In June 2018, the Company signed a lease agreement to lease approximately 105,000 square feet in office and laboratory space in South San Francisco which serves as the Company’s headquarters (the “Headquarters”). The lease expires in 2029 with an option to renew for a period of ten years. The landlord paid for $15.7 million of tenant improvements. In connection with the lease, the Company entered into a letter of credit arrangement in the amount of $1.5 million as collateral for the lease, which is classified as restricted cash on the consolidated balance sheets. In October 2020, the Company signed a lease agreement to lease approximately 18,700 square feet of office and laboratory space in Newark, California. The lease term ends on February 6, 2028 with an option to extend for an additional five years. The landlord is obligated to pay for up to $0.4 million of tenant improvements. The measurement of the lease liabilities for the leases excludes the options to extend the term of the lease as such extensions are not reasonably certain to occur. Variable lease costs for all of the Company’s leases consist of operating expenses for the spaces.

In May 2019, the Company entered into an agreement to sublease approximately 25,000 square feet of the Headquarters (the “Sublease”), which was amended to approximately 23,600 square feet in December 2020. The Sublease expires in November 2021. The sublessor has the option to extend the Sublease for one additional year subject to the consent of the Company. The sublessee is required to pay its proportionate share of operating expenses for the space.

In June 2019, in connection with the Sublease, the Company evaluated the related right-of-use asset for impairment. The lease costs plus amortization expense of the leasehold improvements in the subleased space exceeded the sublease income over the remaining sublease term. As such, the Company recorded an impairment charge of $1.2 million in general and administrative expenses to write-down the right-of-use asset such that no loss is expected to be recognized over the sublease period.

	December 31,
	2020			2019
	(In thousands)
Operating lease cost	$	5,589		$	5,875
Variable lease cost		2,255			1,328
Short-term lease cost		—			68
Sublease income and reimbursement of variable lease cost		(2,288	)		(1,263	)
Total	$	5,556		$	6,008

Rent expense under legacy guidance for the year ended December 31, 2018 was $1.1 million.

As of December 31, 2020, the weighted-average remaining lease term for operating leases was 8.2 years and the weighted-average discount rate was 8.5%. Cash paid for amounts included in the measurement of lease liabilities for the year ended December 31, 2020 and 2019 was $6.9 million and $3.2 million, respectively, was included in net cash used in operating activities in our consolidated statements of cash flows.

The following are the lease payments owed under the Company’s operating leases as of December 31, 2020:

	(In thousands)
2021	$	7,872
2022		8,171
2023		8,436
2024		8,732
2025		9,037
Thereafter		30,130
Total undiscounted lease payments	$	72,378
Less: Present value adjustment		(21,122	)
Total lease liability	$	51,256