Ionis Pharmaceuticals Stock Slides 39% Over 9 Straight Down Days
A persistent selloff in a biotech name prompts a closer look at the underlying business fundamentals.
Ionis Pharmaceuticals (IONS) stock has now moved lower for 9 consecutive trading days, a cumulative loss of 38.7%. The decline has erased about $5.5 billion from the company’s market value, which now stands at about $8.7 billion.
Ionis Pharmaceuticals, Inc. discovers and develops RNA-targeted therapeutics in the United States.
How The Streak Stacks Up Against The S&P 500
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 | -2.6% | -0.2% |
| 9D (Current Streak) | -38.7% | -0.8% |
| 1M (21D) | -28.7% | 0.3% |
| 3M (63D) | -30.1% | 4.5% |
| YTD 2026 | -33.1% | 8.7% |
| 2025 | 126.3% | 16.4% |
| 2024 | -30.9% | 23.3% |
| 2023 | 33.9% | 24.2% |
What do the fundamentals suggest?
The data points to real strain beneath the surface. While recent revenue growth of 47.5% is strong, the company’s operating margin over the last twelve months is -33.3%, a sharp contrast to the S&P 500 median of 18.4%. IONS also has negative trailing earnings.
This move appears specific to the company, not the broader market. Over the same 9 trading days, the S&P 500 returned -0.8%. While 42 S&P 500 stocks are on losing streaks of 3 days or more, the magnitude of this particular decline stands out.
A streak is a question, not an answer.
A long streak is a signal of persistent momentum and focused market attention. It is not, by itself, an instruction to buy or sell.
The disciplined response is to use the new information as a prompt. It is a reason to check the business realities against the stock’s price, a process the fundamental numbers here allow an investor to begin.
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.