The Company leases office space under agreements classified as operating leases. The Company’s active leases as of December 31, 2022 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 September 2021 to extend the terms of the leases for three years through January 31, 2025. The lease extension was treated as a lease modification for accounting purposes, and allows 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 fourth quarter of 2022, the Company recorded an increase to its operating lease liability as the result of leasehold improvements financed by the landlord, to be repaid in equal installments over the remaining term of the lease.

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.

The components of lease cost for operating leases were as follows:


	Years Ended December 31,
	2022		2021
Operating leases
Operating lease cost	$	483,956	$	503,130
Variable lease cost		99,989		88,708
Total rent expense	$	583,945	$	591,838

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


	Years Ended December 31,
	2022			2021
Cash paid for amounts included in measurement of operating lease liabilities	$	487,673		$	514,453
Establishment of operating lease liabilities arising from obtaining right-of-use- assets		77,385			1,302,457
Weighted-average remaining lease term – operating leases		2.1			3.1
Weighted-average discount rate – operating leases		5.8	%		5.8	%

Remaining maturities of the Company’s operating leases, included in operating lease liabilities – current and operating lease liabilities - non-current, net of discount, in the consolidated balance sheets as of December 31, 2022, are as follows:


2023	$	521,467
2024		521,379
2025		43,444
Total		1,086,290
Less present value discount		(64,840	)
Total operating lease liabilities		1,021,450
Less operating lease liabilities - current		(475,126	)
Operating lease liabilities - non-current	$	546,324

The Company has a small 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 did not have any material financing leases as of either the year ended December 31, 2022 or 2021.