Pershing Square Capital CEO Bill Ackman thinks Anthropic (ANTH.PVT) is a great story with a business that has real potential. Just don't expect him to be a buyer early on when Anthropic becomes publicly traded.

"We think of ourselves as very low-risk investors. We want to invest in businesses that we can predict with a very high degree of confidence," the well-known value investor said at Yahoo Finance Invest. "I think Anthropic is perhaps the most amazing business story of this century in terms of from zero to where it is today — it's an absolutely remarkable story. An incredibly impressive story.

I think it's just a much more complicated question as to what that business is worth. It's very hard to nail that with any degree of precision. It could be worth a lot more, a lot less, depending upon a few variables that are difficult to predict. And that's why it doesn't fit into our portfolio."

Anthropic has set an IPO price range of $70 to $78 per share, targeting a fully diluted valuation of approximately $1.4 trillion. The company could raise up to $100 billion from its IPO at the high end of the range.

But the business has a lot to prove to justify keeping such a lofty valuation in public markets.

In an amended S-1 filing, Anthropic said that third quarter sales rose 1,127% to $17 billion. Revenue growth slowed on a quarter-over-quarter basis. Third quarter sales increased 47% compared with a 144% growth rate in the second quarter. Sales increased 132% in the first quarter.

The company also lost a staggering $23.29 billion in the third quarter.

Anthropic is expected to debut on public markets on Thursday, Nov. 19. It plans to list on the Nasdaq under the ticker symbol ANT.

"I think Anthropic is on the cusp, or might even be at, a place in terms of its operating profitability, where it's real operating profitability," Ackman added. "I think the issue is if Anthropic doesn't stay in the lead position, then the real questions about the business model [emerge]. So the capex they have to spend is really real … So I would just say it's a much more complicated question.

And there's a much wider range of outcomes — it's a more speculative bet than buying, for example, Visa, a company we own."

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