Intellia Files BLA After Lonvo-z Meets Phase 3 Endpoints

HAELO meets primary and all secondary endpoints

The regulatory milestone follows positive topline data from the global Phase 3 HAELO trial, announced concurrently on 27 April. HAELO randomised 80 adults and adolescents aged 16 years and older with Type I or Type II HAE to a single 50 mg intravenous infusion of lonvo-z (n=52) or placebo (n=28). Just under half of participants were enrolled at U.S. sites, and 71% had been receiving long-term prophylaxis at study entry – patients required to wash out those regimens in the weeks before dosing.

A single dose of lonvo-z reduced HAE attacks by 87% versus placebo across the six-month efficacy evaluation period from weeks 5 to 28, with a mean monthly attack rate of 0.26 in the active arm compared with 2.10 in the placebo arm (p<0.0001). The trial also met all key secondary endpoints, including a composite measure of being entirely attack-free and therapy-free over the same window – achieved by 62% of lonvo-z recipients versus 11% of those on placebo. As of the 10 February 2026 data cut, every patient who received lonvo-z, whether at baseline or via crossover after week 28, remained free of long-term prophylaxis. Treatment-emergent adverse events through week 28 were predominantly infusion-related reactions, headache and fatigue; all were mild or moderate, and no serious adverse events occurred in the lonvo-z arm.

»As the first Phase 3 data reported for an in vivo gene editing therapy, today's HAELO results represent a profound milestone for Intellia, the broader CRISPR and precision medicine fields and, most importantly, the HAE community,« said John Leonard, Intellia's president and chief executive.

Aleena Banerji of Massachusetts General Hospital's Center for Drug and Vaccine Allergy, a HAELO principal investigator, framed the clinical implication: »If approved as a one-time treatment, I would expect lonvo-z to be an appealing option for many patients.«

Long-term Phase 1/2 data presented at the American Academy of Allergy, Asthma & Immunology meeting in Philadelphia in late February reinforce the durability narrative supporting the Phase 3 read-out. In a pooled analysis of 32 patients dosed with 50 mg of lonvo-z and followed for a median of 12.2 months (range 2.4 months to 3 years), Markus Magerl of Charité – Universitätsmedizin Berlin and colleagues reported mean reductions in plasma kallikrein of 86–96% sustained across follow-up, mean monthly attack rates of 0.2 throughout, and a single serious adverse event – a pulmonary embolism one year post-infusion in a patient with multiple risk factors – that resolved without sequelae (see Figure 2).

Regulatory designations clear a path to 2027 launch

A companion poster led by Banerji introduced a composite endpoint of attack-free and long-term prophylaxis-free status as a working definition of functional cure in HAE. Among the 32 patients in the Phase 1/2 cohort, 97% (31/32) had achieved that status at last follow-up, and 86% of those with at least six months of follow-up had maintained it for six months or longer. The authors argue that the framing parallels how oncology and hepatology have evolved their therapeutic ceilings as new modalities arrived.

The regulatory pathway has been accelerated through the FDA's Regenerative Medicine Advanced Therapy designation, which permits rolling submission and supports expedited review, and Intellia's participation in the agency's Chemistry, Manufacturing, and Controls Development and Readiness Pilot. Lonvo-z also carries Orphan Drug Designation in both the United States and European Union, the U.K. Medicines and Healthcare products Regulatory Agency's Innovation Passport, and the European Medicines Agency's PRIME designation – a regulatory portfolio signalling coordinated trans-Atlantic ambition.

For a field that has spent more than a decade contending with the operational complexity of ex vivo cell engineering, an approval would be transformative. Lonvo-z is an outpatient infusion targeting a chronic disease with established pharmacology – a setting that, unlike one-off ex vivo cures, scales. Whether commercial uptake validates the broader in vivo thesis will depend on payer reception and traction among patients well-served by current chronic prophylactics, but the clinical case for displacement is now on the table.

This article draws on two Intellia Therapeutics press releases from 27 April 2026 (the BLA submission and Phase 3 results) and two poster presentations from the AAAI Annual Meeting 2026 (long-term durability and long-term prophylaxis).