Stockholders' Equity (Tables)
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12 Months Ended |
Dec. 31, 2018 |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Summary of Stock Option and Restricted Stock Award Activity |
The following summary of stock option and restricted stock award activity, excluding 2014 IN, for the periods presented is as follows: | | | | | | | | | | | | | | | | | | | | Number of Shares Available for Grant | | Number of Shares Underlying Outstanding Options | | Weighted Average Exercise Price Per Share | | Weighted Average Remaining Contractual Life (in Years) | | Aggregate Intrinsic Value | | | | | | | | | | | (In thousands) | Balance as of December 31, 2015 | | 273,948 |
| | 2,381,486 |
| | $ | 18.36 |
| | | | | Additional shares reserved | | 1,131,538 |
| | — |
| | — |
| | | | | Options granted | | (839,800 | ) | | 839,800 |
| | 16.72 |
| | | | | Restricted stock awards granted | | (299,900 | ) | | 299,900 |
| | — |
| | | | | Options exercised | | — |
| | (131,752 | ) | | 10.67 |
| | | | | Options cancelled/forfeited | | 320,084 |
| | (320,084 | ) | | 21.77 |
| | | | | Restricted stock awards forfeited | | 80,333 |
| | (80,333 | ) | | — |
| | | | | Restricted stock awards released | | — |
| | (124,344 | ) | | — |
| | | | | Shares cancelled/retired under 2002/2012 plans | | — |
| | (38,829 | ) | | 8.92 |
| | | | | Net settlement of restricted stock awards for employee taxes | | 23,289 |
| | — |
| | — |
| | | | | Balance as of December 31, 2016 | | 689,492 |
| | 2,825,844 |
| | 17.92 |
| | | | | Additional shares reserved | | 1,145,958 |
| | — |
| | — |
| | | | | Options granted | | (925,525 | ) | | 925,525 |
| | 21.65 |
| | | | | Restricted stock awards granted | | (340,525 | ) | | 340,525 |
| | — |
| | | | | Options exercised | | — |
| | (309,341 | ) | | 12.88 |
| | | | | Options cancelled/forfeited | | 230,734 |
| | (230,734 | ) | | 22.81 |
| | | | | Restricted stock awards forfeited | | 81,905 |
| | (81,905 | ) | | — |
| | | | | Restricted stock awards released | | — |
| | (117,218 | ) | | — |
| | | | | Shares cancelled/retired under 2002/2012 plans | | — |
| | (696 | ) | | 8.94 |
| | | | | Net settlement of restricted stock awards for employee taxes | | 21,010 |
| | — |
| | — |
| | | | | Balance as of December 31, 2017 | | 903,049 |
| | 3,352,000 |
| | 19.29 |
| | | | | Additional shares reserved | | 1,460,643 |
| | — |
| | — |
| | | | | Options granted | | (926,650 | ) | | 926,650 |
| | 28.67 |
| | | | | Restricted stock awards granted | | (339,500 | ) | | 339,500 |
| | — |
| | | | | Options exercised | | — |
| | (293,100 | ) | | 15.45 |
| | | | | Options cancelled/forfeited | | 423,096 |
| | (423,096 | ) | | 25.66 |
| | | | | Restricted stock awards forfeited | | 101,218 |
| | (101,218 | ) | | — |
| | | | | Restricted stock awards released | | — |
| | (198,213 | ) | | — |
| | | | | Net settlement of restricted stock awards for employee taxes | | 59,904 |
| | — |
| | — |
| | | | | Balance as of December 31, 2018 | | 1,681,760 |
| | 3,602,523 |
| | $ | 21.63 |
| | 7.13 | | $ | 8,071 |
| Exercisable as of December 31, 2018 | | | | 1,853,452 |
| | $ | 19.47 |
| | 6.11 | | $ | 7,274 |
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Schedule of Stock Options and Restricted Stock Exercise Price Range |
The following table summarizes information with respect to stock options outstanding and currently exercisable as of December 31, 2018: | | | | | | | | | | Options Outstanding | | Options Exercisable | Exercise Price | Number of Options | | Weighted-Average Remaining Contractual Life (In Years) | | $0.45 - 9.15 | 430,333 |
| | 4.41 | | 430,333 |
| $13.35 - 16.23 | 406,389 |
| | 6.44 | | 335,718 |
| $16.3 - 18.37 | 423,042 |
| | 7.16 | | 298,893 |
| $18.7 - 19.7 | 391,547 |
| | 8.09 | | 180,069 |
| $19.91 - 24.96 | 442,443 |
| | 8.48 | | 167,039 |
| $25.3 - 29.15 | 656,654 |
| | 8.52 | | 176,065 |
| $29.4 - 32.22 | 587,175 |
| | 6.88 | | 360,415 |
| $32.25 - 34.08 | 51,000 |
| | 8.53 | | 9,399 |
| $35.95 - 35.95 | 10,500 |
| | 8.94 | | 2,625 |
| $36.32 - 36.32 | 206,250 |
| | 6.95 | | 154,687 |
| | 3,605,333 |
| | | | 2,115,243 |
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|
Nonvested Restricted Stock Shares Activity |
The following table summarizes information with respect to restricted stock awards outstanding as of December 31, 2018: | | | | | | | | | | | | | Number of Awards Available for Grant | | Weighted-Average Grant-Date Fair Value | | Aggregate Intrinsic Value | | | | | | (In thousands) | Outstanding as of December 31, 2015 | 315,600 |
| | $ | 25.67 |
| | — |
| Granted | 314,900 |
| | 17.16 |
| | — |
| Vested | (133,938 | ) | | 26.41 |
| | — |
| Forfeited | (80,333 | ) | | 20.35 |
| | — |
| Outstanding as of December 31, 2016 | 416,229 |
| | 20.02 |
| | — |
| Granted | 435,525 |
| | 22.08 |
| | — |
| Vested | (130,562 | ) | | 23.25 |
| | — |
| Forfeited | (81,905 | ) | | 19.32 |
| | — |
| Outstanding as of December 31, 2017 | 639,287 |
| | 20.86 |
| | — |
| Granted | 373,500 |
| | 28.37 |
| | — |
| Vested | (235,307 | ) | | 20.25 |
| | — |
| Forfeited | (172,468 | ) | | 24.83 |
| | — |
| Outstanding as of December 31, 2018 | 605,012 |
| | $ | 24.61 |
| | $ | 14,888 |
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Schedule of Stock-based Compensation Expense |
Stock-based compensation expense related to options and awards for employees and non-employees and shares purchased under the 2014 ESPP by employees, was allocated as follows: | | | | | | | | | | | | | (in thousands) | Year Ended December 31, | 2018 | | 2017 | | 2016 | Research and development | $ | 7,480 |
| | $ | 5,902 |
| | $ | 5,557 |
| General and administrative | 8,793 |
| | 7,328 |
| | 6,396 |
| Total stock-based compensation expense | $ | 16,273 |
| | $ | 13,230 |
| | $ | 11,953 |
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Schedule of Reserved Shares of Common Stock |
The Company had reserved shares of common stock, on an as if converted basis, for issuance as follows: | | | | | | | December 31, 2018 | Issuances under stock incentive plans | | 1,681,760 |
| Issuances upon exercise of common stock warrants | | 34,113 |
| Issuances under employee stock purchase plan | | 1,178,940 |
| Issuances under inducement plan | | 157,861 |
| Total | | 3,052,674 |
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Employee Stock Option |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Fair Value Assumptions |
The fair value of the employee and non-employee director stock options was estimated using the Black-Scholes option-pricing model with the following weighted-average assumptions: | | | | | | | | | | | Year Ended December 31, | | 2018 | | 2017 | | 2016 | Expected term (in years) | 6.0 |
| | 6.0 |
| | 6.0 |
| Expected volatility | 60.2 | % | | 67.7 | % | | 61.9 | % | Risk-free interest rate | 2.7 | % | | 2.1 | % | | 1.4 | % | Expected dividend rate | — | % | | — | % | | — | % |
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Non-employee Stock Options |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
Fair Value Assumptions |
| | | | | | | | | | | Year Ended December 31, | | 2018 | | 2017 | | 2016 | Expected term (in years) | 5.5 |
| | 8.9 |
| | 7.3 |
| Expected volatility | 59.4 | % | | 67.9 | % | | 68.9 | % | Risk-free interest rate | 2.8 | % | | 2.3 | % | | 1.7 | % | Expected dividend rate | — | % | | — | % | | — | % |
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Employee Stock Purchase Plan |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
Schedule of Stock-based Compensation Expense |
The fair value of the option component of the shares purchased under the 2014 ESPP was estimated using the Black-Scholes option-pricing model with the following weighted-average assumptions: | | | | | | | | | | | Year Ended December 31, | | 2018 | | 2017 | | 2016 | Expected term (in years) | 0.5 |
| | 0.5 |
| | 0.5 |
| Expected volatility | 50.9 | % | | 59.2 | % | | 72.0 | % | Risk-free interest rate | 1.9 | % | | 0.9 | % | | 0.4 | % | Expected dividend rate | — | % | | — | % | | — | % |
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2014 Inducement Plan |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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Summary of Stock Option and Restricted Stock Award Activity |
The following table summarizes the stock option activity for the 2014 IN is as follows: | | | | | | | | | | | | | | | | | | | | Number of Shares Available for Grant | | Number of Shares Underlying Outstanding Options and Awards | | Weighted Average Exercise Price Per Share | | Weighted Average Remaining Contractual Life (in Years) | | Aggregate Intrinsic Value | | | | | | | | | | | (In thousands) | Balance as of December 31, 2015 | | 449,889 |
| | 354,219 |
| | $ | 31.46 |
| | | | | Options granted | | (110,000 | ) | | 110,000 |
| | 18.37 |
| | | | | Restricted stock awards granted | | (15,000 | ) | | 15,000 |
| | — |
| | | | | Option forfeitures | | 88,594 |
| | (88,594 | ) | | 22.97 |
| | | | | Restricted stock awards released | | — |
| | (9,594 | ) | | — |
| | | | | Net settlement of restricted stock awards for employee taxes | | 3,604 |
| | — |
| | — |
| | | | | Balance as of December 31, 2016 | | 417,087 |
| | 381,031 |
| | 29.43 |
| | | | | Options granted | | (35,000 | ) | | 35,000 |
| | 24.40 |
| | | | | Restricted stock awards granted | | (95,000 | ) | | 95,000 |
| | — |
| | | | | Restricted stock awards released | | — |
| | (13,344 | ) | | — |
| | | | | Net settlement of restricted stock awards for employee taxes | | 5,009 |
| | — |
| | — |
| | | | | Balance as of December 31, 2017 | | 292,096 |
| | 497,687 |
| | 28.96 |
| | | | | Options granted | | (210,000 | ) | | 210,000 |
| | 26.71 |
| | | | | Restricted stock awards granted | | (34,000 | ) | | 34,000 |
| | — |
| | | | | Option forfeitures | | 25,521 |
| | (25,521 | ) | | 24.40 |
| | | | | Restricted stock award forfeitures | | 71,250 |
| | (71,250 | ) | | — |
| | | | | Restricted stock awards released | | — |
| | (37,094 | ) | | — |
| | | | | Net settlement of restricted stock awards for employee taxes | | 12,994 |
| | — |
| | — |
| | | | | Balance as of December 31, 2018 | | 157,861 |
| | 607,822 |
| | $ | 28.32 |
| | 7.82 | | $ | 194 |
| Exercisable as of December 31, 2018 | | | | 261,791 |
| | $ | 29.34 |
| | 6.67 | | $ | 133 |
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