In October 2014, the Company entered into an agreement to lease office and laboratory space at 130 Brookline Street in Cambridge, Massachusetts under an operating lease agreement with a term through January 2020, with an option to extend the term of the lease for an additional five-year period. In April 2019, the Company executed an amendment to the lease to extend the term of the lease for the additional five-year period, through January 2025. Upon the execution of the original lease, the Company provided a $0.3 million security deposit. The Company has recorded this security deposit in other assets on the condensed consolidated balance sheets.

In applying the ASC 842 transition guidance, the Company retained the classification of this lease as operating and recorded a lease liability and a right-of-use asset on the ASC 842 effective date with the five-year extension included in the lease term, based on the Company’s election of the hindsight practical expedient as the Company was reasonably certain to exercise this option term.

In March 2019, the Company entered into a separate agreement to sublease additional office and laboratory space at 130 Brookline Street in Cambridge, Massachusetts under an operating sublease agreement with a term through April 2021, with two options to extend the agreement by one year each, for a total option period of up to two years. Upon commencement of the lease in April 2019, the Company recognized a right-of-use asset and lease liability of approximately $1.3 million.

In January 2016, the Company entered into a ten-year agreement to lease office and laboratory space at 40 Erie Street in Cambridge, Massachusetts under an operating lease agreement, with an option to terminate the lease at the end of the sixth year and an option to extend the term of the lease for an additional three years. Upon the execution of this lease, the Company provided a $2.2 million security deposit, which has been recorded in other assets on the condensed consolidated balance sheets. In addition, the Company had prepaid $2.2 million in lease payments as of December 31, 2018 under the terms of this lease. In applying the ASC 842 transition guidance, the Company retained the classification of this lease as operating and recorded a lease liability and a right-of-use asset, based on the present value of the non-cancelable term, on the ASC 842 effective date.

The Company has also entered into leases that are not related to office space, including one for a manufacturing-related facility. These leases are accounted for in accordance with ASC 842 and are not material to the Company’s condensed consolidated financial statements.

Throughout the term of its leases, the Company is responsible for paying certain costs and expenses, in addition to the rent, as specified in the lease, including a proportionate share of applicable taxes, operating expenses and utilities. The variable portion of these costs are expensed as incurred and are disclosed as variable lease cost.

The following table contains a summary of the lease costs recognized under ASC 842 and other information pertaining to the Company’s operating leases for the three and nine months ended September 30, 2019:

	Three Months Ended		Nine Months Ended
	September 30, 2019
	(in thousands)
Lease cost
Operating lease cost	$	1,902	$	5,485
Short-term lease cost		12		12
Variable lease cost		615		1,612
Total lease cost	$	2,529	$	7,109

	Nine months ended
	September 30, 2019
	(in thousands)
Other information
Operating cash flows used for operating leases	$			4,784
Operating lease liabilities arising from obtaining right-of-use assets				2,554

	As of September 30, 2019
Lease term and discount rate
Weighted average remaining lease term	3.2 years
Weighted average discount rate	9.00%

Future minimum lease payments under the Company’s non-cancelable operating leases as of September 30, 2019, are as follows:

Future Operating Lease Payments
Year Ending December 31,	(in thousands)
2019 (excluding the nine months ended September 30, 2019)	$	1,692
2020		7,113
2021		7,350
2022		4,733
2023		871
Thereafter		943
Total lease payments	$	22,702
Less: imputed interest		(3,055	)
Total operating lease liabilities at September 30, 2019	$	19,647

Future minimum lease payments under the Company’s non-cancelable operating leases as of December 31, 2018, are as follows:

Year Ending December 31,	(In thousands)
2019	$	5,616
2020		4,963
2021		5,507
2022		3,861
	$	19,947