It is usually uneventful when a single insider buys stock. However, When quite a few insiders buy shares, as it happened in Castle Biosciences, Inc.'s (NASDAQ:CSTL) case, it's fantastic news for shareholders.

While insider transactions are not the most important thing when it comes to long-term investing, we do think it is perfectly logical to keep tabs on what insiders are doing.

View our latest analysis for Castle Biosciences

The Last 12 Months Of Insider Transactions At Castle Biosciences

The Independent Director Ellen Goldberg made the biggest insider purchase in the last 12 months. That single transaction was for US$69k worth of shares at a price of US$17.27 each. That means that an insider was happy to buy shares at above the current price of US$14.45. While their view may have changed since the purchase was made, this does at least suggest they have had confidence in the company's future. To us, it's very important to consider the price insiders pay for shares. As a general rule, we feel more positive about a stock if insiders have bought shares at above current prices, because that suggests they viewed the stock as good value, even at a higher price.

While Castle Biosciences insiders bought shares during the last year, they didn't sell. You can see the insider transactions (by companies and individuals) over the last year depicted in the chart below. If you want to know exactly who sold, for how much, and when, simply click on the graph below!

Castle Biosciences is not the only stock insiders are buying. So take a peek at this free list of growing companies with insider buying.

Insider Ownership

Looking at the total insider shareholdings in a company can help to inform your view of whether they are well aligned with common shareholders. I reckon it's a good sign if insiders own a significant number of shares in the company. It appears that Castle Biosciences insiders own 3.4% of the company, worth about US$13m. This level of insider ownership is good but just short of being particularly stand-out. It certainly does suggest a reasonable degree of alignment.

So What Does This Data Suggest About Castle Biosciences Insiders?

There haven't been any insider transactions in the last three months -- that doesn't mean much. But insiders have shown more of an appetite for the stock, over the last year. Insiders do have a stake in Castle Biosciences and their transactions don't cause us concern. So these insider transactions can help us build a thesis about the stock, but it's also worthwhile knowing the risks facing this company. In terms of investment risks, we've identified 1 warning sign with Castle Biosciences and understanding this should be part of your investment process.

Of course Castle Biosciences may not be the best stock to buy. So you may wish to see this free collection of high quality companies.

For the purposes of this article, insiders are those individuals who report their transactions to the relevant regulatory body. We currently account for open market transactions and private dispositions of direct interests only, but not derivative transactions or indirect interests.

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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.