Leases (Tables)

9 Months Ended

Sep. 30, 2020

Lessee Lease Description [Line Items]

Undiscounted Minimum Future Lease Payments Under Non-cancelable Leases

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.

Watertown Lease

Lessee Lease Description [Line Items]

Summary of Lease Costs

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	%