Pilot Trial of Dronabinol Adjunctive Treatment of Agitation in Alzheimer's Disease (THC-AD)

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Abstract

Introduction

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disease of aging (70%). Neuropsychiatric symptoms (NPS) in AD are a major cause of burden to patients, caregivers, and society and are near-universal at some point in the AD course (97%). One of the most troubling NPS is agitation (Agit-AD), typified by a variety of problem behaviors including combativeness, yelling, pacing, lack of cooperation with care, insomnia, and restlessness. Neurobiological mechanisms that contribute to Agit-AD include brain atrophy, degradation of neurotransmission, neuroinflammation, disrupted circadian rhythms, comorbidities, and frailty. There is a great need for better interventions that target Agit-AD, which is a major source of disease progression, patient disability, financial burden, and caregiver stress. Dronabinol is synthetic tetrahydrocannabinol (THC, one of the predominant biochemical constituents of cannabis) and is FDA approved for anorexia and nausea. Cannabinoids may improve Agit-AD by providing protection against neuroinflammation and excitotoxicity, regulating neurotransmitters, improving comorbidities, stabilizing circadian rhythms, and increasing cerebral blood flow. This pilot trial could open the door to “re-purposing” dronabinol as a novel and safe treatment for Agit-AD with significant public health impact.

Methods

THC-AD is a three-week placebo-controlled, double-blind, randomized clinical trial of dronabinol (10 mg QD) in 80 patients with severe Agit-AD. Capsules of dronabinol contain 2.5 mg per dose (5 mg daily) during Week 1, then increase to 5 mg per dose (10 mg daily) for Weeks 2 and 3. The half-life of dronabinol is ∼4 hours, so study medication is administered BID at 08:00 and 14:00 to maximize daytime coverage for agitation and to minimize sundowning. Inclusionary criteria include a diagnosis of AD, severe agitation as determined by the Neuropsychiatric Inventory-Clinician Rating Scale (NPI-C), and being 60-95 years old, while exclusionary criteria include serious or unstable medical illness, seizure disorder, delirium, current use of lithium, and inability to swallow a pill. Primary outcomes are a change in the Pittsburgh Agitation Scale and NPI-C Agitation/Aggression subscales. Secondary outcomes are measures of agitation, cognition, sleep, and global functioning as determined by the following assessments: the NPI-C, Cohen Mansfield Agitation Inventory, Clinical Global Impression of Change, Activities of Daily Living, Mini-Mental State Examination (MMSE), Severe Impairment Battery (8 item), and subjective and observer-rated drug effects. Safety outcomes include monitoring for adverse events (AEs), weekly health assessments, EKG changes, incident delirium (Confusion Assessment Method), and changes in laboratory values. DNA specimens are collected to explore cannabinoid receptor polymorphisms that may affect response to dronabinol. Serum samples are collected to examine the association of peripheral markers of inflammation with agitation and response to dronabinol. Concomitant medications are limited to currently used antipsychotics, antidepressants, and benzodiazepines, as well as anticonvulsant therapy when not used for seizure disorder. PRN rescue medications include total daily doses up to 0.75 mg of lorazepam and 100 mg of trazodone.

Results

We have enrolled 37 out of 80 participants (Table 1: mean age 78.2 years, 78.4% female, 83.8% Caucasian, mean education 13.2 years, 48.6% family history). Study participants are significantly cognitively impaired (Table 2: mean baseline MMSE of 7.1), agitated (mean NPI-C Agitation 14.8, mean NPI-C Aggression 6.4) and in reasonable overall health (Figure 1: General Medical Health Rating, 10.8% “excellent,” 48.6% “good” and 40.5% “fair”). Recorded AEs have been tolerable (Figure 2). Due to the COVID-19 pandemic, we expanded our inpatient trial to include outpatient enrollments and implemented hybrid visits with telemedicine to limit in-person interactions. To bolster our recruitment, we are collaborating with additional clinical sites, increasing dementia bed capacity, and deploying recruitment strategies for outpatients, including referrals from providers and other research trials, social media ads, and virtual community outreach. Updated results will be presented at AAGP (estimated 6-10 additional participants).

Conclusions

Agitation is one of the most common behavioral manifestations of AD and is associated with greater caregiver burden and shorter time to institutionalization. Current treatments for Agit-AD have a plethora of safety limitations, and there is a particularly acute need for interventions for severe Agit-AD in advanced dementia. One important question for treatment development is whether Agit-AD represents a specific target for intervention or a nonspecific syndrome shared with many other diseases. This clinical trial may enable us to understand if targeting the cannabinoid system will be a safe and effective approach to treat this global health concern.

Funding

National Institute on Aging, R01AG050515