XML 55 R31.htm IDEA: XBRL DOCUMENT
v3.23.1

Stock-Based Compensation (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2022
Stock-Based Compensation [Abstract] |
Weighted-Average Assumptions Used for Grants Issued | The following weighted-average assumptions were used for stock options granted during the years ended December 31, 2022 and 2021:
|  | Year ended December 31, |
|  | 2022 |  |  | 2021 |
Weighted average risk-free rate |  |  | 2.52 | % |  |  | 1.09 | %
Weighted average volatility |  |  | 90.49 | % |  |  | 134.64 | %
Dividend yield |  |  | 0 | % |  |  | 0 | %
Expected term |  | 5.79 years |  |  | 6.10 years |
Summarizes of Stock Option Activity | The following table summarizes stock option activity for the years ended December 31, 2022 and 2021 (in thousands except for per-share and remaining contractual life data):
|  | Outstanding Options |  |  | Weighted Average Exercise Price per Share |  |  | Weighted Average Remaining Contractual Life (in years) |  |  | Aggregate Intrinsic Value |
Outstanding January 1, 2021 |  |  | - |  |  | $ | - |  |  |  | - |  |  | $ | - |
Granted |  |  | 199 |  |  |  | 168.04 |  |  |  |  |  |  |  |  |
Cancelled |  |  | - |  |  |  | - |  |  |  |  |  |  |  |  |
Outstanding December 31, 2021 |  |  | 199 |  |  | $ | 168.04 |  |  |  | 9.38 |  |  | $ | - |
Granted |  |  | 287 |  |  |  | 17.29 |  |  |  |  |  |  |  |  |
Cancelled |  |  | (127 | ) |  |  | 140.56 |  |  |  |  |  |  |  |  |
Outstanding December 31, 2022 |  |  | 359 |  |  | $ | 57.18 |  |  |  | 7.57 |  |  | $ | - |
Options vested and exercisable at December 31, 2022 |  |  | 146 |  |  | $ | 109.60 |  |  |  | 4.79 |  |  | $ | - |
Summarizes of RSU Activity | The following table summarizes RSU activity for the years ended December 31, 2022 and 2021 (in thousands except for per-share data):
|  | Outstanding Restricted Stock Units |  |  | Weighted Average Fair Value per Share |
January 1, 2021 |  |  | - |  |  | $ | - |
Granted |  |  | 12 |  |  |  | 276.00 |
December 31, 2021 |  |  | 12 |  |  |  | 276.00 |
Granted |  |  | 55 |  |  |  | 38.60 |
Released |  |  | (3 | ) |  |  | 271.42 |
Cancelled |  |  | (60 | ) |  |  | 61.03 |
December 31, 2022 |  |  | 4 |  |  | $ | 236.36 |
Balance expected to vest at December 31, 2022 |  |  | 4 |  |  |  |  |
RSUs Vested and Settled | The following table shows the number of RSUs that vested and were settled during the year ended December 31, 2022, as well as the number of shares of common stock withheld to cover the withholding taxes and the net shares issued upon settlement (in thousands):
|  | Year ended |
|  | December 31, 2022 |
RSUs vested |  |  | 3 |
Common stock withheld to cover taxes |  |  | (1 | )
Common stock issued |  |  | 2 |
Stock-Based Compensation Expense | For the years ended December 31, 2022 and 2021, the Company recognized stock-based compensation expense as follows (in thousands):
|  | Years ended December 31, |
|  |  | 2022 |  |  |  | 2021 |
Research and development |  | $ | 1,249 |  |  | $ | 1,597 |
General and administrative |  |  | 1,686 |  |  |  | 3,638 |
Total |  | $ | 2,935 |  |  | $ | 5,235 |

X
- Definition Tabular disclosure of the number RSUs vested and settled. + References No definition available. + Details
Name: | erna_ScheduleOfRestrictedStockUnitsVestedAndSettledTableTextBlock
Namespace Prefix: | erna_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

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 allocation of amount expensed and capitalized for award under share-based payment arrangement to statement of income or comprehensive income and statement of financial position. Includes, but is not limited to, corresponding line item in financial statement. + 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 https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types: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 https://asc.fasb.org/extlink&oid=128089324&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 https://asc.fasb.org/extlink&oid=128089324&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 https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types: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 https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- 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
Name: | us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration