Despite an already strong run, Puma Biotechnology, Inc. (NASDAQ:PBYI) shares have been powering on, with a gain of 31% in the last thirty days. Looking back a bit further, it's encouraging to see the stock is up 56% in the last year.

Since its price has surged higher, Puma Biotechnology's price-to-earnings (or "P/E") ratio of 79.6x might make it look like a strong sell right now compared to the market in the United States, where around half of the companies have P/E ratios below 16x and even P/E's below 9x are quite common. Although, it's not wise to just take the P/E at face value as there may be an explanation why it's so lofty.

Puma Biotechnology has been struggling lately as its earnings have declined faster than most other companies. One possibility is that the P/E is high because investors think the company will turn things around completely and accelerate past most others in the market. You'd really hope so, otherwise you're paying a pretty hefty price for no particular reason.

Is There Enough Growth For Puma Biotechnology?

The only time you'd be truly comfortable seeing a P/E as steep as Puma Biotechnology's is when the company's growth is on track to outshine the market decidedly.

Taking a look back first, the company's earnings per share growth last year wasn't something to get excited about as it posted a disappointing decline of 65%. Unfortunately, that's brought it right back to where it started three years ago with EPS growth being virtually non-existent overall during that time. Accordingly, shareholders probably wouldn't have been overly satisfied with the unstable medium-term growth rates.

Looking ahead now, EPS is anticipated to slump, contracting by 16% per annum during the coming three years according to the two analysts following the company. With the market predicted to deliver 11% growth per annum, that's a disappointing outcome.

In light of this, it's alarming that Puma Biotechnology's P/E sits above the majority of other companies. It seems most investors are hoping for a turnaround in the company's business prospects, but the analyst cohort is not so confident this will happen. Only the boldest would assume these prices are sustainable as these declining earnings are likely to weigh heavily on the share price eventually.

The Final Word

Puma Biotechnology's P/E is flying high just like its stock has during the last month. While the price-to-earnings ratio shouldn't be the defining factor in whether you buy a stock or not, it's quite a capable barometer of earnings expectations.

We've established that Puma Biotechnology currently trades on a much higher than expected P/E for a company whose earnings are forecast to decline. Right now we are increasingly uncomfortable with the high P/E as the predicted future earnings are highly unlikely to support such positive sentiment for long. Unless these conditions improve markedly, it's very challenging to accept these prices as being reasonable.

It's always necessary to consider the ever-present spectre of investment risk. We've identified 5 warning signs with Puma Biotechnology (at least 1 which is concerning), and understanding them should be part of your investment process.

If these risks are making you reconsider your opinion on Puma Biotechnology, explore our interactive list of high quality stocks to get an idea of what else is out there.

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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.