This study is a single-center, open-label, single-arm, non-randomized, single-dose, dose-escalation investigator-initiated trial (IIT) designed to evaluate the safety, tolerability, and preliminary efficacy of NKG001 Injection administered via different dosing regimens (intravenous \[IV\] alone or intravenous combined with intrathecal \[IV+IT\]) in subjects with Type 1 or Type 2 spinal muscular atrophy (SMA).
A total of 13-21 SMA subjects aged ≤60 months are planned to be enrolled. Based on age at enrollment, subjects will be stratified into two age cohorts for independent evaluation:
Age Cohort 1: subjects aged \<24 months at dosing; Age Cohort 2: subjects aged ≥24 months and ≤60 months at dosing.
Eligible subjects must carry 2 or 3 copies of the SMN2 gene.
Note: Subjects with 3 SMN2 copies must be able to sit independently but unable to walk independently.
Four dose cohorts are planned as follows:
S1: 6.0 × 10\^13 vg/kg, IV S2: 1.2 × 10\^14 vg/kg, IV S3: 6.0 × 10\^13 vg/kg, IV + 6 × 10\^13 vg/person, IT S4: 6.0 × 10\^13 vg/kg, IV + 1.2 × 10\^14 vg/person, IT
Subjects in the S1 cohort (2 SMN2 copies and aged \<24 months at dosing) and the S2 cohort (2 or 3 SMN2 copies and aged ≤60 months at dosing) will receive a single intravenous administration of NKG001 Injection.
Subjects in the S3 and S4 cohorts will receive a single administration of NKG001 Injection via combined intravenous and intrathecal routes. In each of these two cohorts, the first enrolled subject must have 2 SMN2 copies and be aged \<24 months at dosing, while the remaining subjects may have either 2 or 3 SMN2 copies and be aged ≤60 months at dosing.