Varenicline for Falls in Hypocholinergic Parkinson Disease (NCT06679374)

Varenicline for Falls in Hypocholinergic Parkinson Disease (NCT06679374)

Overview

Varenicline (marketed as Chantix® for smoking cessation) is being investigated in this Phase 2 randomized controlled trial as a potential treatment to reduce falls in [Parkinson's disease](/diseases/parkinsons-disease) patients who have significant cholinergic denervation. The trial specifically enrolls patients with hypocholinergic status, defined by reduced [acetylcholine](/mechanisms/cholinergic-signaling-neurodegeneration) signaling in the occipital association cortex as measured by F-fluoroethoxybenzovesamicol (FEOBV) PET imaging["@nctgov"].

Varenicline for Falls in Hypocholinergic Parkinson Disease (NCT06679374)

Overview

Varenicline (marketed as Chantix® for smoking cessation) is being investigated in this Phase 2 randomized controlled trial as a potential treatment to reduce falls in [Parkinson's disease](/diseases/parkinsons-disease) patients who have significant cholinergic denervation. The trial specifically enrolls patients with hypocholinergic status, defined by reduced [acetylcholine](/mechanisms/cholinergic-signaling-neurodegeneration) signaling in the occipital association cortex as measured by F-fluoroethoxybenzovesamicol (FEOBV) PET imaging["@nctgov"].

Falls are a major source of morbidity in Parkinson's disease, affecting up to 60% of patients annually. Current treatment options are limited, with most approaches targeting dopaminergic pathways rather than the cholinergic deficits that contribute to balance and gait dysfunction. Varenicline's action as a partial agonist at [alpha-7 nicotinic acetylcholine receptors (alpha-7 nAChR)](/proteins/chrnA7-protein) offers a novel mechanism to address this gap["@cholinergic2023"].

Trial Information

| Attribute | Details |
|-----------|---------|
| NCT Number | NCT06679374 |
| Title | Reducing Falls With Varenicline in Hypocholinergic Parkinson Disease |
| Phase | Phase 2 |
| Status | Recruiting |
| Sponsor | Vikas Kotagal (Investigator-initiated) |
| Participants | 102 |
| Start Date | April 9, 2025 |
| Estimated Completion | January 2027 |
| Intervention | Varenicline vs. Placebo |
| Duration | 12 months |

Mechanism of Action

Alpha-7 Nicotinic Acetylcholine Receptor Agonism

Varenicline is a partial agonist at the alpha-7 subtype of nicotinic acetylcholine receptors (nAChRs). These receptors are widely expressed in the brain, including in regions critical for attention, sensory processing, and motor control[@varenicline2007].

Why alpha-7 nAChR for falls in PD:

Varenicline Pharmacology

| Property | Value |
|----------|-------|
| Primary Target | Alpha-7 nAChR (partial agonist) |
| Secondary Target | Alpha-4-beta-2 nAChR (partial agonist) |
| Bioavailability | ~90% (oral) |
| Half-life | ~24 hours |
| Approved Use | Smoking cessation (0.5 mg and 1 mg tablets) |
| Standard Dosing | Titrated from 0.5 mg BID to 1 mg BID over 1 week |

For the PD trial, varenicline dosing follows a similar titration schedule to the approved smoking cessation regimen, reaching therapeutic doses within the first week.

Cholinergic Denervation in PD

The trial's enrollment criteria require participants to have occipital association cortex cholinergic denervation in the lowest tertile of the normal range on FEOBV PET. This imaging biomarker provides a direct measure of cholinergic terminal density[@feobvpet].

FEOBV PET background:

• FEOBV (F-fluoroethoxybenzovesamicol) is a radiotracer that binds to the vesicular acetylcholine transporter (VAChT)
• Reduced FEOBV uptake indicates loss of cholinergic nerve terminals
• PD patients with lower FEOBV binding in the occipital cortex show worse performance on dual-task gait assessments
• This provides a patient enrichment strategy — targeting those most likely to benefit from cholinergic augmentation

Eligibility Criteria

Inclusion Criteria

• Diagnosis of [Parkinson's disease](/diseases/parkinsons-disease) based on Movement Disorders Society Clinical Diagnostic Criteria
• Occipital association cortex cholinergic denervation in the lowest tertile of the normal range on FEOBV PET scan
• Legally authorized representative (LAR) able to co-sign informed consent, OR participant has capacity to provide informed consent as assessed by the UCSD Brief Assessment of Capacity to Consent (UBACC)
• Mild Cognitive Impairment consistent with Parkinson disease Mild Cognitive Impairment (PD-MCI)
• Modified Hoehn and Yahr score less than 4.0 (not severely disabled)

Exclusion Criteria

• Atypical Parkinsonian conditions (MSA, PSP, CBS, etc.)
• Current or recent (within 6 months) use of tobacco products, nicotine patches/gum, or varenicline
• [Dopamine](/mechanisms/dopaminergic-signaling)blocking drugs or anticholinergic drugs (trihexyphenidyl, benztropine) at screening
• Contraindications to MRI or PET imaging
• Stage 4-5 chronic kidney disease (eGFR <30 mL/min)
• Active mood disorder (depression/anxiety >2 weeks in past 30 days)
• Active suicidal ideation
• History of myocardial infarction or unstable angina in past 90 days
• Epilepsy or seizures within 12 months
• Heavy alcohol use (AUDIT score ≥8)
• Unable to swallow pills
• Known allergic reaction to varenicline
• Participation in another interventional trial

Outcome Measures

Primary Outcome

| Measure | Description |
|---------|-------------|
| Normal Pace-Dual Task Cost (npDTC) | Change from baseline to 12 months in the difference between single-task normal pace gait speed and dual-task gait speed. Lower npDTC indicates less interference from the cognitive task, suggesting better gait automaticity and reduced fall risk. |

The dual-task paradigm assesses how much a person's gait is disrupted when simultaneously performing a cognitive task (e.g., serial sevens or verbal fluency). In PD, this dual-task cost is exaggerated due to competing demands on limited attentional resources. Cholinergic enhancement should reduce this interference.

Secondary Outcomes

| Measure | Description |
|---------|-------------|
| Number of falls | Total count of falls from first dose to 12-month visit, assessed via fall diaries and monthly phone calls |

Falls are defined as an unintentional descent to the floor, ground, or lower level. The fall count provides a direct clinical endpoint that is highly meaningful to patients and caregivers.

Scientific Rationale

Why Targeting Cholinergic System for Falls?

Falls in PD have multiple contributing factors:

Cholinergic augmentation addresses multiple pathways simultaneously: improving attention for environmental hazard detection, enhancing sensorimotor integration for rapid postural corrections, and supporting the automaticity of gait[@cholinergic2024].

Why Varenicline?

Varenicline was selected because:

• Proven safety profile: FDA-approved for smoking cessation since 2006
• Excellent CNS penetration: Crosses the blood-brain barrier effectively
• Selective alpha-7 agonism: Targets the specific receptor subtype most relevant to cognitive-motor integration
• Once-daily or BID dosing: Practical for elderly PD patients with complex medication regimens
• No significant drug-drug interactions with standard PD medications

Comparison to Cholinesterase Inhibitors

Unlike donepezil or rivastigmine (acetylcholinesterase inhibitors that boost acetylcholine non-selectively), varenicline provides targeted agonism at specific nAChR subtypes. This mechanistic distinction may offer advantages:

• More precise receptor activation
• Avoids global increase in acetylcholine that could cause cholinergic side effects
• Direct agonism rather than indirect enzyme inhibition

Cholinergic System and Falls in PD

Basal Forebrain Cholinergic System

The basal forebrain contains large neurons that synthesize acetylcholine via choline acetyltransferase (ChAT) and project throughout the cortex. These cholinergic projections are critical for:

• Attention: Orienting to salient stimuli and maintaining focus
• Memory: Encoding and retrieving sensory information
• Executive function: Planning and monitoring actions
• Modulation of sensory processing: Enhancing signal-to-noise ratio in cortical circuits

Pedunculopontine Nucleus

The pedunculopontine nucleus (PPN) is a brainstem structure with cholinergic neurons that project to thalamic and spinal cord targets. PPN cholinergic dysfunction contributes to:

• Freezing of gait
• Postural instability
• Falls

FEOBV PET as a Biomarker

FEOBV PET provides a quantitative measure of cholinergic terminal density across cortical regions. Studies have shown:

• PD patients with lower occipital cortex FEOBV binding have worse dual-task gait performance
• Cholinergic denervation correlates with fall frequency
• This biomarker can identify patients most likely to benefit from cholinergic augmentation therapies

Cross-Links to NeuroWiki

• [Parkinson's Disease](/diseases/parkinsons-disease) — Target indication
• [Cholinergic Signaling in Neurodegeneration](/mechanisms/cholinergic-signaling-neurodegeneration) — Mechanism basis
• [Alpha-7 Nicotinic Receptor (CHRNA7)](/proteins/chrna7-protein) — Drug target
• [CHRNA7 Gene](/genes/chrna7) — Drug target gene
• [Falls in Parkinson's Disease](/mechanisms/pd-falls-mechanism) — Related mechanism
• [Gait and Balance Disorders in PD](/mechanisms/pd-gait-disorders) — Related mechanism
• [Non-Motor Symptoms in PD](/mechanisms/pd-non-motor-symptoms) — Related symptoms
• [Chantix (Varenicline) — Smoking Cessation](/therapeutics/varenicline-smoking-cessation) — Existing page (approved use)

References

See Also

• [CHRNA7 Gene](/wiki/genes-chrna7) — references