Therapy Type: Small Molecule (timeline)
Target Type: Amyloid-Related (timeline)
Condition(s): Alzheimer's Disease
U.S. FDA Status: Alzheimer's Disease (Phase 2)
Company: Cassava Sciences
PTI-125 binds to filamin, a ubiquitous scaffolding protein and regulator of the actin cytoskeleton. Filamin appears to stabilize the high-affinity interaction of soluble Aβ42 and the α7 nicotinic acetylcholine receptor (α7nAChR), which has been reported to trigger tau phosphorylation and synaptic dysfunction in some experimental systems (Wang et al., 2000; Wang et al., 2003; Snyder et al., 2005).
Preclinical studies suggest that PTI-125 prevents and reverses the binding of Aβ42 to α7nAChR. In one, daily infusions of human synthetic Aβ42 into mouse cerebral ventricles resulted in association of Aβ42 and filamin with α7 receptors in the hippocampus and prefrontal cortex. Concomitant intraperitoneal PTI-125 injections prevented this association, reduced tau phosphorylation and amyloid deposition, and normalized signaling through the α7, NDMA, and insulin receptors. PTI-125 reportedly tamped down Aβ-induced inflammatory cytokine release by blocking filamin recruitment to toll-like receptor 4. When applied to human AD postmortem brain tissue, PTI-125 caused filamin and Aβ42 to dissociated from the α7 receptor (July 2012 news).
Two months of oral PTI-125 in 3xTg AD mice reportedly reduced tau hyperphosphorylation, amyloid and tau deposition, and neuroinflammation, and restored synaptic function, nesting behavior, and spatial and working memory relative to untreated mice. The study proposed that Aβ42 induces a conformational change in filamin, which would promote its association with the α7 and toll-like receptors, enabling Aβ42 toxicity and inflammation. PTI-125 was said to preferentially bind altered filamin and normalize its conformation (Wang et al., 2017).
Cassava Sciences started with a Phase 1 safety study of 50, 100, or 200 mg of PIT-125 in 24 healthy adults in 2017 and, in March 2019, proceeded to run an NIH-funded Phase 2a trial in patients with mild to moderate AD. This open-label, multicenter safety, pharmacokinetics, and biomarker study was to enroll 12 patients with MMSE scores between 16 and 24 and a CSF total tau/Aβ42 ratio of 0.30 or higher. Participants took 100 mg PTI-125 capsules twice daily for 28 days. Primary outcomes were pharmacokinetic measures, secondary ones were CSF biomarkers of Alzheimer’s pathology, neurodegeneration, and neuroinflammation. The study measured levels of PTI-125DX, an experimental diagnostic biomarker to indicate altered filamin in blood.
In a September 2019 press release, Cassava claimed that drug treatment significantly decreased CSF total and phosphorylated tau, neurofilament light, neurogranin, YKL-40, Il-6, Il-1β, and TNFα, consistent with drug effects countering neurodegeneration and -inflammation. The ratio of phosphorylated tau to Aβ42 apparently improved. The trial did not measure cognition.
Also in September 2019, the company began a randomized Phase 2b study (see press release). This multicenter study will compare 100 or 50 mg PTI-125 to placebo, dosed twice daily for 28 days in 60 participants with mild to moderate AD. The primary endpoint is change in CSF phosphorylated tau, neurofilament light chain, neurogranin, total tau, YKL-40 and Aβ42; secondary outcomes include cognitive assessments and plasma biomarkers. This NIH-funded trial will run through April 2020.
For details, see clinicaltrials.gov.
Last Updated: 02 Oct 2019
Research Models Citations
- Wang HY, Lee DH, D'Andrea MR, Peterson PA, Shank RP, Reitz AB. beta-Amyloid(1-42) binds to alpha7 nicotinic acetylcholine receptor with high affinity. Implications for Alzheimer's disease pathology. J Biol Chem. 2000 Feb 25;275(8):5626-32. PubMed.
- Wang HY, Li W, Benedetti NJ, Lee DH. Alpha 7 nicotinic acetylcholine receptors mediate beta-amyloid peptide-induced tau protein phosphorylation. J Biol Chem. 2003 Aug 22;278(34):31547-53. PubMed.
- Snyder EM, Nong Y, Almeida CG, Paul S, Moran T, Choi EY, Nairn AC, Salter MW, Lombroso PJ, Gouras GK, Greengard P. Regulation of NMDA receptor trafficking by amyloid-beta. Nat Neurosci. 2005 Aug;8(8):1051-8. PubMed.
- Wang HY, Lee KC, Pei Z, Khan A, Bakshi K, Burns LH. PTI-125 binds and reverses an altered conformation of filamin A to reduce Alzheimer's disease pathogenesis. Neurobiol Aging. 2017 Jul;55:99-114. Epub 2017 Mar 31 PubMed.
- Burns LM, Wang HY. Altered filamin A enables amyloid beta induced tau hyperphosphorylation and neuroinflammation in Alzheimer’s disease. Neuroimmunol Neuroinflammation 2017;4:263-71.