Stockholders' Equity (Tables)
|
12 Months Ended |
Dec. 31, 2020 |
|---|
| Stockholders' Equity |
|
| Summary of restricted stock award activity |
Certain employees, directors and consultants have been awarded restricted stock. The restricted stock vesting consists of milestone and time-based vesting. The following table summarizes restricted stock award activity for the year ended December 31, 2020 and 2019:
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|
|
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|
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|
|
|
|
Weighted Average |
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|
|
|
Grant Date Fair |
|
|
Number of Shares |
|
Value |
Nonvested at December 31, 2018 |
|
2,932,106 |
|
$ |
4.22 |
Granted |
|
800,652 |
|
|
3.33 |
Forfeited |
|
(21,000) |
|
|
3.16 |
Vested |
|
(407,919) |
|
|
1.96 |
Nonvested at December 31, 2019 |
|
3,303,839 |
|
$ |
4.29 |
Granted |
|
1,117,340 |
|
|
2.39 |
Vested |
|
(551,283) |
|
|
5.23 |
Non-vested at December 31, 2020 |
|
3,869,896 |
|
$ |
3.61 |
|
| Summary of stock option award activity |
The following table summarizes stock option award activity for the year ended December 31, 2020 and 2019:
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|
|
|
|
|
|
|
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|
|
|
|
Weighted Average |
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|
|
|
|
|
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Remaining |
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|
|
|
Weighted Average |
|
Contractual Life |
|
|
Stock Options |
|
Exercise Price |
|
(in years) |
Outstanding as of December 31, 2018 |
|
60,000 |
|
$ |
5.43 |
|
8.09 |
Granted |
|
100,000 |
|
|
2.56 |
|
|
Outstanding as of December 31, 2019 |
|
160,000 |
|
$ |
3.64 |
|
8.56 |
Granted |
|
60,000 |
|
|
2.04 |
|
|
Outstanding as of December 31, 2020 |
|
220,000 |
|
$ |
3.20 |
|
8.04 |
Vested and exercisable as of December 31, 2020 |
|
25,000 |
|
$ |
1.87 |
|
8.82 |
|
| Summary of stock options granted |
The Company used the Black-Scholes option pricing model for determining the estimated fair value of stock-based compensation related to stock options. The table below summarizes the assumptions used:
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|
|
|
|
|
|
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For the Years Ended December 31, |
|
|
|
2020 |
|
2019 |
|
Risk-free interest rate |
|
0.65% - 1.02% |
|
1.77% - 2.72% |
|
Expected dividend yield |
|
— |
|
— |
|
Expected term in years |
|
10.0 |
|
10.0 |
|
Expected volatility |
|
101.27% - 104.60% |
|
99.84% - 103.79% |
|
|
| Summary of warrant activities |
A summary of warrant activities for year ended December 31, 2020 and 2019 is presented below:
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|
|
|
|
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|
|
|
|
Weighted Average |
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|
|
|
|
|
|
Remaining |
|
|
|
|
Weighted Average |
|
Contractual Life |
|
|
Warrants |
|
Exercise Price |
|
(in years) |
Outstanding as of December 31, 2018 |
|
4,280,972 |
|
$ |
6.69 |
|
2.33 |
Exercised |
|
(73,525) |
|
|
— |
|
|
Outstanding as of December 31, 2019 |
|
4,207,447 |
|
$ |
6.81 |
|
1.25 |
Exercised |
|
(102,742) |
|
|
0.13 |
|
|
Expired |
|
(4,047,190) |
|
|
7.00 |
|
|
Outstanding as of December 31, 2020 |
|
57,515 |
|
$ |
5.39 |
|
1.22 |
|
| Summary of stock-based compensation expense |
The following table summarizes stock-based compensation expense for the years ended December 31, 2020 and 2019 (in thousands).
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|
|
|
|
|
|
|
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For the year ended December 31, |
|
|
2020 |
|
2019 |
Research and development |
|
$ |
617 |
|
$ |
707 |
General and administrative |
|
|
2,163 |
|
|
2,414 |
Total stock-based compensation expense |
|
$ |
2,780 |
|
$ |
3,121 |
|