Tesaro prices biggest biotech public offering in nearly a year

Shares of US biotech firm Tesaro (Nasdaq: TSRO) rose 8.6% to $84.05 after it priced an underwritten public offering of an aggregate of 4,650,000 shares of its common stock at an offering price to the public of $81.00 per share.

The gross proceeds from the offering will be around $376.7 million, the largest offering to be raised by a US biotech firm since the sector began a significant selloff nearly a year ago. The further rise in the value of the stock comes after a 113% gain to $79.30 that followed release of extremely  encouraging Phase III results with its investigational drug niraparib, which slowed the growth of ovarian tumors earlier this week.

In addition, Tesaro has granted the underwriters an option to purchase up to an additional $56.5 million of its common stock. The company estimates that the net proceeds from the offering will be about $355.6 million after deducting the underwriting discount and other offering expenses payable by Tesaro, but excluding any exercise of the underwriters’ option.