XML 72 R30.htm IDEA: XBRL DOCUMENT
v3.20.1

Stock-Based Compensation (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
Summary of Stock-Based Compensation Expense | Total stock-based compensation expense is recognized for stock-based awards granted to employees and non-employees and has been reported in the Company’s consolidated statements of operations and comprehensive loss as follows:
|  | Year Ended December 31, |
|  | 2019 |  |  | 2018 |  |  | 2017 |
|  | (In thousands) |
Research and development |  | $ | 1,542 |  |  | $ | 1,236 |  |  | $ | 246 |
General and administrative |  |  | 2,152 |  |  |  | 1,557 |  |  |  | 224 |
Total stock-based compensation expense |  | $ | 3,694 |  |  | $ | 2,793 |  |  | $ | 470 |
Summary of Stock Option Activity | The following table summarizes stock option activity under the Plan:
|  | Shares Available for Grant |  |  | Number of Options Outstanding |  |  | Weighted- Average Exercise Price per Option ($) |  |  | Weighted- Average Remaining Contract Term (Years) |  |  | Aggregate Intrinsic Value ($) |
|  | (In thousands) |
Outstanding, December 31, 2018 |  |  | 1,350,582 |  |  |  | 1,122,677 |  |  |  | 11.63 |  |  |  | 9.22 |  |  |  |  |
Shares reserved for issuance |  |  | 1,122,213 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Options granted |  |  | (1,896,527 | ) |  |  | 1,896,527 |  |  |  | 6.28 |  |  |  |  |  |  |  |  |
Restricted stock units granted |  |  | (813,335 | ) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Options exercised |  |  | — |  |  |  | (7,029 | ) |  |  | 0.79 |  |  |  |  |  |  |  |  |
Options forfeited |  |  | 449,375 |  |  |  | (449,375 | ) |  |  | 10.77 |  |  |  |  |  |  |  |  |
Outstanding, December 31, 2019 |  |  | 212,308 |  |  |  | 2,562,800 |  |  |  | 7.85 |  |  |  | 8.84 |  |  |  | 200 |
Exercisable, December 31, 2019 |  |  |  |  |  |  | 461,150 |  |  |  | 11.40 |  |  |  | 7.06 |  |  |  | 37 |
Vested and expected to vest, December 31, 2019 |  |  |  |  |  |  | 2,562,800 |  |  |  | 7.85 |  |  |  | 8.84 |  |  |  | 200 |
Schedule of Assumptions to Estimate Fair Value of Stock Options for Employees and Non-Employees Using Black-Scholes Option Pricing Model | The fair value of stock options for employees and non-employees was estimated using a Black-Scholes option pricing model with the following assumptions:
|  | Year Ended December 31,
|  | 2019 |  | 2018 |  | 2017
Employees: |  |  |  |  |  |
Fair value of common stock |  | $1.27 - $10.66 |  | $8.57 - $15.45 |  | $0.79 - $9.33
Expected term (in years) |  | 5.5 - 6.1 |  | 5.8 - 6.2 |  | 5.9 - 6.2
Expected volatility |  | 92.0% - 104.9% |  | 75.9% - 90.6% |  | 74.4% - 74.5%
Risk-free interest rate |  | 1.4% - 2.6% |  | 2.4% - 3.1% |  | 1.9% - 2.2%
Expected dividend yield |  | 0.0% |  | 0.0% |  | 0.0%
Non-employees: |  |  |  |  |  |
Fair value of common stock |  | $1.23 - $10.26 |  | $8.62 - $15.45 |  | $0.79 - $10.28
Expected term (in years) |  | 7.4 - 10.0 |  | 8.4 - 10.0 |  | 9.4 - 10.0
Expected volatility |  | 89.7% - 99.5% |  | 78.0% - 91.2% |  | 74.6% - 77.0%
Risk-free interest rate |  | 1.7% - 2.8% |  | 2.7% - 3.1% |  | 2.3% - 2.4%
Expected dividend yield |  | 0.0% |  | 0.0% |  | 0.0%
Summary of Restricted Stock Activity | The summary of restricted stock activity and related information follows:
|  | Number of Restricted Shares Outstanding |
Unvested shares — December 31, 2018 |  |  | 1,000 |
Vested |  |  | (1,000 | )
Unvested shares — December 31, 2019 |  |  | — |
Summary of Restricted Stock Units Activity | The summary of restricted stock unit activity and related information follows:
|  | Number of Restricted Stock Units Outstanding |
Unvested shares — December 31, 2018 |  |  | 24,960 |
Granted |  |  | 813,335 |
Vested |  |  | (9,360 | )
Unvested shares — December 31, 2019 |  |  | 828,935 |

X
- References No definition available. + Details
Name: | us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the changes in outstanding nonvested restricted stock shares. + 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 (c) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
Name: | us-gaap_NonvestedRestrictedStockSharesActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- 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=116856206&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfCompensationCostForShareBasedPaymentArrangementsAllocationOfShareBasedCompensationCostsByPlanTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the changes in outstanding nonvested restricted stock units. + 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 (c)(2) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfNonvestedRestrictedStockUnitsActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- 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=116856206&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=116856206&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=116856206&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- 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=116856206&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration