Nexiguran Ziclumeran (Nex-z / NTLA-2001)
Details
Nexiguran ziclumeran (nex-z, also known as NTLA-2001) is an investigational CRISPR-Cas9 in vivo gene editing therapy for transthyretin amyloidosis (ATTR). It is packaged in a hepatotropic lipid nanoparticle (LNP) delivering two components: a single-guide RNA targeting the TTR gene and a human-codon–optimised mRNA encoding Streptococcus pyogenes Cas9 endonuclease. A single intravenous infusion induces NHEJ-mediated permanent knockout of the TTR gene in hepatocytes — the primary source of circulating TTR — achieving deep, sustained suppression of serum TTR without repeated dosing. Developed by Intellia Therapeutics and Regeneron Pharmaceuticals; Phase 3 MAGNITUDE trial ongoing (NCT06128629).
Key Facts
- Class: In vivo CRISPR-Cas9 gene editing; hepatotropic LNP delivery; permanent TTR gene knockout (sources/nexz-crispr-attrcm-nejm-2024 — high)
- Mechanism: Single-guide RNA + Cas9 mRNA packaged in LNP → hepatocyte uptake → NHEJ-mediated TTR gene knockout → permanent reduction in hepatic TTR synthesis (sources/nexz-crispr-attrcm-nejm-2024 — high)
- Delivery advantage vs AAV: LNP is rapidly cleared after administration; no AAV pre-existing immunity concern; no viral genome integration; enables broad patient eligibility (sources/nexz-crispr-attrcm-nejm-2024 — high)
- Phase 1 pharmacodynamics (n=36 ATTR-CM): Mean serum TTR −89% at 28 days; −90% (95% CI −93 to −87) at 12 months; maintained through 24 months in all 11 patients completing 2 years of follow-up (sources/nexz-crispr-attrcm-nejm-2024 — high)
- Depth and consistency of knockdown: Every patient achieved TTR <50 μg/mL by 28 days; 78% achieved <25 μg/mL; effect consistent regardless of TTR genotype (ATTRwt vs ATTRv) (sources/nexz-crispr-attrcm-nejm-2024 — high)
- Dosing (Phase 1): 0.7 mg/kg or 1 mg/kg (dose-escalation); fixed 55 mg (expansion, fixed-dose equivalent of 0.7 mg/kg); single IV infusion ≥2 hours with premedication protocol (sources/nexz-crispr-attrcm-nejm-2024 — high)
- Secondary outcomes at 12 months (no control group): NT-proBNP factor change 1.02 (stable); hs-TnT 0.95 (stable); 6MWT +5 m (stable); KCCQ +8 pts (61% ≥5-point improvement); NYHA improved 47%, stable 44%, worsened 8%; cardiac imaging stable (sources/nexz-crispr-attrcm-nejm-2024 — high)
- Disease stabilization (post hoc): 66% had no worsening on any prognostic marker at 12 months; 83% of NYHA I/II vs 47% of NYHA III (sources/nexz-crispr-attrcm-nejm-2024 — high)
- Safety: Treatment-related AEs: infusion-related reactions 14% (1 severe); transient AST/ALT elevations 6% (resolved ~10 days); vitamin A persistently low (expected — TTR transports retinol-binding protein complex); no clinical vitamin A deficiency; thyroid function normal; 1 death unrelated to treatment (sources/nexz-crispr-attrcm-nejm-2024 — high)
- Comparator context — TTR knockdown depth: Nex-z −90% (permanent, one-time) vs vutrisiran −81% (repeat Q12W SC) vs patisiran −87% (repeat Q3W IV); whether deeper knockdown translates to superior clinical outcomes has not been established in ATTR-CM (sources/nexz-crispr-attrcm-nejm-2024, sources/vutrisiran-attrcm-heliosb-nejm-2025, sources/patisiran-attrcm-apollob-nejm-2023)
- Phase 3 MAGNITUDE trial: International randomised, placebo-controlled trial in ATTR-CM (NCT06128629); ongoing (sources/nexz-crispr-attrcm-nejm-2024 — high)
Contradictions / Open Questions
- Clinical efficacy not yet established: Phase 1 data shows biomarker and functional stability in most patients at 12 months but lacks a randomised comparator; open-label design introduces bias for all functional outcomes; Phase 3 MAGNITUDE trial is required to confirm clinical benefit. (sources/nexz-crispr-attrcm-nejm-2024)
- Deeper TTR knockdown vs better clinical outcomes — not confirmed: Nex-z achieves −90% TTR suppression, exceeding vutrisiran (−81%) and patisiran (−87%). A positive association between knockdown magnitude and outcomes has been demonstrated in hereditary ATTR polyneuropathy, but this has not been established for ATTR-CM. (sources/nexz-crispr-attrcm-nejm-2024)
- Permanent vs reversible knockdown — long-term safety unknown: Unlike RNAi agents (vutrisiran/patisiran) where TTR suppression reverses within months of stopping, nex-z permanently edits the TTR gene. The long-term safety of lifelong TTR deficiency — including vitamin A transport, thyroid hormone binding, retinal function, and peripheral nerve health — requires the planned 15-year surveillance. (sources/nexz-crispr-attrcm-nejm-2024)
- Nex-z vs vutrisiran — no head-to-head comparison: Both target TTR synthesis (permanent knockout vs repeatable mRNA degradation). Vutrisiran has Phase 3 mortality benefit data (HELIOS-B HR 0.65 through 42 months); nex-z has only Phase 1 pharmacodynamic and safety data. Optimal agent selection for ATTR-CM will depend on MAGNITUDE trial results. (sources/nexz-crispr-attrcm-nejm-2024, sources/vutrisiran-attrcm-heliosb-nejm-2025)
Connections
- Related to entities/ATTR-Amyloidosis — indication; disease entity
- Related to concepts/CRISPR-Cas9-in-Channelopathies — gene editing technology and platform; first clinical application to ATTR
- Related to entities/Vutrisiran — comparator RNAi class (HELIOS-B mortality benefit)
- Related to entities/Patisiran — comparator RNAi class (APOLLO-B proof-of-concept; not ATTR-CM approved)
- Related to concepts/TTR-Stabilizer-Therapy — comparator stabilizer class; lifelong dosing vs single-dose gene editing
- Related to concepts/Gene-Editing-Risk-Benefit-Framework — ATTR-CM as paradigm case where gene editing is appropriate given residual disease risk on existing therapies