The sales occurred after Moderna (MRNA) excited Wall Street before markets opened Monday by announcing encouraging vaccine trial results.
After spiking to as high as $87 on Monday, Moderna's stock price has since retreated below $70 as medical experts have debated the importance of the early findings.
On May 15, just days before the results were announced, Kim sold 20,000 shares of stock worth $1.3 million.
Moderna's stock has since retreated
Andrew Gordon, director of research services at Equilar, said there would only be a "legal issue if they created or modified their 10b5-1 plan while in possession of material insider information."
"It's not uncommon for insiders to sell shares they own, nor is it bad for them to capitalize on the current stock price," Gordon said in an email.
"It'll look bad from a PR perspective if Moderna's stock price starts to fall dramatically after all this trading," Gordon said.
If future studies go well, Moderna has said its vaccine could be available to the public as early as January.
Charles Elson, a corporate governance expert at the University of Delaware, said the Moderna stock sales underscore why he has always believed executives should not sell stock while they are at the company.