Dive Insight:

When Regeneron developed Praluent, its goal was to treat broad numbers of heart-disease patients who couldn’t get their cholesterol levels in check with commonly prescribed pills like Pfizer’s Lipitor.

That plan was complicated by insurers, who made drug access difficult because of Praluent’s high price. And Regeneron also had a rival drug from Amgen, called Repatha, to compete against. The two have battled both commercially and in court for years, and the legal war is still ongoing: Regeneron won a key court decision related to patent litigation on Thursday.

With Evkeeza, Regeneron has applied a different strategy. The drug is for small numbers of severely ill patients with an ultra-rare disease.

In homozygous familial hypercholesterolemia, or HoFH, patients have two copies of a gene that causes elevated LDL. The condition, affecting about 1,300 people in the U.S., leads to early onset of dangerous blood vessel blockages and severely high cholesterol levels that can’t be easily controlled with other drugs.

One drug, Amryt’s Juxtapid, won FDA approval in 2012 because it could lower LDL by a median of 50% in HoFH patients. That drug can cause spikes in liver enzymes, however, a worrisome side effect and a sign of potential liver damage. Amryt reported sales of $68 million in 2016.

HoFH patients can also get apheresis, a process that involves filtering the LDL out of the bloodstream. That procedure was calculated to cost nearly $230,000 a year for patients needing weekly treatment in 2015.

Though pricier than other treatments, Regeneron’s drug appears to help HoFH patients lower cholesterol even when added on to other therapies. The clinical trial supporting Evkeeza’s approval, called ELIPSE-HoFH, enrolled 65 patients with a mean LDL levels of 255 milligrams per deciliter — more than double what are considered healthy levels. After 24 weeks of a once-monthly Evkeeza infusion alongside other therapies including Praluent and apheresis, patients saw their LDL levels drop an average of 47%.

Patients given a placebo, by comparison, had a mean LDL increase of 2%.

The high-priced drug is being tested for other conditions, including the more common heterozygous form of inherited disease — which affects one in 250 people — and non-inherited high LDL that hasn’t responded to drug therapy. A Phase 2 trial of people with inherited and non-inherited disease who had uncontrolled LDL despite treatment with other drugs found that Evkeeza could lower LDL by up to 56% when compared to placebo.

Evkeeza might not be alone for long, however. Ionis Pharmaceuticals is developing an RNA-based drug called vupanorsen targeting ANGPTL3. That treatment is currently in Phase 2 testing.