The Company’s lease portfolio is primarily comprised 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. 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 therefore the renewal options 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 our 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	56,859	March 2019 to May 2020	November 2025 to February 2028
South San Francisco, CA	66,075	December 2019 to September 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.

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
	(in thousands)
Operating lease cost	$	4,303	$	2,750	$	11,368	$	7,870
Short-term lease cost		-		474		512		1,418
Variable lease cost		1,286		837		4,015		2,306
Total lease cost	$	5,589	$	4,061	$	15,895	$	11,594

As of September 30, 2021, the weighted-average remaining lease term was 7.9 years and the weighted-average incremental borrowing rate was 9.55%.

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 September 30, 2021 (in thousands):

2021 (remaining 3 months)	$	2,867
2022		17,511
2023		17,677
2024		17,036
2025		17,151
2026 and thereafter		98,614
Total undiscounted lease payments		170,856
Less: imputed interest		(67,513	)
Less: tenant improvement allowances		(4,438	)
Present value of operating lease liabilities	$	98,905