The Company’s lease portfolio is primarily composed of operating leases for office, laboratory, non-good manufacturing practices (GMP) pilot plant manufacturing, and industrial space located in Seattle, WA, Cambridge, MA, South San Francisco, CA, and Fremont, CA. Our operating leases have contractual periods expiring between April 2024 and November 2031. These leases contain various rent abatement periods, after which they require monthly lease payments that may be subject to annual increases throughout the lease term. The Seattle and South San Francisco lease agreements each provide the Company with the option to renew for an additional period of five years. The Company is not reasonably certain it will renew these leases, and the renewal options therefore are not considered in the remaining lease term for these leases. The industrial space located in Fremont, CA will be used for the construction of a GMP manufacturing facility. The lease agreement initial term is ten years and includes the option to extend for up to two additional five-year terms. The Company anticipates that it will exercise both options to extend. Certain leases provide the Company with the right to make tenant improvements, including the addition of laboratory space or build-out of manufacturing

capabilities, and include a lease incentive allowance. The following table contains additional information related to the Company’s operating leases:

Location	Approximate Square Footage	Commencement Dates	Expiration Dates
Seattle, WA	48,086	March 2019 to September 2020	December 2026 to April 2028
Cambridge, MA	59,639	March 2019 to May 2020	November 2025 to February 2028
South San Francisco, CA	66,075	December 2019 to November 2021	April 2024 to April 2030
Fremont, CA	163,193	July 2021	November 2031

Throughout the term of the lease agreements, the Company is responsible for paying certain operating costs in addition to rent, such as common area maintenance, taxes, utilities, and insurance. These additional charges are considered variable lease costs and are recognized in the period in which the costs are incurred.

	Year Ended December 31,
	2021		2020		2019
	(in thousands)
Operating lease cost	$	16,425	$	10,757	$	4,898
Short-term lease cost		512		1,886		3,710
Variable lease cost		5,230		3,081		1,494
Total lease cost	$	22,167	$	15,724	$	10,102

As of December 31, 2021, the weighted-average remaining lease term was 9.88 years and the weighted-average IBR was 9.15%.

The following table reconciles the Company’s undiscounted operating lease cash flows by fiscal year to the present value of the operating lease liabilities as of December 31, 2021 (in thousands):

2022		19,954
2023		21,511
2024		20,601
2025		20,449
2026		17,701
2026 and thereafter		80,913
Total undiscounted lease payments		181,129
Less: imputed interest		(66,291	)
Less: tenant improvement allowances		(3,895	)
Present value of operating lease liabilities	$	110,943