We lease three facilities for office and laboratory space in Cambridge, Massachusetts that represent substantially all of our lease obligations. An overview of these significant leases are as follows:

In April 2015, we entered into a non-cancelable real property lease for approximately 295,000 square feet of laboratory and office space located at 675 West Kendall Street, Cambridge, Massachusetts. We intend to move our corporate headquarters and research facility to this location in 2019. The lease commenced on May 1, 2018 and monthly rent payments became due commencing on February 1, 2019 upon substantial completion of the building improvements, and continue for 15 years, with options to renew for two terms of five years each. Exercise of these options was not determined to be reasonably certain and thus was not included in the operating lease liability on the condensed consolidated balance sheet as of March 31, 2019.

We lease approximately 129,000 square feet of office and laboratory space located at 300 Third Street, Cambridge, Massachusetts, which to date has served as our corporate headquarters under a non-cancelable real property lease agreement dated as of September 26, 2003, as amended. The term of the lease expires on January 31, 2034, with an option to extend for two additional five-year terms. Exercise of these options was not determined to be reasonably certain and thus was not included in the operating lease liability on the condensed consolidated balance sheet as of March 31, 2019.

In March and May 2015, we entered into non-cancelable real property lease agreements for approximately 72,000 square feet of office space located on several floors at 101 Main Street, Cambridge, Massachusetts that will expire in March 2024 and June 2021, respectively, each with an option to renew for one five-year term. Exercise of these options was not determined to be reasonably certain and thus was not included in the operating lease liability on the condensed consolidated balance sheet as of March 31, 2019.

Our facility leases described above generally contain customary provisions allowing the landlords to terminate the leases if we fail to remedy a breach of any of our obligations under any such lease within specified time periods, or upon our bankruptcy or insolvency.

The below table summarizes our costs included in operating expenses related to leases we have entered into through March 31, 2019:

Lease Cost	For the Three Months Ended March 31,
Operating lease cost	$	9,290
Variable lease cost		5,047
Total	$	14,337

Short-term lease costs were not material for the three months ended March 31, 2019.

Net cash paid for the amounts included in the measurement of the operating lease liability on our condensed consolidated balance sheet and included in accrued expenses and other within operating activities in our condensed consolidated statement of cash flow was $7.1 million for the period ending March 31, 2019. The weighted-average remaining lease term and weighted-average discount rate for all leases as of March 31, 2019 was 13.9 years and 8.2%, respectively.

Future lease payments for non-cancellable operating leases as of March 31, 2019 and a reconciliation to the carrying amount of the operating lease liability presented in the condensed consolidated balance sheet as of March 31, 2019 is as follows:

Year Ending December 31,
2019 (excluding the three months ended March 31, 2019)	$	11,125
2020		34,530
2021		35,776
2022		35,880
2023		35,575
2024		34,674
2025 and thereafter		356,211
Total undiscounted payments due under non-cancellable operating leases		543,771
Less imputed interest		(244,494	)
Total	$	299,277

Current operating lease liability	$	16,977
Non-current operating lease liability		282,300
Total	$	299,277

Under the prior lease guidance, minimum payments under our non-cancelable facility leases, as of December 31, 2018, were approximately as follows, in thousands:

Year Ending December 31,
2019	$	32,228
2020		34,826
2021		34,410
2022		34,826
2023		35,270
Thereafter		390,455
Total	$	562,015