Ionis Pharmaceuticals Inc. (IONS) is having one of those Mondays. The stock is trading at a 52-week low after the company cut its 2026 product sales guidance for Tryngolza (olezarsen) roughly in half.

The Guidance Cut That Started It All

Tryngolza, the cholesterol-lowering drug, brought in U.S. net product sales of $9 million in the third quarter. That's the number investors got. What they also got was a forecast reset: Ionis now expects 2026 Tryngolza sales of approximately $50 million, down from a prior range of $100 million-$110 million.

The reason? The severe hypertriglyceridemia (sHTG) launch is moving more gradually than expected. According to the company, this reflects the early dynamics of establishing a new treatment paradigm. In plain English: doctors and payers need time to adopt a novel approach, and that time is showing up in the sales line.

Q3 Results Actually Beat the Street

Here's the twist. The quarter itself wasn't bad. Ionis reported a third-quarter adjusted loss of 40 cents per share, comfortably better than the consensus loss of $1.21. Sales jumped 55% year over year to $243 million, blowing past the Wall Street consensus of $182.12 million.

The company also affirmed its 2026 total sales guidance of $875 million-$900 million. That's below the analysts' estimate of $916.396 million, but not by a mile. Ionis still plans to achieve positive cash flow by 2029, contingent on Tryngolza's uptake and pipeline successes.

Leadership Pushes Back on the Panic

On the earnings call, management made the case that Tryngolza's multibillion-dollar peak sales potential is intact. The strategic initiatives are focused on broadening the prescriber base, increasing prescribing depth, and improving payer access.

CEO Brett Monia told investors that as the first and only treatment approved to reduce triglycerides and the risk of acute pancreatitis in people living with sHTG, Tryngolza requires health care professionals to adopt a new approach to patient care. That, he noted, takes time in these early days.

"While initial sales progress has been more gradual than anticipated, we are encouraged by the underlying launch fundamentals. Importantly, we have identified clear opportunities to improve performance, and we remain confident in TRYNGOLZA's long-term growth potential," Monia said in a press release on Monday.

Monia also said the company remains confident in Tryngolza's potential to achieve more than $3 billion in peak annual sales. That's a big number, and it's the kind of promise that gets tested when guidance gets halved.

Dawnzera Keeps Chugging Along

Not everything is slowing down. Dawnzera (donidalorsen), the first and only RNA-targeted prophylactic therapy for hereditary angioedema (HAE) in patients 12 years of age and older, generated sales of $37 million. The company is on track to hit its full-year 2026 Dawnzera sales guidance of $110-120 million.

So the portfolio isn't a one-trick pony. But Tryngolza is the growth story investors were counting on, and the market is repricing that story in real time.

Price Action

Ionis Pharmaceuticals shares were down 24.25% at $29.867 at the time of publication on Monday. The stock is trading at a new 52-week low, according to market data.