OpenAI is preparing to sell around $6 billion in stock as part of a secondary sale that would value the company at roughly $500 billion, CNBC confirmed Friday.

The shares would be sold by current and former employees to investors including SoftBank, Dragoneer Investment Group and Thrive Capital, according to a person familiar with the negotiations who asked not to be named due to the confidential nature of the discussions. The talks are still in early stages and the details could change.

Bloomberg was first to report the discussions. All three firms are existing investors in OpenAI, but Thrive Capital could lead the round, as CNBC previously reported . SoftBank, Dragoneer and Thrive Capital did not immediately respond to CNBC's request for comment.

OpenAI's valuation has grown expon

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