In July 2017, the Company entered into a lease of office and laboratory space for its headquarters at 490 Arsenal Way in Watertown, Massachusetts (the “Watertown Lease”). The Watertown Lease commenced in April 2018 with rent commencing in May 2018. The Company recognized operating lease costs of $3.1 million and $3.0 million for the nine months ended September 30, 2020 and 2019, respectively.

The Company incurred approximately $0.5 million in costs for leasehold improvements for the nine months ended September 30, 2019. The Company incurred no costs for leasehold improvements for the nine months ended September 30, 2020. The Watertown Lease required the Company to provide collateral in the amount of $2.6 million, which is recorded as restricted cash on the accompanying condensed consolidated balance sheets.

As of December 31, 2019, assets under the Watertown Lease classified as right-of-use assets on the Company’s condensed consolidated balance sheet were $14.5 million, net of accumulated amortization. Liabilities under the Watertown Lease were $13.8 million, of which $0.9 million were classified as operating lease liability, current, and $12.9 million were classified as operating lease liability, net of current, on the Company’s condensed consolidated balance sheet.

As of September 30, 2020, assets under the Watertown Lease classified as right-of-use assets on the Company’s condensed consolidated balance sheet were $13.5 million, net of accumulated amortization. Liabilities under the Watertown Lease were $13.1 million, of which $1.0 million were classified as operating lease liability, current, and $12.1 million were classified as operating lease liability, net of current, on the Company’s condensed consolidated balance sheet.

Additionally, the Company recorded right-of-use amortization of $0.9 million for the nine months ended September 30, 2020 and 2019.

The elements of lease costs under the Watertown Lease were as follows (in thousands):

	THREE MONTHS ENDED SEPTEMBER 30,						NINE MONTHS ENDED SEPTEMBER 30,
	2020			2019			2020			2019
Lease cost:
Operating lease cost	$	637			637		$	1,912		$	1,912
Variable lease cost		419			366			1,207			1,087
Total lease cost		1,056			1,003			3,119			2,999
Other information:
Operating cash flows for operating liabilities	$	551			535		$	1,654		$	1,606
Operating lease liabilities arising from obtaining right-of- use assets		—			—			—			—
Weighted average remaining lease term	7.5 years			8.5 years			7.5 years			8.5 years
Weighted average discount rate		10	%		10	%		10	%		10	%

As of September 30, 2020, undiscounted minimum future lease payments under non-cancelable leases were as follows: (in thousands):

FUTURE OPERATING LEASE PAYMENTS
2020⁽¹⁾	$	551
2021		2,272
2022		2,340
2023		2,410
2024		2,483
Thereafter		8,833
Total lease payments		18,889
Less imputed interest		(5,792	)
Total operating lease liabilities at September 30, 2020	$	13,097

(1)	For the three months ended December 31, 2020.