In November 2017, the Company entered into a lease agreement for its current corporate headquarters comprising approximately 28,731 square feet of office and laboratory space at 26 Landsdowne Street in Cambridge, Massachusetts, commencing December 2017. The Company began to occupy and use the leased space for its intended purpose in June 2018. The lease ends on June 30, 2028. The Company has the option to extend the term of the lease for an additional five-year period, at the market rate, by giving the landlord written notice of its election to exercise the extension at least nine months prior to the original expiration of the lease term. The lease has a total commitment of $25.1 million over the ten year term, and includes escalating rent payments. The lease provides the Company with an allowance for normal leasehold improvements of $5.0 million. The lease agreement requires the Company to either pay a security deposit or maintain a letter of credit of $1.1 million. The Company maintains a letter of credit for this lease and has recorded the cash held to secure the letter of credit as restricted cash on the consolidated balance sheet as of December 31, 2022 and December 31, 2021.

As a result of the adoption of ASU 2016-02, as amended, on January 1, 2022, the Company recorded a right-of-use asset and a corresponding lease liability associated with the 26 Landsdowne Street lease on the consolidated balance sheet as of December 31, 2022. As there is no rate implicit in the 26 Landsdowne Street lease, the Company estimated its incremental

borrowing rate based upon a synthetic credit rating and yield curve analysis. Based upon this analysis, the Company calculated a discount rate of 6.1% for the lease. As of December 31, 2022, the remaining lease term was 5.5 years.

Pursuant to ASU 2016-02, as amended, operating lease expense and variable lease expense associated with this lease for the year ended December 31, 2022 was approximately $1.9 million and $1.0 million, respectively.

The future minimum lease payments associated with the 26 Landsdowne Street lease as of December 31, 2022, are as follows (in thousands):


2023	$	2,497
2024		2,572
2025		2,649
2026		2,729
Thereafter		4,237
Total minimum lease payments		14,684
Less: imputed interest		(2,278	)
Total lease liability	$	12,406

Prior to the adoption of ASU 2016-02, as amended, and pursuant to the legacy guidance within ASC 840, the Company recorded rent expense on a straight-line basis through the end of the lease term and also recorded deferred rent on the consolidated balance sheets. The Company recorded the leasehold improvement incentives as a deferred lease incentive on the consolidated balance sheets and amortized the deferred lease incentive through a reduction of rent expense ratably over the lease term.

Pursuant to ASC 840, rent expense associated with this lease for the year ended December 31, 2021 was approximately $1.9 million. Under ASC 840, minimum rental commitments under non-cancelable leases for each of the next five years and total thereafter as of December 31, 2021, were as follows (in thousands):


2022	$	2,424
2023		2,497
2024		2,572
2025		2,649
2026		2,729
Thereafter		4,237
Total minimum lease payments		17,108

In November 2021, the Company entered into a lease agreement comprising approximately 12,196 square feet of office space at 125 Sidney Street in Cambridge, Massachusetts, commencing November 2021. The Company began recognizing rent expense associated with this lease during November 2021. The lease ends on March 31, 2024. The Company has the option to extend the term of the lease for two successive one-year periods, at the market rate, by giving the landlord written notice of its election to exercise the extension at least nine months prior to the original expiration of the lease term. The lease has a total commitment of $1.7 million over the initial term, and includes escalating rent payments.

As a result of the adoption of ASU 2016-02, as amended, on January 1, 2022, the Company recorded a right-of-use asset and a corresponding lease liability associated with the 125 Sidney Street lease on the consolidated balance sheet as of December 31, 2022. As there is no rate implicit in the 125 Sidney Street lease, the Company estimated its incremental borrowing rate based upon a synthetic credit rating and yield curve analysis. Based upon this analysis, the Company calculated a discount rate of 4.2% for the lease. As of December 31, 2022, the remaining lease term was 1.2 years.

Pursuant to ASU 2016-02, as amended, operating lease expense associated with this lease for the year ended December 31, 2022 was approximately $0.7 million. No variable lease expense was recorded associated with this lease for the year ended December 31, 2022. The future minimum lease payments associated with this lease as of December 31, 2022, are as follows (in thousands):


2023	$	836
2024		210
Total minimum lease payments		1,046
Less: imputed interest		(29	)
Total lease liability	$	1,017

Pursuant to ASC 840, rent expense associated with this lease for the year ended December 31, 2021 was approximately $0.1 million. Under ASC 840, minimum rental commitments under non-cancelable leases for each of the next five years and total thereafter as of December 31, 2021, were as follows (in thousands):


2022	$	613
2023		836
2024		210
Total minimum lease payments	$	1,659