NanoString Technologies Inc. closed its underwritten public offering 3,450,000 common shares at a price of $16.75 per share with net proceeds of about $56.5 million.

The shares sold included 450,000 shares as part of the full exercise by the underwriter of its option to purchase additional shares.

NanoString plans to use the net proceeds for general corporate purposes and working capital.

Robert W. Baird & Co. Inc. served as the sole underwriter for the offering.