Intellia’s one-time CRISPR therapy cuts hereditary angioedema attacks 87% in Phase 3; rolling FDA filing started

An ahead-of-print report in The New England Journal of Medicine and a same-day conference presentation are putting fresh attention on Intellia Therapeutics’ experimental one-time CRISPR treatment for hereditary angioedema, after the company said its late-stage trial succeeded and that it has started a rolling U.S. regulatory filing.

The treatment, lonvoguran ziclumeran, also called lonvo-z and formerly known as NTLA-2002, is an in-vivo CRISPR/Cas9 gene-editing therapy for hereditary angioedema, a rare inherited disorder marked by recurrent and sometimes severe swelling attacks. In an April 27 press release, Intellia said its Phase 3 HAELO trial showed that a single 50-milligram infusion cut attack rates by 87% versus placebo during the primary efficacy period from weeks 5 to 28. The company said the global, randomized, double-blind, placebo-controlled study enrolled 80 patients age 16 and older with Type I or II hereditary angioedema, with 52 receiving lonvo-z and 28 receiving placebo. Intellia also said it has initiated a rolling Biologics License Application with the Food and Drug Administration, with plans to complete the submission in the second half of 2026.

For patients, the appeal is straightforward. Hereditary angioedema is typically managed with long-term preventive medicines or drugs taken when attacks happen. Intellia says the disease affects about 1 in 50,000 people. A one-time treatment that meaningfully reduces attacks could represent a major change in care if its benefit proves durable and its safety profile holds up over time.

The company’s reported Phase 3 results suggest that possibility, though the therapy is not approved. Intellia said mean monthly attack rates during the primary analysis period were 0.26 for lonvo-z patients compared with 2.10 for placebo, meeting the primary endpoint with p < 0.0001. It also said 62% of treated patients were both attack-free and therapy-free during the six-month efficacy period, compared with 11% in the placebo group, also with p < 0.0001.

“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,” John Leonard, Intellia’s president and chief executive officer, said in the April 27 release.

That broader milestone is a key reason the update is drawing attention beyond hereditary angioedema. In-vivo gene editing means the CRISPR machinery is delivered directly into the body, in this case to inactivate the KLKB1 gene in the liver. Intellia says that is intended to lower kallikrein and downstream bradykinin activity linked to hereditary angioedema attacks. Earlier CRISPR therapies to reach the market used an ex-vivo approach, in which cells are edited outside the body and then returned to the patient. Intellia and collaborators have previously published early-phase in-vivo CRISPR findings in hereditary angioedema, but the new Phase 3 readout is a more advanced randomized dataset.

On safety, Intellia said lonvo-z showed favorable safety and tolerability through the Feb. 10, 2026, data cutoff. The most common treatment-emergent adverse events were infusion-related reactions, headache and fatigue, the company said. Intellia added that all reported adverse events were mild or moderate and that there were no serious adverse events in the lonvo-z arm. Even so, longer-term safety and durability remain central questions for any one-time gene-editing treatment.

“The results we are seeing from lonvo-z demonstrate its potential to eliminate the need for chronic medication and related challenges. If approved as a one-time treatment, I would expect lonvo-z to be an appealing option for many patients,” said Aleena Banerji, the HAELO principal investigator, in the same release.

Additional HAELO data are scheduled to be presented Friday in a late-breaking oral presentation at the European Academy of Allergy and Clinical Immunology, or EAACI, meeting. Intellia has said it could potentially launch the therapy in the United States in the first half of 2027, subject to FDA approval.