Blarcamesine for the treatment of Early Alzheimer's Disease: results from the ANAVEX2-73-AD-004 Phase IIB/III trial

Background: There are no approved oral disease-modifying treatments for Alzheimer's disease (AD). Objectives: The objective of this study was to assess efficacy and safety of blarcamesine (ANAVEX®2-73), an orally available small-molecule activator of the sigma-1 receptor (SIGMAR1) in early AD through restoration of cellular homeostasis including autophagy enhancement. Design: ANAVEX2-73-AD-004 was a randomized, double-blind, placebo-controlled, 48-week Phase IIb/III trial. Setting: Multicenter - 52 medical research centers/hospitals in 5 countries. Intervention: 508 participants with early AD (Stage 3) were randomized to receive either blarcamesine (n = 338) in medium dose group 30 mg or in high dose group 50 mg or placebo (n = 170) oral capsules once daily for 48 weeks. Participants in these groups were offered to enroll into the open-label-extension study ATTENTION-AD, which completed June 2024, ClinicalTrials.gov Identifier NCT04314934. Measurements: The co-primary cognitive and functional outcomes were assessed as change in ADAS-Cog13 and ADCS-ADL from baseline to 48 weeks. The outcomes include the secondary outcome CDR-SB and biomarkers from the A/T/N spectrum, plasma Aβ42/40-ratio and global brain volume changes measured by MRI. All clinical endpoints were analyzed using mixed model for repeated measures (MMRM), plasma biomarker measurements were analyzed by Welch's t-test, and volumetric MRI scans were analyzed by general linear model. Results: Among 462 randomized participants in the intent-to-treat population (mean age, 73.7 years; 225 [48.7%] women), 338 (73.2%) completed the trial. The co-primary outcome was met under the multiplicity control rule, since the differences in the least-squares mean (LSM) change from baseline to 48 weeks between the prespecified blarcamesine and placebo groups for ADAS-Cog13 was significant at a level of P < 0.025 and for CDR-SB was significant at a level of P < 0.025, while ADCS-ADL did not reach significance at Week 48 (ADAS-Cog13 difference of -2.027 [95% CI -3.522 to -0.533]; P = 0.008; CDR-SB difference of -0.483 [95% CI -0.853 to -0.114]; P = 0.010; ADCS-ADL difference of 0.775 [95%CI -0.874 to 2.423]; P = 0.357). Plasma Aβ42/40-ratio increased significantly with blarcamesine group vs. placebo, (P = 0.048) and whole brain volume loss was significantly decreased (P = 0.002). Participants in the full safety population with ≥1 serious treatment-emergent adverse events (TEAEs) occurred in 56 participants (16.7%) in the blarcamesine and 17 (10.1%) in the placebo group. Common TEAEs included dizziness, which was transient and mostly mild to moderate in severity. One death in the blarcamesine group and 1 in the placebo group were both not considered treatment related. Conclusions: Blarcamesine, demonstrating a safety profile with no associated neuroimaging adverse events, significantly slowed clinical progression by 36.3% at 48 weeks with blarcamesine group as well as the individual 30 mg (by 34.6%) and 50 mg (by 38.5%) blarcamesine groups vs. placebo on the prespecified primary cognitive endpoint ADAS-Cog13. The prespecified secondary endpoint CDR-SB, which is used as the sole primary endpoint in recent successful AD drug submissions, is significantly improved at Week 48 with blarcamesine relative to placebo. The findings are supported by biomarkers from the A/T/N spectrum, including plasma Aβ42/40-ratio and reduction of whole brain atrophy. Additionally, the prespecified SIGMAR1 gene variant subgroup analysis confirmed beneficial clinical effect of blarcamesine group through upstream SIGMAR1 activation - subjects with the common SIGMAR1 wild-type gene (excluding carriers of the mutated SIGMAR1 rs1800866 variant) experienced an even greater significant clinical benefit with slowed clinical progression by 49.8% at 48 weeks on the prespecified primary cognitive endpoint ADAS-Cog13. Oral once daily blarcamesine could represent a novel treatment in early AD and be complementary or alternative to anti-beta amyloid drugs.