One person's trash is another person's treasure. That's proven out every single day on the stock market. Every time a stock is sold by one person, there's another person on the other end of the transaction ready and willing to buy the stock.

I wouldn't say, though, that every time someone sells a stock they think it's trash. For example, well-known investor Cathie Wood recently sold shares of several companies that are still holdings in her ARK exchange-traded funds (ETFs). While she obviously had reasons to sell these stocks, it doesn't necessarily mean that she thinks poorly of them.

There are some stocks in which the ARK ETFs reduced their positions that still have strong growth prospects. Here are three growth stocks that Wood is selling that I think are especially still worth buying.

A die with "buy" on one side and "sell" on another side.

Image source: Getty Images.

Regeneron Pharmaceuticals

Wood's ARK Genomic Revolution ETF has sold shares of Regeneron Pharmaceuticals (REGN -0.34%) six times so far in August. However, the biotech stock still remains one of the top 10 holdings for the ETF.

I think Regeneron's short- and long-term prospects continue to be very good. Over the short term, the latest COVID-19 wave should boost sales of the company's REGEN-COV COVID-19 antibody cocktail. But it's Regeneron's long-term opportunities that provide the main reason to consider buying the stock.

Eye-disease drug Eylea and autoimmune disease drug Dupixent continue to enjoy solid momentum. Regeneron is evaluating both drugs in phase 3 clinical studies with the hopes of picking up additional approved indications.

Libtayo could be the company's next blockbuster. That's especially the case after a late-stage study of the drug in combination with chemotherapy was recently stopped early because the combo was so effective in improving survival in patients with advanced non-small cell lung cancer.

I also like Regeneron's pipeline. It's loaded with experimental antibody therapies targeting a wide range of diseases. In addition, the company has a fast-growing cash stockpile that it could use to further bolster its pipeline.

Sea Limited

Two of Wood's ETFs have trimmed their positions in Sea Limited (SE -0.60%) this month -- her flagship ARK Innovation ETF and the ARK Next Generation Internet ETF. Both ETFs still own sizable stakes in Sea Limited, though.

I agree with my Motley Fool colleagues Brian Feroldi and Brian Stoffel that even after huge gains over the last two years, Sea Limited is just getting started. For example, the company plans to develop its extraordinarily popular Free Fire mobile game into a full-blown social platform.

Free Fire is gaining momentum not only in Southeast Asia and Latin America, but also in other parts of the world. Sea Limited is expanding its gaming ecosystem with esports and collaborations with third-party developers as well.

But it's a mistake to view Sea Limited as only a gaming play. The company also has an up-and-coming e-commerce platform with Shopee and a digital financial services business built around SeaMoney. My take is that both of these businesses will generate strong growth over the long run.

The Trade Desk

The ARK Next Generation Internet ETF has also sold more than 800,000 shares of The Trade Desk (TTD 0.30%) so far in August. Even with those sales, however, the stock still ranks in the top 25 holdings for the ETF.

There are similarities between my views of Regeneron and The Trade Desk, although their businesses are about as different as you can get. Both companies have strong short-term and long-term prospects.

One key short-term growth driver for The Trade Desk is its recent launch of the Solimar digital advertising platform. It's the company's biggest release ever. CEO Jeff Green said in the second-quarter conference call that management expects the majority of impressions on its overall platform will be purchased using Solimar by the beginning of 2022.

I also think that The Trade Desk is like Sea Limited in that they're both just getting started. Independent research firm MoffettNathanson expects that the ad-supported video-on-demand market will reach nearly $18 billion by 2025. That's four times larger than the market size last year. The Trade Desk is poised to benefit significantly from this growth.