Development of a De Novo Model to Assess the Cost-Effectiveness of a New Treatment Option for Patients With Primary Immunoglobulin a Nephropathy (IgAN)

OBJECTIVES: Immunoglobulin A Nephropathy (IgAN) is a rare progressive chronic kidney disease (CKD). Patients with IgAN are typically younger, less comorbid, and may experience more rapid disease progression than patients with CKD. The nature of disease progression necessitates surrogate endpoints to assess long-term efficacy of IgAN treatments on late-stage disease progression. The first disease-specific therapy for IgAN received marketing authorisation in the UK in 2023 (Nefecon^®, targeted-release budesonide). No IgAN-specific UK cost-effectiveness analyses have been published. A UK-specific cost-effectiveness model was developed to assess treatments for IgAN.

METHODS: A systematic review of IgAN economic literature informed the model structure, assumptions, and data sources for a UK-specific model. IgAN real-world evidence (RWE) from the UK National Registry of Rare Kidney Diseases (RaDaR) was used to address key evidence gaps.

RESULTS: A de novo Markov cohort model, including eight health states and an absorbing mortality state, was developed. The model’s health states were primarily defined by CKD state (eGFR levels, a clinically-accepted measure of kidney function). Patient change in eGFR obtained from clinical trial data informed the transitions between CKD 1–4. A Kaplan-Meier curve estimating the probability of progressing to end-stage renal disease or mortality over time was obtained from UK RaDaR and extrapolated to estimate long-term transitions from CKD 4 to CKD 5. For the intervention arm, a hazard ratio calculated using published data linking relative changes in 1-year eGFR slopes to long-term clinical outcomes was applied to the Kaplan-Meier curve. Standardised mortality ratios from UK RaDaR further informed the risk of mortality from all CKD stages and dialysis.

CONCLUSIONS: Model strengths include the use of clinical trial data, UK-specific RWE, and expert validation. Uncertainty regarding the representativeness of CKD data for patients with IgAN, small patient samples, and use of surrogate endpoints for disease progression may warrant further exploration.