Arrowhead Pharmaceuticals (NASDAQ: ARWR) Shares Rise 19% on Thursday July 23 After Positive Phase 3 SHASTA-3 and SHASTA-4 Topline Data for Plozasiran (25 mg Subcutaneous Every Three Months) Showed 79% and 81% Median Reductions in Triglyceride Levels at 12 Months Versus Approximately 27% for Placebo in Adults With Severe Hypertriglyceridemia, With Statistically Significant Reductions in Acute Pancreatitis Events Across Both Trials; Arrowhead Plans to File a Supplemental New Drug Application With the FDA Before End of 2026
Arrowhead Pharmaceuticals (NASDAQ: ARWR) reported positive Phase 3 topline results Thursday July 23, 2026 from the SHASTA-3 and SHASTA-4 studies of plozasiran, an ApoC-III-targeting siRNA administered as a 25 mg subcutaneous injection once every three months, in adults with severe hypertriglyceridemia (sHTG). Both trials met their primary endpoint: median triglyceride reductions of 79% (SHASTA-3) and 81% (SHASTA-4) at Month 12 versus approximately 27% for placebo. All prespecified secondary endpoints were met, including a statistically significant reduction in the rate of acute pancreatitis events compared with placebo. Arrowhead shares rose approximately 19% on the readout. The company plans to file a supplemental New Drug Application (sNDA) with the US FDA before the end of 2026 for the sHTG indication (which extends the current Redemplo label from familial chylomicronemia syndrome), and Arrowhead intends to use the SHASTA-3, SHASTA-4, and MUIR-3 program data for marketing authorization filings across multiple global geographies. Plozasiran is a nucleic-acid therapeutic (siRNA), an adjacent-modality to peptides that operates through RNA interference at the ApoC-III gene expression level to lower circulating triglycerides.