6. Restricted Cash

At September 30, 2018, the Company had $0.9 million in restricted cash of which $0.6 million was classified as short-term and $0.3 million as long-term. At December 31, 2017, the Company had $0.5 million in restricted cash, of which $0.2 million was classified as short-term and $0.3 million as long-term.

As of December 31, 2017, the $0.5 million of restricted cash served as the security deposit on the lease of the Company’s current facility in Cambridge, Massachusetts (Note 8). In April 2018, the Company collected a $0.2 million refund from its landlord in accordance with the terms of the lease agreement and the remaining of $0.3 million is classified as long-term on the Company’s condensed consolidated balance sheets as of September 30, 2018.

In August 2018, the Company entered into a manufacturing agreement with a third party for manufacturing services related to one of its product candidates. In accordance with the terms of the manufacturing agreement, the Company was required to provide a letter of credit in the amount of $0.6 million. The letter of credit will expire on September 30, 2019 and is classified as short-term on the Company’s condensed consolidated balance sheets as of September 30, 2018.

In accordance with the recently adopted accounting pronouncement ASU 2016-18, the following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the amounts shown in the condensed consolidated statement of cash flows as of September 30, 2018, December 31, 2017, September 30, 2017 and December 31, 2016 (in thousands):