6.	Restricted Cash:

The Company is required to maintain a stand-by letter of credit as a security deposit under the ARE-East River Science Park LLC (“ARE”) lease (see Note 15) through the end of the lease term in December 2021, plus three months. The fair value of the letter of credit approximates its contract value. The Company’s bank requires the Company to maintain a restricted cash balance to serve as collateral for the letter of credit issued to the landlord by the bank. As of December 31, 2018 and 2017, the restricted cash balance for the ARE lease was invested in a commercial money market account.

The Company had $123,376 of restricted cash included in long-term assets as of December 31, 2018 and 2017 and is measured using level 1 inputs.