8. Commitments and Contingencies Operating Lease We lease office and laboratory space located at 3545 John Hopkins Court, La Jolla, California (the  Facility ) for our corporate headquarters and research facility under an operating lease agreement (the  Lease ). The Lease commenced in July 2010 and provided for approximately 22,000 square feet of office and laboratory space, expiring in June 2017. In November 2012, we amended the Lease to expand our laboratory and office space by approximately 7,000 square feet, including the addition of an approximately 3,000 square foot dedicated research and development laboratory. Lease payments for this additional space began October 2013. We have an option to terminate and cancel the lease in June 2015 upon six months  written notice to our landlord. We also have two options to extend the lease for successive three-year periods. In connection with the inception of the Lease, we were provided tenant incentives of $0.1 million which was used to construct a leasehold improvement. In addition, we were provided and fully utilized a tenant improvement allowance of approximately $0.6 million, which was used to fund additional leasehold improvements. In January 2011, the Lease was amended to memorialize the payback of the allowance into our base rent. In conjunction with the amendment of the Lease in November 2012, we were provided an additional tenant improvement allowance of approximately $0.7 million, which was utilized in 2013 to fund leasehold improvements in the newly occupied space. We are obligated to repay our landlord the tenant improvement allowance, plus interest at a fixed rate of 8%, on a monthly basis over the remaining term of the Lease. The future minimum payment summary below includes our amended base rents over the remaining period of the lease agreement. Cumulative rent to be paid over the lease term is being amortized on a straight-line basis over the term of the Lease. Rent expense for the years ended December 31, 2013, 2012 and 2011 was approximately $0.7 mil