OBJECTIVES: To present a current snapshot of the patient data in a registry of multiple sclerosis (MS) patients being treated with interferon-beta 1a SC (INF) in Portugal (PT).

METHODS: Anonymized data was retrieved from a patient support program database of MS patients treated with INF in PT. Data was checked for missing values and descriptive analysis was run for the available information using STATA18. Missing data was censured, with number of samples being mentioned. Information was available from a total of 38 hospitals. Snapshot date was May 17^th, 2023.

RESULTS: Overall, 414 patients were included in the analysis, 64,3% were female (34,5% male; 0,4% unknown). Average age of the population (n=408) was 51,89 ± 12,12 years, with a median of 51,67 years, a minimum of 17,5 and a maximum of 81,21 years. The average time on treatment (ToT) with CT for the whole population (n=402) was 12,42 ± 8,18 years, with a median of 12,18 years, minimum of 0,05 and maximum of 33,92 years. Overall, 9,2% of patients have started therapy before 2000, with 33,8% of patients having started between 2000-2009, 38,6% between 2010-2019, and 18,4% after the beginning of 2020. Overall, 57% of the patients currently under treatment have been on it for more than 10 years, with 22,4% having been for more than 20 years.

CONCLUSIONS: Data observed characterizes the current Portuguese population being treated with INF. The data shows that for a considerable sample of this population INF has resulted in a long-term treatment without any need for subsequent switch to additional therapies.