The Company has facility leases for office space under non-cancellable and cancellable operating leases with various expiration dates through 2032 and equipment under a non-cancellable operating lease with a term expiring in 2026. Total lease costs were approximately $3.2 million and $5.9 million, including operating lease costs of $2.4 million and $4.3 million, variable lease costs of $918,000 and $1.8 million, and sublease income of $132,000 and $216,000, during the three and six months ended June 30, 2024, respectively. Total lease costs were approximately $2.8 million and $5.8 million, including operating lease costs of $1.9 million and $3.8 million and variable lease costs of $859,000 and $2.0 million, during the three and six months ended June 30, 2023, respectively. The Company paid $4.1 million and $2.6 million in cash for operating leases, net of sublease income, that is included in the operating activities section of the condensed consolidated statements of cash flows for the six months ended June 30, 2024 and 2023, respectively.

The weighted-average remaining lease term and the weighted-average discount rate of the Company’s operating leases were 7.81 years and 8.96%, respectively, at June 30, 2024. The weighted-average remaining lease term and the weighted-average discount rate of the Company’s operating leases were 8.29 years and 8.95%, respectively, at December 31, 2023. The weighted-average remaining lease term does not include any renewal options at the election of the Company.

The Company’s lease agreements do not contain any material residual value guarantees or material restrictive covenants.

In September 2020, the Company entered into a lease agreement for 59,407 square feet of laboratory and office space in San Diego, California, which represented a portion of a new facility that was under construction and which was subsequently amended in March 2021 to expand the rented premises by 18,421 square feet (the 2020 Lease). The construction and design of the asset was the primary responsibility of the lessor. The Company was involved in certain aspects of construction and design for certain interior features and leasehold improvements that is beneficial to the Company to better suit its business needs and intended purpose of the space. The lease is accounted for as an operating lease and commenced in August 2021. In April 2022, the 2020 Lease was modified to amend the rent commencement date from February 2022 to May 2022. The 2020 Lease, as amended, has a term of 10.75 years and includes aggregate monthly payments to the lessor of approximately $51.6 million beginning in May 2023 with a rent escalation clause, and a tenant improvement allowance of approximately $16.8 million. The Company is responsible for its share of operating expenses based on actual operating expenses incurred by the landlord. The 2020 Lease is cancellable at the Company’s request after the 84th month with 12 months written notice and a lump-sum cancellation payment of $2.5 million. The termination option has not been included in the Company's operating lease assets and liabilities. As discussed in Note 2, the Company provided a letter of credit to the lessor for $408,000, which expires July 29, 2032.

In December 2021, the Company entered into a lease agreement for 29,542 square feet of office and laboratory space in South San Francisco, California. The lease is accounted for as an operating lease with the associated operating lease assets and liabilities recorded upon commencement, which occurred in July 2022. The non-cancellable operating lease has an initial term of 124 months with an option to extend the lease term by 5 years at the then-current market rates and includes aggregate monthly payments to the lessor of approximately $34.4 million beginning in November 2022 with a rent escalation clause and a tenant improvement allowance of approximately $8.2 million. The renewal option has not been included in the Company's operating lease assets and liabilities. The Company is responsible for its share of operating expenses based on actual operating expenses incurred by the landlord. The construction and design of the tenant improvements was the primary responsibility of the lessor. While the Company was involved in certain aspects of construction and design for certain interior features and leasehold improvements that is beneficial to the Company to better suit its business needs and intended purpose of the space, all construction was handled directly by the landlord. The Company was not deemed to be the accounting owner of the tenant improvements prior to or after the construction period. All payments made by the Company for landlord-owned tenant improvements were recorded as prepaid rent on the condensed consolidated balance sheets prior to lease commencement and included in the operating lease asset upon lease commencement. In February 2022, the expected project costs exceeded the tenant improvement allowances by $5.1 million, which was paid directly to the landlord by the Company and was recorded as prepaid rent in the condensed consolidated balance sheets and as a cash outflow from operating activities in the condensed consolidated statements of cash flows. Upon lease commencement, the $5.1 million of prepaid rent was included in the operating lease asset. The Company paid a security deposit of $874,000 in December 2021 that was recorded as other assets in the condensed consolidated balance sheets.

In January 2024, the Company entered into an agreement to sublease the second floor of its corporate headquarters in San Diego, California. Pursuant to the agreement, the subleased space is approximately 10,000 square feet of office space with a sublease term of three years which includes an option for the subtenant to renew for an additional year and an early termination clause. The Company determined the sublease to be an operating lease. Therefore, the Company recognizes sublease income on a straight-line basis over the lease term in its condensed consolidated statements of operations and comprehensive loss as a reduction to operating lease costs because the sublease is outside of the Company's normal business operations. The Company will continue to account for the operating lease asset and related liability of the original lease as it did prior to the commencement of the sublease. The Company recorded a reduction to operating lease costs of $132,000 and $216,000 related to income from this sublease during the three and six months ended June 30, 2024, respectively.

In June 2024, the Company committed to a plan to sublease the first floor of its corporate headquarters in San Diego, California and in July 2024, the Company executed an agreement to sublease such space. Pursuant to the agreement, the subleased space is approximately 18,421 square feet of office space with a sublease term of 61 months beginning in October 2024, with early access in August 2024. The agreement includes an option for the subtenant to renew for an additional year and an early termination clause.

In connection with the sublease plan of the first floor, the Company reassessed its asset groups for testing long-lived assets for impairment and determined the first floor operating lease assets and related property and equipment represented an asset group separate from the entity wide asset group. The Company concluded that the carrying value of the first floor asset group was not recoverable as it exceeded the future net undiscounted cash flows that are expected to be generated from the use and eventual disposition of the assets within the asset group. The Company determined the fair value of the first floor asset group based on the income approach using a discounted cash flow model. The cash flows used in the model were discounted using a rate of 13.5%. Based on this analysis, the Company recognized a noncash impairment charge of $4.7 million, including $2.4 million for the operating lease assets and $2.3 million for the leasehold improvements and furniture, of which $3.0 million was recorded to research and development expense and $1.7 million was recorded to general and administrative expense during the three and six months ended June 30, 2024. This represents a Level 3 nonrecurring fair value measurement. Calculating the fair value of the asset group involves significant estimates and assumptions, including projected future cash flows and a discount rate. Changes in the estimates and assumptions used could materially affect the amount of impairment loss recognized in the period the asset group is considered impaired.

Future minimum lease payments under operating leases as of June 30, 2024 are as follows (in thousands):


Year ending December 31,
2024 (remaining six months)	$	4,426
2025		9,024
2026		9,170
2027		9,199
2028		9,277
Thereafter		35,098
Total lease payments	$	76,194
Less: Amount representing interest		(22,226	)
Operating lease liabilities	$	53,968