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Commitments and Contingencies (Tables) | 12 Months Ended
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Dec. 31, 2020
Commitments and Contingencies |
Summary of lease costs | Other information related to the Company’s leases (excluding the Company’s sublease) is as follows (in thousands, except lease term and discount rate):
​ | ​ | ​ | ​
​ | ​ | For Year Ended
​ |  | December 31,
​ | ​ | 2020
Lease Cost: | ​ | ​ | ​
Operating lease cost | ​ | $ | 3,229
Variable lease cost | ​ | ​ | 1,027
Total lease cost | ​ | $ | 4,256
​
​ | ​ | ​ | ​
​ | For Year Ended | ​
​ | December 31, | ​
​ | 2020 | ​
Other information: | ​ | ​ | ​
Operating cash flows used for operating leases (1) | $ | 2,111 | ​
Weighted average remaining lease term | ​ | 4.4 years | ​
Weighted average incremental borrowing rate | ​ | 7.5 | %
​ (1) Operating cash flows used for operating leases are presented net of certain tenant improvement reimbursements received related to the construction of the Company’s office and laboratory space at 301 Binney Street.
Summary of minimum lease payments | The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of December 31, 2020 (in thousands):
​ | ​ | ​ | ​
Year Ending December 31, |  | ​ | ​
2021(1) | ​ | $ | 7,657
2022 | ​ |  | 9,196
2023 | ​ |  | 9,070
2024 | ​ | ​ | 8,064
2025 | ​ | ​ | 4,498
Total lease payments | ​ | ​ | 38,485
Less imputed interest | ​ | ​ | (6,026)
Total operating lease liabilities | ​ | $ | 32,459
​ (1) Cash flows for operating lease liabilities in 2021 are presented net of tenant improvement allowances expected to be received related to the construction of the Company’s office and laboratory space at 301 Binney Street.

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- Definition Tabular disclosure of lessee's lease cost. Includes, but is not limited to, interest expense for finance lease, amortization of right-of-use asset for finance lease, operating lease cost, short-term lease cost, variable lease cost and sublease income. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918686-209980 + Details
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- Definition Tabular disclosure of undiscounted cash flows of lessee's operating lease liability. Includes, but is not limited to, reconciliation of undiscounted cash flows to operating lease liability recognized in statement of financial position. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918701-209980 + Details
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