Equity Offering

3 Months Ended

Mar. 31, 2019

Stockholders Equity Note [Abstract]

Equity Offering

8. Equity Offering

On July 28, 2016, the Company filed a prospectus supplement and associated sales agreement related to an at-the-market (“ATM”) equity offering program pursuant to which the Company may sell, from time to time, common stock with an aggregate offering price of up to $75,000 through Cowen and Company LLC, as sales agent, for general corporate purposes.  During the three months ended March 31, 2019, the Company sold a total of 893,650 shares of its common stock under the ATM program for $3,453, or an average of $3.86 per share, and received proceeds of $3,375, net of commissions of $78.  As of March 31, 2019, the Company had sold a total of 4,599,586 shares of its common stock under the ATM program for $52,980, or an average of $11.52 per share, and received proceeds of $51,788, net of commissions of $1,192.  Subsequent to March 31, 2019, the Company sold an additional 356,350 shares of its common stock under the ATM program for $1,259, or an average of $3.53 per share, and received proceeds of $1,231, net of commissions of $28.