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STOCKHOLDERS' EQUITY (Tables) | 12 Months Ended
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Dec. 31, 2015
STOCKHOLDERS' EQUITY |
Schedule of aggregate option and award activity |
|  |  |  | Outstanding Options
|  | Shares Available For Grant |  | Number of Shares |  | Weighted Average Exercise Price Per Share |  | Weighted Average Remaining Contractual Life (In years) |  | Aggregate Intrinsic Value (In thousands)
Balance at December 31, 2014 |  |  | 13,384,883 |  |  | 16,958,944 |  | $3.16 |  |  |  | $16,038
Options granted |  |  | (2,875,000 | ) |  | 2,875,000 |  | $4.29 |  |  |  |
Awards granted |  |  | (14,015 | ) |  | — |  | $ — |  |  |  |
Options exercised |  |  | — |  |  | (1,069,838 | ) | $2.06 |  |  |  |
Options cancelled/forfeited |  |  | 1,558,423 |  |  | (1,558,423 | ) | $4.65 |  |  |  |
Awards cancelled/forfeited |  |  | 625 |  |  | — |  | $ — |  |  |  |
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Balance at December 31, 2015 |  |  | 12,054,916 |  |  | 17,205,683 |  | $3.29 |  | 6.89 |  | $29,267
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Options exercisable at December 31, 2015 |  |  |  |  |  | 11,356,232 |  | $2.98 |  | 6.18 |  | $23,234
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Options fully vested and expected to vest at December 31, 2015 |  |  |  |  |  | 16,703,236 |  | $3.26 |  | 6.84 |  | $28,932
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Schedule of information about stock options outstanding by exercise price range | Information about stock options outstanding as of December 31, 2015 is as follows:
|  | Options Outstanding
Exercise Price Range |  | Number of Shares |  | Weighted Average Exercise Price Per Share |  | Weighted Average Remaining Contractual Life (In years)
$1.10 - $1.51 |  |  | 6,003,210 |  | $1.45 |  | 6.58
$1.55 - $4.34 |  |  | 5,412,577 |  | $3.21 |  | 7.63
$4.42 - $5.09 |  |  | 4,744,005 |  | $4.99 |  | 7.41
$5.14 - $9.32 |  |  | 1,045,891 |  | $6.47 |  | 2.45
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$1.10 - $9.32 |  |  | 17,205,683 |  | $3.29 |  | 6.89
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Schedule of aggregate restricted stock activity |
|  | Number of Shares |  | Weighted Average Grant Date Fair Value Per Share |  | Weighted Average Remaining Contractual Term (In years)
Non-vested restricted stock at December 31, 2014 |  |  | 60,970 |  | $4.73 |  | 0.37
Granted |  |  | 14,015 |  | $3.75 |  |
Vested |  |  | (73,860 | ) | $4.54 |  |
Cancelled/forfeited |  |  | (625 | ) | $4.65 |  |
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Non-vested restricted stock at December 31, 2015 |  |  | 500 |  | $4.65 |  | 0.10
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Summary of allocation of stock-based compensation expense related to share-based payment awards |
|  | Year Ended December 31, |
(In thousands) |  | 2015 |  | 2014 |  | 2013 |
Research and development |  | $ | 2,139 |  | $ | 2,545 |  | $ | 1,741 |
Restructuring charges |  |  | 307 |  |  | — |  |  | 28 |
General and administrative |  |  | 5,951 |  |  | 5,113 |  |  | 2,666 |
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Stock-based compensation expense included in operating expenses |  | $ | 8,397 |  | $ | 7,658 |  | $ | 4,435 |
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Schedule of assumptions used to estimate the fair value of stock options granted |
|  | 2015 |  | 2014 |  | 2013
Dividend yield |  | 0% |  | 0% |  | 0%
Expected volatility range |  | 0.874 to 0.884 |  | 0.898 to 0.922 |  | 0.742 to 0.792
Risk-free interest rate range |  | 1.68% to 1.71% |  | 1.64% to 1.92% |  | 0.80% to 1.97%
Expected term |  | 5.5 yrs |  | 5.5 yrs |  | 6 yrs
Schedule of assumptions used to estimate the fair value of employee stock purchases under the Purchase Plans |
|  | 2015 |  | 2014 |  | 2013
Dividend yield |  | 0% |  | 0% |  | 0%
Expected volatility range |  | 0.654 to 1.392 |  | 0.835 to 1.666 |  | 0.506 to 1.391
Risk-free interest rate range |  | 0.11% to 0.28% |  | 0.06% to 0.15% |  | 0.09% to 0.21%
Expected term range |  | 6 mos to 12 mos |  | 6 mos to 12 mos |  | 6 mos to 12 mos
Schedule of common stock reserved for future issuance | Common stock reserved for future issuance as of December 31, 2015 is as follows:
Outstanding stock options |  |  | 17,205,683 |
Options and awards available for grant |  |  | 12,054,916 |
Employee stock purchase plan |  |  | 942,365 |
Warrants outstanding |  |  | 537,893 |
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Total |  |  | 30,740,857 |
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