Stock option plans (Tables)

12 Months Ended

Dec. 31, 2022

Stock option plan

Schedule of assumptions used in valuation of stock options

	Year ended December 31,
	2022	2021	2020
Expected volatility	84.4%-89.6%	88.1%-90.2%	78.9% ‑83.8%
Risk‑free rate	1.95%-2.69%	0.96%-1.04%	0.36% ‑1.43%
Expected dividend yield	0%	0%	0%
Expected term in years	6.08-10.00	5.50 - 6.08	5.50 - 6.08

Summary of stock option activity

			Weighted‑		Weighted
			average		average
			exercise		remaining	Aggregate
	Number of		price per		contractual	intrinsic
	options		share		term (in years)	value
Outstanding at January 1, 2020		174,975	$	109.80	7.5
Granted		22,340		710.13
Exercised		(8,203)		18.33
Cancelled/Forfeited		(560)		775.60
Outstanding at December 31, 2020		188,552	$	182.00	6.8
Granted		58,980		117.40
Exercised		(11,319)		18.40
Cancelled/Forfeited		(6,905)		330.60
Outstanding at December 31, 2021		229,308	$	169.00	6.6
Granted		96,798		31.40
Options assumed in Atrin merger		163,733		14.21
Exercised		—		—
Cancelled/Forfeited		(9,565)		118.60
Outstanding at December 31, 2022		480,274	$	89.49	6.8	$
Exercisable at December 31, 2022		447,721	$	94.41	6.1	$
Vested or expected to vest at December 31, 2022		480,274	$	89.49	6.8	$

Summary of restricted stock units activity

		Weighted‑
		average
		grant date
	Shares	fair value
Restricted stock units outstanding at December 31, 2020	—	$	—
Granted	26,150		118.20
Vested	(5,365)		118.80
Cancelled/Forfeited	(800)		120.00
Outstanding at December 31, 2021	19,985	$	118.20
Granted	24,064		28.68
Vested	(30,981)		88.21
Cancelled/Forfeited	(334)		114.60
Outstanding at December 31, 2022	12,734	$	21.80