6. Commitments and Contingencies Lease Commitments The Company's operating lease obligations primarily consist of leased office, laboratory, and manufacturing space under a non-cancelable operating lease that originally were to expire in November 2019. In addition to the minimum future lease commitments presented below, the lease requires the Company to pay property taxes, insurance, maintenance, and repair costs. The lease includes a rent holiday concession and escalation clauses for increased rent over the lease term. Rent expense is recognized using the straight-line method over the term of the lease. The Company records deferred rent calculated as the difference between rent expense and the cash rental payments. On October 19, 2017, the Company entered into an agreement to sublease one of its facilities. The sublease agreement commenced on approximately December 1, 2017 and expired on November 15, 2019 (which was 15 days prior to the expiration of the facility lease). The sublessee paid a base rent of $82,410 per month. In addition to the base rent, the sublessee paid the Landlord's operating expenses and property taxes due and payable with respect to the subleased facility. Upon the adoption of Topic 842 on January 1, 2019, the Company recognized a right of use asset and a corresponding leasehold liability related to this lease of approximately $1.8 million, representing the present value of the remaining minimum lease payments as of that date. The asset was being reduced over the remaining period of the lease on a straight-line basis. The leasehold liability is being reduced as payments are made. On April 1, 2019, we entered into an amendment to the lease which extended the lease term for an additional period of five years subsequent to the original expiration of November 30, 2019. As amended, the lease will expire on November 30, 2024. Under the terms of the amendment, we are obligated to pay approximately $5.8 million in base rent payments through November 2024, beginning on December 1, 2019. This amendment did not extend the term of the lease with respect to the building being subleased. In connection with the amendment the Company adjusted its right-of-use asset and lease liability to $6.0 million. As of the date of the amendment, the operating lease was included on the balance sheet at the present value of the future base payments discounted at a 6.5% discount rate using the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term and amount equal to the lease payments in a similar economic environment as the lease do provide an implicit rate. For the three months ended September 30, 2020, our operating lease expense, excluding variable maintenance fees and other expenses paid by the Company on a monthly basis, was approximately $105,000, which totaled approximately $314,000 for each of the three month periods ended September 30, 2020 and 2019. Rent expense for the nine months ended September 30, 2020 and 2019 was approximately $942,000 and $1.1 million, respectively. Operating right-of-use asset amortization for the three months ended September 30, 2020 and 2019 was approximately $242,000 and $225,000, respectively. Operating right-of-use asset amortization for the nine months ended September 30, 2020 and 2019 was approximately $718,000 and $444,000, respectively. Due to payments being made in excess of operating lease expense recognized, the Company recorded approximately $331,000 as prepaid rent included in other assets on the condensed balance sheet as of September 30, 2020. The following table presents the future operating lease payments and lease liability included on the condensed balance sheet related to the Company's operating lease as of September 30, 2020 ( in thousands): Year Ending December 31, 2020 (remaining three months of the year) $ 274 2021 1,123 2022 1,162 2023 1,203 2024 1,138 4,900 Less: Imputed interest (630 ) Leasehold liability as of September 30, 2020 $ 4,270 Purchase Obligations Purchase obligations consist of agreements to purchase goods and services entered into in the ordinary course of business. The Company had non-cancelable commitments to suppliers for purchases totaling approximately $1.1 million as of September 30, 2020. Indemnification In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and may provide for indemnification of the counterparty. The Company's exposure under these agreements is unknown because it involves claims that may be made against it in the future but have not yet been made. To date, the Company has not been subject to any claims or been required to defend any action related to its indemnification obligations. The Company indemnifies each of its directors and officers for certain events or occurrences, subject to certain limits, while the director is or was serving at the Company's request in such capacity, as permitted under Delaware law and in accordance with its certificate of incorporation and bylaws. The term of the indemnification period lasts as long as a director may be subject to any proceeding arising out of acts or omissions of such director in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company currently holds director liability insurance. This insurance allows the transfer of risk associated with the Company's exposure and may enable it to recover a portion of any future amounts paid. The Company believes that the fair value of these indemnification obligations is minimal. Accordingly, it has not recognized any liabilities relating to these obligations for any period presented.