In June 2015, the Company entered into a lease agreement for the lease of research facility space with a commencement date of November 15, 2015 (the “2015 Lease”). The lease expires in February 2022. The 2015 Lease contains escalating rent clauses which require higher rent payments in future years. With the adoption of ASC 842, the Company has recorded a right-of-use asset and corresponding lease liability.

In May 2016, the Company entered into a sublease agreement for its primary office and research facility in Cambridge, Massachusetts, with a commencement date of December 23, 2016 (the “2016 Sublease”). The sublease expires in December 2026, and the Company has an option to extend the term of sublease for an additional five-year period if, at the time of expiration of the initial term, the sublessor does not intend to utilize the space for itself or its affiliates. The 2016 Sublease contains escalating rent clauses which require higher rent payments in future years. With the adoption of ASC 842, the Company has recorded a right-of-use asset and corresponding lease liability. The right-of-use asset and corresponding lease liability does not include the additional five-year period under the option.

In May 2019, the Company entered into a lease agreement for office facility space with a commencement date of June 1, 2019 (the “2019 Lease”). The lease expires in November 2026, and the Company has an option to extend the term of the lease for an additional five-year period based on certain conditions within the Company’s control. The 2019 Lease contains escalating rent clauses which require higher rent payments in future years. At lease commencement, the Company recorded a right-of-use asset and corresponding lease liability. The right-of-use asset and corresponding lease liability does not include the additional five-year period under the option.

In addition, the Company rents certain office space in Zug, Switzerland, on a short-term basis for which a right-of-use asset and liability are not recorded, in accordance with the practical expedient elected.

The Company has embedded leases in certain research and license agreements for which the Company has recorded a right of use asset and liability. These arrangements are not significant in comparison to the Company’s total operating lease assets and liabilities. In addition, the Company has identified certain short-term leases embedded within its manufacturing contracts which are not recorded on the Company’s balance sheet in accordance with the practical expedient elected.

The Company identified and assessed the following estimates in recognizing the right-of-use asset and corresponding liability:

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Expected lease term: The expected lease term for those leases commencing prior to January 1, 2019 did not change with the adoption of ASC 842. The expected lease term for leases commencing after the adoption of ASC 842 includes noncancelable lease periods and, when applicable, periods covered by an option to extend the lease if the Company is reasonably certain to exercise that option, as well as periods covered by an option to terminate the lease if the Company is reasonably certain not to exercise that option.

The following table summarizes the lease assets and liabilities as of September 30, 2019 (in thousands):

	As of September 30, 2019
Assets
Operating lease assets	$	30,619
Total lease assets		30,619
Liabilities
Current
Operating lease liabilities		4,805
Non-current
Operating lease liabilities, net of current portion		36,827
Total lease liabilities	$	41,632

The following table summarizes operating lease costs included in research and development and general and administrative expense, as well as sublease income for the three and nine months ended September 30, 2019 (in thousands):

	Three Months Ended September 30, 2019		Nine Months Ended September 30, 2019
Operating lease costs	$	2,131	$	5,857
Short-term lease costs		1,117		3,378
Variable lease costs		698		2,111
Sublease income		—		(525	)
Net lease cost	$	3,946	$	10,821

The following table summarizes the maturity of undiscounted payments due under lease liabilities and the present value of those liabilities as of September 30, 2019 (in thousands):

	Total
2019	$	1,997
2020		9,334
2021		8,816
2022		7,345
2023		7,363
Thereafter		23,254
Total	$	58,109
Present value adjustment		(16,477	)
Present value of lease liabilities	$	41,632

The following table summarizes the lease term and discount rate as of September 30, 2019:

	As of September 30, 2019
Weighted-average remaining lease term (years)
Operating leases		6.8
Weighted-average discount rate
Operating leases		9.9	%

The following table summarizes the cash paid for amounts included in the measurement of lease liabilities for the nine months ended September 30, 2019 (in thousands):

	Nine Months Ended September 30,
	2019
Cash paid for amounts included in the measurement of lease liabilities	$	6,362
Operating cash flows from operating leases	$	6,362