CRISPR therapy, which rewrites genes within the body, has completed its first Phase 3 trial.

A research team from Amsterdam University Medical Center and other institutions presented the results of a trial of CRISPR therapy in patients with hereditary angioedema at the annual meeting of the European Association for Allergy, Clinical Immunology (EAACI) held in Istanbul, Turkey on June 13, 2026.

In Vivo CRISPR Gene Editing in Hereditary Angioedema | New England Journal of Medicine
https://www.nejm.org/doi/full/10.1056/NEJMoa2600931

World first: First phase 3 trial of in vivo CRISPR therapy successfully completed CRISPR treatment comes one step closer to reality | EurekAlert!
https://sciencesources.eurekalert.org/news-releases/1131680

Intellia Therapeutics Reports Positive Phase 3 Results in Hereditary Angioedema, Marking a Global First for In Vivo Gene Editing
https://ir.intelliatx.com/news-releases/news-release-details/intellia-therapeutics-reports-positive-phase-3-results

CRISPR is a gene editing technology that modifies DNA at targeted locations. In the medical field, its application to treating genetic diseases is progressing, and in this Phase 3 trial, CRISPR therapy that directly edits genes in the patient's body was validated. According to the research team, this is the first time that such a Phase 3 trial of CRISPR therapy has been completed.

Phase 3 trials are a stage in which a treatment under development, which has shown some safety and efficacy in previous clinical trials, is tested on a larger number of patients to confirm its effectiveness and potential side effects. Often compared to standard treatment or a placebo (dummy drug) that does not contain the active ingredient, the purpose is to collect important data used to decide whether or not to approve the drug or treatment.

The subject of this trial, 'hereditary angioedema,' is a rare genetic disorder characterized by recurrent episodes of swelling in the face, airways, abdomen, and limbs. These episodes not only cause pain and disrupt daily life, but can also be life-threatening if they occur in the airways. A trial of the CRISPR treatment 'lonvoguran ziclumeran (lonvo-z),' administered via a single intravenous infusion, was conducted for this disease. Lonvo-z is designed to utilize CRISPR-Cas9 to directly inhibit the KLKB1 gene, which is involved in hereditary angioedema, from functioning in the patient's body.

In the trial, 80 patients with hereditary angioedema were randomly divided into two groups: one receiving lonvo-z and the other receiving a placebo. Both groups received the drug intravenously. The frequency of seizures was then examined from week 5 to week 28 after administration. The study found that patients who received lonvo-z had an 87% lower seizure frequency compared to those who received a placebo.

In addition, the need for medication during seizures decreased by 89%, moderate to severe seizures decreased by 91%, and indicators of quality of life improved significantly compared to patients who received a placebo.

During the 6-month evaluation period, 62% of patients who received lonvo-z and 11% of patients who received placebo did not experience any seizures and did not require any further treatment to prevent seizures. Regarding this, Danny Cohn of the University Medical Center Amsterdam stated, 'It is not certain that all reported swellings were seizures due to hereditary angioedema, as trial participants tended to use the medication early when they felt signs of swelling.' He added, 'If participants knew they had received the active ingredient, they may be more confident in refraining from taking the medication, potentially leading to an increase in the number of patients who are judged as completely seizure-free.'

Regarding the safety of lonvo-z, common side effects include mild infusion-related reactions, headache, fatigue, and back pain, but no serious health problems have been reported in patients who received lonvo-z after treatment.

According to Cohn, data from the previous Phase 1 and Phase 2 trials, which followed 37 participants, showed that the efficacy and safety of lonvo-z were maintained even four years after administration. Cohn stated, 'If a single treatment can provide long-term management of a serious chronic disease, it could reduce the burden of continuing treatment and anxiety about future seizures.'

As of the time of writing, lonvo-z has not yet received regulatory approval, but Cohn explains that these results are 'necessary data for regulators to determine whether lonvo-z can be marketed as a drug.' He then summarizes the results of this trial as 'opening the way for applying CRISPR therapy, which directly edits genes in the body, to patients with other genetic disorders.'