The Company has entered into various long-term non-cancelable lease arrangements for its facilities, expiring at various times through 2029. Certain arrangements have free rent periods or escalating rent payment provisions; costs under such arrangements are recognized on a straight-line basis over the life of the leases. The Company has two locations in Massachusetts, its office and laboratory, located in Cambridge and manufacturing space, located in Lexington, which is currently being leased and operated by Lonza (Note 3).

The Company leased building space at 500 Technology Square in Cambridge, Massachusetts. Under the terms of the lease, the Company leased approximately 19,823 square feet for $1.5 million per year in base rent, which was subject to a 2.5% annual rent increase plus certain operating expenses and taxes. The Company accounted for this lease as an operating lease. The lease commenced on December 28, 2016 and originally expired on December 31, 2021. On August 26, 2019, the Company signed a lease termination to accelerate the expiration date of the lease to February 28, 2020.

On March 5, 2019, the Company entered into a lease for manufacturing space at 4 Hartwell Place, ("4 Hartwell") in Lexington, Massachusetts. Under the terms of the lease, the Company leases approximately 18,707 square feet for $0.9 million per year in base rent, which is subject to a 2.6% annual rent increase during the initial lease term, plus certain operating expenses and taxes. The lease term commenced in July 2019 and will end in December 2029. The Company has the option to extend the lease twice, each for a five-year period, on the same terms and conditions as the current lease, subject to a change in base rent based on market rates. The Company had fully occupied the space as of December 31, 2020. Upon execution of the lease agreement, the Company provided a security deposit of $0.4 million which is held in the form of a letter of credit and was classified as non-current restricted cash on the condensed consolidated balance sheets as of December 31, 2021 and December 31, 2020. The lease provided the Company with a tenant improvement allowance of up to $1.3 million, which is being amortized as a reduction to rent expense over the remaining lease term. As of December 31, 2021, the Company had received all $1.3 million of the tenant improvement allowance. Costs incurred related to the allowance are capitalized as leasehold improvements.

On November 15, 2021, the Company entered into an amendment to the lease (the Master Lease Amendment) for the property located at 4 Hartwell Place in Lexington, Massachusetts. The only change to the terms of the lease was to increase the base rent by $0.1 million per year. There were no initial direct costs incurred, incremental incentives received or any other payments made to or by the Company with respect to the Master Lease Amendment. The Company accounted for the changes made to the lease agreement as a lease modification. The Company determined that the associated lease should continue to be accounted for as an operating lease with a lease term commensurate with the initial lease term which ends in December 2029. The Company remeasured the lease liability as of November 15, 2021 based on the then-current applicable incremental borrowing rate resulting in an increase of $1.0 million which was offset by an equal adjustment made to the corresponding right-of-use asset.

On March 22, 2019, the Company entered into a non-cancelable property lease for office and laboratory space at 35 CambridgePark Drive, ("35 CambridgePark") in Cambridge, Massachusetts. Under the terms of the lease, the Company leases approximately 68,258 square feet for $4.9 million per year in base rent, which is subject to a 3.0% annual rent increase during the initial lease term, plus certain operating expenses and taxes. The Company accounts for this lease as an operating lease. The lease term commenced upon execution of the lease on March 26, 2019 and is expected to end in November 2029. The Company has the option to extend the lease for a 10-year period on the same terms and conditions as the current lease, subject to a change in base rent based on market rates. The Company occupied the space in February 2020 as its new corporate headquarters. Upon execution of the lease agreement, the Company provided a security deposit of $3.7 million which is held in the form of a letter of credit and is classified as non-current restricted cash on the accompanying consolidated balance sheets as of December 3, 2020 and 2019. The lease provides the Company with a tenant improvement allowance of $12.3 million, subject to reduction for a 2% construction oversight fee due to the landlord, which is being amortized as a reduction to rent expense over the remaining lease term. As of December 31, 2020, the Company had received all $12.3 million of the tenant improvement allowance. Costs incurred related to the allowance are capitalized as leasehold improvements.

On November 15, 2021, the Company entered into a sublease agreement with Lonza for the entirety of its leased space at 4 Hartwell Place in Lexington, Massachusetts, as discussed in Note 3. Under the terms of the Sublease Agreement, Lonza is obligated to pay the Company base rent of approximately $1.0 million per year, subject to a 2.8% annual increase, plus certain operating expenses and other costs. The initial lease term commenced on November 15, 2021 and continues through November 30, 2024. Lonza has the option to extend the sublease term for five 12-month periods on the same terms and conditions as the current sublease, subject to an increase of 2.8% in the annual fixed rent charges. Additionally, Lonza has the right to have the associated master lease assigned to it beginning on January 1, 2026, subject to the landlord’s consent. As of December 31, 2021, the Company has not been legally released from its primary obligations under the original lease. Therefore, the Company continues to account for the original lease as it did before commencement of the sublease, inclusive of the effects of the Master Lease Amendment. The Company determined that the sublease term is commensurate with the initial sublease term because it is not reasonably certain that any of the extension options will be exercised.

On April 27, 2020, the Company entered into a sublease for 23,280 square feet of its leased space at 35 CambridgePark Drive. Under the terms of the sublease, the sublessee was to pay the Company approximately $1.3 million per year, which was subject to a 3.0% annual rent increase, plus certain operating expenses. The lease term commenced on May 18, 2020 and was expected to end in May 2022. The sublessee had the option to extend the sublease for a one-year period on the same terms and conditions as the current sublease, subject to a change in base rent based on the greater of (i) an increase of 3% of the annual rent owed by the sublessee in year two, and (ii) market rent for the subleased premises. Upon execution of the sublease agreement, the sublessee provided the Company a security deposit of $0.3 million which is held in the form of a letter of credit.

Effective July 1, 2021, the Company received notice of the sublessee’s intent to exercise its option to extend the sublease for a one-year period through May 2023. The Company increased the base rent of the option period to reflect a market-based fixed annual rate beginning June 2022. The Company remains jointly and severally liable under the head lease and accounts for the sublease as an operating lease. The lease term is now expected to end in May 2023.

During the year ended December 31, 2021 and 2020, the Company recognized sublease income of $1.8 million and $0.9 million, which is presented in other income in the accompanying consolidated statement of operations and comprehensive loss, respectively.

The components of operating lease costs were as follows (in thousands):


	FOR THE YEAR ENDED DECEMBER 31,
	2021			2020
Operating lease costs	$	4,882		$	4,836
Short-term lease costs		27			19
Variable lease costs		2,582			2,222
Sublease income		(1,850	)		(861	)
	$	5,641		$	6,216

Variable lease costs were primarily related to operating expenses, taxes and utilities associated with the operating leases, which were assessed based on the Company’s proportionate share of such costs for the leased premises.

Additional lease information is summarized in the following table (in millions, except lease term and discount rate):


	FOR THE YEAR ENDED DECEMBER 31,
	2021			2020
Cash paid for amounts included in the measurement of operating lease liabilities	$	6.0		$	6.0
Weighted-average remaining lease term - operating leases (years)		7.9			8.9
Weighted-average discount rate - operating leases		10.1	%		10.3	%

Undiscounted cash flows used in calculating the Company’s operating lease liabilities and amounts to be received under the sublease at 35 CambridgePark Drive and 4 Hartwell Place as of December 31, 2021 are as follows (in thousands):


Fiscal Year	OPERATING LEASE PAYMENTS			SUBLEASE RECEIPTS		NET OPERATING LEASE PAYMENTS
2022	$	6,252		$	2,821	$	3,431
2023		6,436			1,962		4,474
2024		6,625			936		5,689
2025		6,820					6,820
2026		7,020					7,020
Thereafter		21,779					21,779
Total undiscounted cash flows	$	54,932		$	5,719	$	49,213
Less: Amounts representing interest		(17,387	)
Present value of lease liabilities	$	37,545