Sibeprenlimab (Voyxact): Anti-APRIL FDA Approved for IgAN
Sibeprenlimab (Voyxact, Otsuka): first anti-APRIL FDA accelerated 2025-11 for primary IgAN proteinuria reduction. VISIONARY interim UPCR -51.2%.
Introduction: An Immunology-First IgAN Therapy
IgA nephropathy is driven by aberrantly O-glycosylated IgA1 (Gd-IgA1) immune complexes. Long treated with RAAS blockade and steroids, the IgAN landscape is shifting as hemodynamic (Sparsentan, Atrasentan) and complement (Iptacopan) agents emerge. The newest pillar is B-cell cytokine targeting: Otsuka / Visterra's Sibeprenlimab (VIS649 / Voyxact), the first humanized monoclonal antibody selectively neutralizing APRIL, received FDA accelerated approval on November 25, 2025 for reducing proteinuria in adults with primary IgAN at risk of disease progression (long-term kidney function benefit not yet established; continued approval contingent on confirmatory clinical benefit data)[1]. This article reviews APRIL–Gd-IgA1 biology, the ENVISION and VISIONARY trials, and the competitive landscape based on public sources.
1. Compound Profile
| Item | Detail |
|---|---|
| Generic name | Sibeprenlimab |
| Brand name | Voyxact |
| Development code | VIS649 |
| Sponsor | Otsuka Pharmaceutical (acquired Visterra 2018, ~USD 430M) |
| Modality | Humanized IgG2 mAb, selective APRIL (TNFSF13) neutralization |
| Dose | 400 mg SC every 4 weeks (Q4W) |
| Approval | FDA accelerated approval 2025-11-25 (IgAN) |
| Designations | Breakthrough Therapy (Feb 2024), EU Orphan Designation |
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2. APRIL–Gd-IgA1 Pathway in IgAN
APRIL Biology
APRIL (TNFSF13) is a TNF-superfamily cytokine promoting plasma cell survival and IgA class switching/production. Its receptors are BCMA and TACI.
IgAN Pathogenesis
- APRIL stimulates IgA1-producing plasma cells → overproduction of Gd-IgA1
- Gd-IgA1 forms immune complexes with autoantibodies
- Mesangial deposition → complement activation, inflammation, mesangial proliferation
- Proteinuria, eGFR decline
Sibeprenlimab neutralizes APRIL without affecting BAFF, aiming to limit the breadth of B-cell pool perturbation. However, the FDA label specifies that VOYXACT can reduce antibody production, may cause immunosuppression with infection risk, can blunt vaccine responses, and that live vaccines are contraindicated. APRIL selectivity alone should not be interpreted as a definitive safety advantage[1].
3. Mechanism & Differentiation
| Agent | Target | Immune Breadth |
|---|---|---|
| Sibeprenlimab | APRIL-selective | IgA-producing plasma cells |
| Atacicept | BAFF + APRIL | Broader B cells + plasma cells |
| Zigakibart (BION-1301) | APRIL-selective (IgG4) | Similar to Sibeprenlimab |
| Rituximab | CD20 | Pan-B cell (non-plasma) |
Sibeprenlimab uses an IgG2 subclass (low FcγR affinity, minimal complement activation) to minimize immune-mediated side effects.
4. Clinical Evidence
4-1. ENVISION Phase 2 (NCT04287985)[2]
- Design: IV monthly, 12 months, dose-ranging (2/4/8 mg/kg), n=155
- 12-month UPCR reduction: 2 mg/kg −47.2%, 4 mg/kg −58.8%, 8 mg/kg −62.0% vs placebo −20.0%
- Complete remission (UPC <300 mg/d): 26.3% in 8 mg/kg vs 2.6% placebo
- Biomarkers: serum APRIL −95.8%, Gd-IgA1 −67.1%
- Mathur M, et al., N Engl J Med 2024;390(1):20-31 (PMID 37916620)
4-2. VISIONARY Phase 3 (NCT05248646)[3]
- Design: double-blind placebo-controlled, 400 mg SC monthly. ClinicalTrials.gov reports actual enrollment of 530; Otsuka/FDA label describes the trial as ~510 adult patients; the accelerated-approval basis is the interim analysis of the first 320 randomized participants
- 9-month prespecified interim (n=320, primary EP): UPCR −50.2% in sibeprenlimab vs +2.1% in placebo, between-group difference −51.2% (95% CI −58.2 to −42.9, p<0.001)
- Key secondary: 24-month eGFR slope readout — Otsuka PR projects data within 2026; the FDA accelerated-approval page lists PMR/PMC final report deadline 2027-04-30
- Safety population (VOYXACT 259 / placebo 251): infections 49% vs 45%, injection-site reactions 24% vs 23%; most events mild-to-moderate. FDA label specifies cautions for immunosuppression, infection, and vaccine response. No meningococcal infections reported in VISIONARY per NEJM/label[1]
- Perkovic V et al., N Engl J Med 2026;394(7):635-646 (PMID 41211929)
4-3. FDA Accelerated Approval (2025-11-25)
- Basis: VISIONARY 9-month UPCR
- Confirmatory: VISIONARY 24-month eGFR slope
- Priority review (PDUFA 2025-11-28)
5. Regulatory & Milestones
- FDA accelerated approval: 2025-11-25 (IgAN)
- EMA / PMDA: public information limited; Japan (Otsuka HQ) trajectory to watch
- Long-term confirmation: VISIONARY 24-month eGFR slope gates full approval
6. Competitive Landscape
| Agent | MoA | Phase | Note |
|---|---|---|---|
| Sibeprenlimab | anti-APRIL (monthly SC) | FDA accelerated approval (2025-11-25) | Selectivity + Q4W dosing |
| Atacicept | BAFF/APRIL dual | Phase 3 (ORIGIN, actual n=376), PDUFA target action 2026-07-07 (not yet approved as of 2026-05-16) | ORIGIN UPCR −46% |
| Zigakibart (BION-1301) | anti-APRIL (IgG4, Q2W SC) | Phase 3 (BEYOND, actual n=383, NCT05852938) | Phase 1/2 UPCR −60% |
| Iptacopan | Factor B (AP) | FDA Aug 2024 accelerated / APPLAUSE final eGFR slowing 49.3% (NEJM 2026-03) | MoA-independent |
| Sparsentan | ETAR/AT1R | FDA approved | Hemodynamic |
| Atrasentan (Vanrafia) | ETAR-selective | FDA accelerated approval 2025-04-02 / ALIGN UPCR -36.1% | Hemodynamic |
| Budesonide-MR (Tarpeyo) | Gut-targeted steroid | FDA approved | Gut-B-cell origin |
IgAN treatment is broadening across multiple mechanism axes: hemodynamic (ARB/ETAR) + complement (Iptacopan) + B-cell/APRIL (Sibeprenlimab approved; Atacicept PDUFA-pending; Zigakibart Phase 3) + gut-B-cell (Budesonide-MR).
7. Preclinical & Biomarkers
- Models: ddY IgAN mice (IgAN-specific model). Note: Myette 2019 (PMID 31027890) also evaluated passive Heymann nephritis, which is a membranous nephropathy model — included for proteinuria/renal-immune pharmacology rather than as an IgAN model (separate disease context)
- Serum biomarkers: APRIL and Gd-IgA1 reduction as direct response markers
- Immune profile: mild total IgA/IgM reduction (BAFF preserved), IgG maintained
- Renal histology: mesangial IgA/C3 deposition, mesangial proliferation
8. Points to Watch
- VISIONARY 24-month eGFR slope (confirmatory readout)
- EMA / PMDA approval in Japan (Otsuka HQ)
- Combination trials with ARB / ETAR / complement / Budesonide-MR
- Expansion to LN, SLE, and other B-cell-driven diseases
- Head-to-head dynamics with Atacicept and Zigakibart
References
1. Otsuka. FDA Accelerated Approval for VOYXACT (sibeprenlimab-szsi) in Primary IgA Nephropathy. Press release, Nov 25, 2025. Otsuka
2. Mathur M, et al. A Phase 2 Trial of Sibeprenlimab in IgA Nephropathy (ENVISION). N Engl J Med. 2024;390(1):20-31. PubMed 37916620 / ClinicalTrials.gov: NCT04287985
3. Perkovic V, et al. Sibeprenlimab in IgA Nephropathy — Interim Analysis of a Phase 3 Trial (VISIONARY). N Engl J Med. 2026;394(7):635-646. PubMed 41211929 / ClinicalTrials.gov: NCT05248646
4. Myette JR, et al. An APRIL-targeted antibody is safe and effective in murine IgA nephropathy. Kidney Int. 2019;96:104-116. PubMed 31027890
5. EMA. Sibeprenlimab orphan designation (EU/3/21/2444). European Medicines Agency
6. FDA. VOYXACT (sibeprenlimab-szsi) prescribing information. FDA label 761434s000lbl.pdf / FDA accelerated approvals page