The goal of this retrospective observational study is to investigate the long-term safety of Fingolimod in individuals with Multiple Sclerosis (MS), specifically focusing on the risk of developing skin cancer. The main question it aims to answer is:

• Does the use of Fingolimod increase the incidence of skin cancer in individuals with MS compared to those using other disease-modifying therapies? Participants who are new users of Fingolimod or other active comparators as part of their regular medical care for MS will be included in this study. Researchers will use advanced causal inference techniques to analyze healthcare data and compare the incidence of skin cancer between these groups.

Inclusion Criteria:

• Identified MS cohort with hospital/physician and prescription claims classified according to the international classification of disease codes and drug identification numbers respectively, using a validated case definition. This case definition requires an individual to have at least three health care encounters (any combination of inpatient encounter, outpatient encounter, or DMT dispensation) for MS in a 1-year window
• MS patients who initiated and used fingolimod, natalizumab, alemtuzumab, dimethyl fumarate, or teriflunomide as monotherapy following MS identification.

Exclusion Criteria:

• Pediatric (<18 years old) MS cases.
• MS cases with less than three years of baseline data before the first drug dispensation.
• MS cases with skin cancer in the three-year baseline period

Individuals diagnosed with MS at age 18 or older who received fingolimod, natalizumab, alemtuzumab, DMF, or teriflunomide for the treatment of relapsing-remitting MS between 2003 and 2020.