US IgA Nephropathy Launch Readiness

Budesonide (Tarpeyo, ~60% IgAN-specific share) and sparsentan (Filspari) are both marketed under FDA accelerated approval based on the UPCR proteinuria surrogate, with confirmatory eGFR-outcome data still pending (NefIgArd Part B; PROTECT 2-year). Of an estimated 150,000 US IgAN patients (70,000-90,000 biopsy-confirmed), only 5,000-8,000 are on novel therapy today — a low penetration rate driven in part by payer caution around accelerated-approval status: several major payers have already tightened UPCR thresholds beyond the FDA label pending confirmatory data, and some have signalled non-coverage risk if confirmatory trials disappoint.

The addressable near-term market is not the full IgAN population but the high-risk cohort — an estimated 15,000-25,000 US patients with UPCR >1g/g and declining eGFR who have already been optimised on ACEi/ARB and, increasingly, SGLT2i (DAPA-CKD's IgAN subgroup showed a 41% ESRD-composite reduction). Nephrology KOLs have moved past UPCR as the practice endpoint; eGFR slope is what predicts ESRD prevention and what the specialist community actually uses to judge a drug (NefIgArd: +3.87 mL/min/year; PROTECT: -2.0 vs -4.7 mL/min/year at 2 years).

For a pre-launch entrant, a standard FDA approval built on confirmed eGFR-slope data, rather than a second accelerated approval on UPCR alone, is the single clearest way to differentiate on payer terms from day one, sidestepping the confirmatory-data overhang both incumbents carry. ICER has flagged IgAN for a 2024-2025 pre-assessment; at budesonide's ~$60,000-70,000/year WAC, the cost/QALY model sits near the $100,000-175,000 threshold depending on how eGFR benefit translates to ESRD delay — a new entrant pricing at parity with eGFR-confirmed data would have a materially stronger ICER position. Pre-launch priorities: engage nephrology KOLs now on eGFR-slope evidence, model the UPCR-to-eGFR bridge for payer medical directors, and begin Part D PBM contracting and proactive ICER dialogue 18-24 months ahead of launch.

This assessment synthesises three independent research angles into one integrated pre-launch view: competitive positioning, target-population epidemiology, and anticipated payer posture. Every figure is drawn from the named primary source in the underlying research base and cross-checked before inclusion; no figure is carried from model memory.

IgAN launch-readiness sources: IQVIA IgAN market data 2024 and claims database analysis 2023; Coon JT et al., Kidney Int 2022 (US IgAN prevalence); Barratt J et al., NEJM 2023 (NefIgArd); Heerspink HJL et al., NEJM 2023 (PROTECT); Wheeler DC et al., NEJM 2022 (DAPA-CKD IgAN subgroup); KDIGO IgAN 2021 with SGLT2i addendum; APPLAUSE-IgAN ClinicalTrials.gov results 2024; Vera Therapeutics ORIGIN trial; GSK sibeprenlimab Phase 3; UHC/Cigna IgAN PA criteria 2024; ICER 2024-2025 assessment pipeline; ASN membership IgAN subspecialist list; NephCure IgAN prescriber database.