• If you are considering whether Ionis Pharmaceuticals at around US$76.82 represents fair value or a stretched price, this article outlines what the current valuation indicators might be suggesting.
• The stock has returned 2.5% over the last 7 days and 6.2% over the last 30 days. Its 1 year return of 171.0% and 3 year return of 109.1% contrast with a year-to-date return showing a 3.6% decline.
• Recent attention on Ionis has been supported by ongoing coverage of its pipeline and commercial prospects, which has kept the stock on the radar of many biotech-focused investors. This backdrop provides useful context for considering whether the recent 1 year return of 171.0% aligns with the business fundamentals or reflects a shift in sentiment and risk appetite.
• On Simply Wall St's valuation checks, Ionis scores 2 out of 6. The next sections will discuss what different valuation approaches indicate about the stock today and then conclude with a way to combine those methods into a more complete view of value.

Ionis Pharmaceuticals scores just 2/6 on our valuation checks. See what other red flags we found in the full valuation breakdown.

Approach 1: Ionis Pharmaceuticals Discounted Cash Flow (DCF) Analysis

A Discounted Cash Flow, or DCF, model estimates what a company could be worth by projecting its future cash flows and discounting them back into today’s dollars. For Ionis Pharmaceuticals, this is done using a 2 Stage Free Cash Flow to Equity model that relies on analyst forecasts for the early years and then extends those trends further out.

Ionis currently has last twelve month free cash flow of about $321.0 million in outflows. Analyst and model projections show free cash flow of $650.7 million in outflows in 2026, $292.4 million in outflows in 2027 and then moving into positive territory, reaching $69.7 million in 2028, $403.7 million in 2029 and $854.3 million in 2030, all in $. Beyond 2030, Simply Wall St extrapolates further increases in projected free cash flow up to 2035.

Discounting all of these projected cash flows back to today produces an estimated intrinsic value of about $247.52 per share. Compared with the recent share price of around $76.82, the DCF output implies the stock is about 69.0% undervalued on this model.

Result: UNDERVALUED

Our Discounted Cash Flow (DCF) analysis suggests Ionis Pharmaceuticals is undervalued by 69.0%. Track this in your watchlist or portfolio, or discover 60 more high quality undervalued stocks.

Approach 2: Ionis Pharmaceuticals Price vs Sales

For companies where profits are limited or volatile, the P/S ratio is often a useful yardstick because it compares what you are paying for each dollar of revenue, rather than each dollar of earnings. Investors typically look for a P/S level that lines up with expectations for revenue growth and the risk of that revenue stream.

Higher expected growth or lower perceived risk can justify a higher P/S multiple, while slower growth or higher uncertainty usually point to a lower, more cautious multiple. Ionis currently trades on a P/S of 13.45x. This is above the Biotechs industry average of 11.82x and also above the peer average of 4.16x.

Simply Wall St’s Fair Ratio for Ionis, at 4.81x, is a proprietary estimate of what the P/S might be based on factors such as earnings growth, industry, profit margins, market cap and risk. This tailored view can be more informative than a simple industry or peer comparison because it adjusts for the company’s specific profile rather than treating all Biotechs as similar. Comparing the Fair Ratio of 4.81x with the current P/S of 13.45x indicates that the shares are pricing in a higher multiple than this framework supports.

Result: OVERVALUED

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Upgrade Your Decision Making: Choose your Ionis Pharmaceuticals Narrative

Earlier it was mentioned that there is an even better way to understand valuation. Narratives on Simply Wall St let you connect your own story about Ionis Pharmaceuticals to specific forecasts for revenue, earnings and margins, then translate that into a Fair Value that you can compare to the current price to decide whether the stock looks attractive or stretched. For example, a more bullish view might tie a US$120 Fair Value to assumptions of US$2.9b revenue, US$640.8m earnings and a 42.9x P/E around 2029. More cautious views might be anchored closer to US$93.90 or US$62.78. All of these narratives update automatically when new news or earnings arrive, so you can see in one place how different perspectives inside the Community page turn the same information into very different price expectations.

For Ionis Pharmaceuticals, here are previews of two leading Ionis Pharmaceuticals Narratives:

Fair value in this bullish narrative: US$120.00 per share.

At the recent price of US$76.82, this implies the shares are about 36.8% below that narrative fair value on this framework.

Revenue growth assumption in this view: 45.0% a year.

• Expects a ramp up in revenue and margins as therapies such as TRYNGOLZA and Donidalorsen build on existing launches and a wider late stage pipeline.
• Assumes Ionis can translate its antisense platform and an aging population into higher pricing power, better profitability and stronger cash generation over time.
• Anchors to a fair value of US$120, which relies on analysts expecting Ionis to reach US$2.9b of revenue and US$640.8m of earnings around 2029 on a 42.9x P/E multiple.

Fair value in this more cautious narrative: about US$62.78 per share.

At the recent price of US$76.82, this implies the shares are about 22.4% above that narrative fair value on this framework.

Revenue growth assumption in this view: 13.8% a year.

• Focuses on pricing pressure as Ionis moves from smaller orphan indications into broader populations, alongside tighter payer scrutiny in the U.S. and Europe.
• Highlights the risk that higher R&D and commercial spending, competitive pressure and reliance on key partnerships could keep earnings and cash flow volatile.
• Uses a fair value of about US$62.78, which reflects updated assumptions for revenue growth, profit margins and a higher required return after recent Q4 results and 2026 catalyst updates.

Seen together, these narratives bracket a wide range of possible outcomes for Ionis Pharmaceuticals, from a US$120 upside case to a US$62.78 downside case, and both are built off specific assumptions about revenue, margins, regulatory events and valuation multiples that you can test against your own expectations.

Do you think there's more to the story for Ionis Pharmaceuticals? Head over to our Community to see what others are saying!

This article by Simply Wall St is general in nature. We provide commentary based on historical data and analyst forecasts only using an unbiased methodology and our articles are not intended to be financial advice. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. We aim to bring you long-term focused analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material. Simply Wall St has no position in any stocks mentioned.