Subsequent Event	3 Months Ended
Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Event	13. Subsequent Event In April 2019, the Company amended its multi-year lease agreement to relocate its office space in Boston, Massachusetts under an operating lease agreement. The amended lease term is for a period of seven years from the date of relocation. The initial annual base rent of the relocation premises is $0.6 million per year, increasing 2% annually. In connection with the lease amendment, the Company issued a new letter of credit for the benefit of the landlord in the amount of $0.2 million. In May 2019, the Company was awarded a 5-year grant for up to $1.5 million from the National Institutes of Health.

The entire disclosure for significant events or transactions that occurred after the balance sheet date through the date the financial statements were issued or the date the financial statements were available to be issued. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, catastrophic loss, significant foreign exchange rate changes, loans to insiders or affiliates, and transactions not in the ordinary course of business.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 855
-URI http://asc.fasb.org/topic&trid=2122774

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