Intellia Therapeutics Says a Patient Died in Gene Editing Trial

Intellia disclosed late last month that the patient, a man in his early 80s with heart disease, had been hospitalized due to liver problems weeks after being dosed with nex-z. (Dreamstime)

The biotech Intellia Therapeutics said late Thursday that a patient had died in a trial of the company’s experimental gene editing treatment, called nex-z.

Intellia had disclosed late last month that the patient, a man in his early 80s with a heart disease called ATTR-cardiomyopathy, had been hospitalized due to liver problems weeks after being dosed with nex-z.

The company paused dosing and screening patients in the trial in which the patient had been enrolled, and in a related trial that tested nex-z in a similar condition.

The company said late Thursday that the patient had died on Wednesday night. Intellia shares were down 20.6% on Friday.

“We were very saddened to learn that the patient passed away last night,” Intellia CEO John Leonard said on a Thursday investor call. “We have been advised by the treating physician that this is a case with complicating comorbidities, and the case is being further evaluated.”

Nex-z is the most closely watched drug in Intellia’s development pipeline. The company had said as recently as late September that it planned to submit the drug for Food and Drug Administration approval in 2028, and last month FactSet consensus estimates had nex-z sales hitting $2.5 billion in 2030. That figure has now plummeted to $990 million.

On Thursday and Friday, analysts said that the patient death would at the very least complicate the future for the nex-z program.

“While foremost a tragedy for the patient and family, this announcement continues the run of negative news for nex-z, and we are not surprised by shares down ~20% after hours in reaction,” Leerink Partners analyst Mani Foroohar wrote in a late Thursday note.

Nex-z is a gene-editing treatment that uses an approach called Crispr/Cas9 to knock out a gene in the liver that codes for the production of a protein called transthyretin. The treatment is being tested in ATTR-cardiomyopathy and ATTR-polyneuropathy, two separate conditions in which transthyretin plays a role.

Intellia says it is still committed to nex-z, and that it is also continuing development of another gene editing treatment, called lonzo-v, which is being studied in a separate Phase 3 trial.

While lonvo-z uses the same lipid nanoparticle wrapper as nex-z, it targets a different gene. Lonzo-v is being tested as a treatment for a genetic condition called hereditary angioedema. The company said that it hopes to launch lonvo-z in early 2027.

Intellia said that the patient who died had been dosed with nex-z on Sept. 30. He was admitted to the hospital on Oct. 24 after tests showed liver problems. The Food and Drug Administration told Intellia late last month that it was putting what is called a clinical hold on both of the nex-z trials, stopping the studies, though the company hasn’t yet received a formal notification of the clinical holds.

Resuming the studies could pose challenges, and will likely depend on what doctors determine was the ultimate cause of the patient’s death. On the late Thursday investor call, Leonard made clear that the company still believes in nex-z. He said that nearly 700 patients have been enrolled in the two Phase 3 trials thus far, and seriously elevated levels of liver enzymes have been seen “in less than 1% of all patients.”

In response to investor questions, Leonard declined to discuss the patient’s comorbidities, but said he had a “very complicated medical course.”

Write to Josh Nathan-Kazis at josh.nathan-kazis@barrons.com