In October 2014, the Company entered into an agreement to lease office and laboratory space at 130 Brookline Street (the “130 Brookline Lease”) in Cambridge, Massachusetts under an operating lease agreement with a term through January 2020, with an option to extend the term of the lease for an additional five-year period. In April 2019, the lease was amended to extend the term for the additional five-year period, through January 2025. Upon the execution of the original lease, the Company provided a $0.3 million security deposit which is recorded in “Investments and other assets” on the Company's consolidated balance sheets.

In March 2020, the Company entered into a second amendment to the 130 Brookline Lease (the “130 Brookline Lease Second Amendment”). The 130 Brookline Lease Second Amendment extends the term of the 130 Brookline Lease by

approximately six years through January 31, 2031. This extended term is included as part of the lease liability and right-of-use asset at December 31, 2021. The 130 Brookline Lease Second Amendment also provides an option to extend the lease for two consecutive five-year terms. The option for these further extensions is not included as part of the lease liability and right-of-use asset at December 31, 2021, as it is not reasonably certain that it will be exercised. In the first quarter of 2020, the Company increased the right-of-use asset and liability related to this lease by approximately $7.3 million related to the 130 Brookline Lease Second Amendment.

In March 2019, the Company entered into a separate agreement to sublease additional office and laboratory space at 130 Brookline Street in Cambridge, Massachusetts under an operating sublease agreement with a term through April 2021, with two options to extend the agreement by one year each, for a total option period of up to two years. Upon commencement of the lease in April 2019, the Company recognized a right-of-use asset and lease liability of approximately $1.3 million. In September 2020, the Company amended the lease to extend the term until October 2021. An adjustment of $0.4 million to the right-of-use asset and lease liability was recorded upon the execution of the amendment. This sublease was terminated in September 2021.

In January 2016, the Company entered into a ten-year agreement to lease office and laboratory space at 40 Erie Street (the “40 Erie Lease”) in Cambridge, Massachusetts under an operating lease agreement, with an option to terminate the lease at the end of the sixth year and an option to extend the term of the lease for an additional three years. Upon the execution of this lease, the Company provided a $2.2 million security deposit, which has been recorded in “Investments and other assets” on the consolidated balance sheets. In November 2020, the Company entered into a second amendment to the 40 Erie Lease (the “40 Erie Lease Second Amendment”) which provides the Company with a right of first offer with respect to any space that becomes available at the 40 Erie Street building, and in consideration for this right the Company agreed to nullify the option to terminate the lease at the end of the sixth year that was included in the 40 Erie Lease. In the fourth quarter of 2020, the Company increased the right-of-use asset and liability related to this lease by approximately $18.5 million related to the 40 Erie Lease Second Amendment.

In March 2020, the Company entered into an agreement to lease approximately 39,000 square feet of office and laboratory space at 281 Albany Street in Cambridge, Massachusetts under an operating lease agreement (the “281 Albany Lease”). The initial term of the 281 Albany Lease is ten years following the rent commencement date which was determined to be March 2021 in accordance with ASC 842, Leases (Topic 842) (“ASC 842”), as that was when the facility was substantially complete and available for use. The Company recognized a right-of-use asset and a lease liability of approximately $40.4 million and $34.8 million, respectively, in the first quarter of 2021 related to the 281 Albany Lease. In determining the lease liability, the Company used an incremental borrowing rate of 5.52% based on a number of factors including the Company’s credit rating and the lease term. Included in the recognized right-of-use asset at the inception of the lease was approximately $5.6 million in lease payments that were prepaid under the terms of the lease. The Company modified the right-of-use asset in the second quarter of 2021 based on changes to the configuration of this space, resulting in an additional $1.4 million being added to the right-of-use asset. The base rent under the 281 Albany Lease is $99.00 per square foot per year during the first year of the term, which is subject to scheduled annual increases up to $128.87 per square foot per year during the last year of the initial term, plus certain operating expenses and taxes. In addition, the landlord contributed an aggregate of $4.4 million toward the cost of construction and tenant improvements for the premises. In accordance with the 281 Albany Lease, the Company is required to maintain a letter of credit in the amount of $1.9 million that is restricted for the term of the lease. These restricted cash equivalents are reported in “Investments and other assets” in the Company’s consolidated balance sheet. The Company has the option to extend the 281 Albany Lease for two successive five-year terms; this option is not included as part of the lease liability and right-of-use asset at December 31, 2021, as it is not reasonably certain that it will be exercised.

In July 2021, the Company entered into an agreement to lease 13,662 square feet of office space at 17 Tudor Street in Cambridge, Massachusetts under an operating lease agreement (the “17 Tudor Lease”). The Company’s obligation to pay rent began on November 1, 2021. The initial term of the 17 Tudor Lease is five years and the Company has an option to extend the 17 Tudor Lease for one three-year term. The option is not included as part of the lease liability and right-of-use asset at December 31, 2021, as it is not reasonably certain that it will be exercised. The base rent under the 17 Tudor Lease is $74.00 per square foot during the first year of the term, which is subject to scheduled annual increases throughout the term, resulting in a base rent of $83.29 per square foot during the last year of the initial term, plus certain operating expenses and taxes. In September 2021 the Company determined, in accordance with ASC 842, that the commencement date of the lease had been met as the Company had gained access to the facility

in order to begin work on lessee-owned tenant improvements and, accordingly, the Company recognized a right-of-use asset and a lease liability of approximately $4.9 million in the third quarter of 2021 related to the 17 Tudor Lease. In determining the lease liability, the Company used an incremental borrowing rate of 4.15% based on a number of factors including the Company’s credit rating and the lease term. In accordance with the 17 Tudor Lease, the Company is required to maintain a letter of credit in the amount of $0.2 million that is restricted for the term of the lease. These restricted cash equivalents are reported in “Investments and other assets” in the Company’s consolidated balance sheet.

In July 2021, the Company entered into an agreement to extend an existing lease for a clean room located in Waltham, Massachusetts under an operating lease agreement (the “Waltham Lease”) for an additional two years. The Company determined, in accordance with ASC 842, that the extension should be accounted for as a lease modification and, accordingly, recorded an adjustment to the right-of-use asset and lease liability of approximately $2.5 million in the third quarter of 2021 related to the Waltham Lease.

Throughout the term of its leases, the Company is responsible for paying certain costs and expenses, in addition to the rent, as specified in the lease, including a proportionate share of applicable taxes, operating expenses and utilities. The variable portion of these costs are expensed as incurred and are disclosed as variable lease cost.

The following table contains a summary of the lease costs recognized under ASC 842 and other information pertaining to the Company’s operating leases for the years ended December 31, 2021 and 2020:


	Year Ended December 31,
	2021		2020
	(In thousands)
Lease cost
Operating lease cost	$	12,871	$	8,447
Short-term lease cost		31		56
Variable lease cost		3,339		2,918
Total lease cost	$	16,241	$	11,421

	Year Ended December 31,
	2021		2020
	(In thousands)
Other information
Operating cash flows used for operating leases	$	12,641	$	7,495
Operating lease liabilities arising from obtaining right-of-use assets		49,378		26,432

	As Of December 31,
	2021		2020
Lease term and discount rate
Weighted average remaining lease term	7.2 years		6.7 years
Weighted average discount rate	5.50%		5.80%

The table below reconciles the undiscounted cash flows for each of the next five years and total of the remaining years to the operating lease liabilities recorded in the consolidated balance sheet as of December 31, 2021:


Future Operating Lease Payments
Year Ending December 31,	(in thousands)
2022	$	12,929
2023		13,398
2024		12,320
2025		12,838
2026		11,544
Thereafter		28,809
Total lease payments	$	91,838
Less: imputed interest		(17,815	)
Total operating lease liabilities at December 31, 2021	$	74,023