We lease our corporate headquarters in South San Francisco, California under a non-cancellable lease agreement. In December 2021, we entered into a second amendment with the landlord to extend the lease term through May 2025. The amended lease agreement does not include an option to extend the lease term. In connection with the amended lease, we are required to maintain a letter of credit in the amount of $0.1 million to the landlord, a decrease of $0.1 million from the prior lease agreement, and which expires and is renewed every 12 months, and is classified as restricted cash in our consolidated balance sheet. As of December 31, 2021, we were still working to update our letter of credit and continued to report an amount of $0.2 million as restricted cash related to this letter of credit on our consolidated balance sheet.

In March 2021, we entered into a new lease agreement for approximately 33,659 square feet of office, lab and warehouse space in Thousand Oaks, California. During the third quarter of 2021, the initial 10.5-year lease term commenced, upon substantial completion of the landlord’s work as defined under the agreement. The contractual obligations during the initial lease term are $21.0 million in aggregate. Base rent is subject to annual increase of 3% with each annual anniversary of the rent commencement date. We have the option to extend this lease for two additional five-year periods after the initial term.

In February 2017, we entered into a lease agreement for approximately 90,580 square feet of office, lab and cellular therapy manufacturing space in Thousand Oaks, California. The initial 15-year term of the lease commenced on February 15, 2018, upon the substantial completion of landlord’s work as defined under the agreement. The contractual obligations during the initial term are $16.4 million in aggregate. We have the option to extend the lease for two additional periods of ten and nine years, respectively, after the initial term. In connection with the lease, we were required to issue a letter of credit in the amount of $1.2 million to the landlord, which is recorded as long-term restricted cash in our consolidated balance sheet.

In November 2018, we entered into a lease agreement for additional office space in Thousand Oaks, California that expires in February 2026 and for which we have the option to extend the lease for an additional period of five years after the initial term. Additionally, in 2021, we entered into an amended lease agreement for our office and lab space in Aurora, Colorado, to add additional lab space. Incremental contractual obligations under the lease amendment are $0.2 million, and the lease term continues to expire in April 2024.

The maturities of lease liabilities under our operating and finance leases as of December 31, 2021 were as follows:

	Operating Leases				Finance Leases
Years Ending December 31,		(in thousands)
2022			5,171			$	181
2023			5,265				29
2024			5,183				—
2025			4,806				—
2026			3,257				—
Thereafter			19,004				—
Total lease payments		$	42,686			$	210
Less: amount representing interest			(14,586	)			(10	)
Present value of lease liabilities		$	28,100			$	200

Balance as of December 31, 2021
Other current liabilities		$	2,582			$	171
Operating lease liabilities - long-term			25,518				—
Other long-term liabilities			—				29
Total		$	28,100			$	200

	Year Ended		Year Ended		Year Ended
	December 31, 2021		December 31, 2020		December 31, 2019
	(in thousands)				(in thousands)
Operating lease cost:
Operating lease cost	$	3,827	$	3,020	$	2,578
Short-term lease cost		836		987		770
Total operating lease cost	$	4,663	$	4,007	$	3,348
Finance lease cost:
Amortization expense	$	244	$	389	$	324
Interest on lease liabilities		29		60		56
Total finance lease cost	$	273	$	449	$	380

	Year Ended			Year Ended			Year Ended
	December 31, 2021			December 31, 2020			December 31, 2019
	(in thousands, except lease term and discount rate)
Supplemental Cash Flows Information
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$	3,738		$	2,878		$	2,346
Operating cash flows for finance leases		32			62			50
Financing cash flows for finance leases		254			389			486

Operating lease assets obtained in exchange for lease obligations:	$	13,427		$	—		$	838
Finance lease assets obtained in exchange for lease obligations:		—			281			323
Non-cash increase to operating lease assets due to remeasurement of lease liabilities:		1,760			639

Weighted Average Remaining Lease Term
Operating leases	9.2 years			9.4 years			10.3 years
Finance leases	1.0 years			1.7 years			2.5 years
Weighted Average Discount Rate
Operating leases		9.6	%		10.3	%		10.4	%
Finance leases		9.7	%		9.7	%		10.0	%

The Company’s ARO consists of a contractual requirement to remove the tenant improvements at our manufacturing facility in Thousand Oaks, California and restore the facility to a condition specified in the lease agreement. The Company records an estimate of the fair value of its ARO in long-term liabilities in the period incurred. The fair value of the ARO is also capitalized in property and equipment, net and depreciated over the lease term. The fair value of our ARO was estimated by discounting projected cash flows over the estimated life of the related assets using our credit adjusted risk-free rate.