Billionaire investors Bill Ackman and Stanley Druckenmiller invested in Coupang years before its $4.6 billion IPO this week

• Bill Ackman and Stanley Druckenmiller were early investors in South Korea's Coupang.
• Ackman introduced founder Bom Kim to another of his key investors, David Frankel.
• Rose Park Advisors, founded by author Clayton Christensen, is another shareholder.
• See more stories on Insider's business page.

Billionaire investors Bill Ackman and Stanley Druckenmiller were early backers of Coupang, the South Korean e-commerce group which raised $4.6 billion on Thursday in the biggest US IPO of the year so far.

David Frankel, the cofounder of Founder Collective, tweeted a slide from one of Coupang's investor presentations that listed his firm and Ackman as "key investors." It also named Rose Park Advisors, the investment firm set up by Clayton Christensen - the late Harvard Business School professor and author of "The Innovator's Dilemma."

Harvard Business School appears to be the common denominator among several of the people involved. Bom Kim dropped out of its MBA program after six months to found Coupang in 2010. Ackman, a graduate of the program, apparently connected Kim with Frankel, another alumnus.

"I only had the chance to invest in Bom's vision because Bill introduced us and asked me for an opinion," Frankel tweeted. "I simply cannot thank him enough. Bill, please, please send any future grad students my way :-)"

Ackman, the founder and CEO of Pershing Square Capital Management, reacted to Frankel's gratitude with a blushing emoji on Twitter.

Kevin Warsh, a Coupang director and an advisor to Druckenmiller's Duquesne Family Office, told CNBC on Thursday the investor is also a longtime backer of the business. Duquesne owns stakes in Amazon and Chinese rival JD.com per its latest portfolio update, suggesting it's bullish on several e-commerce players.

Ackman and Druckenmiller's stakes in Coupang appear to be relatively small. Neither of the investors or their firms own more than 5% of the company, according to the list of principal shareholders in its IPO filing.

In contrast, Rose Park owns 5.1% of the online retailer following its market debut, the filing shows. Matthew Christensen, one of Clayton's sons, also sits on Coupang's board.

Another notable Coupang shareholder is SoftBank's Vision Fund. The tech conglomerate's investment arm owns 33% of the company following the IPO, SEC filings show.

Coupang's pre-IPO backers are likely sitting on substantial investment gains. The company's stock price surged more than 40% on its first day of trading, giving it a market capitalization of about $85 billion.