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 | Dec-31-15 |
| 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
Operating activities: | | | | | | | | |
Net loss | -35.7 | -28.3 | -19.2 | -44.6 | -27.2 | | | |
Adjustments to reconcile net loss to net cash used in operating activities: | | | | | | | | |
Depreciation expense | 0.6 | 0.4 | 0.3 | 0.1 | 0.0 | | | |
Stock-based compensation expense | 1.6 | 1.1 | 0.5 | 4.3 | 1.4 | 6.9 | 9.2 | 19.3 |
Changes in operating assets and liabilities: | | | | | | | | |
Prepaid expenses and other assets | 0.9 | -0.2 | 0.4 | -0.7 | -2.5 | 0.9 | 0.9 | -1.1 |
Accounts payable | 0.0 | -0.2 | -0.6 | -0.5 | 0.3 | 0.1 | -1.2 | -0.2 |
Accrued expenses and other liabilities | 1.7 | 0.7 | -0.2 | 0.3 | 3.2 | -5.8 | 4.8 | 0.8 |
Interest payable | -0.3 | 0.1 | | | | | | |
Operating lease liabilities | -1.5 | -1.0 | | | | | | |
Cash used in operating activities | -31.1 | -26.0 | -19.0 | -41.2 | -23.6 | -45.6 | -61.7 | -50.3 |
|
Investing activities: | | | | | | | | |
Purchase of property and equipment | -0.6 | -0.1 | -0.1 | -0.4 | 0.0 | -0.2 | -2.6 | -5.2 |
Cash used in investing activities | -0.6 | -0.1 | 0.0 | 4.0 | 1.9 | 17.3 | 8.3 | -38.3 |
|
Financing activities: | | | | | | | | |
Proceeds from the issuance of common stock, net of issuance costs | 8.9 | 33.4 | | 26.7 | 38.8 | | 53.9 | 124.1 |
Proceeds from the issuance of pre-funded warrants, net of issuance costs | 7.3 | | | | | | | |
Cash provided by financing activities | 11.4 | 59.1 | 34.6 | 26.9 | 77.7 | | 54.1 | 125.4 |
|
Supplemental disclosure of cash flow information: | | | | | | | | |
Cash paid for interest | 1.5 | 1.0 | | | | | | |
Cash paid for income taxes | 0.0 | | | | | | | |
Non-cash operating activities: | | | | | | | | |
Lease modification | 0.9 | | | | | | | |
Non-cash investing activities: | | | | | | | | |
Property and equipment in accounts payable | 0.1 | 0.1 | | | | 0.0 | 0.1 | 1.0 |