NOTE 5 — STOCK BASED COMPENSATION

The Company recognizes stock-based compensation in accordance with ASC 718, “Compensation—Stock Compensation.” Stock-based compensation expense, which consists of the compensation cost for employee stock options and the 2004 Purchase Plan, and the value of options issued to non-employees for services rendered, was allocated to research and development and general and administrative expenses in the unaudited consolidated statements of operations for the three and six months ended June 30, 2016 and 2015 as follows (in thousands):

Valuation Assumptions

The Company estimated the fair value of stock options granted using the Black-Scholes option-pricing formula and a single option award approach. This fair value is being amortized ratably over the requisite service periods of the awards, which is generally the vesting period. The fair value of employee stock options and employee purchase rights under the 2004 Purchase Plan was estimated using the following weighted-average assumptions for the three and six months ended June 30, 2016 and 2015:

To determine the expected term of the Company’s employee stock options granted, the Company utilized the simplified approach as defined by SEC Staff Accounting Bulletin No. 107, “Share-Based Payment” (“SAB 107”). To determine the risk-free interest rate, the Company utilized an average interest rate based on U.S. Treasury instruments with a term consistent with the expected term of the Company’s stock based awards. To determine the expected stock price volatility for the Company’s stock based awards, the Company utilized the historical volatility of the Company’s common stock. The fair value of all the Company’s stock based awards assumes no dividends as the Company does not anticipate paying cash dividends on its common stock.

Employee Stock-based Compensation Expense

As required by ASC 718, the Company recognized $0.8 million and $1.6 million of stock-based compensation expense related to stock options and purchase rights under the Company’s equity incentive plans and 2004 Purchase Plan for the three and six months ended June 30, 2016 and $1.9 million and $3.3 million of stock-based compensation for the three and six months ended June 30, 2015.  As of June 30, 2016, the total unrecognized compensation cost related to unvested stock-based awards granted to employees under the Company’s equity incentive plans was approximately $2.4 million before forfeitures. This cost will be recorded as compensation expense on a ratable basis over the remaining weighted average requisite service period of approximately 2.7 years.

Equity Incentive Plans

Equity Incentive Plans   At June 30, 2016, 857,479 shares were authorized and available for issuance under the 2014 Equity Incentive Plan.

The following table summarizes stock option activity under the Company’s equity incentive plans:

No stock options were exercised during the six months ended June 30, 2016. The total intrinsic value of stock options exercised during six months ended June 30, 2015 was $0.2 million, as determined at the date of the option exercise. Cash received from stock option exercises was $0.1 million for the six months ended June 30, 2015. The Company issues new shares of common stock upon exercise of options. In connection with these exercises, there was no tax benefit realized by the Company due to the Company’s current loss position.

2004 Employee Stock Purchase Plan On January 1, 2016, an additional 100,000 shares was authorized for issuance under the 2004 Purchase Plan pursuant to the annual automatic increase to the authorized shares under the 2004 Purchase Plan. For the six months ended June 30, 2016, plan participants had purchased 49,366 shares at an average purchase price of $0.24 for total cash proceeds of $12,000.  At June 30, 2016, 177,471 shares were authorized and available for issuance under the 2004 Purchase Plan.