Arrowhead Stock Tumbles 15% on Same Day Rival Ionis Cuts Tryngolza Forecast in Triglyceride Drug Market

Shares of Arrowhead Pharmaceuticals Inc. fell about 15% on Monday, sliding on the same day that rival Ionis Pharmaceuticals sharply cut its sales forecast for a competing triglyceride drug.

Arrowhead shares fell $8.95, or 15.4%, to $49.21 in Monday trading, with about 3.2 million shares traded, nearly double the average. The decline cut the company's market value to about $7 billion. The stock is still up about 46% over the past year.

Arrowhead had closed at $58.16 on Nov. 6.

Arrowhead did not issue a price-sensitive announcement explaining Monday's move.

Rival's warning

The decline came hours after Ionis reported results. Ionis plummeted about 27% Monday as the company drastically lowered its full-year revenue expectations for Tryngolza, now seeing sales of the severe hypertriglyceridemia therapy of about $50 million, down from $100 million to $110 million.

The two companies compete head-to-head. Arrowhead's plozasiran, sold as Redemplo, is positioned against Ionis' already-approved Tryngolza, with Arrowhead's differentiation resting on quarterly dosing versus Tryngolza's monthly schedule, along with its safety profile.

Analysts and investors may view Ionis' slower launch as a sign that the severe hypertriglyceridemia market could take longer to develop than expected, although no direct link to Arrowhead's decline has been confirmed.

Plozasiran's progress

Arrowhead has posted strong data for the drug. Full 12-month data from the Phase 3 SHASTA-3 and SHASTA-4 trials showed plozasiran cut pancreatitis 78% and triglycerides 79% to 81%.

The drug is already approved for a rarer condition. The FDA approved Redemplo as an adjunct to diet to reduce triglycerides in adults with familial chylomicronemia syndrome.

Recent developments

Arrowhead recently reported clinical data supporting plozasiran's durability and reduced acute pancreatitis events in severe hypertriglyceridemia, presented early results for ARO-DIMER-PA and reduced financing costs through a $400 million refinancing.

Volatile stock

The shares have swung widely. Arrowhead's 52-week high is $95.49 and its 52-week low is $37.06.

What's next

Yahoo Finance lists Arrowhead's next earnings date as Nov. 12, 2026. Investors will look for updates on Redemplo's commercial performance and the timing of its expansion into severe hypertriglyceridemia.

Analysts' average one-year price target is $107.71.