Organization and summary of significant accounting policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) NumberOfSegment shares	Dec. 31, 2021 USD ($) shares
Organization And Summary Of Significant Accounting Policies [Line Items]
Entity Incorporation, State or Country Code	DE
Company formation date	2007-03
Common Stock, Shares, Issued | shares	46,336,166	35,799,233
Preferred Stock, Shares Issued | shares	0	0
Accumulated deficit	$ (292,801,000)	$ (186,319,000)
Uncertain tax positions percentage	50.00%
Number of operating segment | NumberOfSegment	1
Impairment losses	$ 0	0
Operating lease right-of-use-assets	2,423,000	3,300,000
Operating lease liabilities	1,521,000	1,389,000
Operating lease liabilities, less current portion	2,460,000	$ 3,982,000
Accrued clinical trial cost	5,500,000
Accumulated deficit
Organization And Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit	$ 292,800,000
Class B Common Stock
Organization And Summary Of Significant Accounting Policies [Line Items]
Common Stock, Shares, Issued | shares	1,211,959	1,492,059