We can readily understand why investors are attracted to unprofitable companies. For example, although Amazon.com made losses for many years after listing, if you had bought and held the shares since 1999, you would have made a fortune. But while history lauds those rare successes, those that fail are often forgotten; who remembers Pets.com?

So should Prothena (NASDAQ:PRTA) shareholders be worried about its cash burn? In this article, we define cash burn as its annual (negative) free cash flow, which is the amount of money a company spends each year to fund its growth. First, we'll determine its cash runway by comparing its cash burn with its cash reserves.

How Long Is Prothena's Cash Runway?

A cash runway is defined as the length of time it would take a company to run out of money if it kept spending at its current rate of cash burn. As at June 2024, Prothena had cash of US$564m and no debt. Looking at the last year, the company burnt through US$101m. That means it had a cash runway of about 5.6 years as of June 2024. Importantly, though, analysts think that Prothena will reach cashflow breakeven before then. If that happens, then the length of its cash runway, today, would become a moot point. Depicted below, you can see how its cash holdings have changed over time.

How Well Is Prothena Growing?

We reckon the fact that Prothena managed to shrink its cash burn by 22% over the last year is rather encouraging. But it was the operating revenue growth of 277% that really shone. We think it is growing rather well, upon reflection. While the past is always worth studying, it is the future that matters most of all. So you might want to take a peek at how much the company is expected to grow in the next few years.

How Easily Can Prothena Raise Cash?

There's no doubt Prothena seems to be in a fairly good position, when it comes to managing its cash burn, but even if it's only hypothetical, it's always worth asking how easily it could raise more money to fund growth. Companies can raise capital through either debt or equity. Many companies end up issuing new shares to fund future growth. By comparing a company's annual cash burn to its total market capitalisation, we can estimate roughly how many shares it would have to issue in order to run the company for another year (at the same burn rate).

Prothena's cash burn of US$101m is about 8.8% of its US$1.1b market capitalisation. That's a low proportion, so we figure the company would be able to raise more cash to fund growth, with a little dilution, or even to simply borrow some money.

So, Should We Worry About Prothena's Cash Burn?

As you can probably tell by now, we're not too worried about Prothena's cash burn. In particular, we think its revenue growth stands out as evidence that the company is well on top of its spending. And even though its cash burn reduction wasn't quite as impressive, it was still a positive. Shareholders can take heart from the fact that analysts are forecasting it will reach breakeven. Looking at all the measures in this article, together, we're not worried about its rate of cash burn; the company seems well on top of its medium-term spending needs. Its important for readers to be cognizant of the risks that can affect the company's operations, and we've picked out 1 warning sign for Prothena that investors should know when investing in the stock.

Of course Prothena may not be the best stock to buy. So you may wish to see this free collection of companies boasting high return on equity, or this list of stocks with high insider ownership.

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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.