Stock-based compensation - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2023	Dec. 31, 2023
Stock options
Shares
Outstanding at the beginning of the period (in shares)	2,270,359
Granted (in shares)	31,751
Exercised (in shares)	(4,600)
Forfeited/cancelled (in shares)	(151,695)
Expired	(22,914)
Outstanding at the end of the period (in shares)	2,122,901			2,270,359
Vested at the end of the period (in shares)			565,008
Weighted-average exercise price per share
Outstanding at the beginning of the period (in dollars per share)	$ 19.81
Granted (in dollars per share)	9.77
Exercised (in dollars per share)	7.97
Forfeited/cancelled (in dollars per share)	12.89
Expired (in dollars per share)	163.77
Outstanding at the end of the period (in dollars per share)	$ 13.18			$ 19.81
Vested at the end of the period (in dollars per share)			$ 20.83
Weighted-average remaining contractual term
Outstanding at the end of the period	8 years 8 months 12 days			7 years 9 months 18 days
Vested at the end of the period			7 years 3 months 18 days
Aggregate intrinsic value
Outstanding at the beginning of the period (in dollars)	$ 559
Outstanding at the end of the period (in dollars)	$ 4,539			$ 559
Vested at the end of the period (in dollars)			$ 1,084
Assumptions used to estimate fair value of each stock-based award on the grant date
Risk-free interest rate (as a percent)	4.08%	3.56%
Volatility (as a percent)	95.00%	90.00%
Expected term (years)	6 years 2 months 5 days	5 years 7 months 6 days
Option Exchange Program
Additional disclosures
Stock-based compensation expense	$ 1,700
Option Exchange Program | Stock options
Shares
Granted (in shares)	603,330
Forfeited/cancelled (in shares)	(603,330)
Weighted-average exercise price per share
Granted (in dollars per share)	$ 11.44
Forfeited/cancelled (in dollars per share)	$ 30.58