CONDENSED STATEMENTS OF CASH FLOWS - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Operating activities    
Net loss $ (27,358) $ (14,905)
Adjustments to reconcile net loss to net cash used in operating activities:    
Depreciation and amortization 474 54
Stock-based compensation 670 471
Loss from remeasurement of development derivative liability 1,426 454
Non-cash interest expense 93 132
Non-cash research and development expense 11,798 557
Other non-cash transactions 0 100
Changes in operating assets and liabilities:    
Other receivables 0 337
Prepaid expenses and other assets 965 (9,602)
Accounts payable 2,199 (712)
Accrued expenses and other current liabilities (467) (713)
Net cash used in operating activities (10,200) (23,827)
Investing activities    
Purchases of property and equipment (133) (558)
Acquisition of intellectual property rights 0 (100)
Net cash used in investing activities (133) (658)
Financing activities    
Proceeds from development derivative liability 0 10,000
Proceeds from issuance of common stock in public offering, net 60,536 0
Payments of deferred stock offering costs 0 (116)
Proceeds from exercise of stock options 2 17
Repayments of long-term debt (1,364) 0
Net cash provided by financing activities 59,174 9,901
Net increase (decrease) in cash and cash equivalents 48,841 (14,584)
Cash and cash equivalents at the beginning of the period 28,122 74,025
Cash and cash equivalents at the end of the period 76,963 59,441
Supplemental disclosure for cash flow    
Cash paid for interest 192 246
Supplemental disclosure of non-cash investing and financing activities    
Issuance of warrants in conjunction with development derivative liability 0 7,925
Stock offering costs included in accounts payable and accrued expenses 370 45
Purchases of property and equipment by incurring development derivative liability 3,317 0
Purchases of property and equipment included in accounts payable and accrued expenses $ 969 $ 1,031