11. Facility Lease

In January 2015, the Company signed an initial operating lease, effective February 1, 2015 for 8,138 square feet of office and laboratory space with a one year term. Between January 2015 and October 2018, the Company entered into a series of lease amendments to increase the amount of leased space to 27,280 square feet and extend the expiration of the lease to February 2023. The lease agreement includes annual rent escalations. Under the lease and subsequent amendments, the landlord provided approximately $1.9 million in free rent and lease incentives. The Company records rent expense on a straight-line basis over the effective term of the lease, including any free rent periods and incentives. In calculating the present value of the lease payments, the Company has utilized its incremental borrowing rate. The Company’s facility lease is a net lease, as the non-lease components (i.e. common are maintenance) are paid separately from rent based on actual costs incurred. Therefore, the non-lease components were not included in the right-of-use asset and liability and are reflected as an expense in the period incurred.

As of March 31, 2019 and December 31, 2018, the right-of-use asset under operating lease was $2.8 million and $0, respectively. The elements of lease expense were as follows (in thousands):


	Three Months Ended
	March 31,
	2019		2018
Operating lease cost
Base rent expense	$	249	$	177
Common area maintenance		81		75
Total operating lease cost	$	330	$	252
Other Information
Operating cash flows used for operating lease	$	359	$	356
Operating lease liabilities arising from obtaining right-of-use asset		3,769		—
Remaining lease term		3.8 years		2.8 years
Discount rate		10.0%		—

As of March 31, 2019, minimum rental commitments under this lease are as follows (in thousands):


Year Ended December 31 (in thousands)
2019*	$	845
2020		1,159
2021		1,260
2022		1,299
Total lease payments	$	4,563
Less: imputed interest		(794)
Total	$	3,769

* Remainder of the year

As of December 31, 2018, minimum rental commitments under this lease are as follows (in thousands):


Year Ended December 31 (in thousands)
2019	$	1,110
2020		1,142
2021		1,251
2022		1,296
2023		109
Total	$	4,908