2018 Operating Lease. In February 2018, as amended in March 2018, the Company entered into a non-cancelable operating lease for a facility in San Diego, California. The lease has an initial term of seven years which expires in August 2025, and the Company has an option to extend the term of the lease for an additional five years and has a termination option subject to early termination fees. The lease is subject to base lease payments and additional charges for common area maintenance and other costs and includes certain lease incentives and tenant improvement allowances. Rent expense is being recognized on a straight-line basis over the term of the lease. The Company’s estimated incremental borrowing rate of 8.0% was used in its present value calculation as the facility lease does not have a stated rate, and the implicit rate was not readily determinable.

Under the terms of the lease, the Company provided the lessor with an irrevocable letter of credit in the amount of $0.5 million. The lessor is entitled to draw on the letter of credit in the event of any default by the Company under the terms of the lease.

Future Minimum Payments. As of June 30, 2020, future minimum payments under non-cancellable operating leases were as follows (in thousands):

Year ending December 31,	Minimum Payments
2020 (6 months)	$	571
2021		1,173
2022		1,208
2023		1,244
2024		1,280
Thereafter		871
Total future minimum lease payments		6,347
Less imputed interest		1,121
Total operating lease liability		5,226
Less operating lease liability, current		782
Operating lease liability, non-current	$	4,444

Rent expense was $0.2 million and $0.5 million for the three and six months ended June 30, 2020, respectively; for the three and six months ended June 30, 2019, the Company recognized rent expense of $0.3 million and $0.5 million, respectively.

Cash paid for amounts included in the measurement of lease liabilities for operating cash flow from operating leases was $0.6 million and $0.5 million during the six months ended June 30, 2020 and 2019, respectively.