Iptacopan (Fabhalta): Oral Factor B Drug for IgAN/PNH/C3G
Novartis' Iptacopan (Fabhalta), an oral Factor B inhibitor. APPLAUSE-IgAN: eGFR slope +49%. FDA approvals: PNH (2023), IgAN (2024 accelerated), C3G (2025).
Introduction: The First Oral Alternative-Pathway Complement Drug
IgA nephropathy (IgAN), paroxysmal nocturnal hemoglobinuria (PNH), and C3 glomerulopathy (C3G) are clinically distinct but share a common molecular driver: alternative pathway (AP) complement hyperactivation. Anti-C5 antibodies (eculizumab/ravulizumab) block downstream complement partially, yet upstream C3 deposition and tissue injury progress. Novartis' Iptacopan (LNP023 / Fabhalta), an oral selective Factor B inhibitor, is the first oral AP-specific drug approved across all three indications[1][2]. This article covers the MoA, key trials, and competitive positioning based on public sources.
1. Compound Profile
| Item | Detail |
|---|---|
| Generic name | Iptacopan |
| Brand name | Fabhalta |
| Development code | LNP023 |
| Sponsor | Novartis |
| Modality | Oral small-molecule, selective Factor B inhibitor (AP-specific) |
| Dose | 200 mg PO BID |
| Indications | PNH (FDA Dec 2023), IgAN (FDA Aug 2024, accelerated), C3G (FDA Mar 2025) |
| EMA | PNH approved May 2024 |
| Boxed warning / REMS | Boxed warning for serious infections caused by encapsulated bacteria (meningococcal, pneumococcal, Hib). Dispensed only under FABHALTA REMS. ACIP-aligned vaccination ≥2 weeks before first dose, emergency antibiotic prophylaxis when treatment cannot be deferred, and ongoing surveillance for invasive infection symptoms even after vaccination are required |
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2. Alternative Pathway Biology
C3b binds Factor B; Factor D cleaves the complex to form C3bBb (AP C3 convertase), amplifying C3/C5 cleavage and membrane-attack complex (MAC) formation. In IgAN, mesangial IgA immune complexes drive AP activation, leading to C3 deposition, proteinuria, and eGFR decline.
Differentiation vs other complement targets
- Anti-C5 (eculizumab/ravulizumab): downstream only; upstream C3 activation persists
- C3 inhibitor (pegcetacoplan): whole-pathway suppression but breakthrough hemolysis
- Anti-MASP2 (narsoplimab): lectin pathway focus
- Iptacopan: AP-selective; classical and lectin pathways preserved, including serum meningococcal bactericidal activity. Nonetheless, as a complement inhibitor, FABHALTA carries a boxed warning for encapsulated-bacterial infections and is administered under REMS
3. Mechanism
Iptacopan binds Factor B's catalytic site with high affinity (IC50 ≈ 0.01 μM), blocking Bb fragment generation and C3 convertase assembly. Oral dosing rapidly suppresses plasma Factor B activity, disrupting the AP amplification loop and reducing C3 deposition, C3a/C5a anaphylatoxins, and MAC formation.
4. Clinical Evidence
4-1. APPLAUSE-IgAN Phase 3 (NCT04578834)[1]
| Item | Detail |
|---|---|
| Design | Randomized double-blind placebo-controlled, IgAN with UPCR ≥1.0 g/g |
| Interim (9 mo) | UPCR −38.3% vs placebo (95% CI 26.0–48.6%, p<0.0001) / Perkovic V, N Engl J Med 2025;392(6):531-543 (PMID 39453772)[1a] |
| Final (24 mo) | Annual eGFR slope −3.10 vs −6.12 mL/min/1.73m²/yr, 49.3% improvement (p<0.001) / Barratt J, N Engl J Med 2026 |
| Renal composite | HR 0.57 (p=0.003) |
| Safety | Serious infections 6.7% vs 2.1% (managed with vaccination) |
FDA accelerated approval (Aug 2024) was granted on the basis of proteinuria reduction from the interim UPCR data. The 2026 final analysis (Barratt J, NEJM 2026, PMID 41910396; published online March 29, 2026 with simultaneous WCN 2026 late-breaking presentation) reported eGFR-slope benefit, and Novartis has submitted these data to FDA for traditional approval (priority review granted). As of May 2026, the US label still lists IgAN under accelerated approval and states that "it has not been established whether FABHALTA slows kidney function decline in patients with IgAN."
4-2. PNH Phase 3: APPLY-PNH / APPOINT-PNH[3]
- APPLY-PNH (switch from anti-C5): 24-week Hb ≥2 g/dL increase rate 82.3% (iptacopan monotherapy), ≥12 g/dL rate 68.8% vs 1.8% (anti-C5)
- APPOINT-PNH (treatment-naïve): 97% with Hb ≥2 g/dL, 79% reaching ≥12 g/dL transfusion-free
- Peffault de Latour R, et al., N Engl J Med 2024
4-3. APPEAR-C3G Phase 3
- 6-month UPCR −35.1% (p=0.0014); 12-month composite 43.5% vs 25.0%
- FDA approval Mar 2025
5. Regulatory Timeline (US-Centric + Global C3G)
The US FDA leads on IgAN (still accelerated approval), while C3G has expanded globally across the US, Japan, and Europe.
| Date | Agency | Indication |
|---|---|---|
| 2023-12 | FDA | PNH (traditional) |
| 2024-05 | EMA | PNH |
| 2024-08 | FDA | IgAN (accelerated approval, basis: proteinuria reduction) |
| 2025-03 | FDA | C3G ("to reduce proteinuria in adults") |
| 2025-05 | PMDA (Japan) | C3G (label-expansion approval, 2025-05-19) |
| 2026-03 | — | APPLAUSE-IgAN final 24-month data in NEJM + WCN 2026 late-breaking. Novartis submitted to FDA for IgAN traditional approval; priority review granted |
6. Competitive Landscape (IgAN)
| Agent | MoA | FDA Status | Primary EP |
|---|---|---|---|
| Sparsentan | ETAR/AT1R dual | Full approval | UPCR −50% |
| Iptacopan | Factor B (AP) | Accelerated Aug 2024 | UPCR −38.3% + eGFR slope +49% |
| Sibeprenlimab | anti-APRIL | Accelerated Nov 2025 | UPCR −51.2% |
| Atrasentan | ETAR-selective | Accelerated Apr 2025 (IgAN) | UPCR −38.1% |
| Atacicept | BAFF/APRIL | Phase 3 (ORIGIN) | UPCR −46% |
| Zigakibart (BION-1301) | anti-APRIL | Phase 3 (BEYOND) | — |
Iptacopan is the only approved agent targeting complement directly in IgAN, and its non-overlapping MoA versus RAAS / ETAR / APRIL inhibitors makes it a plausible future combination partner (formal combination trial data are limited as of May 2026).
7. Preclinical & Biomarkers
- IgAN-related models: ddY mice (IgAN-specific). Passive Heymann nephritis — a membranous nephropathy model — is sometimes used as a separate complement-mediated kidney-injury context to assess C3 deposition blockade, but it is not an IgAN model
- Complement biomarkers: Bb fragment, urinary sC5b-9, plasma C3a as direct AP activity readouts (pharmacodynamic markers)
- Exploratory pharmacodynamic markers: alongside UPCR / eGFR slope, plasma Bb and sC5b-9 are explored as treatment-response readouts (not established as predictive biomarkers)
8. Points to Watch
- EMA and PMDA IgAN approvals (limited public data currently)
- Long-term infection risk in post-marketing surveillance
- Combination trials with Sibeprenlimab / Sparsentan / Atrasentan — four-pillar strategies
- Expansion to APOL1 FSGS, aHUS, IC-MPGN
- Japan market: PMDA approved PNH in 2024 and added a C3G label expansion on 2025-05-19; next focus is the IgAN filing trajectory
References
1. Barratt J, et al. Iptacopan in IgA Nephropathy — Final 24-Month Data (APPLAUSE-IgAN Phase 3). N Engl J Med. 2026. PubMed 41910396 / NEJM / ClinicalTrials.gov: NCT04578834
1a. Perkovic V, et al. Alternative Complement Pathway Inhibition with Iptacopan in IgA Nephropathy (APPLAUSE-IgAN 9-month interim). N Engl J Med. 2025;392(6):531-543. PubMed 39453772
2. Novartis. FDA grants accelerated approval to Fabhalta (iptacopan) for primary IgA nephropathy. August 2024. Novartis
3. Peffault de Latour R, et al. Oral Monotherapy with Iptacopan in PNH (APPLY-PNH). N Engl J Med. 2024. PubMed 38477987
4. Kavanagh D, Bomback AS, Vivarelli M, et al. Oral iptacopan therapy in patients with C3 glomerulopathy: a randomised, double-blind, parallel group, multicentre, placebo-controlled, phase 3 study (APPEAR-C3G). Lancet. 2025;406(10512):1587-1598. PubMed 41016405 / ScienceDirect / ClinicalTrials.gov: NCT04817618
5. Schubart A, et al. Small-molecule factor B inhibitor for complement-mediated diseases. PNAS 2019;116:7926-7931. PubMed 30926668