American billionaire Bill Ackman will donate $400m to brain research after his daughter suffered a brain haemorrhage that left her in a coma.

The investor, whose Pershing Square hedge fund ranks among the most famous investment management firms in the world, said the vast sum will go to a newly established research institute named after him and his wife, Neri Oxman, an architect and designer known for her work at MIT's Media Lab combining design, biology and computing.

Ackman's daughter Lucy suffered a stroke earlier this year that has left her unable to speak, see or walk. In a lengthy post on X, the financier described how his daughter was discovered unconscious in her New York apartment, and that when the emergency services arrived "they did not know what was wrong" with her.

Doctors eventually scanned Lucy's brain and discovered a "massive" haemorrhage, Ackman wrote to his 3 million social media followers. The haemorrhage was later removed during a lengthy surgery.

An institute focused on patient outcomes

The hedge fund billionaire and his wife established the Ackman Oxman Institute (AOI) in the wake of the ordeal. The Manhattan-based non-profit research centre will be devoted to becoming "the world's greatest brain research, rehabilitation, recovery, human optimisation and longevity institute," Ackman said.

The institute will be located in New York and will focus on patient-related outcomes rather than academia, papers and research-related breakthroughs. That patient-first emphasis comes against a backdrop of rising need: a 2024 analysis in The Lancet Neurology, drawing on 2021 data, estimated that 3.4 billion people worldwide live with neurological conditions, making them the world's leading cause of illness and disability. Much of the field's funding has historically flowed through academic and government channels, such as the multi-billion-dollar US BRAIN Initiative launched in 2013 to accelerate understanding of the human brain — a grant-and-paper ecosystem that contrasts with the outcomes-led model Ackman is championing. It will be based in a 400,000-square-foot building in Manhattan, part of which is set to be the repurposed studios that currently host Saturday Night Live, the NBC institution that has broadcast from Rockefeller Center since 1975.

The pledge represents one of the largest single philanthropic donations of the year. In 2025, British hedge fund manager Chris Hohn gave a record £1.4bn via his Children's Investment Fund Foundation, according to The Sunday Times' Giving List. Jeff Bezos's ex-wife MacKenzie Scott, meanwhile, has continued to release billions of pounds to good causes from the settlement of her divorce from the Amazon founder. Ackman is himself a signatory of the Giving Pledge, the campaign launched by Warren Buffett and Bill Gates in 2010 under which billionaires commit to giving away more than half of their fortunes.

'Commercial instincts' at a non-profit

Ackman's donation will be made in the form of 10 million shares in his New York-listed Pershing Square hedge fund, which were worth roughly $400m (£292m) at Thursday's closing price.

Ackman is worth an estimated $8bn according to Bloomberg's billionaires index. He shot to prominence with a $1bn short of American weight-loss supplement maker Herbalife, branding the firm a pyramid scheme and launching a publicity campaign to convince regulators to launch a formal investigation. The drive was ultimately unsuccessful, but it made the hedge fund one of the most famous investment shops on Wall Street.

He has since become an avid supporter of Donald Trump and — alongside Elon Musk — was one of his most outspoken supporters from the world of business and finance.

Ackman said the AOI will have "highly commercial instincts" despite its non-profit status, boasting a venture capital arm that will provide seed funding and then spin out any treatments and medications it develops. That structure resembles the approach known as venture philanthropy, previously used by disease foundations such as the Cystic Fibrosis Foundation, which helped fund early drug development and later sold its royalty rights for $3.3bn to bankroll further research.

His AI pitch also lands amid growing crossover between the two fields, with researchers using machine learning to analyse neural data and brain-computer interface developers such as Musk's Neuralink having begun human trials. "The advance of AI in the last few years will also enable us to greatly accelerate our mission," he added. "AI still has a lot to learn about human intelligence and the brain, and the AOI should be at the forefront of the interplay between the brain and AI."