Arrowhead Pharmaceuticals’ Redemplo has received FDA approval for lowering triglycerides in adults with familial chylomicronemia syndrome (FCS), marking the first product approval for the Pasadena, California-based company.
Redemplo is now the first approved small interfering RNA (siRNA) therapy approved to treat patients with FCS, a rare hereditary disorder characterized by extremely high triglyceride (TG) levels.
Arrowhead will be facing off directly against Ionis Pharmaceuticals and its monthly injectable antisense oligonucleotide (ASO) therapy Tryngolza. The drug, the first to be approved for FCS, made its commercial debut in December 2024 and registered $32 million in sales in the third quarter of 2025.
Normal triglyceride levels are under ~150 mg/dL, with values over 500 mg/dL considered severely elevated. In FCS, TG levels can be 10 to 100 times higher, usually over 880 mg/dL, and even run into the thousands.
The consequences can be serious, including recurrent acute pancreatitis (which can be life-threatening), abdominal pain, fatty deposits (xanthomas), lipemia retinalis and more.
FCS is very rare, with estimates suggesting that it affects around one to 10 per 1,000,000 individuals globally. In the US, Arrowhead said approximately 6,500 people are affected by the condition.
Until now, management has focused heavily on a strict low-fat diet and triglyceride-lowering therapies, with few approved options.
Plozasiran is an siRNA therapy that targets apolipoprotein C-III (apoC-III), a protein implicated in triglyceride metabolism. Ionis’ therapy is also designed to lower the production of apoC-III.
Photo courtesy of Arrowhead Pharmaceuticals.
It was developed using Arrowhead’s proprietary Targeted RNAi Molecule (TRiM) platform.
Redemplo is formulated as a subcutaneous injection that can be self-administered at home once every three months.
Redemplo’s approval is supported by data from the pivotal Phase III Palisade trial in genetically confirmed or clinically diagnosed adult FCS patients on a low-fat diet. Arrowhead said that Redemplo is the first and only FDA-approved medicine to be studied in patients with genetically confirmed and clinically diagnosed FCS.
The primary endpoint was the percent change in fasting triglycerides from baseline to month 10.
Among the 75 patients in the study, at a dose of 25 mg, Redemplo reduced triglycerides by 80% from baseline compared to 17% in the placebo group, and led to a lower numerical incidence of acute pancreatitis.
Results from the study were presented at the European Society of Cardiology (ESC) Congress 2024 and the American Heart Association Scientific Sessions 2024 (AHA24), and were also published in The New England Journal of Medicine (NEJM) and Circulation, respectively.
“The FDA approval of Redemplo is a transformational milestone for Arrowhead. This is a proud moment for all those involved in the discovery and development process and represents new hope for the estimated 6,500 people in the US living with genetic or clinical FCS. 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,” said Christopher Anzalone, PhD, president and CEO of Arrowhead Pharmaceuticals.
“Redemplo also represents the first FDA-approval for a medicine that leverages Arrowhead’s proprietary and differentiated Targeted RNAi Molecule (TRiM) platform.”
He explained how the platform can potentially deliver siRNA to seven different cell types in the body, with the potential of silencing the expression of two genes in one molecule at the same time. “The breadth of this technology with our growing commercial capabilities dramatically expands the diseases we can potentially address and the number of lives we can change,” he said.
Related: Tryngolza (Olezarsen) Becomes First FDA-Approved Drug for Familial Chylomicronemia Syndrome
According to Reuters, in a conference call with analysts, Anzalone said Redemplo’s annual wholesale cost would be $60,000.
“We think Arrowhead’s drug will capture a larger market share,” B. Riley Securities analyst Madison El-Saadi said ahead of the decision. He also noted that Redemplo has a better profile compared to Tryngolza.
Analysts are predicting the therapy to earn around $1.4 billion by 2031, according to data from LSEG.
Arrowhead and Ionis were already dueling it out legally before Redemplo’s approval.
In September, both Ionis and Arrowhead Pharmaceuticals filed lawsuits against each other. Ionis sued Arrowhead for patent infringement, claiming Arrowhead copied its mRNA technology to develop plozasiran.
In response, Arrowhead filed a preemptive lawsuit seeking a judgment that Ionis’ patent is invalid and that its plozasiran does not infringe.
Ionis is asking a California court for an unspecified amount of monetary damages.
“Arrowhead will not tolerate efforts by Ionis to limit the availability of a potentially important new medicine to members of the FCS community,” Anzalone said in a press release regarding the lawsuit.
According to Fierce Biotech, an Ionis spokesperson said that it was “not seeking to block the launch of this new therapy to patients,” but maintained that it would continue to “vigorously defend our patent position.”
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