A Phase III, Randomized, Double-blind, Parallel-group, Placebo-controlled Study to Evaluate the Pharmacokinetics, Pharmacodynamics, Efficacy, and Safety of IV Anifrolumab in Pediatric Participants 5 to < 18 Years of Age With Moderate to Severe Active Systemic Lupus Erythematosus While on Background Standard of Care Therapy

This study aims to characterize the pharmacokinetics, pharmacodynamics, efficacy, and safety of anifrolumab solution for infusion compared with placebo solution for infusion in pediatric participants with severe active systemic lupus erythematosus who are on background standard of care therapy. The study duration for a participant will be approximately 116 weeks, which includes: * Screening period of up to 30 days. * Part A consists of a four-week, double-blind, placebo-controlled, randomised, pharmacokinetic period. * Part B is a double-blind, placebo-controlled, randomised, safety/efficacy…