Lagging Endpoints and Hidden Transition in Lupus Nephritis: A Dynamic Systems Reflection A systems-oriented reflection on urinary biomarkers, intrarenal inflammation, and the limits of proteinuria-based response definitions

This paper belongs to the Dynamic Medicine in Practice series, focusing on clinical interpretations of lagging signals and hidden biological transitions. This paper presents a conceptual reflection on temporal mismatch between biological change and clinical recognition in inflammatory disease, using lupus nephritis as an illustrative example. Recent proteomic findings from the TULIP-LN trial suggest that intrarenal inflammatory activity, reflected by urinary biomarkers such as CD163 and MCP-1, may decrease before conventional clinical endpoints—particularly proteinuria—indicate response. This observation highlights a broader principle: clinical response frameworks based on lagging indicators may underestimate early biological change and obscure ongoing system transitions. The analysis is situated within a dynamic systems perspective, where disease is understood as an evolving trajectory shaped by feedback, compensation, and phase shifts rather than a sequence of isolated events. The purpose of this work is not to replace established clinical endpoints, but to clarify their temporal limitations and to support the development of more dynamic, trajectory-based approaches to disease monitoring and treatment evaluation. This paper is released to establish intellectual priority for the concept that clinical endpoints may function as lagging indicators of underlying biological transitions in dynamic disease systems.