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Equity Incentive Plans (Tables) | 9 Months Ended
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Sep. 30, 2020
Share-based Payment Arrangement [Abstract] |
Summary of Activity Related to Stock Option Awards | A summary of the activity related to stock option awards during the nine months ended September 30, 2020 is as follows:
| Shares Subject to Options |  | Weighted-Average Exercise Price per Share |  | Weighted-Average Remaining Contractual Term (in years) |  | Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2020 | 3,039,880 |  |  | $ | 29.40 |  |  |  |  |
Granted | 461,425 |  |  | $ | 18.30 |  |  |  |  |
Exercises | (91,146) |  |  | $ | 4.06 |  |  |  |  |
Forfeitures and cancellations | (534,096) |  |  | $ | 37.54 |  |  |  |  |
Outstanding at September 30, 2020 | 2,876,063 |  |  | $ | 26.91 |  |  | 7.47 |  | $ | 6,747 |
Exercisable at September 30, 2020 | 1,355,530 |  |  | $ | 27.48 |  |  | 5.64 |  | $ | 6,365 |
Summary of Weighted Average Assumptions in Stock Option Valuations | The estimated fair values of stock option awards granted to employees were determined on the date of grant using the Black-Scholes option valuation model with the following weighted-average assumptions:
| Nine Months Ended September 30, |
| 2020 |  | 2019 |  |  |
Risk-free interest rate |  | 0.5 |  | % |  |  | 2.5 |  | % |  |  |  |
Expected volatility |  | 90.5 |  | % |  |  | 68.4 |  | % |  |  |  |
Expected dividend yield |  | — |  | % |  |  | — |  | % |  |  |  |
Expected term (in years) |  | 6.25 |  |  |  | 6.25 |  |  |  |  |
Weighted-average grant date fair value per share | $ | 13.88 |  |  |  | $ | 43.08 |  |  |  |  |  |
Summary of Non-cash Stock-based Compensation Expense | Total non-cash stock-based compensation expense for all stock awards that was recognized in the consolidated statements of operations and comprehensive loss is as follows:
| Three Months Ended September 30, |  | Nine Months Ended September 30,
(in thousands) | 2020 |  | 2019 |  | 2020 |  | 2019
Research and development | $ | 926 |  |  | $ | 1,580 |  |  | $ | 3,030 |  |  | $ | 4,469 |
General and administrative | 1,879 |  |  | 1,564 |  |  | 5,491 |  |  | 5,185 |
Total | $ | 2,805 |  |  | $ | 3,144 |  |  | $ | 8,521 |  |  | $ | 9,654 |

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- Definition Tabular disclosure of cost recognized for award under share-based payment arrangement by plan. Includes, but is not limited to, related tax benefit. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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