baseline to months 1 and 3. RESULTS: All patients treated with AVXS-101 survived event-free to 24 months. A rapid increase in mean CHOP-INTEND scores of 9.8 (n¼12; SD¼3.91) points as early as 1 month and 15.4 (n¼12, SD¼6.36) points at 3 months post-dose were observed. CONCLUSIONS: AVXS-101 appears to induce a rapid and significant improvement in motor function as measured by CHOP-INTEND score relative to nusinersen, consistent with its pharmacological mechanism of action designed to promptly restore SMN expression in motor neurons with a single dose administration. Advances in the understanding of SMA, currently available and investigational pharmacologic treatments, and the gene replacement therapy, AVXS-101, underscore the importance of early diagnosis and treatments with a near-immediate onset of action to maximize clinical improvements.