Onasemnogene Abeparvovec-xioi

Assessed via the developmental milestone checklist, formed of 10 yes/no questions. The developmental milestones are: head control, sitting with support, sitting without support, sitting without support for 30 seconds, hands-and-knees crawling, pulls to stand, standing with assistance, walking with assistance, standing alone and walking alone.

The HFMSE was devised for use in children with SMA to give objective information on motor ability and clinical progression. The HFMSE is formed of 33 assessments rated from 0 (unable to perform functional task) to 2 (able to perform functional task unassisted). Higher scores on the total scale of 0-66 indicates higher levels of motor ability.

Participants will receive pulmonary assessments by a pulmonologist or appropriate clinician. Respiratory device data will be reviewed for participants receiving non-invasive ventilatory support.

Assessed via the swallowing function questionnaire, formed of 4 yes/ no questions and 1 body weight question.

The physical examination includes review of the following systems: head, ears, eyes, nose and throat, lungs/thorax, cardiovascular, abdomen, musculoskeletal, neurologic, dermatologic, lymphatic, and genitourinary. In addition, visual inspection of the spine, back, shoulders, and hips looking for spinal curvature and asymmetry will be carried out. Joints will be assessed for loss of mobility and contractures.

Vital sign measurements will include blood pressure, respiratory rate, pulse, axillary temperature, and pulse oximetry.

Blood samples will be collected for hematology (including complete blood cell count) and chemistry.

Cardiac assessments will include a 12-lead electrocardiogram, transthoracic echocardiogram and Troponin-I.

The observational phase questionnaire includes 7 yes/no questions. Observation categories include: adverse events, hospitalizations, concomitant medications, ventilatory support and feeding support.

An SAE is defined as any adverse event (appearance of \[or worsening of any pre existing\]) undesirable sign(s), symptom(s), or medical conditions(s) which meets any one of the following criteria: * Fatal * Life-threatening * Results in persistent or significant disability/incapacity * Constitutes a congenital abnormality or birth defect * Requires in-patient hospitalization or prolongation of existing hospitalization * Is medically significant e.g. defined as an event that jeopardizes the participant or may require medical or surgical intervention to prevent one of the outcomes listed above

An AESI is defined as an AE occurring during any study phase that fulfills one of the following criteria: * Hepatotoxicity * Thrombotic microangiopathy * Cardiac adverse events * Dorsal root ganglia toxicity * New malignancies * New incidence of a neurologic disorder * New incidence of an autoimmune disorder * New incidence of hematologic disorder

Third Edition (Bayley-III) to be performed in all patients up to 42 months, 15 days of age.

RULM score is based on a scale from 0 to 37 where lower scores reflect poorer upper limb functional ability.

The Cogstate Computerized Cognitive Battery consists of the Identification Test (scored 0 (best) to 1.5708 (worst)), the International Shopping List Test (scored 0 (worst) to 999 (best)), the International Shopping List Test-Delayed Recall (scored 0 (worst) to 999 (best)), the One Card Learning Test (scored 0 (worst) to 1.5708 (best)), and the One Back Test (scored 0 (worst) to 1.5708 (best)).

The CELF-5 Following Directions and Sentence Repetition subtests use scoring that varies based on age, but will be administered to participants 5-21 years of age. The Following Directions subtest will be scored from 0-33 with higher score being more advanced and the Recalling Sentences subtest will be scored from 0-78 with higher score being more advanced.

ACEND score is based on a scale from 1 to 41 where higher scores represent a better caregiver experience

Independent sitting is defined by the World Health Organization Multicentre Growth Reference Study, confirmed by video recording, as a participant who sits up straight unsupported for at least 10 seconds.

Independent sitting is defined by the World Health Organization Multicentre Growth Reference Study, confirmed by video recording, as a participant who sits up straight with head erect for at least 10 seconds; participant does not use arms or hands to balance body or support position.

Defined by the Bayley Scales of Infant and Toddler Development (BSID) Gross Motor (GM) subtest performance criteria number 26, confirmed by video recording, as a participant who sits for at least 30 seconds without assistance from another person or object. The participant was allowed to use their upper extremities.

Defined by the BSID GM subtest performance criteria number 40, confirmed by video recording, as a participant who stands alone for at least 3 seconds unsupported.

Independent sitting is defined as sitting up straight with head erect for at least 30 seconds. This endpoint is a co-primary endpoint. The two co-primary efficacy endpoints were assessed in sequence: The endpoint of functional independent sitting was assessed first and, only when this assessment met statistical significance, was the endpoint of event-free survival assessed.

Survival is defined by the avoidance of combined endpoint of either death or permanent ventilation, which is defined by tracheostomy or by the requirement of ≥ 16 hours of respiratory assistance per day for ≥ 14 consecutive days in the absence of an acute reversible illness, excluding perioperative ventilation. Permanent ventilation is considered a surrogate for death. An acute reversible illness is defined as any condition other than SMA that results in increased medical intervention. The endpoint is a co-primary endpoint. The two co-primary efficacy endpoints were assessed in sequence: The endpoint of functional independent sitting was assessed first and, only when this assessment met statistical significance was the survival endpoint assessed.