Trial Outcomes & Findings for Study of Intrathecal Administration of Onasemnogene Abeparvovec-xioi for Spinal Muscular Atrophy (NCT NCT03381729)

Last Updated: 2026-01-26

Results Overview

Defined by the Bayley Scales of Infant and Toddler Development (BSID) Gross Motor (GM) subtest performance criteria number 40, confirmed by video recording, as a participant who stands alone for at least 3 seconds unsupported.

Recruitment status

TERMINATED

Study phase

PHASE1

Target enrollment

32 participants

Primary outcome timeframe

From Day 1 up to Month 12

Results posted on

2026-01-26

Participant Flow

A total of 32 participants took part in the trial at 11 sites in the United States between December 2017 and May 2021.

A total of 38 participants were screened, of which 6 were screen failures and 32 were enrolled and received study drug.

Participant milestones

Participant milestones
Measure	Cohort 1: 6.0E13 Vector Genomes (vg) - Age 6 to <24 Months Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 6.0E13 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 6 to <24 Months Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 24 to <60 Months Participants aged 24 to \<60 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.
Overall Study STARTED	3	13	12	4
Overall Study Received AVXS-101	3	13	12	4
Overall Study COMPLETED	3	13	12	4
Overall Study NOT COMPLETED	0	0	0	0

Reasons for withdrawal

Withdrawal data not reported

Baseline Characteristics

Study of Intrathecal Administration of Onasemnogene Abeparvovec-xioi for Spinal Muscular Atrophy

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Cohort 1: 6.0E13 Vector Genomes (vg) - Age 6 to <24 Months n=3 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 6.0E13 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 6 to <24 Months n=13 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 24 to <60 Months n=12 Participants Participants aged 24 to \<60 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months n=4 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Total n=32 Participants Total of all reporting groups
Age, Categorical <=18 years	3 Participants n=41 Participants	13 Participants n=1581 Participants	12 Participants n=4626 Participants	4 Participants n=72 Participants	32 Participants
Age, Categorical Between 18 and 65 years	0 Participants n=41 Participants	0 Participants n=1581 Participants	0 Participants n=4626 Participants	0 Participants n=72 Participants	0 Participants
Age, Categorical >=65 years	0 Participants n=41 Participants	0 Participants n=1581 Participants	0 Participants n=4626 Participants	0 Participants n=72 Participants	0 Participants
Age, Continuous	17.2 months STANDARD_DEVIATION 4.1 • n=41 Participants	16.7 months STANDARD_DEVIATION 4.5 • n=1581 Participants	37.5 months STANDARD_DEVIATION 10.6 • n=4626 Participants	16.9 months STANDARD_DEVIATION 5.6 • n=72 Participants	24.6 months STANDARD_DEVIATION 12.5
Sex: Female, Male Female	2 Participants n=41 Participants	6 Participants n=1581 Participants	6 Participants n=4626 Participants	0 Participants n=72 Participants	14 Participants
Sex: Female, Male Male	1 Participants n=41 Participants	7 Participants n=1581 Participants	6 Participants n=4626 Participants	4 Participants n=72 Participants	18 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	2 Participants n=41 Participants	3 Participants n=1581 Participants	0 Participants n=4626 Participants	0 Participants n=72 Participants	5 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	1 Participants n=41 Participants	10 Participants n=1581 Participants	12 Participants n=4626 Participants	4 Participants n=72 Participants	27 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=41 Participants	0 Participants n=1581 Participants	0 Participants n=4626 Participants	0 Participants n=72 Participants	0 Participants
Race/Ethnicity, Customized White	2 Participants n=41 Participants	10 Participants n=1581 Participants	8 Participants n=4626 Participants	3 Participants n=72 Participants	23 Participants
Race/Ethnicity, Customized Asian	0 Participants n=41 Participants	1 Participants n=1581 Participants	4 Participants n=4626 Participants	1 Participants n=72 Participants	6 Participants
Race/Ethnicity, Customized Other	0 Participants n=41 Participants	1 Participants n=1581 Participants	0 Participants n=4626 Participants	0 Participants n=72 Participants	1 Participants
Race/Ethnicity, Customized Multiple	1 Participants n=41 Participants	1 Participants n=1581 Participants	0 Participants n=4626 Participants	0 Participants n=72 Participants	2 Participants

PRIMARY outcome

Timeframe: From Day 1 up to Month 12

Population: Intent-to-Treat (ITT) Set: All enrolled participants who were given an AVXS-101 intrathecal injection. Participants were analyzed according to the assigned dose. Data were only collected in participants aged 6 to \<24 months at time of dosing.

Outcome measures

Outcome measures
Measure	Cohort 1: 6.0E13 Vector Genomes (vg) - Age 6 to <24 Months n=3 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 6.0E13 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 6 to <24 Months n=13 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months n=4 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.
Age 6 to <24 Months Only: Number of Participants Who Achieved the Ability to Stand Alone Able to Stand Alone	1 Participants	1 Participants	0 Participants	—
Age 6 to <24 Months Only: Number of Participants Who Achieved the Ability to Stand Alone Unable to Stand Alone	2 Participants	12 Participants	4 Participants	—

PRIMARY outcome

Timeframe: Baseline and Month 12

Population: ITT Set: All enrolled participants who were given an AVXS-101 intrathecal injection. Participants were analyzed according to the assigned dose. Data were only collected in participants aged 24 to \<60 months at time of dosing.

The HFMSE contained 33 items which were scored on a scale of 0-2 with a total achievable score ranging from 0, if all activities are failed, to 66, if all the activities are achieved. A positive change from baseline indicates a better outcome.

Outcome measures

Outcome measures
Measure	Cohort 1: 6.0E13 Vector Genomes (vg) - Age 6 to <24 Months n=12 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 6.0E13 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 6 to <24 Months Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.
Age 24 to <60 Months Only: Change From Baseline in Hammersmith Functional Motor Scale-Expanded (HFMSE) Score at Month 12	6.0 score on a scale Interval 3.7 to 8.3	—	—	—

PRIMARY outcome

Timeframe: Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3)

Population: Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.

A TEAE was defined as any event that began or worsened in severity on or after the administration of AVXS-101 through the last study visit. Evaluation of TEAEs included the number of participants with at least one: * TEAE * Serious TEAE * TEAE related to AVXS-101 * TEAE with Common Terminology Criteria for Adverse Events (CTCAE) grade ≥ 3 (grade 3 = severe or medically significant to grade 5 = death related to TEAE)

Outcome measures

Outcome measures
Measure	Cohort 1: 6.0E13 Vector Genomes (vg) - Age 6 to <24 Months n=3 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 6.0E13 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 6 to <24 Months n=13 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months n=12 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months n=4 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.
Number of Participants Who Experienced a Treatment-emergent Adverse Event (TEAE) TEAE	3 Participants	13 Participants	12 Participants	4 Participants
Number of Participants Who Experienced a Treatment-emergent Adverse Event (TEAE) Serious TEAE	1 Participants	2 Participants	4 Participants	0 Participants
Number of Participants Who Experienced a Treatment-emergent Adverse Event (TEAE) TEAE Related to AVXS-101	0 Participants	7 Participants	4 Participants	1 Participants
Number of Participants Who Experienced a Treatment-emergent Adverse Event (TEAE) TEAE with CTCAE Grade ≥ 3	1 Participants	4 Participants	4 Participants	0 Participants

SECONDARY outcome

Timeframe: From Day 1 up to Month 12

Population: ITT Set: All enrolled participants who were given an AVXS-101 intrathecal injection. Participants were analyzed according to the assigned dose.

Defined by the BSID GM subtest performance criteria number 43, confirmed by video recording, as a participant who takes 5 coordinated independent steps.

Outcome measures

Outcome measures
Measure	Cohort 1: 6.0E13 Vector Genomes (vg) - Age 6 to <24 Months n=3 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 6.0E13 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 6 to <24 Months n=13 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months n=12 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months n=4 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.
Number of Participants Who Achieved the Ability to Walk Alone Able to Walk Alone	0 Participants	1 Participants	0 Participants	0 Participants
Number of Participants Who Achieved the Ability to Walk Alone Unable to Walk Alone	3 Participants	12 Participants	12 Participants	4 Participants

SECONDARY outcome

Timeframe: Months 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12

Population: Data were only collected in participants requiring BiPAP support.

Participants were assessed by a pulmonologist and may have been fitted with a non-invasive positive pressure ventilatory (e.g., Bilevel Positive Airway Pressure BiPAP) at the discretion of the pulmonologist and/or investigator. The number of hours per day of non-invasive ventilatory support was captured continuously by the device.

Outcome measures

Outcome measures
Measure	Cohort 1: 6.0E13 Vector Genomes (vg) - Age 6 to <24 Months Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 6.0E13 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 6 to <24 Months n=1 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months n=1 Participants Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 2	—	—	10.530 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 3	—	—	2.930 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 4	—	0.000 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	5.860 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 5	—	0.000 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	4.610 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 6	—	2.590 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	4.490 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 7	—	4.550 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	7.490 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 8	—	7.170 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	8.290 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 9	—	8.690 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	7.690 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 10	—	10.320 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	9.900 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 11	—	14.050 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	3.460 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—
Average Number of Hours Per Day of Non-invasive Ventilatory Support Month 12	—	10.120 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	0.040 hours/day Standard Deviation NA Only 1 participant had available data so standard deviation could not be calculated.	—

Adverse Events

Cohort 1: 6.0E13 Vector Genomes (vg) - Age 6 to <24 Months

Serious events: 1 serious events

Other events: 3 other events

Deaths: 0 deaths

Cohort 2: 1.2E14 vg - Age 6 to <24 Months

Serious events: 2 serious events

Other events: 13 other events

Deaths: 0 deaths

Cohort 2: 1.2E14 vg - Age 24 to <60 Months

Serious events: 4 serious events

Other events: 12 other events

Deaths: 0 deaths

Cohort 3: 2.4E14 vg - Age 6 to <24 Months

Serious events: 0 serious events

Other events: 4 other events

Deaths: 0 deaths

Serious adverse events

Serious adverse events
Measure	Cohort 1: 6.0E13 Vector Genomes (vg) - Age 6 to <24 Months n=3 participants at risk Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 6.0E13 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 6 to <24 Months n=13 participants at risk Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 2: 1.2E14 vg - Age 24 to <60 Months n=12 participants at risk Participants aged 24 to \<60 months at time of AVXS-101 dosing received a single 1.2E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.	Cohort 3: 2.4E14 vg - Age 6 to <24 Months n=4 participants at risk Participants aged 6 to \<24 months at time of AVXS-101 dosing received a single 2.4E14 vg dose of AVXS-101 administered as an intrathecal injection on Day 1 of the overall study. Participants also received daily doses of prophylactic oral prednisolone starting at a dose of 1 mg/kg/day from 1 day prior to AVXS-101 injection until at least 30 days post-injection at which point the prednisolone dose could be tapered downwards. At week 9, prednisolone could be discontinued.
Infections and infestations Bronchitis	0.00% 0/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	8.3% 1/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Infections and infestations Influenza	0.00% 0/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	8.3% 1/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Infections and infestations Pneumonia	0.00% 0/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	8.3% 1/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Infections and infestations Pneumonia respiratory syncytial viral	0.00% 0/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	8.3% 1/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Infections and infestations Respiratory tract infection viral	0.00% 0/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	8.3% 1/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Infections and infestations Rhinovirus infection	0.00% 0/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	8.3% 1/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Investigations Blood alkaline phosphatase increased	33.3% 1/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	7.7% 1/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Investigations Alanine aminotransferase increased	0.00% 0/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	7.7% 1/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Investigations Aspartate aminotransferase increased	0.00% 0/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	7.7% 1/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Respiratory, thoracic and mediastinal disorders Acute respiratory failure	0.00% 0/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	8.3% 1/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Respiratory, thoracic and mediastinal disorders Asthma	0.00% 0/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	8.3% 1/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.
Respiratory, thoracic and mediastinal disorders Respiratory failure	33.3% 1/3 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/13 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/12 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.	0.00% 0/4 • Adverse events were collected from the single dose of study treatment until the end of study visit (12 months for Cohort 1 and 2 and 15 months for Cohort 3) Safety Analysis Set: All participants given an AVXS-101 intrathecal injection. Participants were analyzed according to actual dose received.

Other adverse events

Additional Information

EMEA Medical Information

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Principal investigator is a sponsor employee Depending on local requirements, Sponsor's consent necessary before publication of study, or Sponsor can review results communications before public release with a right to request changes to communications regarding trial results between 40 to 60 and up to 90 or 120 days, as applicable, from the time submitted to Sponsor for review to remove references to Sponsor's Confidential Information or delay results communications to permit Sponsor to obtain appropriate Intellectual Property protection.
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Restriction type: OTHER