5. Share-Based Compensation Plans

2015 Equity Incentive Plan

In April 2015, our Board of Directors approved the 2015 Equity Incentive Plan, or the 2015 Plan, and authorized for issuance thereunder (i) an additional 1,000,000 shares of common stock plus (ii) the number of shares available for issuance pursuant to the grant of future awards under our 2005 Equity Incentive Plan determined as of the effective date of the 2015 Plan; plus (iii) the number of shares underlying outstanding stock awards granted under our previous stock option plans prior to the effective date of the 2015 Plan that expire or terminate for any reason prior to exercise or settlement, are forfeited or repurchased because of the failure to meet a contingency or condition required to vest such shares, or are reacquired, withheld (or not issued) to satisfy a tax withholding obligation in connection with an award. The 2015 Plan became effective upon the approval of the plan by our stockholders on June 23, 2015. Due to the effectiveness of our 2015 Plan, no additional awards will be made under our previous stock option plans. All outstanding awards under our previous stock option plans will continue to be subject to the terms and conditions as set forth in the agreements evidencing such stock awards and the terms of the applicable plan. Stock options issued under the 2015 Plan generally vest over 4 years; vesting is generally based on service time, and have a maximum contractual term of 10 years.

2015 Non-Employee Directors’ Stock Option Plan

In April 2015, our Board of Directors adopted the 2015 Non-Employee Directors’ Stock Option Plan, or the 2015 Directors’ Plan, and authorized for issuance thereunder and (i) an additional 250,000 shares of common stock plus (ii) the number of shares available for issuance pursuant to the grant of future awards under our previous non-employee directors stock option plan determined as of the effective date of the 2015 Directors’ Plan; plus (iii) the number of shares underlying outstanding stock awards granted under our previous non-employee directors stock option plan prior to the effective date of the 2015 Directors’ Plan that expire or terminate for any reason prior to exercise or settlement, are forfeited or repurchased because of the failure to meet a contingency or condition required to vest such shares, or are reacquired, withheld (or not issued) to satisfy a tax withholding obligation in connection with an award. The 2015 Directors’ Plan became effective upon the approval of the plan by our stockholders on June 23, 2015. Due to the effectiveness of our 2015 Directors’ Plan, no additional awards will be made under our previous non-employee directors’ stock option plan. The 2015 Directors’ Plan provides for the automatic grant of nonstatutory stock options to purchase shares of common stock to our non-employee directors, which vest over approximately one year and have a term of 10 years.

The following table sets forth the summary of option activity under our share-based compensation plans (the 2015 Plan, the 2005 Equity Incentive Plan, the 2015 Directors’ Plan and the 2005 Non-Employee Directors’ Stock Option Plan) for the three months ended March 31, 2016:

	Outstanding Options
	Number of			Weighted Average
	Shares			Exercise Price
Outstanding at January 1, 2016		2,326,401		$	4.23
Options granted		27,500			0.69
Options exercised		—			—
Options forfeited		—			—
Options cancelled		(214,482	)		(9.73	)
Outstanding at March 31, 2016		2,139,419		$	3.64

There were no options exercised during the three months ended March 31, 2016 and 2015.

The following table sets forth the summary of restricted stock units, or RSUs, activity under our share-based compensation plans for the three months ended March 31, 2016:

				Weighted Average
	Number of			Grant Date
	Shares			Fair Value
Outstanding at January 1, 2016		36,950		$	4.67
Granted		—			—
Released		—			—
Forfeited		(3,250	)		4.67
Outstanding at March 31, 2016		33,700		$	4.67

At March 31, 2016, RSUs to purchase 13,725 shares of common stock were vested but unreleased. These RSUs will be released upon opening of the trading window.

As of March 31, 2016, 2,683,289 and 410,000 shares remained available for issuance under the 2015 Plan and the 2015 Directors’ Plan, respectively.

2015 Employee Stock Purchase Plan

In April 2015, our Board of Directors adopted the 2015 Employee Stock Purchase Plan, or 2015 ESPP, and authorized for issuance thereunder (i) an additional 500,000 shares of our common stock plus (ii) the 128,249 additional shares, that remained available for issuance under our previous employee stock purchase plan after all outstanding purchase rights under such plan were exercised in October 2015. The 2015 ESPP allows eligible employee participants to purchase shares of our common stock at a discount through payroll deductions. The terms of any offering period under the 2015 ESPP will be determined by our Board of Directors. Purchases are generally made on the last trading day of each November and May. Employees may purchase shares at each purchase date at 85% of the market value of our common stock at either the beginning of the offering period or the end of the purchase period, whichever price is lower. Our previous employee stock purchase plan remained in effect until the conclusion of our previous offering, which concluded in October 2015.

As of March 31, 2016, 628,249 shares were available for issuance under the 2015 ESPP.