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Note 7 - Stockholders' Equity and Stock-based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2025
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 |  |  |  |
Outstanding as of December 31, 2024 |  |  | 4,463,028 |  |  | $ | 20.15 |  |  |  | 7.61 |  |  | $ | 288,000 |
Options granted |  |  | 1,655,000 |  |  |  | 1.68 |  |  |  |  |  |  |  |  |
Options exercised |  |  | (225,209 | ) |  |  | 1.51 |  |  |  |  |  |  |  |  |
Options forfeited/canceled |  |  | (1,735,725 | ) |  |  | 17.27 |  |  |  |  |  |  |  |  |
Outstanding as of December 31, 2025 |  |  | 4,157,094 |  |  |  | 15.01 |  |  |  | 8.19 |  |  | $ | 696,000 |
Vested and expected to vest at December 31, 2025 |  |  | 4,157,094 |  |  |  | 15.01 |  |  |  | 8.19 |  |  | $ | 696,000 |
Exercisable at December 31, 2025 |  |  | 1,557,052 |  |  | $ | 20.18 |  |  |  | 6.82 |  |  | $ | 45,000 |
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 |  |  | $ | 0.95 |  |  |  | 34,000 |  |  |  | 2.7 |  |  | $ | 0.95 |  |  |  | 34,000 |  |  | $ | 0.95 |
$ | 1.44 |  |  | $ | 1.44 |  |  |  | 1,067,000 |  |  |  | 9.3 |  |  | $ | 1.44 |  |  |  | — |  |  | $ | — |
$ | 1.59 |  |  | $ | 5.46 |  |  |  | 844,520 |  |  |  | 7.0 |  |  | $ | 2.62 |  |  |  | 393,212 |  |  | $ | 3.14 |
$ | 8.12 |  |  | $ | 26.91 |  |  |  | 1,360,782 |  |  |  | 8.1 |  |  | $ | 23.50 |  |  |  | 824,903 |  |  | $ | 22.70 |
$ | 27.42 |  |  | $ | 77.00 |  |  |  | 850,792 |  |  |  | 8.3 |  |  | $ | 31.30 |  |  |  | 304,937 |  |  | $ | 37.48 |
|  |  |  |  |  |  |  |  | 4,157,094 |  |  |  | 8.2 |  |  | $ | 15.01 |  |  |  | 1,557,052 |  |  | $ | 20.18 |
Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] |
|  | 2025 |  |  | 2024 |  |  | 2023 |
Volatility |  |  | 149% to 162% |  |  |  | 151% to 170% |  |  |  | 152% to 155% |
Risk-free interest rates |  |  | 3.78% to 4.21% |  |  |  | 3.53% to 4.47% |  |  |  | 3.82% to 4.37% |
Expected life of option (in years) |  |  | 7 |  |  |  | 7 |  |  |  | 7 |
Dividend yield |  | zero |  |  | zero |  |  | zero |
Forfeiture rate |  | zero |  |  | 4.37 | % |  | zero |
Weighted average fair value of stock options granted |  | $ | 1.63 |  |  | $ | 25.85 |  |  | $ | 18.21 |
Share-Based Payment Arrangement, Activity [Table Text Block] |
|  | Number of Performance Awards |
Outstanding as of December 31, 2024 |  |  | 7,142 |
Granted |  |  | — |
Vested |  |  | — |
Forfeited/canceled |  |  | — |
Outstanding as of December 31, 2025 |  |  | 7,142 |
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] |
|  | Years ended December 31, |
|  | 2025 |  |  | 2024 |  |  | 2023 |
Research and development |  | $ | 7,159 |  |  | $ | 6,492 |  |  | $ | 2,050 |
General and administrative |  |  | 12,423 |  |  |  | 9,799 |  |  |  | 2,536 |
Total stock-based compensation expense |  | $ | 19,582 |  |  | $ | 16,291 |  |  | $ | 4,586 |

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