Long-term debt consisted of the following (in thousands): | | | | | | | | | | | | | December 31, | | 2021 | | 2020 | | Principal amount of long-term debt | $ | — | | | $ | 20,000 | | | Less: Current portion of long-term debt | — | | | — | | | Long-term debt, net of current portion | — | | | 20,000 | | | Final payment fee | — | | | 1,000 | | | Debt discount, net of accretion | — | | | (1,346) | | | Long-term debt, net of discount and current portion | $ | — | | | $ | 19,654 | |
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