A Two-Stage, Dose-Escalation and Safety & Efficacy Study of Bilateral Intraparenchymal Thalamic and Intracisternal/Intrathecal Administration of AXO-AAV-GM2 in Tay-Sachs or Sandhoff Disease
Phase: PHASE1
Conditions: Tay-Sachs Disease, Sandhoff Disease
Sponsor: Terence Flotte

Clinical Protocol AXO-GM2-001 
 
Study Tite: A Two-Stage, Dose-Escalation and Safety & EƯicacy Study of Bilateral 
Intraparenchymal Thalamic and Intracisternal/Intrathecal Administration of AXO-AAV-GM2 
in Tay-Sachs or SandhoƯ Disease  
 
NCT Number: NCT04669535 
 
Protocol Version : Version 8  
 
Protocol Date : 9 June 2023 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
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CLINICAL STUDY PROTOCOL AXO-GM2-001 
A TWO-STAGE, DOSE-ESCALATION AND SAFETY & EFFICACY STUDY OF 
BILATERAL INTRAPARENCHYMAL THALAMIC AND 
INTRACISTERNAL/INTRATHECAL ADMINISTRATION OF AXO-AAV-GM2 IN 
TAY-SACHS OR SANDHOFF DISEASE 
 
 
 
 
 
 
Sponsor:
UMass Chan Medical School 
55 Lake Ave North 
Worcester, MA 01655 
Clinical Research Organization: 
Premier Research 
One Park Drive, Suite 130 
Box 13608 
Research Triangle Park, NC 27709-0006 
(919) 627-9100 
www.premier-research.com 
Protocol Number: 
AXO-GM2-001 
Study Drug Name: 
AXO-AAV-GM2 
Development Phase: 
Two-Stage; Phase 1-3 (Stage 1: Phase 1, 
Stage 2: Phase 2/3) 
Protocol Version: 
Version 8.0 
Protocol Version Date: 
9 June 2023  
Protocol Version Supersedes: 
Version 7.0 
 
 
 
 
CONFIDENTIAL 
This clinical study protocol is confidential and proprietary property of UMass Chan Medical 
School. This document may not be reproduced or communicated to a third party without the 
prior written permission of UMass Chan Medical School. 

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SPONSOR SIGNATURE 
Protocol Title: 
A Two-Stage, Dose-Escalation and Safety & Efficacy Study of Bilateral 
Intraparenchymal Thalamic and Intracisternal/Intrathecal Administration of AXO-AAV-GM2 in 
Tay-Sachs or Sandhoff Disease 
 
Protocol Number: 
AXO-GM2-001 
This clinical study protocol was subjected to critical review. The information contained within is 
consistent with current knowledge of the risks and benefits of the investigational product, as well 
as with the moral, ethical, and scientific principles governing clinical research as set out in the 
Declaration of Helsinki, and the guidelines on Good Clinical Practice. 
 
 
 
 
 
 
Terence Flotte, MD 
Chief Research Officer 
UMass Chan Medical School 
Date: 
 
 

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INVESTIGATOR’S AGREEMENT 
I have received and read the Investigator’s Brochure for AXO-AAV-GM2. I have received and 
read the AXO-GM2-001 Clinical Study Protocol and agree to conduct the study as outlined. I 
agree to maintain the confidentiality of all information received or developed in connection with 
this protocol. 
 
 
 
 
 
Printed Name of Investigator 
 
 
 
 
 
Signature of Investigator 
 
 
 
Date: 
 
 

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1. 
SYNOPSIS 
 
Name of Sponsor/Company: 
UMass Chan Medical School, Worcester, MA 01655 USA 
Name of Investigational Product: AXO-AAV-GM2 
Name of Active Ingredients: rAAVrh8-HEXA (also referred to as AAVrh8-HEXA and 
AAVrh8-CB-ci-HEXA in this protocol) and rAAVrh8-HEXB (also referred to as AAVrh8-HEXB and 
AAVrh8-CB-ci-HEXB in this protocol) 
Title of Study: 
A Two-Stage, Dose-Escalation and Safety & Efficacy Study of Bilateral Intraparenchymal Thalamic 
and Intracisternal/Intrathecal Administration of AXO-AAV-GM2 in Tay-Sachs or Sandhoff Disease 
Study Center(s): Up to 3 U.S. sites 
Principal Investigator: 
Terence R. Flotte, MD 
UMass Chan Medical School 
55 Lake Ave. North 
Worcester, MA 01655 
Studied Period (years): 
Estimated date first participant enrolled: 2020 
Estimated date last participant completed: 2028 
Phase of Development: 
Stage 1: Phase 1; Stage 2: Phase 2/3. 
Objectives: 
Stage 1: 
Stage 1 Primary Objective: 
• To assess the safety and tolerability of AXO-AAV-GM2 
Stage 1 Secondary Objective: 
• To identify the optimal AXO-AAV-GM2 dose for Stage 2 
Stage 1 Exploratory Objectives: 
• To determine the impact of treatment with AXO-AAV-GM2 on clinical function as 
assessed by neurocognitive, adaptive, developmental, neurological and motor 
assessments 
• To assess changes in biomarkers of disease activity 
• To assess neurodegenerative and myelination imaging biomarkers following 
AXO-AAV-GM2 infusion 
• To assess peripheral and central nervous system integrity following AXO-AAV-GM2 
infusion 

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Stage 2:
Stage 2 Primary Objectives: 
• To assess the safety and efficacy of surrogate biomarkers of disease activity following 
AXO-AAV-GM2 infusion 
• To assess motor function following AXO-AAV-GM2 infusion 
Stage 2 Secondary Objectives: 
• To assess surrogate biomarkers of disease 
• To evaluate the biodistribution of AXO-AAV-GM2 
• To evaluate clinical function as assessed by neurocognitive function, neurodevelopment, 
and motor function 
Stage 2 Exploratory Objectives: 
• To further determine the impact of treatment with AXO-AAV-GM2 on clinical function 
as assessed by neurocognitive, adaptive, developmental and motor assessments 
• To assess biomarkers of disease activity 
• To assess neurodegenerative and myelination imaging biomarkers 
• To assess peripheral and central nervous system integrity following AXO-AAV-GM2 
infusion 
Long-term Follow-up (LTFU): 
Objectives: 
• Continued monitoring of Stage 1 and Stage 2 objectives through 5 years post- 
administration 
Study Design: 
The study will be open-label, non-randomized and involve a single 2-part administration of AXO- 
AAV-GM2 by bilateral thalamic (BiTh) and dual intracisternal magna (ICM)/intrathecal (IT) infusion 
into the cerebrospinal fluid (CSF). Participants will undergo an immunosuppression regimen 
beginning prior to and following administration of AXO-AAV-GM2 treatment (Day -7 to Week 24) 
as outlined in Section 8.2. Gene transfer will be administered over the course of two days 
(Section 11.5) as follows: 
• At Visit 1a/Day 1, participants will receive bilateral intraparenchymal infusions of 
AXO-AAV-GM2 into the thalamus (BiTh) 
• At Visit 1b/Day 2, participants will receive ICM/IT infusion of AXO-AAV-GM2 into the 
CSF 
All AXO-AAV-GM2 infusions will be comprised of a 1:1 mixture of rAAVrh8-HEXA and 
rAAVrh8-HEXB. 
The study will be conducted in two stages, as follows: 
Stage 1: Twelve (12) TSD or SD participants will be treated sequentially, in a dose-escalation 
manner, with the objective to assess safety and tolerability, and determine the optimal 

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dose to be studied in Stage 2. Dose selection will be determined from safety, 
biomarker, and relevant imaging, neurological and clinical data. Following gene 
transfer, infantile-onset and juvenile-onset participants will undergo safety and efficacy 
assessments according to the respective Schedule of Assessments Table 15 and 
Table 14, respectively). 
Stage 2: Up to 10 infantile-onset TSD or SD participants will be treated with the optimal dose 
identified in Stage 1, with the objective to determine safety and efficacy (according to 
Table 15). The Primary Clinical Efficacy Endpoint measure will be assessed at 
12-months. 
Stage 1 (Safety and Dose Identification for Stage 2): 
Enrollment into Stage 1 will be performed sequentially, with stepwise dose-escalation of participants. 
• Stage 1 Participant 1 (I or J) will receive a starting dose of AXO-AAV-GM2 that 
corresponds to the same BiTh volume as TSD002 and in ICM/IT volume to achieve an 
equivalent total vector dose to TSD001. The independent Data Safety Monitoring 
Committee (DSMC), in conjunction with the Sponsor, will review all available safety 
data through the 4-week visit and determine whether to proceed with the next participant 
(low dose juvenile-onset participant). 
• Dosing of subsequent participants will only occur after satisfactory DSMC and Sponsor 
review of 4-week safety data from the previously dosed participant as well as 
accumulated safety data from all previously dosed participants in the trial. In the Mid and 
High dose cohorts, after the DSMC has reviewed the 4-week safety data from the first 
(Juvenile) participant, an infantile and second Juvenile participant may be treated 
concurrently. 
An additional participant may be entered at any dose level if a participant is lost to follow-up or 
experiences a ≥ Grade 3 related AE before 4 weeks post-gene transfer. Each staggered participant 
may start limited screening activities, as detailed in the schedule of assessments for juveniles 
(Table 14) and infants (Table 15), respectively. The rest of the study assessments can be pursued only 
once the DSMC and Sponsor approve the dosing of additional participants. 
Gene transfer will be administered over the course of two days (Section 11.5) as follows: 
• At Visit 1a/Day 1, participants will receive bilateral intraparenchymal infusions of 
AXO-AAV-GM2 into the thalamus (BiTh) 
• At Visit 1b/Day 2, participants will receive ICM/IT infusion of AXO-AAV-GM2 into the 
CSF 
All AXO-AAV-GM2 infusions will be comprised of a 1:1 mixture of rAAVrh8-HEXA and 
rAAVrh8-HEXB. 
To ensure venous access and ability to draw protocol specified safety labs, as well as reduce the pain 
associated with difficult blood draws during the study, a central venous catheter may be inserted with 
caregiver consent prior to surgical gene transfer. 
Following gene transfer, Stage 1 juvenile participants will be assessed for safety and efficacy over a 
2-year period, during which they will undergo safety, biomarker, neurocognitive, neurologic and 
motor function assessments according to Table 14. Stage 1 infantile participants will undergo safety, 
biomarker, neurologic and motor function assessments according to Table 15 over a 1-year period. 
Neurologic and motor function assessments may be videotaped. 

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After the last participant in Stage 1 has been dosed and observed for 4 weeks, the DSMC will review 
the cumulative safety data and make a determination regarding the safety of the administered doses. 
The Sponsor will determine the optimal AXO-AAV-GM2 dose regimen to be administered in Stage 2 
based on the DSMC safety recommendation and available biomarker, imaging, and clinical data. The 
DSMC will continue to review accumulated safety data at regular intervals throughout the duration of 
the study. 
Stage 1 – Dose Escalation 
Stage 1 dosing consists of a Starting Dose, Low Dose, Mid Dose, and High Dose (Figure 1). The first 
participant enrolled in the study can be of either sub-type (infantile or juvenile) and will be 
administered the Starting Dose. Prior to dosing of each participant, the DSMC must review available 
safety data from all previously dosed participants and make a recommendation regarding continued 
enrollment and dose escalation.  Additional participants beyond those planned in a cohort may be 
dosed when recommended by the DSMC or requested by the regulatory agency, or if a participant 
within a dose level cohort is lost to follow up or experiences a ≥ Grade 3 related AE before 4 weeks 
post-gene transfer. 
Requirements for dose escalation or progression to Stage 2 of the study are as follows: 
1. Recommendation to continue as planned from DSMC, and: 
• At the Low Dose: at least 4 weeks of safety data are available from 2 juvenile and 1 
infantile participants administered the Low Dose 
• For the Mid Dose and High Dose: 
− 
At least 4 weeks of safety data from at least 1 juvenile participant and 2 infantile 
participants are required to dose escalate. 
− 
In addition, dose escalation of juvenile participants may also occur based on at least 4 
weeks of safety data from at least 2 juvenile participants and may occur prior to 
infantile dose escalation. 
− 
Figure 1: 
Stage 1 Dose Escalation Scheme 
 
 
 
 
 
SD
I/J
LD 
J
LD 
J
LD
I
MD 
I 
MD 
I 
MD 
J 
HD 
I
HD 
I
DSMC 
SD = Starting Dose 
LD = Low Dose 
MD = Mid Dose 
HD = High Dose 
J Blue = Juvenile 
I Green = Infantile 

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Stage 2 (Safety and Efficacy):
The study design and endpoints for Stage 2 will be further refined based on information gathered 
during Stage 1. Current expectations are that upon completion of Stage 1, up to 10 infantile-onset 
participants will be enrolled in Stage 2 of the study. 
LTFU: 
All participants enrolled in Stage 1 and Stage 2 of the trial will be followed up for a total of 5 years 
post-gene transfer. Therefore, upon completion of the 2-year follow-up period, juvenile-onset 
participants will be followed for an additional 3 years according to the assessments outlined in 
Table 16. Upon completion of the 12-month follow-up, Stage 1 and 2 infantile-onset participants will 
be followed for an additional 4 years according to the assessments outlined in Table 17. 
Number of Participants (Planned): 
Stage 1: Twelve (12) participants including juvenile-onset and infantile-onset subjects 
Stage 2: Up to ten (10) infantile-onset participants (To be confirmed based on Stage 1) 
Diagnosis and Main Criteria for Inclusion: 
Inclusion Criteria: 
1. Male or female participants with genetically diagnosed TSD or SD mutations of either HEXA 
gene or HEXB gene 
a. Stage 1 juvenile-onset participants must be ≥ 2 years old and ≤ 12 years old at time of 
gene transfer 
i. Diagnosis consistent with juvenile-onset TSD or SD 
b. Stage 1 infantile-onset participants must be between 6-20 months of age at the time of 
gene transfer 
i. Diagnosis consistent with infantile-onset TSD or SD 
 
2. Juvenile onset participants must demonstrate a minimum of 2 of the following age- 
appropriate clinical features/abilities, confirmed by the site examiner at the time of screening 
and reaffirmed prior to the initiation of immunosuppression: 
a. A Gross Motor Function Classification-MLD (GMFC-MLD) score of 0, 1 or 2. The 
minimum gross motor function (GMFC-MLD level 2) is the ‘ability to walk with support 
and walking without support is not possible (fewer than 5 steps)’. (Participants aged 2-12 
years) Note: Any form of support is permitted; however, the participant must initiate each 
step and complete it for a total of 5 steps. 
b. Fine Motor Function 
− 
For Participants aged 4-12 years: A Manual Ability Classification System (MACS) 
score of I, II, III, or IV. The minimum level of manual ability (level IV) corresponds 
to ‘Handles a limited selection of easily managed objects in adapted situations’. 
− 
For participants aged 2-4 years: attainment of fine motor function/coordination 
abilities and milestones with normal or a reduced quality of performance. That is, the 
ability to coordinate fingers and both hands to play, such as swinging a bat or 
opening a container (pathways.org) OR the ability to use fingertips to pick up small 

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objects, i.e., the child uses pad of his/her thumb and any fingertip to grasp a pellet or 
small object as described in BSID III Fine Motor Sub-test Item #26. . 
c. Speech: 
− 
For participants aged 4-12 years, a speech disturbance score of 0, 1, 2 or 3 on the 
speech disturbance subset of the Scale for Assessment and Rating of Ataxia (SARA). 
The minimum speech requirement is a speech disturbance in which most words can 
be understood, with occasional words difficult to understand secondary to dysarthria. 
− Participants aged 2-4 years who have attained the communication milestone of ability 
to consistently use 2-3 word phrases may be assessed in line with this criterion using 
the speech disturbance subset of the SARA. 
− 
For participants aged 2-4 years who have not yet attained the above communication 
milestone, the minimum requirement is the ability to imitate at least one word, even if 
the imitation consists of vowels only (BSID III, expressive communication subtest, 
item #16) 
3. Infantile onset participants must demonstrate current* or historical† ability to sit without 
support for at least 5 seconds 
* As assessed in item 22 of the Bayley Scales of Infant and Toddler Development, Third 
Edition (BSID-III) Gross Motor Scale or documented medical records 
† Documented within available medical records 
In addition, infantile onset participants must demonstrate a minimum of 3 of the following 
developmental skills confirmed by the site examiner at the time of screening and reaffirmed 
prior to the initiation of immunosuppression: 
a. Head control - While supine, with head in midline turns head symmetrically (score of 3 
on GMFM item 1) 
b. Uses hands to support self while sitting 
c. Reach for an object that is held out for them above their chest while supine 
d. Transfer of object from hand to hand while supine 
e. Eye tracking while supine 
f. 
Looks at an object of interest for at least 3 continuous seconds 
4. Surgical readiness for gene transfer by the routes of administration confirmed by the study 
neurosurgeon*, based on examination and MRI findings 
The following findings will disallow the performance of the BiTh procedure thereby 
excluding the participant from participation: 
• Any scalp and skull related lesion (e.g., vascular, infectious) over the surgical entry 
area 
• Any intracranial lesion (e.g., vascular, cystic, other mass lesions), significant 
immaturity or deformity of the brain anatomy that would make the intended surgical 
trajectory high risk 
The following findings will disallow the performance of the ICM/IT procedure thereby 
excluding the participant from participation: 

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• Any skin related lesion (e.g., vascular, infectious) over the lumbar puncture site 
• Any intraspinal or intracranial lesion in posterior fossa (e.g., vascular, cystic, other 
mass lesions) or significantly deformed, distorted brain, spinal and cisternal anatomy 
that make the intended intrathecal trajectory high risk or not feasible 
* Participants otherwise eligible for study participation but deemed not currently fit for 
neurosurgery may be re-screened at the discretion of the investigator 
5. Participants receiving off-label Zavesca® (miglustat) and/or Tanganil® (acetyl-leucine) must 
be willing to discontinue these therapies 30 days prior to the start of screening 
6. Ability to reliably travel to the study sites for study visits according to the Schedule of 
Assessments 
Exclusion Criteria: 
1. Presence of G269S or W474C mutation in HEXA 
2. Evidence of lower respiratory tract aspiration not easily manageable with thickening of 
feedings or substitution of a modified bottle nipple, as judged on a multi-texture contrast 
swallow. 
3. History of multiple aspiration pneumonias occurring in the past twelve months. 
4. Respiratory support in the form of ventilation (invasive or non-invasive). 
5. History of drug-resistant seizures or status epilepticus 
6. History and/or findings of spinal cord disease that would preclude the lumbar puncture and 
ICM/IT infusion procedures including: 
• Infectious process involving the spinal canal which may cause adhesions or septations in 
the spinal and/or subarachnoid space 
• Previous spinal surgeries 
• History of trauma, bleeding in the spinal canal 
• Vascular or cystic lesions, or any other mass lesion 
• Congenital deformities and malformations involving the spinal canal 
• Posterior fossa findings (low lying cerebellar tonsils, crowded foramen magnum, small or 
absent cisterna magna) 
7. The participant’s parent(s) or legal guardian(s) is unable to understand the nature, scope, and 
possible consequences of the study, or does not agree to comply with the protocol defined 
schedule of assessments 
8. Any prior participation in a study in which a gene therapy vector or stem cell transplantation 
was administered 
9. Immunizations of any kind in the month prior to screening 

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10. Cardiomyopathy or other cardiac disease based on echocardiogram and/or electrocardiogram, 
(ECG) that in the opinion of the Investigator would deem the paticipant unsafe to undergo 
surgical gene transfer 
11. Indwelling ferromagnetic devices that would preclude MRI//MRS/DTI imaging 
12. Ongoing medical condition that is deemed by the Investigator to interfere with the conduct or 
assessments of the study 
13. Current clinically significant infections including any requiring systemic treatment including 
but not limited to human immunodeficiency virus (HIV), Hepatitis A, B, or C 
14. History of or current chemotherapy, radiotherapy or other immunosuppressive therapy within 
the past 30 days. Corticosteroid treatment may be permitted at the discretion of the PI 
15. Clinically significant laboratory abnormalities: 
Based on age-specific reference range and determined by the investigator: 
• 
Total WBC count 
• 
Hemoglobin 
• 
Creatinine 
• 
Pancreatic enzymes 
Based on the following thresholds: 
• 
Platelet count (< 150,000/μL) 
• 
Prothrombin (PT), partial thromboplastin time (PTT) >2X normal 
• 
Liver transaminases (Hy’s Law: > 3x elevations above the ULN of ALT or AST and 
serum total bilirubin > 2xULN) 
16. Participants for whom any of the proposed study procedures or medications (i.e., sirolimus, 
trimethoprim/sulfamethoxazole) would be contraindicated 
17. Failure to thrive, defined as falling 20 percentiles (20/100) in body weight in the 3 months 
preceding Screening/Baseline 
18. Participant is not suitable for participation in the study in the opinion of the Principal 
Investigator 
Investigational Product, Dosage and Route of Administration: 
All infusions will be comprised of a 1:1 mixture of rAAVrh8-HEXA and rAAVrh8-HEXB 
(AXO-AAV-GM2). 
The Surgical Manual will contain detailed specific instructions for administration of 
AXO-AAV-GM2. 
The anatomy of the participant’s brain, spinal cord and subarachnoid space will be assessed by pre- 
operative MRI. (See Section 11.5) 
Gene transfer will be administered over the course of two consecutive days as follows: 

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• At Visit 1a/Day 1, participants will receive bilateral intraparenchymal injections of AXO- 
AAV-GM2 into the thalamus (BiTh) at doses outlined in Table 1. 
• At Visit 1b/Day 2, participants will receive ICM/IT infusion of AXO-AAV-GM2 into the 
CSF via microcatheter at doses outlined in Table 2. 
Table 1: 
Stage 1 Bilateral Intrathalamic (BiTh) Doses – Visit 1a/Day 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Note: Dosing based on final titer of 3.26E+13 vg/mL (1:1 mixture of AAVrh8-HEXA:AAVrh8-HEXB) 
Table 2: 
Stage 1 ICM/IT Doses: Visit 1b/Day 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Note: Dosing based on final titer of 3.26E+13 vg/mL (1:1 mixture of AAVrh8-HEXA:AAVrh8-HEXB) 
• 75% of the intended ICM/IT dose will be infused into the cisterna magna 
• 25% of the intended ICM/IT dose will be infused at a thoracolumbar level (T12/L1) 
The total dose (vg) of AXO-AAV-GM2 that will be administered during Stage 1 per participant 
ranges from 1.42E+14 to 3.56E+14 vg (Table 3). 
Group 
Participant 
Volume of Infusion 
(per thalamus) 
Dose 
(per thalamus) 
Intraparenchymal 
Catheter 
Starting Dose 
Participant (I or J) 
0.18 mL 
5.87E+12 vg 
SmartFlow 
Low Dose 
Participant (J) 
0.36 mL 
1.17E+13 vg 
BrainLab Flexible 
Participant (I) 
0.36 mL 
1.17E+13 vg 
BrainLab Flexible 
Participant (J) 
0.36 mL 
1.17E+13 vg 
BrainLab Flexible 
Cohort 1 
(Mid-Dose) 
Participant (J) 
0.72 mL 
2.35E+13 vg 
BrainLab Flexible 
Participant (I) 
0.72 mL 
2.35E+13 vg 
BrainLab Flexible 
Participant (I) 
0.72 mL 
2.35E+13 vg 
BrainLab Flexible 
Cohort 2 
(High-Dose) 
Participant (I) 
1.25 mL 
4.08E+13 vg 
BrainLab Flexible 
Participant (I) 
1.25 mL 
4.08E+13 vg 
BrainLab Flexible 
 
Group 
Participant 
Total ICM/IT Infusion 
Volume 
Dose 
Starting Dose 
Participant (I or J) 
4.00 mL 
1.30E+14 vg 
       Low Dose 
Participant (J) 
5.25 mL 
1.71E+14 vg 
Participant (I) 
5.25 mL 
1.71E+14 vg 
Participant (J) 
5.25 mL 
1.71E+14 vg 
        Cohort 1 
               (Mid-Dose) 
Participant (J) 
5.25 mL 
1.71E+14 vg 
Participant (I) 
5.25 mL 
1.71E+14 vg 
Participant (I) 
5.25 mL 
1.71E+14 vg 
          Cohort 2 
               (High-Dose)
Participant (I) 
8.40 mL 
2.74E+14 vg 
Participant (I) 
8.40 mL 
2.74E+14 vg 
 

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Table 3: 
Total Vector Dose per Participant: BiTh and IT Dosing 
 
Group
Participant
BiTh Dose
ICM/IT Dose
TOTAL DOSE
Starting Dose 
Participant (I or J)
1.17E+13 vg 
1.30E+14 vg 
1.42E+14 vg 
Low Dose 
Participant (J) 
2.35E+13vg 
1.71E+14 vg 
1.95E+14 vg 
Participant (I) 
2.35E+13vg 
1.71E+14 vg 
1.95E+14 vg 
Participant (J) 
2.35E+13vg 
1.71E+14 vg 
1.95E+14 vg 
                
Cohort 1 
(Mid-Dose) 
Participant (J) 
4.70E+13 vg 
1.71E+14 vg 
2.18E+14 vg 
Participant (I) 
4.70E+13 vg 
1.71E+14 vg 
2.18E+14 vg 
Participant (I) 
4.70E+13 vg 
1.71E+14 vg 
2.18E+14 vg 
               
Cohort 2 
(High-Dose)
Participant (I) 
8.15E+13 vg 
2.74E+14 vg 
3.56E+14 vg 
Participant (I) 
8.15E+13 vg 
2.74E+14 vg 
3.56E+14 vg 
          Note: Dosing based on final titer of 3.26E+13 vg/mL (1:1 mixture of AAVrh8-HEXA:AAVrh8-HEXB) 
Stage 2 dosing regimen will be determined based on Stage 1 results. 
Duration of treatment: AXO-AAV-GM2 will be administered as a single, two-part procedure 
Reference Therapy, Dosage and Mode of Administration: N/A 
Criteria for Evaluation: 
Stage 1 
Stage 1 Primary Endpoint: 
• The incidence, severity, seriousness, and relatedness to treatment of treatment emergent 
adverse events (TEAEs) as graded NCI CTCAE v5.0 
Stage 1 Secondary Endpoints: 
• Safety and immunologic response endpoints 
• Changes in vital signs including weight 
• Changes in physical examination findings 
• Changes in clinical safety laboratory tests 
• Immunosuppression response markers 
Stage 1 Exploratory Endpoints: 
• Changes from baseline in developmental age-appropriate clinical function assessments 
− 
Infantile participants: Bayley Scales of Infant and Toddler Development, Third 
Edition (BSID-III), Hammersmith Infant Neurological Examination Section 2 
(HINE-2; motor), Clinical Global Impression (CGI), Vineland-3 Neurological exam 

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− 
Juvenile participants: Neurocognitive function (as measured by the Wechsler, 
WPSSI, BSID-III depending on the participant’s developmental age), Vineland-3, 
CGI, Neurological exam, fine and gross motor function and classification (as 
measured by GMFM-88, GMFC-MLD, timed motor function tests, 9-hole peg test, 
and the Manual Ability Classification System (MACS)) 
• Biomarker changes from baseline in: 
− 
Serum HEXA activity level 
− 
CSF HEXA activity level 
− 
GM2 ganglioside in CSF 
• Change from baseline in brainstem auditory evoked response (BAER) and visual evoked 
response (VER) from baseline to Week 12 and Week 48 
• MRI brain volume and Diffusion Tensor Imaging (DTI) indices of myelination and brain 
water change from baseline to Week 12 and Week 48 
• MRS indices of metabolite accumulation change from baseline to Week 12 and Week 48 
Stage 1 Juvenile-Onset Participant Efficacy: 
Biologic and clinical efficacy endpoint measures will be performed for juvenile-onset participants 
enrolled in Stage 1 of the study. These endpoints will be analyzed in a descriptive manner, separately 
from that of the infantile-onset participants. 
Stage 2 
Stage 2 Primary Endpoint(s): 
• Clinical Function: BSID-III Gross Motor domain change from baseline to Week 48 
(12 months) 
• Surrogate Biologic Marker: CSF HexA activity change from baseline to Visit 9/Week 48 
Stage 2 Secondary Endpoints(s): 
• Changes in Biomarkers: 
− 
Serum HexA activity levels change from baseline to Week 48 (12 months) 
− 
CSF GM2 ganglioside levels change from baseline to Week 48 (12 months) 
• Biodistribution: Serum and CSF vector DNA levels will be measured over 48 weeks (12 
months) to assess the pharmacokinetics of AXO-AAV-GM2 
• Clinical Function: 
− 
BSID-III Composite score change from baseline over Week 48 
− 
Proportion of Motor Milestone responders based on Hammersmith Infant 
Neurological Examination (HINE) Section 2 from baseline to Week 48 
Responder defined as: 
i. The participant demonstrated at least a 2-point increase in the motor milestones 
category of ability to kick or achievement of maximal score on that category 
 

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(touching toes), or a 1-point increase in the motor milestones of head control, 
rolling, sitting, crawling, standing, or walking 
AND 
ii. Among the 7 motor milestone categories (with the exclusion of voluntary grasp), 
the participant demonstrated improvement (as defined in [i]) in more categories 
than worsening 
• Proportion of infantile-onset participants maintaining the ability to sit without support as 
assessed in HINE Section 2 at Week 48 
Stage 2 Exploratory Endpoint(s): 
• Changes from baseline in developmental age-appropriate clinical function assessments as 
measured by BSID-III, HINE-2 (Motor), CGI, Neurologic exam, and Vineland-3 
• Biomarker changes from baseline over 5 years in: 
− 
Serum HEXA activity level 
− 
CSF HEXA activity level 
− 
GM2 ganglioside in CSF 
• Change from baseline in brainstem auditory evoked response (BAER) and visual evoked 
responses (VER) from baseline to Week 12, Week 24, and Week 48 
• MRI brain volume and Diffusion Tensor Imaging (DTI) indices of myelination and brain 
water change from baseline to Week 12 and Week 48 
• MRS indices of metabolite accumulation change from baseline to Week 12 and Week 48 
Long-term Follow-up 
• Continued assessment of Stage 1 and Stage 2 endpoints for a total of 5 years post-gene 
transfer 
Statistical Methods: 
The statistical analysis methods for Stage 1 and Stage 2 will reflect the design elements and 
objectives of each Stage, with descriptive methods and data listings the primary methods used for the 
Stage 1 data. The appropriate statistical models and analyses for Stage 2 will be informed by and 
developed based on the data from Stage 1. Potential comparison of outcomes to external control data 
may be performed and will be described in the statistical analysis plan. 
Sample Size: 
Stage 1: The objectives of Stage 1 are to evaluate safety and tolerability of AXO-AAV-GM2 and 
identify the optimal dose regimen to be used in Stage 2. The sample size of 12 participants 
including infantile and juvenile participants is expected to be sufficient to allow assessment 
of both the safety of the neurosurgical procedure and the stepwise evaluation of escalating 
BiTh and ICM/IT doses. Furthermore, biomarker, imaging and clinical data collected in 
Stage 1 are intended to inform the appropriate dose to progress to Stage 2. 
Stage 2: The Primary Efficacy Endpoints for Stage 2 will be the BSID-III Gross Motor domain 
change from baseline to Week 48 (12 months) and CSF HexA activity change from baseline 
to Week 48 (12 months). The sample size of up to 10 participants is not based upon 

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hypothesis testing assumptions but rather the desire to assess neurodevelopment of 
participants at ages when they would be expected to be declining based on natural history 
data. 
General Methods: 
Stage 1 outcomes analysis will focus on comparisons of individual participant data using graphical 
displays (e.g., line-scatterplots of each participant’s outcomes over time) to allow for visual 
inspection of any trends between the participants and within participants over time. 
Stage 2 will include a comprehensive assessment of both efficacy and safety outcomes tabulated and 
presented using both descriptive and inferential statistics (where applicable) where specified. 
Comparisons to external data sources (e.g., literature, natural history study data) may be performed as 
the data allow. The appropriate statistical models and analyses for Stage 2 will be informed by and 
developed based on the data from Stage 1 and will be described in the statistical analysis plan. 

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2. 
TABLE OF CONTENTS, LIST OF TABLES, AND LIST OF 
FIGURES 
TABLE OF CONTENTS 
SPONSOR SIGNATURE ................................................................................................................ 2 
INVESTIGATOR’S AGREEMENT ................................................................................................ 3 
1. 
SYNOPSIS .................................................................................................................... 4 
2. 
TABLE OF CONTENTS, LIST OF TABLES, AND LIST OF FIGURES ................ 17 
3. 
LIST OF ABBREVIATIONS AND DEFINITIONS OF TERMS ............................. 22 
4. 
INTRODUCTION ...................................................................................................... 25 
5. 
NATURAL HISTORY OF TSD AND SD ................................................................. 27 
6. 
SCIENTIFIC RATIONALE ....................................................................................... 31 
6.1. 
Clinical Experience ..................................................................................................... 32 
7. 
STUDY OBJECTIVES ............................................................................................... 35 
7.1. 
Stage 1 ......................................................................................................................... 35 
7.1.1. 
Stage 1 Primary Objective .......................................................................................... 35 
7.1.2. 
Stage 1 Secondary Objective ...................................................................................... 35 
7.1.3. 
Stage 1 Exploratory Objectives ................................................................................... 35 
7.2. 
Stage 2 ......................................................................................................................... 35 
7.2.1. 
Stage 2 Primary Objectives ......................................................................................... 35 
7.2.2. 
Stage 2 Secondary Objectives ..................................................................................... 35 
7.2.3. 
Stage 2 Exploratory Objectives ................................................................................... 36 
7.3. 
Long-term Follow-up .................................................................................................. 36 
7.3.1. 
Long-term Follow-up Objectives ................................................................................ 36 
8. 
INVESTIGATIONAL PLAN ..................................................................................... 37 
8.1. 
Overall Study Design .................................................................................................. 37 
8.1.1. 
Stage 1 (Safety and Dose Selection for Stage 2): ........................................................ 37 
8.1.1.1. 
Stage 1 – Dose Escalation ........................................................................................... 38 
8.1.2. 
Stage 2 (Safety and Efficacy) ...................................................................................... 39 
8.1.3. 
LTFU ........................................................................................................................... 39 
8.2. 
Prophylactic Immune Tolerance Induction (ITI) Regimen ......................................... 40 
8.2.1. 
Use of Rescue Steroids................................................................................................ 42 
8.3. 
Study Justification ....................................................................................................... 43 

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8.3.1. 
Study Design ................................................................................................................43 
8.3.2. 
Immune Tolerance Induction (ITI) Regimen Justification ..........................................43 
8.3.3. 
AXO-AAV-GM2 Dose Rationale ...............................................................................44 
8.3.3.1. 
AXO-AAV-GM2 Dose Rationale Based on Early Clinical Data and 
Nonclinical Scaling ..................................................................................................... 44 
8.3.3.2. 
AXO-AAV-GM2 Vector Infusion Volume Scaling from NHPs for 
Intrathalamic Delivery ................................................................................................44 
8.3.3.3. 
AXO-AAV-GM2 Vector Dose Volume Scaling from NHPs for ICM/IT 
Dosing ........................................................................................................................ 45 
8.3.3.4. 
Calculation of Safety Margins based on Scaled Dose Volumes from NHP 
Safety Study (Hex-004) ...............................................................................................46 
8.3.4. 
AXO-AAV-GM2 Planned Dose Escalation .................................................................47 
8.3.4.1. 
AXO-AAV-GM2 BiTh Clinical Dose Escalation Strategy .........................................47 
8.3.4.2. 
AXO-AAV-GM2 ICM/IT Clinical Dose Strategy ......................................................51 
8.3.4.3. 
AXO-AAV-GM2 Total Vector Dose Summary .........................................................52 
8.4. 
Number of Participants ................................................................................................ 53 
8.5. 
Treatment Assignment ................................................................................................53 
8.6. 
Dose Adjustment Criteria ............................................................................................53 
8.7. 
Potential Risks ............................................................................................................53 
8.7.1. 
Potential Risks with AXO-AAV-GM2 .......................................................................53 
8.8. 
Criteria for Study Termination .....................................................................................53 
9. 
SELECTION AND WITHDRAWAL OF PARTICIPANTS .....................................65 
9.1. 
Participant Inclusion Criteria ...................................................................................... 65 
9.2. 
Participant Exclusion Criteria ......................................................................................67 
9.3. 
Participant Withdrawal Criteria ..................................................................................68 
9.4. 
Study Stopping Criteria ...............................................................................................68 
10. 
TREATMENT OF PARTICIPANTS .........................................................................70 
10.1. 
Description of Study Drug ..........................................................................................70 
10.2. 
Concomitant Medications ...........................................................................................70 
10.3. 
Treatment Compliance ................................................................................................71 
10.4. 
Randomization and Blinding ..................................................................................... 71 
11. 
STUDY DRUG MATERIALS AND MANAGEMENT ............................................72 
11.1. 
Study Drug ..................................................................................................................72 

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11.2. 
Study Drug Packaging and Labeling ...........................................................................72 
11.3. 
Study Drug Storage .....................................................................................................72 
11.4. 
Study Drug Preparation ...............................................................................................72 
11.5. 
AXO-AAV-GM2 Administration ...............................................................................72 
11.5.1. 
Stage 2 Dosing ............................................................................................................73 
11.6. 
Study Drug Accountability ..........................................................................................73 
11.7. 
Study Drug Handling and Disposal .............................................................................73 
12. 
ASSESSMENT OF EFFICACY .................................................................................74 
13. 
SAFETY PARAMETERS ..........................................................................................75 
13.1. 
Vital Signs, Height, and Weight .................................................................................75 
13.2. 
Physical Examination ..................................................................................................75 
13.3. 
Electrocardiogram (ECG), Electroencephalogram (EEG) ..........................................75 
13.4. 
Laboratory Assessments ..............................................................................................75 
13.4.1. 
Hematology .................................................................................................................75 
13.4.2. 
Blood Chemistry .........................................................................................................76 
13.4.3. 
Urinalysis ....................................................................................................................76 
13.4.4. 
Virus Serology ............................................................................................................76 
13.4.5. 
CNS .............................................................................................................................76 
13.4.6. 
Immunology ................................................................................................................76 
13.4.7. 
Vector Shedding ..........................................................................................................76 
13.5. 
Chest X-Ray ................................................................................................................76 
13.6. 
Imaging: MRI, MRS, DTI ...........................................................................................76 
13.7. 
Ophthalmology ............................................................................................................77 
13.8. 
Brainstem Auditory Evoked Response (BAER) .........................................................77 
13.9. 
Adverse and Serious Adverse Events .........................................................................77 
13.9.1. 
Definition of Adverse Events ......................................................................................77 
13.9.1.1. 
Adverse Event (AE) ....................................................................................................77 
13.9.1.2. 
Serious Adverse Event (SAE) .....................................................................................77 
13.9.1.3. 
Adverse Events of Special Interest (AESI) .................................................................78 
13.10. 
Relationship to Investigational Product, Study Procedure and Administration 
System .........................................................................................................................78 
13.11. 
Recording Adverse Events ..........................................................................................79 

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13.12. 
Reporting Adverse Events........................................................................................... 79 
13.13. 
Reporting Device Deficiencies .................................................................................... 80 
14. 
STATISTICS .............................................................................................................. 81 
14.1. 
Sample Size ................................................................................................................. 81 
14.2. 
General Methods ......................................................................................................... 81 
14.3. 
Analysis Populations .................................................................................................... 82 
14.4. 
Primary Efficacy Endpoints ........................................................................................ 82 
14.5. 
Secondary Efficacy Endpoints .................................................................................... 82 
14.6. 
Safety Endpoints ......................................................................................................... 84 
15. 
ACCESS TO SOURCE DATA/DOCUMENTS FOR MONITORING ..................... 85 
15.1. 
Audits and Inspections ................................................................................................. 85 
15.2. 
Institutional Review Board (IRB) ............................................................................... 85 
16. 
QUALITY CONTROL AND QUALITY ASSURANCE .......................................... 86 
16.1. 
Deviations from Protocol ............................................................................................ 86 
17. 
STUDY COMMITTEES ............................................................................................ 87 
17.1. 
Independent Data and Safety Monitoring Committee (DSMC) .................................. 87 
18. 
ETHICS....................................................................................................................... 88 
18.1. 
Ethics Review ............................................................................................................. 88 
18.2. 
Ethical Conduct of the Study ...................................................................................... 88 
18.3. 
Written Informed Consent ........................................................................................... 88 
19. 
DATA HANDLING AND RECORDKEEPING ........................................................ 89 
19.1. 
Retention of Records ................................................................................................... 89 
20. 
PUBLICATION POLICY ........................................................................................... 90 
21. 
LIST OF REFERENCES ............................................................................................ 91 

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LIST OF TABLES 
Table 1: 
Stage 1 Bilateral Intrathalamic (BiTh) Doses – Visit 1a/Day 1 ..................................12 
Table 2: 
Stage 1 ICM/IT Doses: Visit 1b/Day 2 ......................................................................12 
Table 3: 
Total Vector Dose per Participant: BiTh and IT Dosing ............................................13 
Table 4: 
Abbreviations and Specialist Terms ............................................................................22 
Table 5: 
Motor Development Timeline .....................................................................................29 
Table 6: 
Scaled Human Vector Dose Volume from NHP (Hex-004) for BiTh Infusion ..........45 
Table 7: 
Scaled Human Vector Dose Volume from NHP Safety Study (Hex-004) for 
CSF Infusion ...............................................................................................................46 
Table 8: 
Safety Margins for Intrathalamic Vector Delivery and Infusion Volume ...................46 
Table 9: 
Safety Margins for ICM/IT Vector Delivery and Infusion Volume ............................47 
Table 10: 
Study AXO-GM2-001 Stage 1 BiTh Dose Escalation Plan ........................................49 
Table 11: 
Study AXO-GM2-001 Stage 1 Calculated Vd for Thalamic Infusion by 
Participant (results shown per thalamus) .....................................................................50 
Table 12: Study AXO-GM2-001 Stage 1 ICM/IT Infusion Volume and Dose by 
Participant ...................................................................................................................52 
Table 13: Study AXO-GM2-001 Stage 1 BiTh and ICM/IT Total Vector Dose by 
Participant ...................................................................................................................52 
Table 14: 
Schedule of Juvenile-Onset Participant Assessments .................................................54 
Table 15: 
Schedule of Infantile-Onset Participant Assessments .................................................58 
Table 16: 
Schedule of Juvenile-Onset Participant LTFU............................................................62 
Table 17: 
Schedule of Infantile-Onset Participant LTFU ...........................................................63 
Table 18: 
Investigational Product................................................................................................70 
 
LIST OF FIGURES 
Figure 1: 
Stage 1 Dose Escalation Scheme ..................................................................................7 
Figure 2: 
Residual Activity of HexA and GM2 Turnover in Skin Fibroblast Cell 
Culture .........................................................................................................................26 
Figure 3: 
Sitting Without Propping Milestone Achievement and Loss ......................................27 
Figure 4: 
Average Time with Ability to Sit Without Propping ..................................................28 
Figure 5: 
BSID-III Age-Equivalent Scores for Gross Motor Domain ........................................30 
Figure 6: 
Stage 1 Dose Escalation Scheme ................................................................................39 

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3. 
LIST OF ABBREVIATIONS AND DEFINITIONS OF TERMS 
The following abbreviations and specialist terms are used in this study protocol. 
Table 4: 
Abbreviations and Specialist Terms 
 
Abbreviation or Specialist Term 
Explanation 
AAV 
Adeno-associated virus 
AE 
Adverse Event 
AESI 
Adverse event of special interest 
ADR 
Adverse drug reactions 
ALT 
Alanine aminotransferase 
AST 
Aspartate aminotransferase 
BAER 
Brainstem auditory evoked response 
BiTh 
Bilateral thalamic 
BSA 
Body surface area 
BSID-III 
Bayley Scales of Infant and Toddler Development, 3rd Ed 
BUN 
Blood urea nitrogen 
CBA 
Chicken β-actin 
CBC 
Complete blood count 
CED 
Convection enhanced delivery 
CMP 
Clinical Monitoring Plan 
CNS 
Central nervous system 
CRF 
Case report form 
CRA 
Clinical research associate 
CRO 
Contract research organization 
CRIM 
Cross reactive immunological material 
CSF 
Cerebrospinal fluid 
CT 
Computed Tomography 
CTL 
Cytotoxic T lymphocytes 
DTI 
Diffusion tensor imaging 
DSMC 
Data Safety Monitoring Committee 
ECG 
Electrocardiogram 
EDC 
Electronic Data Capture 
EEG 
Electroencephalogram 
ELISA 
Enzyme-linked immunosorbent assay 
ERT 
Enzyme replacement therapy 
FDA 
Food and Drug Administration 
FBS 
Fetal bovine serum 

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Abbreviation or Specialist Term 
Explanation 
GAA 
Acid α-glucosidase 
GCP 
Good Clinical Practice 
GMO 
Genetically modified organism 
GM2 
Disialotetrahexosylganglioside 
Hex 
Hexosaminidase enzyme 
HexA 
Hexosaminidase A enzyme 
HEXA 
HEXA gene 
HEXB 
HEXB gene 
HIPAA 
Health Insurance Portability and Accountability Act 
HINE 
Hammersmith Infant Neurological Examination 
HIV 
Human immunodeficiency virus 
Hs-CRP 
High-sensitivity C-Reactive Protein 
ICH 
International Conference on Harmonization 
ICM 
Intracisternal Magna 
ICP 
Intracranial Pressure 
ICV 
Intracerebroventricular 
IEC 
Independent Ethics Committee 
IL 
Interleukin 
IND 
Investigational new drug 
IPa 
Intraparenchymal 
IRB 
Institutional Review Board 
IRR 
Infusion related reaction 
ITT 
Intent to treat 
IT 
Intrathecal 
ITI 
Immune tolerance induction 
IV 
Intravenous 
IVIG 
Intravenous immunoglobulin 
LFTs 
Liver function tests 
LP 
Lumbar puncture 
LDH 
Lactate dehydrogenase 
LSD 
Lysosomal storage disorder 
LTFU 
Long term follow-up 
MedDRA 
Medical Dictionary for Regulatory Activities 
MMRM 
Mixed-effect model repeated measure 
MRI 
Magnetic resonance imaging 
MRS 
Magnetic resonance spectroscopy 

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Abbreviation or Specialist Term 
Explanation 
NCI 
National Cancer Institute 
NHP 
Non-human primate 
NHS 
Natural history study 
NIH 
National Institute of Health 
PBMCs 
Peripheral blood mononuclear cells 
PBS 
Phosphate buffered saline 
PICU 
Pediatric Intensive Care Unit 
PI 
Principal Investigator 
PML 
Progressive multifocal leukoencephalopathy 
PO 
Per os 
PT 
Prothrombin time 
PTT 
Partial thromboplastin time 
RBC 
Red blood cell 
SADE 
Serious adverse device effect 
SAE 
Serious adverse event 
SD 
Sandhoff disease 
SMA 
Spinal muscular dystrophy 
SOP 
Standard operating procedure 
TEAE 
Treatment emergent adverse event 
Th 
thalamus 
TSD 
Tay-Sachs disease 
UNL 
Upper normal limit 
Vd 
Volume of distribution 
VER 
Visual evoked responses 
Vi 
Volume of infusion 
WBC 
White blood cell 
YO 
Year old 

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4. 
INTRODUCTION 
Tay-Sachs disease (TSD) and Sandhoff disease (SD) are lysosomal storage disorders (LSDs) 
caused by a deficiency in the enzyme β-N-acetyl-D-hexosaminidase A (HexA), which is 
responsible for GM2 ganglioside degradation. (Ferreira and Gahl 2017) Gangliosides are the 
main glycolipids of neuronal cell plasma membranes which ensure normal cellular activities. 
(Sandhoff and Harzer 2013) HexA is an isoenzyme consisting of α and β subunits which are 
encoded by the HEXA and HEXB genes, respectively. TSD is caused by mutations in HEXA 
encoding the α subunit, whereas SD is caused by mutations in HEXB encoding the β subunit. 
Both forms of GM2 gangliosidosis are caused by overwhelming storage of GM2 ganglioside 
within neurons throughout the central nervous system (CNS), which is normally degraded in the 
lysosome by the isozyme HexA. The resulting neuronal dysfunction and cell death induces the 
primary symptoms of the disease: motor impairment, seizures, and sensory impairments. The 
progression and symptoms associated with TSD and SD are virtually indistinguishable as they 
arise from dysfunction of the same lysosomal enzyme (HexA) and storage product (GM2). 
There are 3 categories of GM2 gangliosidoses defined by the age of symptom onset: infantile, 
juvenile, and late-onset. Those with infantile-onset have the most severe mutations and despite 
achieving very early developmental milestones at expected age, quickly plateau and regress. 
Infantile-onset individuals are often diagnosed due to developmental delays, hypotonia, and 
exaggerated startle response beginning on average at approximately 5 months of age; however, 
diagnosis is made on-average at approximately 13 months of age (Smith et al. 2012). These 
infants and toddlers eventually develop hypotonia, seizures, swallowing difficulties and progress 
to a semi-vegetative state. Bley and colleagues reported the first survival analysis of patients 
affected by infantile-onset GM2 gangliosidosis, with only half surviving beyond the age of 3 
years and one-quarter surviving to the age of 5 years (Bley et al. 2011). Juvenile-onset GM2 
symptomatology generally develops at approximately 5 years of age (range of 1.5 – 15 years) 
with speech, gait or learning difficulties (Maegawa et al. 2006). Death occurs in a similar fashion 
to infantile-onset, but typically occurs in the second decade of life due to the slower rate of 
disease progression. Late-onset GM2 patients often have a normal lifespan, but develop gait 
abnormalities (often wheelchair bound), swallowing and speech difficulties, peripheral 
neuropathy as well as psychiatric manifestations. 
The rate of storage, clinical disease onset and progression severity is largely determined by the 
particular mutation and associated level of residual HexA activity (Solovyeva et al. 2018). 
Conzelmann et al. reported a correlation between residual activity of HexA and the severity of 
GM2 gangliosidosis, through an assay system using radiolabeled GM2 ganglioside as a substrate 
in human fibroblast extracts. (Conzelmann et al. 1983) Hex A activities for infantile, juvenile, 
and adult-onset patients were ≤0.1, 0.5, and 2-4% of normal, respectively. Importantly, healthy 
probands were found to possess activities of 11% to 20% of normal, suggesting that low levels of 
residual HexA activity may be sufficient to achieve ganglioside normalization. This concept is 
further elucidated in Figure 2 below, adapted from Leinekugel, et al 1992 
(Leinekugel et al. 1992). 

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Figure 2: 
Residual Activity of HexA and GM2 Turnover in Skin Fibroblast Cell 
Culture 
 
 
Adapted from Leinekugel et al. 1992 
 
This study demonstrated a correlation between HexA activity and clinical disease severity. 
Groups corresponding to infantile, juvenile, and adult-onset disease forms could be distinguished 
with limited overlap in residual enzyme activity and were well separated from heterozygotes. 
Small increases in HexA activity were associated with milder phenotypes from the severe 
infantile-onset form to the mild adult-onset form. This suggests a range of approximately 5-15% 
of normal HexA activity may result in adequate ganglioside clearance and potentially an 
improved disease course with stabilized motor/neurologic function and achievement of 
developmental milestones. 
HexA expression in serum and cerebrospinal fluid (CSF) will be assessed in this study and holds 
the potential to serve as a surrogate marker of disease. Given the known pathophysiology and 
direct-to-CNS route of administration, CSF HexA expression should be the most likely biologic 
surrogate endpoint that would predict clinical benefit. 
There are no FDA-approved treatments for GM2 gangliosidoses and there is no effective clinical 
treatment generally. Although Miglustat, a glucosylceramide synthase inhibitor approved for 
monotherapy in adult patients with mild to moderate type 1 Gaucher disease, is known to cross 
the blood-brain barrier and commonly used off-label in TSD and SD patients, it is associated 
with peripheral neuropathy, tremor, diarrhea and weight loss (ZAVESCA® Package Insert 2011) 
and has not been observed to result in marked improvement in symptom management or disease 
progression. (Regier et al. 2016, Bembi et al. 2006, Maegawa et al. 2009, Shapiro et al. 2009) 
Current medical care can increase lifespan of affected patients through gastric tube feeding, 
seizure management, and vigilant pulmonary supportive care, but the quality of life is very poor, 
and patients eventually succumb to respiratory infection secondary to aspiration pneumonia (the 
most common cause of death in infantile gangliosidoses). There is a significant unmet clinical 
need for effective treatments for TSD and SD patients. 

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5. 
NATURAL HISTORY OF TSD AND SD 
TSD and SD pathogenesis and natural history are well-described. Few phenotype differences 
exist among TSD and SD, and both are categorized as infantile, juvenile and late/adult based on 
the age of first symptom onset. 
Infantile-onset phenotype disease course includes progressive neurological impairment and death 
in early childhood (Bley et al. 2011, Regier et al. 2016). Recent literature reports highlight the 
homogeneity of the infantile TSD and SD population and their consistent and predictable clinical 
course (Bley et al. 2011, Utz et al. 2017). 
Bley and colleagues (Bley et al. 2011) studied the timing of regression in 97 cases of infantile 
GM2 gangliosidosis. The majority of infantile-onset patients acquired at least some early motor 
milestones, such as head control, reaching, and transferring at the appropriate age (according to 
the Denver Developmental Screening Test II), but few late infant milestones (Bley et al. 2011). 
Mean age at onset of the earliest symptom was 5.0 months (SD 3.3 months). Of the early infant 
milestones, the ability to sit without support or propping provides the most consistent natural 
history outcome. Only 55% of the infantile-onset GM2 patients achieved the ability to sit without 
support (red line in Figure 3; average age of 6.8 months when gained/SD 1.5 months), and 
almost all of those who gained this ability, lost it within 12 months (blue line in Figure 3; 
average age of 13.1 months when lost/ SD 6.8 months). See Figure 3 and Figure 4. 
Figure 3: 
Sitting Without Propping Milestone Achievement and Loss 
 
 
Adapted from Bley et al. 2011 

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Figure 4: 
Average Time with Ability to Sit Without Propping 
 
 
Adapted from Bley et al. 2011 
 
Utz and colleagues recently reported the results of a prospective natural history study intended to 
establish a timeline of clinical changes occurring in infantile-onset gangliosidoses 
(Utz et al. 2017). This study was conducted under clinical trials (NCT00668187 and 
NCT02030015) of the Lysosomal Disease Network (U54NS065768) which is a part of the 
National Institutes of Health (NIH) Rare Diseases Clinical Research Network (RDCRN). 
Patients were enrolled in a natural history study in which clinical events were documented 
prospectively while patients were receiving clinical care. As part of clinical care, some patients 
were placed on a combination regimen, called Syner-G, which consists of miglustat and a very 
low carbohydrate diet, the ketogenic diet. The data for both the natural history study as well as 
Syner-G was obtained through clinical care. Standard clinical care included visits with providers 
at the University of Minnesota a minimum of once yearly. Clinical evaluations were performed 
by specialists in lysosomal diseases which include the following: metabolic geneticist, genetic 
counselor, pharmacotherapist, neurologist, cardiologist, and pediatric psychologist. All patients 
were also followed by providers near their homes, including a neurologist, geneticist and primary 
care physician. Follow-up telephone communications with the parents were made a minimum of 
once every 6 months and were conducted by a pharmacotherapist or clinical geneticist. These 
communications queried about onset of new clinical symptoms and changes in existing 
symptoms. Neurodevelopmental evaluations were completed using the Bayley Scales of Infant 
and Toddler Development®, Third Edition (BSID-III). The BSID-III was administered to all 
participants receiving neurodevelopmental evaluations, regardless of their chronological age. To 
determine functioning outside of the evaluation session, caregivers completed the Vineland 
Adaptive Behavior Scales, Second Edition (Vineland™-II). This measure is standardized for 
individuals from birth to 90-years-old and assesses domains including functional 
communication, daily living skills, social skills, and motor skills (Sparrow et al. 2017). Six- 
month intervals were used to summarize the timing of events for all the patients, corresponding 
with the minimal frequency of follow-up by study staff with patients’ caregivers. 

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Twenty-three patients were enrolled in the study: 8 with infantile GM1 gangliosidosis, 15 with 
infantile GM2 gangliosidosis (9 with infantile TSD and 6 with infantile SD). The median age of 
onset of the first noted symptom for GM2 was 6 months and diagnosis at 15 months. The most 
common clinical changes in the infantile gangliosidoses were onset of hypotonia within the first 
6 months of life, excessive oral and respiratory secretions, gastroesophageal reflux, dysphagia 
(followed by feeding-tube placement), and constipation. Utz and colleagues reported that most 
infantile GM2 patients had some motor developmental delay within the first 6 months of life and 
all patients had a delay by 12-months of age (Table 5). 
Table 5: 
Motor Development Timeline 
 
 
 
Infantile GM2 Motor Skills 
 
 
N 
 
Percent 
Never 
Gained 
 
 
Patient 
Experienced 
Age (Months) divided into 6-Month Intervals at which 
Motor Development Milestones Occurred 
 
0 to 6 
 
7 to 12 
 
13 to 18 
 
19 to 24 
Experienced 
but age 
unknown 
Gained independent head control 
N=14 
0% 
100% 
79% 
7% 
 
 
14% 
Lost independent head control 
N=14 
- 
93% 
 
57% 
21% 
7% 
7% 
Gained ability to sit independently 
N=13 
62% 
39% 
31% 
8% 
15% 
 
 
Lost ability to sit independently 
N=13 
- 
39% 
 
23% 
 
 
 
Gained ability to crawl 
N=13 
100% 
0% 
 
 
 
 
 
Lost ability to crawl 
N=14 
- 
7% 
 
 
7% 
 
 
Based on BSID-III data for GM2 patients only, adapted from Utz et al 2017. 
 
Most patients had documented seizure disorders by 18 months of age, with the most common 
interval for seizure onset occurring between 13 to 18 months of age. Consistent with 
Bley et al. 2011, overall, motor skills that were gained within the first 6–12 months of life were 
lost in most GM2 patients by the age of 2 years. Most patients never gained the ability to crawl, 
and had a median survival for all patients with infantile-onset GM2 of 43.43 months (range for 
ages at death: 33.08–66.83 months). 
There was no statistically significant difference between infantile-onset GM1 and GM2 patients 
when comparing the age of motor skills gained and motor skills lost. Gross motor skill scores 
(based on BSID-III Age Equivalent Scores for Gross Motor Domain) showed rapid decline in 
patients receiving two or more neurodevelopmental evaluations and reached the floor of the 
testing scale by 28 months of age for all tested patients (Figure 5). 

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Figure 5: 
BSID-III Age-Equivalent Scores for Gross Motor Domain 
 
 
Source: Utz et al. 2017. 
 
Maegawa and colleagues used combined retrospective and prospective collection of clinical, 
laboratory, molecular genetics, and imaging data from a cohort of 21 patients with juvenile-onset 
GM2 gangliosidosis, supplemented by a review of 134 cases of the disease reported in medical 
literature (Maegawa et al. 2006). Juvenile GM2 gangliosidosis is clinically heterogeneous, not 
only in terms of age of onset and clinical features but also with regard to the disease course. 
Mean age of onset of earliest symptom was 5.3 +/- 4.1 years (range: 1.5–15 years). Gait 
disturbances are the earliest symptom, followed by speech problems, incoordination, intellectual 
impairment, seizures, extrapyramidal signs, incontinence of sphincters, and upper motor neuron 
signs. Dysphagia, along with diarrhea/constipation, tend to emerge later, with a median onset of 
3 to 3.5 years (Maegawa et al. 2006). This was also the first published analysis of survival in 
juvenile-onset GM2 gangliosidosis, reporting that nearly half of the patients die in the first 
decade and only one quarter live into the late teen years (Maegawa et al. 2006). 

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6. 
SCIENTIFIC RATIONALE 
GM2 accumulation occurs primarily in neuronal cells, therefore, gene therapy must provide 
broad coverage of the brain and spinal cord to adequately address the neurologic deterioration 
associated with this condition. Direct CNS administration of AAVrh8 vectors encoding HEXA 
and HEXB has been shown effective in mouse, cat, and sheep models 
(Cachon-Gonzalez et al. 2006, Cachon-Gonzalez et al. 2012, Bradbury et al. 2013, 
McCurdy et al. 2015, Rockwell et al. 2015, Cachon-Gonzalez et al. 2018), and holds the 
potential for clinical efficacy in human participants with TSD or SD. Extensive preclinical 
efficacy studies of the gene therapy approach used in this protocol have been conducted. 
Results of BiTh and CSF injections of AAVrh8 vectors in animal models of SD, as well as the 
safety and efficacy data for the latest generation of AAVrh8 vectors, supports the combined 
BiTh and ICM/IT delivery of gene therapy in these diseases with expectation of safety and 
potential therapeutic benefit. 
Efficacy and Safety Study of AAVrh8-mHEXA/B in Sandhoff Disease Mice (Study 
Hex-003) 
• Three cohorts of 4-week old SD mice were treated with AAVrh8-mHEXA/B vector 
(1.76E+10, 3.51E+10 or 7.02E+10 vg, based on qPCR titers) by bilateral injection 
into the thalamus combined with unilateral ICV delivery. 
• Intracranial injection of AAVrh8 vectors in SD mice provided evidence of significant 
therapeutic benefit with no apparent major safety concerns. 
• The two top dose groups showed improved survival compared to PBS-treated and 
untreated control SD mice. 
• In the rotarod test, AAV treated SD mice in the two top dose cohorts performed 
significantly better than PBS-treated and untreated control SD mice. Hexosaminidase 
activity (HexA and Hex total) in the brain was significantly greater in vector-treated 
mice, than PBS-treated and untreated SD control mice, and the enzyme level directly 
correlated with AAV vector dose, with highest activity documented in the highest 
dose cohort. 
• GM2 ganglioside content in brain was significantly lower in all AAV treatment 
groups compared to PBS-treated and untreated SD mice. The impact on GM2 
ganglioside content in brain was inversely proportional to the AAV vector dose. No 
significant difference in spinal cord GM2 ganglioside content was apparent. 
 
Safety Study of AAVrh8-cmHEXA/B in Normal Cynomolgus Macaques (Hex-004) 
A safety study was carried out in normal young cynomolgus macaques receiving bilateral 
thalamic injection combined with unilateral ICV injection of a 1:1 admixture of AAVrh8 vectors 
encoding cynomolgus macaque HEXA or HEXB. NHPs received either 9.1E+12 or 2.3E+12 vg, 
based on qPCR titer, which roughly corresponded to the top and bottom doses tested in SD mice 
based on scaling from brain volumes. 
• All animals tolerated the surgical procedure and brain MRI with no complications. 

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• Intracranial administration was well tolerated as was AAV-mediated expression of 
hexosaminidase in the thalamus and other brain regions, albeit with no evidence of 
increased activity in the spinal cord. 
• NHP behavior remained unchanged for the duration of the experiments for all 
cohorts. 
• Hexosaminidase activity above normal levels was documented in thalamic punches of 
all AAV treated NHPs as well as other areas of the brain. Increased enzyme activity 
above normal levels were not apparent for any of the spinal cord regions. 
 
6.1. 
Clinical Experience 
Safety and limited clinical efficacy data are available for AAVrh8HEXA/HEXB from Expanded 
Access Protocol UMMS-GTC-HEX-001 participants TSD001 and TSD002. For both 
participants, the administration procedures were well-tolerated, and the totality of the available 
data from neurology exams, neuromotor skills testing, biomarkers, and brain imaging provide 
early clinical support for proof-of-concept and starting dose selection for the proposed Phase 1 
(Stage 1) study (AXO-GM2-001). The following is a summary of the clinical status of the two 
participants treated with AAVrh8HEXA/HEXB under expanded access, each having achieved the 
13-month post-treatment visit. 
TSD001 
Participant TSD001 is a female with infantile-onset TSD due to two HEXA mutations: a 4-BP 
insertion in exon 11 (c1275-1278), a common Ashkenazi mutation; and a second mutation 
HEXA, c.82 C->T (p.Gln28). Her symptom onset began at 5-6 months with the loss of 
developmental milestones, and at 12 months, TSD001 was noted to have macrocephaly and MRI 
abnormalities. Progression of neurologic declined ensued and TSD was formally diagnosed at 
14 months of age when she presented with non-febrile seizures. At 17 months of age, she 
underwent gastrostomy tube placement for feeding and medication administration. 
AAVrh8HEXA/HEXB administration was performed on 15 November 2018 when TSD001 was 
30 months of age. TSD001 was administered an immune suppression regimen consisting of 
rituximab, sirolimus, and corticosteroids prior to and following receipt of AAVrh8HEXA/HEXB 
transfer to prevent the risks of an inflammatory response to the vector and to protect AAV- 
transduced cells from an immune response to the AAVrh8 capsid. TSD001 underwent vector 
administration to the cerebrospinal fluid (CSF) via lumbar puncture with fluoroscopically guided 
catheter advancement to the cisterna magna where 75% of the dose (~9 mL) was administered 
followed by the remaining 25% of the dose (~3 mL)] at the L1-2 level. Due to her advanced 
stage of disease, BiTh infusion was not performed. The dose, based on ddPCR retesting, was 
1.45E+14 vg (adjusted from preliminary calculated titer of 1.0E+14 vg based on the previous 
qPCR method). The ICM/IT procedure was performed without incident, with mild/moderate 
adverse events (AEs) related to immunosuppression therapy. The immunosuppression regimen 
was continued for 12 weeks post dosing. The only serious adverse events (SAEs) reported to- 
date were from pneumonia at Day 260 post dosing, which resolved following intubation and 
treatment with antibiotics. This was deemed by the investigator to be unrelated to the therapy or 
the procedure. 

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Following gene transfer, participant TSD001’s overall clinical condition has remained stable, 
without deterioration on neurological exam. Mild improvement in trunk tone was noted at the 1 
and 2-month follow up visits, and the parents reported a mild increase in responsiveness. The 
12-month post dosing visit for TSD001 was completed as an at-home visit with the Principal 
Investigator on 15 December 2019. At 12-months post dosing, the participant was noted to have 
continued stabilization of neurological function (as assessed by neurology exam) and motor 
skills as assessed via the Children’s Hospital of Philadelphia Infant Test of Neuromuscular 
Disorders (CHOP INTEND). TSD001 was noted to become seizure-free post dosing and has 
remained so to date. Additionally, she has shown other potential signs of biological activity and 
resultant efficacy including: 1) confirmed transgene expression in CSF at 3 months post dosing; 
2) increased HexA enzyme activity in serum and CSF samples collected at 3 and 6 months post 
dosing (the latest time point these samples were drawn) compared to baseline; and 3) no 
substantial deterioration in white matter myelination on MRI scans at 6 months post dosing (the 
last time point at which MRI scans were performed). 
TSD002 
Participant TSD002 is a female with infantile-onset TSD due to two mutant HEXA alleles 
(heterozygous 1.75kb deletion of exons 11-13 and p.Val381* truncation mutation in exon 10). 
TSD002 was diagnosed shortly after birth due to two siblings affected by infantile-onset TSD. 
Her serum HexA level at one week of age was 1% of normal. Sibling 1 was diagnosed at 2 years 
of age and died at nearly 3 years of age; no genetic reports are available for this child. Sibling 2 
began regressing at 7 months of age, developed seizures within a few months and currently is 
managed with tracheostomy due to recurrent pneumonia. Prior genetic report confirms the same 
two mutations for Sibling 2 as seen in TSD002. 
At the age of 3 months, TSD002 was developmentally normal and asymptomatic. At the time of 
her pre-operative evaluation when she was 6 months of age, she began demonstrating early signs 
and symptoms of TSD with cherry red macula, self-hand stabilization when sitting up, and 
parents described reduced visual and auditory responsiveness. 
TSD002 was administered an immune suppression regimen consisting of rituximab, sirolimus, 
and corticosteroids prior to and following receipt of AAVrh8HEXA/HEXB transfer. She 
underwent BiTh and ICM/IT infusion of AAVrh8HEXA/HEXB on 11 June and 12 June 2019, 
respectively. At the time of gene transfer, the participant was 7 months of age. The total dose, 
based on ddPCR testing, was 6.49E+13 vg (adjusted from preliminary calculated titer of 
4.6E+13 vg based on the previous qPCR method). Based on ddPCR method results, 5.90E+12 
vg; 180 μL was administered per thalamus at infusion rate of 3 μL/min with a rigid infusion 
cannula, and 5.31E13 vg; 5 mL was infused via ICM/IT administration using the flexible 
catheter (75% of dose to ICM/25% to IT). 
A total vector dose of 4.6E+13 vg as determined by qPCR titer was administered, with 180 μL 
infused per thalami (1.548E+12 vg; 180 μL per thalamus at infusion rate of 3 μL/min with a rigid 
infusion cannula) and 5 mL infused via ICM/IT administration (4.3E+13 vg) using flexible 
catheter with 75% of the dose administered at the cisterna magna level and 25% at the 
thoracolumbar level. 

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The BiTh and ICM/IT procedures were performed without incident. Following gene transfer, the 
immunosuppression regimen was continued for 12 weeks. The only SAEs reported to-date were 
from a urinary tract infection at Day 90 post dosing, which resolved following hospitalization 
and treatment with antibiotics and was not considered related to either the gene therapy or the 
procedure. 
The 6-month post dosing visit for TSD002 was completed on November 21, 2019, with stable 
safety monitoring. The CHOP INTEND total score for TSD002 was 60 at baseline and 3 months 
post dosing and dropped to 52 at 6 months. She remains seizure-free post dosing, and has shown 
other potential signs of biological activity with resultant efficacy including: 1) increased HexA 
enzyme activity in serum and CSF samples collected at 3 and 6 months post dosing (the latest 
time point these samples were drawn) compared to baseline; and 2) stabilization of disease on 
MRI scans at 3 months post dosing, with slow decline at 6 months (the last time point at which 
MRI scans were performed). Due to travel limitations caused by the ongoing COVID-19 
pandemic, a telephone/video visit was performed on May 18, 2020 for her 12 month post dosing 
visit. At 16 months post dosing, she was noted to be able to sit for 5 seconds, retained visual 
tracking and response to auditory stimulation. The CHOP-INTEND score could not be 
conducted at the 12 month visit since it needs to be conducted in person. Clinically, TSD002 
remains stable and only mildly symptomatic (as at baseline), whereas sibling 2, with the same 
mutations as TSD002, demonstrated rapid neurodegeneration and milestone regression at similar 
age. 

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7. 
STUDY OBJECTIVES 
7.1. 
Stage 1 
7.1.1. 
Stage 1 Primary Objective 
• To assess the safety and tolerability of AXO-AAV-GM2 
7.1.2. 
Stage 1 Secondary Objective 
• To identify the optimal AXO-AAV-GM2 dose and administration regimen for 
Stage 2 
 
7.1.3. 
Stage 1 Exploratory Objectives 
• To determine the impact of treatment with AXO-AAV-GM2 on Clinical Function as 
assessed by neurocognitive, adaptive, developmental, neurological and motor 
assessments 
• To assess changes in biomarkers of disease activity 
• To assess neurodegenerative and myelination imaging biomarkers following 
AXO-AAV-GM2 infusion 
• To assess peripheral and CNS integrity following AXO-AAV-GM2 infusion 
7.2. 
Stage 2 
7.2.1. 
Stage 2 Primary Objectives 
• To assess surrogate biomarkers of disease activity following AXO-AAV-GM2 
infusion 
• To assess motor function following AXO-AAV-GM2 infusion 
7.2.2. 
Stage 2 Secondary Objectives 
• To assess surrogate biomarkers of disease 
• To evaluate the biodistribution of AXO-AAV-GM2 
• To evaluate clinical function as assessed by neurocognitive function, development, 
and motor function 

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7.2.3. 
Stage 2 Exploratory Objectives 
• To further determine the impact of treatment with AXO-AAV-GM2 on clinical 
function as assessed by neurocognitive, adaptive, developmental and motor function 
• To assess biomarkers of disease activity 
• To assess neurodegenerative and myelination imaging markers following 
AXO-AAV-GM2 infusion 
• To assess peripheral and central nervous system integrity following AXO-AAV-GM2 
infusion 
 
7.3. 
Long-term Follow-up 
7.3.1. 
Long-term Follow-up Objectives 
• Continued monitoring of Stage 1 and Stage 2 objectives through 5 years post- 
administration 

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8. 
INVESTIGATIONAL PLAN 
8.1. 
Overall Study Design 
The study will be open-label, non-randomized, single 2-part administration of AXO-AAV-GM2, 
by bilateral thalamic (BiTh) and dual intracisternal magna (ICM)/intrathecal (IT) administration 
into the CSF. Participants will undergo an immunosuppression regimen beginning prior to and 
following administration of AXO-AAV-GM2 treatment (Day -7 to Week 24) as outlined in 
Section 8.2. Gene transfer will be administered over the course of two days (Section 11.5) as 
follows: 
• At Visit 1a/Day 1, participants will be administered bilateral intraparenchymal 
infusions of AXO-AAV-GM2 into the thalamus (BiTh) 
• At Visit 1b/Day 2, participants will be administered ICM/IT infusion of 
AXO-AAV-GM2 into the CSF 
All AXO-AAV-GM2 infusions will be comprised of a 1:1 mixture of rAAVrh8-HEXA and 
rAAVrh8-HEXB. 
The study will be conducted in 2 Stages: 
Stage 1: Twelve (12) TSD of SD participants will be treated sequentially, in a dose- 
escalation manner, with the objective to assess safety and tolerability, and 
determine the optimal dose to be studied in Stage 2. Dose selection will be 
determined from safety, biomarker, and relevant imaging, neurological and clinical 
data. Following gene transfer, infantile-onset and juvenile-onset participants will 
undergo safety and efficacy assessments according to the respective Schedule of 
Participant Assessments (Table 14 and Table 15). 
Stage 2: Up to 10 infantile-onset TSD or SD participants will be treated with the optimal 
dose identified in Stage 1, with the objective to determine safety and efficacy 
(according to Table 15). The primary clinical efficacy endpoint will be assessed at 
12 months post dosing. 
All participants enrolled in Stage 1 and Stage 2 of the trial will be followed up for a total of 5 
years post gene transfer in the LTFU study, to determine on-going safety and efficacy of the 
treatment. 
8.1.1. 
Stage 1 (Safety and Dose Selection for Stage 2): 
Enrollment into Stage 1 will be performed sequentially, with stepwise dose-escalation of 
participants. 
• To bridge the proposed dosing in this protocol to the early clinical data available from 
expanded access participants, Participant 1 (I or J) will receive the same total dose of 
AXO-AAV-GM2 as TSD001 (treated by ICM/IT infusion only). This will be 
administered with the same BiTh volume TSD002 received (1.17E13 vg/360μL) 
followed with the ICM/IT volume (1.30E14 vg/4.00 mL) for the rest of the dose. The 
independent DSMC, in conjunction with the Sponsor will review all available safety 

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data through the 4-week visit and determine whether to proceed with the next 
participant (low dose juvenile-onset participant). 
• Dosing of subsequent participants will occur after satisfactory DSMC and Sponsor 
review of 4-week safety data from the previously dosed participant as well as 
accumulated safety data from all dosed participants in the trial.  
Each staggered participant may start limited screening activities, as detailed in the schedules of 
assessments Table 14 and Table 15 for juveniles and infants, respectively. The rest of the study 
assessments can be pursued only once the DSMC and Sponsor have approved continued 
enrollment/dosing of the next participant. 
An additional participant may be entered at any dose level if a participant within that dose level 
is lost to follow up or experiences a ≥ Grade 3 related AE before 4 weeks post-gene transfer, or if 
requested by the DSMC or regulatory agency. 
Following gene transfer, Stage 1 juvenile participants will be assessed for safety and efficacy 
over a 2-year period, during which they will undergo safety, biomarker, neurocognitive, 
neurologic and motor function assessments according to Table 14. Stage 1 infantile participants 
will undergo safety, biomarker, neurocognitive, neurologic and motor function assessments 
according to Table 15 over a 1-year period. Neurologic and motor function assessments may be 
videotaped. 
After the last Stage 1 participant has been dosed and observed for 4 weeks, the DSMC will 
review the cumulative safety data and make a recommendation regarding the safety of the 
administered doses. The Sponsor will determine the AXO-AAV-GM2 dose regimen to be 
administered in Stage 2 based on the DSMC safety recommendation and available biomarker, 
imaging and clinical data. The DSMC will continue to review accumulated safety data at regular 
intervals throughout the duration of the study. 
8.1.1.1. 
Stage 1 – Dose Escalation 
Stage 1 dosing consists of a Starting Dose, Low Dose, Mid Dose, and High Dose (Figure 6). The 
first participant enrolled in the study can be either sub-type (infantile or juvenile) and will be 
administered the Starting Dose. Prior to dosing of each participant, the independent DSMC must 
review the available safety data from all previous participants and make a recommendation 
regarding continued enrollment and dose escalation. Additional participants beyond those 
planned in a cohort may be dosed, for example, if requested by the DSMC or regulatory agency, 
or if a participant within a dose level cohort is lost to follow up or experiences a ≥ Grade 3 
related AE before 4 weeks post-gene transfer. 
Requirements for dose escalation or progression to Stage 2 of the study are as follows: 
1. DSMC recommendation to continue as planned, and: 

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• At the Low Dose: at least 4 weeks of safety data are available from 2 juvenile and 1 
infantile participant administered the Low Dose. 
• For the Mid Dose and High Dose: 
− 
At least 4 weeks of safety data from at least 1 juvenile participant and 2 infantile 
participants are required to dose escalate. 
− 
In addition, dose escalation of juvenile participants may also occur based on at least 4 
weeks of safety data from at least 2 juvenile participants and may occur prior to infantile 
dose escalation. 
Figure 6: 
Stage 1 Dose Escalation Scheme 
 
 
 
8.1.2. 
Stage 2 (Safety and Efficacy) 
Up to 10 infantile-onset participants will be enrolled in Stage 2 of the study, which will assess 
safety and efficacy of AXO-AAV-GM2 at the optimal dose identified from Stage 1. The exact 
number of participants to be enrolled in Stage 2 may be revised based on Stage 1 data analysis. 
Following AXO-AAV-GM2 administration, participants participating Stage 2 will be followed 
according to Table 15. 
To ensure venous access and ability to draw protocol specified safety labs, as well as reduce the 
pain associated with difficult blood draws during the study, caregivers will have the option to 
have a central venous catheter inserted into participants after consultation with the principal 
investigator and prior to surgical gene transfer (Table 15). 
8.1.3. 
LTFU 
All participants enrolled in Stage 1 and Stage 2 of the trial will be followed up for a total of 5 
years post gene transfer in the LTFU study. Therefore, upon completion of the 12 month follow- 
up, Stage 1 and Stage 2 infantile-onset participants will be followed for 4 years according to 
Table 17. Upon completion of the 2-year follow-up period, juvenile-onset participants will be 
followed for an additional 3 years according to Table 16. 
SD
I/J
LD 
J
LD 
J
LD
I
MD 
I 
MD 
I 
MD 
J 
HD 
I
HD 
I
DSMC 
SD = Starting Dose 
LD = Low Dose 
MD = Mid Dose 
HD = High Dose 
J Blue = Juvenile 
I Green = Infantile 

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8.2. 
Prophylactic Immune Tolerance Induction (ITI) Regimen 
To prevent the risks of an inflammatory response and to protect AAV-transduced cells from 
immune response to the AAVrh8 capsid and/or transgene, participants will be 
immunosuppressed prior to administration of AXO-AAV-GM2 treatment. The ITI regimen will 
be maintained as described below. 
Starting on Day -7 of the study, the following will be initiated: 
• Rituximab* at 375 mg/m2 BSA (IV infusion) 
*Pre-medication for rituximab infusion will include: 
- acetaminophen 10-15 mg/kg given either PO, g-tube or rectal one time prior to infusion (may 
repeat q 4 hours for temperature >38.3°C) 
- diphenhydramine 1 mg/kg given either PO, g-tube or IV one time prior to infusion (may repeat 1 
mg/kg IV PRN) 
• Solu-Medrol at 10 mg/kg (IV infusion) 
• Sirolimus* at 1.5 mg/m2 BSA/day (PO or by feeding tube) 
*adjustment permitted to achieve trough levels of 7-12 ng/mL 
• Prednisolone at 1-2 mg/kg/day (PO or by feeding tube) 
• Lansoprazole at 1-1.5 mg/kg/day (PO or by feeding tube) 
• Trimethoprim/sulfamethoxazole 2.5 mg/kg/day BID on 2 consecutive days per week 
(PO or by feeding tube) or per PI discretion 
Day -2, Day 1 (BiTh Infusion Day), Day 2 (ICM/IT Infusion Day): 
• Rituximab* at 375 mg/m2 BSA (IV infusion), as needed for persistent CD20 count ≥ 
5% 
*Pre-medication for rituximab infusion will include: 
- acetaminophen 10-15 mg/kg given either PO, g-tube or rectal one time prior to infusion (may 
repeat q 4 hours for temperature >38.3°C) 
- diphenhydramine 1 mg/kg given either PO, g-tube or IV one time prior to infusion (may repeat 1 
mg/kg IV PRN) 
• Continuation of sirolimus*, prednisolone, and lansoprazole dosing (PO or by feeding 
tube) 
*adjustment permitted to achieve trough levels of 7-12 ng/mL 
• Continuation of trimethoprim/sulfamethoxazole 2.5 mg/kg/day BID on 2 consecutive 
days (PO or by feeding tube) or per PI discretion 
Day 2-8: 
• Continuation of sirolimus*, prednisolone, and lansoprazole dosing (PO or by feeding 
tube) 
*adjustment permitted to achieve trough levels of 7-12 ng/mL 
• Continuation of trimethoprim/sulfamethoxazole 2.5 mg/kg/day BID on 2 consecutive 
days per week (PO or by feeding tube) or per PI discretion 

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• IV immunoglobulin (IVIG) ~1000 mg/kg administration – initiate only if 
immunoglobulin levels fall below 500 mL/dL. Dose will be adjusted to maintain 
serum trough levels of 500-1000 mg/dL. Will occur after vector infusion. 
Day 15, Day 22: 
• Continuation of sirolimus*, prednisolone, and lansoprazole dosing (PO or by feeding 
tube) 
*adjustment permitted to achieve trough levels of 7-12 ng/mL 
• Continuation of trimethoprim/sulfamethoxazole 2.5 mg/kg/day BID on 2 consecutive 
days per week (PO or by feeding tube) or per PI discretion 
Week 4/Month 1: 
• Continuation of sirolimus*, prednisolone, and lansoprazole dosing (PO or by feeding 
tube) 
*adjustment permitted to achieve trough levels of 7-12 ng/mL 
• Continuation of trimethoprim/sulfamethoxazole 2.5 mg/kg/day BID on 2 consecutive 
days per week (PO or by feeding tube) or PI discretion 
• IVIG ~1000 mg/kg if IgG levels are below 500 mL/dL. Dose will be adjusted to 
maintain serum trough levels of 500-1000 mg/dL. 
Week 6, Week 8, Week 10: 
• Continuation of sirolimus*, prednisolone, and lansoprazole dosing 
*adjustment permitted to achieve trough levels of 7-12 ng/mL 
• Continuation of trimethoprim/sulfamethoxazole 
• IVIG ~1000 mg/kg if IgG levels are below 500 mL/dL. Dose will be adjusted to 
maintain serum trough levels of 500-1000 mg/dL. 
Week 12/Month 3 to Week 20/Month 5: 
• Initiate prednisolone tapering regimen: 
− Week 12-13: Reduce Dose by 50% 
− Week 13-14:  Reduce week 12-13 Dose by 50% 
− Week 14-15:  Reduce week 13-14 Dose by 50% 
− Week 15-16: Reduce week 14-15 Dose by 50% then stop 
• Lansoprazole to be discontinued following completion of prednisolone tapering 
• Continuation of sirolimus* 
*adjustment permitted to achieve trough levels of 7-12 ng/mL 
• Continuation of trimethoprim/sulfamethoxazole 
• IVIG ~1000 mg/kg if IgG levels are below 500 mL/dL. Dose will be adjusted to 
maintain serum trough levels of 500-1000 mg/dL. 
Week 24/Month 6 
• Initiate weaning of sirolimus: 

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− Week 24-25: reduce dose by 50% (PO or by feeding tube) 
− Week 25-26: reduce Week 24-25 dose by 50% (PO or by feeding tube) 
− Week 26-27: reduce Week 25-26 dose by 50% (PO or by feeding tube) then stop 
• Trimethoprim/sulfamethoxazole to be discontinued following completion of sirolimus 
wean 
 
The ITI regimen will be stopped upon evidence of any of the following severe conditions for 
which no other cause has been identified: (1) intractable, severe opportunistic infections, not able 
to be managed with antibiotic, antifungal or antiviral therapy; (2) renal dysfunction (rising 
creatinine or BUN); (3) severe rash; (4) evidence of CNS problems including seizures or 
encephalopathy; (5) bleeding or clinically significant elevation of bleeding parameters. 
Participants requiring discontinuation of the ITI regimen prior to Visit 1a (Day 1) will not be 
eligible for gene transfer and will be withdrawn from the study. 
 
8.2.1. 
Use of Rescue Steroids 
Triggering criteria: 
A modification of the corticosteroid regimen is indicated if the following events occur in the 
trial: 
1. A positive gamma interferon ELISPOT response to AAVrh8 capsid or HEXA/B 
transgene peptide pools on two successive ELISPOT assays done on or prior to the 
3-month post-dosing time point. Please note that if one ELISPOT is positive, the assay 
should be repeated within 1 to 2 weeks. 
AND EITHER 
2. A worsening of clinical neurological signs or symptoms felt to be indicative of 
inflammation and/or injury, including but not limited to physical and neurological 
examination, CSF analysis and neuroimaging studies. 
OR 
3. An increase in ALT to 2× the pre-dosing level or 3× the upper limit of normal. 
If these conditions are met the following regimen will be completed: 
1. Methylprednisolone administered IV at 10 mg/kg/day for 3 successive days. 
2. Followed by resumption of prednisolone at 2 mg/kg/day for at least 3 weeks prior to 
resumption of the scheduled weaning protocol. 
3. Adjustment of sirolimus dose to achieve a trough level of 10-15 ng/mL for at least 
3 weeks prior to resumption of dosing to achieve a level of 7-12 ng/mL, followed then by 
the scheduled plans for continuation and weaning. 
If these conditions are not met, but the indicators ALT and ELISPOT are trending higher, the 
PI may, at his or her discretion increase the prednisolone dose within the range of 1 to 2 

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mg/kg/day and/or increase the sirolimus dose to achieve a trough level at a higher than the 
prior baseline, but still within the reference range (i.e., still less than 18 ng/ml). 
 
 
8.3. 
Study Justification 
8.3.1. 
Study Design 
The uncontrolled study design is based on the consideration that TSD and SD are rapidly 
progressing and predictably fatal conditions for which natural history data exist with well- 
defined outcome measures very similar to those included in this study (Bley et al. 2011, 
Utz et al. 2017) can be used as a non-concurrent comparative/control group to measure treatment 
effect of AXO-AAV-GM2. 
TSD and SD pathophysiology is well understood, and the natural history data reflect concurrent 
management of the condition during the disease-course of these patients. The natural history data 
highlight the homogeneity of the infantile TSD and SD population and the consistent and 
predictable clinical course involving the attainment of early milestones followed by 
developmental regression within a short time span. These factors allow for results of this study 
to: 1) be clearly interpretable as the treatment effect is expected to exceed the known variability 
in progression, 2) is not affected by patient or investigator motivation or choice of participants 
for treatment, 3) be objectively measured in a manner that reasonably manages and minimizes 
bias, 4) have a strong temporal association with administration of the investigational drug, and 5) 
is consistent with expected pharmacological activity based on the target and animal models. As 
there is limited experience with stereotactic intracerebral infusions in infants, and to manage 
potential safety concerns associated with AAV gene therapy, the first participant dosed in the 
low, mid, and high dose groups of Stage 1 will be a juvenile-onset participant to facilitate the 
stepwise escalation of intra-thalamic infusion volumes and doses. 
 
8.3.2. 
Immune Tolerance Induction (ITI) Regimen Justification 
The prophylactic ITI regimen will be administered starting 7 days prior to gene transfer and will 
continue to week 24 to prevent antibody response to AAV capsid in participants receiving gene 
therapy. The potential for immune modulation to prevent antibody response to AAV capsid in 
participants receiving gene therapy was demonstrated by Corti et. al following a trial of intra- 
diaphragmatic injection of AAV1-GAA in participants with infantile Pompe disease 
(Corti et al. 2017). Three CRIM negative participants receiving AAV1-hGAA had also received 
chronic immune modulation with rituximab and sirolimus due to pre-existing immune responses 
to enzyme replacement therapy (ERT). These participants had no immunologic response to AAV 
capsid proteins or the GAA protein. This was in contrast to the 5 CRIM positive participants who 
had not received immune modulation and had an average 150-fold increase in anti-AAV1 titer 
after exposure to AAV1. 
Immune modulation using rituximab has become the therapy of choice for CRIM negative 
infants to maintain the efficacy of ERT (Elder 2013, Kazi 2017). 
A similar mitigation of antibody response to AAV9 capsid and therapeutic protein has been 
observed in an expanded access trial of intravenous plus ICV administration of rAAV9-hASPA 

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transgene in a child with Canavan disease (Corti et al. 2018). In this study with rituximab and 
sirolimus preconditioning, the immune response was abrogated. 
In another ongoing trial, “Re-administration of Intramuscular AAV9 in Subjects with Late-Onset 
Pompe Disease,” (NCT02240407, IND #17404) a similar immune modulation strategy to ablate 
B- and T-cells (rituximab, sirolimus, methylprednisolone and prednisone) prior to the initial 
exposure to AAV9 by intramuscular injection prevented the formation of antibody against AAV9 
and the GAA transgene. 
The ITI regimen was administered and well-tolerated in the two TSD subjects that are part of an 
ongoing Expanded Access clinical trial for AAVrh8-HEXA/HEXB gene therapy (IND# 18225). 
 
8.3.3. 
AXO-AAV-GM2 Dose Rationale 
 
8.3.3.1. 
AXO-AAV-GM2 Dose Rationale Based on Early Clinical Data and Nonclinical 
Scaling 
AXO-AAV-GM2 will be directly infused into the CNS using BiTh and dual ICM/IT dosing 
approach to maximize the distribution of vector and expressed enzyme throughout the brain and 
spinal cord. This is based on evidence from multiple nonclinical studies, as well as early clinical 
data from the expanded access patients, for the safety and efficacy of AAVrh8-HEXA/HEXB 
administration. To bridge the early clinical data dosages to the proposed doses in this protocol, 
the starting dose was selected as the same BiTh volume as expanded access patient TSD002 and 
an ICM/IT volume that achieves an equivalent total vector dose to expanded access patient 
TSD001. To support dose escalation, this section will provide further rationale based on 
extrapolation from dose volumes evaluated in animals to their equivalent dose in humans. 
Conservative volumetric scaling from animal models to humans for dose calculation was based 
on the targeted regions of the CNS, specifically the volume of the thalamus for IPa 
administration and the volume of the CSF compartment for ICM/IT infusion. 
 
8.3.3.2. 
AXO-AAV-GM2 Vector Infusion Volume Scaling from NHPs for Intrathalamic 
Delivery 
In the cynomolgus macaque safety study (Hex-004), an upper dose of 1.69E+12 vg based on 
qPCR titer in an infusion volume of 0.150 mL was administered to each thalamus and found to 
be safe and well-tolerated. 
Between 6 months and 20 months of age, the most likely age range for infantile patients at the 
time of vector infusion in the Stage 1 clinical trial, the thalamus changes in size less than 15% 
ranging from 4,003 mm3 to 4,573 mm3 (Tutunji et al. 2018). This difference is sufficiently small 
to use a standard volume of a 1YO (4,332 mm3) as representative for infantile patients. This 
facilitates the determination of scaling factors to calculate dose volumes as described below. 
Likewise, for juvenile patients a volume of a 4YO (4,990 mm3) was used for scaling, close to the 
average volume of the thalamus between 2 and 12 years of age, the range used in the inclusion 
criteria for Stage 1 of the clinical trial. 
To determine scaling factors, the volume for the human thalamus is divided by that for the 
cynomolgus non-human primate used in the safety study with a volume of 590 mm3. (Stephen 
Frey, personal communication). As shown below, the scaling factor for juvenile participants was 

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calculated to be 8.5x and infantile participants was calculated to be 7.3x. The scaling factors 
were then multiplied by the NHP dose volume to determine a scaled human equivalent (see 
Table 6). 
 
 
 
𝐽𝑢𝑣𝑒𝑛𝑖𝑙𝑒 𝑠𝑐𝑎𝑙𝑖𝑛𝑔 𝑓𝑎𝑐𝑡𝑜𝑟 
= 
 
𝐼𝑛𝑓𝑎𝑛𝑡𝑖𝑙𝑒 𝑠𝑐𝑎𝑙𝑖𝑛𝑔 𝑓𝑎𝑐𝑡𝑜𝑟 
= 
𝐻𝑢𝑚𝑎𝑛 𝑇ℎ 𝑣𝑜𝑙 
(mm3)1 
= 
𝑁𝐻𝑃 𝑇ℎ 𝑣𝑜𝑙 (mm3)2 
𝐻𝑢𝑚𝑎𝑛 𝑇ℎ 𝑣𝑜𝑙 (mm3)3 = 
𝑁𝐻𝑃 𝑇ℎ 𝑣𝑜𝑙 (mm3)2 
4.99 𝑚𝐿 
 
 
0.59 𝑚𝐿 
4.33 𝑚𝐿 
 
 
0.59 𝑚𝑙 
 
= 8.5𝑥 
 
= 7.3𝑥 
 
1 Volume of human thalamus at 4 years of age, estimated from (Tutunji et al. 2018) 
2 Volume of NHP thalamus provided by Steven Frey (personal communication) 
3 Volume of human thalamus at 1 year of age, estimated from (Tutunji et al. 2018) 
Table 6: 
Scaled Human Vector Dose Volume from NHP (Hex-004) for BiTh Infusion 
 
Participant 
Type 
Max NHP Infusion Vol 
Human Scaling Factor 
Scaled Human Infusion 
Volume Equivalent 
Juvenile 
0.150 mL 
8.5 
1.28 mL 
Infantile 
0.150 mL 
7.3 
1.10 mL 
 
8.3.3.3. 
AXO-AAV-GM2 Vector Dose Volume Scaling from NHPs for ICM/IT Dosing 
In the cynomolgus macaque safety study (Hex-004), a maximum dose of 6.76E+12 vg based on 
qPCR titer and infusion volume of 600 µL was administered to the CSF via a unilateral ICV 
infusion and was found to be safe and well-tolerated (the NHP study employed a dual thalamus 
and CSF dosing strategy). Using the same scaling strategy calculations as described above, the 
scaling factors for human equivalent vector dose volumes were determined. A total CSF volume 
of 170 mL was used for juvenile and 150 mL for infantile patients. Note that the estimated 
human CSF volumes were adjusted upward based on higher CSF volume content noted in 
children with GM2 gangliosidosis (Nestrasil et al. 2018). For the NHP, a total CSF volume of 
13.0 mL was used for the scaling denominator as shown in the equations below. From these 
values, the CSF scaling factor was calculated as 13.1x for juveniles and 11.5x for infantile 
patients. The scaling factors were then multiplied by the NHP dose volume to determine a scaled 
human equivalent (see Table 7). 
 
𝐽𝑢𝑣𝑒𝑛𝑖𝑙𝑒 𝑠𝑐𝑎𝑙𝑖𝑛𝑔 𝑓𝑎𝑐𝑡𝑜𝑟 
= 
 
𝐼𝑛𝑓𝑎𝑛𝑡𝑖𝑙𝑒 𝑠𝑐𝑎𝑙𝑖𝑛𝑔 𝑓𝑎𝑐𝑡𝑜𝑟 
= 
𝐻𝑢𝑚𝑎𝑛 𝐶𝑆𝐹 𝑣𝑜𝑙 (𝑚𝐿)1 = 
𝑁𝐻𝑃 𝐶𝑆𝐹 𝑣𝑜𝑙 (𝑚𝐿)2 
𝐻𝑢𝑚𝑎𝑛 𝐶𝑆𝐹 𝑣𝑜𝑙 (𝑚𝐿)3 = 
𝑁𝐻𝑃 𝐶𝑆𝐹 𝑣𝑜𝑙 (𝑚𝐿)2 
170.0 𝑚𝐿 
 
 
13.0 𝑚𝐿 
150.0 𝑚𝐿 
 
 
13.0 𝑚𝐿 
 
= 13.1 
 
 
= 11.5 

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1 Volume of human CSF estimated from Jang et al. 2019, McAllister et al. 2017, and Nestrasil et al. 2018 
2 Volume of NHP CSF estimated from Poplack et al. 1977 

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Table 7: 
Scaled Human Vector Dose Volume from NHP Safety Study (Hex-004) for 
CSF Infusion 
 
Participant 
Type 
 
Max NHP Vol 
Human: NHP Scaling 
Factor 
Scaled Human 
ICM/IT Infusion 
Volume Equivalent 
Juvenile 
0.600 mL 
13.1 
7.86 mL 
Infantile 
0.600 mL 
11.5 
6.92 mL 
 
8.3.3.4. 
Calculation of Safety Margins based on Scaled Dose Volumes from NHP Safety 
Study (Hex-004) 
The scaled dose volumes for BiTh and ICM/IT delivery, determined above, can be compared to 
the planned doses for the clinical trial. These results inform on the relative difference of the two 
doses and yield a safety factor by dividing the scaled human dose volumes (derived from the 
NHP safety study, Hex-004) by the proposed clinical dose volumes. Values greater than one 
indicate that the dose volumes scaled from the NHP study are higher than the planned dose 
volume resulting in a positive safety margin. The results are shown in Table 8 for intrathalamic 
administration and Table 9 for ICM/IT infusion to the CSF for the different dose groups in the 
planned clinical trial. Overall, the safety margins for BiTh infusion volumes are positive (values 
are ≥ 1.0) for all participants except the infantile-onset participants in Cohort2 (High Dose) 
where the margin is 0.9 (see Table 8). Likewise, the safety margins for ICM/IT are positive 
(values are ≥ 1.0) for all participants except Cohort 2 (High Dose), which have a safety margin 
of 0.9 and 0.8 for juvenile-onset and infantile-onset participants, respectively (see Table 9). 
Table 8: 
Safety Margins for Intrathalamic Vector Delivery and Infusion Volume 
 
 
Group 
 
Participant 
Planned Clinical 
Infusion Volume 
(mL) 
Scaled Human Vector Infusion 
Volume Equivalent (mL) 
 
Safety Margin 
Starting Dose 
Participant (I or 
J) 
0.18 
I: 1.1 
J: 1.28 
I: 6.1 
J: 7.1 
 
Low Dose 
Participant (J) 
0.36 
1.28 
3.6 
Participant (I) 
0.36 
1.1 
3.1 
Participant (J) 
0.36 
1.28 
3.6 
Cohort 1 
(Mid Dose) 
Participant (J) 
0.72 
1.28 
1.8 
Participant (I) 
0.72 
1.1 
1.5 
Participant (I) 
0.72 
1.1 
1.5 
Cohort 2 
(High Dose) 
Participant (I) 
1.25 
1.1 
0.9 
Participant (I) 
1.25 
1.1 
0.9 

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Table 9: 
Safety Margins for ICM/IT Vector Delivery and Infusion Volume 
 
 
Group 
 
Participant 
Planned Clinical 
Infusion Volume 
(mL) 
Scaled Human Vector Infusion 
Volume Equivalent (mL) 
 
Safety Margin 
Starting Dose 
Participant (I or 
J) 
4.00 
I: 6.92 
J: 7.86 
I: 1.7 
J: 2.0 
 
Low Dose 
Participant (J) 
5.25 
7.86 
1.5 
Participant (I) 
5.25 
6.92 
1.3 
Participant (J) 
5.25 
7.86 
1.5 
Cohort 1 
(Mid Dose) 
Participant (J) 
5.25 
7.86 
1.5 
Participant (I) 
5.25 
6.92 
1.3 
Participant (I) 
5.25 
6.92 
1.3 
Cohort 2 
(High Dose) 
Participant (I) 
8.4 
6.92 
0.8 
Participant (I) 
8.4 
6.92 
0.8 
 
8.3.4. 
AXO-AAV-GM2 Planned Dose Escalation 
The dose escalation plan was informed by the nonclinical studies as well as the clinical 
experience from the two participants treated under Expanded Access Protocol UMMS-GTC- 
HEX-001. The BiTh infusion performed on participant TSD002 supported the feasibility and 
safety of the stereotactic BiTh infusion approach using rigid intracerebral infusion catheters and 
sequential, bilateral thalamic infusions, followed the next day by ICM/IT delivery of vector to 
the CSF. To safely increase the dose and volume of BiTh and ICM/IT infusions, while limiting 
the procedural time and duration of general anesthesia, several elements of the dosing process 
will be advanced in a stepwise manner during Stage 1 as described briefly below for BiTh dosing 
(Section 8.3.4.1) and ICM/IT delivery (Section 8.3.4.2). The BiTh and ICM/IT neurosurgical 
procedures will be described in detail within the Surgical Manual. 
The surgical readiness of participants to undergo gene transfer for Study AXO-GM2-001 will be 
confirmed at Visit B (Day -16) by the neurosurgeon based on neurologic examination and MRI 
imaging of the participant’s brain, spinal cord and IT space anatomy. 
The neurosurgeon may determine the participant is not appropriate candidate for BiTh and/or 
ICM/IT infusion based on this assessment as described in the Surgical Manual. 
 
8.3.4.1. 
AXO-AAV-GM2 BiTh Clinical Dose Escalation Strategy 
The stereotactic neurosurgical BiTh infusion procedure will be performed by a pediatric 
neurosurgeon at UMMS according to Table 10 and as described in the Surgical Manual. 
Participant 1 (I or J) will undergo the same procedure as that for the previously treated Expanded 
Access Protocol UMMS-GTC-HEX-001 participant TSD002 with rigid infusion cannulas for IPa 

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delivery (Smartflow, ClearPoint). Intra-operative CT scan may be performed in the OR to verify 
the catheter locations in the target thalamus. 
Flexible infusion catheters (BrainLab) will be used and simultaneous infusion of 360 µL per 
thalamus will be performed on Low Dose participants. An intra-operative Computed 
Tomography (CT) scan of the brain will be performed shortly after bilateral infusion catheter 
placement to verify appropriate location in the thalamic targets. An additional intra-operative CT 
scan of the brain (with limited number of images focused on the thalamus to minimize radiation 
exposure) will be performed mid-way through the infusion to assess any infusion related changes 
and/or possible bleeding or injury. The infusions will be stopped in the event of an adverse event 
or CT scan finding at the discretion of the neurosurgeon. 
Cohort 1 (Mid-Dose) participants will undergo simultaneous BiTh infusion of 720 µL per 
thalamus with the flexible infusion catheters. Intra-operative CT scan of the brain will be 
performed as described above. Cohort 2 (High-Dose) participants will receive 1,250 µL per 
thalamus with flexible infusion catheters (Table 10). Intra-operative CT scan of the brain will be 
performed as described above, and at the discretion of the surgeon, an additional scan may be 
performed. Based on the safety results from prior participants, the neurosurgeon will have the 
option to complete the infusion for Cohort 2 within the OR under general anesthesia with 
intubation, or alternatively, in the Pediatric Intensive Care Unit (PICU) under light sedation. If 
the decision is made to carry out the infusion within the OR, intra-operative CT scan of the brain 
will be performed as described above. Additional intra-operative CT scans of the brain may be 
performed to assess any infusion related changes and/or possible bleeding or injury. If the 
surgeon elects to complete the infusion within the PICU, intra-operative CT scan of the brain 
will be performed shortly after bilateral infusion catheter placement to verify appropriate 
location in the thalamic targets. The participant will then be transferred to the PICU for 
completion of the infusion. All participants will have brain MRI after completion of the infusion 
and removal of the cannulas. Additional details can be found in the Surgical Manual. 
The optimal dose regimen to be used in Stage 2 will be identified from Stage 1 data including 
safety, biomarker, and additional data. 

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Table 10: 
Study AXO-GM2-001 Stage 1 BiTh Dose Escalation Plan 
 
 
 
Participant 
 
Rate 
Dose per 
Thalamus 
(vg) 
Volume per 
Thalamus 
(µL) 
 
Infusion Time 
Catheter 
Type 
 
Infusion Setting 
Starting 
Dose 
Participant (I or 
J) 
 
4 µL/min 
 
5.87E+12 vg 
 
180 
90 min (1.5 hours) 
(45 min x 2, 
sequentially) 
Rigid 
(SmartFlow) 
 
Operating Room † 
 
 
 
 
Low Dose 
 
Participant (J) 
 
4 µL/min 
 
1.17E+13 vg 
 
360 
90 min (1.5 hours) 
(simultaneous 
bilaterally) 
 
 
 
 
 
 
Flexible 
(BrainLab) 
 
Operating Room † 
 
Participant (I) 
 
4 µL/min 
 
1.17E+13 vg 
 
360 
90 min (1.5 hours) 
(simultaneous 
bilaterally) 
 
Operating Room † 
 
Participant (J) 
 
4 µL/min 
 
1.17E+13 vg 
 
360 
90 min (1.5 hours) 
(simultaneous 
bilaterally) 
 
Operating Room † 
 
Cohort 1 
(Mid Dose) 
Participant (J) 
4 µL/min 
2.35E+13 vg 
720 
180 min (3 hours) 
(simultaneous 
bilaterally) 
Operating Room † 
Participant (I) 
4 µL/min 
2.35E+13 vg 
720 
Operating Room † 
Participant (I) 
4 µL/min 
2.35E+13 vg 
720 
Operating Room † 
Cohort 2  
(High Dose) 
Participant (I) 
4 µL/min 
4.08E+13 vg 
1,250 
312 min (5.2 hours) 
(simultaneous 
bilaterally) 
Operating Room †† or PICU* 
Participant (I) 
4 µL/min 
4.08E+13 vg 
1,250 
Operating Room †† or PICU* 
OR = Operating Room 
† Limited intra-operative CT scan of the brain will be performed shortly after bilateral infusion catheter placement and mid-way through the infusion. At the discretion of the 
surgeon, infusions will be stopped if there is evidence of bleeding or injury, or an emergent adverse event 
†† For infusions within the OR, additional intra-operative CT scans of the brain may be performed 
* PICU infusion is at the discretion of neurosurgeon and based on safety results of prior treated participants’ outcomes. If the surgeon elects to perform the infusion within the 
PICU, a single limited intra-operative CT scan of the brain will be performed shortly after bilateral infusion catheter placement and the participant will then be transferred 

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To achieve the broadest distribution of vector and transgene expression, the goal of the BiTh 
infusion is to fill as much of the thalamus as possible using a dosing scheme that holds the vector 
concentration constant (based on a titer of 3.26E+13 vg/mL) and to progressively increase the 
volume of infusion across consecutive participants. As infusion volume increases, so does the 
total vector dose (these dosing parameters are inherently confounded). The amount or % of the 
target thalamus that is filled with vector is based on the use of convection enhanced delivery 
(CED) to drive AAV through the brain parenchyma using pressure (Bobo et al. 1994). Infusion 
rates between 1 and 5 µL/min are typically used with CED and this technique has been 
successfully applied across many nonclinical and clinical studies to increase the distribution of a 
wide range of therapeutic agents including AAV (Ellinwood et al. 2011, Tardieu et al. 2017, 
Chien et al. 2017, Christine et al. 2019, Hudry et al. 2019, Kells et al. 2009, Yin et al. 2010). For 
delivery of AXO-AAV-GM2, an infusion rate of 4 μL/min will be used across all participants for 
CED of the vector. As shown in Table 11, the time for bilateral infusion will range from 1.5 to 
5.2 hours. 
In order to estimate the volume of distribution (Vd) of vector within the thalamus based on the 
volume of infusion (Vi), a correction factor can be applied for how far the vector spreads from 
the point of source of delivery with CED. From CED studies with delivery of AAV to the 
thalamus (and other brains structures), the Vd is substantially larger than the Vi. The Vd:Vi ratio 
can be conservatively estimated to be a factor of 3, meaning that the distribution of AAV in the 
thalamus will be 3 times the infusion volume (Yin et al. 2010). This is an important factor to help 
ensure that the infusion volume is appropriately sized to yield a distribution of AAV that is 
matched to the size of the target thalamus. The calculated Vd for infantile participants in the 
study ranges from 12% (if Participant 1 is an infantile) of the thalamus to 87% of the thalamus 
for Cohort 2 based on a standard volume of 4,322 mm3 for a 1-year-old child (Table 11). The 
calculated Vd for juvenile participants in the study ranges from 11% (if Participant 1 is a 
juvenile) to 75% for Cohort 2 based on a standard volume of 4,990 mm3 for a 4-year-old child 
(Table 11). 

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Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
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Table 11: 
Study AXO-GM2-001 Stage 1 Calculated Vd for Thalamic Infusion by 
Participant (results shown per thalamus) 
 
 
Group 
 
Participant 
 
Dose 
Volume of 
Infusion 
(mL) 
Calculated Volume of 
Distribution 
(3 x Infusion volume) 
Calculated Percent 
Volume of Target 
Starting Dose 
Participant (I or J) 
5.87E+12 vg 
0.18 
540 mm3 
I: 12% 
J: 11% 
 
Low Dose 
Participant (J) 
 
1.17E+13 vg 
0.36 
1,080 mm3 
22% 
Participant (I) 
0.36 
1,080 mm3 
25% 
Participant (J) 
0.36 
1,080 mm3 
22% 
Cohort 1  
(Mid-Dose) 
Participant (J) 
 
 
2.35E+13 vg 
0.72 
2,160 mm3 
43% 
Participant (I) 
0.72 
2,160 mm3 
50% 
Participant (I) 
0.72 
2,160 mm3 
50% 
Cohort 2 
(High-Dose) 
Participant (I) 
4.08E+13 vg 
1.25 
3,750 mm3 
87% 
Participant (I) 
1.25 
3,750 mm3 
87% 
 
Note: Dosing based on final titer of 3.26E+13 vg/mL (1:1 mixture of AAVrh8-HEXA:AAVrh8-HEXB). Calculated percent 
volume of target based on a standard volume of 4,322 mm3 (1YO) for infantile participants and 4,990 mm3 (4YO) for juvenile 
participants as reported by Tutunji et al. 2018. Vd derived as 3 times the infusion volume divided by the thalamic volume. 
 
 
8.3.4.2. 
AXO-AAV-GM2 ICM/IT Clinical Dose Strategy 
ICM/IT infusion will be conducted the day following BiTh infusion in study AXO-GM2-001 via 
a lumbar puncture and advancement of a flexible catheter (Excelsior SL-10, Stryker) to the 
cisterna magna. Infusion will take place through the catheter, with 75% of the dose into the CSF 
at the level of the cisterna magna. The catheter will then be partially retracted to the 
thoracolumbar spinal cord level and the remaining 25% of dose will be infused into the CSF of 
the intrathecal space. The concentration of AXO-AAV-GM2 will be held constant across the 
dosing levels (3.26E+13 vg/mL), but the infusion volumes (and thus dose) will vary in Stage 1 
(Table 12). Vector will be administered at a rate of 0.5 to 1.0 mL/min. Additional details can be 
found in the Surgical Manual. 

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Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
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Table 12: 
Study AXO-GM2-001 Stage 1 ICM/IT Infusion Volume and Dose by 
Participant 
 
 
 
Cisterna magna level 
(75% of vector) 
Thoracolumbar level 
(25% of vector) 
Total CSF Dose 
 
Group 
 
Participant 
 
Dose (vg) 
Infusion 
Volume 
(mL) 
 
Dose (vg) 
Infusion 
Volume 
(mL) 
 
Dose (vg) 
Infusion 
Volume 
(mL) 
Starting Dose 
Participant (I or 
J) 
9.79E+13 
3.00 
3.26E+13 
1.00 
1.30E+14 
4.00 
 
Low Dose 
Participant (J) 
1.28E+14 
3.94 
4.28E+13 
1.31 
1.71E+14 
5.25 
Participant (I) 
1.28E+14 
3.94 
4.28E+13 
1.31 
1.71E+14 
5.25 
Participant (J) 
1.28E+14 
3.94 
4.28E+13 
1.31 
1.71E+14 
5.25 
Cohort 1 
(Mid Dose) 
Participant (J) 
1.28E+14 
3.94 
4.28E+13 
1.31 
1.71E+14 
5.25 
Participant (I) 
1.28E+14 
3.94 
4.28E+13 
1.31 
1.71E+14 
5.25 
Participant (I) 
1.28E+14 
3.94 
4.28E+13 
1.31 
1.71E+14 
5.25 
Cohort 2    
(High Dose) 
Participant (I) 
2.05E+14 
6.30 
6.85E+13 
2.10 
2.74E+14 
8.40 
Participant (I) 
2.05E+14 
6.30 
6.85E+13 
2.10 
2.74E+14 
8.40 
Note: Dosing based on final titer of 3.26E+13 vg/mL (1:1 mixture of AAVrh8-HEXA:AAVrh8-HEXB) 
 
8.3.4.3. 
AXO-AAV-GM2 Total Vector Dose Summary 
The total dose (vg) of AXO-AAV-GM2 that will be administered per participant ranges from 
1.42E+14 to 3.56E+14 vg (Table 13). Total dose is a combination of bilateral IPa infusion of 
viral vector into the thalamus and direct delivery of vector into the CSF. 
 
Table 13: 
Study AXO-GM2-001 Stage 1 BiTh and ICM/IT Total Vector Dose by 
Participant 
 
 
Participant 
Dose per 
Thalamus 
BiTh Dose 
ICM/IT Dose 
TOTAL DOSE 
Starting Dose 
Participant (I or 
J) 
5.87E+12 vg 
1.17E+13 vg 
1.30E+14 vg 
1.42E+14 vg 
 
Low Dose 
Participant (J) 
1.17E+13 vg 
2.35E+13 vg 
1.71E+14 vg 
1.95E+14 vg 
Participant (I) 
1.17E+13 vg 
2.35E+13 vg 
1.71E+14 vg 
1.95E+14 vg 
Participant (J) 
1.17E+13 vg 
2.35E+13 vg 
1.71E+14 vg 
1.95E+14 vg 
Cohort 1 
(Mid-Dose) 
Participant (J) 
2.35E+13 vg 
4.70E+13 vg 
1.71E+14 vg 
2.18E+14 vg 
Participant (I) 
2.35E+13 vg 
4.70E+13 vg 
1.71E+14 vg 
2.18E+14 vg 
Participant (I) 
2.35E+13 vg 
4.70E+13 vg 
1.71E+14 vg 
2.18E+14 vg 
Cohort 2 
(High-Dose) 
Participant (I) 
4.08E+13 vg 
8.15E+13 vg 
2.74E+14 vg 
3.56E+14 vg 
Participant (I) 
4.08E+13 vg 
8.15E+13 vg 
2.74E+14 vg 
3.56E+14 vg 
Note: Dosing based on final titer of 3.26E+13 vg/mL (1:1 mixture of AAVrh8-HEXA:AAVrh8-HEXB) 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
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8.4. 
Number of Participants 
Stage 1: Twelve (12) participants including juvenile-onset and infantile-onset participants 
Stage 2: Up to ten (10) infantile-onset participants 
LTFU: All participants Stage 1 and 2 
 
8.5. 
Treatment Assignment 
All participants will be assigned to treatment. 
 
8.6. 
Dose Adjustment Criteria 
Stage 1 dose escalation is defined in Section 8.3.4. Stage 2 dose will be based on results of 
Stage 1. Following selection of dose for Stage 2, no dose adjustments will be allowed. 
 
8.7. 
Potential Risks 
The risks of administering AXO-AAV-GM2 treatment in TSD or SD participants are not 
completely known. There are theoretical/potential risks with AXO-AAV-GM2, certain known 
risks associated with BiTh and ICM/IT administration of AXO-AAV-GM2, and there are certain 
known risks associated with the proposed ITI regimen. These risks are described in the 
Investigator’s Brochure. 
8.7.1. 
Potential Risks with AXO-AAV-GM2 
These risks are described in the Investigator’s Brochure. 
 
8.8. 
Criteria for Study Termination 
The study stopping criteria are outlined in Section 9.4. In the event of a stopping criteria event, 
the DSMC and Sponsor will be notified for determination of significant safety risks (as outlined 
in the DSMC Charter). 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 7.0, 09 June 2022 
AXO-AAV-GM2
Confidential
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Table 14: 
Schedule of Juvenile-Onset Participant Assessments 
 
Schedule of Activities
Visit
A 
Visit
B 
Visit
C 
Visit
D 
Visit
1a 
Visit
1b 
Visit
2 
Visit
3 
Visit
4 
Visit
5 
Visit
6 
Visit
7 
Visit
8 
Visit
9 
Visit
10 
Visit
11 
Visit
12 
Visit
13 
Visit
14 
Visit
15 
Week
- 8 
Day
-16 
Day
-7 
Day
-2 
Day
1 
Day
2 
Day
8 
Day
15 
Day
22 
Week
4 
Week
6 
Week
8 
Week
10 
Week
12 
Week
16 
Week
20 
Week
24 
Week
48 
Week
72 
Week
96 
±28d
±5d
±3d
±1d
-
-
±1d
±3d
±3d
±3d
±4d
±5d
±4d
±7d
±7d
±7d
±7d
±7d
±7d
±7d
ICF 
X* 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Inclusion/Exclusion Criteria 
X* 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Genetic Confirmation 1 
X* 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Vital Signs 2 
X* 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27 
 X27 
 X27 
Weight 
X* 
X 
X 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27
 X27 
 X27 
Height 
X* 
X 
X 
 
 
 
 
 
 
 
 
 
 
X 
 
 
X 
X27
X27 
 X27 
Physical Examination 
X* 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27
 X27 
 X27 
Neurologic Examination 3 
 
X* 
 
 
X 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27 
 
 X27 
 X27 
   Tele-health follow-up call 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
X 
X 
 
X28 
X28 
X28 
Tele-health Neuro Exam 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
X28 
X28 
X28 
Ophthalmology Exam 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Urinalysis 
 
 
 
 
X 
 
 
 
 
 
 
 
 
AN 
 
 
AN 
AN 
AN 
AN 
Participant Appropriate 
Neuro-Cognitive 
Assessments22 
X* 
 
 
 
 
 
 
 
 
X 
 
 
 
X 
 
 
X 
X27 
X27 
X27 
Clinical Global Impression23 
X* 
 
 
 
 
 
 
 
 
X 
 
 
 
X 
 
 
X 
X 
X 
X 
Motor Assessments24 
X 
 
 
 
 
 
 
 
 
 
 
 
 
X 
 
 
X 
X27 
X27 
X27 
BAER/VER/SSEP26 
X 
 
 
 
 
 
 
 
 
 
 
 
 
X 
 
 
X 
X27 
 
 
CBC with auto-differential4 
X 
 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27
X27
 X27
Comprehensive metabolic 
panel 4 
X 
 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27 
X27 
X27 
CRP 
X 
 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27 
X27 
X27 
GGT – AN due to elevated       
liver enzymes 
AN 
 
 
 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
 
 
AN 
AN 
AN 
AN 
PT, PTT, INR, Blood 
Typing4 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
CD 19, 20 count 
 
X 
X 
X 
 
AN 
 
 
 
X 
 
X 
 
X 
 
 
X 
X27
AN 
AN 
IgA level 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
IgG levels 6 
 
 
 
X 
 
 
 
 
 
X 
 
X 
 
X 
 
 
X 
AN 
AN 
AN 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Table 14:
Schedule of Juvenile-Onset Participant Assessments (Continued)
Confidential
Page 55 of 97
 
 
 
Schedule of Activities 
Visit A 
Visit B Visit C
Visit
D
Visit 1a Visit 1b Visit
2
Visit 3
Visit
4
Visit
5
Visit 6
Visit 7
Visit 8
Visit 9
Visit 10 
Visit 11 
Visit 12
Visit
13
Visit
14
Visit
15
 
Week
- 8 
Day
-16 
Day
-7 
Day
-2 
Day 1 
Day 2 
Day
8 
Day 15
Day
22 
Week
4 
Week 6
Week 8
Week 10
Week 12 Week 16
Week 20
Week 24
Week
48 
Week
72 
Week
96 
 
±28d 
±5d
±3d 
±1d
- 
- 
±1d
±3d 
±3d
±3d
±4d
±5d
±4d
±7d
±7d 
±7d 
±7d
±7d
±7d
±7d
Total hemolytic complement 
(CH50) – AN due to platelet 
count decrease4
X 
 
 
 
AN 
AN 
AN 
AN 
AN
AN 
AN 
AN 
AN 
AN 
 
 
AN 
AN
AN 
AN
Infectious disease testing –
As clinically indicated based 
on Medical History5 
 
AN 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Research blood collection 7 
 
X 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27 
X27
X27
Anti-AAVrh8 antibodies 
(ADA)7 
 
X 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27 
X27 
X27 
Transgene antibodies 
(ADA)7 
 
X 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27 
X27 
X27 
Neutralizing antibodies 
(Nabs)7 
 
X 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27 
X27 
X27 
GM2 ganglioside levels 
(serum)7 
 
X 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X27 
X27 
X27 
ELISpot 
 
X 
 
AN
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
 X27 
X27 
X27 
Chest X-ray 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Swallow Study25 
 
X 
 
 
 
 
 
 
 
 
 
 
 
X 
 
 
X 
X27
 
X27 
ECG 
 
X 
 
 
AN 
 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
X 
 
 
AN 
 X27 
AN 
X27 
EEG 8 
 
X 
 
 
 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
Echocardiogram 9 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Pre-Surgical MRI 10 / CT 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Intra-surgical CT scan 
 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Post-Surgical MRI 
 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
MRI, MRS, DTI 11 
X 
 
 
 
 
 
 
 
 
 
 
 
 
X 
 
 
X 
X27
X27 
 
Surgical readiness 
determination 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Central Venous Catheter 
placement 12 
 
AN 
AN 
AN 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Rituximab infusion 13 
 
 
X 
AN 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Solu-Medrol infusion 14 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Sirolimus 15 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
wean 
 
 
 
Prednisolone 16 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X, 
taper 
X, 
taper 
 
 
 
 
 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Table 14:
Schedule of Juvenile-Onset Participant Assessments (Continued)
Confidential
Page 56 of 97
 
 
 
Schedule of Activities 
Visit A
Visit B Visit C Visit D Visit 1a Visit 1b Visit 2
Visit 3
Visit 4
Visit 5
Visit 6
Visit 7
Visit 8
Visit 9
Visit 10
Visit 11
Visit 12
Visit 13
Visit 14
Visit 15
 
Week
- 8
Day
-16
Day
-7
Day
-2
Day 1
Day 2
Day 8
Day 15
Day 22
Week 4
Week 6
Week 8
Week 10
Week 12
Week 16
Week 20
Week 24
Week 48
Week 72
Week 96
 
±28d
±5d
±3d
±1d
-
-
±1d
±3d
±3d
±3d
±4d
±5d
±4d
±7d
±7d
±7d
±7d
±7d
±7d
±7d
Trimethoprim/sulfamethoxaz 
ole 17
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
 
Lansoprazole 18 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
 
 
 
 
IVIG administration 19 
 
 
 
 
 
AN 
 
 
 
AN 
AN 
AN 
AN 
AN 
 
 
AN 
 
 
 
Bilat Intrathalamic Infusion 
 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Intrathecal Infusion 
 
 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
LP CSF collection 20 
X 
 
 
 
 
X 
 
 
 
 
 
 
 
X 
 
 
X 
X27 
 X27 
X27 
CSF HexA activity level, 
GM2 ganglioside 
X 
 
 
 
 
X 
 
 
 
 
 
 
 
X 
 
 
X 
 X27 
X27 
X27 
Sirolimus levels 
 
 
AN 
X 
X 
AN 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
AN 
 
 
 
Anti-seizure drug levels 21 
 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
Adverse Events review 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Concomitant medication 
review 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Footnotes:  
* Enrollment of Participants will be done at staggered 4-week intervals, based on satisfactory DSMC and Sponsor review of 4-week safety data. The screening activities marked 
with an asterisk may be performed prior to DSMC data review conclusion. All other assessments must not be performed prior to DSMC/Sponsor review and approval to enroll the 
next participant. 
* Blue Indicates this occurs at Massachusetts General Hospital, Red indicates it occurs at UMass Chan Medical School 
 
1. 
Verification of HEXA or HEXB gene mutation and modifiers by reports 
2. 
Measurements include systolic and diastolic blood pressure, pulse rate per minute, respiratory rate per minute, and temperature 
3. 
Comprehensive exam or limited exam at the discretion of the clinician based on status of the participants. Exams may be videotaped. For Visit 1b (Day 2), perform 
neurologic checks every 2h for the first 24h, and full physical and neurological exam 24h, 48h, and 72h post infusion. 
4. 
Safety labs will be prioritized based on the participant’s conditions at the discretion of the investigator. Additional safety labs may be required for participant 
management. Safety labs include the following: CBC with auto-differential and comprehensive metabolic panel, AST, ALT, ALP repeated as needed if 2X baseline, 
ELISpot. A CH50 may also be performed as clinically indicated, i.e., platelet count decrease. Additionally, PT, PTT, and INR will be assessed prior to surgery. 
5. 
Infectious disease testing will be performed as clinically indicated (i.e., based on Medical History) and will include HIV, hepatitis A, B and C, herpes simplex virus, 
cytomegalovirus, Epstein Barr virus, varicella zoster virus, and toxoplasmosis 
6. 
IgG levels to be done at least 3 days prior to the scheduled visit, at a local lab as necessary. Performed as needed at month 6, contingent on results from month 3 
7. 
Blood will be collected for research as tolerated by the participant and will be frozen for later use or used for the isolation of serum or PBMCs. The amount of research 
blood collected, and its intended use, will vary between visits based on the overall volume of blood collected within a 1-week period remaining < 10 mL. Sample 
prioritization will be determined by investigator and Sponsor if collected blood volume is limited. Collect blood on Visit B (Day -16) prior to immunosuppression. Blood 
collected for research can include anti-AAVrh8 antibodies (ADA), transgene antibodies (ADA) and neutralizing antibodies (Nabs) if needed. The priority should be the 
antibodies followed by the serum HEXA activity and then GM2 ganglioside levels in serum. 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Table 14:
Schedule of Juvenile-Onset Participant Assessments (Continued)
Confidential
Page 57 of 97
 
 
8. 
1hr or 24hr EEG at the discretion of the clinician based on participant status 
9. 
Echocardiogram report within 3 months of screening is acceptable 
10. To be used by neurosurgeon for thalamic target navigation planning. Scan should include brain and spinal cord. Scans may be obtained up to 14 days prior to surgery to 
allow adequate planning and preparation time. 
11. To be reviewed by study neurosurgeon as part of surgical readiness determination. 
12. Caregivers will have option to have a central venous catheter inserted into participants prior to surgical gene transfer to ensure venous access and reduce difficulty and 
pain associate with blood draws during the study 
13. Rituximab IV infusion at 375 mg/m2 body surface area (BSA). As needed at Day -2 for persistent CD20 count greater than or equal to 5% 
14. Solu-Medrol IV infusion at 10 mg/kg 
15. Sirolimus oral at 1.5 mg/m2 BSA; Adjust dose to achieve serum trough levels of 7-12 ng/mL as needed. To be weaned starting Visit 12/Week 24 according to the following 
regimen: Week 24-25: reduce dose by 50%; Week 25-26: reduce Week 24-25 dose by 50%; Week 26-27: reduce Week 25-26 dose by 50% then stop 
16. Prednisolone 1-2 mg/kg/day, to be tapered starting Visit 9/Week 12 according to the following regimen: Week 12-13: reduce dose by 50%; Week 13-14: reduce week 12-13 dose 
by 50%; Week 14-15: reduce week 13-14 dose by 50%; Week 15-16: reduce week 13-14 dose by 50% then stop. 
17. The dose of trimethoprim/sulfamethoxazole should be 2.5 mg/kg/day BID on 2 consecutive days per week (PO or by feeding tube) or per PI discretion, to be 
discontinued following completion of sirolimus wean. 
18. Lansoprazole suspension of 1 to 1.5 mg/kg/day PO, to be discontinued following completion of prednisolone tapering. 
19. IVIG administration 1 gm/kg (1000 mg/kg) if IgG levels < 500 mL/dL. Dose adjusted to maintain serum trough levels of 500-1000 mg/dL after vector infusion. On Day 
1, IVIG administration will occur later in the day, after treatment infusion has completed. 
20. Divided between clinical and research analyses. Visit 1b (Day -2) CSF collection should be pre-administration. 
21. Anti-seizure drug levels will be assessed as needed after Day -2 
22. Appropriate neuro-cognitive assessments will be determined for each participant. We expect all participants will be assessed via the Vineland 3. Available additional 
juvenile assessments include the Wechsler, WPPSI, BSID-III depending on the participant’s age and capabilities. 
23. CGI-S will be administered at Visit A. CGI-I will be administered at Visits 5, 9, 12, 13, 14, and 15. All neuro-cognitive assessments with the exception of the Vineland 3 
should be videotaped. 
24. Juvenile motor assessments and motor classifications include the GMFM-88, GMFC-MLD, 9 Hole Peg Test, Timed Motor Function Tests (10 Meter Walk/Run, Time to 
Rise From Floor, Time Up 4 Stairs), MACs. All motor assessments with the exception of the MACs should be videotaped. 
25. Participants must have a swallow evaluation test performed within 6 months prior to AXO-AAV-GM2 administration to assess the risk of aspiration. If aspiration risk is 
identified, it must be clinically managed prior to surgical procedures. Participants must have a swallow evaluation test performed at baseline and a clinical assessment of 
swallowing and a swallow study, if warranted, at Visit 9 (Week 12), Visit 12 (Week 24), Visit 13 (Week 48), Visit 15 (Week 96) and yearly thereafter for Years 3-5 (see 
Table 16). 
26. BAER/VER/SSEP should be conducted without sedation or a prolongation of, or another episode of general anesthesia. 
27. May be completed if visit occurs in person however not if the visit is completed as a tele-health 
28. Tele-health will occur if Pt does not come to site in person 
 
AN – As Needed 
 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Confidential
Page 58 of 97
 
 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Confidential
Page 59 of 97
 
 
Table 15: 
Schedule of Infantile-Onset Participant Assessments 
 
Schedule of Activities 
Visit 
A 
Visit 
B 
Visit 
C 
Visit 
D 
Visit 
1a 
Visit 
1b 
Visit 
2 
Visit 
3 
Visit 
4 
Visit 
5 
Visit 
6 
Visit 
7 
Visit 
8 
Visit 
9 
Visit 
10 
Visit 
11 
Visit 
12 
Visit 
13 
Week
- 8 
Day
-16 
Day
-7 
Day
-2 
Day 
1 
Day 
2 
Day 
8 
Day 
15 
Day 
22 
Week 
4 
Week 
6 
Week 
8 
Week 
10 
Week 
12 
Week 
16 
Week 
20 
Week 
24 
Week 
48 
±28d 
±5d 
±3d 
±1d 
- 
- 
±1d 
±3d 
±3d 
±3d 
±4d 
±5d 
±4d 
±7d 
±7d 
±7d 
±7d 
±7d 
ICF 
X* 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Inclusion/Exclusion Criteria 
X* 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Genetic Confirmation 1 
X* 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Vital Signs 11 
X* 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
Weight 
X* 
X 
X 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
Height 
X* 
X 
X 
 
 
 
 
 
 
 
 
 
 
X 
 
 
X 
X23 
Physical Examination 
X* 
X 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
Neurologic Examination12 
X* 
 
 
X 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
Tele-health follow-up 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
X 
X 
 
X24 
Tele-health Neuro Exam 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
X24 
Ophthalmology Exam 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
HINE-2 
X* 
 
 
 
 
 
 
 
 
X 
 
 
 
X 
 
 
X 
X23 
BSID-III 
X* 
 
 
 
 
 
 
 
 
X 
 
 
 
X 
 
 
X 
X23 
Clinical Global Impression 
X* 
 
 
 
 
 
 
 
 
X 
 
 
 
X 
 
 
X 
 X 
CBC with auto-differential6 
X 
 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23  
Comprehensive metabolic 
panel6 
X 
 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
hsCRP 
X 
 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
GGT – AN due to elevated     
liver enzymes
AN 
 
 
 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
 
 
AN 
AN 
PT, PTT, INR, Blood 
Typing6 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Total hemolytic 
complement (CH50) – AN 
due to platelet count 
decrease6 
AN 
 
 
 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
 
 
AN 
AN 
Serum HexA activity level 
X 
 
 
 
 
X 
 
 
X 
X 
 
X 
 
X 
 
 
X 
X23 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Table 15:
Schedule of Infantile-Onset Participant Assessments (Continued)
Confidential
Page 60 of 97
 
 
 
 
Schedule of Activities 
Visit 
A 
Visit 
B 
Visit 
C 
Visit 
D 
Visit 
1a 
Visit 
1b 
Visit 
2 
Visit 
3 
Visit 
4 
Visit 5 
Visit 6 
Visit 7 
Visit 8 
Visit 9 
Visit 
10 
Visit 
11 
Visit 
12 
Visit 
13 
 
Week 
- 8 
Day 
-16 
Day 
-7 
Day 
-2 
Day 
1 
Day 
2 
Day 
8 
Day 
15 
Day 
22 
Week 
4 
Week 
6 
Week 
8 
Week 
10 
Week 
12 
Week 
16 
Week 
20 
Week 
24 
Week 
48 
 
±28d 
±5d 
±3d 
±1d 
- 
- 
±1d 
±3d 
±3d 
±3d 
±4d 
±5d 
±4d 
±7d 
±7d 
±7d 
±7d 
±7d 
Sirolimus levels 
 
 
AN 
X 
X 
AN 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
AN 
 
Anti-seizure drug levels 7 
 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
CD 19, 20 count 
 
X 
X 
X 
 
AN 
 
 
 
X 
 
X 
 
X 
 
 
AN 
AN 
IgA level 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
IgG levels 8 
 
 
 
X 
 
 
 
 
 
X 
 
X 
 
X 
 
 
AN 
AN 
Research blood collection 9 
 
X 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
Anti-AAVrh8 antibodies 
(ADA)9 
 
X 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
Transgene antibodies 
(ADA)9 
 
X 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
Neutralizing antibodies 
(Nabs)9 
 
X 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
GM2 ganglioside levels 
(serum)9 
 
X 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
ELISpot 
 
X 
 
AN 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
X 
X23 
Infectious disease testing 10 
– As clinically indicated 
based on Medical History 
 
AN 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Urinalysis 
 
 
 
 
X 
 
 
 
 
 
 
 
 
AN 
 
 
AN 
AN 
Chest X-ray 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Swallow Study22 
 
X 
 
 
 
 
 
 
 
 
 
 
 
X 
 
 
X 
X23 
ECG 
 
X 
 
 
AN 
 
AN 
AN
AN 
AN 
AN 
AN 
AN 
X 
 
 
AN 
X23 
EEG 2 
 
X 
 
 
 
 
 
 
X 
 
 
 
 
 
 
 
 
 
Echocardiogram 3 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Pre-Surgical MRI /CT 4 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Intra-surgical CT 
 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Table 15:
Schedule of Infantile-Onset Participant Assessments (Continued)
Confidential
Page 61 of 97
 
 
 
Schedule of Activities 
Visit 
A 
Visit 
B 
Visit 
C 
Visit 
D 
Visit 
1a 
Visit 
1b 
Visit 
2 
Visit 
3 
Visit 
4 
Visit 5 
Visit 6 
Visit 7 
Visit 8 
Visit 9 
Visit 
10 
Visit 
11 
Visit 
12 
Visit 
13 
 
Week 
- 8 
Day 
-16 
Day 
-7 
Day 
-2 
Day 
1 
Day 
2 
Day 
8 
Day 
15 
Day 
22 
Week 
4 
Week 
6 
Week 
8 
Week 
10 
Week 
12 
Week 
16 
Week 
20 
Week 
24 
Week 
48 
 
±28d 
±5d 
±3d 
±1d 
- 
- 
±1d 
±3d 
±3d 
±3d 
±4d 
±5d 
±4d 
±7d 
±7d 
±7d 
±7d 
±7d 
Post-Surgical MRI 
 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
MRI, MRS, DTI 5 
X 
 
 
 
 
 
 
 
 
 
 
 
 
X 
 
 
X 
X23 
Surgical readiness 
determination
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Central Venous Catheter 
placement 13 
 
AN 
AN 
AN 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Rituximab infusion 14 
 
 
X 
AN 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Solu-Medrol infusion 15 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Sirolimus 16 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
wean 
 
Prednisolone 17 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X, 
taper 
X, 
taper 
 
 
 
Trimethoprim/sulfamethoxa 
zole 18 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
Lansoprazole 19 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
 
 
IVIG administration 20 
 
 
 
 
 
AN 
 
 
 
AN 
AN 
AN 
AN 
AN 
 
 
AN 
 
Bilat Intrathalamic Infusion 
 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
Intrathecal Infusion 
 
 
 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
LP CSF collection 21 
X 
 
 
 
 
X 
 
 
 
 
 
 
 
X 
 
 
X 
X23 
CSF HexA activity level, 
GM2 ganglioside 
X 
 
 
 
 
X 
 
 
 
 
 
 
 
X 
 
 
X 
X23 
Adverse Events review 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Concomitant medication 
review 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Footnotes: 
* Enrollment of Participants will be done at staggered 4-week intervals, based on satisfactory DSMC and Sponsor review of 4-week safety data. The screening activities marked 
with an asterisk may be performed prior to DSMC data review conclusion of prior participants. All other assessments must not be performed prior to DSMC/Sponsor review and 
approval to enroll the next participant. 
* Blue Indicates this occurs at Massachusetts General Hospital, Red indicates it occurs at UMass Chan Medical School 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Confidential
Page 62 of 97
 
 
 
1. 
Verification of HEXA or HEXB gene mutation and modifiers by reports 
2. 
1hr or 24hr EEG at the discretion of the clinician based on the status of the participants 
3. 
Echocardiogram report within 3 months of screening is acceptable. 
4. 
To be used by neurosurgeon for thalamic target navigation planning. Scan should include brain and spinal cord. Scan may be obtained up to 14 days prior to surgery to allow for 
adequate time for planning and preparation. 
5. 
To be reviewed by study neurosurgeon as part of surgical readiness determination. 
6. 
Safety labs will be prioritized based on the participant’s condition at the discretion of the investigator. Additional safety labs may be required for participant 
management. Safety labs include the following: CBC with auto-differential and comprehensive metabolic panel, AST, ALT, ALP repeated as needed if 2X baseline, 
ELISpot. A CH50 may also be performed as clinically indicated, i.e., platelet count decrease. Additionally, PT, PTT, and INR will be assessed prior to surgery. 
7. 
Will be assessed as needed after Day -2 
8. 
IgG levels to be done at least 3 days prior to the scheduled visit, at a local lab as necessary. Performed as needed at month 6, contingent on results from month 3 
9. 
Blood will be collected for research as tolerated by the participant and will be frozen for later use or used for the isolation of serum or PBMCs. The amount of research 
blood collected, and its intended use, will vary between visits based on the overall volume of blood collected within a 1-week period remaining < 10 mL. Sample 
prioritization will be determined by investigator and Sponsor if collected blood volume is limited. Collect blood on Visit B (Day -16) prior to immunosuppression.. 
Blood collected for research can include anti-AAVrh8 antibodies (ADA), transgene antibodies (ADA) and neutralizing antibodies (Nabs) if needed. The priority should 
be the antibodies followed by the serum HEXA activity and then GM2 ganglioside levels in serum. 
10. Infectious disease testing will be performed as clinically indicated (i.e., based on Medical History) and will include HIV, hepatitis A, B and C, herpes simplex virus, 
cytomegalovirus, Epstein Barr virus, varicella zoster virus, and toxoplasmosis 
11. Measurements include systolic and diastolic blood pressure, pulse rate per minute, respiratory rate per minute, and temperature 
12. Comprehensive exam or limited exam at the discretion of the clinician based on participant’s status. Exams may be videotaped. For Visit 1b (Day 2), perform neurologic 
checks every 2h for the first 24h, and full physical and neurological exam 24h, 48h, and 72h post infusion while inpatient. 
13. Caregivers will have option to have central venous catheter inserted into participants prior to surgical gene transfer to ensure venous access and reduce difficulty and pain 
associate with blood draws during the study 
14. Rituximab IV infusion at 375 mg/m2 body surface area (BSA). As needed at Day -2 for persistent CD20 count greater than or equal to 5% 
15. Solu-Medrol IV infusion at 10 mg/kg 
16. Sirolimus oral at 1.5 mg/m2 BSA; Adjust dose to achieve serum trough levels of 7-12 ng/mL as needed. To be weaned starting Visit 12/Week 24 according to the 
following regimen: Week 24-25: reduce dose by 50%; Week 25-26: reduce Week 24-25 dose by 50%; Week 26-27: reduce Week 25-26 dose by 50% then stop 
17. Prednisolone 1-2 mg/kg/day, to be tapered starting Visit 9/Week 12 according to the following regimen: Week 12-13: reduce dose by 50%; Week 13-14: reduce 
week 12-13 dose by 50%; Week 14-15: reduce week 13-14 dose by 50%; Week 15-16: reduce week 13-14 dose by 50% then stop. 
18. The dose of trimethoprim/sulfamethoxazole 2.5 mg/kg/day BID on 2 consecutive days per week (PO or by feeding tube) or per PI discretion, to be discontinued 
following completion of sirolimus wean. 
19. Lansoprazole suspension of 1 to 1.5 mg/kg/day PO, to be discontinued following completion of prednisolone tapering. 
20. IVIG administration 1 gm/kg (1000 mg/kg) if IgG levels < 500 mL/dL. Dose adjusted to maintain serum trough levels of 500-1000 mg/dL after vector infusion. On Day 
1, IVIG administration will occur later in the day, after treatment infusion has completed. 
21. Divided between clinical and research analyses. Visit 1b (Day -2) CSF collection should be pre-administration. 
22. Participants must have a swallow evaluation test performed within 6 months prior to AXO-AAV-GM2 administration to assess risk of aspiration. If aspiration risk is 
identified, it must be clinically managed prior to surgical procedures. Participants must have a swallow evaluation test performed at baseline and a clinical assessment of 
swallowing and a swallow study, if warranted, at Visit 9 (Week 12), Visit 12 (Week 24), Visit 13 (Week 48), and yearly thereafter for Years 2-5 (see Table 17). 
23. May be completed if visit occurs in person however not if the visit is completed as a tele-health 
24. Tele-health will occur if Pt does not come to site in person 
 
AN – As Needed 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Confidential
Page 63 of 97
 
 
Table 16: 
Schedule of Juvenile-Onset Participant LTFU 
 
Schedule of Activities 
Visit 16 
Visit 17 
Visit 18 
Visit 19 
Visit 20 
Week 120 
Week 144 
Week 168 
Week 192 
Week 240 
±28d 
±28d 
±28d 
±28d 
±28d 
Vital Signs 
X1 
X1 
X1 
X1 
X1 
Weight 
X1 
X1 
X1 
X1 
X1 
Height 
X1 
X1 
X1 
X1 
X1 
Physical Examination 
X1 
X1 
X1 
X1 
X1 
Neurologic Examination (may be videotaped) 
X1 
X1 
X1 
X1 
X1 
  Tele-health follow-up 
X2 
X2 
X2 
X2 
X2 
Participant Appropriate Neuro-Cognitive Assessments 
 
X1 
 
X1 
X1 
Clinical Global Impression 
 
X1 
 
X1 
X1 
Motor Assessments 
 
X1 
 
X1 
X1 
BAER/VER/SSEP 
 
X1 
 
 
 
MRI, MRS, DTI 
 
X1 
 
X1 
X1 
CBC with auto-differential 
X1 
X1 
X1 
X1 
X1 
Comprehensive metabolic profile 
X1 
X1 
X1 
X1 
X1 
CH50 – AN due to platelet count decrease 
AN 
AN 
AN 
AN 
AN 
CSF HexA activity level, GM2 ganglioside 
 
X1 
 
X1 
X1 
CD 19, 20 count 
AN 
AN 
AN 
AN 
AN 
IgG levels 
AN 
AN 
AN 
AN 
AN 
Research blood collection 
X1 
X1 
X1 
X1 
X1 
Anti-AAVrh8 antibodies (ADA) 
X1 
X1 
X1 
X1 
X1 
Transgene antibodies (ADA) 
X1 
X1 
X1 
X1 
X1 
Neutralizing antibodies (Nabs) 
X1 
X1 
X1 
X1 
X1 
Serum HexA activity levels 
X1 
X1 
X1 
X1 
X1 
Serum GM2 ganglioside levels 
X1 
X1 
X1 
X1 
X1 
ELISpot 
X1 
X1 
X1 
X1 
X1 
Swallow Study 
 
X1 
 
X1 
X1 
Adverse Events review 
X 
X 
X 
X 
X 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Confidential
Page 64 of 97
 
 
Table 16: 
Schedule of Juvenile-Onset Participant LTFU (Continued) 
 
Schedule of Activities 
Visit 16 
Visit 17 
Visit 18 
Visit 19 
Visit 20 
 
Week 120 
Week 144 
Week 168 
Week 192 
Week 240 
 
±28d 
±28d 
±28d 
±28d 
±28d 
Concomitant medication review 
X 
X 
X 
X 
X 
Urinalysis 
 
AN 
 
AN 
AN 
AN – As Needed 
1. 
May be completed if visit occurs in person however not if the visit is completed as a tele-health 
2. 
Tele-health will occur if Pt does not come to site in person 
 
 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Confidential
Page 65 of 97
 
 
 
Table 17: 
Schedule of Infantile-Onset Participant LTFU 
 
Schedule of Activities 
Visit 14 
Visit 15 
Visit 16 
Visit 17 
Visit 18 
Visit 19 
Visit 20 
Week 72 
Week 96 
Week 120 
Week 144 
Week 168 
Week 192 
Week 240 
±28d 
±28d 
±28d 
±28d 
±28d 
±28d 
±28d 
Vital Signs 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Weight 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Height 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Physical Examination 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Neurologic Examination 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
  Tele-health Follow-up 
X2 
X2 
X2 
X2 
X2 
X2 
X2 
HINE-2 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
BSID-III 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Vineland 3 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
MRI, MRS, DTI 
 
X1 
 
X1 
 
 
X1 
BAER/VER/SSEP 
 
 
 
X1 
 
 
 
Clinical Global Impression 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
CBC with auto-differential 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Comprehensive metabolic panel 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
CH50 – AN due to platelet count decrease 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
CSF HexA activity level, GM2 ganglioside 
 
X1 
 
X1 
 
X1 
X1 
CD 19, 20 count 
AN 
AN 
AN 
AN 
AN 
AN 
AN 
IgG levels 
X1 
X1 
X1 
X1 
X1 
X1 
X1 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Confidential
Page 66 of 97
 
 
Table 17: 
Schedule of Infantile-Onset Participant LTFU (Continued) 
 
Schedule of Activities 
Visit 14 
Visit 15 
Visit 16 
Visit 17 
Visit 18 
Visit 19 
Visit 20 
 
Week 72 
Week 96 
Week 120 
Week 144 
Week 168 
Week 192 
Week 240 
 
±28d 
±28d 
±28d 
±28d 
±28d 
±28d 
±28d 
Research blood collection 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Anti-AAVrh8 antibodies (ADA) 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Transgene antibodies (ADA) 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Neutralizing antibodies (Nabs) 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Serum HexA activity level 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Serum GM2 ganglioside level 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
ELISpot 
X1 
X1 
X1 
X1 
X1 
X1 
X1 
Swallow Study 
 
X1 
 
X1 
 
X1 
X1 
Adverse Events review 
X 
X 
X 
X 
X 
X 
X 
Concomitant medication review 
X 
X 
X 
X 
X 
X 
X 
Urinalysis 
AN 
AN 
 
AN 
 
AN 
AN 
AN – As Needed. 
 
1. 
May be completed if visit occurs in person however not if the visit is completed as a tele-health 
2. 
Tele-health will occur if Pt does not come to site in person 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Confidential
Page 67 of 97
 
 
 
9. 
SELECTION AND WITHDRAWAL OF PARTICIPANTS 
In order to reduce participant burden and aid in the participant selection process, screening may 
be initiated by a virtual visit with the study staff prior to traveling to the study site. During the 
virtual visit, study staff will conduct a preliminary assessment of participant eligibility. The 
parent(s)/caregiver(s) will be asked about the participant’s medical history and may be asked to 
help in demonstrating the participant’s functional ability. This virtual visit may be video 
recorded. 
 
9.1. 
Participant Inclusion Criteria 
1. Male or female participants with genetically diagnosed TSD or SD mutations of either HEXA 
gene or HEXB gene 
a. Stage 1 juvenile-onset participants must be ≥ 2 years old and ≤ 12 years old at time of gene 
transfer 
ii. Diagnosis consistent with juvenile-onset TSD or SD 
c. Stage 1 infantile-onset participants must be between ≥ 6 months and ≤ 20 months of age at 
the time of gene transfer 
i. Diagnosis consistent with infantile-onset TSD or SD 
 
2. Juvenile onset participants must demonstrate a minimum of 2 of the following age-appropriate 
clinical features/abilities, confirmed by the site examiner at the time of screening and reaffirmed 
prior to the initiation of immunosuppression: 
a. A Gross Motor Function Classification-MLD (GMFC-MLD) score of 0, 1 or 2. The 
minimum gross motor function (GMFC-MLD level 2) is the ‘ability to walk with support and 
walking without support is not possible (fewer than 5 steps)’. (Participants aged 2-12 years) 
Note: Any form of support is permitted; however, the participant must initiate each step and 
complete it for a total of 5 steps. 
b. Fine Motor Function 
− For Participants aged 4-12 years: A Manual Ability Classification System 
(MACS) score of I, II, III, or IV. The minimum level of manual ability (level IV) 
corresponds to ‘Handles a limited selection of easily managed objects in adapted 
situations’. 
− For participants aged 2-4 years: attainment of fine motor function/coordination 
abilities and milestones with normal or a reduced quality of performance. That is, 
the ability to coordinate fingers and both hands to play, such as swinging a bat or 
opening a container (pathways.org) OR the ability to use fingertips to pick up 
small objects, i.e., the child uses pad of his/her thumb and any fingertip to grasp a 
pellet or small object as described in BSID III Fine Motor Sub-test Item #26. . 
c. Speech: 
− For participants aged 4-12 years, a speech disturbance score of 0, 1, 2 or 3 on the 
speech disturbance subset of the Scale for Assessment and Rating of Ataxia 

UMass Chan Medical School 
Clinical Study Protocol: AXO-GM2-001 
Version 8.0, 09 June 2023 
AXO-AAV-GM2
Confidential
Page 68 of 97
 
 
(SARA). The minimum speech requirement is a speech disturbance in which most 
words can be understood, with occasional words difficult to understand secondary 
to dysarthria. 
− Participants aged 2-4 years who have attained the communication milestone of 
ability to consistently use 2-3 word phrases may be assessed in line with this 
criterion using the speech disturbance subset of the SARA. 
− For participants aged 2-4 years who have not yet attained the above 
communication milestone, the minimum requirement is the ability to imitate at 
least one word, even if the imitation consists of vowels only (BSID III, expressive 
communication subtest, item #16) 
3. Infantile onset participants must demonstrate current* or historical† ability to sit without support 
for at least 5 seconds 
* As assessed in item 22 of the BSID-III Gross Motor Scale or documented medical records 
† Documented within available medical records 
In addition, infantile onset participants must demonstrate a minimum of 3 of the following 
developmental skills confirmed by the site examiner at the time of screening and reaffirmed prior 
to the initiation of immunosuppression: 
a. Head control - While supine, with head in midline turns head symmetrically (score of 3 on 
GMFM item 1) 
b. Uses hands to support self while sitting 
c. Reach for an object that is held out for them above their chest while supine 
d. Transfer of object from hand to hand while supine 
e. Eye tracking while supine 
f. 
Looks at an object of interest for at least 3 continuous seconds 
4. Surgical readiness for gene transfer route of administration confirmed by the study 
neurosurgeon, based on examination and MRI findings 
The following findings will disallow the performance of the BiTh procedure, thereby 
excluding the participant from participation: 
• Any scalp and skull related lesion (e.g. vascular, infectious) over the surgical 
entry area 
• Any intracranial lesion (e.g. vascular, cystic, other mass lesions), significant 
immaturity, or deformity of the brain anatomy that would make the intended 
surgical trajectory high risk 
The following findings will disallow the performance of the ICM/IT procedure, thereby 
excluding the participant from participation: 
• Any skin related lesion (e.g. vascular, infectious) over the lumbar puncture site 
• Any intraspinal or intracranial lesion in posterior fossa (e.g. vascular, cystic, other 
mass lesions) or significantly deformed, distorted brain, spinal and cisternal 
anatomy that make the intended intrathecal trajectory high risk or not feasible 

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Participants otherwise eligible for study participation but deemed not currently fit for 
neurosurgery may be re-screened at the discretion of the investigator 
5. Participants receiving off-label miglustat and/or Tanganil must be willing to discontinue 
these therapies 30 days prior to the start of screening 
6. Ability to reliably travel to the study sites for study visits according to the Schedule of 
Assessments 
 
9.2. 
Participant Exclusion Criteria 
1. Presence of G269S or W474C mutation in HEXA 
2. Evidence of lower respiratory tract aspiration not easily manageable with thickening of 
feedings or substitution of a modified bottle nipple, as judged on a multi-texture contrast 
swallow. 
3. History of multiple aspiration pneumonias occurring in the past twelve months. 
4. Respiratory support in the form of ventilation (invasive or non-invasive). 
5. History of drug-resistant seizures or status epilepticus 
6. History and/or findings of spinal cord disease that would preclude the LP and ICM/IT 
infusion procedures including: 
• Infectious process involving the spinal canal which may cause adhesions or 
septations in the spinal and/or subarachnoid space 
• Previous spinal surgeries 
• History of trauma, bleeding in the spinal canal 
• Vascular or cystic lesions, or any other mass lesion 
• Congenital deformities and malformations involving the spinal canal 
• Posterior fossa findings (low lying cerebellar tonsils, crowded foramen magnum, 
small or absent cisterna magna) 
7. The participant’s parent(s) or legal guardian(s) is unable to understand the nature, scope, 
and possible consequences of the study, or does not agree to comply with the protocol 
defined schedule of assessments 
8. Any prior participation in a study in which a gene therapy vector or stem cell 
transplantation was administered 
9. Immunizations of any kind in the month prior to screening 
10. Cardiomyopathy or other cardiac disease (based on echocardiogram and/or ECG) that in 
the opinion of the Investigator would deem the participant unsafe to undergo surgical 
gene transfer 
11. Indwelling ferromagnetic devices that would preclude MRI/ /MRS/DTI imaging 
12. Ongoing medical condition that is deemed by the Investigator to interfere with the 
conduct or assessments of the study 

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13. Current clinically significant infections including any requiring systemic treatment 
including but not limited to human immunodeficiency virus (HIV), Hepatitis A, B, or C 
14. History of or current chemotherapy, radiotherapy or other immunosuppressive therapy 
within the past 30 days. corticosteroid treatment may be permitted at the discretion of the 
PI 
15. Clinically significant laboratory abnormalities: 
Based on age-specific reference range and determined by the investigator 
• Total WBC count 
• Hemoglobin 
• Creatinine 
• Pancreatic enzymes 
Based on the following thresholds 
• Platelet count (< 150,000/μL) 
• Prothrombin (PT), partial thromboplastin time (PTT) >2X normal 
• Liver transaminases (Hy’s Law: > 3x elevations above the ULN of ALT or AST and 
serum total bilirubin > 2xULN) 
16. Participants for whom any of the proposed study procedures or medications (i.e. 
sirolimus, trimethoprim/sulfamethoxazole) would be contraindicated 
17. Failure to thrive, defined as falling 20 percentiles (20/100) in body weight in the 3 
months preceding Screening/Baseline 
18. Participant is not suitable for participation in the study in the opinion of the Principal 
Investigator 
9.3. 
Participant Withdrawal Criteria 
Since AXO-AAV-GM2 is a one-time administration, withdrawal of therapy is not possible. 
 
9.4. 
Study Stopping Criteria 
Temporary suspension of enrollment and administration of AXO-AAV-GM2 to study 
participants will result if any of the following occur in the study: 
1. Death of any participant in which the cause of death is assessed by the investigator as at 
least possibly related to the AXO-AAV-GM2 or the neurosurgical administration 
procedure. 
2. Intracranial hemorrhage related to the BiTh procedure or an event suggestive of or 
consistent with craniospinal herniation related to the ICM/IT procedure. 
3. Two or more CTCAE Grade 3 or higher adverse events in any participant that are 
assessed by the investigator as possibly, probably or definitely related to AXO-AAV- 
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4. An SAE in any participant where the event is assessed by the investigator as possibly, 
probably or definitely related to AXO-AAV-GM2 or the neurosurgical administration 
procedure 
The DSMC will review all available safety data for AXO-AAV-GM2 and the neurosurgical 
administration/infusion procedures and will make recommendation(s) regarding further study 
conduct. The DSMC may make a recommendation regarding dose de-escalation/escalation. The 
clinical study may resume after appropriate steps are taken to address these AEs, including 
revision of the clinical protocol. Any participants who have already received IMP and are 
currently in the study at the time study stopping criteria are met will continue to be followed-up, 
for safety and any signs of efficacy, per protocol. 

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10. 
TREATMENT OF PARTICIPANTS 
10.1. 
Description of Study Drug 
Table 18: 
Investigational Product 
 
 
Investigational Product 
Product Names: * 
AXO-AAV-GM2 
Active Ingredients: 
AAVrh8-HEXA 
AAVrh8-HEXB 
Dosage Form: 
Solution (0.5mL vials) 
Solution (0.5mL vials) 
Concentration: ** 
4.32E+13 vg/mL 
2.62E+13 vg/mL 
Combined Vector: 
Each vector is diluted together without the addition of any diluent to yield a final 
titer of 1.63E+13 vg/mL for each, HEXA and for HEXB, and a combined titer of 
3.26E+13 vg/mL 
Formulation: 
1.47mM KH2PO4, 8.06mM 
Na2HPO4-7H2O, pH 7.1 ± 0.1, 
137.93mM NaCl, 2.67mM KCl 
1.47mM KH2PO4, 8.06mM Na2HPO4- 
7H2O, pH 7.1 ± 0.1, 137.93mM NaCl, 
2.67mM KCl 
Route of Administration: 
BiTh and ICM/IT 
BiTh and ICM/IT 
Physical Description: 
The biologic product is a non- 
replicating, serotype rh8, single- 
stranded (ss) recombinant adeno- 
associated virus (rAAV) designated 
rAAVrh8-HEXA 
The biologic product is a non-replicating, 
serotype rh8, single-stranded (ss) 
recombinant adeno-associated virus 
(rAAV) designated rAAVrh8-HEXB 
* Study drug consists of two components, labeled and supplied in two separate vials as AAVrh8-CB-ci-HEXA and 
AAVrh8-CB-ci-HEXB as described in Section 11.1. AXO-AAV-GM2 refers to the combination of these two components into 
a single dose. 
** Concentration is based on ddPCR titers measured for lots produced at Nationwide Children’s Hospital (June 2019) that will be 
used for Stage 1 of the clinical trial. 
 
10.2. 
Concomitant Medications 
All prescription and over the counter medications (including herbal remedies) taken by the 
participant for 28 days prior to administration of immunosuppressive regimen will be recorded 
on the source document and eCRF. Concomitant medications taken by the participants during the 
LTFU period will also be recorded on the source documents/eCRF. The Investigator may 
prescribe additional medications during the study, as long as the prescribed medication is not 
prohibited by the protocol. In the event of an emergency, any required medications may be 
prescribed without prior approval, but the Medical Monitor or designee must be notified of the 
use of any contraindicated medications immediately thereafter. Any concomitant medications 
added or discontinued during the study will be recorded on the eCRF, including the start and end 
dates, as applicable. 
Concurrent supportive care for TSD or SD will not be restricted with exception of exclusionary 
medications. Therapies considered necessary for the participant’s well-being will be 
administered at the discretion of the investigator. 

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10.3. 
Treatment Compliance 
Since AXO-AAV-GM2 is a one-time surgical administration, treatment compliance to gene 
therapy will not be assessed. 
 
10.4. 
Randomization and Blinding 
Stages 1 and 2 of the study have a single-arm, open label design. Randomization or blinding will 
not be performed. 

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11. 
STUDY DRUG MATERIALS AND MANAGEMENT 
11.1. 
Study Drug 
AXO-AAV-GM2 is a 1:1 formulation of two viral vectors, rAAVrh8-HEXA and 
rAAVrh8-HEXB, carrying different human transgenes. One of the vectors contains the human 
HEXA gene, encoding for the HexA α subunit, and the other contains the human HEXB gene, 
encoding for the HexA β subunit. Both vectors utilize a CBA promoter, a chimeric intron, 
BGH/SV40 polyA tail, and AAV serotype 2 inverted terminal repeats (ITR). 
 
11.2. 
Study Drug Packaging and Labeling 
Study drug will be supplied in polypropylene screw top 0.5 mL tubes (vials). Each vial will be 
filled with 0.5 mL of rAAVrh8-HEXA or rAAVrh8-HEXB. The vials are packed and stored in 
plastic cryoboxes. Both the vials and cryoboxes will be labeled in accordance with the 
requirements set by the FDA. The vial labels will each contain a unique identifier for ease of 
tracking. 
11.3. 
Study Drug Storage 
All study drug vials are to be stored in freezers at less than or equal to -60oC. The freezers must 
be monitored daily and any deviation in temperature > -60˚C must be reported to the sponsor as 
soon as possible and prior to further clinical use of the study drug. The study drug must be stored 
in such a way that it cannot be mixed up or confused with any other medications. 
 
11.4. 
Study Drug Preparation 
All prescriptions for study drug are to be written by the site Principal Investigator . A separate 
prescription is needed for the BiTh and the ICM/IT procedures. The prescriptions for these 
procedures must be accompanied by the Dose Preparation Forms. 
Preparation of both the BiTh and ICM/IT doses must be done in accordance with the 
Pharmacy Manual for the study, and all institutional SOPs and practices required for the 
handling of biologic and/or potentially hazardous materials. Preparation of the study drug must 
be performed by the Research Pharmacist or trained designee, who must be listed on the Site 
Delegation Log and be trained on the Pharmacy Manual. Because each full dose of study drug is 
comprised of two components (AAVrh8-HEXA and AAVrh8-HEXB), a second qualified and 
trained member of the study team must be present during the study drug preparation process and 
must verify quantity of each drug component used, and that all processes were followed. This 
person must also be listed on the Site Delegation Log and be trained the Pharmacy Manual. 
 
11.5. 
AXO-AAV-GM2 Administration 
The Surgical Manual will contain detailed specific instructions for administration of 
AXO-AAV-GM2 which will take place over two days beginning with BiTh procedure at Visit 1a 
and ICM/IT procedure at Visit 1b (See Table 14 and Table 15). 

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11.5.1. 
Stage 2 Dosing 
The dose strategy for Stage 2 will be determined by Stage 1 safety and biomarker results. 
 
11.6. 
Study Drug Accountability 
Study drug accountability will be performed routinely by the Sponsor or Sponsor’s 
representative. The site must maintain accurate and current records of all drug received, all drug 
used during the procedures (including back up drug), all drug remaining on site, and all drug 
destroyed if applicable. 
11.7. 
Study Drug Handling and Disposal 
Storage and dispensing of the study medication will be conducted in accordance with the 
Pharmacy Manual and the overview below. 
AXO-AAV-GM2 is a frozen liquid formulation. Study drug must be inspected and inventoried 
upon receipt, and placed into appropriate storage conditions (≤-60°C), in a monitored, 
temperature-controlled freezer located within the hospital pharmacy, in accordance with site 
SOPs and procedures for GMO handling. 
AXO-AAV-GM2 may only be used for the clinical trial for which it is indicated and must not be 
employed for any other clinical or non-clinical use. 

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12. 
ASSESSMENT OF EFFICACY 
Assessment of efficacy within this study will include: 
• CSF HexA activity and GM2 ganglioside level 
• Serum HexA activity 
• BSID-III 
• HINE-2 
• MRI 
• DTI 
• MRS 
• BAER 
• VER 
• Clinical Global Impression 
• Vineland-3 
• Wechsler scale (Wechsler 5, WPPSI, etc) 
• GMFM-88 
• GMFC-MLD 
• 9-Hole Peg Test 
• The Pediatric Balance Scale 
• Timed Motor Function Tests (10 Meter Walk/Run, Time to Rise from Floor, Time Up 
4 Stairs) 
• SSEP 
Please see the Study Schedule of Events (Table 14 and Table 15) for the timing of these 
assessments. 
Several assessments included in this study will be administered by raters trained in the 
administration of the assessment. To minimize variability, it is preferred that the same rater 
administer the same scale to the same participant throughout the study wherever possible, at the 
same time during the clinic visit. 

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13. 
SAFETY PARAMETERS 
13.1. 
Vital Signs, Height, and Weight 
Vital signs will be measured after the participant has been at rest. Measurements will include 
systolic and diastolic blood pressure, pulse rate per minute, respiratory rate per minute, and 
temperature. Height will be measured in centimeters as the length of the participant in the supine 
position. Weight will be recorded in kilograms. 
A vital sign result should be reported as an AE if it meets any of the following criteria: 
• Accompanied by clinical symptoms 
• Results in a medical intervention or a change in concomitant therapy 
• Clinically significant in the investigator’s judgement 
13.2. 
Physical Examination 
Physical and neurological examinations will be performed per the Schedule of Events. The 
assessments included in the exams will be at the discretion of the clinician based on the status of 
the participant at the time of the assessment. 
13.3. 
Electrocardiogram (ECG), Electroencephalogram (EEG) 
A standard 12-lead ECG will be performed per the Schedule of Events and reviewed by a 
cardiologist. A copy of the tracings will be kept on site as part of the source documents. 
A standard EEG will be performed and reviewed by a neurologist. Whether a 1hr or 24hr EEG is 
performed will be at the discretion of the neurologist. 
 
13.4. 
Laboratory Assessments 
Laboratory assessments for safety will be performed by the site’s local laboratory, and all 
certification/qualification documentation will be on file in the TMF. A laboratory test result 
should be assessed as clinically significant or not clinically significant, and should be reported as 
an AE if it meets any of the following criteria: 
• Accompanied by clinical symptoms 
• Results in a medical intervention or a change in concomitant therapy 
• Clinically significant in the investigator’s judgement 
If a clinically significant laboratory abnormality is a sign of a disease or syndrome (e.g., 
hemoglobin below the lower limit of normal associated with anemia), only the diagnosis should 
be recorded. If the abnormality is not a sign of a disease or syndrome, the abnormality itself 
should be recorded (e.g., low calcium). 
 
13.4.1. 
Hematology 
Hematology panel: complete blood count with auto-differential (hematocrit, hemoglobin, platelet 
count, RBC indices, total RBC, total WBC, and WBC differential) 

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13.4.2. 
Blood Chemistry 
Blood chemistry: comprehensive metabolic panel, including albumin, albumin/globulin ratio 
(calculated), alkaline phosphatase, ALT, AST, BUN/Creatinine Ratio (calculated), Calcium, 
Carbon Dioxide, Chloride, Creatinine with GFR Estimated, Globulin (calculated), Glucose, 
Potassium, Sodium, Total Bilirubin, Total Protein, Blood Urea Nitrogen (BUN) 
 
13.4.3. 
Urinalysis 
Urinalysis by dipstick bag: bilirubin, blood, clarity, color, glucose, ketones, nitrite, pH, protein, 
specific gravity, urobilinogen and leukocyte esterase 
 
13.4.4. 
Virus Serology 
Infectious disease testing: hepatitis B, herpes simplex virus, cytomegalovirus, Epstein-Barr virus, 
varicella zoster virus, and toxoplasmosis. 
 
13.4.5. 
CNS 
• Anti-seizure drug levels 
• Cerebral spinal fluid (CSF) assessments: color, appearance, WBC count, RBC count, 
glucose, protein 
 
13.4.6. 
Immunology 
• B-Cell count 
• IgA levels, to determine if an IgA deficient immunoglobulin needs to be used during 
IVIG 
• Quantitative serum IgG, for determining dosing of IVIG 
• Blood collected for research can include anti-AAVrh8 antibodies (ADA), transgene 
antibodies (ADA) and neutralizing antibodies (Nabs) if needed. 
• ELISpot for assessment of capsid and transgene antigen-specific interferon gamma 
producing T cells in human PBMCs 
 
13.4.7. 
Vector Shedding 
Viral shedding will be assessed in Stage 2; the matrices and time points will be added to the 
schedule of assessments via protocol amendment. 
 
13.5. 
Chest X-Ray 
Anteroposterior and lateral chest X-ray will be performed at the first visit (Day -16) and then 
only as clinically indicated. 
13.6. 
Imaging: MRI, MRS, DTI 
Magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS). diffusion tensor 
imaging (DTI), and computerized tomography (CT) scans will be performed under general 
anesthesia (with or without intubation at discretion of investigator). 

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13.7. 
Ophthalmology 
Complete ophthalmologic examination will be performed and documented by an ophthalmologic 
specialist. 
 
13.8. 
Brainstem Auditory Evoked Response (BAER) 
Standard BAER testing for auditory acuity will be documented. 
 
13.9. 
Adverse and Serious Adverse Events 
13.9.1. 
Definition of Adverse Events 
 
13.9.1.1. Adverse Event (AE) 
According to the International Conference of Harmonization (ICH) guideline for Good Clinical 
Practice, an AE is any untoward medical occurrence in a patient administered pharmaceutical 
product and which does not necessarily have a causal relationship with this treatment. 
An AE can therefore be any of the following: 
• Unfavorable and unintended sign (including an abnormal laboratory finding), 
symptom, or disease temporally associated with the use of a medicinal 
(investigational) product, whether or not considered related to the medicinal 
(investigational) product. 
• Any new disease or exacerbation of an existing disease (a worsening in the character, 
frequency, or severity of a known condition) 
• Recurrence of an intermittent medical condition (e.g., headache) no present at 
baseline 
• Any deterioration or abnormality in a laboratory value or other clinical test (e.g., 
ECG, X-ray) that is associated with symptoms or leads to a change in the study 
treatment or concomitant treatment or discontinuation from the study drug 
• Adverse events that are related to a protocol-mandated intervention, including those 
that occur prior to assignment of study treatment. 
All AEs will be captured following the signing of the informed consent form. 
 
13.9.1.2. Serious Adverse Event (SAE) 
A serious adverse event is an AE occurring during any study phase (i.e., baseline, treatment, 
washout, or follow-up), and at any dose of the investigational product, comparator or placebo, 
that fulfils one or more of the following: 
• Results in death 
• It is immediately life-threatening 
• It requires in-patient hospitalization or prolongation of existing hospitalization 
• It results in persistent or significant disability or incapacity 
• Results in a congenital abnormality or birth defect 

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• It is a significant medical event in the investigator’s judgement (e.g., may jeopardize 
the participant or may require medical/surgical intervention to prevent one of the 
outcomes listed above). 
All SAEs that occur following signing of the informed consent form, regardless of treatment 
arm, must be reported within 24 hours of the investigator becoming aware of the event. 
 
13.9.1.3. 
Adverse Events of Special Interest (AESI) 
Dose-limiting toxicities (DLTs) in this study are defined as adverse events of special interest 
(AESIs). The following AESIs are included specifically for AAV vector gene therapy delivered 
directly to the CNS by convection enhanced delivery 
• Infusion-related reactions (adverse event occurring within 24 hours of gene therapy 
infusion) 
• Neurosurgical related complications 
• Type I Hypersensitivity Reaction 
• Liver function test elevations: (Hy’s Law) >3x elevations above the ULN of ALT or 
AST, serum total bilirubin >2xULN 
• Thrombocytopenia defined as a platelet count <150,000/μL 
• Delayed adverse events including but not limited to autoimmune-like reactions 
• Malignancies 
13.10. 
Relationship to Investigational Product, Study Procedure and 
Administration System 
An Investigator who is qualified in medicine must make the determination of relationship 
between an AE and the investigational product received, study procedure and/or administration 
system (e.g., not related, unlikely related, possibly related, probably related, or definitely 
related). The Investigator should decide whether, in his or her medical judgment, there is a 
reasonable possibility that the event may have been caused by the investigational product, study 
procedure and/or administration system. 
If there is any valid reason, even if undetermined, for suspecting a possible cause-and-effect 
relationship between the investigational product and the occurrence of the AE, then the AE 
should be considered “related.” 
If the relationship between the AE/SAE and the investigational product is determined to be 
“possible” or “probable” the event will be considered to be related to the investigational product 
for the purposes of expedited regulatory reporting. 
When assessing a potential relationship between the investigational product, study procedure 
and/or administration system and an AE, the following parameters should be considered: 
• Temporal relationship between the investigational product, surgical procedure and/or 
protocol-specified procedures and the AE 
• The biological plausibility that the investigational product, study procedure and/or 
administration system caused the event 

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• Any underlying/concurrent illness in the participant 
• Concomitant medications the participant may have received 
• How commonly the event occurs in the study population independent of treatment 
13.11. 
Recording Adverse Events 
Adverse events spontaneously reported by the participant and/or in response to an open question 
from the study personnel or revealed by observation will be recorded during the study at the 
investigational site. Clinically significant changes in laboratory values, blood pressure, and 
pulse need not be reported as AEs. However, abnormal values that constitute an SAE or lead to 
discontinuation of administration of study drug must be reported and recorded as an AE. 
Information about AEs will be collected from the signing of consent until the end of the LTFU. 
Serious Adverse Event information will be collected from the signing of consent form until the 
end of the LTFU. The AE term should be reported in standard medical terminology when 
possible. For each AE, the investigator will evaluate and report the onset (date and time), 
resolution (date and time), intensity, causality, action taken, serious outcome (if applicable), and 
whether or not it caused the participant to discontinue the study. 
AE intensity will be assessed according to NCI CTCAE v5.0. 
It is important to distinguish between serious and severe AEs. Severity is a measure of intensity 
whereas seriousness is defined by the criteria under Section 13.9.1.2. An AE of severe intensity 
may not be considered serious. 
13.12. 
Reporting Adverse Events 
All SAEs (related and unrelated) occurring from the signing of consent form until the completion 
of the LTFU must be reported to the Sponsor or designee within 24 hours of the investigator’s 
knowledge of the event. Any SAEs considered possibly or probably related to the 
investigational product and discovered by the Investigator at any time after the study should be 
reported. All SAEs must be reported to Dr. Terence Flotte within 24 hours of the first awareness 
of the event. 
The Investigator must complete, sign and date the SAE pages, verify the accuracy of the 
information recorded on the SAE pages with the corresponding source documents, and send a 
copy by fax to Dr.Terence Flotte at UMass Chan Medical School. 
Additional follow-up information, if required or available, should all be faxed to UMass Chan 
Medical School within one business day of receipt and this should be completed on a follow-up 
SAE form and placed with the original SAE information and kept with the appropriate section 
of the CRF and/or study file. All participants with a SAE must be followed up and the outcomes 
reported until the event has returned to baseline status or resolved. 
SAE reporting will originate in the electronic data capture (EDC) system and an email will be 
sent to the designated responsible parties in Safety. The paper SAE form is in place as a back-up 
in the event that EDC is not accessible to the reported of the SAE: 
• Terry.Flotte@umassmed.edu 
• Provide copy of all relevant source documents, including medical history, hospital 
records and discharge summaries, and concomitant medication pages, as appropriate 

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UMass Chan Medical School is responsible for notifying the relevant regulatory authorities of 
certain events. 
It is the Principal Investigator’s responsibility to notify the IRB or IEC of all SAEs that occur at 
his or her site. Investigators will also be notified of all unexpected, serious, drug-related events 
(7-day and15-day Safety Reports) that occur during the clinical trial. Each site is responsible for 
notifying its IRB or IEC of 15-day or 7-day safety reports required by local regulations or 
IRB/IEC requirements and shall provide the sponsor or its designee with written confirmation of 
said IRB/IEC notification. 
13.13. 
Reporting Device Deficiencies 
Any deficiency in the AXO-AAV-GM2 administration system defined as an inadequacy with 
respect to identity, quality, durability, reliability, safety or performance which includes 
malfunctions, use errors, and inadequate labeling will be recorded in the eCRF and reported 
immediately to the sponsor and the equipment quarantined. 
Device deficiencies that did not lead to an AE but could have led to a medial occurrence should 
also be reported (e.g.): 
a. if suitable action had not been taken 
b. if intervention had not been made, or 
c. if circumstances had been less fortunate 
The sponsor will review all device deficiencies and determine and document in writing whether 
they could have led to a serious adverse device effect (SADE) and report in accordance with 
regulations to all relevant parties. 

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14. 
STATISTICS 
The statistical analysis methods for Stage 1 and Stage 2 will reflect the design elements and 
objectives of each Stage, with descriptive methods and data listings the primary methods used 
for the Stage 1 data, and with a focus on descriptive methods used for the Stage 2 data. Potential 
comparison of outcomes to external control data may be performed and will be described in the 
statistical analysis plan. 
14.1. 
Sample Size 
Stage 1: The objectives of Stage 1 is to evaluate safety and identify the dose to be used in Stage 
2. A sample size of N=1 or 2 participants per dose, is expected to allow for 
differentiation of outcomes sufficient to select the ‘better’ dose. This determination is 
based on an understanding of the target indication and expected characteristics of the 
study treatment, and thus is not based on specific hypothesis-testing assumptions. 
Stage 2: The Primary Efficacy Endpoints for Stage 2 will be the BSID-III Gross Motor domain 
change from baseline to Week 48 (Month 12) and CSF HexA activity change from 
baseline to Week 48 (Month 12). The sample size is not based upon hypothesis testing 
assumptions but rather the desire to assess neurodevelopment of participants at ages 
when they would be expected to be declining based on natural history data. 
14.2. 
General Methods 
Stage 1 includes 12 participants at differing doses of AXO-AAV-GM2 which precludes 
tabulation of outcomes in a mathematically reasonable manner. Thus, the analysis of Stage 1 
outcomes will focus comparisons of individual participant data using graphical displays (e.g., 
line-scatterplots of each participant’s outcomes over time) to allow for visual inspection of any 
trends between participants. Limited tabulations may be created to present overall Stage 1 data 
(e.g., as for adverse event incidence), as the data warrant. The methods provided below are 
generally intended to describe the analysis of Stage 2 outcomes but may also apply to Stage 1 in 
some instances (e.g., adverse event coding). 
Stage 2 will include a comprehensive assessment of both efficacy and safety outcomes, with 
tables, listings, and figures generated. Data will be tabulated and presented using both 
descriptive and inferential statistics (where applicable) where specified. Select continuous 
endpoints will be assessed a mixed model for repeated measures (MMRM) of changes over time 
with effects for visit, the baseline value (of the outcome of interest), and a random effect for 
participant. Graphical displays of least squares mean (LSMean) changes over time will be 
presented. 
The statistical analysis will be undertaken by the Sponsor or a third-party vendor. The statistical 
analysis and report will conform to the relevant ICH requirements. 
SAS version 9.4 or later will be used for the analysis. 
There is no formal hypothesis being tested. However, comparison to external data sources (e.g., 
literature, NH studies) may be performed as the data allow. 

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14.3. 
Analysis Populations 
There are two pre-defined analysis populations in this study. 
• Safety Population: All participants treated with study treatment (either a partial 
dosing or a complete dosing) will be included in the Safety Population. All safety 
analyses (e.g., adverse events, clinical laboratory) will be performed using the Safety 
Population. 
• Intent-to-Treat Population: The Intent-to-Treat (ITT) population will be defined as 
all Safety Population infantile-onset participants from Stage 2 who have received the 
full dose of study medication. All efficacy analyses will be performed using the ITT 
population. This is the primary population of interest for efficacy assessments. 
 
14.4. 
Primary Efficacy Endpoints 
The Primary Efficacy Endpoints are: 
• Clinical Function: BSID-III Gross Motor domain 
− The continuous clinical outcome BSID-III Gross Motor domain will be assessed 
as a change from baseline to Week 48 (Month 12). 
• Surrogate Biologic Marker: CSF HexA activity 
− CSF HexA activity will be assessed as a change from baseline to Week 48 
(Month 12), including the baseline (pre-treatment) value as a covariate in the 
model. 
This is an open-label, single-arm study in which outcomes will be compared to a pre-specified 
external (e.g., NHS) study database or to the literature. There is no alpha-control applied for 
having co-primary endpoints as no formal hypothesis testing is planned. 
 
14.5. 
Secondary Efficacy Endpoints 
Secondary efficacy endpoints include both biologic markers of disease and measurements of 
clinical function. 
For the biologic markers (e.g., CSF HexA at later time points, GM2 ganglioside levels), changes 
from baseline over time will be presented. 
For clinical endpoints, outcomes are measured at multiple time points during the course of the 
12-month period, and thus will be presented as follows: 
Continuous clinical outcomes will be assessed as for the biologic markers, i.e., with changes 
from baseline over time. 
• BSID-III Composite score change from baseline to Week 4, Week 12, Week 24 and 
Week 48 
The proportion of participants will be assessed via time-to-event methods, presented via Kaplan- 
Meier plots. Comparisons to the NHS study will be made, where possible, using similar 
methodology as for the primary clinical endpoint. 

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• Proportion of Motor Milestone responders based on HINE Section 2 (HINE-2) as 
assessed in HINE Section 2 at Week 4, Week 12, Week 24 and Week 48 
• Responder defined as: 
i. The participant demonstrated at least a 2-point increase in the motor milestones 
category of ability to kick or achievement of maximal score on that category 
(touching toes), or a 1-point increase in the motor milestones of head control, 
rolling, sitting, crawling, standing, or walking 
AND 
ii. Among the 7 motor milestone categories (with the exclusion of voluntary grasp), 
the participant demonstrated improvement (as defined in [i]) in more categories than 
worsening 
Motor milestones are important as they provide a contextualized assessment that is 
relatable to everyday function and capabilities (Gaussen 1985). The HINE was 
originally developed to assess development of global neurological function in normal 
infants (Dubowitz et al. 2005, Haataja et al. 1999) and has been evaluated in several 
infant populations (Frisone et al. 2002, Romeo et al. 2016, Ricci et al. 2006). 
HINE is comprised of eight tests: head control, sitting, voluntary grasp, ability to kick 
in supine position, rolling, crawling, standing, and walking. There are 26 possible 
motor milestones that can be achieved using this schema. 
 
 
The HINE-2 contains a standardized tool for assessing motor milestone achievement, 
consisting of structured, developmentally appropriate items that assess incremental 
changes in head control, sitting, voluntary grasp, ability to grasp, ability to kick, 
rolling, crawling, standing, and walking (Bishop et al. 2018). Bishop and colleagues 
reported the first use of the HINE-2 in a prospective nusinersen treatment trial with 
SMA infants and demonstrated that motor milestone assessment using the HINE-2 
was feasible and practical in symptomatic, fragile (extremely low functioning at 

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baseline) infants with type 1 SMA. A natural history study using the HINE-2 
indicated that SMA infants do not achieve motor milestones and seldom make even 
incremental improvements with development, as also reported for a significant 
proportion of individuals with infantile-onset TSD or SD. (De Sanctis et al. 2016) 
For the HINE-2 category of ability to kick, similar to the definition of improvement 
in (i) above, worsening is defined as at least a 2-point decrease or decrease to the 
lowest possible score of no kicking. For the other 6 categories, worsening is defined 
as at least a 1-point decrease. Participants who die or withdrew from the study will be 
counted as non-responders and will be included in the denominator for the calculation 
of the percentage. 
• Proportion of infantile-onset participants maintaining the ability to sit without support 
as assessed in HINE-2 at Week 4, Week 12, Week 24 and Week 48. 
Of the subset of infantile-onset participants enrolled with the ability to sit up – the 
proportion maintaining the ability to sit without support through Week 48 will be 
provided. A Kaplan-Meier plot of time to event (time to loss of ability to sit upright) 
will be provided to allow for visual inspection of the time-profile of the loss. For 
participants who discontinue the study prior to Week 48, every effort will be made to 
determine sitting ability at Week 48. 
14.6. 
Safety Endpoints 
Adverse events will be coded using the MedDRA coding dictionary. Incidence of each system 
organ class and unique preferred term will be tabulated. AE incidence will also be tabulated 
according to relationship to study medication and severity (graded according to NCI CTCAE 
v5.0). Serious AEs and AEs resulting in premature discontinuation will be tabulated. AESIs 
will be tabulated along with all events as well as separately. 

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15. 
ACCESS TO SOURCE DATA/DOCUMENTS FOR MONITORING 
In accordance with ICH GCP (ICH E6(R2)) guidelines, CRAs must have direct access to the 
Investigator’s source documentation in order to verify the data recorded in the eCRF. The CRAs 
are responsible for routine review of the CRFs according to details contained in the Clinical 
Monitoring Plan (CMP) throughout the study, to verify adherence to the protocol, and the 
completeness, consistency, and accuracy of the data being entered on them. The CRAs should 
have access to any participant records needed to verify the entries in the eCRF. The Investigator 
agrees to cooperate with the CRAs to ensure that any problems detected in the course of these 
monitoring activities are resolved. 
 
15.1. 
Audits and Inspections 
During the conduct of the study, the sponsor, its representative, and regulatory authorities may 
conduct audits of any data and any facility participating in the study. The investigator and 
institutions involved in the study will permit such study-related audits and provide direct access 
to all study records and facilities. And the investigator agrees to participate in audits conducted at 
a convenient time in a reasonable manner. 
In the event of an inspection by any regulatory authority, the investigator should promptly notify 
the sponsor. 
15.2. 
Institutional Review Board (IRB) 
The Principal Investigator must obtain IRB approval for the investigation from committees 
within the institution. Initial IRB approval, and all materials approved by the IRB for this study 
including the participant consent form and recruitment materials must be maintained by the 
Investigator and made available for inspection. 

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16. 
QUALITY CONTROL AND QUALITY ASSURANCE 
16.1. 
Deviations from Protocol 
Protocol deviations, except those intended to reduce immediate risk to study participants, will 
only be implemented by Sponsor-initiated amendments. IRB/EC approval must be obtained 
before changes can be implemented. 

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17. 
STUDY COMMITTEES 
17.1. 
Independent Data and Safety Monitoring Committee (DSMC) 
The DSMC is an independent multidisciplinary group (independent of both the sponsor and 
CRO) who collectively has experience in the management of participating participants as well as 
in the conduct and monitoring of clinical trials. 
The DSMC will meet at regular intervals allowing for the timely review of 4-week safety data 
for Stage 1 participants (see Section 8.1.1). The DSMC and Sponsor will determine whether 
enrollment of participants may proceed according to the dose-escalation plan (Table 10). Based 
on satisfactory review of 4-week safety data for each participant, accrued safety data of all 
participants, and review for potential safety signals related to AXO-AAV-GM2 as well as that of 
the neurosurgical administration/infusion procedures, the DSMC may recommend to continue 
the study as designed, to continue the study with modifications (e.g. dose de- 
escalation/escalation in the event of toxicity), or to terminate the study early based on the safety. 
After the last Stage 1 participant has been dosed and observed for 4 weeks, the DSMC will 
review the cumulative safety data in conjunction with the Sponsor and determine the optimal 
AXO-AAV-GM2 dose regimen to be administered in Stage 2. The DSMC will continue to meet 
at regular intervals throughout the duration of the study. 
The DSMC will review enrollment progress, baseline characteristics of the study population, all 
treatment-emergent safety reports, clinical laboratory and imaging data. The members of the 
DSMC will be notified of all SAEs. 
Additional details regarding the specifics of the DSMC operations may be found in the 
DSMC Charter. 

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18. 
ETHICS 
18.1. 
Ethics Review 
The final study protocol, including the final version of the Informed Consent Form (ICF), must 
be approved or given a favorable opinion in writing by an Institutional Review Board (IRB). 
The investigator must have written approval from all required committees before he or she can 
enroll any participant into the study. 
UMass Chan Medical School will be responsible for informing the IRB of any amendment to 
the protocol in accordance with local requirements. In addition, the IRB must approve all 
advertising used to recruit patients for the study. The protocol must be re-approved by the IRB 
upon receipt of amendments and annually, as local regulations require. 
The Principal Investigator is also responsible for providing the IRB with reports of any 
reportable serious adverse drug reactions from any other study conducted with the investigational 
product. 
Progress reports and notifications of serious adverse drug reactions will be provided to the IRB 
according to local regulations and guidelines. 
 
18.2. 
Ethical Conduct of the Study 
The study will be performed in accordance with ethical principles that have their origin in the 
Declaration of Helsinki and are consistent with ICH/Good Clinical Practice, applicable 
regulatory requirements. 
 
18.3. 
Written Informed Consent 
The Principal Investigator(s) at each center will ensure that the participant’s caregiver is given 
full and adequate oral and written information about the nature, purpose, possible risks and 
benefit of the study. Participant’s caregivers must also be notified that they are free to 
discontinue from the study at any time. The participant and caregiver should be given the 
opportunity to ask questions and allowed time to consider the information provided. The 
informed consent should also convey that an autopsy may be requested if the patient dies (from 
any cause) during the study. 
The signed and dated ICF/Assent must be obtained before conducting any study procedures. 
The Principal Investigator(s) must maintain the original, signed ICF. A copy of the signed 
ICF/Assent must be given to the participant’s caregiver. 

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19. 
DATA HANDLING AND RECORDKEEPING 
19.1. 
Retention of Records 
The Principal Investigator must maintain all documentation relating to the study for a period of 2 
years after the last marketing application approval, or if not approved 2 years following the 
discontinuance of the test article for investigation. If it becomes necessary for UMass Chan 
Medical School or the Regulatory Authority to review any documentation relating to the study, 
the Investigator must permit access to such records. 

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20. 
PUBLICATION POLICY 
Publication by the site of any data from this study must be carried out in accordance with the 
clinical study site agreements. A description of this clinical trial will be available on the relevant 
clinical trial registries. 

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