Objective:To evaluate the long-term safety, tolerability and efficacy of Lacosamide add-on therapy in Chinese children with partial-onset seizures.Methods:SP848 was a global multicenter single-arm study involving 60 Chinese children with partial-onset seizures with the age of 4-17 years who were managed by Lacosamide add-on therapy at seven hospitals across China from April 2018 to May 2019.After treatment with at least two kinds of anti-seizure medications simultaneously or sequentially, partial seizures were still poorly controlled and Lacosamide oral solution (syrup) or tablets were added.The minimum initial oral dose was 2 mg/(kg·d), and the maximum allowable dose was 12 mg/(kg·d)or 600 mg/d during the study period.The dose was adjusted according to the tolerance and seizure control level of partial-onset seizures children.Seizure frequency and the median percentage change in partial-onset seizures per 28 days from baseline to the final visit were recorded, including 50% responder rate and 75% responder rate.Results:A total of 60 Chinese children with the mean age of 9.18 (4.00-15.40) years were included in this interim analysis, involving 39 males and 21 females.The mean course of epilepsy was 5.04 (0.50-15.20) years.A total of 43 patients (71.7%) still have been treated.One patient (1.7%) has completed the 6-12 months of follow-up, and 14 patients (23.3%) have completed the follow-up for less than 6 months.The median change in the frequency of partial seizures every 28 days from baseline to the last visit was -2.91, with its median percentage as -25.46%, and the proportions of ≥50%, while ≥75% responder rate were 40.0% and 28.3%, respectively.A total of 52 patients (86.7%) had 265 treatment emergent adverse events (TEAE), 11 patients (18.3%) had 19 serious TEAE, 37 patients (61.7%) had 127 drug-related TEAE, and 11 patients (18.3%) had 16 TEAE leading to the discontinuation of the trial.The most common TEAE were upper respiratory tract infections (20 cases, 33.3%), followed by drowsiness (16 cases, 26.7%), dizziness (15 cases, 25.0%) and vomiting (13 cases, 21.7%). There were no abnormal changes in the electrocardiographic findings during the treatment.Conclusions:For Chinese patients with partial seizures who are older than the age of 4 years and poorly controlled by other drugs, Lacosamide is effective and well tolerated as an add-on therapy drug.The safety characteristics are consistent with those reported in children and adults.No new safety concerns are identified.