RB001 Gene Therapy Study in Children With SHANK3-related Phelan-McDermid Syndrome (PMS)

To evaluate changes from baseline at weeks 12, 26, and 52 after RB001 injection.

Clinical Global Impression Scale (CGI) severity item provided with a seven-point scale of severity of patient's clinical condition (1=normal, not at all ill; 2=borderline mentally ill; 3=mildly ill; 4=moderately ill; 5=markedly ill; 6=severely ill; 7=among the most extremely ill patients.)

To evaluate changes from baseline at weeks 12, 26, and 52 after RB001 injection.

Clinical Global Impression Scale (CGI) Improvement item provided with a seven-point scale of improvement of patient's clinical condition (1=very much improved since the initiation of treatment; 2=much improved; 3=minimally improved; 4=no change from baseline (the initiation of treatment); 5=minimally worse; 6= much worse; 7=very much worse since the initiation of treatment.)

To evaluate changes from baseline at weeks 12, 26, and 52 after RB001 injection.

The PGI-I consists of a single item in which participants or their parents rate the participant's overall health status relative to baseline using a 7-point scale, scale anchors correspond to those of the CGI-I: 1 = very much improved; 2 = much improved; 3 = minimally improved; 4 = no change; 5 = minimally worse; 6 = much worse; 7 = very much worse.

To evaluate changes from baseline at weeks 12, 26, and 52 after RB001 injection.

The CARS-2 is a clinician-completed rating scale based on direct observation of the child's behavior in standardized contexts. It comprises 15 descriptive items assessing domains including relating to people, imitation, emotional response, body use, object use, and adaptation to change. Each item is scored from 0 to 4, with 0 indicating no abnormality and 4 indicating severe abnormality. The rater integrates behavioral observations with an overall clinical impression of severity to compute a total score ranging from 15 to 60, and converted into a T-score through norm-referenced comparison. Higher T-scores indicate a higher level of autism severity, and a T-score >40 indicates the presence of moderate or above autism-related symptoms.

To evaluate changes from baseline at weeks 12, 26, and 52 after RB001 injection.

The ABC is a clinician-rated instrument based on direct observation of the child's behavior. It includes 57 items distributed across five domains: sensory, relating, body and object use, language, and self-help behavior. Each item is rated as either "yes" (present) or "no" (absent), based on whether the behavior is observed. The total score is calculated by summing the weighted scores of items endorsed as "yes" (item weights vary from 1 to 4). Higher total scores indicate greater autism-related behavioral impairment. The score is interpreted as follows: total < 53 = negative (low risk), 53-67 = suspicious (moderate risk), and ≥ 68 = positive (high clinical concern for autism spectrum disorder).

To evaluate changes of developmental trajectories from baseline at weeks 12, 26, and 52 after RB001 injection, the Griffiths Developmental Assessment Scale - Chinese Version (GDS-C) is accessed by certified examiners. The scale evaluates 240 age-standardized tasks across six domains (Locomotor, Personal-Social, Language, Eye-Hand Coordination, Performance, and Practical Reasoning). Tasks are scored 0 or 1 (1=pass, 0=fail), with raw scores converted to Developmental Quotients (DQ) using China-specific norms (2020 revision). DQ<85 suggests potential mild developmental delay, while a multi-domain DQ<70 indicates significant developmental delay.

To evaluate changes of developmental trajectories from baseline at weeks 12, 26, and 52 after RB001 injection. The PDMS-2 is a standardized, norm-referenced clinical tool used to assess gross and fine motor development in children. Certified clinicians administer age-appropriate items across five domains: reflexes, stationary, locomotion, grasping, and object manipulation. each item is scored based on the child's level of performance, and raw scores are converted to standard scores, percentiles, and composite motor quotients including the gross motor quotient, fine motor quotient, and total motor quotient. Motor quotients are norm-referenced with a mean of 100 and standard deviation of 15. A motor quotient < 85 indicates potential mild motor delay, while a quotient < 70 suggests significant motor developmental impairment.

To evaluate cognitive changes from baseline at weeks 12, 26, and 52 after RB001 injection, the Wechsler Intelligence Scales are administered based on baseline age: WPPSI for subjects aged 2.5-7.7 years at screening, WISC for subjects aged 6-16 years at screening.

the certified neuropsychologist conducts assessments under standardized conditions and assigns scores based on five scales (Verbal Comprehension, Visual Spatial, Fluid/Quantitative Reasoning, Working Memory, Processing Speed) to derive a Full Scale IQ. Scores are norm-referenced (mean=100, SD=15), with higher values indicating superior cognitive ability. IQ<85 suggests potential mild cognitive delay, while IQ<70 indicates significant cognitive delay.

To evaluate changes of functional adaptive behaviors from baseline at weeks 12, 26, and 52 after RB001 injection, the Adaptive Behavior Assessment System-Second Edition (ABAS-2) is administered. the rater (usually the Guardian) score the child's daily living skills across 10 domains (Communication, Self-Care, Social, etc.) using age-specific questionnaires. Items are scored 0-3 based on frequency of competent performance, and raw scores normalized to standard scores based on ages (mean=100, SD=15). The General Adaptive Composite (GAC) serves as the primary secondary endpoint. CAG < 85 suggests potential mild delay, while CAG ≤ 70 indicates significant delay.

To evaluate adaptive functioning from baseline at weeks 12, 26, and 52 after RB001 injection, the Social Life Ability Scale for Infants-Junior Middle School Students (S-M Scale) is administered. Parents or primary caregivers observe the child's daily behaviors and score 132 specific items across six functional domains (Independent Living Skills, Motor Abilities, Practical Task Performance, Communication Skills, Self-Management, and Socialization). Each item is scored 0 or 1 (1 = pass, 0 = fail) based on observed capability. The total score (0-132) is calculated by summing all items, with higher scores indicating better adaptive functioning. A standard score ≤9 (equivalent to a raw score ≤70; ≥2 SD below the norm) suggests significant impairment in social adaptive abilities.

To evaluate behavioral/emotional problems from baseline at weeks 12, 26, and 52 after RB001 injection, the Child Behavior Checklist (CBCL) is administered. Parents or caregivers rate the child's behaviors using 113+ problem items across empirically based syndromes (Anxious/Depressed, Withdrawn/Depressed, Somatic Complaints, Social Problems, Thought Problems, Attention Problems, Rule-Breaking Behavior, and Aggressive Behavior). Each item is scored 0-2 (0 = not true, 1 = somewhat/sometimes true, 2 = very/often true). The total problem score (0-240) is calculated by summing all items, with higher scores indicating greater behavioral/emotional impairment. A T-score >63 (>90th percentile) suggests clinical concern, and >70 (>98th percentile) indicates. (T-scores (M = 50, SD = 10) are derived from normative samples)

To evaluate sleep pattern changes from baseline at weeks 12, 26, and 52 after RB001 injection.

The CSHQ is a validated parent-report screening tool used to assess sleep patterns and common sleep disturbances in children. Parents or primary caregivers rate their child's recent sleep behaviors across multiple domains, including bedtime resistance, sleep onset latency, sleep duration, night wakings, sleep anxiety, parasomnias, sleep-disordered breathing, and daytime sleepiness. The questionnaire consists of 45 items, each scored on a frequency scale based on how often the behavior occurred during the past week: 1 = frequently (5-7 times), 2 = sometimes (2-4 times), and 3 = rarely (0-1 times). The total score is computed using the established scoring criteria; higher total scores indicate more severe sleep problems.

To evaluate viral load dynamics from baseline, at Day 7, Weeks 4, 8, 12, 26, and 52 after RB001 injection, blood samples will be collected at each time point. Viral load will be quantified using RT-qPCR. (Sampling will be discontinued if viral load falls below the lower limit of detection for three consecutive measurements.)

To evaluate Viral shedding from baseline, and at Day 7, Weeks 4, 8, 12, 26, 52 after RB001 injection. Saliva, urine, and feces samples will be collected at each time point. Viral load will be quantified using RT-qPCR. (Sampling will be discontinued if viral load falls below the lower limit of detection for three consecutive measurements.)

To evaluate AAV binding and neutralizing antibodies (Abs) dynamics from baseline, and at Day 7, Weeks 4, 8, 12, 26, 52 after RB001 injection. blood samples will be collected at each time point. Antibodies will be quantified using ELISA (for binding Ab) and cell-coculture (for neutralizing Ab). (Sampling will be discontinued if tests results are negative for three consecutive measurements.)

To evaluate SHANK3 binding antibody (Ab) dynamics from baseline, and at Weeks 4, 8, 12, 26, 52 after RB001 injection. blood samples will be collected at each time point. Antibodies will be quantified using ELISA. (Sampling will be discontinued if tests results are negative for three consecutive measurements.)

To evaluate changes in T-cell responses against AAV and SHANK3 from baseline and at Weeks 26 and 52 after RB001 injection, blood samples will be collected at each time point. Antigen-specific T-cell responses will be quantified using ELISpot assays with peptide pools spanning AAV capsid and SHANK3 epitopes libraries.