| In millions, except per share items | Jun-30-23 | Mar-31-23 | Dec-31-22 | Sep-30-22 | Jun-30-22 | Mar-31-22 | Dec-31-21 | Sep-30-21 |
| | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q | 10-K | 10-Q |
| Operating expenses | | | | | | | | |
| Research and development | 14.2 | 9.6 | 17.2 | 15.6 | 9.0 | 7.9 | 7.1 | 6.3 |
| General and administrative | 9.6 | 8.2 | 6.9 | 7.5 | 10.6 | 10.1 | 7.5 | 4.5 |
| Total operating expenses | 23.7 | 17.8 | 24.2 | 23.1 | 19.6 | 18.0 | 14.6 | 10.8 |
| Loss from operations | -23.7 | -17.8 | -24.2 | -23.1 | -19.6 | -18.0 | -14.6 | -10.8 |
| Other income (expense), net | 0.8 | 1.3 | 2.2 | 1.2 | 0.1 | 0.0 | 0.0 | 0.0 |
| Net loss | -22.9 | -16.5 | -21.9 | -21.9 | -19.5 | -18.0 | -14.6 | -10.8 |
| |
| Other comprehensive income (loss) | | | | | | | | |
| Foreign currency translation adjustment | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | | | |
| Unrealized gain (loss) on marketable securities | 0.0 | | | | | | | |
| Comprehensive loss | -22.9 | -16.5 | -21.9 | -21.9 | -19.5 | -18.0 | -14.6 | -10.8 |
| |
| Shares used in calculating net loss per common share - basic (in shares) | 238.3 | 225.5 | 214.6 | 216.6 | 215.9 | 205.7 | 195.0 | 198.8 |
| Shares used in calculating net loss per common share - diluted (in shares) | 238.3 | 225.5 | 214.6 | 216.6 | 215.9 | 205.7 | 195.0 | 198.8 |
| |
| Net loss per share of common stock - basic (in USD per share) | ($0.10) | ($0.07) | ($0.10) | ($0.10) | ($0.09) | ($0.09) | ($0.07) | ($0.05) |
| Net loss per share of common stock - diluted (in USD per share) | ($0.10) | ($0.07) | ($0.10) | ($0.10) | ($0.09) | ($0.09) | ($0.07) | ($0.05) |