Pfenex Inc., a Sorrento Valley biotech firm specializing in a class of drugs called biosimilars, raised $50 million in its initial public offering July 23, selling 8.33 million shares at $6 per share.

The amount was short of the $74.8 million that the business said that it hoped to raise last month.

Pfenex (NYSE: PFNX) was spun out of Dow Chemical in 2009.

During the stock’s first day of trading July 24, shares fell to $5.28 and closed at $5.30.

Underwriters received a 30-day option to purchase up to 1.25 million additional shares of stock at the IPO price. William Blair & Co. LLC and JMP Securities LLC were joint book-running managers for the offering and Mizuho Securities USA Inc. was a co-manager.