Arrowhead (ARWR) Stock: Why It Fell 18% on Ionis's Guidance Cut

Quick answer

Arrowhead traded at $47.78 at 11:51am ET on Nov 9, 2026, down 17.8% from a $58.16 close, after Ionis cut its 2026 sales guidance for TRYNGOLZA, a rival triglyceride drug, to about $50 million from $100 million to $110 million. Ionis said the launch in severe hypertriglyceridemia (sHTG) is ramping "more gradually than expected." Arrowhead's own drug, REDEMPLO, targets the same patients, and investors read Ionis's slow start as a sign that the market could build slowly for both, International Business Times reported. Arrowhead issued no news and filed nothing on Nov 9. The stock set a low of $46.45 at 10:35am, about 20% below Friday's close.

Our view: Bullish through December 31, 2026, the date by which Arrowhead plans to file for approval of REDEMPLO in sHTG with a priority review voucher it already owns. The case against: Ionis's numbers are the first hard evidence on how fast doctors take up a new sHTG drug, and TRYNGOLZA sold only $9 million in its first quarter of sHTG selling; Arrowhead has not disclosed REDEMPLO sales; and the RSI of 24 shows the selling has momentum. The case for carries more weight. Nothing changed at Arrowhead today. REDEMPLO is not yet approved in sHTG, so Ionis's launch speaks to the market a year from now, not to Arrowhead's current sales, which come from familial chylomicronemia syndrome. REDEMPLO is dosed every three months against TRYNGOLZA's monthly shot, and its Phase 3 trials met every prespecified endpoint. Arrowhead also cut its borrowing cost on Nov 4 by swapping a 15% loan for one at SOFR plus 5.50%, and it had $1.57 billion of cash and securities at June 30, about 23% of today's market value. A drop larger than what changed at the company argues Bullish. We would move off Bullish if the sHTG filing slips into 2027, if Arrowhead's fiscal fourth-quarter report shows REDEMPLO prescriptions falling from the June quarter, or if the stock closes below its 52-week low of $37.06. This is a view on direction over that window, not a recommendation to trade the stock.

Arrowhead daily closing price from Sep 25 to Nov 9, 2026, with the Nov 4 refinancing, the Nov 6 close and the Nov 9 drop marked

Key takeaways

Arrowhead traded at $47.78 at 11:51am ET on Nov 9, 2026, down 17.8% from a $58.16 close, after Ionis cut 2026 sales guidance for TRYNGOLZA, a rival triglyceride drug, to about $50 million from $100 million to $110 million.
Arrowhead had no news or filing of its own; the fall came as investors read Ionis's slow launch in severe hypertriglyceridemia as a sign that the market for Arrowhead's REDEMPLO could build slowly too.
Arrowhead plans to file for approval of REDEMPLO in severe hypertriglyceridemia before the end of 2026, using a priority review voucher it has already bought.
On Nov 4 it replaced a 15% loan with a $400 million Sixth Street term loan at SOFR plus 5.50% due 2031, and it had $1.57 billion of cash and securities at June 30.
Our view is Bullish through December 31, 2026: nothing changed at Arrowhead today, and the drop took off about $1.5 billion of market value on another company's launch.

Table of contents

Nov 9, 2026: a sympathy drop on a rival's guidance cut
The numbers: what Arrowhead has, and what it has not shown
The bull case
The risks
What comes next

Nov 9, 2026: a sympathy drop on a rival's guidance cut

Arrowhead closed Nov 6 at $58.16, up 1.2%. Ionis released its third-quarter results and the TRYNGOLZA cut at 7am on Nov 9. Arrowhead's first premarket trade was $58.28 at 7am; it was $56.33 at 8am, fell to $51.95 at 8:20am and was $53.43 at 9:25am. The stock opened at $52.49, its high of the session came in the first minutes, and it slid to $46.45 at 10:35am. At 11:51am it was $47.78, down 17.8%, on about 3.9 million shares.

What happened:

Ionis cut the guide. TRYNGOLZA's 2026 net sales guidance fell to about $50 million from $100 million to $110 million, and third-quarter sales were $9 million. Ionis fell 27.8%, even though total revenue rose 55% to $243 million and beat estimates. Our article on why Ionis fell covers that report in full.
Arrowhead fell with it. The two drugs are the newest treatments for very high triglycerides, and REDEMPLO's next step is the same sHTG market where TRYNGOLZA is struggling.
No company news. Arrowhead's last 8-K, on Nov 4, announced the refinancing. A holder filed an amended Schedule 13G on Nov 5. Its last release, on new plozasiran data, came on Nov 7.

Arrowhead and Ionis fell alone. From the Nov 6 close to 11:51am ET:

Stock or fund	Nov 6 close	Nov 9, 11:51am	Change
Ionis (IONS)	$39.42	$28.45	-27.8%
Arrowhead (ARWR)	$58.16	$47.78	-17.8%
Alnylam (ALNY)	$155.94	$156.39	+0.3%
SPDR S&P Biotech (XBI)	$152.21	$155.80	+2.4%
iShares Biotechnology (IBB)	$213.63	$218.75	+2.4%

After the drop, RSI(14) stood at 24, the shares sat 28% below their 50-day average and 33% below their 200-day average, 50% below their 52-week high of $95.49, and volume was already 2.5 times its 20-day average with more than four hours of trading left.

The numbers: what Arrowhead has, and what it has not shown

Bar chart of Arrowhead's cash, restricted cash and securities of $1.57 billion at June 30, 2026, against its $400 million term loan and the $1.5 billion of market value lost on Nov 9

Cash. $1.57 billion of cash, restricted cash and available-for-sale securities at June 30, 2026.
Debt. A $400 million senior secured term loan from funds managed by Sixth Street, at three-month SOFR plus 5.50%, due Nov 2, 2031, with no scheduled amortization. The loan it replaced charged 15% a year and required at least twice the invested capital back if repaid by August 2028; Arrowhead prepaid it at a $68 million discount to that minimum.
Last quarter. Fiscal third-quarter revenue was $75.3 million and the net loss was $194.3 million, or $1.36 a share. REDEMPLO prescription volume roughly doubled in the quarter, and more than 400 practitioners had prescribed it. Arrowhead did not disclose REDEMPLO sales.
Next report. The average estimate for the fiscal fourth quarter is a $1.52 loss a share on $61.2 million of revenue.

The cut at Ionis is a guidance change at another company, and the drop here is a read-across. Our explainer on base rates covers why one launch is a thin sample for judging a second drug with a different dosing schedule.

The bull case

REDEMPLO's case was never a bigger triglyceride number; it was quarterly dosing and fewer pancreatitis attacks. In the full 12-month SHASTA-3 and SHASTA-4 data, triglycerides fell 79% to 81% and acute pancreatitis 78%, International Business Times reported. A priority review voucher means an FDA decision could come within six months of filing. The refinancing removed the most expensive piece of the capital structure. The average analyst target is $101.56, about twice the price, and HC Wainwright and Chardan repeated Buy ratings on Oct 15. The stock is now 29% above its 52-week low of $37.06 while holding a drug already on the market.

The risks

The sHTG market. If Ionis is right that establishing a new treatment takes time, REDEMPLO's sHTG sales in 2027 will be slower than models assume. The FDA decision itself will not come before 2027.
No sales disclosure. Arrowhead reports prescriptions and prescribers, not REDEMPLO dollars. The next report may not settle the question.
Cash burn. A $194.3 million loss in the June quarter means the cash pile shrinks fast without partner payments.
Momentum. The Phase 3 readouts are behind it, and the next moves depend on sales, which take longer to prove.

What comes next

Arrowhead's fiscal fourth-quarter report is expected in November, and the sHTG filing before Dec 31. For the rest of the session's movers, see today's biggest stock moves.

Frequently asked questions

Why did Arrowhead stock drop today?

Arrowhead fell 17.8% to $47.78 at 11:51am ET on Nov 9 after Ionis cut its 2026 TRYNGOLZA sales guidance to about $50 million from $100 million to $110 million, saying the launch in severe hypertriglyceridemia is ramping more slowly than expected. TRYNGOLZA competes with Arrowhead's REDEMPLO. Arrowhead issued no news of its own.

What is REDEMPLO?

REDEMPLO (plozasiran) is Arrowhead's RNA interference drug that lowers triglycerides. It is approved in the U.S. for familial chylomicronemia syndrome. In the Phase 3 SHASTA-3 and SHASTA-4 trials in severe hypertriglyceridemia it met its primary endpoint and all prespecified secondary endpoints, and full 12-month data showed triglycerides cut by 79% to 81% and acute pancreatitis by 78%, International Business Times reported.

How is REDEMPLO different from TRYNGOLZA?

REDEMPLO is dosed once every three months, while TRYNGOLZA is dosed monthly, and Arrowhead pitches its safety profile as an advantage. Any comparison of the two drugs' efficacy is across separate trials.

When will Arrowhead file for sHTG approval?

Arrowhead said in August that it expects to submit a supplemental new drug application for plozasiran in severe hypertriglyceridemia before the end of 2026, and that it has acquired a priority review voucher for it. Priority review targets an FDA decision within six months of filing, against ten months under standard review.

How much cash does Arrowhead have?

Arrowhead had $1.57 billion of cash, restricted cash and securities at June 30, 2026. On Nov 4 it replaced a $400 million facility that charged 15% a year with a $400 million Sixth Street term loan at three-month SOFR plus 5.50%, due Nov 2, 2031, and repaid the old loan at a $68 million discount to the minimum it owed.

When does Arrowhead report earnings?

Arrowhead's fiscal year ends Sep 30. Analysts' calendars put its fiscal fourth-quarter report around Nov 12, 2026, with an average estimate of a $1.52 loss a share on $61.2 million of revenue, but the company had not confirmed a date as of Nov 9.

Sources

Article details

By James Whitfield, Head of Equity Research, Dombey Capital

Published November 9, 2026 · 5 min read · Event-Driven Investing