Prime Medicine Doses First Patient With an In Vivo Prime Editor for Wilson Disease
On October 5, 2026, Prime Medicine announced that the first patient has been dosed in its Phase 1/2 trial of PM577a, an investigational prime-editing therapy for Wilson disease. It is the company's first clinical test of a prime editor delivered directly into the body, rather than used to edit cells in a lab.
The therapy is designed as a single intravenous infusion that corrects one of the most common Wilson disease mutations inside liver cells. If it works, it could replace a lifetime of daily medication with a one-time treatment.
What Wilson disease does
Wilson disease is an inherited disorder of copper handling. It is caused by mutations in the ATP7B gene and is autosomal recessive, meaning a person must inherit a faulty copy from each parent. It affects roughly 1 in 30,000 people.
The ATP7B protein is a copper pump in liver cells. It has two jobs:
Loading copper onto ceruloplasmin, the main copper-carrying protein in blood.
Moving excess copper into bile so the body can get rid of it.
When ATP7B does not work, copper builds up in the liver, causing inflammation, scarring, and in some patients sudden liver failure. Copper then spills into the bloodstream and collects in the brain, where it can cause tremors, slurred speech, trouble swallowing, movement problems, and psychiatric symptoms. A copper-colored ring at the edge of the cornea, called a Kayser-Fleischer ring, is a classic sign. Diagnosis is often delayed because symptoms can begin anywhere from childhood to middle age and can resemble other liver or psychiatric disorders.
Current treatment uses chelating drugs such as penicillamine or trientine, which bind copper so it can be removed, or zinc, which blocks copper absorption in the gut. These must be taken every day for life. Side effects and missed doses are common, and some patients still need a liver transplant.
The H1069Q mutation
Hundreds of different mutations in ATP7B have been reported, but one stands out. H1069Q swaps a single amino acid, histidine for glutamine, at position 1069 of the protein. It is the most common Wilson disease mutation in people of European ancestry.
The H1069Q protein folds poorly. The cell's quality-control system holds it in the endoplasmic reticulum instead of sending it to work, so the copper pump never reaches its proper place. Correcting the single DNA letter behind this change should allow liver cells to make normal ATP7B again.
How prime editing fixes it
Prime editing was developed in David Liu's lab at the Broad Institute in 2019. The editor has three key parts:
A Cas9 nickase, which cuts only one strand of DNA instead of both.
A reverse transcriptase, an enzyme that writes DNA from an RNA template.
A prime editing guide RNA (pegRNA), which directs the editor to the target and carries the template for the corrected sequence.
The editor nicks the target strand, then copies the correct sequence into the DNA from the pegRNA. The cell resolves the mismatch in favor of the new sequence. Because no double-strand break is made, the risk of large unwanted DNA changes is lower than with standard Cas9 cutting.
PM577a is packaged in lipid nanoparticles, tiny fat-based particles that are taken up mainly by the liver after an intravenous infusion. The particles carry the editing instructions into liver cells, where the edit is made and the editing molecules are then broken down. The corrected gene stays, and it is passed on whenever an edited liver cell divides.
Prime Medicine has already tested prime editing in patients outside the body, in its treatment for chronic granulomatous disease, which edits blood stem cells in the lab. Gene Tech Times covered that program in Prime Medicine Seeks FDA Approval for the First Prime-Editing Therapy. PM577a moves the technology inside the body.
How the trial is designed
The global Phase 1/2 trial (NCT07748403) is open-label and tests increasing doses. It will enroll adults and adolescents with at least one H1069Q copy, starting with clinically stable adults who stay on standard treatment.
Because the goal is to restore copper excretion, the trial will use measures that track copper handling directly:
Copper-64 PET imaging, which follows a tracer dose of radioactive copper to see how well the liver moves it out.
Serum ceruloplasmin, which should rise if working ATP7B is loading copper onto it again.
The FDA has granted PM577 Rare Pediatric Disease designation. Prime Medicine expects the first clinical data in 2027.
Why a partial fix may be enough
Carriers of Wilson disease, who have one working copy of ATP7B, do not develop the disease. A single corrected copy per cell should therefore be enough, and not every liver cell needs to be edited for copper excretion to improve meaningfully.
This is also why the trial accepts patients with just one H1069Q copy. Many patients carry H1069Q alongside a different mutation, and correcting the H1069Q copy alone would give each edited cell one working gene.
For other populations, Prime Medicine is developing a second candidate that targets R778L, a mutation common in East Asian patients. It is still in preclinical development.
The questions ahead
The trial must show that lipid nanoparticles deliver the editor efficiently enough in people, that editing is precise with minimal unintended changes, and that copper handling actually improves. As with any permanent edit, patients will need long-term follow-up.
Safety will be watched closely. Lipid nanoparticle infusions can cause infusion reactions and temporary rises in liver enzymes, which have been seen with other liver-directed gene-editing therapies. Because adult liver cells divide slowly, edited cells are expected to last for years. That durability is the main appeal of a one-time treatment, but it also means any unintended edit would last, which is why regulators require extended monitoring for in vivo editing.
The bottom line
Prime Medicine has dosed the first patient with PM577a, a one-time prime-editing infusion designed to correct the H1069Q mutation in the liver and restore copper excretion in Wilson disease. It is a major step for in vivo prime editing, with first results expected in 2027.
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Watch on YouTube: First patient dosed: prime editing inside the body for Wilson disease
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