Commitments and Contingencies Lease Obligations In May 2018, the Company entered into an amendment to its operating lease for its former corporate headquarters in South San Francisco (the "Headquarters Lease Amendment") to relocate and expand its headquarters to 148,020 rentable square feet in a building in South San Francisco, California (the "New Premises"). The Headquarters Lease Amendment has a contractual term of ten years from the legal commencement date, which was April 1, 2019, when the building was ready for occupancy. For accounting purposes, the lease commencement date was determined to be August 1, 2018, which was the date at which the Company was deemed to have obtained control over the property. The Company has an option to extend the lease term for a period of ten years by giving the landlord written notice of the election to exercise the option at least nine months, but not more than twelve months, prior to the expiration of the Headquarters Lease Amendment lease term. The Company determined that this renewal was not reasonably certain at lease inception. The Headquarters Lease Amendment provides for monthly base rent amounts escalating over the term of the lease. In addition, the Headquarters Lease Amendment provided a tenant improvement allowance ("TIA") of up to $25.9 million, which was fully utilized, of which $4.4 million will be repaid to the landlord in the form of additional monthly rent. This is recorded as leasehold improvement assets and an offset to the lease ROU asset on the Condensed Consolidated Balance Sheets as of June 30, 2020 and December 31, 2019. The Company is also required to pay the operating expenses for the New Premises, such as taxes and insurance, which are treated as variable lease payments. Management exercised judgment in applying the requirements of ASC 842, including the determination as to whether certain contracts contain a lease and for the Headquarters Lease Amendment, the discount rate used to determine the measurement of the lease liability. As the implicit rate of the Headquarters Lease Amendment was not known, the Company estimated a 9.0% discount rate, which was managements estimate of the Companys incremental borrowing rate. To estimate the incremental borrowing rate, management considered observable debt yields of comparable market instruments, as well as benchmarks within the Headquarters Lease Amendment that may be indicative of the rate implicit in the lease. Total operating lease costs, including variable and short-term lease costs, were $2.9 million and $5.5 million for the three and six months ended June 30, 2020, respectively, and $2.5 million and $4.8 million for the three and six months ended June 30, 2019, respectively. Operating lease liabilities are calculated as the net present value of the remaining lease payments over the remaining lease term. In determining the present value of lease payments, the Company uses its incremental borrowing rate based on the information available at the lease commencement date. As of June 30, 2020, the weighted average remaining lease term was 8.8 years and the weighted average discount rate used to determine the operating lease liability was 9.0%. Cash paid for amounts included in the measurement of lease liabilities for the six months ended June 30, 2020 and June 30, 2019 of $4.7 million and $1.9 million, respectively, was included in net cash used in operating activities in the Company's Condensed Consolidated Statements of Cash Flows. The following table reconciles the undiscounted cash flows for the next five years and total of the remaining years to the operating lease liabilities recorded in the Condensed Consolidated Balance Sheet as of June 30, 2020 (in thousands): Year Ended December 31: 2020 (six months) $ 5,071 2021 10,391 2022 10,731 2023 11,083 2024 11,447 Thereafter 54,074 Total undiscounted lease payments 102,797 Present value adjustment (31,855) Net operating lease liabilities $ 70,942 In October 2018, the Company entered into a sublease agreement ("Sublease Agreement") to sublease approximately 36,835 rentable square feet of space in its New Premises. The Sublease Agreement has a term of five years from the commencement date of April 12, 2019 and provides for the Company to receive monthly base rent amounts escalating over the term of the lease. The Company also passes through a portion of the operating expenses, such as taxes and insurance for the New Premises to the sublessee, which are treated as variable sublease income. Total sublease income, including rent and variable sublease cost reimbursements, was $1.0 million and $1.9 million for the three and six months ended June 30, 2020, respectively, and $0.8 million for the three and six months ended June 30, 2019, respectively. The following table details the future undiscounted cash inflows relating to the Sublease Agreement as of June 30, 2020 (in thousands): Year Ended December 31: 2020 (six months) $ 1,431 2021 2,925 2022 3,009 2023 3,096 2024 876 Thereafter  Total undiscounted sublease receipts $ 11,337 Indemnification In the ordinary course of business, the Company may provide indemnifications of varying scope and terms to vendors, lessors, business partners, board members, officers, and other parties with respect to certain matters, including, but not limited to, losses arising out of breach of such agreements, services to be provided by the Company, negligence or willful misconduct of the Company, violations of law by the Company, or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with directors and certain officers and employees that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors, officers or employees. No demands have been made upon the Company to provide indemnification under such agreements, and thus, there are no claims that the Company is aware of that could have a material effect on the Companys Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Operations and Comprehensive Loss, or Condensed Consolidated Statements of Cash Flows. Commitments Effective September 2017, the Company entered into a Development and Manufacturing Services Agreement as amended (DMSA) with Lonza Sales AG (Lonza) for the development and manufacture of biologic products. Under the DMSA, the Company will execute purchase orders based on project plans authorizing Lonza to provide development and manufacturing services with respect to certain of the Company's antibody and enzyme products, and will pay for the services provided and batches delivered in accordance with the DMSA and project plan. Unless earlier terminated, the DMSA will expire on September 6, 2022. As of June 30, 2020 and December 31, 2019, the Company had open non-cancellable purchase orders for biological product development and manufacturing costs totaling $18.0 million and $21.2 million, respectively. The activities under these purchase orders are expected to be completed by May 2027. As of June 30, 2020 and December 31, 2019, the Company had total non-cancellable purchase commitments under the DMSA of $12.1 million and $11.2 million, respectively. During the three months ended June 30, 2020 and 2019, the Company incurred costs of $3.8 million and $3.1 million, respectively, and made payments of $2.0 million and $3.9 million, respectively, for the development and manufacturing services rendered under the DMSA. During the six months ended June 30, 2020 and 2019, the Company incurred costs of $4.8 million and $6.7 million, respectively, and made payments of $5.2 million and $6.5 million, respectively, for the development and manufacturing services rendered under the DMSA.