| In millions, except per share items | Jun-30-23 | Sep-30-22 | Jun-30-22 | Dec-31-21 | Sep-30-21 | Jun-30-21 | Mar-31-21 | Dec-31-20 |
| | 10-Q | 10-Q | 10-Q | 10-Q | 10-Q | 10-Q | 10-K | 10-Q |
| Cash flows from operating activities | | | | | | | | |
| Net loss | -15.1 | -12.8 | -11.7 | -8.0 | -8.7 | -6.7 | -5.2 | -5.8 |
| |
| Adjustments to reconcile net loss to net cash used in operating activities | | | | | | | | |
| Depreciation and amortization | 0.3 | 0.2 | 0.1 | | 0.1 | | | |
| Amortization of licensed right to use technology | 0.1 | 0.1 | 0.1 | | 0.0 | | | |
| Stock-based compensation | 6.1 | 4.7 | 4.6 | 2.1 | 1.2 | 1.2 | 0.8 | 1.1 |
| Amortization of debt discount | 0.1 | | | 0.5 | 0.1 | | | 0.0 |
| Change in fair value of warrant liability | -0.3 | | | | | | | |
| Change in fair value of derivative liability | -0.5 | | | | | | | |
| Amortization of operating lease assets | 0.1 | 0.1 | 0.0 | | 0.1 | | | |
| Un-realized gain in marketable securities | -0.1 | | | | | | | |
| Foreign currency adjustments | 0.0 | | 0.2 | | | | | |
| |
| Changes in: | | | | | | | | |
| Grant receivable | 0.0 | | -0.2 | | | | | |
| Inventory | -0.2 | -0.1 | -0.3 | | | | | |
| Accounts receivable | 0.0 | 0.2 | | -0.2 | | 0.4 | -0.4 | |
| Other current assets and prepaid expenses | 0.1 | -0.1 | 0.5 | -0.2 | -0.2 | 0.2 | -1.2 | 0.0 |
| Accounts payable | -0.3 | 1.0 | -0.2 | -0.6 | 0.0 | 0.9 | 0.1 | -0.6 |
| Accrued expenses | -7.2 | -3.0 | -0.1 | | 2.7 | -0.1 | | |
| Operating lease liabilities | -0.1 | | | | | | | |
| Net cash used in operating activities | -17.2 | -9.2 | -6.8 | -6.3 | -5.0 | -3.9 | -5.6 | -5.3 |
| |
| Cash flows from investing activities | | | | | | | | |
| Purchase of marketable securities | -9.7 | -32.6 | | | | | | |
| Proceeds from sale of marketable securities | 0.9 | | | | | | | |
| Security deposits made on operating leases | | 0.0 | 0.0 | | -0.1 | | | |
| Purchase of property and equipment | -0.8 | -1.0 | -0.3 | -0.4 | -0.6 | 0.0 | 0.0 | -0.1 |
| Net cash used in investing activities | -9.7 | -33.6 | -0.3 | -0.4 | -0.7 | 0.0 | 0.0 | -0.1 |
| |
| Cash flows from financing activities | | | | | | | | |
| Proceeds from issuance of common stock through at the market offerings | 5.8 | 0.2 | | 38.2 | 15.0 | 8.5 | 6.3 | -1.1 |
| Proceeds from issuance of common stock through exercise of stock options | 0.2 | | | 0.2 | 0.1 | | | 0.0 |
| Proceeds from loan | 15.8 | | | | | | | |
| Payment of loan | -0.3 | -0.1 | -0.5 | -0.2 | -0.2 | -0.2 | -0.1 | -0.1 |
| Net cash provided by and (used in) financing activities | 21.6 | 0.1 | -0.5 | 50.7 | 14.8 | 8.3 | 18.2 | 5.7 |
| Effect of exchange rate changes on cash and cash equivalents | 0.0 | -0.2 | 0.2 | | | | | |
| Decrease in cash, cash equivalents and restricted cash | -5.2 | | -7.5 | | | | | |
| |
| Supplemental disclosure of non-cash investing and financing activities | | | | | | | | |
| Debt discount | 4.5 | | | | | | | |
| End of term loan liability | -0.6 | | | | | | | |
| Warrant liability | -0.9 | | | | | | | |
| |
| Derivative liability | | | | | | | | |
| Right-of-use assets | | | | | | | | |
| Operating lease liability | | | | | | | | |
| Supplemental disclosure of cash flow items: | | | | | | | | |
| Interest paid | 0.3 | 0.0 | 0.0 | 0.2 | 0.0 | 0.1 | 0.2 | 0.3 |
| Income taxes paid | | | | | | | | |