Clinical trial outcomes for SLE: what we have and what we need.

The paradigm of drug approval in SLE currently relies on successful large phase III randomised controlled trials and a set of primary, secondary and additional end points. Taken together, these outcomes offer a nuanced understanding of the efficacy and safety of the investigational agent. In this review, we thoroughly examine the main outcomes used in SLE trials and highlight unmet requirements as well as potential venues for future trial design in SLE. Disease activity indices can be broadly categorised into global-specific and organ-specific indices, in particular for skin, joints and kidneys, but there is no universal consensus about their use in clinical trials. Because each of these instruments has its own intrinsic strengths and weaknesses, the assessment of treatment response has progressed from relying solely on one individual disease activity index to using composite responder definitions. Those are typically measured from the trial baseline to the end point assessment date and may be combined with the need to taper and maintain glucocorticoids (GCs) within prespecified ranges. Remission and low disease activity are two critical states in the perspective of 'Treat-to-Target' trials, but are not fully recognised by regulators. While significant progress has been made in clinical trial outcomes for SLE, there is a clear need for continued innovation. Addressing these challenges will require collaboration between researchers, clinicians, patients as well as with regulatory agencies to refine existing outcome measures, incorporate meaningful and ethnically diverse patient perspectives, foster relevant digital opportunities and explore new therapeutic avenues, including early use of investigational agents. By doing so, we can advance our ability to manage SLE effectively and safely and improve the lives of those living with this complex and impactful autoimmune disease.