10. Commitments and Contingencies Lease Obligation Until December 2010, we leased our Phase I Laboratory, the first completed building in our Silver Spring facility, pursuant to a synthetic lease arrangement entered into in June 2004 with Wachovia Development Corporation and its affiliates (Wachovia), now an affiliate of Wells Fargo. Under the lease, Wachovia funded $32.0 million toward the construction of the Phase I Laboratory on land that we own. After completing construction in May 2006, Wachovia leased the Phase I Laboratory to us. The base term of the lease was scheduled to end in May 2011, at which time we had planned to exercise our option to purchase the Phase I Laboratory for approximately $32.0 million. However, in order to secure the Credit Agreement, we terminated the Lease and acquired title to the Phase I Laboratory for $32.0 million in December 2010. Upon termination of the lease, $35.1 million of cash and marketable investments held as collateral under the lease was released. Operating Leases We lease primarily facilities space and office equipment under operating lease arrangements that have terms expiring at various dates through 2018. Certain lease arrangements include renewal options and escalation clauses. In addition, various lease agreements to which we are a party require that we comply with certain customary covenants throughout the term of these leases. If we are unable to comply with these covenants and cannot reach a satisfactory resolution in the event of a noncompliance, these agreements could terminate. Minimum rent commitments under non-cancelable operating leases are as follows (in thousands): Years ending December 31, 2011 $ 4,364 2012 2,626 2013 2,419 2014 1,700 2015 1,868 Thereafter 4,819 $ 17,796 Total rent expense was $2.7 million, $2.7 million and $2.5 million for the years ended December 31, 2010, 2009 and 2008, respectively. Milestone and Royalty Payments We are party to certain license agreements as described in Note 15? License Agreements to these consolidated financial