7. EQUITY COMPENSATION PLANS

3 Months Ended

Jul. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

7. EQUITY COMPENSATION PLANS

Stock Incentive Plans

As of July 31, 2015, we had an aggregate of 24,721,484 shares of common stock reserved for issuance under our stock incentive plans, of which, 23,867,253 shares were subject to outstanding options and 854,231 shares were available for future grants of share-based awards.

The following summarizes our stock option transaction activity for the three months ended July 31, 2015:

Stock Options	Shares			Weighted Average Exercisable Price
Outstanding, May 1, 2015		20,708,672			$  1.54
Granted		3,523,911			$  1.31
Exercised		(99,091	)		$  0.94
Canceled or expired		(266,239	)		$  1.70
Outstanding, July 31, 2015		23,867,253			$  1.51

Employee Stock Purchase Plan 

We have reserved a total of 5,000,000 shares of common stock to be purchased under our 2010 Employee Stock Purchase Plan (the “ESPP”), of which 2,443,056 shares remained available to purchase at July 31, 2015. The ESPP allows eligible employees on a voluntary basis to purchase shares of our common stock directly from us. Under the ESPP, we sell shares to participants at a price equal to the lesser of 85% of the fair market value of our common stock at the (i) beginning of a six-month offering period, or (ii) end of the six-month offering period. The ESPP provides for two six-month offering periods each year; the first offering period begins on the first trading day on or after each November 1; the second offering period begins on the first trading day on or after each May 1. No shares were purchased under the ESPP during the three months ended July 31, 2015 as the current six-month offering period ends on October 31, 2015.

Share-Based Compensation

Total share-based compensation expense is included in the accompanying interim unaudited condensed consolidated statements of operations as follows:

	Three Months Ended July 31,
	2015		2014
Cost of contract manufacturing	$	13,000	$	24,000
Research and development		471,000		743,000
Selling, general and administrative		699,000		1,009,000
Total share-based compensation expense	$	1,183,000	$	1,776,000
Share-based compensation from:
Stock options	$	1,124,000	$	1,697,000
Employee stock purchase plan		59,000		79,000
	$	1,183,000	$	1,776,000

As of July 31, 2015, the total estimated unrecognized compensation cost related to non-vested employee stock options was $5,946,000. This cost is expected to be recognized over a weighted average vesting period of 1.63 years based on current assumptions. In addition, as of July 31, 2015, the total estimated unrecognized compensation cost related to non-vested stock options granted to non-employees was $130,000 based on a July 31, 2015 measurement date. This cost is expected to be recognized over a weighted average vesting period of 0.95 years.