This article is more than 2 years old.

June 1, 2016 This article is more than 2 years old.

Not long ago, Elizabeth Holmes was regarded as one of the US’s most successful female entrepreneurs, with a net worth of $4.5 billion, Forbes estimated.

Today Forbes cut that figure to zero.

Holmes’s wealth is entirely wrapped up in her 50% stake in Theranos, the medical testing start-up she founded in 2003. The privately-held company in Palo Alto became a standout for its bold attempts to revolutionize the diagnostic industry—it claimed it could test for 240 diseases from a few drops of blood—and for A-listers like Henry Kissinger and Bill Frist on its advisory board.

Last year, Forbes pegged its value at $9 billion, based on the sale of stakes to investors. Since that lofty estimate, Theranos has been battered by bad news, starting with reports in the Wall Street Journal in October that its tests were inaccurate. That triggered an inquiry from the federal Centers for Medicare and Medicaid Services, which proposed banning Holmes from the industry.

Forbes went back to its slide rule and, after talking to venture capitalists and industry experts, recalculated Theranos’ value at $900 million, based on its intellectual property and money it has already raised. “At such a low valuation, Holmes’s stake is essentially worth nothing,” Matt Herper writes.

That’s because Theranos’s other investors own preferred shares, and since Holmes owns common shares, they would get paid first if the company were forced to liquidate.

Theranos didn’t provide a comment to Forbes and has yet to respond to an email from Quartz sent before the start of business hours in California today.

Update: Theranos sent an email with the following statement: “As a privately held company, we declined to share confidential financial information with Forbes. As a result, the article was based exclusively on speculation and press reports.”