By Julie Steenhuysen

CHICAGO, Nov 8 (Reuters) - A single infusion of CRISPR Therapeutics' CRSP.BN experimental gene therapy was safe and reduced levels of harmful LDL cholesterol and triglycerides by half in four people taking the highest dose, raising hope for a one-time treatment.

"We've never had anything that could lower both LDL and triglycerides by around 50%," said Cleveland Clinic cardiologist Dr. Steven Nissen, lead researcher of the first-in-human study of the therapy.

Although still very early in development, if future trials prove the treatment, CTX310, to be safe and effective, it could be practice-changing, said Cleveland Clinic's Dr. Luke Laffin, the study's co-leader.

「Rather than a once-daily pill or monthly injection, this therapy would potentially offer a one-time infusion that is safe and durable for patients with high cholesterol,」 he said.

Results were presented on Saturday at the American Heart Association meeting in New Orleans and published in the New England Journal of Medicine.

High LDL, the so-called "bad" cholesterol, can cause plaques to build up in artery walls, raising the risk of a heart attack or stroke. High triglycerides, another blood fat, can also increase those risks.

SWITCHING OFF A GENE

CTX310 works by switching off a gene called ANGPTL3 through a single, two-hour infusion. It was inspired by studies showing people born with an inactive version of the ANGPTL3 gene have a lower lifetime risk of heart disease with no apparent adverse consequences.

Regeneron's REGN.O Evkeeza, which treats a rare genetic disorder called homozygous familial hypercholesterolemia, targets the same gene but requires monthly infusions.

CRISPR's trial of 15 patients aged 31-68, conducted in Australia, New Zealand and the UK, tested five different doses. All participants had high triglycerides, high LDL cholesterol or both and had failed to respond to other treatments.

Among four patients who received the highest dose, triglycerides on average were cut by 55% and LDL by 50% two weeks after treatment. Levels stayed low for at least two months.

"We're going to try to demonstrate the safety and efficacy of these one and done therapies because we think these options are important for patients," Nissen said.

Three participants had temporary reactions to the therapy, including nausea and elevated liver enzymes that resolved quickly, Laffin said.

Participants will be monitored for a year following the trial, with the option of an additional 15 years of follow-up.

TARGETING COMMON DISEASES

"I think we're just beginning to uncover the power of gene editing in common diseases," Switzerland-based CRISPR Therapeutics chief Sam Kulkarni said in an interview, noting that most gene therapies have been tried in rare diseases.

The company plans to take its data to U.S. regulators with the aim of starting phase 2 studies in 2026. CEO Kulkarni said he hoped to have a product on the market in the next four or five years.

The company would first target people with genetics-related high cholesterol, though eventually it could be an option for tens of millions of Americans, if approved.

CRISPR and Vertex VRTX.O already market the gene therapy Casgevy for sickle-cell disease. Unlike the nearly $2 million sickle cell therapy that involves a year-long process in which the patient's cells are collected and genetically altered, the cholesterol treatment would be a simple infusion.

"We don't know what the cost of this therapy is going to be ultimately, but it's very likely to be less than $100,000," Kulkarni said.

(Reporting by Julie SteenhuysenEditing by Bill Berkrot)

((julie.steenhuysen@thomsonreuters.com; 312-408-8131; Reuters Messaging: Julie.steenhuysen.reuters.com@reuters.net))