A Phase 1/2 Study of Intravenous Gene Transfer With an AAV9 Vector Expressing Human Beta-galactosidase in Type I and Type II GM1 Gangliosidosis

The risks of administering this treatment in a subject with GM1 gangliosidosis are not completely known. The major risk associated with intravenous infusion is from the subject s immunological response to the viral capsid and/or the beta-gal protein. To reduce this possibility, immune modulation therapy is being started prior to vector delivery and maintained for six months afterward. There is a theoretical risk that the integration of a small percentage of the rAAV vector DNA into the host cell genome could cause cellular transformation to cancer cells and lead to a malignancy. This has never been seen in subjects receiving intravenous AAV9 gene therapy so the risk of this complication, is likely very low.

Abdominal ultrasound will be performed as part of screening and safety follow- up studies. The ultrasound will be performed in a radiology department and will take approximately 20-30 minutes.

We are proposing the use of immune modulation to transiently deplete B-cells using rituximab. It will be infused at -21 days and -14 days before gene transfer.

Sirolimus is a macrocytic lactone that inhibits T lymphocyte activation and proliferation by inhibiting activation of mammalian Target of Rapamycin (mTOR) kinase that suppresses cytokinedriven T-cell proliferation. We plan to give sirolimus from day -21 to Day 90 with option to extend to day 365 if clinically indicated.

Subjects will receive IV methylprednisolone 1 mg/kg or a maximum dose of 50 mg, 60-120 minutes prior to vector administration on day 0 to mitigate potential acute innate immune response against the vector.

Prednisone (oral solution, dose 0.5 mg/kg) will be taken daily on Days 1-3.

The audiology assessment will be performed in the Audiology Clinic using a standard audiogram to measure thresholds for pure tones and speech, word recognition, tympanometry, and otoacoustic emissions if the subject is capable and tolerant of these measures. The assessment will take approximately 30 minutes. The ABR is a noninvasive neurophysiologic test to evaluate electrical signal transmission from the 8th cranial nerve to the brainstem and the cortex in response to specific tones. Electrodes are placed on the scalp and on each earlobe. An earphone gives off a brief click or tone and the electrodes pick up the brain's responses to these sounds and record them. This will be performed by a trained neurophysiology technician to monitor possible change in hearing during treatment. The procedure will be performed in the Interventional Radiology suite while the subject is sedated following the MRI, fMRI, and MRS of the brain.

Type II subjects - This is a noninvasive enhanced form of X-ray that is used to measure bone loss. Loss of bone density is a known complication with GM1 gangliosidosis due to decrease in weight-bearing activities with disease progression. The procedure will be performed in the Nuclear Medicine Department. The subject s femur, spine, and whole body will be scanned at baseline and then yearly for 3 years. The procedure will take approximately 10 minutes and may be limited due to the subject s cooperation.

Performed as part of screening and for safety before sedated procedures. The ECG will take approximately 10 minutes and may be limited due to the subject s cooperation.

Performed as part of screening. The Echo will be done in the Echo Lab and may take approximately 20-30 minutes. The exam may be limited due to the subject s cooperation level.

Completed at baseline. The subject will also have an EEG if clinically indicated (for example encephalopathy, seizures, or other change in neurological status or if changes on the previous study are deemed to warrant a follow up study) during post treatment follow up. The procedures will be conducted in the Neurology Testing Department. The total time for an awake EEG, including lead placement, is approximately 40 minutes. An extended overnight EEG will take approximately 12 hours. The exam may be limited due to the subject s cooperation level.

Performed on blood and urine include safety labs, clinically indicated labs and research collections. Additional specimens may be collected for the PI s biorepository or as clinically indicated. Blood volumes for clinical diagnostic testing and research will be consistent with Clinical Center laboratory guidelines.

Performed to obtain cerebrospinal fluid (CSF) to measure GM1 ganglioside, beta-gal enzyme, AAV antibodies, Pentasaccharide biomarkers and other research tests. CSF will also be sent for cell count and differential, glucose, protein, and culture as well as CSF neurotransmitters. The amount of CSF obtained will be less than or equal to 0.75 mL/kg body weight. The procedure will be performed while under sedation following MRI imaging. If a sedated MRI is not being performed, then the LP will be performed in consultation with the pediatric consult service using conscious sedation and local anesthesia. The procedure will take approximately 15 minutes.

Magnetic resonance imaging (MRI), functional MRI (fMRI) and spectroscopy (MRS) Procedure/Surgery - The subject will undergo noncontrast MRI, including DTI sequences, fMRI, and MRS in the 3T scanner using the same image acquisition sequences and the same MRS voxels to capture the same metabolites as prior sequencing under natural history protocol 02-HG0107. The MRI, fMRI, and MRS will be interpreted for signs of disease progression or stabilization and any signs of treatment toxicity by two board-certified radiologists with specialty training in neuroradiology. The scan will require anesthesia. Sedation will be administered by the anesthesia service after a preanesthesia consultation to assess risk. The type of sedation and whether the subject will be intubated for the procedure will be at the discretion of the anesthesia service.

Type II Subjects - The Vineland-3 will be administered under the supervision of a psychologist. The Vineland-3 provides several types of scores, measure of personal and social independence designed to examine the domains of communication, daily living skills, social skills and motor development. Other standard neurocognitive instruments may be used depending on the subject s ability, and some visits will (may) include a measure of intelligence /cognitive development if the child is able to achieve a basal score. Neurocognitive testing will take approximately 2-3 hours depending on subject cooperation. The assessments will not address sensitive topics. Type I Subjects - Bayley Scales of Infant and Toddler Development (BSID-III), a well-normed and validated, examiner-administered evaluation of cognition, language, and motor skills for children from birth to 42 months of age.

Neurology exam will be performed by a neurologist in the screening and followup appointments to monitor for any adverse reactions and to assess for clinical response to the treatment. The exam will be scripted for consistency within subject visits and between subjects and will take approximately 30 minutes to one hour. The exam will be videotaped. The exam may be limited due to the subject s cooperation level.

PICC line or other central line placement will be done under sedation in Interventional Radiology. The procedure will be done under sedation and may take 20 minutes. A chest Xray will be done after placement to confirm correct positioning of the catheter.

A skeletal survey will be performed to assess the degree of skeletal involvement of the disease. This will include X-rays of the a/p lateral spine, chest, and pelvis. The exam will take approximately 30 minutes. The exam may be limited due to the subject s cooperation level.

Skin biopsy will be performed on subjects who have not already had a skin biopsy under the 02-HG-0107 protocol. The procedure will be done under sedation using local anesthetic. After washing the skin with chlorhexidine and numbing the skin with injectable lidocaine, a 3mm circle of skin is removed under sterile conditions and the wound is dressed. The entire procedure takes approximately 5 minutes.

Performed as a marker of response to treatment and safety. The swallow assessments will include a parental swallowing questionnaire and cranial nerve assessment. The NIH Swallowing Questionnaire from the Speech Language Pathology Section is designed to identify the presence and or absence of functional swallowing dysfunction as perceived by the subject and or caregiver. This 4point scale assists with further identification of clinical/research assessments of oral pharyngeal swallowing function if indicated in the form of a modified barium swallow. In addition to swallow assessments, tape recording of speech will also be included with diadochokinetic tasks and sustained phonations as well as speech if able. Recordings will be stored on a shared drive accessible only by the study team. The assessment may take approximately 30 minutes to 1 hour.

The ophthalmology exam will be performed by an ophthalmologist in the screening and follow-up appointments to support subtype diagnosis and assess efficacy. Pictures of bilateral macula will be taken and saved to a secure database. OCT will also be performed. These exams will only be administered to Type I subjects.