Stockholder's equity (deficit) - Common stock (Details)										1 Months Ended		6 Months Ended
	May 10, 2024 USD ($)	Mar. 08, 2024 USD ($) $ / shares shares	May 16, 2023 USD ($) $ / shares shares	Mar. 17, 2023 USD ($)	Sep. 19, 2022 USD ($) $ / shares shares	Jun. 17, 2022 USD ($)	Jun. 15, 2022 $ / shares shares	Jul. 10, 2020 USD ($) $ / shares shares	Jun. 24, 2019 USD ($) $ / shares shares	Feb. 29, 2024 USD ($) $ / shares shares	Apr. 30, 2023 $ / shares shares	Jun. 30, 2024 USD ($) Vote $ / shares shares	Aug. 31, 2024 $ / shares	Dec. 31, 2023 $ / shares shares	May 31, 2023 $ / shares	Jun. 18, 2019 shares
Class of Stock [Line Items]
Common stock, shares authorized												150,000,000		150,000,000
Common stock, par value (in dollars per share) | $ / shares												$ 0.0001	$ 0.0001	$ 0.0001
Number of votes per share | Vote												1
Cash dividend declared | $ / shares												$ 0
Cash dividend paid | $ / shares												$ 0
Net proceeds from the sales of common stock in equity offerings | $												$ 1,196,600,000
Common stock, shares issued												69,205,668		55,754,445
Common stock, shares outstanding												69,205,668		55,754,445
Common stock were reserved for issuance
Options available for future grant												25,113,641		13,667,341
Jeffries
Class of Stock [Line Items]
Net proceeds from the sales of common stock in equity offerings | $			$ 210,956,000
Offering costs | $			$ 9,061,000
Sale of stock under agreement			5,238,500
Sale of stock, price per share | $ / shares			$ 42
Employee Stock Option
Common stock were reserved for issuance
Options available for future grant												2,976,020		1,917,356
Common stock Available under ATM Offering
Class of Stock [Line Items]
Net proceeds from the sales of common stock in equity offerings | $						$ 24,647,000				$ 10,604,000		$ 123,824,000
Offering costs | $										$ 271,000		$ 3,578,000
Sale of stock under agreement										500,000	3,006,052
Sale of stock, price per share | $ / shares										$ 21.75	$ 42.38				$ 42.38
Common stock were reserved for issuance
Options available for future grant												11,722,981		2,708,234
Common stock Available under ATM Offering | Pfizer Inc
Class of Stock [Line Items]
Sale of stock under agreement							2,525,252
Sale of stock, price per share | $ / shares							$ 9.9
Warrants to Purchase Common Stock
Common stock were reserved for issuance
Options available for future grant												64,257		45,898
Warrants Available for Future Grant
Common stock were reserved for issuance
Options available for future grant												211,137		137,700
2018 Stock option and grant plan
Common stock were reserved for issuance
Options available for future grant												980,868		1,114,189		107,635
2019 Stock Option and Incentive plan
Common stock were reserved for issuance
Options available for future grant												6,611,554		5,785,788
2019 Stock Option and Incentive plan | Unvested Restricted Stock Units
Common stock were reserved for issuance
Options available for future grant												566,041		371,952
2019 Employee Stock Purchase Plan
Common stock were reserved for issuance
Options available for future grant												1,980,783		1,586,224
Maximum | Common stock Available under ATM Offering
Class of Stock [Line Items]
Share Issued value under agreement | $				$ 200,000,000
IPO
Class of Stock [Line Items]
Public offering price | $ / shares									$ 16
Net proceeds from the sales of common stock in equity offerings | $									$ 98,394,000
Offering costs | $									$ 2,942,000
Number of shares converted									21,056,136
Common stock, shares issued									6,612,500
Follow Up Public Offering
Class of Stock [Line Items]
Share Issued under agreement					8,846,154			6,012,390
Public offering price | $ / shares		$ 29			$ 26			$ 36
Net proceeds from the sales of common stock in equity offerings | $		$ 344,838,000			$ 216,200,000			$ 203,460,000
Offering costs | $		$ 22,011,000			$ 13,800,000
Common stock, shares issued		12,650,000
Proceeds from issuance of common stock before deducting offering costs | $		$ 401,000
Over allotment | Maximum
Class of Stock [Line Items]
Share Issued under agreement		1,650,000			1,153,846			784,224
Common stock, shares issued									862,500
Amended Sales Agreement
Class of Stock [Line Items]
Share Issued value under agreement | $	$ 200,000,000
Amended Sales Agreement | Maximum
Class of Stock [Line Items]
Share Issued value under agreement | $	$ 261,723,000