STOCKHOLDER'S EQUITY

3 Months Ended

Mar. 31, 2015

Stockholders Equity Note [Abstract]

SHAREHOLDER’S EQUITY

9. STOCKHOLDER’S EQUITY

On March 10, 2014, we completed a follow-on public offering of 1.6 million shares of our common stock at a public offering price of $31.00 per share (the “March 2014 Offering”). We received gross proceeds of $50.0 million, or net proceeds of $46.7 million after deducting costs of $3.3 million, including the underwriters’ fees and commissions, as well as expenses directly related to the March 2014 Offering . The number of shares sold in the March 2014 Offering includes the exercise in full by the underwriters of their option to purchase an additional 0.2 million shares of common stock.

No warrants to purchase shares of common stock expired unexercised during the three months ended March 31, 2015 or 2014, respectively. No warrants to purchase shares of common stock were exercised in the three months ended March 31, 2015. In January 2014, warrants to purchase an aggregate of 20 thousand shares of common stock were exercised at $9.00 per share.