Twenty-five percent of patients treated with cinnoVex were withdrawn from the study due to the non-efficacy (mean frequency of relapses was the same before and after treatment). A significant decrease of relapses was noted in patients treated with genfaxon. The high frequency of side-effects was the major problem in the treatment withgenfaxon. Due to this reason, some patients stopped treatment.A significant decrease of relapses was noted in patients treated with rebif though aversive effects were frequent during the first year of treatment. The effects of biosimilars found in this study are in line with earlier reports. Therefore, the increase of the quality of interferon-beta-1a biosimilars used for MS treatment is needed.