5. PREPAID EXPENSE AND OTHER CURRENT ASSETS Prepaid expenses and other current assets consisted of the following (in thousands): | | | | | | | | | December 31, | | December 31, | (in thousands) | | 2021 | | 2020 | Prepaid research and development expenses | | $ | 4,483 | | $ | 2,349 | Insurance premium asset | | | 1,616 | | | 1,463 | Prepaid rent expenses | | | 117 | | | 108 | Prepaid insurance expenses | | | 105 | | | 91 | Prepaid commercial and patient advocacy | | | 254 | | | 968 | Research and development tax credit receivable | | | 502 | | | 500 | Interest receivable | | | 23 | | | 5 | Other prepaid expenses and current assets | | | 471 | | | 280 | Total prepaid expenses & other current assets | | $ | 7,571 | | $ | 5,764 |
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