Preferred Stock, Common Stock and Stockholders' Equity (Tables)
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12 Months Ended |
Dec. 31, 2015 |
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| Equity [Abstract] |
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| Summary of Warrants Activity |
A summary of the Company’s warrant activity is as follows:
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Weighted |
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Weighted |
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Average |
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Average |
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Remaining |
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Exercise |
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Contractual |
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Shares |
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Price |
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Term (Years) |
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Outstanding at December 31, 2014 |
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118,881 |
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$ |
16.73 |
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5.35 |
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Issued |
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— |
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— |
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— |
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Exercised |
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— |
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— |
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— |
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Expired/Forfeited |
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— |
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— |
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— |
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Outstanding at December 31, 2015 |
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118,881 |
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$ |
16.73 |
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4.35 |
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| Summary of Stock Option Activity |
A summary of the Company’s stock option activity under the 2007 Plan and 2013 Plan is as follows:
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Weighted |
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Weighted |
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Average |
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Average |
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Remaining |
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Exercise |
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Contractual |
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Aggregate |
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Shares |
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Price |
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Term (Years) |
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Intrinsic Value |
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Outstanding at December 31, 2014 |
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683,500 |
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$ |
7.67 |
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8.45 |
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$ |
649,000 |
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Granted |
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354,000 |
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$ |
6.25 |
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9.20 |
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— |
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Exercised |
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— |
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— |
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— |
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— |
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Expired/Forfeited |
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— |
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— |
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— |
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— |
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Outstanding at December 31, 2015 |
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1,037,500 |
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$ |
7.19 |
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8.04 |
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$ |
342,200 |
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Vested and expected to vest at December 31, 2015 |
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1,037,500 |
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$ |
7.19 |
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8.04 |
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$ |
342,200 |
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Exercisable at December 31, 2015 |
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530,079 |
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$ |
6.80 |
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7.50 |
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$ |
342,200 |
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| Summary of Nonvested Options Activity |
The Company had the following nonvested options under the 2007 Plan and 2013 Plan:
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Shares |
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Weighted
Average
Grant Date
Fair Value
Per Share |
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Nonvested at December 31, 2014 |
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424,419 |
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$ |
9.02 |
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Granted |
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354,000 |
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$ |
4.03 |
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Vested |
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(270,998 |
) |
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$ |
8.07 |
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Expired/Forfeited |
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— |
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— |
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Nonvested at December 31, 2015 |
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507,421 |
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$ |
7.60 |
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| Summary of Estimated Fair Value of Stock Option Award |
The estimated fair value of each option award granted was determined on the date of grant using the Black-Scholes option-pricing valuation model with the following weighted-average assumptions for options grants during the two years ended December 31, 2015:
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Year Ended December 31, |
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2015 |
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2014 |
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Risk free interest rate |
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1.50% - 1.87% |
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1.66% - 1.77% |
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Expected option term |
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5.5 - 6.0 years |
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5.5 - 6.0 years |
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Expected volatility of common stock |
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71.99% - 76.74% |
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71.06% - 73.21% |
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Expected dividend yield |
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0.0% |
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0.0% |
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| Summary of Estimated Fair Value of Employee Stock Purchase Plan Award |
The estimated fair value of the shares to be acquired under the ESPP was determined on the initiation date of each six month purchase period using the Black-Scholes option-pricing valuation model with the following weighted-average assumptions for ESPP shares to be purchased during the year ended December 31, 2015 and 2014:
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Year Ended December 31, |
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2015 |
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2014 |
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Risk free interest rate |
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0.08% - 0.26% |
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0.05% - 0.08% |
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Expected term |
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6 months |
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6 months |
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Expected volatility of common stock |
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62.91% - 69.64% |
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69.32% - 73.21% |
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Expected dividend yield |
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0.0% |
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0.0% |
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| Summary of Recognized Non-Cash Stock-Based Compensation Expense |
The Company recognized non-cash stock-based compensation expense to employees and directors in its research and development and its general and administrative functions as follows:
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Year Ended December 31, |
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2015 |
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2014 |
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Research and development |
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$ |
579,078 |
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$ |
410,150 |
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General and administrative |
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925,278 |
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691,937 |
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Total stock-based compensation expense |
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$ |
1,504,356 |
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$ |
1,102,087 |
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| Summary of Common Stock Reserved for Future Issuance |
Common stock reserved for future issuance consists of the following at December 31, 2015 and 2014:
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December 31, |
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2015 |
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2014 |
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Stock options issued and outstanding |
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1,037,500 |
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683,500 |
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Authorized for future option grants |
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78,854 |
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188,370 |
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Warrants to purchase common stock |
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118,881 |
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118,881 |
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Authorized for employee stock purchase plan |
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41,530 |
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52,706 |
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Total common stock reserved for future issuance |
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1,276,765 |
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1,043,457 |
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