OpenAI is losing top executives just as it moves toward a huge stock market debut, a warning sign for would-be investors.

• Two senior leaders are gone in days: chief revenue officer Denise Dresser left this week, right after longtime exec Brad Lightcap said he was leaving too.
• The timing is bad, coming just as OpenAI gears up for one of the biggest IPOs ever.
• Losing top people right before going public makes investors nervous about how stable the company really is.
• It raises the question of whether more insiders will head out before the listing.

Outlook: More executive departures could cool investor demand as the IPO approaches.