Arrowhead's plozasiran moves from rare disease toward a mass market

Arrowhead has one approved product with early sales, a large phase 3 win in a bigger disease, and a balance sheet that now carries debt as well as cash. The question for the next year is whether plozasiran can move from a rare-disease launch to a mass-market lipid drug.

The technology

Arrowhead makes RNA interference drugs. These are small pieces of RNA that tell the liver to stop producing a specific protein. Plozasiran targets APOC3, a protein that slows the clearance of triglycerides. It is given by injection under the skin every three months. As Redemplo, it is approved for familial chylomicronemia syndrome in the U.S., EU, China, Australia and Canada.

The same platform supports the rest of the pipeline: zodasiran for homozygous familial hypercholesterolemia, with the YOSEMITE phase 3 study enrolled and due to finish in mid-2027, and early obesity candidates such as ARO-INHBE. Arrowhead also licenses assets to partners. Revenue in the June quarter came mainly from Sarepta, Novartis and Madrigal.

The odds

The main readouts for plozasiran are done. SHASTA-3 and SHASTA-4 met their primary endpoints, and the full data showed a 78% reduction in acute pancreatitis events and a 4.1% absolute risk reduction. What is left is the filing and review. In the BIO/Informa/QLS study of 2011-2020 programs, 90.6% of applications filed with the FDA were approved. A voucher shortens the clock to six months.

The earlier pipeline faces the usual attrition. Across all programs the same study found 52.0% of drugs move from phase I to II and 7.9% reach approval from phase I. For rare disease programs the study found that 60.4% of phase 3 programs reach a filing and 17.0% reach approval from phase I.

The money

Total cash resources were $1.57 billion at June 30, 2026, against $782 million nine months earlier. The jump came from a January raise of $700 million in convertible notes and an equity offering, which the company put at $930 million gross. Against that, the company reports $682.7 million of net convertible notes, a $392.5 million liability tied to sold future royalties and $181.4 million drawn on a credit facility.

Net loss attributable to Arrowhead was $194.3 million in the June quarter, and the company will pay $215 million for a priority review voucher. It has not given a cash runway figure. Revenue is lumpy. It was $75.3 million in the June quarter, against $27.8 million a year earlier, and $73.7 million in the March quarter against $542.7 million the year before. Only about $2.4 million of the June figure was Redemplo, per MarketBeat's summary of the earnings call.

The risks

First, the sHTG label. The pooled analysis showed worsening glycemic control in 14.3% of patients on plozasiran against 8.7% on placebo, and three deaths occurred in the treated group, all judged unrelated by the company. How the FDA words the label will shape uptake.

Second, the launch is small. Redemplo had more than 400 prescriptions by May and about $2.4 million of quarterly revenue by June. The sHTG market is larger but will need a bigger sales effort, which costs money. Selling, general and administrative spending already rose to $47.1 million in the June quarter from $30.9 million.

Third, the company relies on partners for revenue and on financing for the rest, and the convertible notes mature in January 2032.

Our read

Plozasiran is clinically strong in two diseases, and the pancreatitis data give it a clinical argument that triglyceride numbers alone would not. The filing risk looks moderate and the commercial risk is high, because the company has to build sales from a small base while spending more each quarter. The balance sheet gives it time, but not unlimited time. The sNDA, expected before the end of 2026, is the next test.