CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating Activities:
Net loss	$ (123,430)	$ (64,002)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	5,614	5,172
Loss on disposal of property and equipment	3	348
Stock-based compensation	23,134	18,926
Write off of deferred CIRM grant liability	(3,992)
Accretion of discount on issued term debt	808	844
Accretion on investment securities, net	(8,385)	(1,775)
Changes in operating assets and liabilities:
Accounts receivable	77	(9,088)
Prepaid expenses and other current assets	1,565	499
Operating lease right-of-use assets	3,359	4,605
Other long-term assets	(25)	605
Accounts payable	1,038	(6,748)
Accrued expenses and other liabilities	5,004	1,399
Operating lease liabilities	(3,669)	(4,852)
Deferred revenue	6,732	27,295
Net cash used in operating activities	(92,167)	(26,772)
Investing Activities:
Purchases of property and equipment	(3,066)	(3,924)
Proceeds from sale of property and equipment		12
Purchases of short-term investments	(237,800)	(294,422)
Proceeds from maturities of short-term investments	280,000	95,000
Net cash provided by (used in) investing activities	39,134	(203,334)
Financing Activities:
Proceeds from issuance of common stock under employee stock compensation plans	1,276	1,310
Payment of taxes related to net share settlement of equity awards	(494)
Proceeds from issuance of common stock through ATM offering, net of issuance costs	928
Proceeds from private placement of common stock	14,417
Proceeds from public offering of common stock, net of issuance costs		75,299
Proceeds from term debt		30,000
Payment of debt issuance costs		(1,450)
Net cash provided by financing activities	16,127	105,159
Net decrease in cash and cash equivalents	(36,906)	(124,947)
Cash and cash equivalents at beginning of period	81,378	206,325
Cash and cash equivalents at end of period	44,472	81,378
Non-cash operating, investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued liabilities	20	1,144
Right-of-use assets obtained in exchange for operating lease liabilities		4,425
Supplemental disclosure of cash flow information:
Interest paid	$ 7,796	$ 5,138