Prime Medicine doses first patient with in-body prime editor for Wilson disease

Prime Medicine has dosed the first patient with PM577a, an in-body prime editor for Wilson disease, the company said. The infusion was given on 5 October 2026 in a global Phase 1/2 trial.

The trial is the first test of prime editing inside the human body. Prime editing is a CRISPR-based technique introduced in 2019. It can swap individual DNA letters, insert new genetic instructions or delete chunks with minimal damage to the genome.

What the trial is testing

PM577a is designed to rewrite DNA inside liver cells. It is given as an infusion. The target is Wilson disease. The therapy has the "potential to offer patients a one-time curative treatment, ideally before irreversible liver and neurological damage occur," Mohammed Asmal, Prime Medicine's chief medical officer, said in a press release.

Whether the edit works in the first patient is unknown. The trial will show whether the therapy is safe and how well it works. Initial clinical data are expected in 2027.

Why prime editing is different

Classic CRISPR-Cas9 cuts through both DNA strands. Much of what gets called editing is the cell scrambling to repair the break, and sometimes it botches the job. In one example, a single cut triggered the loss of large portions of a chromosome. Base editing swaps one DNA letter for another without breaking the double helix. Last year doctors used a custom base editor to treat a baby, KJ Muldoon, who had a life-threatening genetic disorder.

Prime editing goes further. It nicks a single strand, a pegRNA carries the blueprint of the desired edit, and a third component copies the RNA instructions into DNA. In tests, its inventors showed it could in theory correct up to 89 percent of known genetic variants associated with disease.

Casgevy, approved in 2024, was the first CRISPR-based treatment to get the green light, and it edits blood stem cells outside the body. Prime editing has also been used outside the body. In an earlier study, Prime Medicine restored missing DNA letters in blood stem cells from two patients with chronic granulomatous disease. The company is now testing whether it can make an edit directly inside a patient.

What comes next

PM577a is not the first in-body gene editing program. Intellia Therapeutics' in-body CRISPR therapy for hereditary angioedema, lonvoguran ziclumeran, has a biologics license application under priority review, which the FDA accepted in September. Prime Medicine is also developing a second in-body prime editing program. The FDA cleared its investigational new drug application for PM647, aimed at alpha-1 antitrypsin deficiency, in September.

DataM Intelligence forecasts the prime editing and CRISPR market to grow from $6.25bn in 2025 to $13.33bn by 2035, a 7.7 percent compound annual rate from 2026 to 2035. The report notes that programs must show editing reaches the intended tissue, produces a durable effect and manages unintended changes.

The PM577a data will show whether the mechanism translates into benefit.