7. Commitments Leases As described further in Note 2, Summary of Significant Accounting Policies, the Company adopted Topic 842 as of January 1, 2019. Prior period amounts have not been adjusted and continue to be reported in accordance with the Companys historic accounting under Topic 840. In December 2010, the Company entered into a non-cancellable operating lease for office space and laboratory facilities in Yonkers, New York expiring in December 2025. In December 2011, the Company entered into an amendment which extended the terms of the lease through December 2027 (the Third Floor Lease). The lease provides for the option to renew for two additional five-year terms. The premises were occupied in June 2011. Monthly rent payments began the date the office and laboratory facilities were ready for occupancy. In January 2012, the Company entered into a non-cancellable operating lease for additional office space and laboratory facilities in the same building in Yonkers, New York expiring in December 2027 (the Fourth Floor Lease). The Fourth Floor Lease provides for an option to renew for two additional five-year terms. Effective August 1, 2017, the Company relinquished 10,912 square feet of space under the Fourth Floor Lease and was relieved of its obligations related to such space. The Company performed an evaluation of its other contracts in accordance with Topic 842 and is determined that, except for the leases described above, none of its contracts contain a lease. The balance sheet classification of the Companys lease liabilities was as follows: Description June 30, 2019 December 31, 2018 Operating lease liabilities: Current portion of lease liabilities $ 625,541 $  Long-term portion of lease liabilities $ 3,399,926 $  Operating lease liabilities are based on the net present value of the remaining lease payments over the remaining lease term. The leases are renewable at the end of the lease term at the Companys option. For the purposes of determining the remaining lease term in contemplation of available extensions, the Company did not consider either renewal to be probable at this time. In determining the present value of lease payments, the Company estimated its incremental borrowing rate based on the information available at the adoption date of Topic 842. As of January 1, 2019, the remaining lease term was 9.0 years and the discount rate used to determine the operating lease liability was 9.93%. As of June 30, 2019, the maturities of the Companys operating lease liabilities were as follows: Amount July 1, 2019-December 31, 2019 $ 326,662 Year ending December 31: 2020 666,391 2021 679,719 2022 693,313 2023 707,179 Thereafter 2,973,011 Total lease payments 6,046,275 Less: Present value adjustment (2,020,808 ) Operating lease liabilities $ 4,025,467 Cash paid for amounts included in the measurement of lease liabilities for the three and six months ended June 30, 2019 was $159,573 and $318,711, respectively, and was included in net cash used in operating activities in the Consolidated Statements of Cash Flows. Rent expense is recognized using the straight-line method over the term of each lease. Rent expense for each of the three months ended June 30, 2019 and 2018, was approximately $154,000, and for each of the six months ended June 30, 2019 and 2018 was $307,000 and $308,000, respectively.