OpenAI gained between US$65.5 billion and US$109.4 billion from the billionaire entrepreneur’s contributions when he was co-founding OpenAI from 2015, while Microsoft gained between US$13.3 billion and US$25.1 billion, Musk said in the federal court filing ahead of his trial against the two companies.

OpenAI, Microsoft and Musk’s lawyers did not immediately respond to requests for comments outside business hours.

OpenAI has called the lawsuit “baseless” and part of a “harassment” campaign by Musk. A Microsoft lawyer has said there is no evidence that the company “aided and abetted” OpenAI.

Musk, who left OpenAI in 2018 and now runs xAI with its competitor chatbot Grok, alleges that ChatGPT operator OpenAI violated its founding mission in a high-profile restructuring to a for-profit entity.

A judge in Oakland, California, ruled this month that a jury will hear the trial, expected to start in April.

Musk’s filing says he contributed about US$38 million, 60% of OpenAI’s early seed funding, helped recruit staff, connect the founders with key contacts and lend credibility to the project when it was created.

“Just as an early investor in a startup company may realise gains many orders of magnitude greater than the investor’s initial investment, the wrongful gains that OpenAI and Microsoft have earned – and which Mr. Musk is now entitled to disgorge – are much larger than Mr. Musk’s initial contributions,” Musk argues.

The filing says Musk’s contributions to OpenAI and Microsoft were calculated by his expert witness, financial economist C. Paul Wazzan.

Musk may seek punitive damages and other penalties, including a possible injunction, if the jury finds either company liable, the filing says, without specifying what form any injunction might take.