A Study to Assess Efficacy and Safety of Efgartigimod in Adults With Sjogren's Disease-associated Sensorimotor Polyneuropathy or Sensory Polyneuropathy (SERENITY)

Inclusion Criteria: * Is at least 18 years of age and the local legal age of consent for clinical studies when signing the ICF * Meets the following SjD criteria: Fulfilled American College of Rheumatology and the European Alliance of Associations for Rheumatology classification 2016 SjD criteria before screening; Moderate-to-severe disease defined as a ESSDAI ≥ 5 or clinESSDAI ≥ 6 with PNS domain score of ≥ 5 (ie, a score of at least low activity) at screening; Anti-Ro/SS-A positive at a central laboratory at screening * Meets the following SjD-associated polyneuropathy criteria: Diagnosis of SjD-associated SMPN, SPN or sensory ganglionopathy, with neuropathy duration ≤ 5 years at screening and signs of active neuropathic disease development within the last 12 months; patients with co-existing SjD-associated small fiber neuropathy are eligible; No alternative diagnosis of neuropathy etiology; Total mTCNS ≥ 6 at screening; mTCNS sensory test score \<level 3 at screening (does not apply to sensory ganglionopathy cohort where any severity is acceptable) Exclusion Criteria: * Besides the indication under study, known medical conditions that would interfere with an accurate assessment of clinical symptoms of SjD-associated SMPN or SPN or gangliopathy, confound the study results, or puts the participant at undue risk. * Associated (also known as secondary) SjD, defined as overlap with another autoimmune rheumatic or systemic inflammatory condition (eg, rheumatoid arthritis, sys…