Ionis Pharmaceuticals Stock Slides 36% Over 5 Straight Down Days
A multi-day slide in this biotech stock has erased billions in value, focusing attention on a disconnect between its growth and profitability.
Ionis Pharmaceuticals (IONS) stock has moved lower for 5 consecutive trading days, resulting in a cumulative loss of 36.4%. The decline has erased about $5.2 billion from the company’s market value, which now stands at about $9.1 billion.
Ionis Pharmaceuticals, Inc. discovers and develops RNA-targeted therapeutics in the United States.
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Here is how IONS stock stacks up against the S&P 500 over the streak and the periods around it:
| Return Period | IONS | S&P 500 |
|---|---|---|
| 1D | -3.2% | 0.4% |
| 5D (Current Streak) | -36.4% | 0.5% |
| 1M (21D) | -25.6% | 2.0% |
| 3M (63D) | -26.7% | 9.5% |
| YTD 2026 | -30.6% | 10.2% |
| 2025 | 126.3% | 16.4% |
| 2024 | -30.9% | 23.3% |
| 2023 | 33.9% | 24.2% |
Are the fundamentals justifying the sell-off?
While the stock’s recent move is its own story and not the market’s, with the S&P 500 returning +0.5% over the same period, the company’s financial profile is mixed. Revenue over the last twelve months grew 47.5%, far outpacing the S&P 500 median. However, profitability metrics show strain. The company’s operating margin is -33.3%, compared to an S&P 500 median of 18.4%. Its price-to-earnings multiple is -27.7.
This kind of streak is not entirely isolated in the current market. Across the S&P 500, 33 stocks are on losing streaks of 3 days or more, while 44 are on winning streaks.
A streak is information, not an instruction.
A persistent price move in one direction is a signal of focused market attention and momentum. It is not, by itself, a reason to buy or sell. The disciplined approach is to use the new information as a prompt to check the business against its price. The data here allows for that first step: weighing a company’s growth against its current profitability and valuation.
A slide like this always poses the same follow-up: which marked-down stocks are actually worth buying? Our Buy the Dip screen runs that test every day, flagging beaten-down names whose fundamentals still hold up.
Prefer the theme to this single name? Our ETF Scorecard shows how the biotech funds stack up. That way no single company’s next surprise decides the outcome.
IONS Has Fallen 52% From A Peak Before
A stock that falls day after day is a live lesson in what single name exposure feels like. IONS itself has fallen 52% from a peak within the past five years, and a fall like that lands very differently when one position carries too much of your wealth. Knowing what a repeat would do to your net worth is exactly what the Trefis Wealth team computes, with the same rules-based systematic discipline that runs our High Quality Portfolio. Request a free vulnerability audit of your biggest positions.