Commitments and Contingencies Operating Leases We lease laboratory and office space under an operating lease in Seattle, Washington. In January 2016, we entered into a new lease agreement for approximately 20,133 square feet of office and laboratory space, which includes and expands on the space we previously subleased. The lease commenced on January 1, 2017 with a term of five years and an option to extend the term for an additional three years. The annual base rent is $1.1 million for the first year and increases by 2.5% each year thereafter. Under the terms of this lease agreement, we provided a $200,000 security deposit in January 2017 under a standby letter of credit. In May 2017 , we entered into a sublease agreement with a third party subtenant. As sublandlord under this agreement, we are subleasing 5,048 square feet of the Seattle laboratory and office space for a period of three years. The annual base rent payable under this sublease is $273,000 for the first year and will increase by 2.5% each year thereafter. Rent under this sublease agreement is reflected in other income. We also lease 9,640 square feet of office space under an operating lease in South San Francisco, California. The lease commenced in January 2015 and continues through January 2020, with an option to extend for an additional five years . Under this lease, we were required to provide a $121,000 letter of credit as a security deposit. As of September 30, 2018 , no funds had been drawn on the letter of credit. Contingencies In June 2015, we entered into a clinical supply agreement with NanoPass Technologies LTD (NanoPass) for the use of its intradermal delivery device in certain of our clinical trials. In July 2015, in connection with the execution of the agreement, we paid an upfront fee of $600,000 for access and rights to use this device. In December 2015, we initiated a Phase 2 clinical trial using the device which triggered a milestone payment of $500,000 . Both the upfront fee and milestone payments were capitalized to prepaid expenses, and fully amortized to research and development expense as of December 31, 2017. In October 2016, we entered into a letter agreement with NanoPass, which amended our clinical supply agreement to expand the field of use to include all oncology immunotherapy applications, which provided for additional milestone payments to NanoPass upon achievement of future clinical milestones. Per the terms of the letter agreement, we paid NanoPass an additional upfront, one-time, non-refundable payment of $150,000 . In addition, we agreed to pay certain future milestone fees up to an aggregate of $8.8 million upon the achievement of certain clinical milestones. However, we did not use the NanoPass intradermal delivery device in our SYNOVATE study, a Phase 3 clinical trial studying CMB305 in patients with synovial sarcoma. We announced the discontinuation of our SYNOVATE study in October 2018 and do not expect to incur any additional milestone fees in connection with the CMB305 program. Under our license agreements with the Infectious Disease Research Institute (IDRI), we are contingently obligated to pay potential future milestone payments, which could total up to $1.8 million and $1.3 million , respectively, for the first and each subsequent exclusive licensed product we develop, and $1.3 million and $625,000 , respectively, for the first and each subsequent non-exclusive licensed product we develop. We are contingently obligated to pay potential future milestone payments to third parties as part of certain collaboration and licensing agreements, which could total up to $6.5 million in aggregate payments for the ZVex products we develop. We also have potential future royalty payments we may be required to make under our licensing agreements as described in Note 9.