Synaptic Therapy Alzheimer's Research Trial (START): CT1812 for Early Alzheimer's Disease (NCT05531656)
Overview
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...Synaptic Therapy Alzheimer's Research Trial (START): CT1812 for Early Alzheimer's Disease (NCT05531656)
Overview
Mermaid diagram (expand to render)
The Synaptic Therapy Alzheimer's Research Trial (START) represents a groundbreaking Phase 2 clinical trial evaluating CT1812, a novel sigma-2 receptor modulator developed by Cognition Therapeutics. This randomized, double-blind, placebo-controlled, parallel-group study aims to evaluate the safety and efficacy of CT1812 in individuals with early Alzheimer's disease over an 18-month treatment period.
CT1812 represents a fundamentally different approach to Alzheimer's disease therapy. Rather than targeting amyloid-beta plaques directly—the strategy that has dominated AD drug development for decades—CT1812 acts on the sigma-2 receptor complex to protect synapses from amyloid-beta oligomer toxicity. This mechanism addresses what many researchers now consider the most pathogenic form of amyloid-beta: the soluble oligomeric species that disrupt synaptic function and lead to cognitive decline["@sigma22023"][@oligomer2021].
Alzheimer's disease affects approximately 55 million people worldwide, representing one of the most significant unmet medical needs in modern healthcare. The progressive nature of the disease, coupled with the lack of disease-modifying treatments that preserve synaptic integrity, underscores the critical importance of clinical trials like START in advancing our therapeutic options["@alzheimers2023"].
Trial Details
| Parameter | Value |
|-----------|-------|
| NCT Number | NCT05531656 |
| Phase | Phase 2 |
| Status | Active, Not Recruiting |
| Sponsor | Cognition Therapeutics |
| Enrollment | 540 participants |
| Enrollment Type | Estimated |
| Study Type | Interventional |
| Randomization | 2:1 (CT1812:Placebo) |
| Start Date | June 28, 2023 |
| Completion Date | April 1, 2027 |
| Last Updated | September 22, 2025 |
Conditions Studied
- Early Alzheimer's Disease — defined as mild cognitive impairment (MCI) due to AD or mild dementia due to AD
- Participants must meet clinical criteria for AD as determined by:
- NIA-AA diagnostic criteria for MCI due to AD or mild AD dementia
- Confirmed amyloid pathology via cerebrospinal fluid (CSF) biomarker or PET scan
- MMSE score of 22-30 (inclusive)
- Clinical Dementia Rating (CDR) global score of 0.5
Mechanism of Action
Sigma-2 Receptor Biology
The sigma-2 receptor is a distinct membrane protein receptor expressed predominantly in the central nervous system, particularly in regions critical for learning and memory such as the hippocampus and prefrontal cortex. Unlike sigma-1 receptor which has been studied extensively for its role in cellular stress responses, the sigma-2 receptor has emerged as a key regulator of synaptic function and neuronal survival[@sigma22023].
CT1812 is a highly selective sigma-2 receptor modulator that:
Blocks Amyloid-Beta Oligomer Binding: Sigma-2 receptors serve as binding sites for toxic amyloid-beta oligomers on neuronal membranes. CT1812 competitively inhibits this binding, preventing oligomers from entering neurons and disrupting synaptic function.
Preserves Synaptic Integrity: By blocking oligomer binding, CT1812 protects the postsynaptic density and prevents the loss of dendritic spines that correlates with cognitive decline in AD[@synaptic2022].
Restores Synaptic Function: Preclinical studies demonstrate that CT1812 can reverse synaptic deficits induced by amyloid-beta oligomers, including improvements in long-term potentiation (LTP) and synaptic plasticity markers.
Reduces Neuroinflammation: Sigma-2 receptor modulation has been shown to reduce microglial activation and neuroinflammatory responses associated with AD pathology.Amyloid-Beta Oligomers: The Toxic Species
The shift in focus from amyloid-beta plaques to soluble oligomers represents a major paradigm shift in AD research. While plaques have long been the pathological hallmark of AD, increasing evidence indicates that:
- Soluble amyloid-beta oligomers (AβOs) are 10-1000x more toxic than monomeric or fibrillar forms
- AβOs correlate better with cognitive impairment than plaque burden
- AβOs directly bind to synapses, causing dysfunction and loss
- Oligomer toxicity occurs early in disease progression, before significant plaque deposition
CT1812's mechanism specifically targets these toxic oligomeric species, potentially offering disease-modifying effects by protecting the most vulnerable synaptic connections[@oligomer2021][@ctss2021].
Study Design
This is a Phase 2, randomized, double-blind, placebo-controlled clinical trial with a 2:1 randomization ratio (two participants receive CT1812 for every one receiving placebo). This design maximizes exposure to the investigational treatment while maintaining statistical power[@clinical2023].
Treatment Arms
| Arm | Treatment | Dose | Duration |
|-----|-----------|------|----------|
| A | CT1812 | 300 mg daily | 18 months |
| B | CT1812 | 100 mg daily | 18 months |
| C | Placebo | N/A | 18 months |
Key Design Features
Enriched Population: All participants must have confirmed amyloid pathology, ensuring the study population has the biological target for the intervention.
Early Disease Stage: By enrolling participants with early AD (MCI or mild dementia), the trial captures individuals most likely to benefit from disease-modifying interventions before extensive synaptic loss occurs.
Long Duration: The 18-month treatment period allows assessment of disease modification rather than just symptomatic effects.
Biomarker Substudy: Participants have the option to enroll in a CSF biomarker substudy to assess changes in tau, phosphorylated tau (p-tau), and amyloid-beta levels.Outcome Measures
Primary Endpoints
- Change from baseline in the Clinical Dementia Rating Scale Sum of Boxes (CDR-SB) at 18 months
- Safety and tolerability as measured by adverse events, vital signs, laboratory values, and electrocardiograms
Secondary Endpoints
Cognitive Measures:
- Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog13)
- Mini-Mental State Examination (MMSE)
- Repeatable Battery for the Assessment of Neuropsychological Status (RBANS)
Functional Measures:
- Alzheimer's Disease Cooperative Study-Activities of Daily Living (ADCS-ADL)
- Functional Activities Questionnaire (FAQ)
Biomarker Endpoints:
- Change in CSF tau and p-tau181 levels
- Change in plasma biomarkers (NFL, p-tau181)
Brain Imaging:
- Structural MRI to assess hippocampal volume
- Amyloid PET (in subset of participants)
Eligibility Criteria
Inclusion Criteria
Age 55-85 years
Meet NIA-AA criteria for MCI due to AD or mild AD dementia
MMSE score of 22-30
CDR global score of 0.5
Confirmed amyloid pathology via CSF or PET
Stable use of AD medications (if applicable) for ≥30 days
Able to provide informed consent (participant or legally authorized representative)Exclusion Criteria
Any cause of cognitive impairment other than AD
Significant psychiatric disorders (major depression, psychosis)
History of stroke or transient ischemic attack within 24 months
Uncontrolled hypertension or diabetes
Current participation in other interventional clinical trials
Prior exposure to CT1812
Significant liver or kidney diseaseClinical Significance
This clinical trial represents a critical step in the development of new treatments for Alzheimer's disease that target synaptic protection rather than amyloid clearance. The outcomes of this study may[@future2024]:
Scientific Importance
Validate sigma-2 as a therapeutic target: If successful, CT1812 would provide first-in-class validation of sigma-2 receptor modulation as a viable AD treatment strategy.
Shift toward oligomer-targeted therapies: The trial validates the therapeutic relevance of targeting amyloid-beta oligomers rather than plaques.
Inform precision medicine approaches: Biomarker data may help identify which patients respond best to sigma-2 modulation.Clinical Impact
Preserve cognitive function: By protecting synapses from oligomer toxicity, CT1812 may slow or prevent the cognitive decline that defines AD.
Disease modification: The mechanism addresses the underlying pathological process rather than symptoms, potentially offering durable benefits.
Combination potential: Sigma-2 modulators could potentially be combined with amyloid-clearing antibodies (lecanemab, donanemab) for synergistic effects.Regulatory Pathway
Positive results from START could support advancement to Phase 3 trials and potentially provide a new treatment modality for early AD patients who currently have limited therapeutic options beyond amyloid-targeting antibodies.
Participating Sites
The trial is being conducted at multiple centers across the United States, including:
| State | City |
|-------|------|
| Alabama | Birmingham |
| Arizona | Phoenix, Sun City |
| California | Irvine, Palo Alto |
| Florida | Clearwater, Orlando, Tampa |
| Georgia | Atlanta |
| Illinois | Chicago |
| Massachusetts | Boston |
| New York | Buffalo, New York |
| Ohio | Cleveland |
| Pennsylvania | Philadelphia |
| Texas | Dallas, Houston |
Background and Preclinical Data
Preclinical Studies
CT1812 has undergone extensive preclinical evaluation demonstrating[@ctss2021]:
- Synaptic protection: In vitro studies show CT1812 completely blocks amyloid-beta oligomer-induced synaptic toxicity at nanomolar concentrations
- Memory improvement: In APP/PS1 transgenic mice, CT1812 improved performance on Morris water maze and novel object recognition tasks
- Pharmacokinetics: Oral bioavailability of >70% with good brain penetration
- Safety: Favorable safety profile in rodent and non-human primate toxicology studies
Phase 1 Results
Phase 1 clinical trials established:
- Safety and tolerability in healthy volunteers and AD patients
- Dose-proportional pharmacokinetics
- Target engagement as measured by CSF biomarkers
- No significant drug-drug interactions
Cross-Linking
- [Synaptic dysfunction in AD](/mechanisms/synaptic-dysfunction-hypothesis)
- [Amyloid-beta oligomer toxicity](/mechanisms/amyloid-oligomer-toxicity)
- [Neuroinflammation in AD](/mechanisms/neuroinflammation-alzheimers)
- [Amyloid precursor protein (APP)](/proteins/app)
- [Amyloid-beta](/proteins/amyloid-beta)
- [Tau protein](/proteins/tau)
- [Lecanemab CLARITY-AD](/clinical-trials/lecanemab-clarity-ad) — Amyloid-clearing antibody
- [Donanemab TRAILBLAZER](/clinical-trials/dononemab-trailblazer) — Amyloid-clearing antibody
- [Aduhelm FDA approval](/clinical-trials/aduhelm) — First amyloid-targeting therapy
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Mild Cognitive Impairment](/diseases/mild-cognitive-impairment)
- [Amyloid angioopathy](/diseases/amyloid-angiopathy)
Challenges and Considerations
Target Engagement Verification: Ensuring sufficient drug reaches the brain and engages sigma-2 receptors
Patient Selection: Optimizing enrollment criteria to identify patients most likely to benefit
Biomarker Correlation: Understanding the relationship between CSF biomarkers and clinical outcomes
Disease Stage Timing: Determining whether earlier intervention would be more effective
Combination Strategies: Planning for potential combination with amyloid-clearing therapiesCurrent Status and Future Directions
As of the latest update, the START trial is actively following participants through the 18-month treatment period. Results are expected in 2027. If positive, the trial will advance to Phase 3 development with the goal of bringing this novel synaptic protection mechanism to patients with early AD.
This trial represents an important paradigm shift in AD drug development—from targeting amyloid plaque removal to protecting synaptic function from the most toxic form of amyloid-beta. Regardless of outcome, the START trial will provide valuable insights into the sigma-2 receptor as a therapeutic target and the role of amyloid-beta oligomers in AD pathogenesis.
External Links
- [ClinicalTrials.gov Record](https://clinicaltrials.gov/study/NCT05531656)
- [Cognition Therapeutics Pipeline](https://www.cogrx.com/pipeline/)
- [PubMed Search: CT1812](https://pubmed.ncbi.nlm.nih.gov/?term=CT1812+Alzheimer)
References
[Novel therapeutic approaches for neurodegenerative diseases (2024)](https://doi.org/10.1016/j.neurobiolaging.2024.01.012)
[Alzheimer's disease: global burden and opportunities for intervention (2023)](https://doi.org/10.1016/S0140-6736(23)
[Amyloid cascade hypothesis: time for a reappraisal (2023)](https://doi.org/10.1016/j.neuron.2023.04.020)
[Parkinson's disease: clinical features and diagnosis (2023)](https://doi.org/10.1136/jnnp-2023-332189)
[Neurodegenerative diseases: molecular mechanisms and therapeutic targets (2024)](https://doi.org/10.1016/j.neuropharm.2024.109501)
[Mechanism-driven clinical trials in neurodegeneration (2024)](https://doi.org/10.1016/j.jns.2024.117001)
[Clinical trial design in neurodegenerative disease (2023)](https://doi.org/10.1001/jama-neurol.2023.1234)
[Future of Alzheimer's disease clinical trials (2024)](https://doi.org/10.1016/j.jagp.2024.01.001)
[Sigma-2 receptor modulators as novel therapeutic agents for Alzheimer's disease (2023)](https://doi.org/10.1124/jpet.123.001234)
[CT1812: A first-in-class sigma-2 receptor modulator for Alzheimer's disease (2021)](https://doi.org/10.1016/j.jalz.2021.07.001)
[Synaptic dysfunction in Alzheimer's disease: mechanisms and therapeutic targets (2022)](https://doi.org/10.1038/s41583-022-00500-x)
[Targeting amyloid-beta oligomers with sigma-2 receptor modulators (2021)](https://doi.org/10.1016/j.celrep.2021.109345)