| 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 |
| Assets | | | | | | | | |
| Current assets: | | | | | | | | |
| Cash and cash equivalents | 15.7 | 16.8 | 28.4 | 32.0 | 36.0 | 42.7 | 45.7 | 47.5 |
| Prepaid expenses and other current assets | 7.1 | 8.8 | 7.6 | 0.5 | 0.6 | 0.6 | 0.3 | 0.2 |
| Total current assets | 22.8 | 25.5 | 36.0 | 32.5 | 36.5 | 43.3 | 46.0 | 47.7 |
| Total assets | 22.8 | 25.5 | 36.0 | 32.5 | 36.5 | 43.3 | 46.0 | 47.7 |
| |
| Liabilities and Stockholders' Equity | | | | | | | | |
| Current liabilities: | | | | | | | | |
| Accounts payable | 1.2 | 4.2 | 4.0 | 1.8 | 0.9 | 0.9 | 0.7 | 0.3 |
| Accrued expenses | 0.9 | 1.3 | 3.7 | 0.7 | 0.4 | 0.3 | 0.8 | 0.8 |
| Total current liabilities | 2.1 | 5.4 | 7.7 | 2.5 | 1.3 | 1.3 | 1.5 | 1.1 |
| Total liabilities | 2.1 | 5.4 | 7.7 | 2.5 | 1.3 | 1.3 | 1.5 | 1.1 |
| |
| Commitments and contingencies (Note 7) | | | | | | | | |
| Stockholders' equity: | | | | | | | | |
| Preferred stock - $0.0001 par value, 2,000,000 shares authorized and 0 shares issued and outstanding | | | | | | | | |
| Common stock | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Additional paid-in capital | 94.1 | 83.9 | 82.4 | 80.9 | 78.6 | 76.7 | 73.2 | 69.3 |
| Accumulated deficit | -73.3 | -63.8 | -54.1 | -51.0 | -43.3 | -34.6 | -28.7 | -22.8 |
| Total stockholders' equity | 20.7 | 20.1 | 28.3 | 30.0 | 35.2 | 42.0 | 44.5 | 46.5 |
| Total liabilities and stockholders' equity | 22.8 | 25.5 | 36.0 | 32.5 | 36.5 | 43.3 | 46.0 | 47.7 |