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Equity-Based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2020
Equity-Based Compensation |
Summary of allocation of equity-based compensation | The Company recorded equity-based compensation expense related to all equity-based awards, which was allocated as follows in the consolidated statements of operations and comprehensive loss for the years ended December 31, 2020 and 2019 (in thousands):
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended
​ | ​ | December 31,
​ |  | 2020 |  | 2019
Research and development expense | ​ | $ | 3,554 | ​ | $ | 2,425
General and administrative expense | ​ |  | 7,621 | ​ |  | 5,547
​ | ​ | $ | 11,175 | ​ | $ | 7,972
Summary of restricted common stock activity | ​
​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Weighted
​ | ​ | ​ | ​ | Average Fair
​ | ​ | ​ | ​ | Value per Share
​ |  | Number of Shares |  | at Issuance
Restricted common stock as of December 31, 2019 |  | 302,360 | ​ | $ | 5.77
Granted |  | — | ​ | $ | —
Vested |  | (202,381) | ​ | $ | 5.77
Forfeited |  | (42,010) | ​ | $ | 5.77
Restricted common stock as of December 31, 2020 |  | 57,969 | ​ | $ | 5.77
Summary of stock option activity | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | Weighted | ​ | ​ | ​
​ | ​ | ​ | ​ | Weighted | ​ | Average | ​ | ​ | ​
​ | ​ | Number of | ​ | Average | ​ | Remaining | ​ | Aggregate
​ |  | Shares |  | Exercise Price |  | Contractual Term |  | Intrinsic Value
​ | ​ | ​ | ​ | ​ | ​ | ​ | (in years) | ​ | (in thousands)
Outstanding as of December 31, 2019 |  | 2,401,382 | ​ | $ | 12.63 |  | 8.36 | ​ | $ | 6,523
Granted |  | 2,388,340 | ​ | $ | 16.01 | ​ | ​ | ​ | ​ | ​
Exercised | ​ | (676,649) | ​ | $ | 10.78 | ​ | ​ | ​ | ​ | ​
Cancelled |  | (433,142) | ​ | $ | 14.38 | ​ | ​ | ​ | ​ | ​
Outstanding as of December 31, 2020 |  | 3,679,931 | ​ | $ | 14.96 | ​ | 8.01 | ​ | $ | 123,600
Options exercisable as of December 31, 2020 |  | 900,142 | ​ | $ | 13.72 | ​ | 7.76 | ​ | $ | 31,332
Schedule of fair value assumptions | ​
​ | ​ | ​ | ​ | ​
​ | Year Ended | ​
​ | December 31, | ​
​ | 2020 |  | 2019 | ​
Risk-free interest rate | 0.92 | % | 2.31 | %
Expected dividend yield | 0.0 | % | 0.0 | %
Expected term (years to liquidity) | 6.21 | ​ | 6.20 | ​
Expected volatility | 82.09 | % | 79.50 | %

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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 Disclosure of the number and weighted-average grant date fair value for restricted stock and restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock and restricted stock units that were granted, vested, or forfeited during the year. + References No definition available. + Details
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