Intellia Therapeutics Posts Phase 3 HAELO Win for lonvo-z, Begins Rolling FDA BLA Filing

27 Apr 2026, 21:02 by Amy Steele · The Cerbat Gem

Intellia Therapeutics (NASDAQ:NTLA) highlighted top-line results from its Phase III HAELO trial evaluating lonvo-z, an investigational in vivo CRISPR-based gene-editing therapy for hereditary angioedema (HAE), and provided an update on regulatory progress during a company conference call.

Company outlines lonvo-z strategy and HAE unmet need

Chief Executive Officer John Leonard described the update as a milestone for “the entire CRISPR field” and people living with HAE, emphasizing Intellia’s focus on in vivo gene editing delivered to the liver. Leonard said Intellia was “the first in the world to dose patients with in vivo CRISPR-based candidates and the first to advance into phase III,” and characterized the newly reported results as the “world’s first phase III data for an in vivo gene-editing candidate.”

Chief Medical Officer David Lebwohl said HAE is driven by an imbalance in the kallikrein-kinin system that leads to unpredictable swelling attacks, including potentially fatal laryngeal events. Despite widespread use of long-term prophylaxis (LTP), Lebwohl said many patients still experience breakthrough attacks and face burdens from chronic treatment, including frequent administration and payer scrutiny. He estimated there are about 7,000 treated HAE patients in the U.S., with more than 60% on LTP, and said U.S. spending is “about $4 billion annually on chronic HAE medications alone,” excluding other healthcare costs.

Lebwohl said lonvo-z is designed to permanently inactivate the KLKB1 gene to reduce kallikrein and bradykinin and “reset the system.” He also described the intended administration as outpatient: patients took a steroid at home the day before dosing, then received additional premedication and a 2- to 4-hour IV infusion before going home.

Phase III HAELO design and enrollment

Marc Riedl, Professor of Medicine and Clinical Director of the US HAEA Angioedema Center at UC San Diego Health and a HAELO principal investigator, presented the Phase III results. Riedl said HAELO is a placebo-controlled, double-blind, randomized trial in Type 1 and Type 2 HAE, requiring LTP washout during screening to establish an LTP-free baseline attack rate during run-in. Patients were randomized 2:1 to a one-time 50 mg dose of lonvo-z or placebo.

Riedl said the six-month efficacy evaluation period ran from week 5 through week 28 post-dosing. After week 28, patients could enter a blinded crossover and were followed for 18 additional months before long-term follow-up.

A total of 80 patients enrolled, with 52 assigned to lonvo-z and 28 to placebo. Roughly 70% of patients in each arm were female, about half were enrolled in the U.S., and approximately 70% were using LTP at study entry, with lanadelumab most common. The mean monthly attack rate during run-in was 3.5 in both arms.

Efficacy: primary endpoint and attack-free outcomes

Riedl said HAELO met the primary endpoint and all key secondary endpoints with statistical significance. For the primary endpoint (weeks 5–28), the placebo arm had a mean of 2.1 attacks per month versus 0.26 for lonvo-z, an 87% reduction.

Riedl also reported that 62% of lonvo-z patients were attack-free during the efficacy observation period versus 11% on placebo. He emphasized that these patients were also “therapy-free,” taking no other prophylactic or rescue medication during that period.

Within the lonvo-z arm, Riedl said 100% of patients achieved an attack-rate reduction from baseline. He reported 62% were attack-free and therapy-free, while the remaining 38% had not reached attack-free status over the full observation period but showed a 72% reduction versus baseline. Leonard later noted that this 38% bucket could include patients who experienced a single attack early in the observation window and none thereafter, and he said Intellia plans to present more detail at the European Academy of Allergy and Clinical Immunology (EAACI) meeting in June, including swimmer plots and additional subgroup information.

Riedl said early post-crossover data suggested continued improvement, with mean monthly attack rates “near zero” by week 36 among patients who had reached that time point, though he cautioned patient numbers beyond week 28 were limited at the cutoff.

Safety, labeling considerations, and path to filing and launch

Riedl said lonvo-z had a favorable safety and tolerability profile in HAELO as of the data cutoff, with all adverse events mild or moderate and no serious adverse events in the lonvo-z arm. The most common adverse events were infusion-related reactions that were mild to moderate and transient.

Leonard also addressed a question about liver tests, saying there was a single Grade 2 ALT elevation in the trial that occurred “a couple weeks out after dosing,” resolved spontaneously within a week, and was asymptomatic with no therapy provided.

On real-world expectations, Riedl said the 62% attack-free endpoint is challenging because trials rely heavily on patient-reported outcomes, which can capture variable symptoms such as abdominal pain that may be adjudicated as an HAE attack. He added that other HAE therapies often “outperformed in the real world” versus blinded trials, including in open-label extensions, as patient confidence in treatment grows over time.

Riedl said if approved, he would discuss lonvo-z with every patient, but emphasized patient preferences vary. He added that while some patients are satisfied with current therapies, “certainly half and probably more than half” of his patients still discuss ongoing attacks, symptoms, treatment burden, and interruptions due to coverage issues. He also said most patient questions about gene editing relate to long-term safety and that broader education will be important.

Riedl pushed back on the suggestion that on-demand therapies might be unnecessary, saying guidelines still recommend all patients maintain access to on-demand treatment given the risk of rare but life-threatening airway attacks, though he expects usage could decline over time.

Leonard said Intellia recently initiated a rolling biologics license application (BLA) with the FDA and is preparing for potential approval and launch, including building commercial leadership, engaging payers and advocacy groups, and identifying target treatment centers. He said the company plans to present additional data at EAACI and aims, “if approved,” to target a commercial launch in the first half of 2027.

Chief Financial Officer Edward Dulac said Intellia is considering collaboration and distribution agreements to reach patients outside the U.S. and has not disclosed timelines for non-U.S. filings. Dulac also said payer discussions have been ongoing and “very constructive,” noting payers often evaluate one-time therapies as a multiple of the average annual cost. He said the company expects lonvo-z to be priced at a premium, though no price has been set, and added that Intellia is mindful that aggressive pricing could increase resistance, including through step edits.

About Intellia Therapeutics (NASDAQ:NTLA)

Intellia Therapeutics, Inc (NASDAQ: NTLA) is a clinical‐stage biotechnology company focused on developing potentially curative genome editing therapies using the CRISPR/Cas9 platform. The company’s research spans both in vivo and ex vivo applications of CRISPR/Cas9, aiming to correct or disable disease‐causing genes with a single administration. Intellia’s lead in vivo program targets transthyretin amyloidosis (ATTR) by delivering CRISPR/Cas9 machinery directly to the liver, while additional preclinical efforts pursue treatments for hemophilia A, hereditary angioedema and other genetic disorders.