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. In December 2013, the Company modified its lease agreement at 830 Winter Street, Waltham, MA to include approximately 19,000 square feet of additional office space through 2020, concurrent with the remainder of the original lease term. As part of the lease amendment, the Company will receive a construction allowance of approximately $746,000 to build out office space to the Company’s specifications. The Company obtained physical control of the additional space to begin construction in January 2014. 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 a conditional option to extend the term for an additional two years. However, the Company has notified the sublessee that it does not intend to allow them to extend the term beyond January 2015.

Effective April 2012, the Company entered into a sublease agreement for the rental of 7,310 square feet of laboratory and office space at 830 Winter Street, Waltham, MA from Histogenics Corporation. The initial term of the sublease is for three years with a conditional option for the Company to extend the lease through October 2017. 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.

Effective March 2013, the Company entered into a lease agreement for the rental of 43,850 square feet in Norwood, MA 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.

Effective April 2013, the Company entered into a lease agreement with River Ridge Limited Partnership for the rental of 7,507 square feet of additional office space at 100 River Ridge Drive, Norwood, MA. The initial term of the lease is for five years and two months commencing in August 2013 with an option for the Company 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.

As of December 31, 2013, the minimum rental commitments for 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):

2014 (six months remaining)	$	3,364
2015	7,677
2016	7,543
2017	7,626
2018	7,843
Thereafter	11,895
Total minimum lease payments	$	45,948
Total minimum rental payments from sublease	(745		)
Total minimum lease payments, net	$	45,203

Purchase Obligations

At December 31, 2013, the Company is obligated to a vendor for certain contractual services to be performed in fiscal 2014. Pursuant to the contract, the Company is required to make a $1.2 million payment to the vendor unless the contract is terminated by the Company for cause.

Collaborations

The Company is contractually obligated to make potential future success-based regulatory milestone payments in conjunction with a certain collaborative agreement. 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 required to pay such amounts. Further, the timing of any future payment is not reasonably estimable. As of December 31, 2013, the maximum amount that may be payable in the future under the Company’s current collaborative agreement is $2.0 million, $1.4 million of which is reimbursable by a third party under a separate agreement.