. and A. Altman, Filamin A Is Required for T Cell Activation Mediated by Protein Kinase C-θ. J Immunol, 2006. 177: p. 1721–1728.
Wang, H.-Y., et al., Dissociating beta-amyloid from alpha 7 nicotinic acetylcholine receptor by a novel therapeutic agent, S 24795, normalizes alpha 7 nicotinic acetylcholine and NMDA receptor function in Alzheimer’s disease brain. J Neurosci, 2009. 35: p. 10961–73.
Nathan, P., et al., Association between CSF biomarkers, hippocampal volume and cognitive function in patients with amnestic mild cognitive impairment (MCI). Neurobiol Aging, 2017. 17: p. 1–10.
Swanson, C. Effect of BAN2401 on underlying AD pathophysiology. in CTAD. 2018. Barcelona.
US FDA, Early Alzheimer’s Disease: Developing Drugs for Treatment, Guidance for Industry 2018.
Acknowledgements
We sincerely thank NIA for their support of our work in Alzheimer’s disease. We thank the clinical investigators and patients who have participated in the clinical program for PTI-125. We thank consultants Chuck Davis for statistics on ELISA biomarkers and Jeff Stark for PK analyses.
Funding
Funding: This trial was funded by grant award AG060878 from the National Institute on Aging at NIH.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest: LHB, CAC, RB and NF are employees of Cassava Sciences, Inc. HYW and MRM are science advisors to Cassava Sciences, Inc. ELB and BN are employees of IMIC, Inc., an independent clinical site that participated in this study.
Ethical standards: All participants and their caregivers provided written informed consent. The protocol, informed consent forms and clinical sites were all approved by Advarra IRB.
Additional information
Role of the sponsor: Cassava Sciences, Inc. provided all drug supply and material support for this clinical research, designed the study in consultation with its advisors and monitored the conduct of the study and data collection. Biomarker assays were conducted blind to treatment day by HWY and his lab at CUNY Medical school. LHB assisted in the interpretation of the data and wrote the manuscript together with RB and HWY.
Rights and permissions
About this article
Cite this article
Wang, HY., Pei, Z., Lee, KC. et al. PTI-125 Reduces Biomarkers of Alzheimer’s Disease in Patients. J Prev Alzheimers Dis 7, 256–264 (2020). https://doi.org/10.14283/jpad.2020.6
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.14283/jpad.2020.6