In December 2015, the Company entered into a lease agreement, or the Stamford Lease, for office space in Stamford, Connecticut, or the Premises, for the purposes of relocating its headquarters. The initial term of the Stamford Lease commenced in May 2016, or the Commencement Date, and ends in November 2023 and is renewable for one five-year term.

The Stamford Lease requires monthly lease payments, including rent escalations and rent holidays, during the initial lease term. The Company began to make rental payments from the Commencement Date. Prior to January 1, 2019, the Company recorded monthly rent expense on a straight-line basis from March 2016, upon taking possession of the Premises, through December 31, 2018. As of December 31, 2018, the balance of deferred lease obligation, representing the difference between cash rent paid and straight-line rent expense, was $864.

As of the Commencement Date, the Stamford Lease landlord had made tenant improvements of $1,094 to the leased premises. Such amount was included in Property and equipment, net and in Deferred lease obligation as of December 31, 2018. The portion of Deferred lease obligation that is related to tenant improvements was being amortized as a reduction to rent expense over the same term as rent expense. As of December 31, 2018, the balance of Deferred lease obligation related to tenant improvements was $698.

Total rent expense under the Stamford Lease was $246 and $491 for the three and six months ended June 30, 2018, respectively.

In connection with the signing of the Stamford Lease, the Company entered into a standby letter of credit agreement for $769, which serves as a security deposit for the Premises. The standby letter of credit is automatically renewed annually through November 2023. This standby letter of credit is secured with restricted cash in a money market account (refer to Note 6, Restricted Cash).

On January 1, 2019, the Company adopted ASC 842 (see Note 2 – Basis of Presentation: Accounting Pronouncements Recently Adopted). Under ASC 842, since the Company adopted the practical expedients not to re-evaluate whether a contract is or contains a lease and to maintain the lease classification under ASC 840, the Stamford Lease continues to be accounted for as an operating lease.

Upon adoption of ASC 842, the Company was required to establish an operating lease ROU asset and operating lease liability for the Stamford Lease. In establishing the ROU asset, the operating lease liability of $5,198 was reduced by lease incentives relating to tenant improvements of $698 and deferred lease obligation of $864, which were outstanding on December 31, 2018.

Under ASC 842, lease expense is recognized on a straight-line basis over the lease term. As a result, $234 of operating lease cost, or lease expense, was recognized for the three months ended June 30, 2019, consisting of $164 relating to R&D lease expense and $70 relating to G&A lease expense. For the six months ended June 30, 2019, $469 of operating lease cost was recognized, consisting of $328 relating to R&D lease expense and $141 relating to G&A lease expense.

	Three Months Ended			Six Months Ended
	June 30, 2019			June 30, 2019
Cash paid for amounts included in the measurement of lease liability:
Operating cash outflows relating to operating lease	$	(302	)	$	(603	)
ROU assets obtained in exchange for new operating lease liabilities	$	—		$	3,636
Remaining lease term-operating lease (years)	4.4			4.4
Discount rate - operating lease		7.0	%		7.0	%

Future minimum lease payments under non-cancellable operating leases, as well as a reconciliation of these undiscounted cash flows to the operating lease liability as of June 30, 2019, were as follows:

Year Ending December 31,
2019 (Excluding the six months ended June 30, 2019)	$	613
2020		1,239
2021		1,264
2022		1,288
2023		1,164
Total future minimum lease payments, undiscounted		5,568
Less imputed interest		(796	)
Total	$	4,772

Operating lease liability reported as of June 30, 2019:
Operating lease liability - current	$	923
Operating lease liability - non-current		3,849
Total	$	4,772