Simufilam 50 mg or 100 mg for Mild-to-Moderate Alzheimer's Disease

A 76-week safety and efficacy study of simufilam (PTI-125) given twice daily to participants with mild-to-moderate Alzheimer's disease (AD) for 76 weeks. Approximately 1083 participants will be randomized (1:1:1) to receive either placebo, 50 mg tablets of simufilam, or 100 mg tablets of simufilam, twice daily, for 76 weeks. Clinic visits will occur 4 weeks after the baseline visit, and then every 12 weeks until the end of the study. The safety of simufilam, and its efficacy in enhancing cognition and slowing cognitive and functional decline will be evaluated.

The primary objective of this study is to investigate the safety and efficacy of simufilam (PTI-125) in enhancing cognition and slowing cognitive and functional decline following 76-week, repeat-dose oral administration in participants with mild-to-moderate AD. Secondary objectives are to assess neuropsychiatric symptoms and to replicate the cerebrospinal fluid (CSF) biomarker effects observed in the two Phase 2 studies (PTI-125-03 and PTI-125-02) after 76 weeks of simufilam treatment. A third objective is to investigate the effect of simufilam treatment on plasma biomarkers as well as anatomical correlates of disease progression (brain volume \[hippocampus, ventricles and whole brain\]; and amyloid and tau deposition in the brain). A limited number of research sites will be invited to participate in sub-studies to assess the impact of simufilam on anatomical and biomarker endpoints, including: change from Baseline in CSF biomarkers (30 subjects/group); brain volume via magnetic resonance imaging (MRI) (50 subjects/group); and amyloid and tau positron emission tomography (PET) (40 and 50 subjects/group, respectively). Participants in both PET sub-studies will be required to have an MRI during the Screening Period and provide plasma for a biomarker sub-study. Participants in the tau PET sub-study will also provide additional plasma for a pharmacokinetic (PK) exposure response analysis. Changes from baseline for these imaging and fluid biomarkers represent additional secondary endpoints. The 90 subjects (30 per group) in the CSF sub-study will undergo lumbar puncture during the Screening Period and again at the Week 76 End-of-Treatment Visit to collect CSF biomarkers.

Safety will be evaluated by adverse event monitoring, vital signs, clinical labs, and the Columbia Suicide Severity Rating Scale at every visit. Subjects will undergo MRI during screening to ensure entry criteria are met (unless recent MRI confirms entry criteria); however, 150 subjects (50 subjects per treatment group) will also undergo repeat MRI assessments at Weeks 40 and 76 to assess both long-term safety and drug impact on brain volume as noted above. Resting electrocardiograms will be conducted at Baseline (Study Day 1) and Weeks 4, 40 and 76. A complete physical and neurological examination will be performed at screening, and brief examinations will be performed at all other visits. Weight will be measured during the Screening Period, at Baseline (Study Day 1) and at all other visits.

An independent Data Safety Monitoring Board (DSMB) will meet periodically to review subject safety assessments and determine if dosing may continue. A charter will be developed with specific guidance for the DSMB.

Eligibility Criteria:
Key Inclusion Criteria:

1. Meets National Institute on Aging and Alzheimer's Association Research Framework criteria for individuals in clinical Stage 4 or 5 of the Alzheimer's continuum.
2. Evidence for AD pathophysiology, confirmed prior to or during screening.
3. MMSE score ≥ 16 and ≤ 27 at screening.
4. Clinical Dementia Rating - Global Score must be 0.5, 1 or 2.
5. If receiving background AD medications, the dosing regimen must be stable for at least 12 weeks prior to randomization. Chronic medications for conditions other than AD (such as depression) must be prescribed at a stable dose for at least 4 weeks prior to screening.
6. The subject has not been a cigarette smoker or chewed tobacco for at least 3 years.
7. Availability of a study partner.
8. Individuals who have participated in a clinical study with an investigational drug targeting the underlying AD process may be permitted to participate in this study.
9. Completed a COVID-19 vaccine primary series ("fully vaccinated") at least 2 weeks prior to randomization or had an unambiguous COVID-19 infection diagnosed more than 3 months before the start of the Screening Period.

Key Exclusion Criteria:

1. A neurologic condition other than AD that significantly contributes to the subject's dementia.
2. Any current primary psychiatric diagnosis other than AD if it is likely to confound cognitive assessment or ability to comply with study procedures.
3. Geriatric Depression Scale (15-item) score \> 8 (Note - a subject with a score \> 8 may continue in screening if, in the judgment of the Investigator, the elevated score is not attributed to a major depressive episode).
4. Suicidal ideation during the past 3 months or suicidal behavior during the past 12 months.
5. Alcohol or substance use disorder within 2 years of screening.
6. MRI presence of cerebral vascular or other significant pathology.
7. History of transient ischemic attack or stroke within 12 months of screening.
8. Seizure within 12 months of screening.
9. Severe head trauma or head trauma considered likely to be contributing to the subject's cognitive impairment.
10. Sleep apnea that is considered likely to be contributing to the subject's cognitive impairment.
11. Insufficiently controlled diabetes mellitus or hypertension.
12. Body mass index \< 18.5 or \> 37.5.
13. History or diagnosis of clinically significant cardiac disease.
14. Currently or previously prescribed/administered aducanumab, lecanemab, or any anti-amyloid monoclonal antibody, more than 2 doses.