Arrowhead Pharmaceuticals Completes Enrollment in SHASTA-3, SHASTA-4, and MUIR-3 Phase 3 Studies of Plozasiran

Business Wire

17 hours ago

PASADENA, Calif.--(BUSINESS WIRE)--Arrowhead Pharmaceuticals, Inc. (NASDAQ: ARWR) today announced that it has completed enrollment in SHASTA-3, SHASTA-4, and MUIR-3, the company's global Phase 3 clinical studies designed to support regulatory submissions for marketing approval of investigational plozasiran in the treatment of severe hypertriglyceridemia. Arrowhead anticipates completing the primary portion of these studies in mid-2026 with topline data expected shortly thereafter and planned submissions for regulatory review and potential approval to follow. The company previously submitted a New Drug Application (NDA) for plozasiran based on positive Phase 3 PALISADE study results in patients with familial chylomicronemia syndrome, which the U.S. FDA has accepted with a Prescription Drug User Fee Act (PDUFA) action date set for November 18, 2025.
Arrowhead anticipates completing the primary portion of these studies in mid-2026 with topline data expected shortly thereafter and planned submissions for regulatory review and potential approval to follow.
'Completion of enrollment for the SHASTA-3, SHASTA-4, and MUIR-3 studies represent important milestones for plozasiran,' said Bruce Given, M.D., Chief Medical Scientist at Arrowhead. 'These studies bring us closer to generating the datasets needed to support potential global regulatory submissions for plozasiran as a treatment for severe hypertriglyceridemia, pending positive results. With a primary endpoint focused on triglyceride reduction at 12 months, we remain on track for study completion by mid-2026. Arrowhead's clinical development, clinical operations, and regulatory teams continue to execute complex global clinical studies with speed and precision. We owe the entire team involved a debt of gratitude for efficiently initiating these studies in 24 countries and enrolling approximately 2,200 patients. We're grateful to the investigators, caregivers, and patients for participating in these clinical studies, and we thank them for their trust in Arrowhead and in plozasiran.'
About Severe Hypertriglyceridemia
Severe hypertriglyceridemia (SHTG) is characterized by triglyceride (TG) levels greater than 500 mg/dL, with the most severe form being familial chylomicronemia syndrome (FCS) where TGs typically exceed 880 mg/dL. SHTG significantly increases the risk of acute pancreatitis (AP), which can often include recurrent attacks requiring repeat hospital admissions and worsening outcomes. AP risk is proportional to the number, characteristics, and concentration of triglyceride rich lipoproteins (TRLs), particularly chylomicrons, and increases as TGs rise. Elevated TGs can also increase the risk of atherosclerotic cardiovascular disease (ASCVD). Limited treatment options exist to sustainably reduce TGs below guideline directed risk thresholds.
About SHASTA-3 and SHASTA-4 Phase 3 Studies
SHASTA-3 (NCT06347003) and SHASTA-4 (NCT06347016) are double-blind, placebo-controlled, Phase 3 studies to evaluate the efficacy and safety of plozasiran in adults with severe hypertriglyceridemia. Between the two studies, approximately 750 participants were randomized to receive 4 doses (once every 3 months) of 25 mg plozasiran or placebo. The primary endpoint is percent change in fasting serum triglyceride levels from baseline to month 12 compared to placebo. After month 12, eligible participants will be offered an opportunity to continue in an optional open-label extension.
About MUIR-3 Phase 3 Study
MUIR-3 (NCT06347133) is a double-blind, placebo-controlled, Phase 3 study to evaluate the efficacy and safety of plozasiran in adults with hypertriglyceridemia (TGs greater than 150 mg/dL and less than 500 mg/dL). Approximately 1,450 participants were randomized to receive 4 doses (once every 3 months) of 25 mg plozasiran or placebo. The primary endpoint is percent change in fasting serum triglyceride levels from baseline to month 12 compared to placebo.
About Plozasiran
Plozasiran, previously called ARO-APOC3, is a first-in-class investigational RNA interference (RNAi) therapeutic designed to reduce production of apolipoprotein C-III (APOC3) which is a component of triglyceride rich lipoproteins (TRLs) and a key regulator of triglyceride metabolism. APOC3 increases triglyceride levels in the blood by inhibiting breakdown of TRLs by lipoprotein lipase and uptake of TRL remnants by receptors in the liver. The goal of treatment with plozasiran is to reduce the level of APOC3, thereby reducing triglycerides and restoring lipids to more normal levels.
In multiple clinical studies, investigational plozasiran has demonstrated reductions in triglycerides and multiple atherogenic lipoproteins in patients with familial chylomicronemia syndrome (FCS), severe hypertriglyceridemia (SHTG), and mixed hyperlipidemia. Plozasiran has been generally well tolerated to date with treatment emergent adverse events reported that generally reflect the comorbidities and underlying conditions of the study populations. Across clinical studies and study populations, the most frequently reported treatment emergent adverse events for the 25 mg dose that is proposed for marketing approval were COVID-19, upper respiratory tract infection, headache, Type 2 diabetes mellitus, and abdominal pain.
Plozasiran is being investigated in the SUMMIT program of clinical studies, including the PALISADE Phase 3 study in patients with FCS, the SHASTA studies in patients with SHTG, and the MUIR studies in patients with mixed hyperlipidemia.
Plozasiran in the treatment of patients with FCS has been granted Breakthrough Therapy Designation, Orphan Drug Designation, and Fast Track Designation by the U.S. Food and Drug Administration and Orphan Medicinal Product Designation by the European Medicines Agency. Investigational plozasiran has been submitted for marketing authorization in treatment of FCS to multiple global regulatory authorities but has not been reviewed or approved to treat any disease.
About Arrowhead Pharmaceuticals, Inc.
Arrowhead Pharmaceuticals, Inc. develops medicines that treat intractable diseases by silencing the genes that cause them. Using a broad portfolio of RNA chemistries and efficient modes of delivery, Arrowhead therapies trigger the RNA interference mechanism to induce rapid, deep, and durable knockdown of target genes. RNA interference, or RNAi, is a mechanism present in living cells that inhibits the expression of a specific gene, thereby affecting the production of a specific protein. Arrowhead's RNAi-based therapeutics leverage this natural pathway of gene silencing.
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Source: Arrowhead Pharmaceuticals, Inc.