E. Commitments and Contingencies Leases Effective July 27, 2007, the Company entered into a lease agreement with Intercontinental Fund III for the rental of approximately 89,000 square feet of laboratory and office space at 830 Winter Street, Waltham, MA. The Company uses this space for its corporate headquarters, research and other operations. The initial term of the lease is for twelve years with an option for the Company to extend the lease for two additional terms of five years. The Company is required to pay certain operating expenses for the leased premises subject to escalation charges for certain expense increases over a base amount. The Company entered into a sublease in December 2009 for 14,100 square feet of this space in Waltham through January 2015, with the sublessee having an option to extend the term for an additional two years. At September 30, 2011, the Company also leases a facility in Norwood, MA under an agreement through 2018 with an option to extend the lease for an additional term of five years. The Company is required to pay certain operating expenses for the leased premises subject to escalation charges for certain expense increases over a base amount. The minimum rental commitments for both of the Company?s facilities, including real estate taxes and other expenses, for the next five fiscal years and thereafter under the non-cancelable operating lease agreements discussed above are as follows (in thousands): 2012 (nine months remaining) $ 4,419 2013 5,893 2014 5,981 2015 6,181 2016 6,203 Thereafter 22,413 Total minimum lease payments $ 51,090 Total minimum rental payments from sublease (2,092 ) Total minimum lease payments, net $ 48,998 Collaborative Agreements The Company is contractually obligated to make potential future success-based regulatory milestone payments in conjunction with certain collaborative agreements. These payments are contingent upon the occurrence of certain future events and, given the nature of these events, it is unclear when, if ever, the Company may be require