Billionaire Patrick Soon-Shiong’s clinical-stage immunotherapy firm NantKwest Inc. debuted at $25 a share in its first day of trading on the Nasdaq Tuesday, raising more than $207 million with the sale of 8.3 million shares.

The offering price, $2 above its expected range, gave NantKwest a fully diluted value of $2.65 billion, making it the largest biotech to IPO in at least 20 years, according to Matthew Kennedy, an analyst at Greenwich, Ct.-based Renaissance Capital. NantKwest also sold nearly 1.3 million more shares than it initially intended.

The stock shot up 39 percent, closing its first day of trading at $34.64 and a market cap of $3.7 billion.

NantKwest makes a proprietary line of the immune system’s “natural killer” cells used in the treatment of cancer, infectious and inflammatory diseases. It has developed an “off-the-shelf” treatment meant to be manufactured and delivered via a blood transfusion, and is working on using its platform to fight multiple tumor types.

“This a company that’s taking advantage in your body of these natural killer cells,” said Soon-Shiong, NantKwest’s chief executive. “This is the natural order of the immune system. It’s there to protect the body from cancer and infected cells.”

Soon-Shiong controls a 58 percent stake in the company, valued at more than $1.7 billion.

NantKwest’s therapy is different from t-cell drugs being developed by immuno-oncology firms like Santa Monica’s Kite Pharma Inc., which remove white blood cells from the body, engineer them to find the patient’s cancer and then infuse them back into the body.

“People are very excited about (the company) clearly based on the stock movement today alone,” said Cowen & Co. biotech analyst Boris Peaker, who does not cover NantKwest but had reviewed the firm’s SEC filings.

Though the company’s regulatory paperwork said it was based in Cardiff-by-the-Sea with operations in Culver City, Soon-Shiong referred to the latter as NantKwest’s headquarters. If that’s indeed the case, it would mean NantKwest is one of the biggest biotech firms based in Los Angeles by market cap.

“It deserves to be a major biotech center,” Soon-Shiong said of the city, referencing other large peers Kite and Westwood’s Puma Biotechnology Inc.

The billionaire physician may just be getting started with big dollar IPOs. Soon-Shiong indicated previously that he expected NantHealth, his Culver City-based health care IT firm to go public by the end of the year. The company recently scored a $200 million investment from Chicago-based Allscripts Healthcare Solutions Inc. in exchange for a 10 percent stake, which valued NantHealth at $2 billion.

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