Lonvoguran Ziclumeran — In Vivo CRISPR Gene Editing in Hereditary Angioedema (Phase 3 HAELO)

Fetch note: The NEJM article page (nejm.org/doi/full/10.1056/NEJMoa2600931, published online June 13 2026) returned HTTP 403 to automated fetch. The figures below are derived from Intellia Therapeutics' primary Phase 3 topline press release (April 27, 2026), which reports the same trial subsequently published in NEJM and presented at EAACI 2026. URL preserved to the peer-reviewed paper of record.

Summary

Intellia Therapeutics reported positive topline results from the global Phase 3 HAELO trial (NCT06634420) of lonvoguran ziclumeran (lonvo-z, formerly NTLA-2002) in patients with hereditary angioedema (HAE). This is the first time an in vivo CRISPR gene editing therapy has met its primary endpoint in a Phase 3 trial — a global first for the modality. Results were announced April 27, 2026, published in the New England Journal of Medicine, and presented at the EAACI 2026 Congress.

Lonvo-z is a single-dose, in vivo CRISPR/Cas9 therapy delivered by lipid nanoparticle (LNP) to the liver, where it permanently inactivates the KLKB1 (kallikrein B1 / prekallikrein) gene. Knocking out KLKB1 lowers circulating kallikrein and bradykinin — the mediators that drive HAE swelling attacks — so a one-time treatment is intended to replace lifelong prophylaxis.

Key Findings (quoted figures)

• 87% reduction in monthly HAE attacks vs placebo (p<0.0001) — the primary endpoint.
• Mean monthly attack rate of 0.26 in the lonvo-z arm vs 2.10 in the placebo arm (weeks 5–28 post-infusion).
• 62% of lonvo-z patients were entirely attack-free and therapy-free over weeks 5–28, vs 11% of placebo patients.
• 80 patients enrolled — 52 received lonvo-z, 28 received placebo.
• Single 50 mg infusion (one-time dose).
• Safety: As of the February 10, 2026 data cutoff, all treatment-emergent adverse events (TEAEs) in the lonvo-z arm were mild or moderate, with no serious adverse events reported in the lonvo-z arm.

Regulatory / Commercial

• Rolling BLA submission initiated with the U.S. FDA; Intellia plans to complete the BLA in 2H 2026.
• Anticipated U.S. launch in 1H 2027.
• Three-year Phase 1 durability data and pooled Phase 1/2 data have been presented at prior allergy/immunology congresses (EAACI, AAAAI 2026), supporting the durability of a single-dose knockout.

Why It Matters

Casgevy (2023) proved CRISPR in an ex vivo setting (cells edited outside the body, then re-infused). Lonvo-z proves the harder in vivo path — editing the patient's own liver directly with a single IV infusion — at Phase 3 scale. It validates the LNP-to-liver, gene-knockout playbook that Verve (cardiovascular) and Beam (AATD, PKU) are pursuing, and sets the first regulatory precedent for an in vivo CRISPR product.

Open Questions

• Long-term (5+ year) durability of the KLKB1 knockout and any need for re-dosing.
• How the FDA frames the benefit/risk of a permanent, irreversible in vivo edit for a non-fatal (though serious) indication.
• Pricing and reimbursement for a one-time curative-intent therapy vs chronic HAE prophylactics.

Source

• Intellia Therapeutics, "Intellia Therapeutics Reports Positive Phase 3 Results in Hereditary Angioedema, Marking a Global First for In Vivo Gene Editing," April 27, 2026 (GlobeNewswire / company IR).
• Peer-reviewed publication: New England Journal of Medicine, DOI 10.1056/NEJMoa2600931 (online June 13, 2026).