Commitments and Contingencies Operating Leases On April 9, 2013, we entered into an amendment (the 2013 Amendment) to the lease agreement dated September 14, 2010 (as amended, the Lease) relating to the lease of office and laboratory space at our corporate headquarters located in South San Francisco, California. The 2013 Amendment provided for an expansion of the premises covered under the Lease, effective April 1, 2014; an extension of the term of the Lease to April 30, 2020 with an option to renew for an additional five years; payment of base rent with rent escalation; and payment of certain operating expenses during the term of the Lease. The 2013 Amendment also provided for an allowance of approximately $0.7 million for tenant improvements, which, to the extent not used by March 31, 2015, will be used to offset base rent obligations, and an additional allowance of approximately $0.5 million for tenant improvements, which, if used, will be repaid in equal monthly payments with interest at a rate of 9% per annum over the remaining term of the Lease. On June 4, 2014, we entered into an additional amendment to the Lease (the June 2014 Amendment), which provided for an expansion of the premises covered under the Lease by approximately 13,000 square feet, effective October 1, 2014; payment of base rent with rent escalation; and payment of certain operating expenses during the term of the Lease. The June 2014 Amendment also provided for an allowance of approximately $0.2 million for tenant improvements, which, to the extent not used by March 31, 2015, will be used to offset base rent obligations, and an additional allowance of approximately $0.1 million for tenant improvements, which, if used, will be repaid in equal monthly payments with interest at a rate of 9% per annum over the remaining term of the Lease. The total future minimum lease payments for the additional space, which will be paid through April 2020, are approximately $2.5 million as of September 30, 2014 . On September 15, 2014, we entered into an addi