Abstract
Background: Edonerpic (T-817; 1-{3-[2-(1-benzothiophen-5-yl)ethoxy]propyl}azetidin-3-ol maleate, Toyama Chemical, Ltd) protects against Aβ42-induced neurotoxicity and memory deficits, promotes cortical and hippocampal neuron outgrowth, and preserves hippocampal synapses and spatial memory in tau transgenic mice, possibly via sigma receptor activation. The primary objective was to assess the efficacy and safety of T-817 in Alzheimer's disease (NCT 02079909). Methods: Outpatients, ages 55 to 85, meeting criteria for probable AD, MMSE 12–22, taking stable doses of donepezil or rivastigmine, taking or not memantine, were randomly assigned (1:1:1) to placebo, 224mg, or 448mg of T-817 once/day for 52 weeks. The primary outcomes were the ADAScog and ADCS-CGIC (CIBIC+) at week 52. Secondary outcomes were the MMSE, ADCS-ADL, FAQ, and NPI at week 52; and the outcomes at weeks 12, 24, 36, and 44. Biomarkers were MRI whole brain, lateral ventricular, and hippocampal volumes; and CSF Aβ40, 42, t-tau, and p-tau; and population pharmacokinetics. Results: 140 of 158 (88.6%) participants assigned to placebo, 117 of 166 (70.5%) to 224mg, and 120 of 158 (75.9%) to 448mg completed the trial, conducted from June 2014 to December 2016 at 52 US sites. LS mean ADAScog change was 7.9, 7.5, and 7.1 for the placebo, 224mg, and 448mg groups, respectively; difference, placebo vs. 448mg, -0.8 (95% CI: -2.8, 1.1; P=0.3919). Mean ADCS-CGIC scores were 5.2, 5.2, and 5.3; difference, 0.04 (95% CI: -0.19, 0.26; P=0.7588). There were no significant differences for the secondary outcomes. P-tau was nominally significantly lower in the 448mg group vs. placebo (n=24 and N=18, P=0.0338). Hippocampal volumes decreased less in the 224mg group than placebo (n=79 and N=89; -0.27 vs. -0.39 mL, P=0.0106) but not in the 448mg group (n=76; -0.31 vs. -0.39 mL, P=0.0996). 4.4%, 13.9% and 14.6% discontinued because of AEs, placebo, 224mg, and 448mg groups, respectively. Most frequent AEs ≥ 5%: diarrhea (12.7%, 20.5%, 31.0%), nausea (3.8%, 7.8%, 5.7%); infections, injuries, falls, agitation and anxiety were more common with placebo. Conclusions: T-817 appeared safe, tolerable, with expected GI symptoms occurring early, but without evidence for clinical effect in the protocol-specified primary and secondary outcomes. Decreased CSF p-tau and hippocampal volumes require confirmation.