Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued compensation	$ 798,243	$ 788,570
Accrued research and development	3,097,752	1,327,103
Accrued general & administrative	263,076	120,792
Accrued expenses	$ 4,159,071	$ 2,236,465

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_AccruedLiabilitiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant