XML 52 R27.htm IDEA: XBRL DOCUMENT
v3.24.0.1

Note 7 - Stockholders' Equity and Stock-based Compensation Expense (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2023
Notes Tables |
Share-Based Payment Arrangement, Option, Activity [Table Text Block] |
|  |  |  |  |  | Weighted Average |  |  | Weighted Average |  |  |  |  |
|  | Number of |  |  | Weighted Average |  |  | Remaining Contractual |  |  | Aggregate Intrinsic Value |
|  | Options |  |  | Exercise Price |  |  | Term in Years |  |  | in Millions |
Outstanding as of December 31, 2022 |  |  | 2,529,448 |  |  | $ | 12.13 |  |  |  | 3.94 |  |  | $ | 49.60 |
Options granted |  |  | 1,162,000 |  |  |  | 18.91 |  |  |  |  |  |  |  |  |
Options exercised |  |  | (602,420 | ) |  |  | 8.38 |  |  |  |  |  |  |  |  |
Options forfeited/canceled |  |  | (49,999 | ) |  |  | 32.59 |  |  |  |  |  |  |  |  |
Outstanding as of December 31, 2023 |  |  | 3,039,029 |  |  |  | — |  |  |  | — |  |  | $ | — |
Vested and expected to vest at December 31, 2023 |  |  | 3,039,029 |  |  |  | 15.13 |  |  |  | 6.21 |  |  | $ | 30.28 |
Exercisable at December 31, 2023 |  |  | 1,836,174 |  |  | $ | 11.09 |  |  |  | 3.98 |  |  | $ | 26.18 |
Share-Based Payment Arrangement, Option, Exercise Price Range [Table Text Block] |
|  |  |  |  |  |  |  | Options outstanding |  |  | Options exercisable |
|  |  |  |  |  |  |  |  |  |  |  | Weighted |  |  |  |  |  |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |  |  |  |  | average |  |  | Weighted |  |  |  |  |  |  | Weighted |
|  |  |  |  |  |  |  | Number of |  |  | remaining |  |  | average |  |  | Number of |  |  | average |
Range of exercise prices |  |  | outstanding |  |  | contractual |  |  | exercise |  |  | vested |  |  | exercise |
From |  |  | To |  |  | options |  |  | life (in years) |  |  | price |  |  | options |  |  | price |
$ | 0.95 |  |  | $ | 3.24 |  |  |  | 804,834 |  |  |  | 4.8 |  |  | $ | 2.17 |  |  |  | 804,834 |  |  | $ | 2.17 |
$ | 4.09 |  |  | $ | 13.02 |  |  |  | 656,230 |  |  |  | 2.9 |  |  | $ | 8.33 |  |  |  | 647,167 |  |  | $ | 8.34 |
$ | 14.21 |  |  | $ | 16.94 |  |  |  | 62,634 |  |  |  | 1.9 |  |  | $ | 16.00 |  |  |  | 62,634 |  |  | $ | 16.00 |
$ | 17.54 |  |  | $ | 17.54 |  |  |  | 800,000 |  |  |  | 9.8 |  |  | $ | 17.54 |  |  |  | 44,442 |  |  | $ | 17.54 |
$ | 21.11 |  |  | $ | 77.00 |  |  |  | 715,331 |  |  |  | 7.2 |  |  | $ | 33.20 |  |  |  | 277,097 |  |  | $ | 41.29 |
|  |  |  |  |  |  |  |  | 3,039,029 |  |  |  | 6.2 |  |  | $ | 15.13 |  |  |  | 1,836,174 |  |  | $ | 11.09 |
Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] |
|  | 2023 |  |  | 2022 |  |  | 2021 |
Volatility |  |  | 152% to 155% |  |  |  | 151% to 154% |  |  |  | 147% to 151% |
Risk-free interest rates |  |  | 3.82% to 4.37% |  |  |  | 1.98% to 3.69% |  |  |  | 1.12% to 1.42% |
Expected life of option (in years) |  |  | 7 |  |  |  | 7 |  |  |  | 7 |
Dividend yield |  | zero |  |  | zero |  |  | zero |
Forfeiture rate |  | zero |  |  | zero |  |  | zero |
Weighted average fair value of stock options granted |  | $ | 18.21 |  |  | $ | 35.16 |  |  | $ | 65.83 |
Share-Based Payment Arrangement, Activity [Table Text Block] |
|  | Number of Performance Awards |
Outstanding as of December 31, 2022 |  |  | 7,142 |
Granted |  |  | — |
Vested |  |  | — |
Forfeited/canceled |  |  | — |
Outstanding as of December 31, 2023 |  |  | 7,142 |
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] |
|  | Years ended December 31, |
|  | 2023 |  |  | 2022 |  |  | 2021 |
Research and development |  | $ | 2,050 |  |  | $ | 1,631 |  |  | $ | 1,302 |
General and administrative |  |  | 2,536 |  |  |  | 435 |  |  |  | 457 |
Total stock-based compensation expense |  | $ | 4,586 |  |  | $ | 2,066 |  |  | $ | 1,759 |

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 -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
Name: | us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of activity for award under share-based payment arrangement. Includes, but is not limited to, outstanding award at beginning and end of year, granted, exercised, forfeited, and weighted-average grant date fair value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -SubTopic 10 -Topic 718 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (e) -SubTopic 10 -Topic 718 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
Name: | us-gaap_ScheduleOfShareBasedCompensationActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of option exercise prices, by grouped ranges, including the upper and lower limits of the price range, the number of shares under option, weighted average exercise price and remaining contractual option terms. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
Name: | us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTextBlock
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 -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -SubTopic 10 -Topic 718 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (e) -SubTopic 10 -Topic 718 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + 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 -Topic 718 -SubTopic 10 -Subparagraph (f)(2) -Name Accounting Standards Codification -Paragraph 2 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
Name: | us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

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