The Company has operating leases for its current corporate offices, laboratory space, manufacturing facility, and dedicated space in a vivarium in South San Francisco, California, as well as for an additional facility in South San Francisco that the Company plans to use for corporate offices, laboratories and manufacturing. Rent expense, which is recognized on a straight-line basis over the term of each lease, was $0.7 million and $1.9 million for the three and nine months ended September 30, 2021, respectively, and $0.5 million and $1.4 million for the three and nine months ended September 30, 2020, respectively. The total cash paid for operating leases included in the operating cash flows was $0.6 million and $1.6 million for the three and nine months ended September 30, 2021, respectively, and $0.4 million and $1.3 million for the three and nine months ended September 30, 2020, respectively. The weighted-average remaining lease term was 6.9 years for the corporate office and laboratory space leases as of September 30, 2021. The weighted-average discount rate was 9.1% as of September 30, 2021.

In May 2018, the Company entered into a lease agreement for its corporate office and laboratory space located in South San Francisco, California with an expiration date in May 2025 (the “Initial Lease Agreement”). In April 2019, the Company executed the first amendment to the Initial Lease Agreement for additional corporate space, laboratory space and manufacturing capabilities and an extension to the lease term through April 2026.

In May 2020, the Company signed a second amendment to the Initial Lease Agreement. The amended lease provides for an eight-year non-cancelable lease of additional office and laboratory space in the same building. The lease amendment for additional office and laboratory space provided for abatement of rent during the first three months of the lease and contains rent escalations during the term of the lease. The lease for this additional space commenced in January 2021 and expires in January 2029. The lease amendment also includes an extension of the lease term for the existing office and laboratory space beginning on May 1, 2020 and expiring in January 2029. The amendment to the Initial Lease Agreement also includes an option to extend the lease for an additional seven-year term.

In January 2021, the Company signed a third amendment to the Initial Lease Agreement which provides for lease of additional space in the same building. The lease amendment for this additional space commenced in April 2021 and expires in March 2024.

In October 2021, the Company signed a fourth amendment to the Initial Lease Agreement which provides for lease of additional space in the same building. The lease for additional office and laboratory space provides for abatement of rent during the first two months of the lease and contains rent escalations during the term of the lease. The lease amendment of this additional space is anticipated to commence in April 2022 and expires in January 2029. The Company expects to pay base rent of approximately $4.6 million over the lease term. The lease amendment also includes this additional space in the Company’s option to extend the amended Initial Lease Agreement for an additional seven-year term. The other terms of the Initial Lease Agreement, as amended, remain unchanged.

In July 2021, the Company entered into a lease agreement for corporate office, manufacturing and laboratory space located in South San Francisco, California with an expiration date approximately twelve years after the lease commencement date (the “Additional Lease Agreement”). The Company will become responsible for paying rent on the lease commencement date. The Company’s monthly installment of base rent for the new premises will start at approximately $0.6 million commencing on the lease commencement date and will increase on an annual basis up to a maximum monthly base rent of approximately $0.8 million. The Company expects to pay base rent of approximately $98.8 million over the lease term. In addition to base rent, the Company is responsible for payment of direct expenses, which include operating, insurance and tax expenses. The lease also provides for certain tenant improvement allowances of up to approximately $25.2 million for tenant improvements and certain infrastructure upgrades in connection with the initial buildout of the premises, approximately $4.4 million of which, if utilized, would need to be repaid by the Company over the lease term. During the three months ended September 30, 2021, the Company delivered a security deposit in the form of a letter of credit of $1.6 million to the Landlord in connection with the Additional Lease Agreement.

On November 5, 2021, the Company entered into an amendment to its corporate office, manufacturing and laboratory facilities lease. The lease amendment expressly includes manufacturing as a permitted use at the facility, clarifies that Silicon Valley Bank is an acceptable bank for purposes of issuing a letter of credit under the lease, revises the letter of credit transferability terms and replaces the form of letter of credit attached to the lease.

Maturities of operating lease liabilities under existing operating leases as of September 30, 2021 were as follows (in thousands):

Year ending December 31,	Amount
2021 (remaining three months)	$	629
2022		2,579
2023		2,432
2024		2,184
2025		2,200
2026 and thereafter		7,321
Total future minimum lease payments		17,345
Less imputed interest		(4,534	)
Present value of net minimum lease payments	$	12,811
Operating lease liabilities:
Current		2,463
Non-current		10,348
Total lease liability	$	12,811