Estimation of the Size of the Eligible Population in the United States for Resmetirom: A Novel Investigational Therapy for NASH

OBJECTIVES: The US FDA granted Priority Review for resmetirom for the treatment of adults with nonalcoholic steatohepatitis (NASH) with liver fibrosis. Estimates of the diagnosed, treatment-eligible NASH population are poorly understood; as prevalence of NASH using biopsy, the reference diagnostic standard, is infrequently performed in practice. Alternatively, noninvasive tests for screening are often used for estimation, although their performance varies. This study estimated the size of US resmetirom-eligible population.

METHODS: A conceptual framework was developed, using literature, screening guidelines, resmetirom study criteria, and de novo analyses of the NHANES 2017-March 2020 cycle. It specifies NASH prevalence, proportion with significant liver fibrosis (SLF) without cirrhosis (stages ~F2-F3), Year 1 diagnosis, and new diagnoses in Years ≥2. NASH prevalence was estimated by applying published FibroScan®+AST score cutoffs in participants with steatosis and no other liver disease, and fibrosis staging (based on liver stiffness). NASH diagnosis rates were obtained from published estimates and survey responses. Growth of the treatment-eligible population was projected using published incidence data. Estimates were compared to a NASH budget impact analysis (BIA) from Institute for Clinical and Economic Review (ICER).

RESULTS: In the base case, NASH prevalence of 4.6% was assumed (range:1.3-14.2%), of which ~35% was estimated to have SLF without cirrhosis. Published analyses evaluating diagnosis rates 2 years before/2 years after 18 FDA approvals over a 10-year period suggest a 10% diagnosis rate (range:3.3%-14.3%) & paired with incidence equated to ~16% year-over-year growth in the treatment-eligible population. Assuming a 1-million commercial population, resmetirom-eligible population was estimated as 1,255-1,699 in Years 1-3 following approval. Sensitivity analyses were conducted and comparison to the ICER BIA was influenced by different diagnosis rates.

CONCLUSIONS: Estimation of the treatment-eligible population for the investigational treatment resmetirom depends on NASH diagnosis rates, which are predicted to be <15% in the three years after potential approval.