In a Form 4 filing with the SEC late Tuesday, Apple (NASDAQ: AAPL) CEO Tim Cook disclosed selling 511,000 common shares of the iPhone giant worth about $88 million. Of the shares, 270,431 were used for taxes, leaving Cook with net proceeds of approximately $41 million.

It was Cook's largest stock sale in more than two years and comes with shares well off recent highs but still up 33% on the year.

Cook still owns 3,280,053 Apple shares following the transaction, worth about $563 million based on current prices.

In 2021, Cook sold $750 million in Apple stock.

The latest stock sale disclosure comes on the same day that Apple received a rare Wall Street downgrade. KeyBanc downgraded the stock to Sector Weight from Overweight. The analyst cited valuation, with shares trading near-peak multiples despite a mature growth profile. In addition, the analyst said the Americas region will likely see soft growth and the international segment is seeing challenging trends.

Shares of Apple are down 0.5% in pre-open trading Wednesday.