12.Controlled Equity Offering

In August 2015, we entered into a Controlled Equity OfferingSM Sales Agreement (Sales Agreement) with Cantor Fitzgerald & Co. (Cantor), as sales agent, pursuant to which we may sell, through Cantor, up to an aggregate of $30.0 million in shares of our common stock. All sales of our common stock will be made pursuant to a shelf registration statement that was declared effective by the Securities and Exchange Commission (SEC) on July 13, 2015.  Cantor acted as our sole sales agent for any sales made under the Sales Agreement for a low single-digit commission on gross proceeds.  The common stock was sold at prevailing market prices at the time of the sale.  During the nine months ended September 30, 2016, 7,895,563 shares of common stock were sold under the Sales Agreement, with aggregate gross proceeds of $24.3 million. As of September 30, 2016, 9,617,875 shares of our common stock had been issued under the Sales Agreement with aggregate gross proceeds of $30.0 million.  Of this amount, $1.3 million was received subsequent to September 30, 2016.  Accordingly, this amount was accounted for as a reduction in Additional Paid-in Capital as of September 30, 2016 in the accompanying Condensed Balance Sheet. As of September 30, 2016, there are no amounts remaining for future sales under the Sales Agreement.