Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating losses	$ 27,047	$ 16,655
Research and development credits	7,617	4,949
Accrued expenses	291	130
Other	474	247
Deferred rent	266	124
Stock based compensation	428	73
Total deferred tax assets	36,123	22,178
Deferred tax liabilities:
Asset basis	(124)	(110)
Prepaid expenses	(558)	(139)
Total deferred tax liabilities	(682)	(249)
Valuation allowance	$ 35,441	$ 21,929	$ 20,240