Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (18,367)	$ (41,911)
Adjustments to reconcile net loss to net cash used in operating activities:
In-process research and development acquired		30,885
Depreciation expense	36	40
Impairment of property and equipment	61
Stock-based compensation expense	2,976	401
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	718	(322)
Accounts payable	1,090	(394)
Accrued liabilities	391	(3,319)
Net cash used in operating activities	(13,095)	(14,620)
Cash flows from investing activities:
Cash and restricted cash acquired in reverse merger		3,582
Net cash provided by investing activities		3,582
Cash flows from financing activities:
Proceeds from issuance of common stock, net of issuance costs		24,016
Payment of offering costs	(66)
Proceeds from exercise of stock options	61	258
Net cash (used in) provided by financing activities	(5)	24,274
Net (decrease) increase in cash and cash equivalents	(13,100)	13,236
Cash and cash equivalents — beginning of period	58,765	6,939
Cash and cash equivalents — end of period	45,665	20,175
Non-cash investing and financing activities:
Conversion of preferred stock to common stock		10,515
Issuance of common stock to Tocagen shareholders		31,809
Unpaid offering costs	$ 40	$ 297