| In millions, except per share items | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 |
| | S-1/A | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Cash flows from operating activities: | | | | | | | | |
| Net Loss | -11.3 | -14.6 | -12.5 | -9.4 | -8.6 | -7.9 | -5.6 | -5.8 |
| Adjustments to reconcile net loss to net cash used in operating activities: | | | | | | | | |
| Depreciation and amortization | 0.1 | 0.2 | 0.2 | 0.3 | 0.3 | 0.2 | 0.1 | 0.1 |
| Stock-based compensation | 0.7 | 1.7 | 2.4 | 3.6 | 2.5 | 2.0 | 1.4 | 0.8 |
| Changes in operating assets and liabilities: | | | | | | | | |
| Accounts receivable | 0.0 | 0.0 | 0.0 | 0.0 | 0.1 | -0.1 | | |
| Prepaid assets and other current assets | -0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Accounts payable | 0.1 | 0.1 | -0.5 | 0.2 | -0.1 | 1.4 | -0.2 | 0.5 |
| Accrued expenses and other current liabilities | 0.5 | 0.4 | 0.5 | 0.6 | 0.2 | 1.0 | | 1.0 |
| Net cash used in operating activities | -2.0 | -6.9 | -5.1 | -3.9 | -5.0 | -3.1 | -3.2 | -2.7 |
| |
| Cash flows from investing activities: | | | | | | | | |
| Purchases of equipment | | 0.0 | 0.0 | 0.0 | -0.2 | -0.4 | -0.2 | 0.0 |
| Net cash provided by (used in) investing activities | 2.5 | 0.0 | 0.0 | 0.0 | -0.2 | -0.5 | -0.2 | 0.0 |
| |
| Cash flows from financing activities: | | | | | | | | |
| Net proceeds from issuance of common stock in at-the-market offering | 0.0 | | | | | | | |
| Net cash provided by financing activities | 5.0 | 6.8 | 4.8 | 4.3 | 5.1 | 3.7 | 3.3 | 2.9 |
| |
| Supplemental cash flow information: | | | | | | | | |
| Cash paid for: | | | | | | | | |