The Company leases office space under agreements classified as operating leases. The Company’s active leases as of December 31, 2021 relate to the Company’s office and manufacturing space in Tucson, Arizona, and expire in 2025. The Company’s leases do not include any contingent rental payments, impose any financial restrictions, or contain any residual value guarantees.

The Company amended its Tucson facility leases in December 2020 to extend the terms of the leases for one year, through January 31, 2022 and again in September 2021 to extend the terms of the leases for three years, through January 31, 2025. The lease extensions were treated as lease modifications for accounting purposes, and allow for an additional extension of two years on the same terms and conditions of the existing amended lease agreement, except that the lease rates would be adjusted to reflect lease rates applicable to like-kind buildings within the market at the time that the Company elects to exercise the extension options, but in no event less than the last applicable rental rate. The Company has not accounted for these renewal options in the calculation of the lease liabilities and right-of-use assets as the Company is not reasonably certain to exercise the options.

In the first quarter of 2021, the Company closed its development laboratory in San Carlos, California and, as a result, $0.2 million of operating right-of-use assets related to the abandonment of the laboratory were written off to research and development expense for the year ended December 31, 2021.

Variable expenses generally represent the Company’s share of the landlord’s operating expenses and are recorded when incurred. Incremental borrowing rates used to discount future lease payments in calculating lease liabilities were estimated by reference to the rates for similar length secured lines of credit to the Company’s lease agreements provided by the Company’s lenders at the time that the lease liabilities were recorded, as these rates represented the cost of borrowing for secured loans of similar duration. The Company does not have any operating lease arrangements where it acts as a lessor.

	Years Ended December 31,
	2021		2020
Operating leases
Operating lease cost	$	503,130	$	752,413
Variable lease cost		88,708		125,792
Total rent expense	$	591,838	$	878,205

The table below summarizes other information related to the Company’s operating leases:

	Years Ended December 31,
	2021			2020
Cash paid for amounts included in measurement of operating lease liabilities	$	514,453		$	883,252
Establishment of operating lease liabilities arising from obtaining right-of-use assets	$	1,302,457		$	447,987
Weighted-average remaining lease term – operating leases		3.1			1.7
Weighted-average discount rate – operating leases		5.8	%		8.0	%

As of December 31, 2021, remaining maturities of the Company’s operating leases are as follows:

2022	$	481,548
2023		484,719
2024		484,631
2025		40,382
Total		1,491,280
Less present value discount		(127,954	)
Total operating lease liabilities		1,363,326
Less operating lease liabilities – current		(413,865	)
Operating lease liabilities - non-current	$	949,461

The Company has a number of computer and copier equipment leases that are classified as financing leases. Incremental borrowing rates used to discount future lease payments in calculating lease liabilities were estimated by reference to information received by the Company from bankers regarding estimated current borrowing rates for collateralized loans with similar amount and duration as the leases. The Company does not have any material financing leases where it acts as a lessor. The components of lease cost for financing leases were as follows:

	Years Ended December 31,
	2021		2020
Financing leases
Amortization of right-of-use assets	$	23,118	$	42,826
Interest on lease liability		5,793		8,938
Total financing lease cost	$	28,911	$	51,764

The table below summarizes other information related to the Company’s financing leases:

	Years Ended December 31,
	2021			2020
Weighted-average remaining lease term – financing leases		2.8			3.4
Weighted-average discount rate – financing leases		9.77	%		9.77	%

As of December 31, 2021, remaining maturities of the Company’s financing leases are as follows:

2022	$	20,716
2023		18,396
2024		16,080
Total		55,192
Less present value discount		(7,081	)
Financing lease liabilities, net	$	48,111

Financing lease liabilities net of discount of $48,111, of which $16,807 and $31,304 were included in other current liabilities and other non-current liabilities, respectively, and financing right-of-use assets of $43,651, were included in property and equipment, net, in the consolidated balance sheet as of December 31, 2021.