MicroStrategy (MSTR) executive chairman Michael Saylor began to sell $216 million worth (at current prices) of company shares on Tuesday, according to a regulatory filing with the U.S. Securities and Exchange Commission.

The document shows that Saylor intends to sell 310,000 shares. These shares were awarded as stock options in 2014 and were set to expire in April 2024.

The sales plan was disclosed a couple of months ago, with Saylor saying during Microstrategy's third quarter earnings call that he plans to sell 5,000 shares per trading day commencing on Jan. 2. and continuing over four months, subject to a minimum price condition. That quarter's 10-Q filing said he can sell up to 400,000 shares of his vested options through April 26, 2024.

"Exercising this option will allow me to address personal obligations as well as acquire additional bitcoin (BTC) to my personal account," Saylor said during the call. "I continue to be optimistic about MicroStrategy's prospects and should note that my equity stake in the company after these sales will remain very significant."

MicroStrategy is the largest corporate holder of bitcoin with some 189,000 BTC in its treasury after the latest purchase in December, worth some $8,5 billion at current prices. Shares of MicroStrategy gained 8.5% Tuesday, defying a market-wide slump of cryptocurrency-focused stocks.

Bitcoin's price has risen over recent months, trading around $45,000 as of press time (midnight UTC). Market participants expect a spot bitcoin exchange-traded fund (ETF) approval from the U.S. Securities and Exchange Commission in the coming weeks, which would increase potential exposure to the asset from retail and institutional investors.