Sam Altman gracefully thanked his OpenAI cofounder who quit. Then another exec quit hours later.

• Jan Leike, a co-leader of OpenAI's superalignment group, announced his resignation on Tuesday.
• His exit follows the departure of Ilya Sutskever, an OpenAI cofounder who was its chief scientist.

OpenAI's leadership shake-up continues with the departure of Jan Leike, who tweeted on Tuesday night that he'd resigned.

Leike co-led OpenAI's superalignment group, a team that focuses on making its artificial-intelligence systems align with human interests.

In September, he was named one of Time 100's most influential people in AI.

Leike announced his departure hours after Ilya Sutskever, the other superalignment leader, said he was leaving.

Sutskever, who cofounded OpenAI and was its chief scientist, said he was leaving after almost a decade in a post on X, formerly known as Twitter. Sutskever added that he was "excited" about his next steps, which he said he'd share more details about "in due time."

Leike's short post — "I resigned" — is sure to fuel speculation about his and Sutskever's next moves.

In a post on X, OpenAI CEO Sam Altman said, "Ilya and OpenAI are going to part ways. This is very sad to me; Ilya is easily one of the greatest minds of our generation, a guiding light of our field, and a dear friend. His brilliance and vision are well known; his warmth and compassion are less well known but no less important."

Altman didn't immediately address Leike's departure.

The news came on the heels of several high-profile OpenAI departures. Two executives, Diane Yoon and Chris Clark, quit weeks ago, as The Information reported. Yoon was the vice president of people, and Clark was head of nonprofit and strategic initiatives. The Information also reported last month that OpenAI had parted ways with the researchers Leopold Aschenbrenner and Pavel Izmailov. They had both worked on the superalignment team.

Business Insider reported last week that two employees who worked on safety and governance had resigned in recent months. Daniel Kokotajlo left last month and William Saunders departed OpenAI in February.

OpenAI and Leike didn't immediately respond to requests for comment from BI, sent outside standard working hours.