Ionis Pharmaceuticals Stock Plunges 28% to Worst Day Since 2016 as Company Halves Tryngolza Sales Forecast

Shares of Ionis Pharmaceuticals Inc. plunged about 28% on Monday after the drugmaker slashed its sales forecast for Tryngolza, its triglyceride-lowering drug, overshadowing quarterly results that beat Wall Street's expectations.

Ionis shares fell $10.94, or 27.75%, to $28.48 in Monday trading, with about 6.5 million shares changing hands, roughly double the stock's three-month average. The decline cut the company's market value to about $4.7 billion.

The stock was on track for its worst single-day percentage drop since May 26, 2016, according to Dow Jones Market Data. The selloff came even as the S&P 500, Dow Jones and Nasdaq all traded higher.

Guidance cut

The Tryngolza forecast drove the selloff. Management cut its full-year 2026 Tryngolza product sales guidance by roughly 52% at the midpoint, from a prior range of $100 million to $110 million to about $50 million, citing a more gradual launch ramp than originally anticipated for the drug's severe hypertriglyceridemia indication.

Executives explained the change on the earnings call. Ionis said it was lowering guidance "to reflect the more gradual launch ramp than we had anticipated."

The cut also pushed back a key financial milestone. An analyst on the call noted the company changed its break-even guidance from 2028 to 2029.

A beat overshadowed

The quarterly numbers themselves were strong. Third-quarter revenue reached $243 million, well above the $178.2 million analysts expected. Total revenue climbed 55% year over year, and the quarterly net loss narrowed 15% to $110 million.

Ionis posted a quarterly loss of 40 cents a share, compared with the Zacks consensus estimate of a $1 loss and a 61-cent loss a year earlier.

The company stood by its overall outlook. Ionis maintained its total revenue guidance of $875 million to $900 million, expecting substantial R&D revenue to offset the reduced Tryngolza expectations, and kept its non-GAAP operating loss guidance at $425 million to $475 million.

Mixed pipeline news

The quarter also brought clinical setbacks. Ionis' presentation highlighted positive Phase 3 data for sefaxersen and ulefnersen, but also Phase 3 data misses for pelacarsen and eplontersen.

Why Tryngolza matters

Investors had been watching the launch closely. Tryngolza's commercial trajectory, in a market Ionis projects could deliver multibillion-dollar peak sales, was seen as the key test of the company's independent commercial execution capability.

Legal scrutiny

The drop drew attention from plaintiffs' firms. Kehoe Law Firm said it is investigating potential securities claims on behalf of Ionis investors following the reduced sales forecast. No lawsuit has been announced.

Analysts remain bullish

Wall Street remains largely positive. Of the 25 analysts covering the company, 22 recommend buying the stock. The stock is now down about 63% in 2026.

Investors will watch whether Tryngolza prescriptions accelerate in the coming quarters and how Ionis' late-stage pipeline progresses.