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Summary of Significant Accounting Policies - Addtional Information (Detail) - USD ($)			1 Months Ended				12 Months Ended
	Mar. 12, 2019	Jan. 14, 2019	Mar. 31, 2019	Jan. 31, 2019	Jan. 18, 2019	Sep. 20, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Significant Accounting Policies [Line Items]
Other Intangible Assets, Net								$ 800,000
Other Finite-Lived Intangible Assets, Gross								2,500,000
Cash							$ 1,004,000	5,965,000	$ 9,375,000
Depreciation							265,000	251,000
Research and Development Costs Expenses							$ 4,600,000	$ 5,500,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount							15,286	28,102
Development Project Service Evaluation Exchange Cost							$ 50,000
Net Income (Loss) Attributable to Parent							(8,583,000)	$ (7,023,000)
Retained Earnings (Accumulated Deficit)							(47,740,000)	(39,157,000)
Proceeds from Issuance of Common Stock	$ 17,000,000						$ 1,180,000	3,567,000
Technology Service [Member]
Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Including Assessed Tax								$ 50,000
Warrant
Significant Accounting Policies [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount							183,714	63,889
Proceeds from Issuance of Common Stock						$ 1,200,000
Subsequent Event [Member]
Significant Accounting Policies [Line Items]
Proceeds from Issuance of Private Placement			$ 17,000,000	$ 1,500,000
Proceeds from Issuance of Common Stock	$ 17,000,000	$ 900,000		$ 900,000	$ 1,500,000
Furniture and fixtures
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life							7 years
Computers and equipment
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life							3 years
Scientific equipment
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life							7 years
Jp Morgan Chase Bank
Significant Accounting Policies [Line Items]
Cash, FDIC Insured Amount							$ 800,000	$ 5,700,000
Federal Deposit Insurance							$ 250,000
Cash								6,000,000
Md Anderson
Significant Accounting Policies [Line Items]
Amortization of Intangible Assets								$ 1,700,000