7. Stockholders’ Equity and Stock-Based Compensation

Common Stock

As of September 30, 2016, there were 200,000,000 shares of common stock authorized and 28,224,086 shares issued and outstanding. Each share of common stock has the right to one vote on all matters submitted to a vote of stockholders. The holders of common stock are also entitled to receive dividends whenever funds are legally available and if declared by the board of directors, subject to prior rights of holders of all classes of stock outstanding having priority rights as to dividends. No dividends have been declared or paid on the common stock through September 30, 2016.

On April 27, 2016, the board of directors resolved to retire 1,128,472 shares that were previously held as treasury stock.

Employee Equity Plans

Our 2015 Equity Incentive Plan (“EIP”) serves as the successor to our 2010 Equity Incentive Plan (together with the EIP, the “Stock Plans”). Pursuant to the terms of the EIP, the share reserve increased by 1,225,795 shares in January 2016.  As of September 30, 2016, 3,029,305 options to purchase remained outstanding under the 2010 Equity Incentive Plan.  As of September 30, 2016, we had approximately 1,874,405 shares of common stock available for future grants under the EIP.

We also have a 2015 Employee Stock Purchase Plan (“ESPP”). The ESPP allows eligible employees to purchase shares of our common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations.  Our board of directors approves the ESPP offerings. The offerings need not be identical, but each offering may not exceed 27 months and may specify one or more shorter purchase periods within the offering.  Pursuant to the terms of the ESPP, the share reserve increased by 272,399 shares in January 2016. On May 31, 2016, 156,469 shares of common stock were purchased under the ESPP at a purchase price of $13.60 per share resulting in cash proceeds of $2,128,000. As of September 30, 2016, 449,263 shares of common stock were available for issuance under the ESPP.

The following two tables show stock-based compensation expense by award type and where the stock-based compensation expense was recorded in our consolidated statements of operations (in thousands):

 

 

 

Stock Options

The Stock Plans provide for the issuance of incentive and nonstatutory options to employees and non-employees. A summary of information related to stock option activity during the nine months ended September 30, 2016 is as follows (in thousands, except per share data):

 

 

As of September 30, 2016 and December 31, 2015, we had $18,830,000 and $9,721,000, respectively, of unrecognized stock-based compensation costs related to non-vested awards that are expected to be recognized over a weighted average period of 3.0 years and 3.0 years, respectively.

As of September 30, 2016, we had $271,000 of unrecognized stock-based compensation expense related to our ESPP that is expected to be recognized over the term of the offering period ending November 30, 2016. As of December 31, 2015, we had $919,000 of unrecognized stock-based compensation expense related to our ESPP that was recognized over the initial term of the offering period through May 31, 2016.

Restricted Stock Units

The Stock Plans provide for the issuance of restricted stock units (“RSUs”) to employees. A summary of information related to RSU activity during the nine months ended September 30, 2016 is as follows (in thousands, except per share amounts):