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Stock Option Plans (Tables) | 9 Months Ended
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Sep. 30, 2016
Schedule of Activity under Stock Option Plan | Activity under the Company’s stock option plan is set forth below:
|  |  |  |  |  |  |  | Options Outstanding |
|  | Options Available for Grant |  |  | Options Outstanding |  |  | Weighted- Average Exercise Price Per Share |  |  | Weighted- Average Remaining Contractual Life (years) |  |  | Aggregate Intrinsic Value |
|  |  |  |  |  |  |  |  |  |  |  |  |  | (in thousands) |
Balances at December 31, 2015 |  |  | 147,219 |  |  |  | 833,178 |  |  | $ | 1.33 |  |  |  | 8.56 |  |  |  |  |
Additional options authorized |  |  | 1,697,088 |  |  |  | — |  |  |  |  |  |  |  |  |  |  |  |  |
Options granted |  |  | (774,479 | ) |  |  | 774,479 |  |  |  | 5.55 |  |  |  |  |  |  |  |  |
Options exercised |  |  | — |  |  |  | (111,501 | ) |  |  | 1.28 |  |  |  |  |  |  |  |  |
Balances at September 30, 2016 |  |  | 1,069,828 |  |  |  | 1,496,156 |  |  |  | 3.52 |  |  |  | 8.65 |  |  | $ | 26,347 |
Options exercisable – September 30, 2016 |  |  |  |  |  |  | 338,784 |  |  |  | 1.97 |  |  |  | 7.26 |  |  | $ | 6,490 |
Options vested and expected to vest – September 30, 2016 |  |  |  |  |  |  | 1,481,620 |  |  |  | 3.51 |  |  |  | 8.64 |  |  | $ | 26,100 |
Schedule of Stock-based Compensation Expense for Employees and Non-employees for Stock Options and the 2016 ESPP | Total stock-based compensation expense recognized for both employees and non-employees for stock options and the 2016 ESPP was as follows (in thousands):
|  | Three Months Ended September 30, |  |  | Nine Months Ended September 30, |
|  | 2016 |  |  | 2015 |  |  | 2016 |  |  | 2015 |
Research and development |  | $ | 285 |  |  | $ | 8 |  |  | $ | 360 |  |  | $ | 24 |
General and administrative |  |  | 163 |  |  |  | 14 |  |  |  | 250 |  |  |  | 38 |
Total stock-based compensation expense |  | $ | 448 |  |  | $ | 22 |  |  | $ | 610 |  |  | $ | 62 |
Employee and Director [Member] |
Schedule of Grant-date Fair Value of Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions | The fair value of employee and director stock option awards was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions:
|  | Three Months Ended September 30, |  |  | Nine Months Ended September 30, |
|  | 2016 |  |  | 2015 |  |  | 2016 |  |  | 2015 |
Expected term (in years) |  |  | 4.16 - 5.70 |  |  |  | — |  |  |  | 4.16 - 5.94 |  |  |  | 5.89 |
Expected volatility |  |  | 62.8 | % |  |  | — |  |  |  | 62.5% - 64.8 | % |  |  | 59.8 | %
Risk-free interest rate |  |  | 1.28 | % |  |  | — |  |  |  | 1.27% - 1.38 | % |  |  | 1.57 | %
Dividend yield |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |
Non-employees [Member] |
Schedule of Grant-date Fair Value of Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions | The fair value of the stock options granted is calculated at each reporting date using the Black-Scholes option-pricing model with the following assumptions:
|  | Three Months Ended September 30, |  |  | Nine Months Ended September 30, |
|  | 2016 |  |  | 2015 |  |  | 2016 |  |  | 2015 |
Expected term (in years) |  |  | 5.70 - 7.04 |  |  |  | — |  |  |  | 5.70 - 9.93 |  |  |  | — |
Expected volatility |  |  | 62.8 | % |  |  | — |  |  |  | 62.5% - 62.8 | % |  |  | — |
Risk-free interest rate |  |  | 1.29 | % |  |  | — |  |  |  | 1.29% - 1.36 | % |  |  | — |
Dividend yield |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |

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- Definition Tabular disclosure of the allocation of equity-based compensation costs to a given line item on the balance sheet and income statement for the period. This may include the reporting line for the costs and the amount capitalized and expensed. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 + Details
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- Definition Tabular disclosure of share-based compensation plans that may be presented in a single table for outstanding, vested and expected to vest, and exercisable awards. The information that may be disclosed in this table may include, but is not limited to, number of shares, weighted average exercise price, weighted average remaining contractual life, and aggregate intrinsic value. + References No definition available. + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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