Palantir (NYSE: PLTR) has been one of the hottest artificial intelligence (AI) stocks to own this year. It's up around 280% as of the time of this writing and has far exceeded many investors' expectations.

Palantir Technologies, the newest S&P 500 member, was the index's best performer in 2024 as of Nov. 15. But it didn't last long.Nvidia was the biggest S&P 500 leader in 2023 and ruled for much of 2024,

Among those selling the stock was CEO Alex Karp, who filed to sell 4.5 million shares of the stock on Friday, which has a market value of $266 million. That sale was predetermined by a 10b5-1 plan, which sells stock at set intervals to avoid suspicions of insider trading. Palantir stock was down 5.38% as of 11:45 a.m. ET.