The Company recorded rent expense of approximately $2.5 million for the year ended December 31, 2018. The Company recorded a rent credit of approximately $0.2 million for the year ended December 31, 2017 due to the accelerated amortization the deferred rent associated with the 200 Sidney Street facility. In July 2017, the Company agreed to terminate its lease and revised its estimate of the remaining amortization period from 63 months to seven months.

In July 2017, the Company entered into an agreement to lease approximately 41,346 square feet of laboratory and office space at 301 Binney Street in Cambridge, Massachusetts. Annual rent is approximately $3.1 million. The ten-year lease commenced in January 2018 and contains provisions for a free-rent period, annual rent increases and an allowance for tenant improvements. The Company is responsible for real estate taxes, maintenance, and other operating expenses applicable to the leased premises. In addition to approximately $1.6 million the Company has committed to for tenant improvements, the operating lease also provided for a tenant improvement allowance, at the cost of the lessor, not to exceed approximately $6.6 million. The Company was deemed to be the accounting owner of the tenant improvements primarily because it was responsible for project cost overruns. Therefore, the amounts will be recorded as a leasehold improvement and deferred rent and will be recorded as a reduction to rent expense ratably over the lease term. At December 31, 2018, the Company has capitalized approximately $5.0 million of the landlord-funded tenant improvements, representing the completed portion of the buildout. In conjunction with the lease, the Company established a letter of credit of approximately $1.0 million secured by cash balances included in restricted cash.

In July 2015, the Company entered into an operating lease for office and laboratory space at 200 Sidney Street in Cambridge, Massachusetts. The operating lease term commenced in February 2016 and expired in April 2021 with a one year renewal option to extend the lease. The Company agreed to terminate the lease in July 2017 at a date that was 30 days after the commencement of its new lease. No penalties were associated with the termination of the lease. Rent expense commenced on February 1, 2016 and was recognized on a straight‑line basis over the duration of the term. The operating lease provided for annual rent of approximately $0.9 million, payable on a monthly basis, which increased at a rate of 3% annually, and included three months of rent abatement during the first year. The Company was responsible for real estate taxes, maintenance, and other operating expenses applicable to the leased premises. The Company was deemed to be the accounting owner of the tenant improvements primarily because it was responsible for project cost overruns. Therefore, the amounts were recorded as a leasehold improvement and deferred rent and were being recorded as a reduction to rent expense ratably over the lease term of 63 months. As a result of the agreement to terminate its lease, the Company revised its estimate of the remaining amortization period of the deferred rent and its estimate of the remaining useful life of its leasehold improvements to seven months through January 2018.

In June 2017, the Company entered two non-cancellable thirty-six month lease agreements for certain lab equipment of approximately $0.2 million and $0.7 million, respectively. The lease term and payments for each agreement began upon delivery and installation of the equipment. Both leases are accounted for as a capital lease as one has a bargain purchase option and in the other, the present value of the lease exceeds 90% of the fair market value. At December 31, 2018, the interest rate on each capital lease obligation was approximately 1.1% and 7.3%, respectively.

In October 2016, the Company entered into a twenty-four month, non-cancellable lease agreement for approximately $0.4 million for certain lab equipment. Due to the existence of a bargain purchase option, the lease has been accounted for as a capital lease. At December 31, 2017, the interest rate on the outstanding capital lease obligation was approximately 9.6%. The agreement terminated per the terms of the lease agreement in November 2018.

Future minimum lease payments under the Company’s non-cancelable operating and capital leases as of December 31, 2018, are as follows (in thousands):

	Operating		Capital
	leases		leases
Fiscal year:
2019	$	3,175	$	287
2020		3,270		214
2021		3,369		2
2022		3,470		—
2023		3,574		—
Thereafter		18,067		—
Total future minimum lease payments	$	34,925	$	503
Less amounts representing interest				27
Capital lease obligations at December 31, 2018				476
Less current portion of capital lease obligations				266
Capital lease obligations, net of current portion			$	210