To estimate the onset of action of ozanimod, we analyzed monthly MRI scans in a 24-week, phase 2, randomized, double-blind, placebo-controlled study (RADIANCE [NCT01628393]) of ozanimod 0.46 and 0.92 mg/day in relapsing multiple sclerosis (RMS; N=258).

Knowledge of the onset of action by magnetic resonance imaging (MRI) for disease-modifying therapies in RMS is important for treatment monitoring.

MRI scans were acquired at baseline, W8, W12, W16, W20, and W24. In this post hoc analysis, onset of action was estimated for reduction in number of gadolinium-enhancing (GdE) lesions (primary outcome), number of new/enlarging T2 lesions, T2 lesion volume, number of new un-enhancing T1 lesions (black holes), and whole brain atrophy rate (all secondary outcomes). Onset of action was defined as the earliest time point at which a nominally significant difference (P<0.05) in the rate ratio of the least square means (LSM) and 95% confidence intervals (CIs) between ozanimod 0.92 mg and placebo occurred and was sustained.

Onset of action of ozanimod 0.92 mg based on GdE and new/enlarging T2 MRI lesion activity in this phase 2 study was detected as early as W8, the earliest available MRI time point, with complete separation from placebo beginning at W12.