Allopregnanolone (also known as allo, brexanolone, or SAGE-547) is a neurosteroid being developed as a regenerative therapeutic for mild Alzheimer's disease. This Phase 2 clinical trial (NCT04838301), conducted by the University of Arizona Center for Innovation in Brain Science, evaluates the safety, tolerability, and efficacy of intravenous allopregnanolone in patients with mild Alzheimer's disease[1][2].
Unlike conventional AD therapies that target amyloid or tau pathology, allopregnanolone takes a regenerative approach by promoting neurogenesis, protecting synapses, and supporting overall brain health. This represents a paradigm shift in AD therapeutics from disease modification to true regeneration of neural function[3].
| Field | Value |
|---|---|
| NCT Number | NCT04838301 |
| Brief Title | Allopregnanolone Regenerative Therapeutic for Mild Alzheimer's Disease |
| Official Title | A Phase 2 Study of Allopregnanolone (Allo) as a Regenerative Therapeutic for Mild Alzheimer's Disease |
| Study Type | Interventional |
| Phase | Phase 2 |
| Enrollment | 200 participants |
| Status | Completed |
| Sponsor | University of Arizona |
| Collaborators | NIH National Institute on Aging (NIA) |
| Study Start | April 2021 |
| Primary Completion | December 2023 |
This is a multicenter, randomized, double-blind, placebo-controlled, parallel-group Phase 2 clinical trial evaluating the safety, tolerability, and efficacy of intravenous allopregnanolone in participants with mild Alzheimer's disease.
Randomized, 1:1 allocation to treatment vs. placebo.
Parallel group design with multiple dose cohorts.
Matched vehicle solution administered via identical infusion protocol.
Allopregnanolone is a neurosteroid — a naturally occurring neuromodulator derived from progesterone that acts as a positive allosteric modulator of the GABAA receptor.
GABAergic Modulation: Allopregnanolone enhances GABAA receptor function, the primary inhibitory neurotransmitter system in the brain. This modulation affects neuronal excitability, synaptic plasticity, and circuit function.
Neurogenesis Promotion: Preclinical studies demonstrate that allopregnanolone stimulates hippocampal neurogenesis — the birth of new neurons in the dentate gyrus. This is particularly relevant for AD, where neurogenesis is impaired.
White Matter Integrity: Evidence suggests allopregnanolone promotes oligodendrocyte differentiation and myelination, potentially protecting white matter integrity compromised in AD.
Anti-inflammatory Effects: Neurosteroids exhibit anti-inflammatory properties that may contribute to neuroprotection.
Neurotrophic Support: Allopregnanolone has been shown to increase brain-derived neurotrophic factor (BDNF) expression, supporting neuronal survival and plasticity.
The regenerative therapeutic approach targets multiple pathological features of AD:
This trial represents a significant effort in developing regenerative therapies for AD that move beyond symptom modification to address underlying neuronal loss and dysfunction[4].
Allopregnanolone (also known as allo, brexanolone, or SAGE-547) has undergone extensive clinical development for neurological indications:
Allopregnanolone is an endogenous neurosteroid derived from progesterone through the cholesterol side-chain cleavage pathway[5]. It is synthesized de novo in the brain, primarily in glial cells, and acts as a potent positive allosteric modulator of GABA-A receptors.
Allopregnanolone binds to a distinct recognition site on the GABA-A receptor that is separate from the benzodiazepine binding site[6]. This site has the following properties:
Adult hippocampal neurogenesis occurs in the dentate gyrus throughout life and is essential for memory formation and cognitive flexibility[7]. In AD:
Allopregnanolone promotes neurogenesis through:
Chronic neuroinflammation is a hallmark of AD pathogenesis[8]. Allopregnanolone exerts anti-inflammatory effects through:
Mitochondrial dysfunction is an early event in AD pathogenesis[@mitochondria2024]. Allopregnanolone protects mitochondria through:
Allopregnanolone influences gene expression through epigenetic mechanisms[9]:
Brain-derived neurotrophic factor (BDNF) is critical for neuronal survival and synaptic plasticity[10]. Allopregnanolone:
White matter integrity is compromised in AD, contributing to cognitive decline[11]. Allopregnanolone supports white matter health through:
Synaptic dysfunction is a key mediator of cognitive decline in AD[12]. Allopregnanolone enhances synaptic plasticity through:
| Therapeutic | Mechanism | Administration | Stage | Key Feature |
|---|---|---|---|---|
| Allopregnanolone | GABA-A modulation + regeneration | IV infusion | Phase 2/3 | Regenerative |
| Donepezil | AChE inhibition | Oral | Approved | Symptomatic |
| Aducanumab | Anti-amyloid antibody | IV monthly | Approved | Disease-modifying |
| Lecanemab | Anti-amyloid antibody | IV biweekly | Approved | Disease-modifying |
| Allo | Regenerative + neuroprotection | IV | Phase 2 | Multi-target |
The allopregnanolone program continues to evaluate:
The trial was conducted at multiple centers across the United States:
Brinton RD et al. Allopregnanolone as a regenerative therapeutic for Alzheimer's disease. Ann Neurol. 2022. 2022. ↩︎
Irwin RW et al. Allopregnanolone preclinical and clinical data for Alzheimer's disease. Neurobiol Dis. 2020. 2020. ↩︎
White matter integrity and oligodendrocyte function. 2024. ↩︎