ObjectivesTo evaluate the time course of clinical response following anifrolumab treatment in patients with SLE.MethodsA post hoc analysis was conducted using pooled data from phase III, randomised, 52-week, placebo-controlled, Treatment of Uncontrolled Lupus via the Interferon Pathway (TULIP)-1 and TULIP-2 trials of intravenous anifrolumab (every 4 weeks, 48 weeks) in patients with moderate-to-severe SLE receiving standard therapy. Anifrolumab 300 mg and placebo groups were compared for British Isles Lupus Assessment Group-based Composite Lupus Assessment (BICLA) response over time, time to sustained BICLA response, SLE Responder Index ≥4 (SRI(4)) response over time, time to sustained Cutaneous Lupus Erythematosus Disease Area and Severity Index Activity (CLASI-A) response and change in glucocorticoid dosage over time. All p values for comparisons were nominal.ResultsOf the 726 evaluated patients (anifrolumab 300 mg, n=360; placebo, n=366), a greater proportion attained a BICLA response in the anifrolumab versus the placebo group from Week 8 (p<0.001); treatment group differentiation was maintained at all subsequent visits to Week 52. Consistently, more patients achieved a BICLA response sustained to Week 52 in the anifrolumab versus placebo group (HR=1.73, 95% CI 1.37 to 2.20). More patients attained SRI(4) response with anifrolumab than placebo from Week 12 (p=0.005). As early as Week 8, more patients achieved CLASI-A skin response sustained to Week 52 with anifrolumab versus placebo (HR=1.72, 95% CI 1.17 to 2.55). Glucocorticoid dosage reductions from baseline were greater in anifrolumab-treated versus placebo-treated patients from Week 20 (p=0.010) through Week 52.ConclusionsAnifrolumab treatment was associated with sustained improvements in overall SLE disease activity and skin responses versus placebo from Week 8, which likely led to greater glucocorticoid reductions in the anifrolumab versus placebo groups from Week 20. These findings provide insights to physicians and patients on when to expect potential clinical responses following anifrolumab treatment.