Prot #ARGX‐113‐2007: A Phase 2/3, Randomized, Double‐Blinded, Placebo‐Controlled, Parallel‐Group, 2‐Arm, Multicenter, Operationally Seamless Study to Evaluate the Efficacy, Safety, Tolerability, Pharmacodynamics, Pharmacokinetics, and Immunogenicity of Ef