Efavirenz for Patients With Alzheimer's Disease

1.0 BACKGROUND

1.1. Introduction

The brain is the most cholesterol-rich organ in the body. Circulating peripheral cholesterol cannot cross the blood-brain barrier and enter the brain, so all of cerebral cholesterol is synthesized and metabolized locally. The CNS relies on cholesterol 24-hydroxylation as its major mechanism for eliminating excess cholesterol from the brain. CYP46A1 is an enzyme of the CNS responsible for hydroxylating cholesterol to 24-hydroxycholesterol (24-OHC), which can easily pass the blood-brain barrier and leave the brain to travel into the systemic blood circulation. In fact, 24-OHC plasma level is a specific biomarker for cholesterol homeostasis and CYP46A1 activity in the brain. 24-OHC is a potent modulator of NMDAR, a receptor system in the brain whose hypofunctioning can lead to problems of memory and learning performance. Cyp46a1-/- mice and CYP46A1 transgenic animals established that CYP46A1 is involved in higher-order brain functions and processes beyond mere cholesterol balance: the Cyp46a1-/- mice lacking CYP46A1 demonstrated severe deficiencies in spatial, associative, and motor learning-- as well as deficiencies in long-term potentiation of the hippocampus. On the other hand, CYP46A1 transgenic animals with an abundance of CYP46A1 had improvements in spatial memory and significant increase in the levels of NMDAR in the hippocampus. CYP46A1 overexpressing mice possessing an animal model of AD demonstrated improvements in learning and memory, and reduction in pathological amyloid beta.

Various studies have demonstrated a number of associations between CYP46A1 and AD. For unknown reasons, this neuron-specific enzyme becomes specifically expressed in astrocytes of AD patients; plasma levels of 24-OHC, the product of CYP46A1, also change in AD patients-there are slight elevations of plasma levels in the early stages of AD, followed by decreases in the later stages of AD, (the elevations have been interpreted to represent demyelination of the brain and subsequent release of 24-OHC into the systemic circulation, and the decreases could be attributed to loss of CYP46A1 during the physical process of neuronal degeneration); and, finally, CYP46A1 is highly polymorphic enzyme with the most frequent intronic SNPs (rs754203, rs3742376, rs7157609, and rs4900442 being found at ~29- 40% frequency in the population. The CYP46A1-AD genetic link is, however, unclear, with only about half of linkage studies establishing the CYP46A1-AD association. Data from several laboratories point to enhanced metabolism of cerebral cholesterol as a strong anti-AD disease mechanism.

CYP46A1-mediated metabolism of cerebral cholesterol has never been considered as a pharmacologic target because the proposed activity requires activation of the enzyme, a significant challenge for drug developers. Only 5% of drugs on the market act as enzyme activators, with the majority of pharmaceuticals serving as enzyme inhibitors. Dr. Pikuleva's laboratory--over the course of more than 10 years' work--overcame this challenge by ultimately discovering that in mice, CYP46A1 can indeed be activated pharmacologically by efavirenz (EFV). This CYP46A1 activation also leads to enhanced cerebral cholesterol turnover in mice.

2.0 STUDY RATIONALE

AD has been shown to be a disease featuring rampant aberrant cerebral cholesterol phenomenon; hence the AD population is the most appropriate demographic to include in this study. The investigators expect EFV to be a cerebral cholesterol-metabolism-modifying medication, which may have prolific uses in neurodegenerative diseases--such as AD--where cholesterol metabolism is aberrant.

2.1. Risk/Benefit Assessment

EFV is an FDA-approved anti-retroviral medication for use in the adult population-including the geriatric population. The current recommended dose of Sustiva for adults with HIV is 600 mg daily. This research study will be utilizing very low doses of Sustiva (50 mg and 200 mg), which are the current dosage ranges for children. The investigators have no reason to believe that utilizing 1/3 the adult dose of a drug in the geriatric population will increase the risk of the drug beyond those side effects which are already listed for this product. The study participants will be monitored very closely throughout the course of the research study to bring to light any untoward effects in the participants that would outweigh the potential benefit of this study.

3.0 STUDY OBJECTIVES

3.1. Primary Objectives

• To ascertain if EFV engages CYP46A1 and affects brain cholesterol metabolism.
• To investigate whether EFV alters plasma 24-OHC concentrations.
• To confirm the safety and tolerability of low doses of EFV.

3.2. Secondary Objectives

● To precisely measure EFV's effect on CYP46A1 activation and CNS-cholesterol turnover via Stable Isotope Labeling Kinetics (SILK) study.

3.3. Tertiary Objectives

● To conduct post-hoc analysis to investigate whether APOE isorforms and SNPs in CYP46A1 and CYP2B6 affect study participant response to EFV.

4.0 STUDY DESIGN

4.1. Study Design Overview

A total of 36 patients will be enrolled at 2 sites, 18 patients at the UH site and 18 patients at the MGH site. Site UH, the recruiting clinician at this site is Alan Lerner, MD. Site MGH, recruiting clinician at this site is Steven Arnold, MD. At each site, subjects will be divided into 3 groups; Group1 will consist of 6 subjects who will receive 50 mg EFV; Group 2 will consist of 6 subjects who will receive 200 mg EFV and Group 3 will consist of 6 subjects who will receive Placebo.

5.0 CRITERIA FOR EVALUATIONS

5.1. Primary Endpoints

CYP46A1 engagement will be indicated either by a decrease or increase in plasma 24-OHC from baseline to final time of treatment in the study participants receiving EFV.

CYP46A1 activation will be indicated by ≥ 30% increase in plasma 24-OHC from baseline to final time of treatment in the study participants receiving EFV. The primary dose selection criterion for EFV will be to maximize the proportion of subjects that exceed the threshold for 24-OHC increase, provided there are no associated safety concerns.

A "symptom checklist" will be reviewed and asked of the study participants every two weeks to ensure that no untoward, serious complications arise from treatment with EFV. It is not expected that any serious adverse events will occur. All participants will conclude their treatment with a Post-Study Safety Check Visit during Week 22.

5.2. Secondary Endpoints

Plasma levels of deuterated 24-OHC in patients involved in the SILK study, who will drink deuterated water, will be measured to evaluate EFV's effect on CNS-cholesterol turnover.

5.3. Tertiary Endpoints

Carriers of the APOE E4 allele could be better responders to the anti-AD effects of EFV because in the brain, cholesterol output is a function of both APOE-mediated cholesterol transport and CYP46A1-mediated cholesterol metabolism. Accordingly, if one of these pathways is impaired, like in APOE E4 carriers, the significance of the other pathway is increased. Similarly, the CYP46A1 polymorphisms may affect the ability of EFV to increase 24-OHC because the baseline levels of CYP46A1 and 24-OHC in the carriers of these polymorphisms could be lower, if these polymorphisms affect CYP46A1 protein levels. Finally, at a high dose (400-600 mg/day), plasma concentrations of EFV depend on the frequent SNP rs3745274 in CYP2B6 that metabolizes EFV. Genotyping will be carried out by the Molecular Biology and Genotyping Module at Case Western Reserve University.

6.0 SUBJECT SELECTION

A total of 36 participants, either male or female, will be enrolled between the ages of 55-85 for 22 weeks. Recruitment of study participants will occur during potential participants' regularly-schedule clinical visits, or from chart review.

6.1. Study Population

All participants should have either mild cognitive impairment or early dementia due to AD, defined clinically as follows:

• Complaint of cognitive decline
• Mini-Mental Status Examination (MMSE) totaling between 16-30
• Clinical Dementia Rating (CDR) equaling 0.5-1

The 36 study participants will be recruited in a timeframe of approximately 8-9 months. The two study sites are anticipated to recruit 2 study participants per month. This anticipated rate is based on the investigators previous experience in clinical study subject enrollment and high patient volume at the University Hospitals Brain Health and Memory Center and the Memory Disorders Clinic, and the Memory Disorders Unit and Massachusetts Alzheimer's Disease Research Center (MADRC) at Massachusetts General Hospitals (MGH).

7.0 CONCOMITANT THERAPIES

Medical history will be collected for all medications at the screening visit and at all subsequent clinical and telephone follow-up visits. All subjects should be maintained on the same medications from screening through Visit 7, as medically feasible, with no introduction of new therapies.If any changes in concomitant medications are made for any reason by the study participant's personal physician(s), the changes and reason(s) for the change(s) will be documented.

7.1. Allowed

Except as noted in the prohibited medications section 7.2. Stable use of cholinesterase inhibitor is permitted if doses are stable for 3 months prior to enrollment.

7.2. Prohibited

EFV is mainly metabolized by CYP2B6 and CYP3A4, and in the 600 mg/day dose range or higher, has potential interactions with other drugs. EFV is expected to stimulate cholesterol elimination from the brain, inducing a compensatory upregulation of cerebral cholesterol biosynthesis; statins that cross the blood-brain barrier would be expected to especially inhibit cerebral cholesterol biosynthesis and confound 24-OHC biomarking of EFV's effect. Study participants in the clinical research study should not have taken the following medication within 3 months of commencing their participatory role in the study: simvastatin, antiepileptic agents, clopidogrel, voriconazole, systemic ketoconazole, cyclosporine, St. John's Wort.