Summary of significant accounting policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2022 USD ($) Segment	Dec. 31, 2021 USD ($)
Financing Sources [Line Items]
Re-measurement loss	$ 42,000	$ 6,000
Number of reportable segments | Segment	1
Product revenue	$ 0
Property and equipment, net	$ 4,816,000	6,180,000
Cash equivalent qualification, description	The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents.
Restricted cash	$ 115,000	$ 164,000
Investments, maturity period	1 year 6 months	1 year 6 months
Other than temporary impairment losses, investments	$ 0	$ 0
Impairment of long lived assets	0	0
Royalties due	0
Expenses on milestone payments	0
Dividends, common stock, cash	$ 0
Expected dividend yield	0.00%
Percentage of expected average remaining working lives of employees	10.00%
Research and Development
Financing Sources [Line Items]
Expenses on milestone payments		500,000
US
Financing Sources [Line Items]
Property and equipment, net	$ 4,100,000	5,000,000.0
Belgium
Financing Sources [Line Items]
Property and equipment, net	$ 700,000	$ 1,200,000