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Stock option plans (Tables) | 12 Months Ended
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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

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- Definition Tabular disclosure of the number and weighted-average grant date fair value for restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock units that were granted, vested, or forfeited during the year. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
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