Michael Saylor, CEO of MicroStrategy, began selling a portion of the company's shares worth $216 million on Tuesday, according to a regulatory filing with the US Securities and Exchange Commission.

The document shows that Saylor proposed selling 310,000 stock option awards granted in 2014, which would expire in April.

Saylor said during MicroStrategy's third-quarter earnings call that he plans to sell 5,000 shares per trading day over the next four months, subject to a minimum price condition. This was first disclosed in this quarter's 10-Q filing, which said he could sell up to 400,000 shares of his vested options through April 26.

Form 10-Q is a comprehensive report on financial performance that must be filed quarterly by all public companies with the Securities and Exchange Commission.

This action will allow me to process personal obligations as well as obtain additional Bitcoin (BTC) to my personal account,” Saylor said during the call. Adding, I remain optimistic about MicroStrategy's prospects and I must point out that my stake in the company after these sales will remain very large.

MicroStrategy is the largest holder of Bitcoin with about 189,000 Bitcoin in its treasury after the last purchase in December, worth about $8.5 billion at current prices. The company's shares rose 8.5% on Tuesday, defying a market-wide decline in cryptocurrency-focused stocks.

The price of Bitcoin has risen in recent months, consolidating above the $45,000 level despite a 1% decline in the last 24 hours. Market participants expect a Bitcoin spot exchange-traded fund (ETF) to receive approval from the US Securities and Exchange Commission in the coming weeks, which will increase potential exposure to the asset from retail and institutional investors.