Primary Sjögren's Disease: a review of unmet need, outcome measures, therapeutic advances and health economic impacts. Lessons from the NEw Clinical Endpoints in primary Sjögren's Syndrome: an Interventional Trial based on stratifYing patients (NECESSITY) Innovative Health Initiative (IHI).

Primary Sjögren's disease (pSjD) is an autoimmune rheumatic disease involving exocrine glands and associated with high symptom burden (dryness, fatigue, pain), systemic features and salivary gland dysfunction. B-cell hyperactivity is common, with an increased risk of mucosa-associated lymphoid tissue lymphoma. This review describes the unmet need, scientific validity of outcome measures, optimisation of clinical trial design, therapeutic advances and how clinical improvement relates to health-related quality of life, additional quality-adjusted life years and economic benefit in pSjD. It derives from the EU-funded Necessity IHI Academic-Industry collaborative Consortium project while also drawing on work by the European Alliance of Associations for Rheumatology Sjögren's task force and others. The NECESSITY Consortium, formed within the framework of the Innovative Health Initiative (IHI), comprises 20 academic partners, 1 patient group partner and 4 industry partners (NECESSITY; https://necessity-h2020.eu). Patient leaders have been closely involved, with expert advice obtained from the European Medicines Agency and the United States Food and Drug Administration during the development phase of a new outcome measure, the Sjögren's Tool for Assessing Response composite response criteria. This tool is now undergoing validation through the NECESSITY IHI clinical trial and industry-sponsored trials.