A Natural History Study of Patients With Adult-Onset Leukoencephalopathy With Axonal Spheroids and Pigmented Glia (ALSP)
Conditions: ALSP
Sponsor: Vigil Neuroscience, Inc.



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PROTOCOL VERSION 5.0 SUMMARY OF CHANGES TABLE 
 
Document History 
Document 
Date 
Version 5.0 
02 Oct 2024 
Version 4.0 
03 Oct 2023 
Version 3.0 
01 Mar 2022 
Version 2.0 
29 Jul 2021 
Original (Version 1.0) 
14 May 2021 
Amendment 4: Protocol Version 5.0 (02 Oct 2024) 
Overall Rationale for Amendment  
The overall rationale for this amendment is to allow for telephone visits, at the 
investigator’s discretion, for study subjects who can no longer attend clinic visits due to 
their disease progression. This amendment also adds a provision to collect MRI data prior 
to each consenting subject’s participation in the study. 
 
Section No. and Title  
Description of Change 
Brief Rationale 
 
Cover page 
Updated Vigil Neuroscience, Inc. 
address. 
 
Ensure correct address for Vigil 
Neuroscience is listed. 
 
Sponsor Signatories 
 
Updated Sponsor Signatory to 
Petra Kaufmann, MD 
Change in Sponsor personnel 
Throughout Protocol 
Updated term “caregiver” to 
“study partner” where applicable. 
Broaden term to clarify 
expected respondent for study 
assessments 
1.3. Table 1, Schedule of 
Assessments 
4.1. Overall Design 
Addition of Telephone Visit for 
Month 18, Month 24, and Month 
30 if subject’s condition does not 
allow for in-clinic visit per 
Investigator discretion. 
Allow for partial data collection 
in subjects that are not able to 
attend in-clinic visits   
5.1. Inclusion Criteria, 10 and 13 
8.1.1. Informed Consent 
10.1.2. Informed Consent 
Process 
Updated criteria to allow study 
participation for subjects who 
meet criteria for “Definitive 
ALSP” to enroll or continue in 
study without a study partner per 
Investigator discretion  
Clarify study partner inclusion 
for subject’s participation is per 
Investigator discretion 
8.1.3., Retrospective Pre-
screening MRI (Optional) 
 
Added: “Retrospective pre-
screening MRI scans obtained 
prior to participation in a Vigil-
Sponsored study may be collected 
if available from the medical 
history of each consenting 
subject. This information will be 
used to explore the pre-study 
trajectory of MRI findings.” 
New section added to include 
the optional collection of 
retrospective pre-screening 
MRI data 
 

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TABLE OF CONTENTS 
CLINICAL PROTOCOL .....................................................................................................1 
SPONSOR SIGNATORIES ................................................................................................2 
PROTOCOL VERSION 5.0 SUMMARY OF CHANGES TABLE ..................................3 
TABLE OF CONTENTS .....................................................................................................4 
TABLE OF TABLES ..........................................................................................................7 
TABLE OF FIGURES .........................................................................................................7 
1 
PROTOCOL SUMMARY ............................................................................................8 
1.1 
Synopsis ...................................................................................................................8 
1.2 
Schema ...................................................................................................................10 
1.3 
Schedule of Assessments .......................................................................................11 
2 
INTRODUCTION ......................................................................................................14 
2.1 
Study Rationale ......................................................................................................14 
2.2 
Background ............................................................................................................14 
2.2.1 
Clinical Classification of ALSP .......................................................................14 
2.2.2 
Pathophysiology ...............................................................................................15 
2.2.3 
Prevalence and Geographical Distribution ......................................................16 
2.2.4 
Current Treatment of ALSP .............................................................................16 
2.2.5 
VGL101 ...........................................................................................................16 
2.3 
Benefit/Risk Assessment .......................................................................................17 
3 
OBJECTIVES AND ENDPOINTS ............................................................................18 
3.1 
Study Objectives ....................................................................................................18 
3.2 
Study Endpoints .....................................................................................................18 
3.2.1 
Pharmacodynamic (Biomarker) Endpoints ......................................................18 
3.2.2 
Clinical Outcome Endpoints ............................................................................18 
3.2.3 
Safety Endpoints ..............................................................................................19 
4 
STUDY DESIGN .......................................................................................................20 
4.1 
Overall Design .......................................................................................................20 
4.2 
Scientific Rationale for Study Design....................................................................20 
4.2.1 
Study Design ....................................................................................................20 
4.2.2 
Pharmacodynamic (Biomarker) Endpoints ......................................................21 
4.2.3 
Clinical Outcome Assessments ........................................................................22 
4.3 
Definition of End of Study .....................................................................................22 
5 
STUDY POPULATION .............................................................................................23 
5.1 
Inclusion Criteria ...................................................................................................23 
5.2 
Exclusion Criteria ..................................................................................................24 
5.3 
Lifestyle Considerations ........................................................................................25 
5.4 
Screen Failures .......................................................................................................25 
6 
INVESTIGATIONAL MEDICINAL PRODUCT(S) AND CONCOMITANT 
THERAPY ..................................................................................................................27 
6.1 
Investigational Medicinal Product .........................................................................27 
6.2 
Concomitant Therapy.............................................................................................27 
7 
SUBJECT DISCONTINUATION/WITHDRAWAL ................................................28 
7.1 
Subject Discontinuation/Withdrawal from the Study ............................................28 
7.2 
Lost to Follow-up ...................................................................................................28 

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8 
STUDY ASSESSMENTS AND PROCEDURES ......................................................30 
8.1 
Screening Assessments ..........................................................................................30 
8.1.1 
Informed Consent.............................................................................................30 
8.1.2 
Medical/Family History and Demographic Information .................................30 
8.1.3 
Retrospective Pre-Screening MRI (Optional) ..................................................31 
8.1.4 
Prior and Concomitant Medications/Procedures .............................................31 
8.1.5 
Documentation of CSF1R Gene Mutation .......................................................31 
8.1.6 
Clinical Global Impression – Severity of Illness (GGI-S) ...............................31 
8.1.7 
Patient Global Impression – Severity of Illness (PGI-S) .................................31 
8.1.8 
Urine Drug Screen ...........................................................................................32 
8.2 
Pharmacodynamic (Biomarker) Assessments........................................................32 
8.2.1 
Blood for NfL Analysis ...................................................................................32 
8.2.2 
Magnetic Resonance Imaging ..........................................................................32 
8.3 
Clinical Outcome Assessments ..............................................................................32 
8.3.1 
Cognitive Assessments ....................................................................................33 
8.3.2 
Motor Assessments (Ambulatory Subjects).....................................................34 
8.3.3 
Severity of Illness Assessments .......................................................................35 
8.3.4 
Other Functional and Psychiatric Assessments ...............................................36 
8.4 
Safety Assessments ................................................................................................37 
8.4.1 
Adverse Events ................................................................................................37 
8.4.2 
Physical and Neurological Examinations ........................................................38 
8.4.3 
Columbia-Suicide Severity Rating Scale (C-SSRS) ........................................38 
8.4.4 
COVID-19 Assessments and Testing ..............................................................38 
8.4.5 
Pregnancy Testing ............................................................................................39 
8.5 
Optional CSF Biomarker Sub-study ......................................................................39 
8.6 
Survival Assessment ..............................................................................................39 
9 
STATISTICAL CONSIDERATIONS .......................................................................39 
9.1 
Sample Size Determination....................................................................................39 
9.2 
Analysis Sets ..........................................................................................................40 
9.3 
Statistical Analysis .................................................................................................40 
9.3.1 
Disposition and Demographics ........................................................................40 
9.3.2 
Prior and Concomitant Medications ................................................................40 
9.3.3 
Clinical Outcome and Biomarker Analyses .....................................................40 
9.3.4 
Safety Analyses ................................................................................................40 
10 SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS ..................................................................................................41 
10.1 
Appendix 1: Regulatory, Ethical, and Study Oversight Considerations ................41 
10.1.1 
Regulatory and Ethical Considerations ............................................................41 
10.1.2 
Informed Consent Process ...............................................................................41 
10.1.3 
Data Protection.................................................................................................42 
10.1.4 
Dissemination of Clinical Study Data..............................................................42 
10.1.5 
Source Documents ...........................................................................................43 
10.1.6 
Study and Site Closure .....................................................................................43 
10.1.7 
Publication Policy ............................................................................................44 
10.2 
Appendix 2: Definitions and Procedures for Recording, Evaluating, 
Follow-up, and Reporting of Adverse Events and Serious Adverse Events ..........45 

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10.2.1 
Definition of Adverse Event ............................................................................45 
10.2.2 
Serious Adverse Event .....................................................................................46 
10.2.3 
Recording and Follow-up of Adverse Events and/or Serious Adverse 
Events ...............................................................................................................47 
10.2.4 
Reporting of Serious Adverse Events ..............................................................49 
10.3 
Appendix 3: Criteria for ALSP Based on Magnetic Resonance Imaging 
(MRI)/Computed Tomography (CT) .....................................................................50 
10.4 
Appendix 4: Abbreviations and Definitions ..........................................................52 
10.5 
Appendix 5: Protocol Amendment History ...........................................................54 
10.5.1 
Amendment 1: Protocol Version 2.0 (29 Jul 2021) .........................................54 
10.5.2 
Amendment 2: Protocol Version 3.0 (22 Mar 2022) .......................................58 
10.5.3 
Amendment 3: Protocol Version 4.0 (03-Oct-2023) .......................................61 
11 REFERENCES ...........................................................................................................67 
INVESTIGATOR SIGNATURE PAGE ...........................................................................71 
 

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TABLE OF TABLES 
Table 1 
Schedule of Assessments ...........................................................................12 
 
TABLE OF FIGURES 
Figure 1 
Study Schema.............................................................................................11 
Figure 2 
Characteristic Brain Magnetic Resonance Imaging (MRI)/Computed 
Tomography (CT) Findings in Patients With adult-Onset 
Leukoencephalopathy With Axonal Spheroids and Pigmented Glia 
(ALSP) .......................................................................................................50 
 

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1 PROTOCOL SUMMARY 
1.1 
Synopsis 
Protocol Title  
A Natural History Study of Patients with Adult-Onset Leukoencephalopathy with Axonal 
Spheroids and Pigmented Glia (ALSP) 
Short Title  
Illuminate 
Study Rationale  
Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a 
rare, rapidly progressing, genetic, neurodegenerative disease for which no definitive 
treatment options and limited information on the natural history of the disease are 
available. The structural, genetic, and neuropathophysiological abnormalities of ALSP 
lead to the onset of neurologic symptoms, such as moderate to severe motor and 
neuropsychiatric impairments. Vigil Neuroscience is developing VGL101, a monoclonal 
antibody of triggering receptor on myeloid cells 2 (TREM2) agonist, for the treatment of 
ALSP. This natural history study will collect data to contribute to the development of 
future novel therapies, including VGL101, that focus on the neuropathophysiological 
features that underlie ALSP and that are essential to reverse, delay, or stop progression of 
this debilitating disorder. 
Study Objectives 
The objectives of the study are: 
• To understand the phenotypic heterogeneity and phenotype/genotype correlation and 
natural history of ALSP. 
• To develop and evaluate biomarkers for assessing disease progression in patients with 
ALSP. 
• To create the foundation for a future synthetic control arm and provide run-in data for 
patients who qualify for interventional studies. 
Study Endpoints 
Pharmacodynamic (Biomarker) Endpoints 
• Change from Baseline to Months 6, 12, 24, and 36 in neurofilament light chain (NfL) 
in blood  
• Change from Baseline to Months 12, 24, and 36 in NfL, cytokine(s), soluble TREM2, 
and soluble CSF1R in cerebral spinal fluid (CSF) in subjects who provide informed 
consent to participate in an optional CSF Biomarker Sub-study 

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• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in structural and 
volumetric magnetic resonance imaging (MRI) 
Clinical Outcome Endpoints 
Cognitive Assessments 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Montreal Cognitive 
Assessment (MoCA) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Clinical Dementia 
Rating Scale plus National Alzheimer’s Coordinating Center-Frontotemporal Lobar 
Degeneration (CDR®+NACC-FTLD) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Brief Assessment of 
Cognition (BAC) battery 
Motor Assessments (Ambulatory Subjects) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the 2-Minute Walk Test 
(2MWT) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Timed Up and Go 
(TUG) test 
Severity of Illness Assessments 
• Clinical Global Impression – Change (CGI-C) responses at Months 6, 12, 18, 24, 30, 
and 36 
• Patient Global Impression - Change (PGI-C) responses at Months 6, 12, 18, 24, 30, 
and 36 
Other Functional and Psychiatric Assessments 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Functional Activities 
Questionnaire (FAQ) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Neuropsychiatric 
Inventory – 12-Item Version (NPI-12) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Cortical Basal 
ganglia Functional Scale (CBFS) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Zarit Burden 
Interview 
Safety Endpoints 
• Adverse events (AEs) 
• Columbia-Suicide Severity Rating Scale (C-SSRS) 
Brief Summary 
This is a non-interventional, prospective, multicenter, observational, natural history study 
of patients with ALSP and asymptomatic carriers of CSF1R gene mutations, the causative 
mutation for ALSP. Potential study participants will be screened for study eligibility. 

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Individuals who satisfy the study inclusion and exclusion criteria and who provide 
written informed consent will be enrolled in the study and followed for up to 36 months.  
Clinic visits to assess disease status will be conducted at Screening/Baseline and at 
Months 6, 12, 18, 24, 30, and 36. Each clinic visit will include clinical assessments 
(cognitive, motor, functional, psychiatric, severity of illness, and study partner burden 
assessments) and imaging studies. Blood for biomarker analysis will be collected at 
Screening/Baseline and at Months 6, 12, 18, 24, 30, and 36. Adverse events and 
concomitant medications and procedures will be recorded throughout the 36-month 
study.  
An optional sub-study to evaluate levels of biomarkers in cerebrospinal fluid (CSF) is 
also included in this study and will be conducted at select study sites. A CSF sample will 
be obtained at Screening/Baseline and at Months 12, 24, and 36 from subjects who 
provide informed consent to participate in the optional CSF Biomarker Sub-study. 
Subjects who, in the discretion of the investigator, may be eligible for a VGL101 clinical 
study may be discontinued from this study at any time. For subjects who discontinue 
from this study to enroll in a VGL101 clinical study, all procedures, except the MRI, 
blood biomarker sampling, and CSF collection (for subjects in the CSF Sub-study), will 
be collected once for the Early Termination (ET) Visit of this study and for the Screening 
or Baseline Visit of the VGL101 clinical study and will be analyzed as part of both 
studies. If CSF biomarker collection is not included at the Screening or Baseline Visit of 
the VGL101 clinical study, CSF biomarker collection will be performed at the ET Visit 
of this study. 
Number of Subjects 
Approximately 60 subjects are planned for enrollment. 
The study will enroll subjects with prodromal or definitive ALSP. Prodromal ALSP is 
defined as ALSP that satisfies the radiologic, but not the full clinical, criteria (see 
Section 5.1, Inclusion Criteria). At sponsor discretion, enrollment of individuals with 
prodromal ALSP may be discontinued. 
Treatment Groups and Duration 
No study intervention will be administered. Subjects will be followed for up to 24 months 
(subjects who complete the study before implementation of Amendment 3) or 36 months 
(subjects who complete the study after implementation of Amendment 3). 
1.2 
Schema 
An overview of the study design is presented in Figure 1. 

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Figure 1 
Study Schema 
 
1.3 
Schedule of Assessments 
The schedule of assessments is shown in Table 1. At each clinic visit, whenever feasible, 
the cognitive and motor assessments should be prioritized. Study visits should be 
scheduled at approximately the same time each day to ensure that scales are completed at 
consistent times during the study. 

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Abbreviations: 2MWT = 2-Minute Walk Test, ALSP = adult-onset leukoencephalopathy with axonal spheroids and pigmented glia, BAC = Brief Assessment of Cognition, CBFS = Cortical 
Basal ganglia Functional Scale, CDR®+NACC-FTLD = Clinical Dementia Rating Scale plus National Alzheimer’s Coordinating Center-Frontotemporal Lobar Degeneration, CGI-
C = Clinical Global Impression - Change, CGI-S = Clinical Global Impression – Severity of Illness, CSF = cerebral spinal fluid, CSF1R = colony-stimulating factor 1 receptor, C-
SSRS = Columbia-Suicide Severity Rating Scale, ET = early termination, FAQ = Functional Activities Questionnaire, LP = lumbar puncture, MoCA = Montreal Cognitive Assessment, 
NPI-12 = Neuropsychiatric Inventory – 12-Item Version, PGI-C = Patient Global Impression - Change, PGI-S = Patient Global Impression - Severity of Illness, SOC = standard of care, 
TUG = Timed Up and Go, WOCBP = women of childbearing potential. 
 
a. 
At each clinic visit, whenever feasible, the cognitive and motor assessments should be prioritized. Study visits should be scheduled at approximately the same time 
each day to ensure that scales are completed at consistent times during the study. 
b. 
Screening/Baseline assessments may be completed at more than 1 study visit; all assessments must be completed within 28 days. 
c. 
Subjects who permanently discontinue from the study before completing the Month 36 Visit will be required to return for an Early Termination (ET) Visit. 
d. 
Written informed consent must be obtained before any study related procedures are conducted. 
e. 
All prescription and over-the-counter medications that have been taken during the 30 days before Screening/Baseline (i.e., Day 1) through the last study visit will be 
documented. A complete history of medications taken for the treatment of ALSP will be collected. Prior medical procedures will also be recorded. 
f. 
COVID-19 assessments will be performed per local guidelines and standard of care at the site. 
g. 
The “Baseline Screening” (lifetime and last 6 months) C-SSRS form will be completed at Screening to determine eligibility. The “Since Last Visit” C-SSRS form 
will be completed at Months 6, 12, 18, 24, 30, and 36. 
h. 
All adverse events/serious adverse events will be monitored until resolution or stabilization. 
i. 
Attempts will be made to determine the survival status (alive or deceased) of any subject who fails to return for the final visit or who discontinues from the study 
before completing the 24-month (subjects who withdraw from the study before implementation of Amendment 3) to 36-month (subjects who withdraw from the 
study after implementation of Amendment 3) observation period. Study staff will contact the subject or the subject’s study partner by telephone to determine 
survival status 24 or 36 months, respectively, after the date of the subject’s Screening Visit or at the end of the study, whichever occurs sooner. 
j. 
Local blood coagulation panel will need to be completed prior to lumbar puncture (LP) for patients that volunteer to participate in the optional CSF sample 
collection. 
k. 
Biomarkers in CSF will be determined in subjects who provide informed consent to participate in an optional CSF Biomarker Sub-study.  
l. 
The MRI scans may be obtained ±2 days before the scheduled visit. 
m. At the investigator’s discretion, the CDR®+NACC-FTLD may not need to be administered if there are no signs or symptoms of cognitive impairment (i.e., normal 
score on the MoCA) or if the subject does not have astudy partner who has provided informed consent for the study. 
n. 
The FAQ, NPI-12, and Zarit Burden Interview will not be completed if the subject does not have a study partner who has provided informed consent for the study. 
o. 
For subjects who participate in the CSF Sub-study and who discontinue from this study to enroll in a VGL101 clinical study, CSF biomarker collection will be 
performed at the Screening or Baseline Visit of the VGL101 clinical study and will be analyzed as part of both studies. If CSF collection is not included at the 
Screening or Baseline Visit of the VGL101 clinical study, CSF biomarker collection will be done at the ET Visit of this study. 
p. 
For subjects who discontinue from this study to enroll in a VGL101 clinical study, blood biomarker collection will be performed once for both the ET Visit of this 
study and the Screening/Baseline Visit of the VGL101 study and will be analyzed as part of both studies. 
q. 
For subjects who discontinue from this study to enroll in a VGL101 clinical study, an MRI will be collected once for both the ET Visit of this study and the 
Screening/Baseline Visit of the VGL101 clinical study and will be analyzed as part of both studies. 
r. 
If a subject is unable to attend on-site visits due to a decline in his/her condition and the subject is willing to remain in the study, telephone visits may be conducted 
at Month 18, Month 24, and Month 30 in lieu of clinic visits at the discretion of the Investigator. All other visits should occur in clinic. Telephone visits will also 
require participation of the study partner. 

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2 INTRODUCTION 
2.1 
Study Rationale 
Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a 
rare, rapidly progressing, genetic, neurodegenerative disease for which no definitive 
treatment options and limited information on the natural history of the disease are 
available. The structural, genetic, and neuropathophysiological abnormalities of ALSP 
lead to the onset of neurologic symptoms, such as moderate to severe motor and 
neuropsychiatric impairments. Vigil Neuroscience is developing VGL101, a monoclonal 
antibody of triggering receptor on myeloid cells 2 (TREM2) agonist, for the treatment of 
ALSP. This natural history study will collect data to contribute to the development of 
future novel therapies, including VGL101, that focus on the neuropathophysiological 
features that underlie ALSP and that are essential to reverse, delay, or stop progression of 
this debilitating disorder. 
2.2 
Background 
2.2.1 
Clinical Classification of ALSP 
ALSP is a fatal, rare, inherited and rapidly progressing neurologic disorder with no 
definitive treatment options. ALSP is clinically delineated by 3 main groups of 
symptoms: impaired cognition, neuropsychiatric abnormalities, and motor dysfunction 
(Sundal & Wszolek, 2017; Konno et al, 2018; Oosterhoff et al, 2018; Tian et al, 2019; 
Kempthorne et al, 2020; Zhan et al, 2020; Zhou et al, 2020). The mean age for onset of 
symptoms is primarily in the 4th decade but can range from early adulthood to the 8th 
decade (Sundal & Wszolek, 2017). Symptoms tend to be present at an earlier age in 
women (40 years) than in men (47 years) (Konno et al, 2017b).  
Signs and symptoms tend to be nonspecific in the early stages of ALSP and may be 
difficult to distinguish from other inherited autosomal neurological disorders. Early 
symptoms include cognitive impairment (59%); neuropsychiatric symptoms (44%), 
including anxiety, depression, apathy, indifference, abulia, irritability, disinhibition, and 
distraction; motor dysfunction (38%), including parkinsonian symptoms, gait 
disturbances, and spasticity; speech difficulty (19%); and other symptoms (8%), such as 
stroke-like episodes, sensory dysfunction, dizziness, fatigue, and epilepsy (Konno et al, 
2017b). 
Progression of the neuropsychiatric aspects and motor symptoms of ALSP can lead to 
further cognitive decline and loss of mobility. Additional progressive symptoms involve 
cortical disturbances (aphasia, agraphia, apraxia, etc.), pyramidal signs (hyperreflexia, 
spasticity, and Babinski signs), bulbar signs (dysarthria, dysphagia, and slurred speech), 
cerebellar abnormalities (ataxia, dysmetria, intention tremor, and gait disturbances), and 
seizures. In the final stages of the disorder, loss of speech and voluntary movements, 
confinement to bed, and a vegetative state are evident. Infections and pneumonia often 
result in death (Sundal & Wszolek, 2017).  

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Progression of the disorder from onset of symptoms to death varies from 2 to >30 years 
(mean, 6-8 years) (Sundal et al, 2012; Konno et al, 2017b). As there are no current 
regulatory-approved therapies that address the etiology and progression of ALSP, the 
prognosis is ominous, with a substantial burden of devastating symptoms that elicit 
deterioration of quality of life and a shortened life span. 
2.2.2 
Pathophysiology 
ALSP is primarily inherited as an autosomal dominant disorder with colony-stimulating 
factor 1 receptor (CSF1R) gene mutations (Sundal & Wszolek, 2017; Du et al, 2019; 
Leng et al, 2019). At least 98 different CSF1R mutations have been identified in more 
than 200 cases worldwide. There is no obvious correlation of genotype and phenotype; 
family members with identical CSF1R gene mutations do not share the same clinical 
phenotype (Sundal & Wszolek, 2017; Konno et al, 2018). Although de novo mutations of 
CSF1R have been reported, they are less common (Rademakers et al, 2011). Penetrance 
of ALSP is high, but incomplete, due to de novo mutations and genetic mosaicism (Karle 
et al, 2013; Sundal et al, 2015; Konno et al, 2017b; Konno et al, 2018).  
CSF1R gene mutations are specific diagnostic features of patients with ALSP. As 
phosphatase and kinase proteins associated with the CSF1R gene regulate functions of 
macrophages, microglia, and neuronal pathways, disturbances of these proteins due to 
gene mutation are implicated in the neuropathophysiology of ALSP (Rademakers et al, 
2011; Lynch et al, 2016; Kraya et al, 2019). The strong link between CSF1R mutations 
and pathologic microglia has resulted in further classification of CSF1R-related 
leukoencephalopathy as a central nervous system (CNS) primary microgliopathy (Han et 
al, 2020). 
Histopathologic evaluation (light and electron microscopy) of brain tissue from biopsies 
and autopsies and brain imaging of patients with ALSP display marked alterations. One 
of the principal neuropathologies consists of vacuolated and demyelinated white matter 
that is found primarily within the corpus callosum, pyramidal tracts, and periventricular 
region of the frontal and parietal lobes. White matter degeneration is often associated 
with deteriorating neurons and axons due to spheroids that are positive for 
neurofilaments, amyloid, and ubiquitin. The axonal pathology is accompanied by 
macrophages that are engorged with lipid and myelin. Other characteristic 
neuropathologies of ALSP are deformed astrocytes and pigmented (iron or lipofuscin) 
microglia cells that decrease in function and number with progression of the disorder 
(Sundal & Wszolek, 2017; Konno et al, 2018; Tian et al, 2019; Kempthorne et al, 2020; 
Zhan et al, 2020; Zhou et al, 2020). 
Abnormal levels of cytoskeletal proteins, such as neurofilament light chain (NfL), tau, 
and glial fibrillary acid, were identified as potential biomarkers in cases of ALSP. A 
recent case control study demonstrated that NfL protein levels in serum and cerebrospinal 
fluid (CSF) were markedly higher in symptomatic and presymptomatic patients with 
ALSP and CSF1R mutations than in healthy control subjects or in patients with multiple 
sclerosis (Hayer et al, 2018). Elevated levels of NfL in blood and CSF are believed to be 

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indicative of neuron death and axonal deterioration in several neurodegenerative 
disorders. 
2.2.3 
Prevalence and Geographical Distribution 
Mendelian adult-onset leukodystrophies are a spectrum of rare, chronic, complex, and 
progressive neurologic disorders. Worldwide incidence of these disorders has been 
reported to be 5 per 100,000 (Sassi et al, 2018), with a total prevalence of 300 cases per 
million (Ahmed et al, 2014). If 10% to 25% of these cases are patients with 
CSF1R-related ALSP (Sundal & Wszolek, 2017), the global prevalence of CSF1R-related 
ALSP is estimated to be in the range of 231,918 to 579,796. Although still rare, 
genetically diagnosed individuals with CSF1R-related ALSP have been increasingly 
recognized around the world (United States, Canada, United Kingdom, Germany, the 
Netherlands, Croatia, Italy, Greece, Norway, Sweden, Saudi Arabia, China, Taiwan, 
South Korea, and Japan) since 2012. It is apparent that this disease has global distribution 
and many patients may still be underdiagnosed (Konno et al, 2018).  
2.2.4 
Current Treatment of ALSP 
Currently, there are no pharmacotherapies that can alter the course of ALSP. Patients are 
treated with a variety of medications to ameliorate clinical symptoms and improve quality 
of life. The medications include anti-Parkinson’s disease drugs, cholinesterase inhibitors, 
antidepressants, antipsychotics, muscle relaxants, and antiepileptics. 
Hematopoietic stem cell therapy (HSCT) has been used in small number of patients with 
variable results (Eichler et al, 2016; Mochel et al, 2019; Gelfand et al, 2020). 
Stabilization of cognition deficits and motor function, as well MRI lesions, have been 
reported up to 2 years after HSCT. Clinical trials in larger number of patients are 
currently ongoing to further explore the value of HSCT in the treatment of ALSP, 
especially in view of the significant risks associated with HSCT. 
Physical therapy is recommended to positively impact motor dysfunction and to maintain 
some activities of daily living. Professional counseling is important to educate the patient 
and relatives on symptoms and progression of ALSP and to ensure a supportive family 
structure. Genetic counseling of patients and relatives is also necessary to address 
insecurity associated with inheritance of ALSP (Sundal & Wszolek, 2017; Konno et al, 
2018; Zhan et al, 2020). 
2.2.5 
VGL101 
ALSP is a rare, progressive, debilitating disorder that affects relatively young individuals 
and that causes a major impact on the life of patients and their families. Patients with 
ALSP lose employment, income, and require costly long-term care. Therefore, ALSP 
represents a major unmet medical need. Safe and effective novel therapies that address 
the etiology of ALSP and that can slow, halt, or even reverse the progression of this 
life-threatening disorder are urgently needed. 

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Vigil Neuroscience is developing VGL101, a monoclonal antibody TREM2 agonist, for 
the treatment of ALSP. The response of microglial cells to changes in the environment of 
the CNS is activated through TREM2 and its associated protein kinase complex, DAP12 
(Konishi & Kiyama, 2018). The TREM2/DAP12 signal functions as the primary 
regulator that transforms microglia from a homeostatic to a neural disease-associated 
state and produces an anti-inflammatory response and neurotrophic factors to protect 
injured neurons and to enable nerve tissue regeneration. The activation of TREM2 by 
VGL101 is expected to slow disease progression and enhance the neural tissue repair 
mechanisms regulated by microglia. 
This natural history study will provide information on the biomarkers and clinical 
outcome assessments that will allow for an assessment of therapeutic agents, such as 
VGL101, in therapeutic trials of ALSP. 
2.3 
Benefit/Risk Assessment 
This natural history study may benefit patients with ALSP and carriers of the CSF1R 
mutation by facilitating the understanding and evaluation of the current standard-of-care 
practice and identifying ways to improve patient care. The subjects who participate in this 
study will receive no direct benefit other than thorough medical assessments, which will 
provide detailed information on their disease status. The risks of participation in the study 
are primarily those associated with collection of blood samples for biomarker analyses 
and lumbar puncture for subjects who participate in the optional CSF Biomarker Sub-
study. 

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3 OBJECTIVES AND ENDPOINTS 
3.1 
Study Objectives 
The objectives of the study are: 
• To understand the phenotypic heterogeneity and phenotype/genotype correlation and 
natural history of ALSP. 
• To develop and evaluate biomarkers for assessing disease progression in patients with 
ALSP. 
• To create the foundation for a future synthetic control arm and provide run-in data for 
patients who qualify for interventional studies. 
3.2 
Study Endpoints 
3.2.1 
Pharmacodynamic (Biomarker) Endpoints 
• Change from Baseline to Months 6, 12, 24, and 36 in NfL in blood 
• Change from Baseline to Months 12, 24, and 36 in NfL, cytokine(s), soluble TREM2, 
and soluble CSF1R in CSF in subjects who provide informed consent to participate in 
an optional CSF Biomarker Sub-study 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in structural and 
volumetric magnetic resonance imaging (MRI) 
3.2.2 
Clinical Outcome Endpoints 
3.2.2.1 
Cognitive Assessments 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Montreal Cognitive 
Assessment (MoCA) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Clinical Dementia 
Rating Scale plus National Alzheimer’s Coordinating Center-Frontotemporal Lobar 
Degeneration (CDR®+NACC-FTLD) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Brief Assessment of 
Cognition (BAC) battery 
3.2.2.2 
Motor Assessments (Ambulatory Subjects) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the 2-Minute Walk Test 
(2MWT) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Timed Up and Go 
(TUG) test 

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3.2.2.3 
Severity of Illness Assessments 
• Clinical Global Impression – Change (CGI-C) responses at Months 6, 12, 18, 24, 30, 
and 36 
• Patient Global Impression - Change (PGI-C) responses at Months 6, 12, 18, 24, 30, 
and 36 
3.2.2.4 
Other Functional and Psychiatric Assessments 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Functional Activities 
Questionnaire (FAQ) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Neuropsychiatric 
Inventory – 12-Item Version (NPI-12) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Cortical Basal 
ganglia Functional Scale (CBFS) 
• Change from Baseline to Months 6, 12, 18, 24, 30, and 36 in the Zarit Burden 
Interview 
3.2.3 
Safety Endpoints 
• Adverse events (AEs) 
• 
Columbia-Suicide Severity Rating Scale (C-SSRS) 

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4 STUDY DESIGN 
4.1 
Overall Design 
This is a non-interventional, prospective, multicenter, observational, natural history study 
of patients with ALSP and asymptomatic carriers of CSF1R gene mutations, the causative 
mutation for ALSP. Potential study participants will be screened for study eligibility. 
Individuals who satisfy the study inclusion and exclusion criteria and who provide 
written informed consent will be enrolled in the study and followed for up to 36 months.  
Clinic visits to assess disease status will be conducted at Screening/Baseline and at 
Months 6, 12, 18, 24, 30, and 36. Each clinic visit will include clinical assessments 
(cognitive, motor, functional, psychiatric, severity of illness, and study partner burden 
assessments) and imaging studies. Blood for biomarker analysis will be collected at 
Screening/Baseline and at Months 6, 12, 18, 24, 30, and 36. Adverse events (AEs) and 
concomitant medications and procedures will be recorded throughout the 36-month 
study.  
An optional sub-study to evaluate levels of biomarkers in cerebrospinal fluid (CSF) is 
also included in this study and will be conducted at select study sites. A CSF sample will 
be obtained at Screening/Baseline and at Months 12, 24, and 36 from subjects who 
provide informed consent to participate in the optional CSF Biomarker Sub-study. 
Given the nature of ALSP, subjects may progress while on study. If a subject is unable to 
attend on-site visits due to a decline in his/her condition and the subject is willing to 
remain in the study, telephone visits may be conducted at Month 18, Month 24, and 
Month 30 in lieu of clinic visits at the discretion of the Investigator (refer to schedule of 
assessments, Table 1) All other visits should occur in clinic. Telephone visits will also 
require participation of the study partner.  
Subjects who, in the discretion of the investigator, may be eligible for a VGL101 clinical 
study may be discontinued from this study at any time. For subjects who discontinue 
from this study to enroll in a VGL101 clinical study, all procedures, except the MRI, 
blood biomarker sampling, and CSF collection (for subjects in the CSF Sub-study), will 
be collected once for the Early Termination (ET) Visit of this study and for the Screening 
or Baseline Visit of the VGL101 clinical study and will be analyzed as part of both 
studies. If CSF biomarker collection is not included at the Screening or Baseline Visit of 
the VGL101 clinical study, CSF biomarker collection will be performed at the ET Visit 
of this study.  
4.2 
Scientific Rationale for Study Design 
4.2.1 
Study Design 
The open-label design is an appropriate design for a non-interventional study in which 
the natural course of the disease will be followed. The information that is collected in this 
study will be used to evaluate biomarkers for assessing disease progression in patients 

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with ALSP and, thereby, will contribute to the development of future novel therapies that 
focus on the neuropathophysiological features that underlie ALSP and that are essential 
to reverse, delay, or stop progression of this debilitating disorder. 
4.2.2 
Pharmacodynamic (Biomarker) Endpoints 
Changes in NfL protein in blood (all subjects) and CSF (subjects who participate in the 
optional CSF Biomarker Sub-study) will be evaluated as potential 
neuropathophysiological biomarkers for ALSP. Studies have shown that NfL protein 
levels are markedly increased in the serum and CSF of patients with ALSP (Hayer et al, 
2018), as well as in the blood and CSF of patients with other neurodegenerative diseases, 
including multiple sclerosis, amyotrophic lateral sclerosis (ALS), and frontal lobe 
dementia (Byrne et al, 2017; Niemelä et al, 2017; Merluzzi et al, 2019; Bäckström et al, 
2020; Delaby et al, 2020). Thus, reduction in NfL levels may be predictive of clinical 
improvements and may serve as a surrogate endpoint in therapeutic studies of orphan 
neurodegenerative indications, including ALSP. 
The response of microglial cells to changes in the environment of the central nervous 
system is activated through TREM2 and its associated protein kinase complex, DAP12 
(Konishi & Kiyama, 2018). The TREM2/DAP12 signal functions as the primary 
regulator that transforms microglia from a homeostatic to a neural disease-associated 
state and produces an anti-inflammatory response and neurotrophic factors to protect 
injured neurons and enable nerve tissue regeneration. Animal and human genetic studies 
have demonstrated that microglia without TREM2 or with mutated TREM2 do not 
convert to an activated stage and, subsequently, lead to development and/or progression 
of neurologic disorders. Furthermore, animal models of Parkinson’s disease, Alzheimer’s 
disease, ALS, and demyelinating disease display dysregulation of TREM2/DAP12 
signals that promotes pathogenesis of neurodegeneration (Konishi & Kiyama, 2018). 
TREM2 in CSF is a marker of CNS microglia activity. The utility of TREM2 as a target 
engagement biomarker warrants further evaluation; therefore, soluble TREM2 will be 
included as an exploratory biomarker in early clinical trials of VGL101. 
CSF1R gene mutations are specific diagnostic features of patients with ALSP. As 
phosphatase and kinase proteins associated with the CSF1R gene regulate functions of 
macrophages, microglia, and neuronal pathways, disturbances of these proteins due to 
gene mutations, may also be implicated in the neuropathophysiology of ALSP 
(Rademakers et al, 2011; Lynch et al, 2016; Kraya et al, 2019). Additional research and 
case studies will likely confirm 1 or more of the above protein markers of neuronal, 
axonal, and glial cell damage and death as a meaningful surrogate endpoint for future 
novel therapies for ALSP. Thus, soluble CSF1R levels in CSF in an optional CSF 
Biomarker Sub-study. In addition to soluble CSF1R and soluble TREM2, measurement 
of cytokine levels will be included as an exploratory biomarker in CSF in an optional 
CSF Biomarker Sub-study. Cytokine assays may include, but are not limited to, the 
following: interferon gamma-inducible protein 10 (IP-10) and monocyte chemoattractant 
protein-1 (MCP-1), which have been proposed to serve as additional markers of CNS 
immune dysregulation. 

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Magnetic resonance imaging of the brains of patients with ALSP reveals high signaling 
of white matter disfigurement with darkened fat (T2-weighted) and fluid-attenuated 
inversion recovery (FLAIR) (Van Gerpen et al, 2008; Sundal et al, 2012; Bender et al, 
2014, Konno et al, 2014; Konno et al, 2017a; Konno et al, 2017b). The high signaling is 
generally confined to the bifrontal or bifrontal parietal regions of the brain in the deep, 
subcortical, and periventricular areas, as well as in the corpus callosum and corticospinal 
tracts. Early onset white matter lesions are scattered and localized but develop confluency 
with progression of the disorder. Images also confirm enlarged ventricles consistent with 
white matter lesions and cerebral atrophy. Although atypical, MRI with 
diffusion-weighted imaging (DWI) has shown high signaling in the bipyramidal tracts 
that connect brain to spinal cord in a patient with ALSP (Li et al, 2020). Magnetic 
resonance imaging scans will be obtained throughout the study to monitor disease 
progression. 
4.2.3 
Clinical Outcome Assessments 
The structural, genetic, and neuropathophysiological abnormalities of ALSP lead to the 
onset of neurologic symptoms, such as moderate to severe motor and neuropsychiatric 
impairments (Sundal & Wszolek, 2017; Konno et al, 2018; Oosterhoff et al, 2018; Tian et 
al, 2019; Kempthorne et al, 2020; Zhan et al, 2020; Zhou et al, 2020). The battery of 
cognitive, motor, and psychiatric scales that will be used in this study have been selected 
to assess the effects of ALSP on the core symptoms of the disease over time.  
4.3 
Definition of End of Study 
The end of the study is defined as the last date on which the last subject completes the 
Month 36/ET Visit. 

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5 STUDY POPULATION 
5.1 
Inclusion Criteria 
Subjects who meet all of the following criteria are eligible for the study: 
General and Administrative 
1. Male or female subjects aged ≥18 years on the day the informed consent form (ICF) 
is signed. 
2. Subjects who are able, in the opinion of the investigator, to understand the nature of 
the study and to comply with the protocol requirements, including scheduled visits, 
blood sampling, and other study procedures, or who have a study partner or legal 
guardian who can understand and assist the subject in complying with the protocol 
requirements. 
3. Subjects who are willing and able to refrain from use of any prohibited 
medication/treatments that are not permitted by the protocol throughout the study 
period. 
4. Subjects who receive approval of sponsor medical personnel as to final suitability for 
the study. 
Inclusion Criteria – Subjects with “Definitive ALSP” 
5. Subjects who have documentation of a gene mutation in the CSF1R gene (prior to 
enrollment). 
6. Subjects who fulfill both of the following criteria (a and b): 
a. More than two findings of clinical signs or symptoms in any of the 
following categories: 
i. Cognitive impairment or psychiatric problem 
ii. Pyramidal signs on neurological examination 
iii. Extrapyramidal signs, such as rigidity, tremor, abnormal gait, or 
bradykinesia 
iv. Epilepsy 
b. MRI findings consistent with ALSP: specifically, bilateral cerebral white 
matter lesions with or without thinning of the corpus callosum (Konno et 
al, 2018; Appendix 3, Section 10.3). 
NOTE: Subjects with other causes of leukoencephalopathy, including vascular 
dementia, multiple sclerosis, or leukodystrophy (e.g., adrenoleukodystrophy, 
Krabbe disease, metachromatic leukodystrophy), will be excluded. 
7. Subjects who, in the investigator’s opinion, have demonstrated clinical progression 
of their ALSP within the past year. 
8. Subjects who have a score of ≥12 on the MoCA. 
9. Subjects who are ambulatory with or without aids (cane, crutches, etc.) or, if 
restricted to a wheelchair, are still able to wheel self, transfer in and out of 
wheelchair, and walk up to 5 meters with or without aid. 

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NOTE: Subjects that are non-ambulatory for reasons other than progression of 
ALSP may be enrolled. 
10. Subjects who meet the criteria for definitive ALSP must have a designated study 
partner (i.e. caregiver) who spends at least 4 hours per week with them. The study 
partner must be able and willing to assist the subject in complying with the study 
requirements, be able to provide information during study visits, and be willing to 
sign a study partner ICF. Subjects who do not have a study partner may be enrolled 
at the investigator’s discretion if they are able to comply with protocol requirements.  
Inclusion Criterion – Subjects with “Prodromal ALSP” 
11. Subjects who have documentation of a gene mutation in CSF1R gene (prior to 
enrollment). 
12. MRI findings consistent with ALSP: specifically, bilateral cerebral white matter 
lesions with or without thinning of the corpus callosum (Konno et al, 2018; 
Appendix 3, Section 10.3). Prodromal subjects may have none or up to and including 
2 ALSP-related clinical signs or symptoms (i.e., they do not meet the clinical criteria 
outlined in 6a as “more than two”). 
13. Subjects who meet the criteria for prodromal ALSP and who, at later study visits, 
meet the criteria for definitive ALSP should have a designated study partner for 
subsequent study visits who spends at least 4 hours per week with them unless 
otherwise approved by the sponsor and/or medical monitor. The study partner must 
be able and willing to assist the subject in complying with the study requirements, be 
able to provide information during study visits, and be willing to sign a study partner 
ICF. Subjects who do not have a study partner may continue the study at the 
investigator’s discretion if they are able to comply with protocol requirements. 
Informed Consent 
14. Subjects who are capable of providing written informed consent, including signing 
and dating the ICF, or who have a study partner/legal guardian who can provide 
written informed consent (with subject assent). 
Screening Assessments 
15. Woman of childbearing potential must have a negative urine pregnancy test at 
Screening/Baseline. 
5.2 
Exclusion Criteria 
Subjects will be excluded from the study for any of the following reasons: 
Medical Conditions 
1. Subjects with any neurological or psychiatric diseases that can produce cognitive, 
motor, or behavioral impairment similar to ALSP, including, but not limited to, 
Alzheimer’s disease, frontotemporal dementia, ALS, stroke, Huntington disease, 
multiple sclerosis, Parkinson’s disease, and Down syndrome, or with active 
alcohol/drug abuse. 
2. Subjects with any concurrent diagnosis that may confound neuropsychological 
testing (e.g., hearing impairment, visual impairment). 

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3. Subjects with any concurrent diagnosis that may confound ambulation 
measurements (e.g., amputee). 
4. Subjects with contraindications for undergoing a lumbar puncture, such as 
bleeding disorders, increased intracranial pressure, or abnormal spinal anatomy. 
NOTE: Only for subjects who participate in the optional CSF Biomarker 
Sub-study. 
5. Subjects who are unable to undergo MRI (e.g., implants not compatible for MRI, 
claustrophobia, inability to remain still that will prevent acquisition of a good 
quality scan).  
6. Female subjects who are pregnant, planning pregnancy in the next 12 months, or 
breastfeeding. 
7. Subjects who are at significant risk of suicidal or violent behavior, in the opinion 
of the investigator. If a subject answers “yes” to the Question 4 or 5 on the 
C-SSRS, a risk assessment should be done by a qualified healthcare professional 
to assess whether it is safe for the subject to participate in the study. 
8. Subjects with a current history of major medical illness, such as renal failure, 
congestive heart failure, or advanced pulmonary disease, that could put the 
subject at additional risk if participating in the study. 
9. Subjects with a history of cancer that required active treatment in the last 5 years, 
with the exception of in situ cervical cancer and basal cell carcinoma of the skin.  
10. Subjects with any condition or situation that, in the opinion of the investigator or 
sponsor medical personnel, may place the subject at significant risk, confound the 
study results, or interfere significantly with the subject's participation in the study. 
11. Subjects who have previously undergone HSCT or plan to undergo HSCT within 
12 months of the Screening/Baseline visit. 
Prior/Current Clinical Study Experience 
12. Subjects who are concurrently enrolled in an investigational drug or device study 
or who received an investigational product within 30 days or 5 half-lives before 
signing the ICF.  
Note: Subjects who are receiving VGL101 in a clinical study may enroll after 
conclusion of their participation in the VGL101 clinical study. 
Other Exclusion Criteria 
13. Subjects who are involved, directly or indirectly, in the conduct or administration 
of this study as an investigator, sub-investigator, study coordinator, or other study 
staff member. 
5.3 
Lifestyle Considerations 
No lifestyle restrictions will be imposed. 
5.4 
Screen Failures 
Screen failures are defined as subjects who consent to participate in the clinical study but 
are not subsequently enrolled. A minimal set of screen failure information is required to 

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ensure transparent reporting of screen failures to meet the Consolidated Standards of 
Reporting Trials (CONSORT) publishing requirements and to respond to queries from 
regulatory authorities. Minimal information includes demography, screen failure details, 
eligibility criteria, and any serious adverse event (SAE). If additional study procedures 
were performed during screening, information from these procedures should be recorded 
in the electronic case report form (eCRF).  
Individuals who do not meet the criteria for participation in this study (screen failure) 
may be rescreened after discussion with the medical monitor and resolution of the issue 
that led to initial screen failure. 

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6 INVESTIGATIONAL MEDICINAL PRODUCT(S) AND 
CONCOMITANT THERAPY 
6.1 
Investigational Medicinal Product 
No intervention will be administered. Subjects will receive their usual treatments for 
ASLP, as prescribed by their physicians. 
6.2 
Concomitant Therapy 
All prescription and over-the-counter medications that have been taken during the 
30 days before Screening/Baseline through the last study visit will be recorded in the 
eCRFs, along with the following: reason for use, dates of administration (including start 
and stop dates), dose, and frequency of administration. A complete history of medications 
for the treatment of ALSP will be recorded. 

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7 SUBJECT DISCONTINUATION/WITHDRAWAL 
7.1 
Subject Discontinuation/Withdrawal from the Study 
Subjects may withdraw from the study at any time or may be withdrawn at any time, at 
the discretion of the investigator, for safety, behavioral, or compliance reasons. When a 
subject wishes to withdraw consent, it is important to distinguish between withdrawing 
his/her consent for a particular study procedure or visit versus withdrawing his/her 
consent from the study entirely (i.e., premature discontinuation). Reasons for premature 
discontinuation from the study include, but are not limited to, the following: 
• Withdrawal of consent 
• Death 
• Intercurrent illness 
• Unacceptable AEs 
• Protocol violation or noncompliance 
• Lost to follow-up 
• Investigator discretion 
• At request of the sponsor, regulatory 
agencies, or institutional review 
board/independent ethics committee 
(IRB/IEC) 
An ET Visit (as shown for the Month 36 Visit in the Schedule of Assessments in Table 1) 
should be conducted at the time of study discontinuation.  
For subjects who discontinue from this study to enroll in a VGL101 clinical study, blood 
biomarker collection will be performed once for both the ET Visit of this study and the 
Screening/Baseline Visit of the VGL101 study and will be analyzed as part of both 
studies.  
For subjects who discontinue from this study to enroll in a VGL101 clinical study, an 
MRI will be collected once for both the ET Visit of this study and the Screening/Baseline 
Visit of the VGL101 clinical study and will be analyzed as part of both studies. 
For subjects who participate in the CSF Sub-study and who discontinue from this study to 
enroll in a VGL101 clinical study, CSF biomarker collection will be performed at the 
Screening or Baseline Visit of the VGL101 clinical study and will be analyzed as part of 
both studies. If CSF collection is not included at the Screening or Baseline Visit of the 
VGL101 clinical study, CSF biomarker collection will be done at the ET Visit of this 
study. 
If the subject withdraws consent for disclosure of future information, the sponsor may 
retain and continue to use any data that are collected before withdrawal of consent. 
Subjects who withdraw from the study may request destruction of any samples that have 
been taken and not tested, and the investigator must document this in the site study 
records. 
7.2 
Lost to Follow-up 
A subject will be considered lost to follow-up if he or she repeatedly fails to return for 
scheduled visits and is unable to be contacted by the investigative site. The site must 
attempt to contact the subject and reschedule the missed visit as soon as possible and 
must counsel the subject on the importance of maintaining the assigned visit schedule and 
ascertain whether or not the subject wishes to and/or should continue in the study. 

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Before a subject is deemed lost to follow up, the investigator or designee must make 
every effort to regain contact with the subject (where possible, 3 telephone calls). These 
contact attempts should be documented in the subject’s medical record. Subjects who 
continue to be unreachable will be considered to have withdrawn from the study.  
Attempts will be made to determine the survival status (alive or deceased) of any subjects 
who fail to return for their study visit or who discontinue from the study before 
completing the 24-month (subjects who withdraw from the study before implementation 
of Amendment 3) or 36-month (subjects who withdraw from the study after 
implementation of Amendment 3) observation period. Study staff will contact the subject 
or the subject’s study partner by telephone to determine survival status 24 or 36 months, 
respectively, after the date of the subject’s Screening Visit or at the end of the study, 
whichever occurs sooner. 
Discontinuation of specific sites or of the study as a whole is described in Appendix 1 
(Section 10.1.6). 

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8 STUDY ASSESSMENTS AND PROCEDURES 
Adherence to the study design requirements, including those specified in the Schedule of 
Assessments (Table 1), is essential and is required for study conduct. Protocol waivers or 
exemptions are not allowed.  
All screening evaluations must be completed and reviewed to confirm that potential 
subjects meet all eligibility criteria. The investigator will maintain a screening log to 
record details of all subjects that are screened and to confirm eligibility or to record 
reasons for screen failure, as applicable. 
Procedures that are conducted as part of the subject’s routine clinical management, within 
the screening period, that are obtained before the ICF is signed may be used for screening 
or baseline purposes provided that the procedures meet the protocol-specified criteria and 
were performed within the timeframe that is defined in the Schedule of Assessments.  
8.1 
Screening Assessments 
8.1.1 
Informed Consent 
The investigator or designated member of the investigational site staff is responsible for 
providing each subject with adequate explanations of the aims, methods, anticipated 
benefits, and potential risks of the study and for obtaining written informed consent from 
each subject (as detailed in Section 10.1.2 before any study-related procedures are 
performed. 
Subjects who meet the criteria for definitive ALSP must have a designated study partner 
(i.e. caregiver) who spends at least 4 hours per week with them. The study partner must 
be able and willing to assist the subject in complying with the study requirements, be able 
to provide information during study visits, and be willing to sign a study partner ICF. 
Subjects who do not have a study partner may be enrolled at the investigator’s discretion 
if they are able to comply with protocol requirements.  
Subjects who meet the criteria for prodromal ALSP and who, at later study visits, meet 
the criteria for definitive ALSP should have a designated study partner for subsequent 
study visits who spends at least 4 hours per week with them unless otherwise approved 
by the sponsor and/or medical monitor. The study partner must be able and willing to 
assist the subject in complying with the study requirements, be able to provide 
information during study visits, and be willing to sign a study partner ICF. Subjects who 
do not have a study partner may continue the study at the investigator’s discretion if they 
are able to comply with protocol requirements. 
8.1.2 
Medical/Family History and Demographic Information 
Relevant medical history (including surgical history) will be documented during 
Screening to assess subject eligibility. Any medical conditions should be captured with at 

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least a start date and an indication of whether the condition is ongoing or resolved. 
Detailed information related to family/subject history of ALSP will be recorded. 
Date of birth, sex, ethnicity, and race will be recorded. 
8.1.3 
Retrospective Pre-Screening MRI (Optional) 
Retrospective pre-screening MRI scans obtained prior to participation in this study may 
be collected if available from the medical history of each consenting subject. This 
information will be used to explore the pre-study trajectory of MRI findings. 
8.1.4 
Prior and Concomitant Medications/Procedures 
All prescription and over-the-counter medications that have been taken during the 
30 days before Screening/Baseline through the last study visit will be documented. A 
complete history of medications taken for the treatment of ALSP will be collected. 
Prior medical procedures will also be recorded. 
8.1.5 
Documentation of CSF1R Gene Mutation 
Documentation of a CSF1R mutation is required for all subjects before enrollment in the 
study.  
8.1.6 
Clinical Global Impression – Severity of Illness (GGI-S) 
The Clinical Global Impressions – Severity of Illness (CGI-S) (Guy, 1976) scale is a 
7-point scale that requires the clinician to rate the severity of the patient’s illness at the 
time of the assessment relative to the clinician’s past experience with patients who have 
the same diagnosis. Raters select one response based on the following question: 
“Considering your total clinical experience with this particular population, how ill is the 
patient at this time?” Scores are as follows: 1 = normal, not at all ill; 2 = borderline ill; 
3 = mildly ill; 4 = moderately ill; 5 = markedly ill; 6 = severely ill; and 7 = among the 
most extremely ill patients. 
The CGI-S will be completed at Screening/Baseline. 
8.1.7 
Patient Global Impression – Severity of Illness (PGI-S) 
The Patient Global Impression – Severity of Illness (PGI-S) is the patient-reported 
counterpoint to the CGI-S (Guy, 1976). The PGI-S is a 1-item questionnaire that is 
designed to assess patient’s impression of disease severity. The PGI-S item asks the 
respondents to best describe how their symptoms are now on the following 4-point scale: 
1 = normal, 2 = mild, 3 = moderate, or 4 = severe.  
The PGI-S will be completed at Screening/Baseline. 

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8.1.8 
Urine Drug Screen 
Subjects will undergo urine drug screening for the presence of phencyclidine (PCP), 
cocaine, cannabinoids, opiates/barbiturates, benzodiazepines, amphetamines, methadone, 
and MDMA (3,4 methylenedioxymethamphetamine/Ecstasy/Molly) at Screening/ 
Baseline. Subjects with a positive urine drug screen will be excluded, unless explained by 
use of an approved prescription medication. 
8.2 
Pharmacodynamic (Biomarker) Assessments 
8.2.1 
Blood for NfL Analysis 
Blood samples for NfL will be obtained at Screening/ Baseline and at Months 6, 12, 18, 
24, 30, and 36/ET to provide further insight into the onset and progression of ALSP. The 
completion of these investigations will be based on the results of this or other exploratory 
work.  
For subjects who discontinue from this study to enroll in a VGL101 clinical study, blood 
biomarker collection will be performed once for both the ET Visit of this study and the 
Screening/Baseline Visit of the VGL101 study and will be analyzed as part of both 
studies.  
Detailed instructions regarding sample collection, processing, and shipping will be 
provided to the sites in a study laboratory manual. 
8.2.2 
Magnetic Resonance Imaging 
MRI scans, including, but not limited to T1-weighted, T2-weighted, FLAIR, and 
diffusion-weighted MRI scans, will be obtained at Screening/Baseline and at Months 6, 
12, 18, 24, 30, and 36/ET. The MRI scans may be obtained ±2 days before the scheduled 
visit. For subjects who discontinue from this study to enroll in a VGL101 clinical study, 
an MRI will be collected once for both the ET Visit of this study and the 
Screening/Baseline Visit of the VGL101 clinical study and will be analyzed as part of 
both studies. 
Detailed instructions regarding the MRI collection protocol will be provided in a separate 
set of image acquisition guidelines. 
Please note that subjects may be given light sedation (e.g., short acting benzodiazepine) if 
they are unable to lie still during scanning or have involuntary movements; this is not a 
protocol requirement and can be based on PI discretion. For those subjects receiving light 
sedation, if the MRI is scheduled on the same day as their cognitive assessments then the 
sedation and scan should occur after the cognitive assessments have been completed. 
8.3 
Clinical Outcome Assessments 
The schedule of assessments is shown in Table 1. At each clinic visit, whenever feasible, 
the cognitive and motor assessments should be prioritized. Study visits should be 

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scheduled at approximately the same time each day to ensure that scales are completed at 
consistent times during the study. 
Detailed instructions regarding the collection and assessment of the clinical outcome 
assessments will be provided in a separate manual. 
8.3.1 
Cognitive Assessments 
8.3.1.1 
Montreal Cognitive Assessment Scale (MoCA) 
The MoCA is a brief 30-question test that is used to evaluate cognitive abilities and 
dementia (Smith et al, 2007; Chou et al, 2010). The MoCA evaluates different types of 
cognitive domains, including orientation, short-term memory, delayed recall, abstraction, 
visuospatial, and executive functioning; language; and attention. The scale, which is 
available in 35 languages, takes 10 to 12 minutes to complete. Scores range from zero to 
30; scores of ≥26 are generally considered normal.  
The MoCA will be completed at Screening/Baseline and at Months 6, 12, 18, 24, 30, and 
36/ET. 
8.3.1.2 
Clinical Dementia Rating Scale plus National Alzheimer’s Coordinating 
Center-Frontotemporal Lobar Degeneration (CDR®+NACC-FTLD) 
The CDR®+NACC-FTLD (Miyagawa et al, 2020) is a semi-structured global assessment 
measure that was developed to measure the severity of dementia symptoms in 
Alzheimer’s disease and related dementias. The scale measures the following 6 domains: 
Memory; Orientation; Judgement and Problem Solving; Community Affairs Engagement; 
Home and Hobbies; Behavior; Language; and Personal Care. The first 7 domains are 
rated on a 5-point scale as follows: 0 = normal, 0.5 = questionably or minimally 
impaired, 1 = mildly but definitely impaired, 2 = moderately impaired, and 3 = most 
severely impaired. The eighth domain, Personal Care, does not have a rating of 0.5 and, 
therefore, is rated on a 4-point scale. . 
The sum total of the ratings of the 8 individual domains is calculated to create the clinical 
dementia rating (CDR®+NACC-FTLD) sum of boxes (CDR®+NACC-FTLD-SB).  
The global CDR®+NACC-FTLD score is calculated from the 8 domains and is rated on a 
5-point scale (0/0.5/1/2/3; see below). The CDR®+NACC-FTLD-SB exhibits good 
correlation with frontotemporal cerebral blood hypoperfusion in patients with FTLD 
patients and is useful in the characterization of the non-amnestic symptoms in patients 
with dementia. CDR®+NACC-FTLD was selected as an outcome measure in this trial 
because frontal lobes are often affected by the disease process of ALSP, and behavioral 
symptoms are common in patients with ALSP.  
Global CDR®+NACC-FTLD score ranges from 0 to 3 (the lower the better) and is 
calculated using the following criteria: 
1. If all domains are 0, then the global CDR®+NACC-FTLD score is 0. 

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2. If the maximum domain score is 0.5, the global CDR®+NACC-FTLD score is 0.5. 
3. If the maximum domain score is above 0.5 in any domain, the following applies: 
a. If the maximum domain score is 1 and all other domains are 0, the global 
CDR®+NACC-FTLD score is 0.5. 
b. If the maximum domain score is 2 or 3, and all other domains are 0, the 
global CDR®+NACC-FTLD score is 1. 
c. If the maximum score occurs only once, and there is another rating besides 
0, the global CDR®+NACC-FTLD score is one level lower than the level 
corresponding to maximum impairment. 
4. If the maximum domain score occurs more than once, then the global 
CDR®+NACC-FTLD score is the maximum domain score. 
The CDR®+NACC-FTLD will be administered by trained site personnel at 
Screening/Baseline and at Months 6, 12, 18, 24, 30, and 36/ET. At the investigator’s 
discretion, the CDR®+NACC-FTLD may not need to be administered if there are no 
signs or symptoms of cognitive impairment (i.e., normal score on the MoCA) or if the 
subject does not have a study partner who has provided informed consent for this study. 
8.3.1.3 
Brief Assessment of Cognition (BAC) 
The BAC (https://littlegreensoftware.com/work/bacbacs) is a tablet-based version of the 
paper-based BAC instrument that was developed for use in schizophrenia and other 
conditions that affect cognition. The BAC can be administered as a full battery or as a 
customized smaller selection of subsets of tests. The following test subsets are included: 
verbal memory, digit sequencing, verbal fluency, and symbol coding. All tests in the 
BAC are completed under the supervision of a trained rater. 
The BAC will be completed at Screening/Baseline and at Months 6, 12, 18, 24, 30, and 
36/ET. 
8.3.2 
Motor Assessments (Ambulatory Subjects) 
8.3.2.1 
Two-Minute Walk Test (2MWT) 
The 2MWT (Witherspoon et al, 2019) is a measure of self-paced walking ability and 
functional capacity, particularly for individuals who cannot manage longer periods of 
walking. The 2MWT has been used as an outcome measure in a variety of health 
conditions, including neuromuscular diseases in the adult and pediatric populations. The 
test measures the distance a person can walk in 2 minutes. Individuals are encouraged to 
walk as fast as they can, safely, for 2 minutes, and to cover as much ground as possible 
without running. Rest breaks are allowed, if needed, but the timer is not stopped. Walking 
aids can be used, if needed, but should be kept consistent from test to test. Rest breaks 
and use of aids should be recorded. As normal subjects aged <59 years can walk up to 

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200 meters in 2 minutes, a testing area that allows a minimum number of turns should be 
available. 
The 2MWT will be done at Screening/Baseline and at Months 6, 12, 18, 24, 30, and 
36/ET. 
8.3.2.2 
Timed Up and Go (TUG) Test 
The TUG (Ibrahim et al, 2017) is used to determine the time needed to progress from 
sitting to standing and walking. In addition, the test helps to evaluate the probability for 
falls. The TUG, which was initially designed for elderly persons, is also used in 
populations with conditions that can affect ambulation and balance. This tool is validated 
for populations with Parkinson’s disease, multiple sclerosis, hip fracture, Alzheimer’s 
disease, cerebrovascular accident (CVA), Huntington disease, and post-CVA. The 
individual starts in a seated position in a chair with armrests and, upon command, stands 
up, walks 3 meters, turns around, walks back to the chair, and sits down. The time stops 
when the patient is seated. The use of walking aids should be recorded and kept 
consistent between tests. 
The TUG will be done at Screening/Baseline and at Months 6, 12, 18, 24, 30, and 36/ET. 
8.3.3 
Severity of Illness Assessments 
8.3.3.1 
Clinical Global Impression – Change (CGI-C) 
The CGI-C (Guy, 1976) is a 7-point scale that requires the clinician to assess how much 
the patient's illness has improved or worsened relative to the baseline state at the 
beginning of the intervention. Raters select one response based on the following question, 
“Compared to your patient’s condition at the beginning of study, how much has your 
patient changed?” Scores are as follows: 1 = very much improved; 2 = much improved; 
3 = minimally improved; 4 = no change; 5 = minimally worse; 6 = much worse; and 
7 = very much worse. 
The CGI-C will be completed at Months 6, 12, 18, 24, 30, and 36/ET. 
8.3.3.2 
Patient Global Impression – Change (PGI-C) 
The PGI-C is the patient-reported outcome counterpoint to the CGI-C (Guy, 1976). The 
qualitative assessment of meaningful change is determined by the patient in response to 
the question, “Compared to your condition at the beginning of study, how much has your 
condition changed?” Scores are as follows: 1 = very much improved; 2 = much 
improved; 3 = minimally improved; 4 = no change; 5 = minimally worse; 6 = much 
worse; and 7 = very much worse.  
The PGI-C will be completed at Months 6, 12, 18, 24, 30, and 36/ET. 

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8.3.4 
Other Functional and Psychiatric Assessments 
8.3.4.1 
Functional Assessment Questionnaire (FAQ) 
The FAQ (Pfeffer et al, 1982) measures instrumental activities of daily living, such as 
preparing balanced meals and managing personal finances. Functional changes in 
instrumental activities of daily living that require a higher cognitive ability are noted 
earlier in the dementia process than changes in basic activities of daily living. Therefore, 
the FAQ is useful to monitor these functional changes over time in patients with mild 
dementia and has been used in clinical trials of patients with mild cognitive impairment 
and in patients with mild to moderate and severe dementias.  
The FAQ assesses 10 functions related to personal finances, shopping, playing games, 
meal preparation, watching television, following the news, taking medications, and 
traveling. Each function is rated from 0 to 3 (0 = normal, 1 = has difficulty but can do 
alone, 2 = requires assistant, and 3 = totally dependent on others to do). The FAQ 
demonstrates high correlation with cognitive measures and is sensitive to change over 
time. 
The FAQ will be completed at Screening/Baseline and at Months 6, 12, 18, 24, 30, and 
36/ET. The FAQ will only be completed if the subject has a study partner who has 
provided informed consent for the study. 
8.3.4.2 
Neuropsychiatric Inventory – 12-Item Version (NPI-12) 
The NPI-12 (Cummings et al, 1994) is an abbreviated inventory that provides a brief 
assessment of neuropsychiatric symptomatology in clinical practice settings and in 
clinical trials. The NPI-12 assesses the following 12 behavioral domains that are common 
in dementia: hallucinations, delusions, agitation/aggression, dysphoria/depression, 
anxiety, irritability, disinhibition, euphoria, apathy, aberrant motor behavior, sleep and 
nighttime behavior change, and appetite and eating change. 
The NPI-12 is administered by the clinician to the study partner. The study partner is 
usually a family member who is involved in the daily care of the patient but can be 
administered to a professional caregiver or other involved person as long as the person 
has detailed knowledge of the patient’s behavior. The clinician reads each question to the 
study partner as it is written. After reading the screening question, the study partner is 
asked if the behavior that was described is present, if the answer is “no” then the clinician 
proceeds to the next section and reads the next screening question. If the answer is “yes” 
to the screening question, the rater then rates the frequency (rarely, sometimes, often, 
very often), severity of the symptoms that have been present within the last month (mild, 
moderate, or severe), and the associated impact of the symptom manifestations on them 
(i.e., caregiver distress; not at all, minimally, mildly, moderately, severely, or very 
severely or extremely). The total scores can be used for monitoring the worsening of or 
improvement in neuropsychiatric symptoms.  

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The NPI-12 will be completed at Screening/Baseline and at Months 6, 12, 18, 24, 30, and 
36/ET. The NPI-12 will only be completed if the subject has a study partner who has 
provided informed consent for the study. 
8.3.4.3 
Cortical Basal ganglia Functional Scale (CBFS) 
The CBFS (Lang et al, 2020) is a novel rating scale that evaluates experiences in daily 
living (EDL) and behavioral, language, and cognitive impairments in patients with 4 
repeat tauopathies. The CBFS consists of 14 questions on motor EDLs (Motor 
Component) and 17 questions on nonmotor EDLs (Nonmotor Component), each of which 
is rated on a Likert 5-point scale that rates function from 0 to 4, where 0 = normal or no 
problems and 4 = severe problems. The questions are for the patient but should be 
answered by the patient and study partner working together. Responses are to be based on 
the usual or average function over the past 2 weeks. 
The CBFS will be completed at Screening/Baseline and at Months 6, 12, 18, 24, 30, and 
36/ET. 
8.3.4.4 
Zarit Burden Interview 
The Zarit Burden Interview (Knight et al, 2000) is a caregiver self-report measure that is 
used to assess the burden of the disease on the primary caregiver. The revised version 
contains 22 items; each item on the interview is a statement that the study partner is asked 
to rate using a 5-point scale that ranges from 0 (“never”) to 4 (“nearly always”). 
Translations of the Zarit Burden Inventory are available in many languages. The 22-item 
questionnaire will be used in this study to assess the impact of ALSP on study partners.  
The Zarit Burden Interview will be completed at Screening/Baseline and at Months 6, 12, 
18,  24, 30, and 36/ET. The Zarit Burden Interview will only be completed if the subject 
has a study partner who has provided informed consent for the study. 
8.4 
Safety Assessments 
Safety assessments include AEs, physical and neurological examinations, the C-SSRS, 
and pregnancy testing for women of childbearing potential. 
8.4.1 
Adverse Events 
An AE is any unfavorable or unintended sign (including an abnormal laboratory finding), 
symptom, or disease temporally associated with the use of a medical treatment or 
procedure that may or may not be considered related to a study procedure. 
All AEs and SAEs that are reported by the subject (or, when appropriate, by a caregiver, 
surrogate, or legally authorized representative) or observed by the investigators from the 
time the ICF is signed through the Month 24 Visit (subjects who complete the study 
before implementation of Amendment 3), the Month 36 Visit (subjects who complete the 
study after implementation of Amendment 3), or the ET Visit will be recorded. All 

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AEs/SAEs will be monitored until resolution or stabilization. Adverse event reporting 
procedures are summarized in Appendix 2 (Section 10.2). 
8.4.2 
Physical and Neurological Examinations 
A complete physical examination will include measurement of height and weight 
(Screening/Baseline only) and examination of general appearance and the skin, neck 
(including thyroid), eyes, ears, nose, throat, heart, lungs, abdomen, lymph nodes, and 
extremities. Genital, rectal, and breast examination may be excluded if not clinically 
indicated. 
The neurological examination will include assessment of mental status (level of 
consciousness, orientation, speech, memory, etc.), examination of cranial nerves II-XII, 
motor examination (muscle appearance, tone, strength, and reflexes), sensory 
examination, reflexes, coordination, stance, gait, and balance. 
Physical and neurological examinations will be conducted at Screening/Baseline and at 
Months 6, 12, 18, 24, 30, and 36/ET. 
8.4.3 
Columbia-Suicide Severity Rating Scale (C-SSRS) 
The C-SSRS (Posner et al, 2011) is a semi-structured interview that was designed to 
quantify the severity of suicidal ideation and behavior. The C-SSRS, which is available in 
over l00 languages, requires approximately 5 minutes to complete. Interviewers are not 
required to have mental health training and can be trained on administration of the 
questionnaire if they have no prior experience with it. The “Baseline/Screening” (lifetime 
and last 6 months) and “Since Last Visit” versions of the scale will be used.  
The “Baseline/Screening” (lifetime and last 6 months) version, which assesses the 
lifetime experience of the subject with suicide events and suicidal ideation and the 
occurrence of suicide events or ideation within a specified time period prior to entry into 
the study, will be completed for all subjects at Screening/Baseline to determine 
eligibility. For subjects with a positive response on Question 4 or 5 of the C-SSRS at 
Screening/Baseline, a risk assessment should be done by a qualified healthcare 
professional to assess whether it is safe for the subject to participate in the study. 
The “Since Last Visit” C-SSRS form will be completed at Months 6, 12, 18, 24, 30, and 
36/ET. If a subject demonstrates potential suicidal ideation associated with actual intent 
or method or plan as indicated by “YES” answers on Question 4 or 5 of the C-SSRS, the 
investigator will evaluate whether a risk assessment by a qualified mental health 
professional (or the investigator alone if the investigator is a qualified mental health 
professional) is needed and whether the subject should continue in or be discontinued 
from the trial. 
8.4.4 
COVID-19 Assessments and Testing 
COVID-19 assessments (temperature and symptom assessment) and testing will be 
performed per local guidelines and standard of care at the site. 

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If a subject develops an active COVID-19 infection (whether confirmed or suspected) 
during the study, the investigator must consult with the sponsor medical monitor to 
determine the best course of action. 
8.4.5 
Pregnancy Testing 
A urine pregnancy test will be performed for women of childbearing potential at 
Screening/Baseline and at Months 6, 12, 18, 24, 30, and 36/ET. Female subjects of 
childbearing potential must have a negative urine pregnancy test at Screening/Baseline 
for entry into the study. If a subject becomes pregnant during the study, the investigator 
must consult the sponsor medical monitor to determine the best course of action.  
8.5 
Optional CSF Biomarker Sub-study 
Cerebrospinal fluid samples for NfL, cytokine(s), soluble TREM2, and soluble CSF1R 
analysis will be obtained at Screening/Baseline and at Months 12, 24, and 36/ET from 
subjects who provide informed consent to participate in the optional CSF Biomarker 
Sub-study to provide further insight into the onset and progression of ALSP. The 
completion of these investigations will be based on the results of this or other exploratory 
work.  
For subjects who participate in the CSF Sub-study and who discontinue from this study to 
enroll in a VGL101 clinical study, CSF biomarker collection will be performed at the 
Screening or Baseline Visit of the VGL101 clinical study and will be analyzed as part of 
both studies. If CSF collection is not included at the Screening or Baseline Visit of the 
VGL101 clinical study, CSF biomarker collection will be done at the ET Visit of this 
study. 
Detailed instructions regarding sample collection, processing, and shipping will be 
provided to sites in a study laboratory manual. 
8.6 
Survival Assessment 
Attempts will be made to determine the survival status (alive or deceased) of any subject 
who fails to return for the vial visit or who discontinues from the study before completing 
the 24-month (subjects who withdraw from the study before implementation of 
Amendment 3) or 36-month (subjects who withdraw from the study after implementation 
of Amendment 3) observation period. Study staff will contact the subject or the subject’s 
study partner by telephone to determine survival status 36 months after the date of the 
subject’s Screening Visit or at the end of the study, whichever occurs sooner. 
9 STATISTICAL CONSIDERATIONS 
9.1 
Sample Size Determination 
The sample size of approximately 60 subjects was determined empirically and is 
expected to provide sufficient information to address the study objectives in this rare 
disease. 

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9.2 
Analysis Sets 
Data will be analyzed for all subjects who have data available at Screening/Baseline and 
at least 1 post-baseline timepoint. 
9.3 
Statistical Analysis 
The Statistical Analysis Plan will be finalized before database lock and will include a 
more technical and detailed description of the statistical analyses that are described in this 
section. 
9.3.1 
Disposition and Demographics 
The number of subjects who were enrolled, completed the study, and discontinued from 
the study, along with the reason for discontinuation, will be summarized. Descriptive 
statistics will be presented for continuous demographic and baseline characteristics; 
counts and percentages will be presented for categorical variables. 
9.3.2 
Prior and Concomitant Medications 
Prior and concomitant medications will be mapped to a World Health Organization 
(WHO) Drug Dictionary preferred term and drug classification. The number and percent 
of subjects taking medications will be summarized using preferred terms and drug 
classifications. 
9.3.3 
Clinical Outcome and Biomarker Analyses 
Descriptive statistics will be presented for the observed and change from baseline values 
for clinical, biomarker, and safety assessments. Continuous variables will be summarized 
using the number of observations, mean, standard deviation, median, minimum, and 
maximum. Categorical variables will be summarized using frequency counts and 
percentages. Ninety-five percent (95%) confidence intervals will be presented as 
appropriate.  
The association between phenotypic heterogeneity and phenotype/genotype and clinical 
outcomes/disease progression and between biomarkers and clinical outcomes/disease 
progression may be assessed. 
9.3.4 
Safety Analyses 
Adverse events will be mapped to a MedDRA (Medical Dictionary for Regulatory 
Activities) preferred term and system organ classification. Severity will be assessed by 
investigator. All AEs will be listed for individual subjects showing both verbatim and 
preferred terms. Separate summaries of AEs, adverse events of interest (AESIs), SAEs, 
and AEs leading to discontinuation from the study will be prepared. 
Categorial safety data (e.g., C-SSRS) will be summarized with frequency counts and 
percentages. 

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10 SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS 
10.1 
Appendix 1: Regulatory, Ethical, and Study Oversight Considerations 
10.1.1 
Regulatory and Ethical Considerations 
This study will be conducted in accordance with the protocol and with the following: 
• Consensus ethical principles derived from international guidelines including the 
Declaration of Helsinki and Council for International Organizations of Medical 
Sciences (CIOMS) International Ethical Guidelines 
• Applicable International Council for Harmonisation of Technical Requirements for 
Pharmaceuticals for Human Use (ICH) Good Clinical Practice (GCP) Guidelines 
• Applicable laws and regulations 
The protocol, protocol amendments, ICF, Investigator Brochure, and other relevant 
documents (e.g., advertisements) must be submitted to an IRB/IEC by the investigator 
and reviewed and approved by the IRB/IEC before the study is initiated. Any 
amendments to the protocol will require IRB/IEC approval before implementation of 
changes made to the study design, except for changes necessary to eliminate an 
immediate hazard to study subjects. 
The investigator will be responsible for the following: 
• Providing written summaries of the status of the study to the IRB/IEC annually or 
more frequently in accordance with the requirements, policies, and procedures 
established by the IRB/IEC. 
• Notifying the IRB/IEC of SAEs or other significant safety findings as required by 
IRB/IEC procedures. 
• Providing oversight of the conduct of the study at the site and adherence to 
requirements of 21 Code of Federal Regulations (CFR), ICH guidelines, the IRB/IEC, 
European regulation 536/2014 for clinical studies (if applicable), and all other 
applicable local regulations. 
10.1.2 
Informed Consent Process 
The investigator or designee will explain the nature of the study to the subject or his/her 
legally authorized representative and answer all questions regarding the study. 
Subjects must be informed that their participation is voluntary. Subjects or their legally 
authorized representative (with subject assent) will be required to sign a statement of 
informed consent that meets the requirements of 21 CFR 50, local regulations, ICH 
guidelines, Health Insurance Portability and Accountability Act (HIPAA) requirements, 
where applicable, and the IRB/IEC or study site. 
 

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Subjects who meet the criteria for definitive ALSP must have a designated study partner 
(i.e. caregiver) who spends at least 4 hours per week with them. The study partner must 
be able and willing to assist the subject in complying with the study requirements, be able 
to provide information during study visits, and be willing to sign a study partner ICF. 
Subjects who do not have a study partner may be enrolled at the investigator’s discretion 
if they are able to comply with protocol requirements.  
Subjects who meet the criteria for prodromal ALSP and who, at later study visits, meet 
the criteria for definitive ALSP should have a designated study partner for subsequent 
study visits who spends at least 4 hours per week with them unless otherwise approved 
by the sponsor and/or medical monitor. The study partner must be able and willing to 
assist the subject in complying with the study requirements, be able to provide 
information during study visits, and be willing to sign a study partner ICF. Subjects who 
do not have a study partner may continue the study at the investigator’s discretion if they 
are able to comply with protocol requirements. 
The medical record must include a statement that informed consent was obtained before 
the subject was enrolled in the study and the date consent was obtained. The authorized 
person who obtains the informed consent must also sign the ICF. 
Subjects must be reconsented to the most current version of the ICF(s) during their 
participation in the study. A copy of the ICF(s) must be provided to the subject or the 
subject’s legally authorized representative. 
Individuals who do not meet the criteria for participation in this study at initial screening 
(screen failure) may be rescreened at the discretion of the investigator, after discussion 
with the medical monitor, and after resolution of the issue that led to initial screen failure. 
Rescreened subjects do not need to sign another ICF but will be assigned a new subject 
number. 
10.1.3 
Data Protection 
Subjects will be assigned a unique identifier by the sponsor. Any subject records or 
datasets that are transferred to the sponsor will contain the identifier only; subject names 
or any information that would make the subject identifiable will not be transferred. 
Subjects must be informed that their personal study-related data will be used by the 
sponsor in accordance with local data protection law. The level of disclosure must also be 
explained to the subject. 
Subjects must be informed that their medical records may be examined by Clinical 
Quality Assurance auditors or other authorized personnel appointed by the sponsor, by 
appropriate IRB/IEC members, and by inspectors from regulatory authorities. 
10.1.4 
Dissemination of Clinical Study Data 
The sponsor will fulfill its commitment to publicly disclose clinical study results through 
posting study results on ClinicalTrials.gov and other public registries in accordance with 

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applicable local laws/regulations. Study results will be reported in an objective, accurate, 
balanced, and complete manner and will be reported regardless of study outcome or the 
country in which the study was conducted. 
10.1.5 
Source Documents 
Source documents, defined as original documents, data, and records, provide evidence for 
the existence of the subject, and substantiate the integrity of the data that are collected. 
Source documents are filed at the investigator’s site and should contain all information in 
original records and certified copies of original records of clinical findings, observations, 
or other activities in the clinical trial that are necessary for the reconstruction and 
evaluation of the trial. Data collected during this study must be recorded on the 
appropriate source documents. 
Data that are transcribed from source documents onto the eCRFs must be consistent with 
the source documents or the discrepancies must be explained. The investigator may need 
to request previous medical records or transfer records, depending on the study. Current 
medical records must also be available. 
In some instances, the initial entry of data will be made by subjects and site personnel 
onto a hand-held device or tablet at the site and will be considered the source, e.g. 
eSource. This system is fully compliant with 21 CFR Part 11 regulations. 
The investigator(s)/institution(s) will permit study-related monitoring, audits, IRB/IEC 
review, and regulatory inspection(s), providing direct access to source data documents. 
10.1.6 
Study and Site Closure 
The sponsor designee reserves the right to close the investigative site or terminate the 
study at any time for any reason at the sole discretion of the sponsor. Investigative sites 
will be closed upon study completion. An investigative site is considered to be closed 
when all required documents and study supplies have been collected and a study-site 
closure visit has been performed. 
The investigator may initiate investigative site closure at any time, provided there is 
reasonable cause and sufficient notice is given in advance of the intended termination. 
Reasons for the early closure of an investigative site by the sponsor or investigator may 
include but are not limited to: 
• Failure of the investigator to comply with the protocol, the requirements of the 
IRB/IEC or local health authorities, sponsor procedures, or GCP guidelines. 
• Inadequate recruitment of subjects by the investigator. 
• Discontinuation of further investigational medicinal product development. 

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10.1.7 
Publication Policy 
The publication policy is outlined in the Clinical Trial Agreement. The data generated in 
this clinical trial are the exclusive property of Vigil Neuroscience, Inc, and are 
confidential. Written approval from Vigil Neuroscience, Inc, is required before disclosing 
any information related to this clinical trial is disclosed. 
The clinical study report will be prepared and provided to the regulatory agencies as 
required by the applicable regulatory requirement(s). 
 
 

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10.3 
Appendix 3: Criteria for ALSP Based on Magnetic Resonance Imaging 
(MRI)/Computed Tomography (CT) 
Brain MRI/CT findings (Konno et al, 2018): 
1. Bilateral cerebral white matter lesions 
2. Thinning of the corpus callosum 
Characteristic brain MRI findings of ALSP are shown in Figure 2. 
Figure 2 
Characteristic Brain Magnetic Resonance Imaging (MRI)/Computed 
Tomography (CT) Findings in Patients With adult-Onset 
Leukoencephalopathy With Axonal Spheroids and Pigmented Glia 
(ALSP) 
 
(A–E,MRI; F, CT). Fluid attenuated inversion recovery imaging of a 43-year-old case with p.Ile794Thr 
mutation in colony-stimulating factor 1 receptor (CSF1R) (A–C, axial; D, sagittal). Abnormal signals are 
observed in frontal white matter around anterior horn of the lateral ventricles, in the posterior limb of the 
internal capsule (arrow, A), and in the splenium of the corpus callosum (arrow, B). A thinning of the corpus 
callosum is shown (arrow, D). (E) Diffusion-restricted lesions in a 22-year-old case with the splice site 
mutation (c.2442+1G>A) in CSF1R. (F) Calcifications are revealed by thin-slice CT of the 43-year-old 
case with p.Ile794Thr mutation (arrows). 
Source: Konno et al, 2018. 
Additional Diagnostic Criteria: 
On brain MRI scans, the white matter lesions without gadolinium enhancement can be 
scattered and asymmetric during the initial stages of the disease but later become 
confluent, diffuse, and more symmetric. Frontal and parietal lobe predominance is 

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observed with involvement of the periventricular deep white matter and dilation of the 
lateral ventricles. 
Thinning of the corpus callosum with signal abnormalities is observed even in the early 
stages of the disease (Sundal et al, 2012; Konno et al, 2017a). Fluid attenuated inversion 
recovery sagittal imaging is recommended to evaluate changes in the corpus callosum. 
Abnormal signaling in the pyramidal tracts and diffusion-restricted lesions are observed 
in some cases (Konno et al, 2017a; Konno et al, 2017b). 
None of ALSP cases showed middle cerebellar peduncle lesions, which are known as a 
characteristic finding of some leukoencephalopathies (Konno et al, 2018). 

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10.4 
Appendix 4: Abbreviations and Definitions 
 
Abbreviation 
Definition 
2MWT 
2-Minute Walk Test 
AE 
Adverse event 
ALS 
Amyotrophic lateral sclerosis 
ALSP 
Adult-onset leukoencephalopathy with axonal spheroids and pigmented 
glia  
BAC 
Brief Assessment of Cognition 
CBFS 
Cortical Basal ganglia Functional Scale  
CDR 
Clinical dementia rating 
CDR®+NACC-FTLD 
Clinical Dementia Rating Scale plus National Alzheimer’s Coordinating 
Center-Frontotemporal Lobar Degeneration  
CDR®+NACC FTLD-SB 
CDR®+NACC FTLD sum of boxes 
CFR 
Code of Federal Regulations 
CGI-C 
Clinical Global Impression - Change 
CGI-S 
Clinical Global Impression – Severity of Illness 
CNS 
Central nervous system 
COVID-19 
Coronavirus disease 2019 
CSF 
Cerebrospinal fluid 
CSF1R 
Colony-stimulating factor 1 receptor  
C-SSRS 
Columbia-Suicide Severity Rating Scale 
CVA 
Cerebrovascular accident 
ET 
Early Termination 
eCRF 
Electronic case report form 
EDL 
Experiences in daily living  
FAQ 
Functional Activities Questionnaire 
FLAIR 
Fluid-attenuated inversion recovery 
FTD 
Frontotemporal dementia 
GCP 
Good Clinical Practice 
HSCT 
Hematopoietic stem cell transplant 
ICF 
Informed consent form 
ICH 
International Council for Harmonisation of Technical Requirements for 
Pharmaceuticals for Human Use 
IEC 
Independent ethics committee 
IRB 
Institutional review board 

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Abbreviation 
Definition 
MoCA 
Montreal Cognitive Assessment 
MRI 
Magnetic resonance imaging 
NfL 
Neurofilament light chain 
NPI-12 
Neuropsychiatric Inventory – 12 Item Version 
PGI-C 
Patient Global Impression - Change 
PGI-S 
Patient Global Impression – Severity of Illness 
SAE 
Serious adverse event 
TREM2 
Triggering receptor on myeloid cells 2 
TUG 
Timed Up and go 

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10.5 
Appendix 5: Protocol Amendment History 
The summary of changes for the current amendment (Amendment 4; protocol 
version 5.0) is located before the Table of Contents. 
10.5.1 
Amendment 1: Protocol Version 2.0 (29 Jul 2021) 
Overall Rationale for Amendment 
The overall rationale for this amendment is to revise the Schedule of Assessments to 
exclude some of the previously planned clinical outcome measures to reduce burden on 
the study participants and to revise the study entry criteria to exclude kindred individuals 
and individuals who had previously received a hemopoietic stem cell transplant (HSCT), 
as recommended by the US Food and Drug Administration (FDA).  
 
Section No. and Title 
Description of Change 
Brief Rationale 
1.1, Study Endpoints, 
Pharmacodynamic (Biomarker) 
Endpoints 
3.2.1, Pharmacodynamic 
(Biomarker) Endpoints 
Revised the first endpoint to 
exclude measurement of 
cytokines and soluble TREM2 in 
blood 
Only to be evaluated in CSF 
Revised the second endpoint to 
indicate that biomarkers in CSF 
will only be determined in 
subjects who provide informed 
consent to participate in an 
optional CSF Biomarker 
Sub-study 
Reduce subject burden 
Revised third endpoint to remove 
the types of MRIs that will be 
performed 
Remove excessive detail from 
objective 
1.1, Study Endpoints, Clinical 
Outcome Endpoints 
3.2.2, Clinical Outcome 
Endpoints 
Revised the clinical outcome 
measures to exclude the 
following assessments: 
MDS-UPDRS – Part III, TFC, 
CIBIC+, MINT, SF-36, Aural 
Analytics Speech Assessment, 
and Real-World Experience of 
ADL (PAMSys sensor) 
Reduce subject burden 
Reordered clinical outcome 
endpoints into the following 
categories: 1) cognitive 
assessments, 2) motor 
assessments, 3) severity of illness 
assessments, and 4)functional, 
psychiatric, and other 
assessments 
Categorize scales by purpose 
rather than by the individual 
who completes the assessment 
1.1, Brief Summary 
4.1, Overall Design 
Revised paragraph 1 to remove 
references to “kindred” 
Limit relevant patient 
population for this natural 
history study to carriers of the 

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Section No. and Title 
Description of Change 
Brief Rationale 
CSF1R mutation (symptomatic 
or asymptomatic)  
1.1, Brief Summary 
4.1, Overall Design 
Revised paragraph 2 to remove 
biomarkers in CSF, and to 
remove references to testing for 
COVID-19  
Consistency with changes in the 
Schedule of Assessments 
Added a paragraph about the 
optional CSF Biomarker 
Sub-study 
Consistency with changes in the 
Schedule of Assessments 
1.1, Treatment Groups and 
Duration 
Revised duration of follow-up 
from “24 months” to “up to 
24 months” 
Account for potential early 
discontinuations 
1.1, Number of Subjects 
9.1, Sample Size Determination 
Changed planned sample size 
from up to 50 subjects 
(approximately 38 with ALSP 
and 12 carriers [asymptomatic or 
kindred]) to up to 36 subjects 
(approximately 30 subjects with 
symptomatic ALSP and 
6 asymptomatic carriers of the 
CSF1R gene mutation) 
Reduction in sample size due to 
change in study population (i.e., 
exclusion of kindred subjects) 
1.2, Schema 
Revised Figure 1 
Consistency with changes in 
study design and Schedule of 
Assessments  
1.3, Schedule of Assessments 
Revised wording to 1) specify 
that, whenever feasible, cognitive 
and motor assessments should be 
prioritized, and 2) remove 
recommendations for timing of 
other assessments 
Clarify study procedures 
1.3, Schedule of Assessments  
Reorganized assessments 
Clarify study procedures 
1.3, Schedule of Assessments 
8.1, Screening Assessments 
Removed the MMSE as a 
screening tool; removed the 
optional skin biopsy 
Reduce subject burden 
1.3, Schedule of Assessments 
8.3, Clinical Outcome 
Assessments 
Removed the following 
assessments: MDS-UPDRS – 
Part III, TFC, CIBIC+, MINT, 
SF-36, Aural Analytics Speech 
Assessment, Real-World 
Experience of ADL (PAMSys 
sensor)  
Reduce subject burden  
Added the CBFS as a clinical 
outcome measure 
Obtain additional information 
on experiences in daily living 
and on behavioral, language, 
and cognitive impairments  

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Section No. and Title 
Description of Change 
Brief Rationale 
1.3, Schedule of Assessments 
8.3.9, Gait and Balance 
Assessments (BioSensics 
Wearable Sensors) in 
Ambulatory Subjects at Selected 
Sites 
Removed specification that only 
subjects who are enrolled at US 
sites would be eligible to 
participate in the digital 
biomarker assessment 
Provide flexibility 
1.3, Schedule of Assessments 
4.4, Safety Assessments 
8.4.4, COVID-19 Assessments 
and Testing 
Changed COVID-19 assessments 
and testing to be in line with 
local guidelines and standard of 
care at each site 
Study will be conducted across 
multiple geographies which may 
have differing COVID-19 
guidelines 
1.3, Schedule of Assessments 
7.2, Lost to Follow-up 
8.6, Survival Assessment 
Added an assessment (telephone 
call) of survival at 24 months 
after the date of the Screening 
Visit for subjects who fail to 
return for the Month 24 Visit or 
who discontinue from the study 
before completing the 24-month 
observation period 
Obtain additional information 
on the outcome of ALSP 
1.3, Schedule of Assessments 
Reclassified collection of CSF 
for biomarker evaluation as an 
optional CSF Biomarker 
Sub-study 
Reduce subject burden 
2.3, Benefit/Risk Assessment 
Modified the last sentence related 
to the risk of CSF sampling 
Clarify that the risk of CSF 
sampling (lumbar puncture) 
only applies to those who 
participate in the optional CSF 
Biomarker Sub-study 
4.2.2, Pharmacodynamic 
(Biomarker) Endpoints 
Removed paragraph 2 (rationale 
for measurement of cytokines in 
in blood) 
Not relevant (cytokines will 
only be measured in CSF) 
Revised several sentences to 
indicate that biomarkers in CSF 
will be determined only in 
subjects who consent to 
participate in the optional CSF 
Biomarker Sub-study 
Clarify study procedures 
Added interferon gamma-
inducible protein 10 (IP-10), and 
monocyte chemoattractant 
protein-1 (MCP-1)  
Provide potential biomarkers for 
evaluation based on emerging 
nonclinical and transitional 
work 
4.3, Definition of End of Study 
Revised definition to include the 
Early Termination (ET) Visit 
Clarify study procedures 

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Section No. and Title 
Description of Change 
Brief Rationale 
5.1, Inclusion Criteria 
Removed reference to CSF 
sampling (i.e., the subject must 
be willing to adhere to the CSF 
sampling schedule) from 
inclusion #2 
Consistency with designation of 
CSF sampling as only required 
for those who agree to 
participate in the optional CSF 
Biomarker Sub-study 
Revised inclusion #7 from 
“subjects who are in stable 
medical condition” to “subjects 
who, in the investigator’s 
opinion, have demonstrated 
clinical progression of their 
ALSP within the past year” 
Clarify inclusion criterion 
Revised inclusion #8 from “a 
score of ≥20 on the MMSE” to 
“a score ≥12 on the MoCA” and 
to allow subjects with a score >7 
to be enrolled with sponsor 
approval 
The MMSE scale was removed; 
therefore, the entry criterion was 
amended to use the MoCA 
assessment (which was retained) 
Deleted inclusion criterion 
related to kindred subjects 
(previously inclusion #12) 
Change in study population  
Deleted inclusion criterion 
related to a negative COVID-19 
test within 72 hours before 
Baseline (previously inclusion 
#14) 
Consistency with removal of 
mandatory COVID-19 testing 
from Schedule of Assessments  
5.2, Exclusion Criteria 
Added a note that exclusion #4 
(contraindications for undergoing 
a lumbar puncture) only applies 
to subjects who agree to 
participate in the optional CSF 
Biomarker Sub-study 
Clarify exclusion criterion 
Added “previous HSCT within 
12 months prior to 
Screening/Baseline” as exclusion 
criterion #11 
Change in study population  
7.1, Subject Discontinuation/ 
Withdrawal from the Study 
Added information pertaining to 
withdrawal of consent 
Clarify study procedures 
8.1.2, Medical/Family History 
and Demographic Information 
Revised section to indicate that 
“relevant” medical history would 
be recorded 
Clarify study procedures 
8.1.4, Documentation of CSF1R 
Gene Mutation 
Removed second sentence 
(kindred subjects must have a 
first degree relative with ALSP 
and CSF1R mutation) 
Change in study population 
8.2.1, Blood for NFLs and 
Soluble CSF1R Analysis 
Removed references to cytokine 
panel and TREM2 
Only to be evaluated in CSF 

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Section No. and Title 
Description of Change 
Brief Rationale 
8.2.2, Magnetic Resonance 
Imagining 
Revised types of MRIs that will 
be collected to include FLAIR 
Changed to align with imaging 
acquisition guidelines 
8.4.3, Columbia-Suicide 
Severity Rating Scale (C-SSRS) 
Clarified that the 
Screening/Baseline evaluation 
should be conducted by a 
qualified healthcare professional 
to assess whether it is safe for the 
subject to participate in the study 
Clarify study procedures 
10.1.2, Financial Disclosure 
Removed section 
Information will be included in 
the Clinical Trial Agreement 
10.1.6, Data Quality Assurance 
Removed section 
Information will be included in 
the Clinical Trial Agreement 
10.2, Appendix 2, Definitions 
and Procedures for Recording, 
Evaluating, Follow-up, and 
Reporting of Adverse Events 
and Serious Adverse Events 
Minor wording changes 
Reflect process at Vigil 
Overall 
Minor grammatical corrections 
and editorial changes 
Correct minor errors, unrelated 
to content, in previous protocol 
or for consistency with the 
changes summarized above 
Abbreviations: ADL = activities of daily living, ALSP = adult-onset leukoencephalopathy with axonal 
spheroids and pigmented glia, CSF = cerebrospinal fluid, CSF1R = colony-stimulating factor 1 receptor, 
CIBIC+ = Clinician Interview Based Impression of Change + Caregiver Input, FLAIR = fluid-attenuated 
inversion recovery, HSCT = hemopoietic stem cell transplant, MDS-UPDRS = Movement Disorders – 
Unified Parkinson’s Disease Rating Scale, MINT = Multilingual Naming Test, MMSE = Mini-Mental State 
Examination, MoCA = Montreal Cognitive Assessment, MRI = magnetic resonance imaging, 
SF-36 = 36-Item Short Form Health Survey, TFC = Total Functional Capacity, TREM2 = triggering 
receptor on myeloid cells 2. 
10.5.2 
Amendment 2: Protocol Version 3.0 (22 Mar 2022) 
Overall Rationale for Amendment 
The overall rationale for this amendment is to revise the classification of the subjects to 
be enrolled in the study to reflect the ALSP patient population. 
 
Section No. and Title 
Description of Change 
Brief Rationale 
1.1, Study Endpoints, 
Pharmacodynamic (Biomarker) 
Endpoints 
3.2.1, Pharmacodynamic 
(Biomarker) Endpoints 
8.2.1 Blood for NfL Analysis 
Revised the first bullet in the 
pharmacodynamic (biomarker) 
endpoints to remove references 
to soluble colony stimulating 
factor 1 receptor (CSF1R) in 
blood. 
Only to be evaluated in CSF 
 

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Section No. and Title 
Description of Change 
Brief Rationale 
1.1, Number of Subjects 
9.1, Sample Size Determination 
Changed planned sample size 
from up to 36 subjects 
(approximately 30 subjects with 
symptomatic ALSP and 
6 asymptomatic carriers of the 
CSF1R gene mutation) to up to 
50 subjects are planned for 
enrollment (of which 
approximately 20% of subjects 
will be classified as ‘Prodromal 
ALSP’ and the remaining 
subjects will have ‘Definitive 
ALSP’. Prodromal ALSP is 
defined as ALSP meeting 
radiologic but not full clinical 
criteria. 
Increase in sample size due to 
change in study population 
1.1, Number of Subjects 
 
Clarified that if a subject that has 
been classified as a ‘Prodromal 
ALSP’ patient progresses while 
on study such that they meet the 
definition of a ‘Definitive ALSP’ 
patient, the subject will be 
reclassified as ‘Definitive ALSP’ 
and another ‘Prodromal ALSP’ 
spot will open for enrollment.  
Clarification on how subjects 
will be classified on study if 
they progress from ‘Prodromal 
ALSP’ to ‘Definitive ALSP’ 
while on study. 
1.2, Schema 
1.3, Schedule of Assessments 
Revised Figure 1 and Schedule 
of Assessments to include 
biomarkers in blood collection at 
the Month 6 visit. 
Consistency with changes in 
study design and Schedule of 
Assessments  
1.3, Schedule of Assessments 
Added Urine pregnancy test at 
each visit. 
Ensure consistency between the 
Schedule of Assessments and 
Section 8.4.5. 
1.3, Schedule of Assessments  
Added Coagulation at the 
Screening/Baseline and Month 
12 Visits for the Optional CSF 
Biomarker Sub-study 
participants. 
Ensure that the site can safely 
proceed with CSF biomarker 
collection at each visit. 
5.1, Inclusion Criteria 
Changed classification of 
Symptomatic ALSP to Definitive 
ALSP 
Change in study population. 

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Section No. and Title 
Description of Change 
Brief Rationale 
Revised inclusion criteria #6 to 
have more than two findings of 
clinical signs or symptoms and 
further defined MRI findings 
needing to have bilateral cerebral 
white matter lesions with or 
without thinning of the corpus 
callosum. 
 
Change inclusion criteria 6 to 
align with “Definitive ALSP” 
per Konno et, 2018. 
 
Revised inclusion #8 to not allow 
subjects with a score >7 and <12 
to be enrolled with sponsor 
approval 
Change in study population  
Revised inclusion criteria #9 to 
only allow for non-ambulatory 
subjects that were not related to 
ALSP progression. 
Change in study population  
Changed classification of 
Asymptomatic ALSP to 
Prodromal ALSP 
Change in study population.  
Added inclusion criteria #12 to 
ensure that subjects with 
Prodromal ALSP have MRI 
findings consistent with ALSP. 
Change in study population. 
5.2, Exclusion Criteria 
Added examples for exclusion #5 
for examples of what subjects 
should be excluded from the 
study for not being able to 
undergo an MRI and that patients 
with renal impairment and 
contraindication for the use of 
MRI contrast agent may be 
enrolled and have non-contrast 
MRI exams.(e.g., implants not 
compatible for MRI, 
claustrophobia, inability to 
remain still that will prevent 
acquisition of a good quality 
scan) 
Clarify exclusion criterion 
 
Revised inclusion criteria #11 to 
allow for the inclusion of 
subjects who have had HSCT 
longer than 6 months from 
baseline visit. 
Change in study population 

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Section No. and Title 
Description of Change 
Brief Rationale 
8.2.2, Magnetic Resonance 
Imagining 
Revised types of MRIs to T1 
(with or without contrast). 
Changed to align with imaging 
acquisition guidelines 
Included note that subjects may 
be given light sedation if they are 
unable to lie still during 
scanning. 
Clarify study procedures 
Overall 
Minor grammatical corrections 
and editorial changes 
Correct minor errors, unrelated 
to content, in previous protocol 
or for consistency with the 
changes summarized above 
Abbreviations: ALSP = adult-onset leukoencephalopathy with axonal spheroids and pigmented glia, 
CSF = cerebrospinal fluid, CSF1R = colony-stimulating factor 1 receptor, HSCT= hematopoietic stem cell 
therapy, MRI = magnetic resonance imaging, NfL = neurofilament light chain.  
 
10.5.3 
Amendment 3: Protocol Version 4.0 (03-Oct-2023) 
Overall Rationale for Amendment 
The overall rationale for this amendment is to expand the observation period of the study 
from 24 months to 36 months to allow for the collection of additional data on the natural 
history of adult-onset leukoencephalopathy with axonal spheroids and pigmented glia 
(ALSP) and to extend the window to capture disease progression from prodromal ALSP 
to definitive ALSP. Additional revisions to clarify study procedures were also 
incorporated. 
 
Section No. and Title 
Description of Change 
Brief Rationale 
Cover Page, Short Title 
Synopsis, Short Title 
Changed short title from Natural 
History Study in ALSP to 
Illuminate. 
Administrative change to provide 
additional study identifier. 
Sponsor Signatories 
Changed Vigil signatory from 
Spyros Papapetropoulos, MD, PhD 
to Christopher Silber, MD. 
Change in sponsor personnel. 
1.1, Protocol Synopsis, Study 
Endpoints 
3.2, Study Endpoints 
Revised the study endpoints to 
include the change from baseline to 
Months 30 and/or 36 
Change in study design to extend the 
study from 24 to 36 months and to 
add visits at Months 30 and 36. 
1.1, Protocol Synopsis, Study 
Endpoints, Clinical Outcome 
Endpoints, Cognitive Assessments 
3.2.2, Clinical Outcome Endpoints; 
3.2.2.1, Cognitive Assessments 
Changed CDR® + NACC-FTD to 
CDR® + NACC-FTLD. 
Correct previous error. 
1.1, Protocol Synopsis, Study 
Endpoints, Clinical Outcome 
Endpoints, Motor Assessments 
(Ambulatory Subjects) 
3.2.2, Clinical Outcome Endpoints; 
3.2.2.2, Motor Assessments 
(Ambulatory Subjects) 
Removed “change from Baseline to 
Months 6 and 12 in gait and balance 
assessments (BioSensics wearable 
sensors) in ambulatory subjects at 
selected sites” as a study endpoint. 
Removed as an assessment to reduce 
subject burden. 

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Section No. and Title 
Description of Change 
Brief Rationale 
1.1, Protocol Synopsis, Brief 
Summary 
4.1, Study Design 
Revised the duration of the study 
from 24 months to 36 months and 
modified the study visits and 
assessments to reflect the addition of 
visits at Months 30 and 36. 
Change in study design to extend the 
study from 24 to 36 months and to 
add visits at Months 30 and 36. 
 
Added a provision for 
discontinuation from this study to 
enter a VGL101 clinical study and 
information related to the ET Visit 
for such subjects. 
Clarify study procedures. 
1.1, Protocol Synopsis, Number of 
Subjects 
9.1, Sample Size Determination 
Changed the number of subjects 
from up to 50 subjects to 
approximately 60 subjects. 
Provide flexibility for dropouts and 
simultaneous enrollment at sites at 
the end of subject recruitment. 
1.1, Protocol Synopsis, Treatment 
Groups and Duration 
Revised the duration of subject 
follow-up from 24 months to 
36 months. 
Change in study design. 
1.2, Schema 
Revised the schematic to include 
additional visits at Months 30 and 
36. 
Change in study design. 
1.3, Schedule of Assessments 
Added visits at Months 30 and 36. 
Collect additional data on the 
natural history of ALSP and extend 
the window to capture disease 
progression from prodromal to 
definitive ALSP. 
Added a blood draw for biomarkers 
at Month 18. 
Correct previous omission. 
Removed Month 24 as the ET visit 
and revised the schedule of 
assessments at the Month 24 visit to 
match the schedule of assessments 
at the Month 12 visit. 
Change in study design to change 
the ET visit from Month 24 to 
Month 36. 
Removed sensor-based gait and 
balance assessments at selected sites 
for the schedule of assessments. 
Reduce subject burden. 
Revised several footnotes to reflect 
the addition of the Month 30 and 
Month 36 visits and the change in 
the ET visit from Month 24 to 
Month 36. 
Change in study design. 
 
Added a footnote to state that, at the 
discretion of the investigator, the 
CDR®+NACC-FTLD may not need 
to be administered if there are no 
signs or symptoms of cognitive 
impairment (i.e., normal score on 
the MoCA) or if the subject does not 
have a caregiver who has provided 
informed consent for the study. 
Clarify study procedures. 

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Section No. and Title 
Description of Change 
Brief Rationale 
 
Added that the FAQ, NPI-12, and 
Zarit Burden Interview will not be 
completed if the subject does not 
have a caregiver who has provided 
informed consent for the study. 
Clarify study procedures. 
 
Added a footnote to state that, for 
subjects who discontinue from this 
study to enroll in a VGL101 clinical 
study, blood biomarker collection 
will be performed once for both the 
ET Visit of this study and the 
Screening/Baseline Visit of the 
VGL101 study and will be analyzed 
as part of both studies.  
Clarify study procedures. 
 
Added a footnote to state that, for 
subjects who discontinue from this 
study to enroll in a VGL101 clinical 
study, an MRI will be collected once 
for both the ET Visit of this study 
and the Screening/Baseline Visit of 
the VGL101 study and will be 
analyzed as part of both studies.  
Clarify study procedures. 
 
Added a footnote to state 1) that, for 
subjects who participate in the CSF 
Sub-study and who discontinue from 
this study to enroll in a VGL101 
clinical study, CSF biomarker 
collection will be performed at the 
Screening or Baseline Visit of the 
VGL101 clinical study and will be 
analyzed as part of both studies, and 
2) that If CSF collection is not 
included at the Screening or 
Baseline Visit of the VGL101 
clinical study, CSF biomarker 
collection will be done at the ET 
Visit of this study.  
Clarify study procedures. 
4.3, Definition of End of Study 
Changed the end of study from 
Month 24/Early Termination (ET) to 
Month 36/Early Termination (ET). 
Change in study design. 
5.1, Inclusion Criteria 
Revised inclusion #10 to require 
subjects who meet the criteria for 
definitive ALSP to have a caregiver. 
Ensure that a caregiver is available 
to complete the scales for subjects 
with definitive ALSP. 
Added exclusion #13 to state that 
subjects who meet the criteria for 
prodromal ALSP and who later meet 
the criteria for definitive ALSP must 
have a caregiver to assist them. 
Ensure that a caregiver is available 
to complete the scales for the 
subjects once they progress to 
definitive ALSP. 
5.2, Exclusion Criteria 
Removed reference to MRI contrast 
agents from exclusion #5. 
Contrast MRIs will no longer be 
done in this study as available data 
suggest that there is insufficient 
evidence to pursue contrast-
enhanced MRI as a biomarker for 
ALSP. 

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Section No. and Title 
Description of Change 
Brief Rationale 
Revised exclusion #11 from subjects 
who have previously undergone 
HSCT within 6 months prior to 
Screening/Baseline to subjects who 
have previously undergone HSCT or 
plan to undergo HSCT within 
12 months of the Screening/Baseline 
visit. 
Ensure that subjects who enter the 
study will not undergo HSCT for the 
first 12 months, which could 
confound the assessment of the 
natural history of ALSP. 
 
Added a note to exclusion #12 to 
state that subjects who are receiving 
VGL101 in a clinical study may 
enroll in this study after conclusion 
of their participation in the VGL101 
clinical study. 
Allow subjects who are treated with 
VGL101 in therapeutic studies to 
enroll in this study. 
7.1, Subject Discontinuation/ 
Withdrawal from the Study 
Changed the ET visit from Month 24 
to Month 36. 
Change in study design. 
7.1, Subject Discontinuation/ 
Withdrawal from the Study 
8.2; Pharmacodynamic (Biomarker 
Assessments); 8.2.1, Blood for NfL 
Analysis 
Added that, for subjects who 
discontinue from this study to enroll 
in a VGL101 clinical study, blood 
biomarker collection will be 
performed once for both the ET 
Visit of this study and the 
Screening/Baseline Visit of the 
VGL101 study and will be analyzed 
as part of both studies.  
Clarify study procedures. 
7.1, Subject Discontinuation/ 
Withdrawal from the Study 
8.2; Pharmacodynamic (Biomarker 
Assessments); 8.2.2, Magnetic 
Resonance Imagining 
Added that, for subjects who 
discontinue from this study to enroll 
in a VGL101 clinical study, an MRI 
will be collected once for both the 
ET Visit of this study and the 
Screening/Baseline Visit of the 
VGL101 clinical study and will be 
analyzed as part of both studies. 
Clarify study procedures. 
7.1, Subject Discontinuation/ 
Withdrawal from the Study 
8.4, Safety Assessments; 8.4.1, 
Adverse Events 
Revised the time period for 
collection of adverse events to 
through Month 24 (for subjects who 
complete the study before 
implementation of Amendment 3), 
Month 36 (for subjects who 
complete the study after 
implementation of Amendment 3), or 
the ET Visit. 
Clarify procedures as a result of the 
change in study duration. 

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Section No. and Title 
Description of Change 
Brief Rationale 
7.1, Subject Discontinuation/ 
Withdrawal from the Study 
8.5, Optional CSF Biomarker Sub-
study 
Added that 1) for subjects who 
participate in the CSF Sub-study and 
who discontinue from this study to 
enroll in a VGL101 clinical study, 
CSF biomarker collection will be 
performed at the Screening or 
Baseline Visit of the VGL101 
clinical study and will be analyzed 
as part of both studies, and 2) if CSF 
collection is not included at the 
Screening or Baseline Visit of the 
VGL101 clinical study, CSF 
biomarker collection will be done at 
the ET Visit of this study.  
Clarify study procedures. 
7.2, Lost to Follow-up 
8.6, Survival Assessment 
Revised the timing of the contact to 
assess survival to 24 months (for 
subjects who withdraw from the 
study before implementation of 
Amendment 3) and 36 months (for 
subjects who withdraw from the 
study after implementation of 
Amendment 3) after the date of the 
subject’s Screening Visit. 
Clarify procedures as a result of the 
change in study duration. 
8.1.1, Informed Consent 
10.1.2, Informed Consent Process 
Revised section to indicate that 
subjects who meet the criteria for 
definitive ALSP must have a 
caregiver who is willing to provide 
informed consent and that subjects 
who meet the criteria for prodromal 
ALSP and later develop definitive 
ALSP must have a caregiver who is 
willing to provide informed consent. 
Consistency with changes in 
inclusion criteria #10 and #13, 
respectively. 
8.2, Pharmacodynamic (Biomarker) 
Assessments 
8.3, Clinical Outcome Assessments 
8.4, Safety Assessments 
Revised the text throughout each 
section to include the Month 30 and 
Month 36 visits and to match the 
Schedule of Assessments (Table 1). 
Change in study design. 
8.3.1.2, Clinical Dementia Rating 
Scale plus National Alzheimer’s 
Coordinating Center-Frontotemporal 
Lobar Degeneration 
(CDR®+NACC-FTLD) 
Changed previous scale (CDR® + 
NACC-FTD) to CDR® + NACC-
FTLD. 
Correct previous error. 
Added a statement that, at the 
discretion of the investigator, 
CDR®+NACC-FTLD may not need 
to be administered if there are no 
signs or symptoms of cognitive 
impairment (i.e., normal score on 
the MoCA) or if the subject does not 
have a caregiver who has provided 
informed consent for the study. 
Clarify study procedures. 
8.3.1.3, Brief Assessment of 
Cognition (BAC) 
Revised description of scale. 
Correct previous errors. 

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Section No. and Title 
Description of Change 
Brief Rationale 
8.3.4.1, Functional Assessment 
Questionnaire (FAQ) 
8.3.4.2, Neuropsychiatric Inventory 
– 12 Item Version (NPI-12) 
8.3.4.4, Zarit Burden Inventory 
Added a statement in each section to 
say that the scales will only be 
completed if the subject has a 
caregiver who has provided 
informed consent to participate in 
the study. 
Clarify study procedures. 
8.3, Clinical Outcome Assessments; 
8.3.2.3, Gait and Balance 
Assessments (BioSensics Wearable 
Sensors) in Ambulatory Subjects at 
Selected Sites 
Removed section. 
Removed as an assessment to reduce 
subject burden. 
8.4, Safety Assessments; 8.4.1, 
Adverse Events 
Revised the time period for 
collection of adverse events to 
through Month 24 (for subjects who 
complete the study before 
implementation of Amendment 3), 
Month 36 (for subjects who 
complete the study after 
implementation of Amendment 3), or 
the ET Visit. 
Clarify procedures as a result of the 
change in study duration. 
8.5, Optional CSF Biomarker Sub-
study 
Added a footnote to state 1) that, for 
subjects who participate in the CSF 
Sub-study and who discontinue from 
this study to enroll in a VGL101 
clinical study, CSF biomarker 
collection will be performed at the 
Screening or Baseline Visit of the 
VGL101 clinical study and will be 
analyzed as part of both studies, and 
2) that If CSF collection is not 
included at the Screening or 
Baseline Visit of the VGL101 
clinical study, CSF biomarker 
collection will be done at the ET 
Visit of this study.  
Clarify study procedures. 
9.1, Sample Size Determination 
Removed reference to the 
percentage of subjects with 
prodromal ALSP. 
Allow enrollment of individuals 
with prodromal ALSP to be 
discontinued at sponsor discretion. 
Abbreviations: ALSP = adult-onset leukoencephalopathy with axonal spheroids and pigmented glia, CTD® + NACC-
FTD = Clinical Dementia Rating Scale plus National Alzheimer’s Coordinating Center-Frontotemporal Dementia, 
CTD® + NACC-FTLD = Clinical Dementia Rating Scale plus National Alzheimer’s Coordinating Center-
Frontotemporal Lobar Degeneration, ET = early termination, FAQ = Functional Assessment Questionnaire, HSCT= 
hematopoietic stem cell therapy, MoCA = Montreal Cognitive Assessment, MRI = magnetic resonance imaging, NPI-
12 = Neuropsychiatric Inventory – 12-Itrem Version.  
 

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INVESTIGATOR SIGNATURE PAGE 
 
Protocol Title: 
A Natural History Study of Patients with Adult-Onset 
Leukoencephalopathy with Axonal Spheroids and Pigmented Glia 
(ALSP) 
Protocol Number: 
VGL101-01.002 
Version: 
5.0 
Date: 
02 Oct 2024 
 
I have read this protocol and agree to conduct this study in accordance with all 
stipulations of the protocol and in accordance with all consensus ethical principles 
derived from international guidelines including the Declaration of Helsinki and Council 
for International Organizations of Medical Sciences (CIOMS) International Ethical 
Guidelines, applicable International Conference on Harmonisation (ICH) Good Clinical 
Practice (GCP), and applicable laws and regulations. 
 
 
 
 
Signed: 
 
 
Date: