The Company leases office space under agreements classified as operating leases. The Company’s active leases as of September 30, 2021 are for office and manufacturing space in Tucson, Arizona, which 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 during the nine months ended September 30, 2021.

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Operating leases
Operating lease cost	$	107,969	$	182,287	$	383,672	$	570,163
Variable lease cost		26,636		36,554		73,120		89,716
Operating lease expense		134,605		218,841		456,792		659,879

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

	Nine Months Ended September 30,
	2021			2020
Cash paid for amounts included in measurement of operating lease liabilities	$	403,012		$	665,095
Establishment of operating lease liabilities arising from obtaining right-of-use assets	$	1,302,457		$	21,078
Weighted-average remaining lease term – operating leases		3.3			1.9
Weighted-average discount rate – operating leases		5.8	%		9.6	%

Remaining maturities of the Company’s operating leases, excluding short-term leases, included in operating lease liabilities – non - current in the condensed consolidated balance sheets as of September 30, 2021 are as follows:

2021	$	111,441
2022		481,549
2023		484,719
2024		484,631
2025		40,382
Total		1,602,722
Less present value discount		(148,425	)
Total operating lease liabilities	$	1,454,297
Less operating lease liabilities - current		(398,313	)
Operating lease liabilities - non-current	$	1,055,984

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.

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Financing leases
Amortization of right-of-use assets	$	5,444	$	10,035	$	18,501	$	34,033
Interest on lease liability		1,369		2,092		4,544		7,074
Total financing lease cost	$	6,813	$	12,127	$	23,045	$	41,107

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

	Nine Months Ended September 30,
	2021			2020
Weighted-average remaining lease term – financing leases		3.0			3.5
Weighted-average discount rate – financing leases		9.77	%		9.77	%

As of September 30, 2021, remaining maturities of the Company’s financing leases are as follows:

2021	$	5,772
2022		20,715
2023		18,396
2024		16,080
Total		60,963
Less present value discount		(8,328	)
Financing lease liabilities, net	$	52,635

Financing lease liabilities net of discount of $52,635, of which $17,558 and $35,077 were included in other current liabilities and other non-current liabilities, respectively, and financing right-of-use assets of $48,269, were included in property and equipment, net, in the condensed consolidated balance sheet as of September 30, 2021.