Longtime OpenAI executive Brad Lightcap announced his departure on Tuesday, the latest in a series of recent leadership shake-ups at the artificial intelligence company.

Lightcap joined OpenAI in 2018 and held a number of senior leadership roles during his tenure, including a four-year stint as the company's operating chief. He served in that role until April, when he moved into a new position focused on "special projects." The company said at the time that Denise Dresser, OpenAI's chief revenue officer, would take over most of Lightcap's responsibilities.

In a post on X on Tuesday, Lightcap said he is moving on from OpenAI to "start something new."

"I feel incredibly fortunate to have spent most of the last decade pursuing our mission and building this company," Lightcap wrote. "Sitting here today, mission success feels within sight. It has been the honor of my life to help bring us to this point, and to do it alongside all of you."

Lightcap's departure marks another key loss for OpenAI at a time when the company is trying to justify its $852 billion valuation and gear up for what's expected to be a monster initial public offering. Fidji Simo, who had been OpenAI's product and business chief, announced last month she was stepping down from her role at the company to focus on recovery after a "severe exacerbation of a chronic illness."

Three other OpenAI execs announced their departures in April. They were Bill Peebles, who led OpenAI's defunct short-form video app Sora, Kevin Weil, the vice president of OpenAI for Science, and Srinivas Narayanan, tech chief of B2B Applications.

Lightcap has been one of OpenAI CEO Sam Altman's closest confidantes since the early days of the company. The two worked together at the startup incubator Y Combinator, which Altman led prior to OpenAI.

Over an 18-month stretch through mid-2025, Lightcap built OpenAI's go-to-market team from around 50 people to more than 700, which included sales reps and staffers focused on customer success, developer relations and strategic partnerships.

That push started in 2023, with GPT-4 and the launch of ChatGPT Enterprise, as OpenAI tried to take its consumer success into the enterprise world to take on its rival Anthropic. Clients started coming in from every direction, Lightcap told CNBC in an interview about a year ago.

"Among the most rewarding parts of this journey for me has been watching each of these teams mature under brilliant leaders," Lightcap wrote on Tuesday. "I am excited for the next decade in the hands of this incredibly capable team."