Share-Based Compensation

3 Months Ended

Mar. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

6. Share-Based Compensation

Employee Share-Based Awards

Compensation cost for employee share-based awards is based on the grant-date fair value and is recognized over the vesting period of the applicable award on a straight-line basis. We issue employee share-based awards in the form of stock options and restricted stock units under our equity incentive plans, and stock purchase rights under the 2015 ESPP (see Note 5).

Valuation of Stock Options, Stock Purchase Rights and Restricted Stock Units

During the three months ended March 31, 2016 and 2015, the per share weighted average fair value of employee stock options granted were as follows:

	Three Months Ended
	March 31,
	2016		2015
Stock Options	$	0.44	$	1.29
Restricted Stock Units		—		—
Stock Purchase Rights		0.41		0.67

The estimated grant date fair values of the stock options and stock purchase rights were calculated using the Black-Scholes valuation model, and the following weighted average assumptions:

	Three Months Ended
	March 31,
	2016		2015
Stock Option Plans
Weighted-average expected term	5.0 Years		5.0 Years
Expected volatility		80%		85%
Risk-free interest rate		1.52%		1.40%
Dividend yield		0%		0%

Employee Stock Purchase Plan
Weighted-average expected term	0.6 Years		0.5 Years
Expected volatility		75%		60%
Risk-free interest rate		0.33%		1.62%
Dividend yield		0%		0%

The estimated fair value of restricted stock unit awards is calculated based on the market price of our common stock on the date of grant, reduced by the present value of dividends expected to be paid on our common stock prior to vesting of the restricted stock unit. Our estimate assumes no dividends will be paid prior to the vesting of the restricted stock unit.

As of March 31, 2016, there was $1,478,000, $70,000, and $1,000 of total unrecognized compensation expense related to unvested stock option awards, unvested restricted stock units and stock purchase rights, respectively, which are expected to be recognized over a weighted average period of 2.8 years, 1.0 years, and 0.02 years, respectively.

We had no share-based compensation capitalized at March 31, 2016 and it was immaterial at March 31, 2015.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

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