This study explored dose escalation of single-arm, open, single intrathecal injection in patients with delayed onset type 2 SMA. The investigator plans to conduct 2 cohorts. It is expected that each dose will be enrolled 3 subjects, with a total of 6 subjects aged from 2-12 years old.
For safety reasons, first subject of each dose cohort needs to complete a 30-day safety observation. After the researcher determines that the dosing is safe and tolerable, the next two subjects can be enrolled in the cohort; The follow-up dose cohort adopts a sentinel test design, with the first subject of each dose group being a sentinel.
During the DLT observation period, if the subject does not observe DLT and the researcher believes that continuing treatment can bring clinical benefits to the subject, the subject will continue to receive treatment; During the DLT observation period, if there is no occurrence of DLT or ≥ grade 2 adverse events related to the investigational drug, it will be escalated to the next dose. If the subject experiences grade ≥ 2 adverse events related to the study drug, the dose will be expanded to 3 subjects for further safety observation. Each subject in each dose cohort will be enrolled on a case by case basis.