| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | S-1/A |
| CASH FLOWS FROM OPERATING ACTIVITIES: | | | | | | | |
| Net loss | | | -28.9 | -31.9 | -29.5 | -18.8 | |
| Adjustments to reconcile net loss to net cash used in operating activities: | | | | | | | |
| Depreciation | | | 0.3 | 0.2 | 0.2 | 0.2 | |
| Stock-based compensation | | | 0.7 | 0.4 | 0.2 | 0.3 | |
| Changes in operating assets and liabilities: | | | | | | | |
| Accounts receivable | | | 0.7 | -0.3 | -0.5 | 0.0 | |
| Prepaid expenses and other current assets | | | -0.2 | 0.7 | -0.4 | -0.3 | |
| Accounts payable | | | 0.1 | 0.7 | 0.4 | -0.6 | |
| Accrued expenses | | | -1.7 | -0.7 | 2.4 | 0.0 | |
| Net cash used in operating activities | -19.1 | -25.3 | -28.6 | -30.7 | -25.3 | -21.4 | |
| |
| CASH FLOWS FROM INVESTING ACTIVITIES: | | | | | | | |
| Purchase of property and equipment | 0.1 | 0.0 | -0.3 | -0.1 | -0.2 | -0.1 | |
| Net cash used in investing activities | -0.1 | 0.0 | -0.3 | 14.1 | -14.2 | -0.1 | |
| |
| CASH FLOWS FROM FINANCING ACTIVITIES: | | | | | | | |
| Proceeds from issuance of common stock | 3.6 | 32.8 | 28.5 | 13.8 | 37.1 | | |
| Payments of long-term debt | 0.1 | 0.0 | | | | | |
| Proceeds from private offering of common stock | 3.6 | 32.8 | 28.5 | 13.8 | 37.1 | | |
| Net cash provided by financing activities | 17.0 | 23.3 | 36.8 | 13.8 | 41.0 | 24.0 | |