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. Having said that, unprofitable companies are risky because they could potentially burn through all their cash and become distressed.

So, the natural question for (NASDAQ:AURA) shareholders is whether they should be concerned by its rate of cash burn. In this report, we will consider the company's annual negative free cash flow, henceforth referring to it as the 'cash burn'. First, we'll determine its cash runway by comparing its cash burn with its cash reserves.

View our latest analysis for Aura Biosciences

A company's cash runway is calculated by dividing its cash hoard by its cash burn. As at September 2024, Aura Biosciences had cash of US$174m and no debt. Looking at the last year, the company burnt through US$75m. Therefore, from September 2024 it had 2.3 years of cash runway. Arguably, that's a prudent and sensible length of runway to have. Depicted below, you can see how its cash holdings have changed over time.

Aura Biosciences didn't record any revenue over the last year, indicating that it's an early stage company still developing its business. So while we can't look to sales to understand growth, we can look at how the cash burn is changing to understand how expenditure is trending over time. Over the last year its cash burn actually increased by 14%, which suggests that management are increasing investment in future growth, but not too quickly. However, the company's true cash runway will therefore be shorter than suggested above, if spending continues to increase. While the past is always worth studying, it is the future that matters most of all. For that reason, it makes a lot of sense to take a look at our analyst forecasts for the company.

Given its cash burn trajectory, Aura Biosciences shareholders may wish to consider how easily it could raise more cash, despite its solid cash runway. Generally speaking, a listed business can raise new cash through issuing shares or taking on debt. Many companies end up issuing new shares to fund future growth. We can compare a company's cash burn to its market capitalisation to get a sense for how many new shares a company would have to issue to fund one year's operations.