With a fresh FDA endorsement for its drug plozasiran, California-based Arrowhead Pharmaceuticals has successfully broken through to the commercial realm.
Complicating the matter, however, is the fact that Arrowhead’s first marketed product will now compete directly with the inaugural launch from its legal foe, Ionis Pharmaceuticals.
Tuesday, the FDA signed off on plozasiran, which will be marketed under the Redemplo sobriquet, as the first small interfering RNA (siRNA) medicine to treat patients with the rare disease familial chylomicronemia syndrome (FCS).
The drug has been approved as an adjunct to diet to reduce triglycerides in adults living with the genetic disorder, which affects some 6,500 people in the U.S., Arrowhead said in a Nov. 18 press release.
People with FCS have triglyceride levels that can be “10 to 100 times higher than normal,” Arrowhead explained. In turn, patients with the disease are at substantially higher risk of developing acute, recurrent and potentially fatal pancreatitis, the company said.
Redemplo is delivered as a subcutaneous injection just once every three months and can be administered at home, according to Arrowhead. The company said it plans to make the medication available in the U.S. “before the end of the year” and will offer a patient assistance program known as Rely on Redemplo.
“The FDA approval of Redemplo is a transformational milestone for Arrowhead,” CEO Christopher Anzalone, Ph.D., said in a statement. “This approval, and subsequent launch, marks the beginning of a new chapter in our journey—one rooted in our unwavering commitment to delivering life-changing therapies to patients with serious diseases.”
The U.S. green light also validates the approach Arrowhead has taken to siRNA delivery with its targeted RNAi Molecule (TRiM) platform, Anzalone added.
The FDA signed off on Redemplo after reviewing data from Arrowhead’s late-stage Palisade study, which met both its primary endpoint and all multiplicity-controlled key secondary endpoints, according to the company.
Crucially, a 25-mg dose of Redemplo helped patients chart a median 80% reduction in triglycerides from baseline, compared to a reduction of just 17% in patients on placebo. Arrowhead’s drug also led to a lower numerical incidence of acute pancreatitis in the trial versus the control cohort.
Redemplo won’t be heading into uncharted commercial waters, thanks to last year’s approval of Ionis’ RNA-targeted ligand conjugated antisense drug Tryngolza (olezarsen), which marked the first approval of a medicine specifically for FCS in the U.S.
Notably, Tryngolza also marks the first Ionis approval the company is launching itself in its more than 35-year history. Traditionally, Ionis had licensed out the rights to its many greenlighted drugs to development partners.
“Today, we enter a new chapter for Ionis as a fully integrated, commercial-stage biotechnology company, ready to launch our first medicine,” the company’s CEO, Brett Monia, Ph.D., said on an analyst call addressing the launch last December.
Ionis recently reported Tryngolza sales of $32 million for the third quarter. For all of 2025, the company estimates that its FCS drug will bring home sales between $85 million and $95 million.
Even before Arrowhead’s approval, the two FCS rivals were already duking it out in court.
Back in September, Arrowhead and Ionis filed dueling lawsuits against one another. Ionis alleged that Arrowhead copied its patented mRNA technology to develop Redemplo, asking a California court for an unspecified amount of monetary damages.
For its part, Arrowhead argued in its lawsuit that the Ionis patent at the heart of the dispute was “invalid and not infringed by Arrowhead’s planned commercialization” of Redemplo.
Both Arrowhead’s and Ionis’ drugs are designed to lower the body’s production of the protein APOC-3.
“Arrowhead will not tolerate efforts by Ionis to limit the availability of a potentially important new medicine to members of the FCS community,” the company’s CEO Anzalone said in a September press release addressing the lawsuit.
At the same time, an Ionis spokesperson told Fierce Biotech that it was “not seeking to block the launch of this new therapy to patients,” while stressing that the company would continue to “vigorously defend our patent position.”