Sibeprenlimab (Voyxact): Anti-APRIL for IgAN, FDA Approved
Otsuka's Sibeprenlimab (Voyxact): first selective anti-APRIL antibody. VISIONARY Ph3 interim UPCR -51.2%. FDA accelerated approval Nov 2025. Monthly SC.
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[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 (a.k.a. SHR-1906) |
| 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 |
For researchers tracking fibrosis & inflammation R&D
FDA approval alerts, trial readouts, preclinical model selection, and assay optimization — curated signal for bench-to-pipeline readers. 2 emails/month max.
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, limiting immunosuppression breadth.
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, n=510, 400 mg SC monthly
- 9-month interim (primary EP): UPCR −51.2% vs placebo +2.1% (95% CI 42.9–58.2%, p<0.001)
- Key secondary: 24-month eGFR slope readout expected in 2026 (confirmatory)
- Safety: AE profile comparable to placebo; no meningococcal infections reported
- 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 | Selectivity + Q4W dosing |
| Atacicept | BAFF/APRIL dual | Phase 3 (ORIGIN), PDUFA Jul 2026 | UPCR −46% (Lancet) |
| Zigakibart (BION-1301) | anti-APRIL (IgG4, Q2W SC) | Phase 3 (BEYOND, n=272) | Phase 1/2 UPCR −60% |
| Iptacopan | Factor B (AP) | FDA Aug 2024 accelerated | MoA-independent |
| Sparsentan | ETAR/AT1R | FDA approved | Hemodynamic |
| Atrasentan | ETAR-selective | FDA Mar 2024 | Hemodynamic |
| Budesonide-MR (Tarpeyo) | Gut-targeted steroid | FDA approved | Gut-B-cell origin |
IgAN treatment is shifting toward a four-axis strategy: hemodynamic (ARB/ETAR) + complement (Iptacopan) + B-cell/APRIL (Sibeprenlimab, Atacicept, Zigakibart) + gut-B-cell (Budesonide-MR).
7. Preclinical & Biomarkers
- Models: ddY IgAN mice, passive Heymann nephritis
- 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