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. Refer to Note 11, Subsequent Event, for additional information regarding this lease amendment. 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. No right-of-use asset or lease liability has been recorded for this lease as of March 31, 2019, as the lease does not commence until April 2019. The Company estimates that at commencement it will recognize a right-of-use asset and lease liability between $1.0 million and $1.5 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 on the ASC 842 effective date.

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 Topic 842 and other information pertaining to the Company’s operating leases for the three months ended March 31, 2019:

	(in thousands)
Lease cost
Operating lease cost	$	1,703
Variable lease cost		537
Total lease cost	$	2,240

Other information
Operating cash flows used for operating leases	$	1,487
Operating lease liabilities arising from obtaining right-of-use assets		-
Weighted average remaining lease term	3.9 years
Weighted average discount rate		9.00	%

Future minimum lease payments under the Company’s non-cancelable operating leases as of March 31, 2019, are as follows:

Future Operating Lease Payments
Year Ending December 31,	(in thousands)
2019 (excluding the three months ended 3/31/19)	$	4,980
2020		6,483
2021		6,618
2022		4,733
2023		871
Thereafter		943
Total lease payments	$	24,628
Less: imputed interest		(3,655	)
Less: leases not yet commenced		(1,460	)
Total operating lease liabilities at March 31, 2019	$	19,513

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
Thereafter		-
	$	19,947