The primary objective of the study is to evaluate safety and tolerability as defined by the frequency of the adverse events (AEs) of flu-like symptoms (FLS) [chills, pyrexia, myalgia, and asthenia], injection site reactions (ISRs), and injection site reaction pain (ISR-P), over 24 weeks of treatment (the active comparator period) with PLEGRIDY 125 μg subcutaneous (SC) every 2 weeks versus current SC IFN-β therapy in participants with Relapsing Remitting Multiple Sclerosis (RRMS).