On 5 October, Prime Medicine said it had dosed the first patient in a trial of a drug called PM577a. The patient has Wilson disease, an inherited condition in which the liver cannot get rid of copper. The drug is a single intravenous infusion. It carries a gene editor in fat particles that the liver takes up, and once inside liver cells the editor is meant to find one wrong letter in one gene and change it back.
That makes it the first trial in which a prime editor has been sent into a living person’s body rather than used on cells in a lab dish. The coverage since has run ahead of the facts. Some outlets reported that the edit had corrected the patient’s DNA and eased their symptoms within weeks. The company has published no result of any kind, and its own release says initial clinical data are expected in 2027.
What is broken in Wilson disease
The gene is ATP7B. It makes a protein that moves copper out of liver cells and into bile, which is how the body disposes of it. When both copies of the gene are faulty, copper builds up in the liver and then spreads to the brain, the kidneys and the cornea. Untreated, it damages the liver and can cause tremors, stiffness and psychiatric symptoms.
There are treatments. Drugs that bind copper and zinc salts that block its uptake keep most patients stable, but they have to be taken every day for life and many people struggle to stay on them. The only cure today is a liver transplant.
PM577a targets one specific fault, a single swapped letter known as H1069Q. Prime Medicine describes it as the most common Wilson disease mutation in North America and Europe. Patients need only one copy of it to qualify for the trial.
Why prime editing is different
Most people know gene editing through CRISPR, which in its original form cuts both strands of DNA and lets the cell repair the break. The repair is messy, and a single cut can sometimes delete large pieces of a chromosome. Prime editing, first described in 2019 by David Liu’s lab at the Broad Institute, nicks only one strand and writes the corrected sequence in directly from an RNA template. It can swap single letters and make small insertions and deletions without the double break.
It has been used in people once before. In December 2025 the New England Journal of Medicine published results from two patients with chronic granulomatous disease, a rare immune disorder. Their blood stem cells were taken out, edited in the lab and put back after chemotherapy cleared room for them. That approach works, but every patient needs a custom batch of their own cells. An infusion that does the editing in place is a different and far harder problem, because the editor has to reach the right cells and do nothing elsewhere.
What the trial will actually measure
The study record on ClinicalTrials.gov is more useful than any headline. It is an open label Phase 1/2 trial with no control group, and it plans to enrol about 42 people at ascending doses. It starts with adults who are already stable on standard treatment, then moves to adolescents. Sites are listed in New Haven, Chicago and San Antonio in the United States and in Auckland, New Zealand, where regulators cleared the trial in June before the US Food and Drug Administration followed in July.
The primary outcome is safety: how often side effects occur and how bad they are, tracked for 48 weeks after the infusion. Everything about whether the drug works is secondary. The trial will look at copper levels in the blood, at ceruloplasmin (a protein that carries copper and is low in Wilson disease) and at PET scans that follow a dose of radioactive copper to see whether the liver can now push it out. It will check how many patients can safely stop their daily medication.
And it will look for the edit itself, by taking a piece of liver at weeks 24 and 48. That is the only direct way to know whether the letter was changed. Until those biopsies come back, nobody can say the patient’s DNA was corrected, including the company. Participants are also asked to join a separate follow up study lasting about 15 years, because a permanent change to the genome needs watching for that long.
What the company is saying
Prime Medicine’s statements are careful. “Dosing the first patient with PM577a is a meaningful step toward our goal of delivering a transformative, one-time treatment for people living with Wilson disease,” said Allan Reine, its chief executive. Mohammed Asmal, the chief medical officer, described the drug as having “the potential to offer patients a one-time curative treatment, ideally before irreversible liver and neurological damage occur.”
Both quotes use the language of intent. The animal work behind the trial, as reported by SingularityHub, found that a single infusion edited roughly half of the liver cells in monkeys. That data was presented at a liver conference in 2024 and has not been published in a peer reviewed journal.
The company is also open about this being a platform bet. The same fat particle delivery can carry a different guide for a different mutation, and a second candidate is already in development for R778L, the most common Wilson disease mutation in East Asian populations. If the first one works, the next ones should be quicker to build.
Why the wait matters
This is a genuine first and it deserves attention. A drug that rewrites DNA inside the body with one infusion would change how a whole class of inherited diseases is treated, and Wilson disease is a sensible place to start because the liver is easy to reach and the target is a single letter.
But a first dose is a starting line. The honest version of the story is that one person has received an experimental gene editor, the trial is designed first of all to find out whether that is safe, and the answer to whether it worked sits in liver biopsies that have not been taken yet. Anyone reporting a cure in October was reporting a hope.
Photograph: Sheila Sund, detail of a native copper specimen at the National Museum of Natural History, Washington DC, CC BY 2.0. Sources: Prime Medicine press release, 5 October 2026; ClinicalTrials.gov NCT07748403; New England Journal of Medicine, doi:10.1056/NEJMoa2509807; SingularityHub, 29 October 2026.