Stockholders’ Equity and Stock-Based Compensation (Tables)
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9 Months Ended |
Sep. 30, 2020 |
| Share-based Payment Arrangement [Abstract] |
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| Schedule of Warrant Activity |
A summary of the Company’s warrant activity for the nine months ended September 30, 2020 was as follows: | | | | | | | | | | | | | | | | | | | | | | | | | Shares of Stock under Warrants | | Weighted- Average Exercise Price | | Weighted- Average Remaining Contractual Term | | Aggregate Intrinsic Value | | Outstanding at January 1, 2020 | 24,406,000 | | | $ | 1.76 | | | 4.82 | | $ | 7,933,000 | | | Granted | 95,396,000 | | | 0.22 | | | 4.53 | | | | Exercised | (90,093,000) | | | 0.21 | | | | | 37,150,000 | | | Canceled | — | | | | | | | | Outstanding at September 30, 2020 | 29,709,000 | | | $ | 1.54 | | | 4.11 | | $ | 1,813,000 | | Vested and exercisable at September 30, 2020 | 29,709,000 | | | $ | 1.54 | | | 4.11 | | $ | — | |
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| Summary of Stock Option Activity |
A summary of the Company’s stock option activity under the Company's equity incentive plans for the nine months ended September 30, 2020 was as follows: | | | | | | | | | | | | | | | | | | | | | | | | | Shares of Stock under Stock Options | | Weighted- Average Exercise Price | | Weighted- Average Remaining Contractual Term | | Aggregate Intrinsic Value | | Outstanding at January 1, 2020 | 1,743,000 | | | $ | 5.73 | | | 8.2 | | $ | 4,000 | | | Granted | 4,250,000 | | | 0.67 | | | | | | | Exercised | — | | | — | | | | | $ | — | | | Canceled | (662,000) | | | 3.52 | | | | | | Outstanding at September 30, 2020 | 5,331,000 | | | $ | 1.97 | | | 8.96 | | $ | 353,000 | | Vested and exercisable at September 30, 2020 | 1,119,000 | | | $ | 5.10 | | | 7.31 | | $ | — | |
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| Summary of Recognized Stock-Based Compensation Expense |
The Company recognized stock-based compensation expense for the periods presented were as follows: | | | | | | | | | | | | | | | | | | | | | | | | | | Three Months Ended September 30, | | Nine Months Ended September 30, | | 2020 | | 2019 | | 2020 | | 2019 | | Research and development | $ | 122,000 | | | $ | 59,000 | | | $ | 255,000 | | | $ | 169,000 | | | General and administrative | 325,000 | | | 305,000 | | | 848,000 | | | 821,000 | | | Total stock-based compensation expense | $ | 447,000 | | | $ | 364,000 | | | $ | 1,103,000 | | | $ | 990,000 | |
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| Schedule of Weighted-Average Assumptions in Black -Scholes Option Pricing Model |
The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants during the periods presented were as follows: | | | | | | | | | | | | | | | | | | | | | | | | | Three Months Ended September 30, | | Nine months Ended September 30, | | 2020 | | 2019 | | 2020 | | 2019 | | Risk-free interest rate | 0.4 | % | | 1.8 | % | | 0.8 | % | | 2.4 | % | | Expected volatility | 77.9 | % | | 68.2 | % | | 74.8 | % | | 68.2 | % | | Expected term (in years) | 5.5 | | 6.1 | | 5.9 | | 5.1 | | Expected dividend yield | 0.0 | % | | 0.0 | % | | 0.0 | % | | 0.0 | % |
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