Leases

The Company leases office and research and development facilities and equipment under various non-cancellable operating lease agreements.

In January 2010, the Company entered into a lease for office and laboratory space in Malvern, Pennsylvania (the “Malvern Lease”). The Malvern Lease commenced in March 2010 and was amended to extend its term to July 31, 2018 and again to September 30, 2023, with an option to extend the lease for an additional three years. This lease contains escalating rent payments. In December 2018, the Company entered into a lease for office space in San Diego, California, which expires in October 2022. As of December 31, 2019, the weighted average remaining lease term for the Company’s leases was 6.1 years, and the weighted average discount rate used to determine the right-of-use assets and corresponding operating lease liabilities was 6.4%.

Maturities of operating lease liabilities as of December 31, 2019 are as follows:



Year Ending December 31,
2020	$	372
2021	377
2022	363
2023	272
2024	278
Thereafter	498
Total future minimum lease payments	2,160
Less: Present value adjustment	(387		)
Operating lease liabilities	$	1,773

The Company recognizes rent expense for the operating leases on a straight-line basis. The Company accounts for the difference between the minimum lease payments and the straight-line amount as deferred rent and records it as an offset to operating lease right-of-use assets. Rent expense was $0.5 million and $0.4 million for the years ended December 31, 2019 and 2018, respectively.