Arrowhead Pharma Shares Surge 18% on Positive Phase 3 Plozasiran Data

Shares of Arrowhead Pharmaceuticals Inc. (NASDAQ:ARWR) surged 18% in Wednesday trading after the company reported positive topline results from two Phase 3 studies of its drug, plozasiran. The trials evaluated the drug's efficacy in patients with severe hypertriglyceridemia (SHTG), a condition characterized by dangerously high levels of triglycerides in the blood.

Key Trial Results

Arrowhead announced that both the SHASTA-3 and SHASTA-4 studies successfully met their primary endpoint of triglyceride reduction compared to placebo. The company also stated that all key prespecified secondary endpoints were met.

Plozasiran, administered as a 25 mg subcutaneous injection every three months, demonstrated significant efficacy. According to the company's release, key outcomes at the 12-month mark included:

• SHASTA-3: A median triglyceride reduction of 79%.
• SHASTA-4: A median triglyceride reduction of 81%.
• Placebo: An approximate reduction of 27%.

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A pooled analysis across both studies also revealed a statistically significant reduction in the rate of acute pancreatitis events for patients treated with plozasiran versus placebo. Arrowhead reported that the drug had a favorable safety and tolerability profile with no new safety signals identified.

Path to Expanded Approval

Following the successful trial results, Arrowhead Pharmaceuticals plans to file a supplemental New Drug Application (sNDA) with the U.S. Food and Drug Administration (FDA). The company aims to submit the application before the end of 2026 to expand plozasiran's approved use to include SHTG.

Plozasiran is already approved under the brand name REDEMPLO in several regions, including the United States and European Union, for the treatment of adults with familial chylomicronemia syndrome (FCS). A successful label expansion into the broader SHTG market would significantly increase the drug's commercial potential. Arrowhead noted that detailed results from the studies will be presented at the European Society of Cardiology Congress in Munich on August 30, 2026.