Consolidated Balance Sheets - USD ($)	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Statement of Financial Position [Abstract]
Cash and cash equivalents	$ 59,716,000		$ 18,820,000
Restricted cash	45,000		0
Prepaid expenses and other current assets	2,796,000	$ 1,005,000	1,005,000
Total current assets	62,557,000		19,825,000
Property and equipment — net	1,116,000	1,110,000	1,110,000
Operating lease right-of-use assets	3,357,000		1,877,000
Other noncurrent assets	112,000		51,000
Total assets	67,142,000		22,863,000
Accounts payable	2,380,000		1,071,000
Accrued expenses	1,658,000	665,000	665,000
Operating Lease, Liability, Current	1,411,000		712,000
Accrued compensation	664,000		695,000
Interest payable	89,000		0
Early option exercise liability	1,000	79,000	79,000
Total current liabilities	6,203,000		3,222,000
Loan payable (net of discount and issuance costs of $820)	15,005,000		0
Noncurrent operating lease obligations	2,398,000		1,727,000
Total liabilities	23,606,000		4,949,000
Commitments and contingencies (Note 8)
Convertible preferred stock, $0.001 par value; shares 5,000,000 and 135,936,731 shares authorized at September 30, 2021 and December 31, 2020; nil and 114,686,731 shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively; liquidation preference of $0 and $100,186,832 at September 30, 2021 and December 31, 2020, respectively	0		86,707,000
Common stock, $0.001 par value; 100,000,000 shares and 196,000,000 shares authorized at September 30, 2021 and December 31, 2020; 6,900,731 and 527,265 shares issued and outstanding, 136 and 29,041 subject to repurchase at September 30, 2021 and December 31, 2020, respectively	7,000		15,000
Additional paid-in capital	135,902,000		2,953,000
Accumulated other comprehensive loss	(89,000)		0
Accumulated deficit	(92,284,000)		(71,761,000)
Total stockholders’ equity (deficit)	43,536,000		(68,793,000)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 67,142,000		$ 22,863,000