beginner8 min read

Understanding Cash Runway in Biotech Stocks

Reviewed by Blane Jackson, DDS, MBA. Educational guide only. See the editorial policy and disclosures.

Imagine a biotech company that has a promising drug in clinical trials but no revenue. How does it pay for research, salaries, and lab space? It burns through cash. The amount of time a company can survive before running out of money is called its 'cash runway.' For biotech investors, cash runway is a critical metric because it directly impacts dilution risk—the chance that your shares get diluted when the company raises more money. In this guide, you'll learn how to calculate cash runway, why it matters more than revenue for pre-commercial biotechs, and how to use it to predict potential dilution. We'll walk through real examples and give you actionable steps to evaluate any biotech stock.

What Is Cash Runway and Why Does It Matter?

Cash runway is the number of months a company can continue operating before it runs out of cash, assuming no additional income or funding. For biotech companies that have no approved products, revenue is often zero or minimal. Instead, they rely on cash reserves from investors to fund expensive clinical trials and operations. If a company runs out of cash, it may be forced to raise money at unfavorable terms, sell assets, or even go bankrupt. Cash runway is a measure of financial health and a predictor of future dilution. A longer runway gives management time to reach milestones that can increase the company's value, while a short runway often leads to desperate fundraising that hurts existing shareholders.

Key takeaway

Cash runway tells you how long a biotech can survive without new funding, and it's a key indicator of dilution risk.

Example

Consider a small biotech with $50 million in cash and an annual burn rate of $30 million. Its cash runway is about 20 months ($50M / $30M * 12). If it needs to complete a Phase 3 trial that takes 24 months, it will likely need to raise money before the trial ends.

How to Calculate Cash Runway

To calculate cash runway, you need two numbers: cash on hand and monthly cash burn rate. Cash on hand is typically found on the balance sheet as 'cash and cash equivalents' plus 'marketable securities' if they are liquid. Monthly burn rate is the net cash used in operating and investing activities per month, usually derived from the cash flow statement. A simple formula: Cash Runway (months) = Cash on Hand / Monthly Burn Rate. For example, if a company has $100 million in cash and burns $10 million per month, its runway is 10 months. But be careful: burn rate can change. If a company is ramping up a large trial, burn rate may increase. Always use the most recent quarterly burn rate and adjust for known upcoming expenses.

Key takeaway

Cash runway = cash on hand ÷ monthly burn rate. Use the latest cash flow statement and adjust for expected changes in spending.

Example

In 2023, Sarepta Therapeutics had cash and investments of about $2.1 billion and an annual operating burn of around $1.1 billion, giving a runway of roughly 23 months. This allowed them to plan for multiple product launches and trials.

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Why Cash Runway Matters More Than Revenue for Pre-Commercial Biotechs

For biotech companies without approved products, revenue is often zero or minimal, coming from partnerships or grants. Therefore, revenue is not a meaningful measure of financial health. Instead, cash runway is the lifeline. It determines whether the company can reach critical milestones like data readouts or FDA approvals. If a company runs out of cash before achieving a milestone, it may have to raise money at a low stock price, causing significant dilution. Even if a company has some revenue from licensing deals, it may not cover the high costs of clinical trials. Investors should focus on cash runway to assess the company's ability to execute its plan and to anticipate when additional funding will be needed.

Key takeaway

For pre-commercial biotechs, cash runway is a more important financial metric than revenue because it indicates how long they can fund operations and reach value-creating milestones.

Example

Moderna had no revenue from approved products until its COVID-19 vaccine, but it had a long cash runway due to large cash reserves and strategic partnerships. This allowed it to develop multiple vaccines without desperate fundraising.

Cash Runway and Dilution Risk

When a biotech needs cash, it often issues new shares, which dilutes existing shareholders. The shorter the cash runway, the more urgent the need for capital, which can lead to lower offering prices and greater dilution. Conversely, a long runway gives the company negotiating power and time to wait for a higher stock price. Investors should monitor cash runway to anticipate potential secondary offerings. A common rule of thumb: if a company's cash runway is less than 12 months, expect a capital raise soon. But even longer runways can be at risk if the company's burn rate increases unexpectedly. Look at the company's guidance and pipeline milestones to estimate when they might need cash.

Key takeaway

A short cash runway increases the likelihood of a dilutive capital raise. Watch for runways under 12 months as a red flag.

Example

In 2021, many small biotechs with cash runways under 12 months rushed to raise capital at high valuations, but those that waited until their runway was critically short often faced severe dilution. For instance, a company with a $10 stock price might have to issue shares at $5, doubling the share count.

Real-World Examples: How Cash Runway Predicts Dilution

Let's look at two contrasting examples. In 2020, Axsome Therapeutics had a cash runway of about 12 months and a promising pipeline. They successfully raised $300 million in a public offering at a high stock price, extending their runway to over 24 months, and avoided dilution during a critical period. On the other hand, a small biotech like Inovio Pharmaceuticals faced a cash crunch in 2021 after its COVID-19 vaccine failed. With a runway of less than 6 months, they had to do a reverse stock split and raise capital at a very low price, causing massive dilution. These examples show that proactive fundraising when the runway is still healthy can minimize dilution, while reactive fundraising when the runway is short can devastate shareholders.

Key takeaway

Companies that raise capital early with a healthy runway often get better terms and less dilution than those that wait until they are desperate.

Example

Axsome's $300M raise in 2020 was done when its stock was trading around $30, whereas Inovio's raise in 2021 was at $2 per share, illustrating the impact of timing.

How to Find Cash Runway Data in SEC Filings

The most reliable source for cash runway data is the company's quarterly report (10-Q) or annual report (10-K). Look at the balance sheet for 'Cash and cash equivalents' and 'Marketable securities.' Then, find the cash flow statement to see 'Net cash used in operating activities' and 'Net cash used in investing activities.' Add these to get total cash burn. Divide by the number of months in the period (e.g., 3 for a quarter) to get monthly burn. Many companies also provide a 'Liquidity and Capital Resources' section in the MD&A where they explicitly state their cash runway. For example, a company might say, 'We believe our existing cash will fund operations into Q2 2025.' Use that as a starting point but verify with your own calculations.

Key takeaway

You can find cash runway data in the 10-Q/10-K filings, specifically in the balance sheet, cash flow statement, and MD&A section.

Example

In a 10-Q, a company might report $80 million in cash and cash equivalents and $20 million in marketable securities. The cash flow statement shows net cash used in operations of $15 million and investing of $5 million for the quarter. That's a total burn of $20 million per quarter, or about $6.7 million per month. Runway = $100M / $6.7M ≈ 15 months.

Actionable Tips for Using Cash Runway in Your Investment Decisions

When evaluating a biotech stock, always check the cash runway. If it's less than 12 months, be prepared for a potential secondary offering. Look at the company's pipeline and upcoming milestones—if a major data readout is expected before the cash runs out, the company might be able to raise money on good news. Also, consider the company's history of dilution. Some companies are serial diluters, while others are disciplined. Use cash runway as a screening tool: avoid companies with less than 6 months of runway unless you are confident in a near-term catalyst. Finally, remember that cash runway is dynamic—recalculate after each quarterly report.

Key takeaway

Incorporate cash runway into your investment checklist: check it quarterly, compare it to upcoming milestones, and be wary of runways under 12 months.

Example

If a company has a Phase 3 readout in 9 months and a cash runway of 12 months, it might be able to raise money after positive data. But if the readout is delayed, the runway could become critical.

Key terms

Cash Runway

The amount of time a company can continue to operate before it runs out of cash, typically expressed in months. It is calculated by dividing current cash reserves by the monthly cash burn rate.

Burn Rate

The rate at which a company spends its cash reserves to cover operating expenses and investments. Usually measured monthly or quarterly.

Dilution

The reduction in existing shareholders' ownership percentage caused by the issuance of new shares. This often happens when a company raises capital by selling additional stock.

Secondary Offering

A sale of additional shares by a company that has already gone public, typically to raise capital. This increases the number of shares outstanding and dilutes existing shareholders.

10-Q

A quarterly report filed by public companies with the SEC, containing unaudited financial statements and management discussion. It provides updated financial data, including cash position and burn rate.

10-K

An annual report filed with the SEC, containing audited financial statements and a comprehensive overview of the company's business and risks. It includes detailed financial data.

Next steps

Pull up the latest 10-Q or 10-K for a biotech stock you're interested in and locate 'Cash and cash equivalents' and 'Marketable securities' on the balance sheet.

Calculate the monthly burn rate by looking at the cash flow statement: add net cash used in operating and investing activities for the quarter and divide by 3.

Divide total cash by monthly burn rate to get the cash runway in months. If it's less than 12 months, note the next likely capital raise date.

Check the MD&A section for management's own statement about cash runway and compare it to your calculation.

Set a calendar reminder to recalculate cash runway after each quarterly earnings report.

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