Relationship of anifrolumab pharmacokinetics with efficacy and safety in patients with systemic lupus erythematosus

OBJECTIVES: To characterize the relationship of anifrolumab pharmacokinetics with efficacy and safety in patients with moderate to severe SLE despite standard therapy, using pooled data from two phase 3 trials. METHODS: TULIP-1 and TULIP-2 were randomized, placebo-controlled, 52-week trials of intravenous anifrolumab (every 4 weeks for 48 weeks). For the exposure–response analysis, BILAG-based Composite Lupus Assessment (BICLA) or SLE Responder Index [SRI(4)] response rates at week 52 in each quartile/tertile of average anifrolumab serum concentration (C(ave)) were compared for anifrolumab and placebo in all-comers, patients who completed treatment, and IFN gene signature (IFNGS)-high patients who completed treatment, using average marginal effect logistic regression. Relationships between exposure and key safety events were assessed graphically. RESULTS: Of patients in TULIP-1/TULIP-2 who received anifrolumab (150 mg, n = 91; 300 mg, n = 356) or placebo (n = 366), 574 completed treatment, of whom 470 were IFNGS high. In the exposure–efficacy analyses, BICLA and SRI(4) treatment differences favouring anifrolumab 300 mg vs placebo were observed across C(ave) subgroups and all analysis populations. Logistic regression identified C(ave) as a significant covariate for predicted BICLA response, as higher anifrolumab C(ave) predicted greater efficacy. There was no evidence of exposure-driven incidence of key safety events through week 52 in patients receiving anifrolumab 150 or 300 mg. CONCLUSION: While higher C(ave) predicted greater efficacy, consistent positive benefit favouring anifrolumab 300 mg vs placebo was observed in BICLA and SRI(4) responses across C(ave) subgroups in the TULIP trials. There was no evidence of exposure-driven safety events. CLINICALTRIAL.GOV NUMBERS: NCT02446912, NCT02446899