INTELLECTUAL PROPERTY LICENSE	12 Months Ended
Dec. 31, 2017
INTELLECTUAL PROPERTY LICENSE
INTELLECTUAL PROPERTY LICENSE	15. INTELLECTUAL PROPERTY LICENSE In July 2007, the Company entered into a worldwide exclusive license (the “BCH License”) for patents co-owned by Boston Children’s Hospital (“BCH”) and the Massachusetts Institute of Technology initially covering the use of biopolymers to treat spinal cord injuries, and to promote the survival and proliferation of human stem cells in the spinal cord. During 2011, the BCH License was amended, and the Company obtained additional rights for use in the field of peripheral nerve injuries. The BCH License, as amended, has a 15‑year term, or as long as the life of the last expiring patent right thereunder, whichever is longer, unless terminated earlier by the licensor, under certain conditions as defined in the related license agreement. In connection with the BCH License, the Company paid an initial $75 licensing fee and is required to pay certain annual maintenance fees, milestone payments and royalties. License fees are capitalized and the gross total at December 31, 2017 and 2016 was $200 (see Note 5). The Company accounts for milestone payments, maintenance fees and royalties when they become due and payable. For the year ended December 31, 2017, the Company expensed milestone payments of $175.

15. INTELLECTUAL PROPERTY LICENSE

In July 2007, the Company entered into a worldwide exclusive license (the “BCH License”) for patents co-owned by Boston Children’s Hospital (“BCH”) and the Massachusetts Institute of Technology initially covering the use of biopolymers to treat spinal cord injuries, and to promote the survival and proliferation of human stem cells in the spinal cord. During 2011, the BCH License was amended, and the Company obtained additional rights for use in the field of peripheral nerve injuries. The BCH License, as amended, has a 15‑year term, or as long as the life of the last expiring patent right thereunder, whichever is longer, unless terminated earlier by the licensor, under certain conditions as defined in the related license agreement. In connection with the BCH License, the Company paid an initial $75 licensing fee and is required to pay certain annual maintenance fees, milestone payments and royalties. License fees are capitalized and the gross total at December 31, 2017 and 2016 was $200 (see Note 5). The Company accounts for milestone payments, maintenance fees and royalties when they become due and payable. For the year ended December 31, 2017, the Company expensed milestone payments of $175.